Patent Publication Number: US-2021191164-A1

Title: Low voltage modulator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Application No. 62/952,313, filed Dec. 22, 2019, the content of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     As data communication demands increase in both volume and speed, optical communications have become an increasingly popular communication approach. For optical communications within a data center, for example, a short reach transceiver may be used to transmit and/or receive communications between computing elements. 
     BRIEF SUMMARY 
     Various embodiments provide a low power modulator that may be used by a short reach transceiver, for example, to generate a wavelength division multiplexing signal. For example, the modulator may be a Franz-Keldysh (FK) effect modulator. For example, the modulator may be an electro-absorption modulator that uses the FK effect to control or modulate the intensity of a laser beam, such as via application of an electric voltage. In various embodiments, the modulator comprises a waveguide configured to guide an optical carrier. In various embodiments, the waveguide comprises a waveguide material having a first contact layer deposited on one side of the waveguide material and a second contact layer deposited on the opposite side of the waveguide material. The first contact layer is doped with a P-type dopant and the first contact layer is doped with an N-type dopant. For example, the first and second contact layers may be doped polycrystalline silicon (poly-si), doped polycrystalline germanium (poly-ge), and/or other appropriately doped amorphous composition. In various embodiments, the waveguide material comprises GeSi. In various embodiments, a waveguide column is formed from the waveguide material such that the waveguide column is less than one micron in width. 
     According to a first aspect of the present disclosure, a modulator is provided. In an example embodiment, the modulator is an FK effect electro-absorption modulator. In an example embodiment, the modulator comprises a waveguide comprising a waveguide column comprising a waveguide material, the waveguide column having a first side and an opposite second side, the first and second sides extending out from a substrate; a first contact layer disposed on a first side of the waveguide that is doped with a P-type dopant; and a second contact layer disposed on a second side of the waveguide that is doped with an N-type dopant. In an example embodiment, the first contact layer and the second contact layer comprise at least one of at least one of polycrystalline silicon, polycrystalline germanium, or an amorphous composition . 
     According to another aspect of the present disclosure, a modulator is provided. In an example embodiment, the modulator comprises a substrate; waveguide material deposited onto the substrate and formed into a waveguide column; a first contact layer doped with a P-type dopant and deposited on a first side of the waveguide column; a second contact layer doped with an N-type dopant and deposited on a second side of the waveguide column; and first and second contacts, the first contact being in electrical communication with the first contact layer and the second contact being in electrical communication with the second contact layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  illustrates a cross-section of a waveguide, in accordance with an example embodiment; 
         FIG. 2  illustrates a cross-section of a portion of a modulator comprising the waveguide, in accordance with an example embodiment; 
         FIGS. 3A and 3B  provide plots showing example experimental and simulation results of dopant concentrations in a doped contact layer and adjacent waveguide material, in accordance with an example embodiment; 
         FIG. 4  provides a flowchart illustrating processes, procedures, and operations performed to fabricate the waveguide of a modulator, in accordance with an example embodiment; 
         FIG. 5  provides a plot showing the transmission loss as a function of waveguide width for four different waveguide column heights, according to an example embodiment; and 
         FIG. 6  provides simulation results of the electronic band structure across a waveguide in an example embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. As used herein, terms such as “top,” “about,” “around,” etc. are used for explanatory purposes in the examples provided below to describe the relative position of certain components or portions of components. As used herein, the terms “substantially” and “approximately” refer to tolerances within manufacturing and/or engineering standards. 
     Various embodiments relate to and/or provide an FK modulator comprising a waveguide. In various embodiments, the waveguide acts as a PIN junction. In general, a PIN junction comprises a P-region within which holes are the majority charge carrier, an intrinsic region within which there are not free charge carriers, and an N-region within which electrons are the majority charge carrier. The intrinsic region (e.g., a region with doping concentrations less than 1×10 14 -1×10 16  per cubic centimeter) acts as an insulator between the P-region and the N-region. For example, the intrinsic region may have a high resistance which obstructs the flow of electrons and/or holes therethrough such that the PIN junction acts as a capacitor. 
