# Patent

## Title
Devices formed from a non-polar plane of a crystalline material and method of making the same

## Abstract

Materials, methods, structures and device including the same can provide a semiconductor device such as an LED using an active region corresponding to a non-polar face or surface of III-V semiconductor crystalline material. In some embodiments, an active diode region contains more non-polar III-V material oriented to a non-polar plane than III-V material oriented to a polar plane. In other embodiments, a bottom region contains more non-polar m-plane or a-plane surface area GaN than polar c-plane surface area GaN facing an active region.

## Background
This application is a continuation of U.S. patent application Ser. No. 12/753,049, filed on Apr. 1, 2010, and entitled “Devices Formed From a Non-Polar Plane of a Crystalline Material and Method of Making the Same,” which is a continuation of and claims the benefit of co-pending International Application No. PCT/US10/29552, filed on Apr. 1, 2010, and entitled “DEVICES FORMED FROM A NON-POLAR PLANE OF A CRYSTALLINE MATERIAL AND METHOD OF MAKING THE SAME,” which claims the benefit of U.S. Provisional Application No. 61/166,184, filed on Apr. 2, 2009, entitled “DEVICES FORMED FROM A NON-POLAR PLANE OF A CRYSTALLING MATERIAL AND METHOD OF MAKING THE SAME,” which applications are hereby incorporated in their entireties herein by reference.


TECHNICAL FIELD
The present invention relates to devices formed from a non-polar plane of a crystalline material, such as the non-polar plane of a III-N crystalline material and methods of making the same. One embodiment is directed to non-polar LEDs or methods of making the same, or more particularly, non-polar LEDs from III-nitride semiconductor materials and methods of making the same.
BACKGROUND
This section provides background information and introduces information related to various aspects of the disclosure that are described and/or claimed below. These background statements are not admissions of prior art.
The usefulness of gallium nitride (GaN), and its ternary and quaternary compounds incorporating aluminum and indium (AlGaN, InGaN, AlInGaN), has been well established, for example, in the fabrication of visible and ultraviolet optoelectronic devices and high-power electronic devices. These devices are typically grown epitaxially using growth techniques including molecular beam epitaxy (MBE), CVD, metalorganic chemical vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE).
As shown in FIG. 1, GaN and its alloys are most stable in the hexagonal wurtzite crystal structure, in which the structure is described by two (or three) equivalent basal plane axes that are rotated 120° with respect to each other (the a-axes), all of which are perpendicular to a unique c-axis. FIG. 1 illustrates an example c-plane 2, m-plane 4, and a-plane 6. Group III and nitrogen atoms occupy alternating c-planes along the crystal's c-axis. The symmetry elements included in the wurtzite structure dictate that III-nitrides possess a bulk spontaneous polarization along this c-axis, and the wurtzite structure exhibits piezoelectric polarization.
Current nitride technology for electronic and optoelectronic devices employs nitride films grown along the polar c-direction. However, related art c-plane quantum well structures in III-nitride (III-N) based optoelectronic and electronic devices suffer from the undesirable quantum-confined Stark effect (QCSE), due to the existence of strong piezoelectric and spontaneous polarizations. The strong built-in electric fields along the c-direction can significantly degrade the usefulness of these III-N materials.
One approach to eliminating the spontaneous and piezoelectric polarization effects in GaN optoelectronic devices is to grow the devices on non-polar planes, the m-planes and a-planes of the crystal. Such planes contain equal numbers of Ga and N atoms and are charge-neutral. Furthermore, subsequent non-polar layers are equivalent to one another so the bulk crystal will not be polarized along the growth direction. However, growth of GaN semiconductor wafers with a non-polar surface remains difficult. Accordingly, there exists a need to increase the efficiency and improve operating characteristics for III-nitride based optoelectronic and electronic devices, for example LEDs.
SUMMARY
One aspect of the present disclosure is to address problems or disadvantages of the related art or provide at least advantages described herein in whole or in part.
Another aspect of the present disclosure is to increase usage of a-plane and m-plane faces of crystalline materials, such as hexagonal or wurtzite structured crystal, in creating electronic devices.
Another aspect of the present disclosure is to increase the usage of non-polar faces of polar crystalline materials, such as III-N materials, and more particularly GaN, in creating electronic devices.
Another aspect of the present disclosure is to improve the extraction efficiency or the internal quantum efficiency of a semiconductor diode or light-emitting diodes (LEDs).
Another aspect of the present disclosure is to improve the extraction efficiency or the internal quantum efficiency of light-emitting diodes (LEDs) by using non-polar faces of III-N semiconductor crystalline material.
Another aspect of the present disclosure is to improve the extraction efficiency or the internal quantum efficiency of light-emitting diodes (LEDs) by exploiting non-polar planes of III-N semiconductors.
Embodiments according to the present invention provide methods, structures and apparatus that can provide a semiconductor diode or LED including at least an active diode region with more non-polar III-N semiconductor material than polar III-N semiconductor material.
Embodiments according to the present invention provide methods, structures and apparatus that can provide a semiconductor diode or an LED including bottom, active and top diode regions from a III-N semiconductor material where the active and top diode regions have fewer defects per unit area than the bottom diode region.
Embodiments according to the present invention provide methods, structures and apparatus that can provide a semiconductor diode or an LED including a cavity in a bottom diode material, an active diode region on a surface of the cavity and a top diode region in at least a portion of the cavity.
Embodiments according to the present invention provide methods, structures and apparatus that can use non-polar planes of III-N semiconductor material in an LED to increase an output efficiency.
These aspects may be especially applicable to devices incorporating III-N semiconductors, including but not limited to optoelectronic devices, a light emitting diode, a laser diode and a photovoltaic device.
Additional aspects and utilities of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
These and/or other aspects and utilities of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:
FIG. 1 is a diagram that illustrates an exemplary hexagonal crystal structure including c-planes, m-planes and a-planes.
FIG. 2 is a diagram that illustrates an exemplary configuration of a semiconductor diode.
FIG. 3 is a flowchart illustrating an embodiment of a method for forming an embodiment of a semiconductor diode according to the invention.
FIG. 4 is a diagram that illustrates a cross-sectional view of a related art GaN layer over a substrate.
FIGS. 5-7 are diagrams that illustrate respective cross-sectional views of an exemplary device structure for a light emitting diode including III-N active regions using non-polar faces.
FIG. 8 illustrates a cross-sectional view of an embodiment of a semiconductor diode including III-N material active regions oriented to non-polar planes for use in an exemplary LED device.
FIG. 9 illustrates a cross-sectional view of an embodiment of a semiconductor diode including III-N material active regions oriented to non-polar planes for use an in exemplary LED device.
FIGS. 10a-10d illustrate a cross-sectional view of various embodiment of semiconductor diodes including non-polar III-N active regions for use an in exemplary LED device.



