P-CHANNEL GALLIUM NITRIDE TRANSISTORS

TECHNICAL FIELD

Embodiments of the present description generally relate to the field of

microelectronic devices, and, more particularly, to forming CMOS (Complementary Metal Oxide Semiconductor) circuits and structures using both n-channel and p-channel gallium nitride transistors.

BACKGROUND

The microelectronics industry is continually striving to produce ever faster and smaller microelectronic packages for use in various electronic products, including, but not limited to, computer server products and portable products, such as laptop/netbook computers, electronic tablets, smart phones, digital cameras, and the like. One route to achieve these goals is the fabrication of System-on-Chip (SoC) devices, wherein all of the components of an electronic system are fabricated on a single chip. In such SoC devices, power management integrated circuits (PMIC) and radio frequency integrated circuits (RFIC) are critical functional blocks, and are as important as logic and memory integrated circuits in determining the power efficiency and the form factor of such SoC devices. Therefore, there is an ongoing effort to scaled down and/or improve the efficiency of PMICs and RFICs, as well as logic and memory integrated circuits, for SoC devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. It is understood that the accompanying drawings depict only several embodiments in accordance with the present disclosure and are, therefore, not to be considered limiting of its scope. The disclosure will be described with additional specificity and detail through use of the accompanying drawings, such that the advantages of the present disclosure can be more readily ascertained, in which: FIG. 1 is a schematic of a gallium nitride circuit, as known in the art.

FIG. 2 is a schematic of a gallium nitride circuit, according to an embodiment of the present description.

FIGs. 3-9 are side cross-section views of the fabrication of a gallium nitride circuit structure, according to one embodiment of the present description.

FIG. 10 is a side cross-section view of a gallium nitride circuit structure, according to another embodiment of the present description.

FIGs. 11 and 12 are side cross-section views of a gallium nitride circuit structure, according to still another embodiment of the present description.

FIG. 13 is a side cross-section view of a gallium nitride circuit structure, according to a further embodiment of the present description.

FIG. 14 is a side cross-section view of a gallium nitride circuit structure, according to another embodiment of the present description. FIG. 15 is a flow chart of a process of fabricating a gallium nitride circuit structure, according to an embodiment of the present description.

FIG. 16 illustrates a computing device in accordance with one implementation of the present description.

DESCRIPTION OF EMBODIMENTS In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the claimed subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the subject matter. It is to be understood that the various embodiments, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the claimed subject matter. References within this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present description. Therefore, the use of the phrase "one embodiment" or "in an embodiment" does not necessarily refer to the same embodiment. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the claimed subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the subject matter is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the appended claims are entitled. In the drawings, like numerals refer to the same or similar elements or functionality throughout the several views, and that elements depicted therein are not necessarily to scale with one another, rather individual elements may be enlarged or reduced in order to more easily comprehend the elements in the context of the present description.

The terms "over", "to", "between" and "on" as used herein may refer to a relative position of one layer with respect to other layers. One layer "over" or "on" another layer or bonded "to" another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer "between" layers may be directly in contact with the layers or may have one or more intervening layers.

Embodiments of the present description related to CMOS circuits formed using p- channel gallium nitride transistors and n-channel gallium nitride transistors, wherein both the p- channel gallium nitride transistors and the n-channel gallium nitride transistors are formed on a single layered structure comprising a polarization layer deposited on a first gallium nitride layer and a second gallium nitride layer deposited on the polarization layer. Having both n-channel gallium nitride transistors and p-channel gallium nitride transistors on the same layer structure may enable "all gallium nitride transistor" implementations of circuits including logic, digital, and analog circuitries spanning low supply voltages to high supply voltages.

Gallium nitride has a relatively wide bandgap (e.g. about 3.4 eV), when compared to the bandgap of silicon (about 1.1 eV). Therefore, gallium nitride transistors may withstand large electric fields, such as applied voltages, drain voltage, and the like, before suffering breakdown, when compared to a silicon based transistor of similar dimensions. This also enables the gallium nitride transistors to be scaled to even smaller physical dimensions when operating at the same supply voltage to a comparable silicon based transistor. Gallium nitride has a high electronic mobility (e.g. about 1000cm ² /Vs) which makes it a very good material for the formation of an n-channel gallium nitride transistor, as an n- channel gallium nitride transistor employs a 2D electron gas as its transportation channel.

Gallium nitride has a hole mobility (zero strain) which is an order of magnitude weaker (e.g. about 100cm ² /Vs) than its electronic mobility. However, it still is a good material for the formation of a p-channel gallium nitride transistor, as a p-channel gallium nitride transistor employs a 2D hole gas as its transportation channel, since is hole mobility is still comparable to unstrained silicon hole mobility.