     As described in more detail with regard to  FIG. 5 , the width of the waveguide (e.g., the distance between the contact layers along the sides of the waveguides in a plane substantially perpendicular to the transmission axis of the waveguide) can significantly affect the transition loss of the waveguide. Conventional waveguides are approximately one micron in width. However, in order to accommodate the evolving bandwidth and power requirements of such waveguides, various embodiments provide waveguides having a width of less than one micron (e.g., a width in the range of 0.3 to 0.9 microns or 0.3 to 0.8 microns). When the width of the waveguide is reduced below one micron, the P-region and N-region of the PIN junction start to overlap. In other words, the intrinsic region which enables the PIN junction to act as a capacitor becomes too narrow to be functional and/or non-existent. Thus, a technical problem exists as to how to provide a wavelength with a width of less than a micron (e.g., in the range of 0.3 to 0.8 microns, for example) that is still a PIN junction that can function as a capacitor. Various embodiments of the present disclosure provide a technical solution to this technical problem, as will now be described in detail. 
     Example Waveguide 
       FIG. 1  illustrates a waveguide  100  that may be part of an example embodiment of a low power modulator. In various embodiments, the waveguide  100  is part of an FK effect modulator. For example, the waveguide  100  may be part of an FK effect electro-absorption modulator. In an example embodiment, the modulator is configured for performing multiplexing and demultiplexing in accordance with wavelength division multiplexing (WDM), such as coarse WDM (CWDM). In an example embodiment, the waveguide  100  is configured for propagating and/or transmitting light in the wavelength range of 1260-1670 nm. Thus, the waveguide  100  may be used for transmission and/or modulation of a broad range of wavelengths. For example, the waveguide  100  may be configured to propagate and/or transmit light having a characteristic wavelength of 1310 nm and/or 1550 nm. Various embodiments of the waveguide  100  may be compatible with various other wavelengths. For example, the waveguide material  116  may be selected based the desired wavelength and/or wavelength range for transmission and/or modulation. For example, the width w of the of the waveguide column  110  may be selected based on the desired wavelength and/or wavelength range for transmission and/or modulation. 
     In various embodiments, the waveguide  100  comprises waveguide material  116  formed into a waveguide column  110  configured to guide an electromagnetic wave, beam, pulse, and/or the like along the waveguide  100  in a direction substantially parallel to a transmission axis  115  of the waveguide  100 . As illustrated, the waveguide column  110  has a cross-section that is generally rectangular in a plane that is substantially perpendicular to the transmission axis  115  of the waveguide  100 . However, in various embodiments, the waveguide column  110  may have various different cross-sections, as appropriate for the application. For example, the cross-section of the waveguide  100  shown in  FIG. 1  is taken in a plane substantially perpendicular to the transmission axis  115  of the waveguide  100 . In an example embodiment, the waveguide  100  extends 20-100 microns in a direction that is substantially parallel to the transmission axis  115 . 
     In various embodiments, the waveguide  100  extends out from a substrate  105 . In the illustrated example embodiment, the substrate  105  comprises a silicon substrate  150  with a buried oxide layer  140  formed within the silicon substrate  150 . A second layer of silicon  120  may be disposed between the buried oxide layer  140  and the waveguide material  116 . In an example embodiment, the second layer of silicon  120  is in the range of 0.1-0.4 microns thick. 
     In various embodiments, the waveguide column  110  extends outward from the substrate  105 . For example, the waveguide material  116  may be deposited onto the substrate and then etched to form a waveguide column  110 . For example, the waveguide column  110  may be formed to have a substrate adjacent edge that abuts a surface of the substrate  105  (e.g., the layer of silicon  120 ). The waveguide column  110  may be further formed to have a first side  112  that extends out from the substrate  105  and a second side  114  that extends out from the substrate  105 . In the depicted embodiment, the transmission axis  115  of the waveguide  100  is disposed between the first side  112  and the second side  114  of the waveguide column  110  such that the waveguide  100  is configured to transmit electromagnetic waves, beams, pulses, and/or the like along the waveguide  100  between the first side  112  and the second side  114 . 
     In various embodiments, the width w of the waveguide column  110  (e.g., between the first side  112  and the second side  114 ) in a plane that that is substantially perpendicular to the transmission axis  115  (and along a line substantially parallel to the surface of the substrate  105  within the plane that is substantially perpendicular to the transmission axis  115 ) is less than one micron. For example, the width w of the waveguide column  110  may be in the range of 0.4 microns to 0.9 microns, in various embodiments. In various embodiments, the width w of the waveguide column  110  may be in the range of 0.2 or 0.4 to 0.8 microns. In an example embodiment, the width w of the waveguide column  110  is approximately  0 . 6  microns. In an example embodiment, the waveguide material  116  comprises GeSi. In various embodiments, the waveguide column  110  has a height h in the range of 0.1 microns to 1 micron. In various embodiments, the waveguide column  110  has a height h in the range of 0.2 to 0.5 microns. For example, in an example embodiment, the height h of the waveguide column  110  is approximately 0.25-0.4 microns. 