DETAILED DESCRIPTION OF EMBODIMENTS
Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures.
As shown in FIG. 2, a diode can include a bottom diode region 220, an active diode region 230 and a top diode region 240, a first electrical contact 260 on the top of the device and a second electrical contact 250 on the bottom of the device. Each region 220, 230, 240 can contain multiple layers. The diode can be coupled to a substrate 210. As shown in FIG. 2, in one embodiment the substrate 210 can be coupled between the bottom contact 250 and the active diode region 230. While FIG. 2 illustrates a vertical diode structure, it is emphasized the invention is not limited to such configurations and other structures and methods embodying the invention will be apparent to one of ordinary skill.
As used herein, “top” and “bottom” for designating regions is considered nonlimiting, a matter of convenience. For example, consider a diode formed above a substrate with its top region formed above its bottom region. If the diode is flip-chip bonded to a handle wafer and then the substrate is removed, the frame of reference for viewing the diode typically is flipped. In this case, the top region will be viewed as being below the bottom region.
The bottom diode region 220 and the top diode region 240 preferably have opposite doping types. For example, if the bottom diode region 220 is predominantly n-type doped (with an electron donor such phosphorous, arsenic, or antimony), then the top diode region 240 will be predominantly p-type doped (with an electron acceptor such as boron or aluminum), and vice versa. The bottom diode region 220 and the top diode region 240 are preferably heavily doped to improve device characteristics.
The bottom contact 250 electrically connects to the active diode region 230, for example, through a via (not shown). As another example, at least some portion of the substrate 210 can have the same predominant doping type (e.g., n or p) as the top diode region 240 or the bottom diode region 220. Accordingly, a good electrical contact can be made between such diode regions and the substrate 210.
Exemplary structures of the active diode region 230 can depend upon numerous factors, including an intended application of the diode and/or corresponding device. In an LED, the active diode region may be an intrinsic region. In an LED, the top diode region 240, the active diode region 230, and the bottom diode region 220 may be duplicated multiple times to include both doped layers and thin undoped quantum wells where electrons and holes can recombine and generate photons.
In another example of a laser, the active diode region 230 can be similar to that of an LED. Reflective layers would be added to create a resonant cavity for the generated light to create a coherent or substantially coherent light source.
In another example of a diode, the active diode region 230 may not be a separately grown layer but comprise the P-N junction interfacing between the top diode region and bottom diode region.
In another example of a solar cell, the active diode region 230 can be a single layer of moderately n-doped or moderately p-doped semiconductor material to absorb incident photons and generate an electron-hole pair.
The III-N compounds used to form the diode regions are well known to those of skill in the art. Group III-N compounds can include binary, ternary, and quaternary forms. Examples of III-N compounds include aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), and their ternary and quaternary compounds. Those of skill in the art understand how to select and process these materials based on desired properties such as emitted light wavelength, bandgaps, lattice constants, doping levels, etc.
FIG. 3 is a flowchart that illustrates an example method for making a LED. In this example, the LED is created from GaN crystalline material, but the invention should not be considered to be limited to such material. For example, the invention may be made from other polar materials or other polar III-N semiconductor materials. In this example, the active diode region is formed between surfaces of the top and bottom diode regions, much of or the majority of such surfaces being non-polar plane surfaces. In another example, the surfaces between which the active region is positioned include more non-polar m-plane III-N semiconductor faces than c-plane polar semiconductor faces. In another example, these surfaces include more non-polar a-plane III-N semiconductor faces than c-plane polar semiconductor faces. In another example, the surface area of the non-polar plane faces of these surfaces is at least double, 5 times, 10 times, 50 times or more than the surface area of polar c-plane semiconductor faces of these surfaces. In another example, the surfaces of the top and bottom diode regions between which the active diode region is formed is substantially all non-polar faces of a polar crystal material (e.g., one or both of the a-planes or m-planes of GaN or other III-N material). In another example, surfaces of the active region include more non-polar III-N semiconductor faces than c-plane polar semiconductor faces.
FIG. 3 illustrates an example process. As shown in FIG. 3, in step 310, a layer of GaN is provided. This may be a GaN bulk substrate, or a GaN grown or otherwise formed on a supporting physical substrate. Alternatively, it may be that GaN is selectively grown (as compared to blanket growth) within selected areas of a substrate as part of a larger semiconductor process. This selective growth may be within a confined area, such as within an ART opening or trench. In this example, a conventional bulk GaN substrate is provided with its surface constituting a polar face (c-plane). In this example, the first layer of GaN corresponds to a bottom diode region 220 of the subsequently formed LED. Caused by III-N semiconductor material characteristics, as generally grown, conventional bulk polar substrates have their “c-plane” parallel to the substrate.
In step 320, the GaN is configured to expose one or both of an a-plane or m-plane. For example, the GaN is vertically etched to form openings, such as holes or trenches in the surface of the GaN. The thus configured GaN corresponds to the bottom diode region of the device.
In step 330, active diode regions are formed. Depending on the device being created, this may be a separate step from step 340 (discussed below) or part of step 340. For example, if an LED is being formed with an intrinsic region, step 330 may include epitaxially growing undoped GaN on the surface of the GaN surface configured by step 320. As another example, if a diode is being formed, step 330 may be the initial part of step 340 to form the PN junction interface (e.g., including a depletion region).
In step 340, a top diode region is formed. For example, this step may include epitaxially growing GaN on the structure resulting from step 330, the GaN including a dopant of opposite type than the dopant of the GaN layer provided in step 310. For example, if the GaN layer provided in step 310 is doped with an n-type dopant, the GaN grown in step 340 may be doped with a p-type dopant. If the GaN layer provided in step 310 is doped with a p-type dopant, the GaN grown in step 340 may be doped with an n-type dopant.
In step 350, contacts are added to provide electrical connections to the top and bottom diode regions. Although the example method illustrated in FIG. 3 has steps 310 through 350 performed in a certain order, the invention should not be construed as limited to such order. As one alternative example, contacts may be formed at any point during the method (e.g., they may be formed on a separate physical substrate to which the diode regions are later connected).
