Patent Publication Number: US-2021167199-A1

Title: Group iii-nitride high-electron mobility transistors with gate connected buried p-type layers and process for making the same

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a continuation in part of U.S. patent application Ser. No. 17/123,727, filed Dec. 16, 2020, which is incorporated herein by reference in its entirety; which application is a continuation of U.S. patent application Ser. No. 16/376,596, filed Apr. 5, 2019, which is incorporated herein by reference in its entirety; which application is a continuation in part of U.S. patent application Ser. No. 16/260,095, filed Jan. 28, 2019, now U.S. Pat. No. 10,840,334 that issued on Nov. 17, 2020, which is incorporated herein by reference in its entirety; which application is a continuation in part of U.S. patent application Ser. No. 15/424,209, filed Feb. 3, 2017, now U.S. Pat. No. 10,192,980 that issued on Jan. 29, 2019, which is incorporated herein by reference in its entirety; which application is a continuation in part of U.S. patent application Ser. No. 15/192,545, filed Jun. 24, 2016, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The disclosure relates to microelectronic devices and more particularly to gallium nitride high-electron mobility transistors with buried p-type layers. The disclosure also relates to a process of making microelectronic devices and more particularly to a process of making gallium nitride high-electron mobility transistors with buried p-type layers. 
     BACKGROUND OF THE DISCLOSURE 
     Group III-Nitride based or gallium nitride (GaN) based high-electron mobility transistors (HEMTs) are very promising candidates for high power radiofrequency (RF) applications, both in discrete and MMIC (Monolithic Microwave Integrated Circuit) forms. Current GaN HEMT designs use buffer layers that include traps to achieve desired breakdown. However, these traps cause memory effects that adversely affect performance. In particular, these designs show some trapping associated with what is called a “gate lag effect.” The gate lag effect may be particularly prevalent at high negative gate voltages. 
     Accordingly, there is a need for a solution to addressing gate lag effect and/or other negative performance issues in Group-III nitride HEMTs and improving the performance of such devices. 
     SUMMARY OF THE DISCLOSURE 
     One general aspect includes an apparatus that includes a substrate; a group III-Nitride buffer layer on the substrate; a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; a source electrically coupled to the group III-Nitride barrier layer; a gate electrically coupled to the group III-Nitride barrier layer; a drain electrically coupled to the group III-Nitride barrier layer; and a p-region being arranged at least in the substrate, where the p-region extends toward a source side of the substrate; and where the p-region extends toward a drain side of the substrate. 
     One general aspect includes a method of making a device that includes providing a substrate; providing a group III-Nitride buffer layer on the substrate; providing a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; electrically coupling a source to the group III-Nitride barrier layer; electrically coupling a gate to the group III-Nitride barrier layer; electrically coupling a drain to the group III-Nitride barrier layer; and providing a p-region being arranged at least in the substrate, where the p-region extends toward a source side of the substrate; and where the p-region extends toward a drain side of the substrate. 
     One general aspect includes an apparatus that includes a substrate; a group III-Nitride buffer layer on the substrate; a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; a source electrically coupled to the group III-Nitride barrier layer; a gate electrically coupled to the group III-Nitride barrier layer; a drain electrically coupled to the group III-Nitride barrier layer; and a p-region being arranged at least in the substrate, where a part of a source side of the substrate is free of the p-region; and where a part of a drain side of the substrate is free of the p-region. 
     One general aspect includes a method of making a device that includes providing a substrate; providing a group III-Nitride buffer layer on the substrate; providing a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; electrically coupling a source to the group III-Nitride barrier layer; electrically coupling a gate to the group III-Nitride barrier layer; electrically coupling a drain to the group III-Nitride barrier layer; and providing a p-region being arranged at least in the substrate, where a part of a source side of the substrate is free of the p-region; and where a part of a drain side of the substrate is free of the p-region. 
     One general aspect includes an apparatus, that includes a substrate; a group III-Nitride buffer layer on the substrate; a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer may include a higher bandgap than a bandgap of the group III-Nitride buffer layer; a source on the group III-Nitride barrier layer; a drain on the group III-Nitride barrier layer; a gate on the group III-Nitride barrier layer between the source and the drain; a p-region being arranged at least in the substrate; and where a part of a source side of the substrate is free of the p-region; and where a part of a drain side of the substrate is free of the p-region. 
     Additional features, advantages, and aspects of the disclosure may be set forth or apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the disclosure and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the disclosure, are incorporated in and constitute a part of this specification, illustrate aspects of the disclosure and together with the detailed description serve to explain the principles of the disclosure. No attempt is made to show structural details of the disclosure in more detail than may be necessary for a fundamental understanding of the disclosure and the various ways in which it may be practiced. In the drawings: 
         FIG. 1  shows a cross-sectional view of one aspect of a transistor according to the disclosure. 
         FIG. 2  shows a cross-sectional view of an aspect of a transistor according to the disclosure. 
         FIG. 3  illustrates a semiconductor device that may include a plurality of unit cell transistors in accordance with an aspect of the disclosure. 
         FIG. 4  is a schematic cross-sectional view taken along line IV-IV of  FIG. 3 . 
         FIG. 5  illustrates a top view of one aspect of a transistor according to the disclosure. 
         FIG. 6  illustrates a top view of one aspect of a transistor according to the disclosure. 
         FIG. 7  illustrates a top view of one aspect of a transistor according to the disclosure. 
         FIG. 8  shows a cross-sectional view of another aspect of a transistor according to the disclosure. 
         FIG. 9  shows a cross-sectional view of another aspect of a transistor according to the disclosure. 
         FIG. 10  shows a cross-sectional view of another aspect of a transistor according to the disclosure. 
         FIG. 11  shows a process for making a transistor according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The aspects of the disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting aspects and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one aspect may be employed with other aspects, as the skilled artisan would recognize, even if not explicitly stated herein. Descriptions of well-known components and processing techniques may be omitted so as to not unnecessarily obscure the aspects of the disclosure. The examples used herein are intended merely to facilitate an understanding of ways in which the disclosure may be practiced and to further enable those of skill in the art to practice the aspects of the disclosure. Accordingly, the examples and aspects herein should not be construed as limiting the scope of the disclosure, which is defined solely by the appended claims and applicable law. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings and in the different aspects disclosed. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the another element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the another element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the another element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. 
     The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     In addition to the type of structure, the characteristics of the semiconductor material from which a transistor is formed may also affect operating parameters. Of the characteristics that affect a transistor&#39;s operating parameters, the electron mobility, saturated electron drift velocity, electric breakdown field, and thermal conductivity may have an effect on a transistor&#39;s high frequency and high power characteristics. 
     Electron mobility is the measurement of how rapidly an electron is accelerated to its saturated velocity in the presence of an electric field. In the past, semiconductor materials, which had a high electron mobility, were preferred because more current could be developed with a lesser field, resulting in faster response times when a field is applied. Saturated electron drift velocity is the maximum velocity that an electron can obtain in the semiconductor material. Materials with higher saturated electron drift velocities are preferred for high frequency applications because the higher velocity translates to shorter times from source to drain. 
     Electric breakdown field is the field strength at which breakdown of the Schottky junction and the current through the gate of the device suddenly increases. A high electric breakdown field material is preferred for high power, high frequency transistors because larger electric fields generally can be supported by a given dimension of material. Larger electric fields allow for faster transients as the electrons can be accelerated more quickly by larger electric fields than by smaller ones. 
     Thermal conductivity is the ability of the semiconductor material to dissipate heat. In typical operations, all transistors generate heat. In turn, high power and high frequency transistors usually generate larger amounts of heat than small signal transistors. As the temperature of the semiconductor material increases, the junction leakage currents generally increase and the current through the field effect transistor generally decreases due to a decrease in carrier mobility with an increase in temperature. Therefore, if the heat is dissipated from the semiconductor, the material will remain at a lower temperature and be capable of carrying larger currents with lower leakage currents. 
     The disclosure includes both extrinsic and intrinsic semiconductors. Intrinsic semiconductors are undoped (pure). Extrinsic semiconductors are doped, meaning an agent has been introduced to change the electron and hole carrier concentration of the semiconductor at thermal equilibrium. Both p-type and n-type semiconductors are disclosed, with p-types having a larger hole concentration than electron concentration, and n-types having a larger electron concentration than hole concentration. 
     Silicon carbide (SiC) has excellent physical and electronic properties, which should theoretically allow production of electronic devices that can operate at higher temperatures, higher power, and higher frequency than devices produced from silicon (Si) or gallium arsenide (GaAs) substrates. The high electric breakdown field of about 4×E6 V/cm, high saturated electron drift velocity of about 2.0×E7 cm/sec and high thermal conductivity of about 4.9 W/cm-° K indicate that SiC would be suitable for high frequency and high power applications. In some aspects, the transistor of the disclosure comprises Si, GaAs or other suitable substrates. 
     GaN based HEMTs are very promising candidates for high power RF applications, both in discrete and MMIC forms. GaN HEMT designs may use buffer layers that include traps to achieve desired breakdown. However, these traps may cause memory effects that adversely affect performance. To overcome this limitation, structures with buried p layers may be utilized to enable obtaining breakdown with minimal trapping. These devices show reduction and/or elimination of drain lag effect and the part of trapping associated with that effect. However, they still show some trapping associated with what is called a “gate lag effect,” particularly at high negative gate voltages. 
     Our simulations have indicated that this effect is also arising from traps in the buffer layer. It is desirable to at least substantially eliminate this effect for many system applications. We propose here connecting a buried p layer to the gate or to a separate negative gate voltage in order to overcome this problem. 
     The methods proposed here enable GaN HEMT devices to be implemented without trapping effects or with reduced trapping effects. The proposed structure can be fabricated with currently available tools and techniques. The methods described here will allow significant improvements in the performance of both commercial and defense applications. They may also enable in the future devices for low noise applications. 
     Possible aspects may include: 
     1. An aspect where a gate is connected to the buried p-layer at one end or both ends of every gate finger. This connection may be achieved by etching down to the p-layer near these ends and making a metal contact to it. This metal may then be connected to the gate metal electrically. 
     2. Another aspect is to have a contact to the p-layer at the ends as above, but not connect it to the gate metal. Instead, a separate contact pad may be provided for this connection. A negative voltage may be applied to this terminal. The applied negative voltage may be more negative than the negative gate bias. 
     3. A third aspect may be similar to aspect  2  above and may further include an RF choke configuration to prevent flow of RF current through this terminal. 
       FIG. 1  shows a cross-sectional view of an aspect of a transistor according to the disclosure. 
     In particular,  FIG. 1  shows a cross-sectional view of a transistor  100 . The transistor  100  may include a substrate layer  102 . The substrate layer  102  may be made of Silicon Carbide (SiC). In some aspects, the substrate layer  102  may be a semi-insulating SiC substrate, a p-type substrate, an n-type substrate, and/or the like. In some aspects, the substrate layer  102  may be very lightly doped. In one aspect, the background impurity levels may be low. In one aspect, the background impurity levels may be 1E15/cm 3  or less. In one aspect, the substrate layer  102  may be formed of SiC selected from the group of 6H, 4H, 15R, 3C SiC, or the like. In one aspect, the substrate layer  102  may be formed of SiC that may be semi-insulating and doped with vanadium or any other suitable dopant or undoped of high purity with defects providing the semi-insulating properties. 
     In another aspect, the substrate layer  102  may be GaAs, GaN, or other material suitable for the applications described herein. In another aspect, the substrate layer  102  may include sapphire, spinel, ZnO, silicon, or any other material capable of supporting growth of Group III-nitride materials. In particular aspects, the substrate layer  102  may include a planer upper surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). In particular aspects, the substrate layer  102  may include a planer lower surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). Where upper and lower are defined along the Y axis. 