     Conventional waveguides comprising GeSi are doped such that a left side of the waveguide is doped with a first dopant and a right side of the waveguide is doped with a second dopant. However, when the width w of the waveguide material is reduced to less than one micron, a first dopant profile of the first dopant and a second dopant profile of the second dopant overlap in a central region of the waveguide such that the waveguide does not include an intrinsic region and is not a PIN junction. For example, when the first dopant profile of the first dopant and a second dopant profile of the second dopant overlap in a central region of the waveguide, the waveguide material fails to act as a capacitor anymore and does not provide an appropriate or functional waveguide for an FK effect modulator. In order to increase the bandwidth of such conventional waveguides in accordance with increases in bandwidth requirements for optical communications, the width w of the waveguide material may be decreased to reduce the absorption of an electromagnetic wave, beam, pulse, and/or the like being transmitted along the waveguide. This results in a technical problem as reduction of the width of the waveguide results in the waveguide not being a functional waveguide. Various embodiments provide a technical solution to this technical problem, as will now be described in more detail. 
     As shown in  FIG. 1 , the waveguide  100  comprises a first contact layer  130 A disposed and/or deposited on the first side  112  of the waveguide column  110  and a second contact layer  130 B disposed and/or deposited on the second side  114  of the waveguide column  110 . In various embodiments, the first contact layer  130 A comprises poly-si, poly-ge, an amorphous composition, and/or the like that is doped with a P-type dopant and the second contact layer  130 B comprises poly-si, poly-ge, an amorphous composition, and/or the like that is doped with an N-type dopant. As should be understood by one skilled in the art, in an example embodiment, the first contact layer  130 A may comprise poly-si, poly-ge, an amorphous composition, and/or the like that is doped with an N-type dopant and the second contact layer  130 B may comprise poly-si, poly-ge, an amorphous composition, and/or the like that is doped with a P-type dopant. In an example embodiment, the P-type dopant is boron and the N-type dopant is phosphorus, but other dopants may be used in other embodiments, as appropriate for the application. In various embodiments, the contact layers  130 A,  130 B have widths that are in the range of 0.1-0.3 microns. In various embodiments, the concentration profile of various dopants across the waveguide  100  (e.g., first contact layer  130 A, the waveguide column  110 , and the second contact layer  130 B) may be configured such that the extinction ratio enables the modulator  200  to operate at a high bandwidth. 
     In various embodiments, the first and second contact layers  130 A,  130 B are heavily doped with the corresponding dopant. For example, the first contact layer may be doped with at least 1×10 16  per cubic centimeter of the P-type dopant and the second contact layer may be doped with at least 1×10 16  per cubic centimeter of the N-type dopant. 
     In various embodiments, the first and second contact layers  130 A,  130 B are doped after they have been deposited onto the first and second sides  112 ,  114 , respectively, of the waveguide column  110 . Thus, in various embodiments, as the dopants are being diffused and/or implanted into the first and second contact layers  130 A,  130 B, some of the dopant may be diffused and/or implanted into the 0.1-0.2 microns of the waveguide column  110  that is adjacent the respective one of the first and second sides  112 ,  114 . For example, the approximately 0.1 microns of the waveguide column  110  closest to the first side  112  may have a concentration of 1×10 15  to 1×10 19  per cubic centimeter of the dopant diffused and/or implanted into the first contact layer  130 A. Similarly, the approximately 0.1 microns of the waveguide column  110  closest to the second side  114  may have a concentration of 1×10 15  to 1×10 19  per cubic centimeter of the dopant diffused and/or implanted into the second contact layer  130 B. However, by 0.2 microns into the waveguide column  110  from each of the first and second sides, the concentration of a respective dopant present is low enough to maintain the conductance of the waveguide column  110  at a low enough value that the waveguide column  110  acts as a capacitor rather than a conductor when voltage is applied to the first and second contact layers  130 A,  130 B. For example, in various embodiments, the width w of the waveguide column  110  may be 0.8 microns or less and the waveguide  100  may be a functional PIN junction. For example,  FIGS. 3A and 3B  show plots of dopant concentrations of a contact layer  130 A,  130 B and an adjacent portion of waveguide column  110 . 