FIG. 4 illustrates an example of a conventional bulk polar GaN layer 12. As shown in FIG. 4, the polar GaN layer 12 is formed on a sapphire wafer substrate 10, however, other materials for the substrate may be used, such as silicon or silicon carbide. The substrate 10 may be, for example, a bulk silicon wafer, a bulk germanium wafer, a semiconductor-on-insulator (SOI) substrate, or a strained semiconductor-on-insulator (SSOI) substrate. The substrate 10 may include or consist essentially of a first semiconductor material, e.g., sapphire. Orientation of the sapphire wafer substrate is typically (1,0,0), however, embodiments according to the application are not intended to be so limited. FIG. 4 also shows a c-plane 14 of the polar GaN layer 12.
Growth of GaN on sapphire is known in the art, but provides a crystalline material that is high in defects including primarily dislocation defects e.g., at least 109/cm2. However, as illustrated in FIG. 4 the majority of dislocation defects occur perpendicular or substantially vertical to the c-plane 14 of the III-N material. Accordingly, in one embodiment, a vertical sidewall in the bulk GaN material will have a lower number of defects (e.g., a vertical sidewall will intersect fewer defects per surface unit area than a horizontal surface).
After the bulk GaN is provided, selected portions are removed to leave structures not oriented to the c-plane. For example, selected portions are removed to leave projections not oriented to the c-plane extending away from the top surface of the substrate. In one embodiment, projections are configured to use the m-plane or the a-plane of the GaN material (operation block 320). In one embodiment, projections are configured to not use the c-plane of the GaN material. For example, openings such as holes, recesses or cavities having prescribed dimensions (e.g., shapes) can be etched in to the bulk GaN. Such trenches can be formed using conventional photolithography techniques or reactive ion etching (RIE) processes. As illustrated in FIG. 5, an exemplary remaining structure 520 or projections can include first portions 524 (e.g., planar sides) that extend along the non-polar planes (e.g., m-planes or a-planes, collectively 540) of the crystalline material while selected portions 522 remain oriented to the c-plane. In one embodiment, the dimensions of the sides 524 are 2×, 5×, 10×, 20× or 100× larger than the portions 522. In one embodiment, the projections can be configured as fins or posts. In one embodiment, a bottom surface may have an intended configuration (e.g., an intended slope or prescribed profile such as a “v” shape).
As described above, an exemplary bottom diode region 220 can be doped in situ during epitaxial growth or ex situ by ion implantation. Again, the material for the bottom diode region preferably depends on the device.
In one embodiment, trenches 530 with substantially m-plane or a-plane sidewalls (e.g., vertical or horizontal sidewalls depending on an orientation) in the bulk GaN can be formed. The number of trenches may be 1 or more to even hundreds or more depending upon the desired application.
After the bottom diode region is configured, an active diode region is formed (operation block 330). In one embodiment, the active diode region can be epitaxially grown. As shown in FIG. 6, direction of exemplary epitaxial growth is indicated by the arrows 610. Growth of an active diode region 230 on exposed GaN surfaces on tops or bottoms or horizontal planes 522 of the projections can grow vertically. Growth of an active diode region 230 on exposed GaN surfaces on sides or vertical planes 524 of the projections can grow horizontally. An exemplary active diode region 230 can be doped in situ during epitaxial growth or ex situ by ion implantation. In one embodiment, the active diode region 230 is intrinsic (e.g., intrinsically doped).
In general, defects existing on an expitaxy growth surface tend to continue to create defects in material that is epitaxially grown from the defective growth surface. Extension of defects during epitaxial growth of the active diode regions is not shown in FIG. 6. However, since defects in GaN are predominantly vertical (see again FIGS. 4 and 5), the defects will tend to be parallel to sidewalls of the exposed projections. Many or most of the defects therefore will not intersect the sidewalls of the projections, and these sidewalls will have reduced or substantially defect free surfaces. Therefore, defectivity on the active diode region 230 shown in FIG. 6 grown on these sidewalls of the projections will also be reduced or substantially defect free. The defect density of the active diode region 230 grown on these sidewalls will be lower than that in the bottom diode region 220. As shown in FIG. 6, dashed region 630a in the active diode region 230 will have a defect density lower than that in the bottom diode region 220. According to one embodiment, defectivity in the active diode region 230 can be 2×, 5×, 10×, 20× or more lower than in the bottom diode region 220.
After the active diode region is configured, the top diode region is formed (operation block 340). In one embodiment, an exemplary top diode region 240 is epitaxially grown. Epitaxial growth for the top diode region 240 shown in FIG. 7 can be similar to that of the active diode region (e.g., epitaxial growth direction as indicated by the arrows 610 in FIG. 6). Growth of a top diode region 240 on exposed GaN surfaces (e.g., of the active diode region) on tops or bottoms or horizontal planes 522 of the projections can grow vertically. Growth of a top diode region 240 on exposed GaN surfaces on sides or vertical planes 524 of the projections can grow horizontally. One feature of the structure shown in FIG. 7 is that the top diode region 240 can partially (not shown) or completely fill an opening such as the opening 530 or an opening in the active diode region 230. One feature of the structure shown in FIG. 7 is that the top diode region 240 can fill multiple openings/trenches and makes electrical contact with active diode regions 230 in multiple openings/trenches. This architecture is particularly advantageous for LEDs because it can reduce or minimize the area of the top electrical contacts 260, which can block emission of the light generated within the active diode region 230. An exemplary top diode region 240 can be doped in situ during epitaxial growth or ex situ by ion implantation. Preferably, the top diode region 240 of the LED is heavily doped with an opposite type from the bottom diode region 220.
In one embodiment, defect levels in the top diode region are lower than in the bottom diode region. In one embodiment, defect levels in the top diode region are greater than in the active diode region. According to one embodiment, defectivity in the top diode region 240 can be 2×, 5×, 10×, 20× or more lower than in the bottom diode region 220.
In one embodiment, growth conditions for at least the active diode regions can be set or designed to favor horizontal growth from the m/a plane (e.g., 524 surfaces) over growth from the c-plane (e.g., 522 surfaces).
After the top diode region is completed, additional processing steps known in the art may optionally be employed to complete a corresponding semiconductor component, semiconductor device or semiconductor product (operation block 350). For example, top and bottom contacts can be added in some embodiments (operation block 350). In addition, some exemplary method embodiments can include bonding to a conductive wafer, bonding to a die or bonding to a package mounting point, removing the substrate and adding top and bottom contacts or the like.