     The transistor  100  may include a buried p-region or p-type material layer  106  that may be formed within the substrate layer  102 . The p-type material layer  106  may be provided solely in the substrate layer  102 , extend from the substrate layer  102  to epitaxial layers within the transistor  100 , or located solely in the epitaxial layers of the transistor  100 . The dopants can be incorporated into the epitaxial layers by ion implantation alone, through epitaxial growth, or a combination of both. The p-type material layer  106  can span multiple layers and include multiple areas of different or graded p-doping. In accordance with other aspects of the disclosure, the p-type material layer  106  may also be formed below the barrier layer  108  between the barrier layer  108  and the substrate layer  102  and/or within the substrate layer  102 . 
     In accordance with aspects of the disclosure, at least some portions of the substrate layer  102  may include the p-type material layer  106 . In accordance with aspects of the disclosure, the p-type material layer  106  may be formed by ion implantation of aluminum (Al) and annealing. In other aspects, the p-type material layer  106  may be formed by ion implantation of boron, gallium, or any other material that may form a p-type layer or a combination of these. In one aspect, the p-type material layer  106  may be formed by implantation and annealing of Al prior to the growth of any GaN layers. In one aspect, the ion implementation may utilize channeling implants. In one aspect, the channeling implants may include aligning the ion beam to the substrate layer  102 . Alignment of the ion beam may result in increased implanting efficiency. 
     Aspects of the disclosure may utilize implant channeling to controllably form implanted regions of the p-type material layer  106  in silicon carbide implementations of the substrate layer  102  that are highly uniform by depth and also result in reduced lattice damage. Channeling is experienced when ions are implanted along a crystal axis of the substrate layer  102 . When a direction of implantation is close to a major axis of the crystal lattice, the atoms in the crystal lattice appear to “line up” relative to the direction of implantation, and the implanted ions appear to travel down the channels created by the crystal structure to form the p-type material layer  106 . This reduces the likelihood of collisions between the implanted ions and the atoms in the crystal lattice. As a result, the depth of the implant of the p-type material layer  106  may be greatly increased. 
     In general, channeling occurs in silicon carbide when the direction of implantation is within about ±0.2° of a crystallographic axis of the silicon carbide crystal. In some aspects, the implantation may be greater than ±0.2° of the crystallographic axis of the silicon carbide crystal, however the implantation may be less effective. For example, when the direction of implantation is more than about ±0.2° of a crystallographic axis of the silicon carbide crystal, the atoms in the lattice may appear to be randomly distributed relative to the direction of implantation, which may reduce channeling effects. As used herein, the term “implant angle” refers to the angle between the direction of implantation and a crystallographic axis, such as the c-axis or &lt;0001&gt; axis, of the semiconductor layer into which ions are implanted. Thus, an implant angle of less than about 2° relative to the c-axis of a silicon carbide layer may be expected to result in channeling. However, other implant angles may be utilized as well. 
     In one aspect, the p-type material layer  106  may be formed by ion implantation of  27 Al in 4H—SiC implanted with channeling conditions with an implant energy of E 1 =100 keV with a dose of 1E13 cm 2  at 25° C. In one aspect, the p-type material layer  106  may be formed by ion implantation of  27 Al in 4H—SiC implanted with channeling conditions with an implant energy of E2=300 keV with a dose of 1E13 cm 2  at 25° C. However, other implant energies and doses are contemplated as well. For example, in some aspects the implant energy may be 20 keV to 80 keV, 80 keV to 120 keV, 120 keV to 160 keV, 160 keV to 200 keV, 200 keV to 240 keV, 240 keV to 280 keV, 280 keV to 340 keV, 340 keV to 400 keV, 20 keV to 400 keV, and/or 80 keV to 340 keV; and in some aspects the implant dose may be 0.6E13 cm 2  to 0.8E13 cm 2 , 0.8E13 cm 2  to 1.2E13 cm 2 , 1.2E13 cm 2  to 1.6E13 cm 2 , 1.6E13 cm 2  to 2E13 cm 2 , 0.6E13 cm 2  to 2E13 cm 2 , and/or 0.8E13 cm 2  to 1.2E13 cm 2 . Additionally, it should be noted that the p-type material layer  106  may be formed by implantation of other materials such as Boron (B), Gallium (Ga), and/or the like, and may be followed by a high temperature anneal. 
     In one aspect, the ion implantation may result in the p-type material layer  106  being a deep layer. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 1 μm or less. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.7 μm or less. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.5 μm or less. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.3 μm to 0.5 μm. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.2 μm to 0.6 μm. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.4 μm to 0.6 μm. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.6 μm to 0.8 μm. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.6 μm to 1.6 μm. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.6 μm to 2.1 μm. In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 1 μm to 5 μm. In one aspect, the p-type material layer  106  implantation and/or doping may be in the range of 5E15 to 5E17 per cm 3  and extend to depths up to 5 μm. 
     In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.05% to 0.3% of a thickness of the substrate layer  102 . In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.05% to 0.1% of a thickness of the substrate layer  102 . In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.1% to 0.15% of a thickness of the substrate layer  102 . In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.15% to 0.2% of a thickness of the substrate layer  102 . In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.2% to 0.25% of a thickness of the substrate layer  102 . In one aspect, the ion implantation may result in the p-type material layer  106  having a thickness of 0.25% to 0.3% of a thickness of the substrate layer  102 . 
     The p-type material layer  106  may be implanted within the substrate layer  102  and may be subsequently annealed. Annealing may allow for the implantation to be activated. In one aspect, a masking layer material may be utilized during implantation. In some aspects, during annealing of the p-type material layer  106 , a cap layer material may be used to cover the wafer surface to prevent dissociation of the substrate at high temperatures. Once the p-type material layer  106  has been formed, the masking layer material may be removed. Annealing may be performed at a temperature range of 1500-1850° C. for 5 minutes-30 minutes. Other annealing time and temperature profiles are contemplated as well. 
     In some aspects, the substrate layer  102  may be made of a p-type material SiC substrate. Further in this aspect, the substrate layer  102  being a p-type material SiC substrate may be subsequently subjected to the processes as described herein including implantation of additional p-type layers. In aspects of the transistor  100  of the disclosure, the p-type material layer  106  may be neutralized to limit the length of the p-type material layer  106 . In one aspect, neutralizing may include implantation of impurities. In one aspect, neutralizing the p-type material layer  106  may include absorbing the charge of the p-type material layer  106  with a material of opposite polarity. Another way to limit the length of the p-type material layer  106  may be to etch the p-type material layer  106 . Another way to limit the length of the p-type material layer  106  may be to use a masking material to limit the area for implantation. 
     In aspects of the transistor  100  of the disclosure, the p-type material layer  106  may be formed by growing the p-type material layer  106 . Growth may be epitaxial, for example. To limit the length of the p-type material layer  106 , the p-type material layer  106  may be etched or otherwise neutralized. In aspects of the transistor  100  of the disclosure, the substrate layer  102  may be etched and the p-type material layer  106  may be formed by growing the p-type material layer  106 . In one aspect, the growth may be epitaxial. 
     In aspects of the transistor  100  of the disclosure, the p-type material layer  106  may be an epitaxial layer and may be GaN. In some aspects, the p-type material layer  106  may be an epitaxial layer and may be GaN and the p-type material layer  106  may include magnesium (Mg), carbon (C), and/or Zinc. In some aspects, the p-type material layer  106  may be an epitaxial layer and may be GaN and the p-type material layer  106  may include implantation of magnesium (Mg), carbon (C), and/or Zinc. 
     In aspects of the transistor  100  of the disclosure, the substrate layer  102  may be etched and the p-type material layer  106  may be formed by growing the p-type material layer  106 . In one aspect, the growth may be epitaxial. 
     In aspects of the transistor  100  of the disclosure, the p-type material layer  106  may be an epitaxial layer formed of SiC. In some aspects, the p-type material layer  106  may be an epitaxial layer and may be SiC and the p-type material layer  106  may include Al and/or Br. In some aspects, the p-type material layer  106  may be an epitaxial layer and may be SiC and the p-type material layer  106  may include implantation of Al and/or Br. 
     In aspects of the transistor  100  of the disclosure, the p-type material layer  106  may be a graded layer. In one aspect, the p-type material layer  106  may be a step-graded layer. In one aspect, the p-type material layer  106  may be multiple layers. In one aspect, the p-type material layer  106  may be a graded layer. In one aspect, the p-type material layer  106  may be a step-graded layer. In one aspect, the p-type material layer  106  may be multiple layers. In particular aspects, the p-type material layer  106  may include a planer upper surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). In particular aspects, the p-type material layer  106  may include a planer lower surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). Where upper and lower are defined along the Y axis. Depending on the material of the substrate layer  102 , a nucleation layer  136  may be formed on the substrate layer  102  to reduce a lattice mismatch between the substrate layer  102  and a next layer in the transistor  100 . In one aspect, the nucleation layer  136  may be formed directly on the substrate layer  102 . In other aspects, the nucleation layer  136  may be formed on the substrate layer  102  with intervening layer(s), such as SiC epitaxial layer(s) formed on a SiC implementation of the substrate layer  102 . The nucleation layer  136  may include different suitable materials, such as a Group III-Nitride material, e.g., Al x In y1-x-y GaN (where 0&lt;=x&lt;=1, 0&lt;=y&lt;=1, x+y&lt;=1). The nucleation layer  136  may be formed on the substrate layer  102  using known semiconductor growth techniques such as Metal Oxide Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVPE), Molecular Beam Epitaxy (MBE), or the like. In some aspects, the nucleation layer is Aluminum Nitride (AlN) or Aluminum Gallium Nitride (AlGaN), such as undoped AlN or AlGaN. 
     In some aspects, a buffer layer  104  may be formed directly on the nucleation layer  136  or on the nucleation layer  136  with intervening layer(s). Depending on the aspect, the buffer layer  104  may be formed of different suitable materials such as a Group III-nitride such as Al x Ga y In (1-x-y) N (where 0&lt;=x&lt;=1, 0&lt;=y&lt;=1, x+y&lt;=1), e.g., GaN, AlGaN, AlN, and the like, or another suitable material. In one aspect, the buffer layer  104  is formed of GaN. The buffer layer  104  or portions thereof may be doped with dopants, such as, Fe and/or C or alternatively can be wholly or partly undoped. In one aspect, the buffer layer  104  is directly on the substrate layer  102 . In particular aspects, the buffer layer  104  may include a planer upper surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). In particular aspects, the buffer layer  104  may include a planer lower surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). Where upper and lower are defined along the Y axis. 
     In one aspect, the buffer layer  104  may include an upper portion of high purity GaN and the buffer layer  104  may also include a lower portion that may form an AlGaN back barrier to achieve better electron confinement. In one aspect, the lower portion that forms the back barrier may be AlGaN of n type. The back barrier construction may be implemented in any of the aspects of the disclosure. 
     In one aspect, the buffer layer  104  may be high purity GaN. In one aspect, the buffer layer  104  may be high purity GaN that may be a low-doped n-type. In one aspect, the buffer layer  104  may also use a higher band gap Group III-nitride layer as a back barrier, such as an AlGaN back barrier, on the other side of the buffer layer  104  from a barrier layer  108  to achieve better electron confinement. 
     In one aspect, the buffer layer  104  may have a buffer layer thickness defined as a distance between an upper surface of the substrate layer  102  and a lower surface of the barrier layer  108 . In one aspect, the buffer layer thickness may be less than 0.8 microns, less than 0.7 microns, less than 0.6 microns, less than 0.5 microns, or less than 0.4 microns. In one aspect, the buffer layer thickness may have a range of 0.8 microns to 0.6 microns, 0.7 microns to 0.5 microns, 0.6 microns to 0.4 microns, 0.5 microns to 0.3 microns, 0.4 microns to 0.2 microns, or 0.7 microns to 0.3 microns. 
     In one aspect, the transistor  100  may have an intervening layer(s) thickness defined as a length between an upper surface of the substrate layer  102  and a lower surface of the barrier layer  108 . In one aspect, the intervening layer(s) thickness may be less than 0.8 microns, less than 0.7 microns, less than 0.6 microns, less than 0.5 microns, or less than 0.4 microns. In one aspect, the intervening layer(s) thickness may have a range of 0.8 microns to 0.6 microns, 0.7 microns to 0.5 microns, 0.6 microns to 0.4 microns, 0.5 microns to 0.3 microns, or 0.4 microns to 0.2 microns. 