     Example Modulator 
       FIG. 2  illustrates a cross-section of a portion of an example modulator  200  comprising a waveguide  100 . For example, the modulator  200  may be an FK effect modulator, such as an FK effect electro-absorption modulator. In an example embodiment, the modulator  200  is configured for performing multiplexing and demultiplexing in accordance with wavelength division multiplexing (WDM), such as coarse WDM (CWDM) in the wavelength range of 1260-1670 nm. For example, the modulator  200  may be integrated with a laser diode, possibly on the same chip and/or substrate, to form a data transmitter and/or transistor in the form of a photonic integrated circuit. 
     The modulator  200  comprises a substrate  105 . For example, the substrate  105  may be a silicon substrate  150  with a buried oxide layer  140  formed within the silicon substrate  150 . A second layer of silicon  120  may be disposed between the buried oxide layer  140  and the waveguide column  110 . The waveguide column  110  extends outward from the substrate  150 . The first contact layer  130 A is disposed and/or deposited on the first side  112  of the waveguide column  110  and the second contact layer  130 B is disposed and/or deposited on the second side  114  of the waveguide column  110 . In various embodiments, the first contact layer  130 A comprises poly-si, poly-ge, an amorphous composition, and/or the like doped with a P-type dopant and the second contact layer  130 B comprises poly-si, poly-ge, an amorphous composition, and/or the like doped with an N-type dopant. 
     An insulating layer  230  is deposited onto the waveguide  100 . For example, the insulating layer  230  may comprise silicon nitride (SiN). Contact openings  225  are etched into the insulating layer  230  and contacts  220 A,  220 B may be deposited into the contact openings  225 . A first contact  220 A may be deposited into one of the contact openings  225  such that the first contact is in electrical communication with the first contact layer  130 A and the second contact  220 B may be deposited into one of the contact openings  225  such that the second contact is in electrical communication with the second contact layer  130 B. 
     A heater  240  may be deposited on the insulating layer  230  (e.g., adjacent the second side  114  and/or second contact layer  130 B). In an example embodiment, depositing the heater  240  may comprise sputtering and/or lithographical processes. In various embodiments, the heater  240  comprises titanium nitride (TiN), tungsten (W), tantalum (Ta), tantalum nitride (TaN), and/or the like. In various embodiments, the heater  240  may be configured in electrical communication with a voltage and/or current source. For example, the heater  240  may be configured to receive a voltage and/or current signal and generate heat (e.g., via resistive means) based thereon. For example, the heater  240  may be used to increase the temperature of one or more components of the modulator  200  and/or waveguide  100  to a desired operating temperature. 
     In various embodiments, an oxide layer  250  may be deposited onto the insulating layer  230  and heater  240 . For example, the oxide layer  250  may comprise thermal oxide, chemical vapor deposit oxide, tetraethyl orthosilicate (TEOS), and/or the like. In an example embodiment, a radiator  210  may be embedded within the oxide layer  250 . In an example embodiment, the radiator  210  may be formed via sputtering and/or metal lithography processes. In an example embodiment, the radiator  210  comprises aluminum (Al), titanium (Ti), and/or the like. In an example embodiment, the radiator  210  comprises an aluminum alloy, such as AlSiCu. In various embodiments, the radiator  210  may act as a heat sink and/or dissipative element to receive and/or dissipate excess heat generated through operation of the modulator  200  and/or waveguide  100 . In an example embodiment, the modulator  200  further comprises a second insulating layer  230  deposited on the oxide layer  250 . 
     As illustrated in  FIG. 5 , due to the small width of the waveguide column  110  (e.g., in the range of 0.4 to 0.9 microns in various embodiments; less than 0.8 microns, in various embodiments; and/or approximately 0.6 microns, in an example embodiment), the transmission loss of the waveguide  100  (and thus the modulator  200 ) is significantly smaller than conventional FK effect modulators (e.g., having waveguide widths of about 1 micron). Thus, the modulator  200  can be operated using lower voltages and/or lower power consumption than conventional FK effect modulators. Moreover, the smaller width of the waveguide column  110  (e.g., in the range of 0.4 to 0.9 microns in various embodiments; less than 0.8 microns, in various embodiments; and/or approximately 0.6 microns, in an example embodiment) enables the waveguide  100  to provide higher bandwidth transmission compared to conventional FK effect modulator waveguides. Additionally, as the FK effect modulator extinction ratio is proportional to the applied voltage divided by the waveguide width, the waveguide  100  provides a larger extinction ratio than conventional FK effect modulator waveguides. Therefore, various embodiments of the modulator  200  comprising a waveguide  100  comprising a thin waveguide column  110  (e.g., with width win the range of 0.4 to 0.9 microns in various embodiments; less than 0.8 microns, in various embodiments; and/or approximately 0.6 microns, in an example embodiment) and doped contact layers  130 A, B provide an improvement over conventional FK effect modulators. 