After the top diode region 240 is configured, electrical contacts can be formed (operation block 350) as shown in FIG. 8. In one embodiment, an exemplary top electrical contact 814 and an exemplary bottom electrical contact 812 are provided to respectively directly contact the top and bottom diode regions 220, 240 for each opening/trench. Electrical contacts 812, 814 can be formed by various materials/processes known to one skilled in the art. Suitable materials for the electrical contacts can include, for example, materials such as a strip of conductive metal such as copper, silver, or aluminum, reflective conductive materials or a layer of relatively transparent conductive materials such as indium tin oxide. Further, there are many ways to couple the bottom contact 812 to the bottom diode region 220 though the substrate 100 such as contact vias (not shown) to make an electrically connection. The electrical contacts 812, 814 can operate as the top contact 260 and the bottom contact 250, respectively. In an alternative embodiment, a single contact (e.g., 812, 814) may be provided for a plurality of top diode regions 240 or a plurality of bottom diode regions 220 (e.g., in a plurality of openings/trenches).
For selected LED applications, the substrate 210 can degrade the performance of the device (e.g., absorb light). In one exemplary embodiment, a substrate can be removed as shown in FIG. 9. The substrate 210 (e.g., sapphire substrate) can be removed by well known methods in the art such grinding, etching, laser ablation or the like. An exemplary process (operation block 350) can include bonding a “handle” substrate or unit 910 to the top diode region 240 and adding electrical contacts 912, 914. Before bonding the handle substrate 910 to the top diode region 240, a corresponding surface of the top diode region 240 may be planarized by a suitable technique such as chemical mechanical planarization (CMP) to securely attach the handle substrate 910. Alternatively or in addition, a connection agent or layer (not shown) may be used to securely electrically connect the handle substrate 910 to the top diode region 240. Alternatively or in addition, an adhering agent or glue layer (not shown) may be used to securely bond the handle substrate 910 to the top diode region 240.
Then, the top contacts 260 and the bottom contacts 250 can be added by standard techniques. As shown in FIG. 9, one top electrical contact 914 and one bottom electrical contact 912 can be provided for two or more openings/trenches or active diode regions 230 in a corresponding opening/trench. Alternatively, the handle substrate 910 may be electrically conductive. In one embodiment, the handle substrate 910 can include or integrate the top contacts 914 for the top diode region 240. Further, the handle substrate 910 can include or be coupled to a device or package.
In related art LEDs, one factor limiting internal quantum efficiency is that the polar c-plane of GaN faces the active region. The exemplary method embodiment shown in FIG. 3 and/or exemplary embodiments shown in FIGS. 8-9 can deliver higher internal quantum efficiency because non-polar m-planes or a-planes of GaN face the active diode region. Further, such embodiments can provide LED structures with less c-plane polar oriented GaN material for one or more of the bottom diode region 220, the active diode region 230 and/or the top diode region 240.
In one embodiment, non-polar m-planes or a-planes of GaN can form an interface between the bottom diode region 220 and the active diode region 230. In one embodiment, non-polar m-planes or a-planes of GaN can form an interface between the active diode region 230 and the top diode region 240.
For selected embodiments according to the application, it may be desirable to increase a percentage of non-polar plane GaN to polar plane GaN in a corresponding device. In one exemplary embodiment, portions of non-polar plane GaN can be increased relative to polar GaN by relatively increasing a dimension of sidewall 524 or decreasing a dimension of bottom surface 522. In one exemplary embodiment, portions of non-polar plane GaN can be increased relative to polar plane GaN by removing selected portions of the polar GaN material during fabrication. FIGS. 10a-10b are a diagram that illustrates an exemplary configuration of a semiconductor diode. As shown in FIG. 10a, portions containing polar c-plane GaN in the top diode region 1040 can be reduced or removed. Removal of a top surface indicated in FIG. 10a stopped at the top diode region, however embodiments are not intended to be so limited, for example, GaN material removal could continue into the active diode region. As shown in FIG. 10b, portions containing polar c-plane GaN in the top diode region 1040 can be reduced or replaced with top contacts 1014. Reference number 1016 indicates a planarizing layer such as an insulator.
In one exemplary embodiment, portions of non-polar plane GaN can be increased relative to polar plane GaN by reducing or removing selected portions of the polar plane GaN material during fabrication. FIG. 10c is a diagram that illustrates an exemplary configuration of a semiconductor diode where portions containing polar plane GaN of an active diode region 1030 are removed prior to formation of the top diode region 1040. FIG. 10d is a diagram that illustrates an exemplary configuration of a semiconductor diode where polar plane GaN portions of a bottom diode region 1020, the active diode region 1030 and/or the top diode region are reduced or removed prior to formation of a “handle” substrate or unit 910′. In one embodiment, substantially all polar plane GaN material grown in the c-plane can be eliminated (e.g., removed) from a depletion region, active diode region or semiconductor diode.
Further, in selected embodiments, top contacts and/or bottom contacts can be 2D or 3D configured to reduce light impinging on polar GaN material in at least one of a bottom diode region, an active diode region or a top diode region.
In one embodiment of an LED, a bottom electrical contact (e.g., 220) can be a highly reflective conductive material that can reflect the internally created light so it will exit the LED from a selected surface or a desired surface. For example, a reflective bottom electrical contact can be made from materials such as such as silver. In another embodiment, such a reflective bottom electrode can be used in conjunction with a light transmissive substrate or an optically translucent/transparent substrate.
In one embodiment of an LED, a reflective layer can be incorporated adjacent selected ones of the bottom diode region 220, the active diode region 230 and/or the top diode region 240 to direct internally created light to exit the LED from a selected surface or a desired surface. For example, a reflective layer can be directly between a bottom diode region 220 and the substrate 210. The reflective layer can be formed by suitable materials/processes known to one skilled in the art.