     The barrier layer  108  may be formed on the buffer layer  104 . In one aspect, the barrier layer  108  may be formed directly on the buffer layer  104 , and in other aspects, the barrier layer  108  is formed on the buffer layer  104  with intervening layer(s). Depending on the aspect, the buffer layer  104  may be formed of different suitable materials such as a Group III-nitride such as Al x Ga y In (1-x-y) N (where 0&lt;=x&lt;=1, 0&lt;=y&lt;=1, x+y&lt;=1), e.g., AlGaN, AlN, or InAlGaN, or another suitable material. In one aspect, the barrier layer  108  may be AlGaN, and in another aspect the barrier layer  108  is AlN. In one aspect, the barrier layer  108  may be undoped. In one aspect, the barrier layer  108  may be doped. In one aspect, the barrier layer  108  may be an n-type material. In some aspects, the barrier layer  108  may have multiple layers of n-type material having different carrier concentrations. In one aspect, the barrier layer  108  may be a Group III-nitride or a combination thereof. In particular aspects, the barrier layer  108  may include a planer upper surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). In particular aspects, the barrier layer  108  may include a planer lower surface that is generally parallel to an X axis as illustrated in  FIG. 1  and/or is generally parallel to an Z axis (perpendicular to the X axis and the Y axis). Where upper and lower are defined along the Y axis. 
     In one aspect, a bandgap of the buffer layer  104  may be less than a bandgap of the barrier layer  108  to form a two-dimensional electron gas (2DEG) at a heterointerface  152  between the buffer layer  104  and barrier layer  108  when biased at an appropriate level. In one aspect, a bandgap of the buffer layer  104  that may be GaN may be less than a bandgap of the barrier layer  108  that may be AlGaN to form the two-dimensional electron gas (2DEG) at a heterointerface  152  between the buffer layer  104  and barrier layer  108  when biased at an appropriate level. 
     In aspects of the disclosure, the heterointerface  152  may be between the barrier layer  108  and the buffer layer  104 . In one aspect, source  110  and drain  112  electrodes may be formed making ohmic contacts such that an electric current flows between the source  110  and the drain  112  electrodes via a two-dimensional electron gas (2DEG) induced at the heterointerface  152  between the buffer layer  104  and barrier layer  108  when a gate  114  electrode is biased at an appropriate level. In one aspect, the heterointerface  152  may be in the range of 0.005 μm to 0.007 μm, 0.007 μm to 0.009 μm, and 0.009 μm to 0.011 μm. 
     In one aspect, the source  110 , the drain  112  and the gate  114  may be formed on the barrier layer  108 . The source  110 , the drain  112 , and/or the gate  114  may be arranged directly on the barrier layer  108  or may be on intervening layer(s) on the barrier layer  108 , such as an AlGaN layer on an AlN barrier layer. Other or additional intervening layers are possible. For example, a spacer layer  116  of SiN, AlO, SiO, SiO 2 , AlN, or the like or combinations thereof can be provided on the barrier layer  108  or other intervening layers. In one aspect, the barrier layer  108  may include a region  164  under the source  110  and/or the drain  112  that is a N+ material. In one aspect, the barrier layer  108  may include a region  164  under the source  110  and/or drain  112  that is Si doped. In one aspect, the n-type dopants in the region  164  are implanted. 
     In one aspect, the source  110 , the drain  112  and the gate  114  may be formed on the buffer layer  104 . The source  110 , the drain  112 , and/or the gate  114  may be arranged directly on the buffer layer  104  or may be on intervening layer(s) on the buffer layer  104 , such as an AlGaN layer on an AlN barrier layer. In one aspect, the buffer layer  104  may include a region  164  under the source  110  and/or the drain  112  that is a N+ material. In one aspect, the buffer layer  104  may include a region  164  under the source  110  and/or drain  112  that is Si doped. In one aspect, the n-type dopants in the region  164  are implanted. 
     In some aspects, the source  110  and the drain  112  may be symmetrical with respect to the gate  114 . In some switch device application aspects, the source  110  and the drain  112  may be symmetrical with respect to the gate  114 . In some aspects, the source  110  and the drain  112  may be asymmetrical with respect to the gate  114 . In one aspect, the gate  114  may be a T-shaped gate. In one aspect, the gate  114  may be a non-T shaped gate. 
     To protect and separate the gate  114  and the drain  112 , a spacer layer  116  may be arranged on the barrier layer  108 , on a side opposite the buffer layer  104 , adjacent the gate  114 , the drain  112  and the source  110 . The spacer layer  116  may be a passivation layer made of SiN, AlO, SiO, SiO 2 , AlN, or the like, or a combination incorporating multiple layers thereof. In one aspect, the spacer layer  116  is a passivation layer made of SiN. In one aspect, the spacer layer  116  can be deposited using MOCVD, plasma chemical vapor deposition (CVD), hot-filament CVD, or sputtering. In one aspect, the spacer layer  116  may include deposition of Si 3 N 4 . In one aspect, the spacer layer  116  forms an insulating layer. In one aspect, the spacer layer  116  forms an insulator. In one aspect, the spacer layer  116  may be a dielectric. In one aspect, a spacer layer  116  may be provided on the barrier layer  108 . In one aspect, the spacer layer  116  may include non-conducting material such as a dielectric. In one aspect, the spacer layer  116  may include a number of different layers of dielectrics or a combination of dielectric layers. In one aspect, the spacer layer  116  may be many different thicknesses, with a suitable range of thicknesses being approximately 0.05 to 2 microns. In one aspect, the spacer layer  116  may include a material such as a Group III nitride material having different Group III elements such as alloys of Al, Ga, or In, with a suitable spacer layer material being Al x In y Ga 1-x-y  (where 0&lt;=x&lt;=1 and 0&lt;=y&lt;=1, x+y&lt;=1). 
     In some aspects, the gate  114  may be deposited in a channel formed in the spacer layer  116 , and a T-gate may be formed using semiconductor processing techniques understood by those of ordinary skill in the art. Other gate configurations are possible. 
     In aspects of the transistor  100  of the disclosure, the substrate layer  102  may be silicon carbide and include a carbon face. In one aspect, the substrate layer  102  may be silicon carbide and include a carbon face arranged adjacent the buffer layer  104 . In one aspect, the substrate layer  102  may be silicon carbide and include a carbon face and the substrate layer  102  may be flipped so as to be arranged adjacent the buffer layer  104 . In this aspect, the buffer layer  104  may be GaN having a nitrogen face adjacent the carbon face of the substrate layer  102 . In one aspect, the buffer layer  104  may be GaN having alternating GaN and N layers with a N layer and/or a nitrogen face adjacent the carbon face of the substrate layer  102 . 
     In aspects of the transistor  100  of the disclosure, the buffer layer  104  may include nonpolar GaN. In one aspect, the buffer layer  104  may include semipolar GaN. In one aspect, the buffer layer  104  may include hot wall epitaxy. In one aspect, the buffer layer  104  may include hot wall epitaxy having a thickness in the range of 0.15 microns to 0.25 microns, 0.2 microns to 0.3 microns, 0.25 microns to 0.35 microns, 0.3 microns to 0.35 microns, 0.35 microns to 0.4 microns, 0.4 microns to 0.45 microns, 0.45 microns to 0.5 microns, 0.5 microns to 0.55 microns, or 0.15 microns to 0.55 microns. The p-type material layer  106  may help avoid breakdowns and problems with material impurities. For example, without a p-type material layer  106 , the transistor  100  may need impurities, which do not discharge well. The p-type material layer  106  may be formed beneath the gate  114 , and may extend toward the source  110  and the drain  112  of the device. 
     In aspects of the transistor  100  of the disclosure, the buffer layer  104  may be designed to be of the high purity type where the Fermi level is in the upper half of the bandgap, which minimizes slow trapping effects normally observed in GaN HEMTs. In this regard, the traps under the Fermi level are filled always and thus slow transients may be prevented. In some aspects, the buffer layer  104  may be as thin as possible consistent with achieving good crystalline quality. Applicants have already demonstrated 0.4 μm layers with good quality. 
     In aspects of the transistor  100  of the disclosure, a Al x In y Ga 1-x-y  (where 0&lt;=x&lt;=1 and 0&lt;=y&lt;=1, x+y&lt;=1) nucleation layer  136  or buffer layer  104  may be grown on the substrate layer  102  via an epitaxial crystal growth method, such as MOCVD (Metalorganic Chemical Vapor Deposition), HVPE (Hydride Vapor Phase Epitaxy) or MBE (Molecular Beam Epitaxy). The formation of the nucleation layer  136  may depend on the material of the substrate layer  102 . 
     In aspects of the transistor  100  of the disclosure, the buffer layer  104  may be formed with Lateral Epitaxial Overgrowth (LEO). LEO can, for example, improve the crystalline quality of GaN layers. When semiconductor layers of a HEMT are epitaxial, the layer upon which each epitaxial layer is grown may affect the characteristics of the device. For example, LEO may reduce dislocation density in epitaxial GaN layers. 
     With reference to the description of  FIG. 8 , the transistor  100  may include a second spacer layer  117  that may be formed on the spacer layer  116  and the gate  114 . With reference to the description of  FIG. 9 , the transistor  100  may include a field plate  132 . With reference to the description of  FIG. 10 , the transistor  100  may include a connection  154  to the field plate  132 . 
       FIG. 2  shows a cross-sectional view of an aspect of a transistor according to the disclosure. 
     In one aspect of the disclosure, the p-type material layer  106  may not extend over the entire area of the transistor  100 . In this regard, the p-type material layer  106  may be selectively arranged as described herein, the p-type material layer  106  may be arranged over the entire length and selectively removed as described herein, the p-type material layer  106  may be arranged over the entire length and selectively electrically neutralized as described herein, or the like. Accordingly, the specific constructions of the p-type material layer  106  described below encompass any of these processes that result in the p-type material layer  106  having an operating construction and arrangement as noted below. In other words, the length and/or size of the p-type material layer  106  does not include a part that is partially electrically neutralized, partially etched, or the like. The length and/or size of the p-type material layer  106  may depend on the application of the transistor  100 , requirements for the transistor  100 , and the like. Limiting a length of the p-type material layer  106  reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     As shown in  FIG. 2 , the p-type material layer  106  may be present in limited areas as described in further detail below. In some aspects, the p-type material layer  106  may be present in a gate—source region. In some aspects, the p-type material layer  106  may be present in a gate—source region and also partly under the gate  114 . In some aspects, the p-type material layer  106  may be arranged at least partially under the gate  114  and/or the source  110 . In some aspects, the p-type material layer  106  may be arranged at least partially under the gate  114  and/or and not arranged under the source  110 . 
     In one aspect, the p-type material layer  106  may be arranged at least partially vertically under the gate  114  along the y-axis and may extend along the x-axis partially toward the source  110  and the drain  112 . In this aspect, no portion of the p-type material layer  106  may be located vertically along the y-axis below the source  110 ; and no portion of the p-type material layer  106  may be located vertically along the y-axis below the source  110 . In this aspect, a portion of the substrate layer  102  may be free of the p-type material layer  106  on a source side of the transistor  100 ; and a portion of the substrate layer  102  may be free of the p-type material layer  106  on a drain side of the transistor  100 . In this regard, a source side of the transistor  100  is defined as a side of the transistor  100  extending from the gate  114  toward and past the source  110  as illustrated in  FIG. 2 ; and a drain side of the transistor  100  is defined as a side of the transistor  100  extending from the gate  114  toward and past the drain  112  as illustrated in  FIG. 2 . 