     Example Method of Fabrication 
       FIG. 4  provides a flowchart illustrating processes, procedures, operations, and/or the like for fabricating the waveguide  100  of a modulator  200 . Starting at step/operation  402 , waveguide material  116  is deposited onto a substrate  105 . For example, the substrate  105  may be a silicon substrate  150  having a buried oxide layer  140  formed therein and a second silicon layer  120  between the buried oxide layer  140  and the deposited waveguide material  116 . In an example embodiment, the waveguide material  116  comprises undoped GeSi. 
     At step/operation  404 , the waveguide material  116  is etched to form a waveguide column  110 . For example, the waveguide material  116  may be etched using a mask, resist layer, and/or the like to form a waveguide column having a width w that is less than one micron. In an example embodiment, the waveguide material  116  is etched to form a waveguide column  110  using a lithography etching technique. In an example embodiment, etching the waveguide material  116  includes etching the second layer of silicon  120  adjacent the waveguide column  110  such that the surface of the buried oxide layer  140  is exposed adjacent the waveguide column  110 , as shown in  FIG. 1 . 
       FIG. 5  illustrates the transmission loss of a waveguide  100  as a function of the width w of the waveguide column for four example waveguide column  110  heights (indicated as hGeSiSlab in  FIG. 5 ) for an example embodiment having GeSi as the waveguide material. As shown in  FIG. 5 , for waveguide columns  110  having heights greater than 0.2 microns (e.g., in the 0.2-0.5 micron range) there is a steep increase in transmission loss as a function of the width w of the waveguide column  110  for widths win the range of 0.5 to 0.8 microns. For example, for a waveguide column  110  having a height h of 0.3 microns, the transmission loss increases steeply as the width w of the waveguide column  110  increases to 0.6 microns. Thus, as illustrated in  FIG. 5 , forming a waveguide column  110  with a sufficiently small width w is enables a low enough transmission loss for the waveguide  100  for the modulator  200  to be operable at high bandwidth. However, as described above, such reduction of the width w of the waveguide column  110  does not allow for the conventional doping of the waveguide column  110  itself, as the N-type and P-type dopant concentrations overlap in a central portion of the waveguide column  110  causing the conductance of the waveguide  100  to be too high such that the modulator  200  does not function as an FK effect modulator. Various embodiments of the present invention provide solutions to these technical problems. 
     Returning to  FIG. 4 , at step/operation  406 , the first and second contact layers  130 A,  130 B may be deposited on to the first and second sides  112 ,  114 , respectively, of the waveguide column  110 . In an example embodiment, the contact layer material is deposited onto the waveguide column  110  and the exposed buried oxide layer  140  adjacent the waveguide column  110  using low pressure chemical vapor deposition. For example, contact layer material may be deposited on exposed surfaces of the waveguide column  110 , substrate  105 , and/or the like. The contact layer material may then be etched (e.g., using a lithography etching technique) to form the first and second contact layers  130 A,  130 B. Any resist layer or mask used in the etching process may then be removed. In an example embodiment, the contact layer material comprises poly-si, poly-ge, an amorphous composition, and/or the like. In various embodiments, the first and second contact layers  130 A,  130 B are in contact with the buried oxide layer  140  and the respective sides of the waveguide column  110 . For example, the first contact layer  130 A may extend out from the substrate  105  along the first side  112  of the waveguide column  110  and may extend along the substrate  105  away from the waveguide column  110  within a waveguide cavity of the modulator  200 . For example, the portion of the modulator  200  shown in  FIG. 2  may be the portion of the modulator  200  within the waveguide cavity. For example, the waveguide cavity may be bordered by other portions of the modulator  200 , such as an echelle grating disposed between the waveguide  100  and a laser cavity and/or laser diode facet. In another example, the waveguide cavity may be bordered by a mesa having a drive pad of the modulator  200  disposed thereon, and/or the like. Similarly, the second contact layer  130 B may extend out from the substrate  105  along the second side  114  of the waveguide column  110  and may extend along the substrate  105  away from the waveguide column  110  within a waveguide cavity of the modulator  200 . 