One embodiment of a semiconductor diode can include a first region having a first dopant type, an active region and a second region having a second dopant type opposite to the first dopant type and an active region between the first and second regions. The active region is at a non-polar plane surface of the first or second region or between at least one non-polar plane surface of the first and second regions. Thus, the semiconductor diode can have a horizontal or vertical stacked structure. A ratio of non-polar surfaces/polar surfaces of the first region adjacent the active region is greater than 1. In one embodiment, at least the active region is a III-N crystalline material. In one embodiment, the active region is a pn junction or a depletion region of a pn junction. In one embodiment, the active region is an intrinsic region or a quantum well structure between the first and second regions. In this disclosure, a depletion region can be one type of active diode region or active region. First and second contacts can be correspondingly provided to the first and second regions.
The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction of an LED. LEDs incorporating III-N material can emit light including blue, green, infrared, ultraviolet and white (e.g., based on or incorporating a blue light). For example, blue LEDs can be based on the wide band gap semiconductors GaN (gallium nitride) and InGaN (indium gallium nitride). In conventional LEDs, one factor limiting internal quantum efficiency is that the polar c-plane of the GaN. Internal efficiency decrease of an active region or a corresponding LED device can vary by the color/wavelength of the light emitted. In one embodiment, a green light emitting LED is expected to experience an increase in efficiency over 100 times. In one embodiment, a green light emitting LED is expected to experience an increase in efficiency over 2×, over 5×, over 10× or more.
In one embodiment of a blue light LED or a white light LED according to the application, an efficiency can be more than 2 times greater, more than 5 times greater, more than 10 times greater, more than 25 times greater or more because of non-polar III-N semiconductor crystalline material.
In one embodiment of an infrared light LED according to the application, an efficiency can be more than 2 times greater, more than 5 times greater, more than 10 times greater, more than 25 times greater or more because of non-polar III-N semiconductor crystalline material.
In one embodiment of an ultraviolet light LED according to the application, an efficiency can be more than 2 times greater, more than 5 times greater, more than 10 times greater, more than 25 times greater or more because of non-polar III-N semiconductor crystalline material.
In one exemplary embodiment, doping levels of the top and bottom diode regions may be in the range of 1017-1020 cm−3, and a doping level of the active region may be below 1017 cm−3.
Lasers LEDs can suffer from disadvantages caused by using polarized material including at least an undesirable frequency shift and/or loss of efficiency. Such disadvantages can be reduced according to embodiments of the application.
Although exemplary embodiments were described using GaN, it is understood that any III-N semiconductor compound material may be used. According to embodiments of the invention, a III-N crystalline semiconductor material may be provided (e.g., selective epitaxial growth). In some embodiments, growth along a first direction of the III-N crystalline semiconductor material can be encouraged or growth along a second direction can be discouraged. In some embodiments, growth of non-polar plane III-N crystalline semiconductor material can be encouraged over polar plane III-N crystalline semiconductor material. In some embodiments, a-plane/m-plane oriented III-N crystalline semiconductor material can be encouraged and/or c-plane oriented III-N crystalline semiconductor material can be discouraged.
Although embodiments were described using non-polar planes, it is understood that any orientation that can reduce or eliminate the characteristic disadvantages of c-plane III-N semiconductor materials can be used (e.g., semi-planar, semi-polar).
Exemplary semiconductor diodes may be described in the context of a single diode or active diode region; however, one skilled in the art will understand that most applications require multiple diodes, typically integrated on a single chip. If a plurality of such semiconductor components, devices or products are formed for a single device or on a single chip, preferably they have identical electrically configurations and substantially identical performance.
As noted above, this invention has a wide variety of applications. While not limited to LED technology, this invention has many applications within LED technology.
Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with other ones of the embodiments. Furthermore, for ease of understanding, certain method procedures may have been delineated as separate procedures; however, these separately delineated procedures should not be construed as necessarily order dependent in their performance. That is, some procedures may be able to be performed in an alternative ordering, simultaneously, etc. In addition, exemplary diagrams illustrate various methods in accordance with embodiments of the present disclosure. Such exemplary method embodiments are described herein using and can be applied to corresponding apparatus embodiments, however, the method embodiments are not intended to be limited thereby.
Although few embodiments of the present invention have been illustrated and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting on the invention described herein. Scope of the invention is thus indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein. As used in this disclosure, the term “preferably” is non-exclusive and means “preferably, but not limited to.” Terms in the claims should be given their broadest interpretation consistent with the general inventive concept as set forth in this description. For example, the terms “coupled” and “connect” (and derivations thereof) are used to connote both direct and indirect connections/couplings. As another example, “having” and “including”, derivatives thereof and similar transitional terms or phrases are used synonymously with “comprising” (i.e., all are considered “open ended” terms)—only the phrases “consisting of” and “consisting essentially of” should be considered as “close ended”. Claims are not intended to be interpreted under 112 sixth paragraph unless the phrase “means for” and an associated function appear in a claim and the claim fails to recite sufficient structure to perform such function.
Below is a list of some embodiments:
(1) A method of making a diode comprises forming a first cladding layer including one or more fins of polar crystalline material, wherein major faces of the one or more fins are non-polar; forming an active region over one or more of said major faces; and forming a second cladding layer adjacent to said active region.
(2) A method of making a diode comprises providing a first cladding layer of a polar semiconductor crystalline material including a first surface with one or more holes formed therein, sidewalls of the one or more holes being non-polar faces of the polar semiconductor crystalline material; providing a second cladding layer opposite the first surface; and providing an active region interposed between the first and second cladding layers extending at least partially into the one or more holes.
(3) A method of making a diode comprises forming a first diode region; forming an active region adjacent the first diode region; and forming a second diode region adjacent the active region, wherein an area of one or more surfaces of the first diode region adjacent the active region that are non-polar is greater than an area of one or more surfaces of the first diode region that are polar.