     In one aspect, the p-type material layer  106  may be arranged at least partially vertically under the gate  114  along the y-axis and may extend along the x-axis partially toward the source  110  and the drain  112 . In this aspect, only a portion of the p-type material layer  106  may be located vertically along the y-axis below the source  110 ; and no portion of the p-type material layer  106  may be located vertically along the y-axis below the source  110 . In this aspect, a portion of the substrate layer  102  may not include the p-type material layer  106  located vertically along the y-axis below the source  110 . In this aspect, a portion of the substrate layer  102  may be free of the p-type material layer  106  on a source side of the transistor  100 ; and a portion of the substrate layer  102  may be free of the p-type material layer  106  on a drain side of the transistor  100 . 
     In one aspect, the p-type material layer  106  may be arranged at least partially vertically under the gate  114  along the y-axis and may extend along the x-axis partially toward the source  110  and the drain  112 . In this aspect, a portion of the p-type material layer  106  may be located vertically along the y-axis entirely below the source  110 ; and no portion of the p-type material layer  106  may be located vertically along the y-axis below the drain  112 . In this aspect, a portion of the substrate layer  102  may not include the p-type material layer  106  located vertically along the y-axis past the source  110 . In this aspect, a portion of the substrate layer  102  may be free of the p-type material layer  106  on a source side of the transistor  100 ; and a portion of the substrate layer  102  may be free of the p-type material layer  106  on a drain side of the transistor  100 . 
     In one aspect, the p-type material layer  106  may be arranged vertically under the gate  114  along the y-axis and may extend along the x-axis partially toward the source  110  and the drain  112 . In this aspect, a portion of the p-type material layer  106  may be located vertically along the y-axis entirely below the source  110 ; and no portion of the p-type material layer  106  may be located vertically along the y-axis below the source  110 . In this aspect, a portion of the substrate layer  102  may not include the p-type material layer  106  located vertically along the y-axis past the source  110 . In this aspect, a portion of the substrate layer  102  may be free of the p-type material layer  106  on a source side of the transistor  100 ; and a portion of the substrate layer  102  may be free of the p-type material layer  106  on a drain side of the transistor  100 . 
     With reference to  FIG. 2 , various dimensions of components of the transistor  100  will be described in order to define dimensions of the p-type material layer  106 . The gate  114  may have a width LG along a lower surface of the gate  114  that is adjacent the barrier layer  108  that is parallel to the X axis. In particular, the width LG may extend from one lower corner of the gate  114  to the other lower corner of the gate  114 . The definition of the width LG is illustrated in  FIG. 2 . In some aspects, the width LG may be between 0.05 μm and 0.6 μm, 0.5 μm and 0.6 μm, 0.4 μm and 0.5 μm, 0.3 μm and 0.4 μm, 0.2 μm and 0.3 μm, 0.1 μm and 0.2 μm, or 0.1 μm and 0.05 μm in length along the x-axis. In some aspects, a width of the gate  114  above a lower surface may be greater than the width LG as illustrated in  FIG. 2 . 
     The distance from the gate  114  to the source  110  may be defined as distance LGS. In particular, the distance LGS may be defined as a distance from a lower corner of the gate  114  on a source side to a lower corner of the source  110  on a gate side. The definition of the distance LGS is illustrated in  FIG. 2 . 
     The distance from the gate  114  to the drain  112  may be defined as the distance LGD. In particular, the distance LGD may be defined as a distance from a lower corner of the gate  114  on a drain side to a lower corner of the drain  112  on a gate side. The definition of the distance LGD is illustrated in  FIG. 2 . 
     In one aspect, the p-type material layer  106  may extend laterally along the x-axis from at least beneath the lower corner of the gate  114  on a source side toward the source  110  a distance LGPS. The definition of the distance LGPS is illustrated in  FIG. 2 . In some aspects, the distance LGPS may be between 1 μm and 6 μm, 5 μm and 6 μm, 4 μm and 5 μm, 3 μm and 4 μm, 2 μm and 3 μm, or 1 μm and 3 μm in length along the x-axis. 
     In one aspect, the p-type material layer  106  may extend laterally along the x-axis from at least beneath the lower corner of the gate  114  on a drain side toward the drain  112  a distance LGPD. In some aspects, the distance LGPD may be between 0.1 μm and 0.6 μm, 0.5 μm and 0.6 μm, 0.4 μm and 0.5 μm, 0.3 μm and 0.4 μm, 0.2 μm and 0.3 μm, or 0.1 μm and 0.3 μm in length along the x-axis. 
     Accordingly, a length of the p-type material layer  106  may be a sum of the distance LGPD, the width LG, and the distance LGPS. In this regard, a length of the p-type material layer  106  reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     In one aspect, the length LGPS may be 100% to 700% of LG, 100% to 200% of LG, 200% to 300% of LG, 300% to 400% of LG, 400% to 500% of LG, 500% to 600% of LG, or 600% to 700% of LG. 
     In one aspect, the length LG may be 10% to 180% of LGPD, 10% to 20% of LGPD, 20% to 30% of LGPD, 30% to 40% of LGPD, 40% to 50% of LGPD, 50% to 60% of LGPD, 60% to 70% of LGPD, 70% to 80% of LGPD, 80% to 90% of LGPD, 90% to 100% of LGPD, 100% to 110% of LGPD, 110% to 120% of LGPD, 110% to 130% of LGPD, 130% to 140% of LGPD, 140% to 150% of LGPD, 150% to 160% of LGPD, 160% to 170% of LGPD, or 170% to 180% of LGPD. 
     In one aspect, the length LGS may be 10% to 180% of LGPS, 10% to 20% of LGPS, 20% to 30% of LGPS, 30% to 40% of LGPS, 40% to 50% of LGPS, 50% to 60% of LGPS, 60% to 70% of LGPS, 70% to 80% of LGPS, 80% to 90% of LGPS, 90% to 100% of LGPS, 100% to 110% of LGPS, 110% to 120% of LGPS, 110% to 130% of LGPS, 130% to 140% of LGPS, 140% to 150% of LGPS, 150% to 160% of LGPS, 160% to 170% of LGPS, or 170% to 180% of LGPS. 
     In one aspect, the length LG may be 10% to 180% of LGPD, 10% to 20% of LGPD, 20% to 30% of LGPD, 30% to 40% of LGPD, 40% to 50% of LGPD, 50% to 60% of LGPD, 60% to 70% of LGPD, 70% to 80% of LGPD, 80% to 90% of LGPD, 90% to 100% of LGPD, 100% to 110% of LGPD, 110% to 120% of LGPD, 110% to 130% of LGPD, 130% to 140% of LGPD, 140% to 150% of LGPD, 150% to 160% of LGPD, 160% to 170% of LGPD, or 170% to 180% of LGPD. 
     In some aspects, the p-type material layer  106  may be under 0.6 μm in thickness. In some aspects, the p-type material layer  106  may be under 0.5 μm in thickness. In some aspects, the p-type material layer  106  may be under 0.4 μm in thickness. In some aspects, the p-type material layer  106  may be under 0.3 μm in thickness. In some aspects, the p-type material layer  106  may be under 0.2 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.1 and 0.6 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.5 and 0.6 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.4 and 0.5 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.3 and 0.4 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.2 and 0.3 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.1 and 0.3 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.05 and 0.25 μm in thickness. In some aspects, the p-type material layer  106  may be between 0.15 and 0.25 μm in thickness. 
     In one or more aspects, a part of a source side of the substrate layer  102  may be free of the p-type material layer  106 . In one or more aspects, a part of a drain side of the substrate layer  102  may be free of the p-type material layer  106 . In one or more aspects, a part of a source side of the substrate layer  102  may be free of the p-type material layer  106  and a part of a drain side of the substrate layer  102  may be free of the p-type material layer  106 . In one or more aspects, the p-type material layer  106  may be arranged under and across a length of the gate  114  and may extend toward the source  110  and the drain  112 . 
     In one or more aspects, a distance LGD may be a distance from a lower corner of the gate  114  on the drain  112  side to a lower corner of the drain  112  on a gate side; a distance LGS may be a distance from a lower corner of the gate  114  on the source  110  side to a lower corner of the source  110  on a gate side; and the distance LGD may be greater than the distance LGS. In one or more aspects, a distance LGPS may define a length of a portion of the p-type material layer  106  from a lower corner of the gate  114  on the source  110  side toward the source  110 ; a distance LGPD may define a length of a portion of the p-type material layer  106  from a lower corner of the gate  114  on the drain  112  side toward the drain  112 ; and the distance LGPS may be equal to the distance LGPD. In one or more aspects, a distance LGPS may define a length of a portion of the p-type material layer  106  from a lower corner of the gate  114  on the source  110  side toward the source  110 ; a distance LGPD may define a length of a portion of the p-type material layer  106  from a lower corner of the gate  114  on the drain  112  side toward the drain  112 ; and the distance LGPS may be greater than the distance LGPD. In one or more aspects, a distance LGPS may define a length of a portion of the p-type material layer  106  from a lower corner of the gate  114  on the source  110  side toward the source  110 ; a distance LGPD may define a length of a portion of the p-type material layer  106  from a lower corner of the gate  114  on the drain  112  side toward the drain  112 ; and the distance LGPD may be greater than the distance LGPS. 
     In one or more aspects, the p-type material layer  106  may extend toward the source  110  but does not vertically overlap the source  110 . In one or more aspects, the p-type material layer  106  may vertically overlap the source  110 . In one or more aspects, the p-type material layer  106  may extend toward the drain  112  but does not vertically overlap the drain  112 . In one or more aspects, the p-type material layer  106  may vertically overlap the drain  112 . In one or more aspects, the p-type material layer  106  may be electrically connected to the gate  114 . In one or more aspects, the gate  114  may be electrically connected to any external circuit or voltage. In one or more aspects, the p-type material layer  106  may have no direct electrical connections. In one or more aspects, the p-type material layer  106  may be electrically connected to the source  110 . 
     In some aspects, part of the voltage from a drain  112  to a source  110  may be dropped in the p-type material layer  106  region. This may also deplete the channel in the lateral direction. The lateral depletion may reduce the lateral field and increase breakdown voltage. Alternatively, a more compact structure can be obtained for a required breakdown voltage. The p-type material layer  106  may eliminate the need to have C or Fe doping of the buffer needed to sustain the applied drain voltage. Elimination of C and Fe leads to decreased current reduction under operating conditions (no trapping). Moreover, in some aspects the p-type material layer  106  may support the field. 
     In some aspects, the p-type material layer  106  may also be configured to have a varying doping and/or implantation profile perpendicular to the surface. In some aspects, the p-type material layer  106  may also be configured to have a varying profile perpendicular to the surface extending into the cross-sectional views of the Figures. The profile may be optimized to achieve desired breakdown voltage, device size, switching time, and the like. 
       FIG. 3  illustrates a semiconductor device that may include a plurality of unit cell transistors in accordance with an aspect of the disclosure. 
     As shown in  FIG. 3 , aspects of the disclosure may include a semiconductor device  400  that may include a plurality of the transistor  100 . In particular, the transistor  100  may be one of a plurality of unit cells  430  implemented in the semiconductor device  400 . 
     In particular,  FIG. 3  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 3  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 3  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     The semiconductor device  400  may include a gate bus  402  that may be connected to a plurality of gate fingers  406  that may extend in parallel in a first direction (e.g., the Z-direction indicated in  FIG. 3 ) that connect to or form part of the gate  114 . A source bus  410  may be connected to a plurality of parallel ones of source contacts  416  that connect to or form part of the source  110 . In some aspects, the source bus  410  may be connected to a ground voltage node on an underside of the semiconductor device  400 . A drain bus  420  may be connected to a plurality of drain contacts  426  that connect to or form part of the drain  112 . 
     As can be seen in  FIG. 3 , each gate finger  406  may run along the Z-direction between a pair of adjacent ones of the source contact  416  and the drain contact  426 . The semiconductor device  400  may include a plurality of unit cells  430 , where each one of the plurality of unit cells  430  includes an implementation of the transistor  100 . One of the plurality of unit cells  430  is illustrated by the dashed Box in  FIG. 3 , and includes a gate finger  406  that extends between adjacent ones of the source contact  416  and the drain contact  426 . 