     At step/operation  408 , dopant is implanted and/or diffused into the contact layers. For example, a P-type dopant may be implanted and/or diffused into the first contact layer  130 A and an N-type dopant may be implanted and/or diffused into the second contact layer  130 B, or vice-versa. For example, as shown in  FIGS. 3A and 3B , the appropriate dopant may be implanted and/or diffused into the first and second contact layers such that the concentration of the dopant within the corresponding contact layer is in the range of approximately 1×10 16  to 1×10 21  per cubic centimeter. The dopant may also diffuse into a portion of the waveguide material  116  disposed adjacent the corresponding contact layer. In an example embodiment, the concentration of dopant present in the waveguide material  116  falls below 1×10 15  per cubic centimeter within approximately 2 microns of the corresponding side of the waveguide column  110 . Thus, a central portion of the waveguide column  110  comprises substantially undoped waveguide material  116 . 
       FIG. 6  provides a band diagram  600  showing the electronic band structure across a cross section of the waveguide  100  taken in a plane substantially perpendicular to the transmission axis  105  of the waveguide  115 . Both the conduction band  610  and the valence band  620  reduce in energy across the waveguide column  110  from the first contact layer  130 A to the second contact layer  130 B. The small barrier  622  to the valence band at the interface between the first contact layer  130 A and the waveguide column  110  enables low to moderate energy holes (e.g., 50 meV holes) to tunnel through the barrier  622 . As should be understood by a person of skill in the art, the electronic band structure shown in  FIG. 6  is a result of the doping of the first contact layer  130 A and the second contact layer  130 B. 
     Continuing with  FIG. 4 , at step/operation  410 , an insulating layer  230  is deposited. For example, an insulating layer  230  may be deposited onto the waveguide column  110 , first and second contact layers  130 A,  130 B, and/or the like, as shown in  FIG. 2 . In an example embodiment, the insulating layer  230  comprises SiN. In an example embodiment, the insulating layer  230  is deposited to a thickness in the range of 200-350 nanometers. 
     At step/operation  412 , the heater  240  is formed. For example, heater material may be sputtered and/or deposited onto the exposed surfaces of the waveguide column  110 , first and second contact layers  130 A,  130 B, substrate  105 , and/or the like. The heater material may then be etched (e.g., using a dry etch) to form the heater  240 . In an example embodiment, the heater material comprises TiN, W, Ta, TaN, and/or the like. In various embodiments, a via may be formed and/or opened for use in placing the heater  240  into electrical communication with a voltage/current source during operation of the modulator  200 . 
     At step/operation  414 , contact openings  225  are etched and contacts  220  are deposited into the contact openings  225  and patterned. In an example embodiment, a portion of the oxide layer  250  is deposited prior to the etching of the contact openings  225 . For example, in an example embodiment, an oxide layer  250  is deposited to a thickness of 450-550 nm. The oxide layer and insulating layer  230  may then be etched to form the contact openings  225 . For example, a lithography etching process may be used to etch the contact openings  225 . In various embodiments, the contact openings  225  are configured to, when the contacts  220  are deposited into the contact openings, place the contacts into electrical communication and/or contact with a corresponding one of the first and second contact layer  130 A,  130 B. In various embodiments, the contacts  220  are formed by depositing a conductive and/or metal material such as aluminum, an aluminum alloy (e.g., AlSiCu), titanium, and/or the like. 
     At step/operation  416 , when a radiator  210  is be present in the modulator  200 , the radiator is formed and any remaining portion of the oxide layer  250  is deposited. In an example embodiment, the radiator  210  is formed during the same metal deposition and etching as the contacts. For example, the radiator may be formed by depositing a conductive and/or metal material such as aluminum, an aluminum alloy (e.g., AlSiCu), titanium, and/or the like and then etching the deposited conductive and/or metal material. The remaining portion of the oxide layer  250  may be deposited after the forming of the radiator  240 . In various embodiments, the oxide layer  250  comprises thermal oxide, chemical vapor deposit oxide, tetraethyl orthosilicate (TEOS), and/or the like. 
     At step/operation  418 , another insulating layer  230  is deposited on the exposed surface of the oxide layer  250 . In an example embodiment, the insulating layer  230  comprises SiN. As should be understood, additional steps may be performed as part of the process to form the modulator  200  on the substrate  105 . For example, the modulator  200  may further comprise a silicon waveguide, laser grating, laser cavity, an alignment mark, an echelle grating, and/or other components which may be formed at least in part simultaneously to the formation of the waveguide  100 . 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.