(4) A method of making a light emitting diode comprises providing a first diode region; forming an active diode region adjacent the first diode region; and forming a second diode region adjacent the active diode region, wherein at least a portion of the active diode region and the second diode region correspond to a non-polar plane of the III-N semiconductor crystalline material.
(5) A method of making a light emitting diode comprises providing a bottom diode region from a III-N semiconductor material; forming an active diode region from a III-N semiconductor material adjacent the bottom diode region; and forming a top diode region from a III-N semiconductor material adjacent the active diode region, wherein the active and top diode regions have fewer defects per unit area than the bottom diode region.
(6) A method of making a light emitting diode comprises providing a bottom diode material; forming a cavity in the bottom diode material; forming an active diode region on a surface of the cavity; and depositing a top diode material in the cavity.
(7) A method of making a light emitting diode comprises providing bottom, active and top diode regions from III-N semiconductor material; and providing non-polar III-N semiconductor material in the LED to increase an output efficiency to over a prescribed amount.
(8) A method of making a light emitting diode comprises providing III-N semiconductor crystalline layer on a polar plane; forming a bottom diode region having at least one first surface aligned in a non-polar plane and at least one second surface aligned in a polar plane of the III-N semiconductor material layer; forming an active diode region adjacent the at least one first surface and the at least one second surface of the bottom diode region; and forming a top diode region adjacent the active diode region.
(9) A method of making a light emitting diode comprises providing a bottom diode region of III-N semiconductor material; forming an active diode region adjacent the bottom diode region on a non-polar surface of III-N semiconductor material; and forming a top diode region adjacent the active diode region.
(10) A method of making a light emitting diode comprises providing a first diode region; forming an active diode region adjacent the first diode region; and forming a second diode region adjacent the active diode region, wherein a first portion of the active diode region has a first output light efficiency and a second portion of the active diode region has a second lower output light efficiency.
The above-listed embodiments may each be further modified according to the features described below.
At least one of the active and top diode regions may have more total line defects than the bottom diode region.
A light output efficiency in a blue light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater, or more than 25 times greater. A light output efficiency in a green light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater, or more than 25 times greater. A light output efficiency in a white light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater, or more than 25 times greater. A light output efficiency in a ultraviolet light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater, or more than 25 times greater. A light output efficiency in an infrared light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater, or more than 25 times greater.
A ratio of non-polar surface area in the bottom diode region facing the active region to polar-plane surface area may be more than one. A ratio of non-polar surface area in the bottom diode region facing the active region to polar-plane surface area may be more than 2, more than 4, more than 10 or more than 50.
The active region may be III-N semiconductor material corresponding to a non-polar surface. A portion of the active diode region oriented to a polar surface of III-N semiconductor material may be less than 50%, less than 25%, less than 15%, less than 10% or less than 5%. A portion of the top diode region oriented to a polar surface of III-N semiconductor material may be less than 50%, less than 25%, less than 15%, less than 10% or less than 5%. A portion of the active diode region, the bottom diode region or the top diode region oriented to a polar surface of III-N semiconductor material may be less than 50%, less than 25%, less than 15%, less than 10% or less than 5%. A portion of the active diode region, the bottom diode region or the top diode region oriented to a non-polar surface of III-N semiconductor material may be greater than 50%, greater than 75%, greater than 85% or greater than 95%.
The diode regions may include one or more of the following: aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), and their ternary and quaternary compounds. The diode regions may include GaN.
The bottom region may be configured with an opening, wherein the opening is a trench, recess or hole. A semiconductor device may be configured over at least a part of the opening. The trench may be at least 2 times deeper than its width, at least 5 times deeper than its width, at least 10 times deeper than its width or the trench may be at least 100 times deeper than its width. The trench may be at least 10 times longer than its width or the trench may be at least 100 times longer than its width. The width of the openings may be one of 450 nm or less, 400 nm or less, 350 nm or less, 200 nm or less, 100 nm or less and 50 nm or less. The width of the openings may be one of 5 um or less, 2 um or less and 1 um or less.
A CMOS device may be integrated with a substrate. A substrate may comprise silicon, germanium or sapphire. A surface of the substrate exposed in the insulator pattern opening may be a (100) surface of the silicon substrate, and the substrate may be a single crystal substrate or a polycrystalline substrate.
The diode regions may be epitaxially grown. The bottom, active and top diode regions may be the same semiconductor crystalline material. The bottom region may be a different semiconductor crystalline material than at least the active region or the top diode region. The bottom and top diode regions may be doped with different doping concentrations. The top and active diode regions may be doped with different doping concentrations. The bottom and top diode regions may be doped with dopants of different types. Diode regions may be in situ doped or ion implanted.
At least one of the active and top diode regions may be formed by selective epitaxial growth including metal-organic chemical vapor deposition (MOCVD), atmospheric-pressure CVD (APCVD), low- (or reduced-) pressure CVD (LPCVD), ultra-high-vacuum CVD (UHVCVD), molecular beam epitaxy (MBE), or atomic layer deposition (ALD).
The bottom, active and top regions may be repeated. At least a portion of the active region corresponding to a polar face may be removed. At least a portion of the bottom diode region or the top diode region corresponding to a polar face may be removed.
The method may comprise an intrinsic active region. The active region may comprise a depletion region.
The method may be a method of manufacturing an LED. The method may be a method of manufacturing a laser diode. The method may be a method of manufacturing a photovoltaic device.
Below lists further embodiments:
(1) A diode comprises one or more fins of polar crystalline material, wherein major faces of the one or more fins are non-polar, said one or more fins constituting a first cladding layer; an active region formed around said one or more fins; and a second cladding layer formed adjacent to said active region.