     The “gate width” refers to the distance by which the gate finger  406  overlaps with its associated one of the source contact  416  and drain contact  426  in the Z-direction. That is, “width” of a gate finger  406  refers to the dimension of the gate finger  406  that extends in parallel to and adjacent an implementation of the source contact  416  and the drain contact  426  (the distance along the Z-direction). Each of the plurality of unit cells  430  may share one of the source contact  416  and/or the drain contact  426  with one or more adjacent ones of the plurality of unit cells  430 . Although a particular number of the of the plurality of unit cells  430  is illustrated in  FIG. 3 , it will be appreciated that the semiconductor device  400  may include more or less of the plurality of unit cells  430 . 
       FIG. 4  is a schematic cross-sectional view taken along line IV-IV of  FIG. 3 . 
     Referring to  FIG. 4 , the semiconductor device  400  may include a semiconductor structure  440  that includes the substrate layer  102 , the buffer layer  104 , the barrier layer  108 , and/or the like as described herein. The source contact  416  and the drain contact  426  may be on the barrier layer  108  as described herein. The gate fingers  406  may be on the substrate layer  102  between the source contacts  416  and the drain contacts  426  as described herein. While the gate fingers  406 , the source contact  416 , and the drain contacts  426  are all shown schematically in  FIG. 3  and  FIG. 4  as having a similar “dimension,” it will be appreciated that each may have different shapes and dimensions consistent with the disclosure. 
       FIG. 5  illustrates a top view of one aspect of a transistor according to the disclosure. 
     In particular,  FIG. 5  illustrates a configuration of the transistor  100  and/or the semiconductor device  400  in order to reduce and/or eliminate trapping within the transistor  100  associated with “gate lag effect.” The gate lag affect may occur particularly at high negative gate voltages. In particular,  FIG. 5  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 5  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 5  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     In one aspect, the p-type material layer  106  may be electrically connected at one end of the gate fingers  406 , at both ends of the gate fingers  406 , at one end of a plurality of the gate fingers  406 , at both ends of a plurality of the gate fingers  406 , at one end of every one of the gate fingers  406 , at both ends of every one of the gate fingers  406 , and/or the like. In one aspect, the p-type material layer  106  may be electrically connected at one end of the gate  114 , at both ends of the gate  114 , at one end of a plurality of the gate  114 , at both ends of a plurality of the gate  114 , at one end of every one of the gate  114 , at both ends of every one of the gate  114 , and/or the like. 
     In particular, the gate  114  and/or the gate fingers  406  may be connected to the p-type material layer  106  with a connection  550 . The connection  550  may be achieved by etching down to the p-type material layer  106  near one or more of the ends of the gate fingers  406  and/or the gate  114  and making a metal contact to the p-type material layer  106 . This metal may then be connected to the gate  114  and/or the gate fingers  406  metal electrically. In one aspect, the connection  550  may be implemented at least in part as a via. The via may extend through one or more layers of the transistor  100 . The via may extend through one or more of the second spacer layer  117 , the spacer layer  116 , the barrier layer  108 , the buffer layer  104 , and/or the like. 
     In one aspect, the connection  550  may have a p-type material contact on the p-type material layer  106 . The p-type material contact may be formed on the p-type material layer  106  in a recess provided in the buffer layer  104 , the barrier layer  108 , and/or the like. The p-type material contact may be electrically coupled to the p-type material layer  106 . The recess may extend down to the p-type material layer  106  to allow for the p-type material contact to be created there. The recess may be formed by etching the buffer layer  104 , the barrier layer  108 , and/or the like, and may also use a material to define the recess. The material may be removed after the recess has been created. 
     The connection  550  may include a connection to the p-type material layer  106 , to the gate  114 , and/or to the gate fingers  406 . In particular, the connection  550  or portions thereof may extend from the p-type material layer  106  and/or the p-type material contact in the recess formed in the transistor  100  and may extend up to the gate  114  and/or to the gate fingers  406 . 
     The connection  550  and/or the p-type material contact may be electrically coupled to the p-type material layer  106 . The recess may be configured as a partial recess, partial trench, or the like in a surface of the transistor  100 . In one aspect, a region or area under or adjacent the p-type material contact may be implanted and/or doped with p-dopants to form an electrical connection with the p-type material layer  106 . In one aspect, the layer may be an epitaxial material on which is provided the p-type material contact. 
     In one aspect, the connection  550  may include a conductive material, many different conductive materials, a suitable material being a metal, or combinations of metals, deposited using standard metallization methods. In one aspect, the materials may include one or more of titanium, gold, nickel, or the like. 
       FIG. 6  illustrates a top view of one aspect of a transistor according to the disclosure. 
     In particular,  FIG. 6  illustrates a configuration of the transistor  100  in order to reduce and/or eliminate trapping within the transistor  100  associated with “gate lag effect.” The gate lag affect may occur particularly at high negative gate voltages. In particular,  FIG. 6  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 6  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 6  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     In particular, the transistor  100  may include a connection  650 . The connection  650  may be achieved by etching down to the p-type material layer  106  near the ends of the gate fingers  406  and making a metal contact to the p-type material layer  106 . In one aspect, the connection  650  may be implemented at least in part as a via. The via may extend through one or more layers of the transistor  100 . The via may extend through one or more of the second spacer layer  117 , the spacer layer  116 , the barrier layer  108 , the buffer layer  104 , and/or the like. In certain aspects, the connection  650  may include a contact  652  electrically connected to receive an external signal or bias. In one aspect, a negative voltage may be applied to the contact  652 . In one aspect, the applied negative voltage may be more negative than a negative gate bias. In one aspect, the applied negative voltage may be −5 V to −75 V, −5 V to −15 V, −15 V to −25 V, −25 V to −35 V, −35 V to −45 V, −45 V to −55 V, −55 V to −65 V, and/or −65 V to −75 V. 
     In one aspect, the connection  650  may be arranged at one end of the gate fingers  406 , at both ends of the gate fingers  406 , at one end of a plurality of the gate fingers  406 , at both ends of a plurality of the gate fingers  406 , at one end of every one of the gate fingers  406 , at both ends of every one of the gate fingers  406 , and/or the like. In one aspect, the connection  650  may be arranged at one end of the gate  114 , at both ends of the gate  114 , at one end of a plurality of the gate  114 , at both ends of a plurality of the gate  114 , at one end of every one of the gate  114 , at both ends of every one of the gate  114 , and/or the like. 
     In one aspect, the connection  650  may have a p-type material contact on the p-type material layer  106 . The p-type material contact may be formed on the p-type material layer  106  in a recess provided in the buffer layer  104 , the barrier layer  108 , and/or the like. The p-type material contact may be electrically coupled to the p-type material layer  106 . The recess may extend down to the p-type material layer  106  to allow for the p-type material contact to be created there. The recess may be formed by etching the buffer layer  104 , the barrier layer  108 , and/or the like, and may also use a material to define the recess. The material may be removed after the recess has been created. 
     The connection  650  may include a connection to the p-type material layer  106  and/or the contact  652 . In particular, the connection  650  or portions thereof may extend from the p-type material contact in the recess formed in the transistor  100  and may extend up to the contact  652 . 
     The connection  650 , the contact  652 , and/or the p-type material contact may be electrically coupled to the p-type material layer  106 . The recess may be configured as a partial recess, partial trench, or the like in a surface of the transistor  100 . In one aspect, a region or area under or adjacent the p-type material contact may be implanted and/or doped with p-dopants to form an electrical connection with the p-type material layer  106 . In one aspect, the layer may be an epitaxial material on which is provided the p-type material contact. 
     In one aspect, the contact  652  may be configured as a contact pad. In this aspect, the p-type material layer  106  through the connection  650  and/or the contact  652  may receive its own bias and signals. In this regard, the p-type material layer  106  may be used to modulate characteristics of the transistor  100 . 
     In one aspect, the connection  650  and/or the contact  652  may include a conductive material, many different conductive materials, a suitable material being a metal, or combinations of metals, deposited using standard metallization methods. In one aspect, the materials may include one or more of titanium, gold, nickel, or the like. 
     In one aspect, the connection  650  may be a metallic connection that extends from the p-type material contact to the contact  652 . In one aspect, the contact  652  may be a buried contact pad. In this regard, the contact  652  may be buried in any one of the above-noted structures of the transistor  100 . In one aspect, the contact  652  may be arranged on the barrier layer  108 . In one aspect, the contact  652  may be arranged directly on the barrier layer  108 . In one aspect, the contact  652  may be arranged on a spacer layer  116  on the barrier layer  108 . In one aspect, the contact  652  may be separate and separated from the gate  114 , the source  110 , and/or the drain  112 . 
       FIG. 7  illustrates a top view of one aspect of a transistor according to the disclosure. 
     In particular,  FIG. 7  illustrates a configuration of the transistor  100  in order to reduce and/or eliminate trapping within the transistor  100  associated with “gate lag effect.” The gate lag affect may occur particularly at high negative gate voltages. In particular,  FIG. 7  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 7  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 7  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     In particular, the transistor  100  may include the connection  650  and/or the contact  652  as described with reference to  FIG. 6 . Additionally,  FIG. 7  illustrates that the transistor  100  may further include a radiofrequency circuit  702 . In one aspect, the radiofrequency circuit  702  may be configured to prevent flow of RF current through the connection  650  and/or the contact  652 . In one aspect, the radiofrequency circuit  702  may be configured as a radiofrequency choke. 
     The radiofrequency circuit  702  may be implemented as one or more resistors, one or more capacitors, one or more inductors, one or more resistor circuits, one or more capacitor circuits, one or more inductor circuits, and/or the like. In one aspect, the radiofrequency circuit  702  may connect to the contact  652  and also connect to a negative voltage bias in series with an inductor; and one end of the inductor may connect to ground in series with a capacitor. In one aspect, the applied negative voltage may be −5 V to −75 V, −5 V to −15 V, −15 V to −25 V, −25 V to −35 V, −35 V to −45 V, −45 V to −55 V, −55 V to −65 V, and/or −65 V to −75 V. 
     The radiofrequency circuit  702  may be implemented as an integrated passive devices (IPD) and/or Integrated Passive Components (IPC). The radiofrequency circuit  702  implemented as an IPD may implement or support various radio frequency (RF) passive devices. The radiofrequency circuit  702  implemented as an IPD may implement or support various functional technology including providing one or more of resistance, inductance, capacitance, impedance matching circuits, matching circuits, input matching circuits, output matching circuits, harmonic filters, harmonic terminations, couplers, baluns, power combiners, power dividers, radio frequency (RF) circuits, radial stub circuits, transmission line circuits, fundamental frequency matching circuits, baseband termination circuits, second order harmonic termination circuits, and the like. The radiofrequency circuit  702  implemented as an IPD may implement or support various functional technology as input, output, and/or intrastage functions to the active region, an RF circuit, and/or the like. 
     Generally speaking, the radiofrequency circuit  702  implemented as an IPD may refer to implementations that they include an integrated circuit, which may be semiconductor based, and may include a number of passive devices. A custom circuit topology may be provided by the IPD. The radiofrequency circuit  702  implemented as an IPD may be used to provide some or all of the passive components for an impedance matching circuit, a matching circuit, an input matching circuit, an output matching circuit, a harmonic filter, a harmonic termination, a coupler, a balun, a power combiner, a power divider, a radio frequency (RF) circuit, a radial stub circuit, a transmission line circuit, a fundamental frequency matching circuit, a baseband termination circuit, a second order harmonic termination circuit, and the like. 
       FIG. 8  shows a cross-sectional view of another aspect of a transistor according to the disclosure. 
     In particular,  FIG. 8  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 8  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 8  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. In particular,  FIG. 8  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 8  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 8  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
       FIG. 8  further illustrates implementation of the second spacer layer  117 . The second spacer layer  117  may be provided over the gate  114  and/or the spacer layer  116 . The second spacer layer  117  may be a passivation layer made of SiN, AlO, SiO, SiO 2 , AlN, or the like, or a combination incorporating multiple layers thereof. 
     In one aspect, the second spacer layer  117  is a passivation layer made of SiN. In one aspect, the second spacer layer  117  can be deposited using MOCVD, plasma chemical vapor deposition (CVD), hot-filament CVD, or sputtering. In one aspect, the second spacer layer  117  may include deposition of Si 3 N 4 . In one aspect, the second spacer layer  117  forms an insulating layer. In one aspect, the second spacer layer  117  forms an insulator. In one aspect, the second spacer layer  117  may be a dielectric. In one aspect, a second spacer layer  117  may be provided on the spacer layer  116 . In one aspect, the second spacer layer  117  may include non-conducting material such as a dielectric. In one aspect, the second spacer layer  117  may include a number of different layers of dielectrics or a combination of dielectric layers. In one aspect, the second spacer layer  117  may be many different thicknesses, with a suitable range of thicknesses being approximately 0.05 to 2 microns. In one aspect, the second spacer layer  117  may include a material such as a Group III nitride material having different Group III elements such as alloys of Al, Ga, or In, with a suitable spacer layer material being Al x In y Ga 1-x-y  (where 0&lt;=x&lt;=1 and 0&lt;=y&lt;=1, x+y&lt;=1). 
       FIG. 9  shows a cross-sectional view of another aspect of a transistor according to the disclosure. 
     In particular,  FIG. 9  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. The transistor  100  of  FIG. 9  may include the p-type material layer  106  as described above. In particular,  FIG. 9  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 9  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 9  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
       FIG. 9  further illustrates implementation of the field plate  132 . In one aspect, the field plate  132  may be arranged on the second spacer layer  117  between the gate  114  and drain  112 . In one aspect, the field plate  132  may be deposited on the second spacer layer  117  between the gate  114  and the drain  112 . In one aspect, the field plate  132  may be electrically connected to one or more other components in the transistor  100 . In one aspect, the field plate  132  may not be electrically connected to any other components of the transistor  100 . In some aspects, the field plate  132  may be adjacent the gate  114  and a second spacer layer  117  of dielectric material may be included at least partially over the gate  114  to isolate the gate  114  from the field plate  132 . In some aspects, the field plate  132  may overlap the gate  114  and a second spacer layer  117  of dielectric material may be included at least partially over the gate  114  to isolate the gate  114  from the field plate  132 . 
     The field plate  132  may extend different distances from the edge of the gate  114 , with a suitable range of distances being approximately 0.1 to 2 microns. In some aspects, the field plate  132  may include many different conductive materials with a suitable material being a metal, or combinations of metals, deposited using standard metallization methods. In one aspect, the field plate  132  may include titanium, gold, nickel, titanium/gold, nickel/gold, or the like. 
     In one aspect, the field plate  132  may be formed on the second spacer layer  117  between the gate  114  and the drain  112 , with the field plate  132  being in proximity to the gate  114  but not overlapping the gate  114 . In one aspect, a space between the gate  114  and field plate  132  may be wide enough to isolate the gate  114  from the field plate  132 , while being small enough to maximize a field effect provided by the field plate  132 . 
     In certain aspects, the field plate  132  may reduce a peak operating electric field in the transistor  100 . In certain aspects, the field plate  132  may reduce the peak operating electric field in the transistor  100  and may increase the breakdown voltage of the transistor  100 . In certain aspects, the field plate  132  may reduce the peak operating electric field in the transistor  100  and may reduce trapping in the transistor  100 . In certain aspects, the field plate  132  may reduce the peak operating electric field in the transistor  100  and may reduce leakage currents in the transistor  100 . 
     In other aspects, for example, the spacer layer  116  is formed on the barrier layer  108  and on the gate  114 . In such aspects, the field plate  132  can be formed directly on the spacer layer  116 . Other multiple field plate configurations are possible with the field plate  132  overlapping or non-overlapping with the gate  114  and/or multiple field plates  132  being used. 
       FIG. 10  shows a cross-sectional view of another aspect of a transistor according to the disclosure. 
     In particular,  FIG. 10  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 10  may include the p-type material layer  106  as described above.  FIG. 10  further illustrates implementation of the field plate  132  that may be electrically connected to the source  110  through a connection  154 . In particular,  FIG. 10  illustrates a transistor  100  that may include any one or more aspects of the disclosure described herein. In particular, the transistor  100  of  FIG. 10  may include the p-type material layer  106  as described above. In this regard, the transistor  100  of  FIG. 10  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     In one aspect, the connection  154  may be formed on the spacer layer  116  and/or the second spacer layer  117  to extend between the source  110  and the field plate  132 . In some aspects, the connection  154  may include a conductive material, many different conductive materials, a suitable material being a metal, or combinations of metals, deposited using standard metallization methods. In one aspect, the materials may include one or more of titanium, gold, nickel, or the like. 
     In particular, the transistor  100  of  FIG. 10  illustrates the field plate  132  connected to the source  110  through the connection  154  (source—field plate interconnect). In one aspect, the connection  154  may be formed on the spacer layer  116  and/or the second spacer layer  117  to extend between the field plate  132  and the source  110 . In one aspect, the connection  154  may be formed with the field plate  132  during the same manufacturing step. In one aspect, a plurality of the connection  154  may be used. In one aspect, a plurality of the field plates  132  may be used. In one aspect, a plurality of the field plates  132  may be used and each of the plurality of field plates  132  may be stacked with a dielectric material therebetween. In some aspects, the connection  154  may include a conductive material, many different conductive materials, a suitable material being a metal, or combinations of metals, deposited using standard metallization methods. In one aspect, the materials may include one or more of titanium, gold, nickel, or the like. 
     In one aspect of the transistor  100  described herein, the gate  114  may be formed of platinum (Pt), nickel (Ni), and/or gold (Au), however, other metals known to one skilled in the art to achieve the Schottky effect, may be used. In one aspect, the gate  114  may include a Schottky gate contact that may have a three-layer structure. Such a structure may have advantages because of the high adhesion of some materials. In one aspect, the gate  114  may further include an overlayer of highly conductive metal. In one aspect, the gate  114  may be configured as a T-shaped gate. 
     In one aspect of the transistor  100  described herein, one or more metal overlayers may be provided on one or more of the source  110 , the contact  652 , the drain  112 , and the gate  114 . The overlayers may be Au, Silver (Ag), Al, Pt, Ti, Si, Ni, Al, and/or Copper (Cu). Other suitable highly conductive metals may also be used for the overlayers. In one or more aspects, the metal overlayer may electrically couple to the contact  652 . In another aspect, the source  110 , the contact  652 , the drain  112 , and the gate  114  may include Au, Silver (Ag), Al, Pt, Ti, Si, Ni, Al, and/or Copper (Cu). Other suitable highly conductive metals may also be used. 
     In one aspect of the transistor  100  described herein, a second buffer layer may be deposited or grown on a first implementation of the buffer layer  104  on a side of the first implementation of the buffer layer  104  opposite of the substrate layer  102 . In one aspect, the second buffer layer may be formed directly on the first implementation of the buffer layer  104 . In one aspect, the second buffer layer may be a high-purity material such as Gallium Nitride (GaN), AlN, or the like. In one aspect, the second buffer layer may be a high-purity GaN. In one aspect, the second buffer layer may be a high-purity AlN. The second buffer layer may be a p-type material or n-type material. In another aspect, the second buffer layer may be undoped. 
     In aspects of the transistor  100  of the disclosure, the contacts of the source  110 , the gate  114 , and/or the drain  112  may include Al, Ti, Si, Ni, and/or Pt. In some aspects, the contact  652  may include Al, Ti, Si, Ni, and/or Pt. In particular aspects, the material of the contacts of the source  110 , the gate  114 , and/or the drain  112  may be the same material as the contact  652 . In this aspect, utilizing the same material may be beneficial in that manufacturing may be easier, simplified, and/or less costly. In other aspects, the material of the contacts of the source  110 , the gate  114 , the drain  112 , and the contact  652  may be different. 
       FIG. 11  shows a process for making a transistor according to the disclosure. 
     In particular,  FIG. 11  shows an exemplary process  500  for making the transistor  100  of the disclosure. It should be noted that the process  500  is merely exemplary and may be modified consistent with the various aspects disclosed herein. In particular, the process  500  may include any one or more aspects of the disclosure described herein. In particular, the process  500  may include making the p-type material layer  106  as described above. In this regard, the process  500  implements a length of the p-type material layer  106  as described herein that reduces gate lag effect, avoids adverse effects on RF performance for certain transistor applications, and/or the like. 
     The process  500  may begin at step  502  by forming a substrate layer  102 . The substrate layer  102  may be formed consistent with the disclosure. For example, the substrate layer  102  may be made of Silicon Carbide (SiC). In some aspects, the substrate layer  102  may be a semi-insulating SiC substrate, a p-type substrate, an n-type substrate, and/or the like. In some aspects, the substrate layer  102  may be very lightly doped. In one aspect, the background impurity levels may be low. In one aspect, the background impurity levels may be 1E15/cm 3  or less. The substrate layer  102  may be formed of SiC selected from the group of 6H, 4H, 15R, 3C SiC, or the like. In another aspect, the substrate layer  102  may be GaAs, GaN, or other material suitable for the applications described herein. In another aspect, the substrate layer  102  may include sapphire, spinel, ZnO, silicon, or any other material capable of supporting growth of Group III-nitride materials. 
     The process  500  may include a step  504  of forming the p-type material layer  106 . The p-type material layer  106  may be formed as described in the disclosure. This may include implanting Al into the substrate layer  102  to form the p-type material layer  106  in the substrate layer  102 . For example, the p-type material layer  106  may be formed by ion implantation of Al and annealing. In one aspect, the p-type material layer  106  may be formed by implantation and annealing of Al prior to the growth of any GaN layers. In one aspect, the ion implementation may utilize channeling implants. In one aspect, the channeling implants may include aligning the ion beam to the substrate layer  102 . Alignment of the ion beam may result in increased implantation efficiency. In some aspects, the process  500  may further include implanting Al into the substrate layer  102  to form the p-type material layer  106  in the substrate layer  102 . Thereafter, the substrate layer  102  may be annealed as defined herein. In one aspect, the p-type material layer  106  may be formed by ion implantation of  27 Al in 4H—SiC implanted with channeling conditions with an implant energy of E 1 =100 keV with a dose of 1E13 cm 2  at 25° C. In one aspect, the p-type material layer  106  may be formed by ion implantation of  27 Al in 4H—SiC implanted with channeling conditions with an implant energy of E 2 =300 keV with a dose of 1E13 cm 2  at 25° C. However, other implant energies and doses are contemplated as well. 
     The process  500  may include a step  506  of forming the buffer layer  104  on the substrate layer  102 . The buffer layer  104  may be grown or deposited on the substrate layer  102  as described in the disclosure. In one aspect, the buffer layer  104  may be GaN. In another aspect, the buffer layer  104  may be formed with LEO. In one aspect, a nucleation layer  136  may be formed on the substrate layer  102  and the buffer layer  104  may be formed at step  506  on the nucleation layer  136 . The buffer layer  104  may be grown or deposited on the nucleation layer  136 . In one aspect, the buffer layer  104  may be GaN. In another aspect, the buffer layer  104  may be formed with LEO. 
     Further during the process  500  as part of step  508 , the barrier layer  108  may be formed on the buffer layer  104 . The barrier layer  108  may be formed as described in the disclosure. For example, the barrier layer  108  may be an n-type conductivity layer or may be undoped. In one aspect, the barrier layer  108  may be AlGaN. 