(2) A diode comprises a first cladding layer of a polar crystalline material including a first surface with one or more holes therein, sidewalls of the one or more holes being non-polar faces of the polar crystalline material; a second cladding layer opposite the first surface and extending at least partially into the one or more holes; and an active region interposed between the first and second cladding layers.
(3) A diode comprises a first diode region; an active region adjacent the first diode region; and a second diode region adjacent the active region, wherein an area of one or more surfaces of the first diode region adjacent the active region that are non-polar is greater than an area of one or more surfaces of the first diode region that are polar.
(4) A light emitting diode comprises a first diode region; an active diode region of a III-N semiconductor crystalline material adjacent the first diode region; and a second diode region adjacent the active diode region, wherein at least a portion of the active diode region corresponds to a non-polar plane of the first diode region.
(5) A light emitting diode comprises a bottom diode region from a III-N semiconductor material; an active diode region from a III-N semiconductor material adjacent the bottom diode region; and a top diode region from a III-N semiconductor material adjacent the active diode region, wherein the active and top diode regions have fewer defects per unit area than the bottom diode region.
(6) A light emitting diode comprises a bottom diode material having a cavity therein; an active diode region on a surface of the cavity; and depositing a top diode material in the cavity.
(7) A light emitting diode comprises bottom, active and top diode regions from III-N semiconductor material, wherein non-polar III-N semiconductor material in the LED is configured to increase an output efficiency.
(8) A light emitting diode comprises a bottom diode region of III-N semiconductor crystalline layer on a polar plane having at least one first surface aligned in a non-polar plane and at least one second surface aligned in a polar plane of the III-N semiconductor material layer; an active diode region adjacent the at least one first surface and the at least one second surface of the bottom diode region; and a top diode region adjacent the active diode region.
(9) A light emitting diode comprises a bottom diode region of III-N semiconductor material; an active diode region adjacent the bottom diode region on a non-polar surface of III-N semiconductor material; and a top diode region adjacent the active diode region.
(10) A light emitting diode comprises a first diode region; an active diode region adjacent the first diode region; and a second diode region adjacent the active diode region, wherein a first portion of the active diode region has a first output light efficiency and a second portion of the active diode region has a second lower output light efficiency.
The above-listed embodiments may each be further modified according to the features described below.
At least one of the active and top regions may have more total line defects than the bottom diode region.
A light output efficiency in a blue light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater or more than 25 times greater. A light output efficiency in a green light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater or more than 25 times greater. A light output efficiency in a white light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater or more than 25 times greater. A light output efficiency in a ultraviolet light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater or more than 25 times greater. A light output efficiency in an infrared light LED may be more than 2 times greater, more than 5 times greater, more than 10 times greater or more than 25 times greater.
A ratio of non-polar surface area in the bottom diode region facing the active region to polar-plane surface area may be more than one. A ratio of non-polar surface area in the bottom diode region facing the active region to polar-plane surface area may be more than 2, more than 4, more than 10 or more than 50.
The active region may be III-N semiconductor material corresponding to a non-polar surface. A portion of the active diode region oriented to a polar surface of III-N semiconductor material may be less than 50%, less than 25%, less than 15%, less than 10% or less than 5%. A portion of the top diode region oriented to a polar surface of III-N semiconductor material may be less than 50%, less than 25%, less than 15%, less than 10% or less than 5%. A portion of the active region, the bottom diode region or the top diode region oriented to a polar surface of III-N semiconductor material may be less than 50%, less than 25%, less than 15%, less than 10% or less than 5%. A portion of the active region, the bottom diode region or the top diode region oriented to a non-polar surface of III-N semiconductor material may be greater than 50%, greater than 75%, greater than 85% or greater than 95%.
The diode regions may include one or more of the following: aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), and their ternary and quaternary compounds. The diode regions may include GaN.
The bottom region may be configured with an opening, wherein the opening is a trench, recess or hole. The diode may comprise a semiconductor device configured over at least a part of the opening. The trench may be at least 2 times deeper than its width, at least 5 times deeper than its width, at least 10 times deeper than its width or the trench may be at least 100 times deeper than its width. The trench may be at least 10 times longer than its width or the trench may be at least 100 times longer than its width. The width of the openings may be one of 450 nm or less, 400 nm or less, 350 nm or less, 200 nm or less, 100 nm or less and 50 nm or less. The width of the openings may be one of 5 um or less, 2 um or less and 1 um or less.
The diode regions may be epitaxially grown. The diode may further comprise a CMOS device integrated with a substrate. A substrate may comprise silicon, germanium or sapphire. A surface of the substrate exposed in the insulator pattern opening may be a (100) surface of the silicon substrate, and the substrate may be a single crystal substrate or a polycrystalline substrate.
The bottom, active and top diode regions may be the same semiconductor crystalline material. The bottom region may be a different semiconductor crystalline material than at least the active region or the top diode region. The bottom and top diode regions may be doped with different doping concentrations. The top and active diode regions may be doped with different doping concentrations. The bottom and top diode regions may be doped with dopants of different types. Diode regions may be in situ doped or ion implanted.
At least one of the active region and top diode region may be formed by selective epitaxial growth including metal-organic chemical vapor deposition (MOCVD), atmospheric-pressure CVD (APCVD), low- (or reduced-) pressure CVD (LPCVD), ultra-high-vacuum CVD (UHVCVD), molecular beam epitaxy (MBE), or atomic layer deposition (ALD).
The bottom, active and top regions may be repeated. At least a portion of the active region corresponding to a polar face may be removed. At least a portion of the bottom diode region or the top diode region corresponding to a polar face may be removed.
The diode may comprise an intrinsic active region. The active region may comprise a depletion region. The diode may be an LED, a laser diode, or a photovoltaic device.