     Further during the process  500  as part of step  510 , to create a place for contact with the p-type material layer  106 , a recess may be created by removing at least part of the barrier layer  108  and at least part of the buffer layer  104 . The process  500  for forming the connection  550  and/or the connection  650  may include removing any material above the p-type material layer  106 , exposing the p-type material layer  106  on a side opposite of the substrate layer  102 . In another aspect of the disclosure, to create a place for contact with the p-type material layer  106 , the connection  550  and/or the connection  650  may be created by removing at least part of the barrier layer  108  and at least part of the buffer layer  104 . The recess formation process may remove any material above the p-type material layer  106  within a portion of a region associated with the source  110 , exposing the p-type material layer  106  on a side opposite of the substrate layer  102 . 
     Further in step  510 , the contact  652  may be formed. Once the p-type material layer  106  is exposed, nickel or another suitable material may be evaporated to deposit the contact  652 . The nickel or another suitable material may be annealed to form an ohmic contact, for example. In some aspects, the contacts of the contact  652  may include Al, Ti, Si, Ni, and/or Pt. Such a deposition and annealing process may be carried out utilizing conventional techniques known to those of skill in the art. For example, an ohmic contact for the contact  652  may be annealed at a temperature of from about 600° C. to about 1050° C. Once the contact  652  has been formed on the p-type material layer  106 , a metal overlayer may electrically couple the contact  652  of the p-type material layer  106  to the source  110 . Doing this may maintain the conductivity of the p-type material layer  106  and the source  110  at the same potential. 
     Further in step  510 , the radiofrequency circuit  702  may be created and connected to the contact  652 . In particular the radiofrequency circuit  702  may include one or more resistors, one or more capacitors, one or more inductors, one or more resistor circuits, one or more capacitor circuits, one or more inductor circuits, and/or the like as described herein. Additionally or alternatively, the radiofrequency circuit  702  may include any other features as set forth by the disclosure. 
     Further during the process  500  as part of step  512 , the source  110  may be arranged on the barrier layer  108 . The source  110  may be an ohmic contact of a suitable material that may be annealed. For example, the source  110  may be annealed at a temperature of from about 500° C. to about 800° C. for about 2 minutes. However, other times and temperatures may also be utilized. Times from about 30 seconds to about 10 minutes may be, for example, acceptable. In some aspects, the source  110  may include Al, Ti, Si, Ni, and/or Pt. In one aspect, a region  164  under the source  110  that is a N+ material may be formed in the barrier layer  108 . In one aspect, a region  164  under the drain  112  may be Si doped. 
     Further during the process  500  as part of step  512 , the drain  112  may be arranged on the barrier layer  108 . Like the source  110 , the drain  112  may be an ohmic contact of Ni or another suitable material, and may also be annealed in a similar fashion. In one aspect, an n+ implant may be used in conjunction with the barrier layer  108  and the contacts are made to the implant. In one aspect, a region  164  under the drain  112  that is a N+ material may be formed in the barrier layer  108 . In one aspect, a region  164  under the drain  112  may be Si doped. 
     Further during the process  500  as part of step  512 , the gate  114  may be arranged on the barrier layer  108  between the source  110  and the drain  112 . A layer of Ni, Pt, AU, or the like may be formed for the gate  114  by evaporative deposition or another technique. The gate structure may then be completed by deposition of Pt and Au, or other suitable materials. In some aspects, the contacts of the gate  114  may include Al, Ti, Si, Ni, and/or Pt. 
     Further during the process  500  as part of step  512 , the spacer layer  116  may be formed. The spacer layer  116  may be a passivation layer, such as SiN, AlO, SiO, SiO 2 , AlN, or the like, or a combination incorporating multiple layers thereof, which may be deposited over the exposed surface of the barrier layer  108 . 
     The source  110  and the drain  112  electrodes may be formed making ohmic contacts such that an electric current flows between the source  110  and drain  112  electrodes via a two-dimensional electron gas (2DEG) induced at the heterointerface  152  between the buffer layer  104  and barrier layer  108  when a gate  114  electrode is biased at an appropriate level. In one aspect, the source  110  may be electrically coupled to the barrier layer  108 , the drain  112  may be electrically coupled to the barrier layer  108 , and the gate  114  may be electrically coupled to the barrier layer  108  such that an electric current flows between the source  110  and the drain  112  via a two-dimensional electron gas (2DEG) induced at the heterointerface  152  between the buffer layer  104  and the barrier layer  108  when the gate  114  electrode is biased at an appropriate level. In one aspect, the source  110  may be electrically coupled to the transistor  100 , the drain  112  may be electrically coupled to the transistor  100 , and the gate  114  may be electrically coupled to the transistor  100  such that an electric current flows between the source  110  and the drain  112  via a two-dimensional electron gas (2DEG) induced at the heterointerface  152  between the buffer layer  104  and the barrier layer  108  when a gate  114  is biased at an appropriate level. In various aspects, the gate  114  may control a flow of electrons in the 2DEG based on a signal and/or bias placed on the gate  114 . In this regard, depending on a composition of the layers and/or a doping of the layers, the transistor  100  can be normally on or the transistor  100  can be normally off with no bias or signal on the gate. In one aspect, the heterointerface  152  may be in the range of 0.005 μm to 0.007 μm, 0.007 μm to 0.009 μm, and 0.009 μm to 0.011 μm. 
     The gate  114  may extend on top of a spacer or the spacer layer  116 . The spacer layer  116  may be etched and the gate  114  deposited such that the bottom of the gate  114  is on the surface of barrier layer  108 . The metal forming the gate  114  may be patterned to extend across spacer layer  116  so that the top of the gate  114  forms a field plate  132 . 
     Further during some aspects of the process  500  as part of step  512 , a second spacer layer  117  may be formed and a field plate  132  may be arranged on top of the second spacer layer  117  and may be separated from the gate  114 . In one aspect, the field plate  132  may be deposited on the second spacer layer  117  between the gate  114  and the drain  112 . In some aspects, the field plate  132  may include many different conductive materials with a suitable material being a metal, or combinations of metals, deposited using standard metallization methods. In one aspect, the field plate  132  may include titanium, gold, nickel, titanium/gold, nickel/gold, or the like. 
     In one aspect, the connection  154  may be formed with the field plate  132  during the same manufacturing step (see  FIG. 10 ). In one aspect, a plurality of the field plates  132  may be used. In one aspect, a plurality of the field plates  132  may be used and each of the plurality of field plates  132  may be stacked with a dielectric material therebetween. In one aspect, the field plate  132  extends toward the edge of gate  114  towards the drain  112 . In one aspect, the field plate  132  extends towards the source  110 . In one aspect, the field plate  132  extends towards the drain  112  and towards the source  110 . In another aspect, the field plate  132  does not extend toward the edge of gate  114 . Finally, the structure may be covered with a dielectric spacer layer such as silicon nitride. The dielectric spacer layer may also be implemented similar to the spacer layer  116 . Moreover, it should be noted that the cross-sectional shape of the gate  114 , shown in the Figures is exemplary. For example, the cross-sectional shape of the gate  114  in some aspects may not include the T-shaped extensions. Other constructions of the gate  114  may be utilized, for example, the construction of the gate  114  illustrated in  FIG. 8  or  FIG. 1 . 
     Further during some aspects of the process  500  as part of step  512 , the connection  550  may be formed. In one aspect, the connection  550  may be formed to extend between the p-type material layer  106  and the gate  114 . Further during some aspects of the process  500  as part of step  512 , the connection  154  may be formed. In some aspects, the field plate  132  may be electrically connected to the source  110  with the connection  154 . In one aspect, the connection  154  may be formed on the second spacer layer  117  to extend between the field plate  132  and the source  110 . 
     It should be noted that the steps of process  500  may be performed in a different order consistent with the aspects described above. Moreover, the process  500  may be modified to have more or fewer process steps consistent with the various aspects disclosed herein. In one aspect of the process  500 , the transistor  100  may be implemented with only the p-type material layer  106 . In one aspect of the process  500 , the transistor  100  may be implemented with the p-type material layer  106  and the p-type material layer  106 . In one aspect of the process  500 , the transistor  100  may be implemented with only the p-type material layer  106 . 
     In one aspect of the transistor  100  as described herein, the p-type material layer  106  may be doped as highly as possible with minimum achievable sheet resistance. In one aspect, the p-type material layer  106  may have an implantation concentration less than 10 19 . In one aspect, the p-type material layer  106  may have an implantation concentration less than 10 20 . In one aspect, the p-type material layer  106  may have an implantation concentration of 10 17 -10 20 , 10 19 -10 20 , 10 18 -10 19 , or 10 17 -10 18 . In one aspect, the p-type material layer  106  may have an implantation concentration 10 19  or greater. In one aspect, the p-type material layer  106  may have an implantation concentration of 10 18 -10 20 , 10 18 -10 19 , or 10 19 -10 20 . 
     In one aspect of the transistor  100  as described herein, the p-type material layer  106  doping may be less than 1E17 cm 3 . In one aspect, the p-type material layer  106  doping may be less than 2E17 cm 3 . In one aspect, the p-type material layer  106  doping may be less than 6E17 cm 3 . In one aspect, the p-type material layer  106  doping may be less than 2E18 cm 3 . In one aspect, the p-type material layer  106  doping may be in the range of 5E15 to 5E17 per cm 3 . In these aspects, the p-type material layer  106  doping concentration may be greater than a doping concentration of the p-type material layer  106 . 
     Accordingly, the disclosure has presented a solution to addressing gate lag effect in Group-III nitride HEMTs and improving the performance of such devices. Additionally, the disclosure has presented a solution to addressing traps that cause memory effects that adversely affect performance. Moreover, the disclosure has set forth a simpler alternative solution to forming p-type layers in HEMTs. The disclosed structure can be readily fabricated with currently available techniques. Moreover, the disclosed use of a high-purity material minimizes drain lag effects. Additionally, the disclosed p-type material layer provides a retarding electric field to obtain good electron confinement with low leakage. Additionally, aspects of this disclosure have described in detail variations of transistors with p-type layers and the ways those p-type layers are formed. The disclosed transistors maximize RF power, allow for efficient discharge, and maximize breakdowns. 
     According to further aspects of this disclosure, transistors, such as GaN HEMTs, fabricated on high resistivity substrates may be utilized for high power RF (radio frequency) amplifiers, for high power radiofrequency (RF) applications, and also for low frequency high power switching applications. The advantageous electronic and thermal properties of GaN HEMTs also make them very attractive for switching high power RF signals. In this regard, the disclosure has described a structure with a buried p-layer under the source region to obtain high breakdown voltage in HEMTs for various applications including power amplifiers while at the same time eliminating drifts in device characteristics arising from trapping in the buffer and/or semi-insulating substrates. Use of buried p-layers may also be important in HEMTs for RF switches to obtain high breakdown voltage and good isolation between the input and output. 
     The following are a number of nonlimiting Examples of aspects of the disclosure. 
     One example includes an apparatus that includes a substrate; a group III-Nitride buffer layer on the substrate; a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; a source electrically coupled to the group III-Nitride barrier layer; a gate electrically coupled to the group III-Nitride barrier layer; a drain electrically coupled to the group III-Nitride barrier layer; and a p-region being arranged at least in the substrate, where the p-region extends toward a source side of the substrate; and where the p-region extends toward a drain side of the substrate. 
     The above-noted Example may further include any one or a combination of more than one of the following aspects. The apparatus of the above-noted example where: a part of the source side of the substrate is free of the p-region; and a part of the drain side of the substrate is free of the p-region. The apparatus of the above-noted example where: a portion of the substrate includes the p-region located vertically below the source; and another portion of the substrate does not include the p-region located vertically below the source. The apparatus of the above-noted example where: the substrate does not include the p-region located vertically below the source; and the substrate does not include the p-region located vertically below the drain. The apparatus of the above-noted example where the p-region is structured and arranged such that no portion of the p-region is located vertically below the drain. The apparatus of the above-noted example further includes a connection to the p-region that is electrically connected to the gate. The apparatus of the above-noted example further includes a connection to the p-region that is electrically connected to a contact to receive an external signal or bias. The apparatus of the above-noted example further includes a connection to the p-region that is electrically connected to a contact that is electrically connected to a radiofrequency circuit. The apparatus of the above-noted example further includes a field plate, where the p-region is implanted. The apparatus of the above-noted example further includes a field plate, where the field plate is electrically coupled to said source. The apparatus of the above-noted example, where the p-region is structured and arranged to extend a limited length parallel to the group III-Nitride barrier layer such that the p-region is not located vertically below areas past the source and the drain. The apparatus of the above-noted example where the p-region is arranged under and across a length of the gate and extends toward the source and the drain. The apparatus of the above-noted example where: a distance LGD is a distance from a lower corner of the gate on the drain side to a lower corner of the drain on a gate side; a distance LGS is a distance from a lower corner of the gate on the source side to a lower corner of the source on a gate side; and the distance LGD greater than the distance LGS. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS being equal to the distance LGPD. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS greater than the distance LGPD. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPD greater than the distance LGPS. The apparatus of the above-noted example where the p-region extends toward the source but does not vertically overlap the source. The apparatus of the above-noted example where the p-region vertically overlaps the source. The apparatus of the above-noted example where the p-region extends toward the drain but does not vertically overlap the drain. The apparatus of the above-noted example where the p-region vertically overlaps the drain. The apparatus of the above-noted example where the p-region is electrically connected to the gate. The apparatus of the above-noted example where the gate is electrically connected to any external circuit or voltage. The apparatus of the above-noted example where the p-region includes no direct electrical connections. The apparatus of the above-noted example where the p-region is electrically connected to the source. 
     One example includes a method of making a device that includes providing a substrate; providing a group III-Nitride buffer layer on the substrate; providing a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; electrically coupling a source to the group III-Nitride barrier layer; electrically coupling a gate to the group III-Nitride barrier layer; electrically coupling a drain to the group III-Nitride barrier layer; and providing a p-region being arranged at least in the substrate, where the p-region extends toward a source side of the substrate; and where the p-region extends toward a drain side of the substrate. 
     The above-noted Example may further include any one or a combination of more than one of the following aspects. The method of making the device of the above-noted example where: a part of the source side of the substrate is free of the p-region; and a part of the drain side of the substrate is free of the p-region. The method of making the device of the above-noted example where: a portion of the substrate includes the p-region located vertically below the source; and another portion of the substrate does not include the p-region located vertically below the source. The method of making the device of the above-noted example where: the substrate does not include the p-region located vertically below the source; and the substrate does not include the p-region located vertically below the drain. The method of making the device of the above-noted example further includes forming the p-region such that no portion of the p-region is located vertically below the drain. The method of making the device of the above-noted example further includes forming a connection to the p-region that is electrically connected to the gate. The method of making the device of the above-noted example further includes forming a connection to the p-region that is electrically connected to a contact to receive an external signal or bias. The method of making the device of the above-noted example further includes forming a connection to the p-region that is electrically connected to a contact that is electrically connected to a radiofrequency circuit. The method of making the device of the above-noted example further includes implanting the p-region. The method of making the device of the above-noted example further includes providing a field plate. The method of making the device of the above-noted example further includes providing a field plate, where the field plate is electrically coupled to said source. The method of making the device of the above-noted example where the p-region is structured and arranged to extend a limited length parallel to the group III-Nitride barrier layer such that the p-region is not located vertically below areas past the source and the drain. The method of making the device of the above-noted example where the p-region is arranged under and across a length of the gate and extends toward the source and the drain. The method of making the device of the above-noted example where: a distance LGD is a distance from a lower corner of the gate on the drain side to a lower corner of the drain on a gate side; a distance LGS is a distance from a lower corner of the gate on the source side to a lower corner of the source on a gate side; and the distance LGD greater than the distance LGS. The method of making the device of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS being equal to the distance LGPD. The method of making the device of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS greater than the distance LGPD. The method of making the device of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPD greater than the distance LGPS. The method of making the device of the above-noted example where the p-region extends toward the source but does not vertically overlap the source. The method of making the device of the above-noted example where the p-region vertically overlaps the source. The method of making the device of the above-noted example where the p-region extends toward the drain but does not vertically overlap the drain. The method of making the device of the above-noted example where the p-region vertically overlaps the drain. The method of making the device of the above-noted example where the p-region is electrically connected to the gate. The method of making the device of the above-noted example where the gate is electrically connected to any external circuit or voltage. The method of making the device of the above-noted example where the p-region includes no direct electrical connections. The method of making the device of the above-noted example where the p-region is electrically connected to the source. 
     One example includes an apparatus, that includes a substrate; a group III-Nitride buffer layer on the substrate; a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; a source electrically coupled to the group III-Nitride barrier layer; a gate electrically coupled to the group III-Nitride barrier layer; a drain electrically coupled to the group III-Nitride barrier layer; and a p-region being arranged at least in the substrate, where a part of a source side of the substrate is free of the p-region; and where a part of a drain side of the substrate is free of the p-region. 
     The above-noted Example may further include any one or a combination of more than one of the following aspects. The apparatus of the above-noted example, where: a portion of the substrate includes the p-region located vertically below the source; and another portion of the substrate does not include the p-region located vertically below the source. The apparatus of the above-noted example, where: the substrate does not include the p-region located vertically below the source; and the substrate does not include the p-region located vertically below the drain. The apparatus of the above-noted example, where the p-region is structured and arranged such that no portion of the p-region is located vertically below the drain. The apparatus of the above-noted example includes a connection to the p-region that is electrically connected to the gate. The apparatus of the above-noted example includes a connection to the p-region that is electrically connected to a contact to receive an external signal or bias. The apparatus of the above-noted example includes a connection to the p-region that is electrically connected to a contact that is electrically connected to a radiofrequency circuit. The apparatus of the above-noted example includes a field plate, where the p-region is implanted. The apparatus of the above-noted example includes a field plate, where the field plate is electrically coupled to said source. The apparatus of the above-noted example where the p-region is structured and arranged to extend a limited length parallel to the group III-Nitride barrier layer such that the p-region is not located vertically below areas past the source and the drain. The apparatus of the above-noted example where the p-region is arranged under and across a length of the gate and extends toward the source and the drain. The apparatus of the above-noted example where: a distance LGD is a distance from a lower corner of the gate on the drain side to a lower corner of the drain on a gate side; a distance LGS is a distance from a lower corner of the gate on the source side to a lower corner of the source on a gate side; and the distance LGD greater than the distance LGS. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS being equal to the distance LGPD. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS greater than the distance LGPD. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPD greater than the distance LGPS. The apparatus of the above-noted example where the p-region extends toward the source but does not vertically overlap the source. The apparatus of the above-noted example where the p-region vertically overlaps the source. The apparatus of the above-noted example where the p-region extends toward the drain but does not vertically overlap the drain. The apparatus of the above-noted example where the p-region vertically overlaps the drain. The apparatus of the above-noted example where the p-region is electrically connected to the gate. The apparatus of the above-noted example where the gate is electrically connected to any external circuit or voltage. The apparatus of the above-noted example where the p-region includes no direct electrical connections. The apparatus of the above-noted example where the p-region is electrically connected to the source. 
     One example includes a method of making a device that includes providing a substrate; providing a group III-Nitride buffer layer on the substrate; providing a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; electrically coupling a source to the group III-Nitride barrier layer; electrically coupling a gate to the group III-Nitride barrier layer; electrically coupling a drain to the group III-Nitride barrier layer; and providing a p-region being arranged at least in the substrate, where a part of a source side of the substrate is free of the p-region; and where a part of a drain side of the substrate is free of the p-region. 
     The above-noted Example may further include any one or a combination of more than one of the following aspects. The method of making the device of the above-noted example where: a portion of the substrate includes the p-region located vertically below the source; and another portion of the substrate does not include the p-region located vertically below the source. The method of making the device of the above-noted example where: the substrate does not include the p-region located vertically below the source; and the substrate does not include the p-region located vertically below the drain. The method of making the device of the above-noted example further includes forming the p-region such that no portion of the p-region is located vertically below the drain. The method of making the device of the above-noted example further includes forming a connection to the p-region that is electrically connected to the gate. The method of making the device of the above-noted example further includes forming a connection to the p-region that is electrically connected to a contact to receive an external signal or bias. The method of making the device of the above-noted example further includes forming a connection to the p-region that is electrically connected to a contact that is electrically connected to a radiofrequency circuit. The method of making the device of the above-noted example further includes implanting the p-region. The method of making the device of the above-noted example further includes providing a field plate. The method of making the device of the above-noted example further includes providing a field plate, where the field plate is electrically coupled to said source. The method of making the device of the above-noted example where the p-region is structured and arranged to extend a limited length parallel to the group III-Nitride barrier layer such that the p-region is not located vertically below areas past the source and the drain. The method of making the device of the above-noted example where the p-region is arranged under and across a length of the gate and extends toward the source and the drain. The method of making the device of the above-noted example where: a distance LGD is a distance from a lower corner of the gate on the drain side to a lower corner of the drain on a gate side; a distance LGS is a distance from a lower corner of the gate on the source side to a lower corner of the source on a gate side; and the distance LGD greater than the distance LGS. The method of making the device of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS being equal to the distance LGPD. The method of making the device of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS greater than the distance LGPD. The method of making the device of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPD greater than the distance LGPS. The method of making the device of the above-noted example where the p-region extends toward the source but does not vertically overlap the source. The method of making the device of the above-noted example where the p-region vertically overlaps the source. The method of making the device of the above-noted example where the p-region extends toward the drain but does not vertically overlap the drain. The method of making the device of the above-noted example where the p-region vertically overlaps the drain. The method of making the device of the above-noted example where the p-region is electrically connected to the gate. The method of making the device of the above-noted example where the gate is electrically connected to any external circuit or voltage. The method of making the device of the above-noted example where the p-region includes no direct electrical connections. The method of making the device of the above-noted example where the p-region is electrically connected to the source. 
     One example includes an apparatus, that includes a substrate; a group III-Nitride buffer layer on the substrate; a group III-Nitride barrier layer on the group III-Nitride buffer layer, the group III-Nitride barrier layer includes a higher bandgap than a bandgap of the group III-Nitride buffer layer; a source on the group III-Nitride barrier layer; a drain on the group III-Nitride barrier layer; a gate on the group III-Nitride barrier layer between the source and the drain; a p-region being arranged at least in the substrate; and where a part of a source side of the substrate is free of the p-region; and where a part of a drain side of the substrate is free of the p-region. 
     The above-noted Example may further include any one or a combination of more than one of the following aspects. The apparatus of the above-noted example where the p-region is arranged under and across a length of the gate and extends toward the source and the drain. The apparatus of the above-noted example where: a distance LGD is a distance from a lower corner of the gate on the drain side to a lower corner of the drain on a gate side; a distance LGS is a distance from a lower corner of the gate on the source side to a lower corner of the source on a gate side; and the distance LGD greater than the distance LGS. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS being equal to the distance LGPD. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPS greater than the distance LGPD. The apparatus of the above-noted example where: a distance LGPS defines a length of a portion of the p-region from a lower corner of the gate on the source side toward the source; a distance LGPD defines a length of a portion of the p-region from a lower corner of the gate on the drain side toward the drain; and the distance LGPD greater than the distance LGPS. The apparatus of the above-noted example where the p-region extends toward the source but does not vertically overlap the source. The apparatus of the above-noted example where the p-region vertically overlaps the source. The apparatus of the above-noted example where the p-region extends toward the drain but does not vertically overlap the drain. The apparatus of the above-noted example where the p-region vertically overlaps the drain. The apparatus of the above-noted example where the p-region is electrically connected to the gate. The apparatus of the above-noted example where the gate is electrically connected to any external circuit or voltage. The apparatus of the above-noted example where the p-region includes no direct electrical connections. The apparatus of the above-noted example where the p-region is electrically connected to the source. 
     While the disclosure has been described in terms of exemplary aspects, those skilled in the art will recognize that the disclosure can be practiced with modifications in the spirit and scope of the appended claims. These examples given above are merely illustrative and are not meant to be an exhaustive list of all possible designs, aspects, applications or modifications of the disclosure.