## Claims

1. A method comprising:
providing a first layer of a first semiconductor crystalline material over a substrate, the first layer having a polar top surface;
forming a recess in the first layer, the recess having a non-polar sidewall surface of the first semiconductor crystalline material; and
forming a second layer of a second semiconductor crystalline material along the non-polar sidewall surface of the recess, the first layer forming a first diode region, the second layer forming a second diode region, an active region being interposed between the first diode region and the second diode region, the first diode region, the active region, and the second diode region forming a diode.

2. The method of claim 1, wherein a ratio of non-polar surface area of the first layer of the diode to polar surface area of the first layer of the diode is more than one.

3. The method of claim 1, wherein the first semiconductor crystalline material and the second semiconductor crystalline material are a same semiconductor crystalline material.

4. The method of claim 1, wherein the first semiconductor crystalline material and the second semiconductor crystalline material are different semiconductor crystalline materials.

5. The method of claim 1 further comprising removing at least a portion of the second layer along the polar top surface.

6. The method of claim 1 further comprising after forming the second layer, removing at least a portion of the first layer or the second layer corresponding to a bottom polar surface of the recess.

7. The method of claim 1 further comprising:
forming a first contact adjacent the substrate; and
forming a second contact adjacent the second layer.

8. A method comprising:
forming a first diode region comprising a III-N semiconductor crystalline material having a polar plane and a non-polar plane; and
forming a second diode region proximate the first diode region, an active diode region being disposed between the first diode region and the second diode region, at least a portion of the active diode region and the second diode region being along the polar plane and the non-polar plane of the III-N semiconductor crystalline material.

9. The method of claim 8, wherein a ratio of a non-polar surface area of the first diode region to a polar surface area of the first diode region is more than one.

10. The method of claim 8, wherein the first diode region has a recess, the non-polar plane being a sidewall of the recess.

11. The method of claim 8, wherein the first diode region and the second diode region are a same semiconductor crystalline material.

12. The method of claim 8, wherein the first diode region and the second diode region are a different semiconductor crystalline material.

13. The method of claim 8 further comprising removing at least a portion of the active diode region corresponding to a polar face.

14. The method of claim 8 further comprising removing at least a portion of the first diode region or the second diode region corresponding to a polar face.

15. A method comprising:
providing III-N semiconductor crystalline layer over a substrate, the III-N semiconductor crystalline layer having a polar plane top surface;
forming a bottom diode region having at least one first surface aligned in a non-polar plane of the III-N semiconductor crystalline layer and at least one second surface aligned in a polar plane of the III-N semiconductor crystalline layer;
forming an active diode region adjacent the at least one first surface and the at least one second surface of the bottom diode region; and
forming a top diode region adjacent the active diode region.

16. The method of claim 15, wherein a ratio of non-polar surface area in the bottom diode region to polar-plane surface area is more than one.

17. The method of claim 15, wherein the forming the bottom diode region comprises forming a recess in the III-N semiconductor crystalline layer, the at least one first surface aligned in a non-polar plane of the III-N semiconductor crystalline layer comprising a sidewall of the recess.

18. The method of claim 15, wherein the bottom diode region is a different semiconductor crystalline material than at least the active region or the top diode region.

19. The method of claim 15, wherein at least a portion of the active diode region corresponding to a polar face of the III-N semiconductor crystalline layer is removed.

20. The method of claim 15, wherein at least a portion of the bottom diode region or the top diode region corresponding to a polar face of the III-N semiconductor crystalline layer is removed.