As shown in FIG. 1, a gallium nitride circuit 100, such as a logic or control circuit, is commonly implemented using a depletion mode n-channel gallium nitride transistor in conjunction with an enhancement mode n-channel gallium nitride transistor. However, steady- state leakage may be high in such circuits due to the depletion mode n-channel nitride transistor acting as a resistor, as will be understood to those skilled in the art. A CMOS gallium nitride circuit 200 of embodiments of the present description may comprise the depletion mode n- channel gallium nitride transistor of FIG. 1 being replaced with a p-channel gallium nitride transistor, as shown in FIG. 2.

FIGs. 3-9 illustrate a method of fabricating a gallium nitride circuit structure, according to one embodiment of the present description. As shown in FIG. 3, a layered structure 210 may be formed with a polarization layer 204 deposited on a first gallium nitride layer 202 and a second gallium nitride layer 206 deposited on the polarization layer 204 with the polarization layer 204 comprising aluminum gallium nitride, aluminum indium nitride, aluminum indium gallium nitride, aluminum nitride, and like materials. The polarization layer 204 may have ternary crystal structure which forms a 2D electron gas 212 (designated generically with negative "-" symbols) in the first gallium nitride layer 202 due to the formation of an abrupt hetero-junction interface 214 between the first gallium nitride layer 202 and the polarization layer 204 through spontaneous and piezoelectric polarization, as will be understood to those skilled in the art. In a like manner, the deposition of the second gallium nitride layer 206 on the polarization layer 204 forms a 2D hole gas 216 (designated generically with positive "+" symbols) within the second gallium nitride layer 206 proximate an interface 218 between the second gallium nitride layer 206 and the polarization layer 204. The 2D hole gas 216 forms due to the formation of the 2D electron gas 212 which shifts the polarization layer 204 positive (labeled as "σ+") near the first gallium nitride layer 202, thereby shifting the polarization layer 204 negative (labeled as "σ-") near the second gallium nitride layer 206. Very high charge densities up to about 2E13 per cm ² can be formed by such mechanisms, without the use of impurity dopants, which allows for high mobilities to be preserved, as will be understood to those skilled in the art. The polarization layer 204 may also act as electrical insulation between the 2D electron gas 212 and the 2D hole gas 216, which is achieved by both conduction and valence bonds offsets, as well as, by the built-in polarization field, as will be understood to those skilled in the art.

As shown in FIG. 4, the layered structure 210 formed with a polarization layer 204 deposited on a first gallium nitride layer 202 and a second gallium nitride layer 206 deposited on the polarization layer 204 is illustrated with the polarization layer 204 being indium gallium nitride and like materials. When the polarization layer 204 is indium gallium nitride and like materials, the 2D electron gas 212 forms in the polarization layer 204, as will be understood to those skilled in the art. In a like manner, the deposition of the second gallium nitride layer 206 on the polarization layer 204 forms the 2D hole gas 216 within the polarization layer 204. Again, the polarization layer 204 may also act as electrical insulation between the 2D electron gas 212 and the 2D hole gas 216, which, in the embodiment of the polarization layer 204 being indium gallium nitride and like materials, is achieved by the built-in polarization field alone. Additionally, although the 2D electron gas 212 and the 2D hole gas 216 are formed in different locations in this embodiment from that shown in FIG. 3, the same results and mechanisms are achieved. Thus, for the sake of conciseness and brevity, FIGs. 5-9 will illustrate the 2D electron gas 212 and the 2D hole gas 216 locations of FIG. 3.

As shown in FIG. 5, a portion 220 of the layered structure 210 designated for the subsequent formation of a p-channel gallium nitride transistor may be patterned with a hardmask 222, such as silicon nitride. As shown in FIG. 6, the second gallium nitride layer 206 in the unmasked portion 224 designated for the subsequent formation of an n-channel gallium nitride circuit structure may be remove, such as by etching, and a portion of the polarization layer 204 may be removed, such as by etching, to form a polarization layer intermediate surface 226, such that the polarization layer intermediate surface 226, from a planar standpoint, is between the interface 214 between the first gallium nitride layer 202 and the polarization layer 204 and the remaining interface 218 between the second gallium nitride layer 206 and the polarization layer 204. In one embodiment, a thickness T between the intermediate surface 226 and the interface 214 between the first gallium nitride layer 202 and the polarization layer 204 may be less than about 20nm. As illustrated in FIG. 7, an n-channel gallium nitride transistor 230 may be formed in the portion 224 after a second hardmask 228 is patterned on the portion 220 designated for the subsequent formation of a p-channel gallium nitride circuit structure. The n-channel gallium nitride transistor 230 may comprise opposing source/drain structures 232 (one being a source structure and the other being a drain structure) with a gate region 234 defined therebetween. A gate dielectric 236 may be formed in the gate region 234 and a gate electrode 238 may be formed on the gate dielectric 236, such that the gate dielectric 236 electrically isolates the gate electrode 238. In one embodiment, the n-channel gallium nitride transistor 230 is an

enhancement mode transistor. Thus, as shown, a portion of the polarization layer 204 may be removed to disrupt the 2D electron gas 212, such that it does not extend through the gate length L _g of the n-channel gallium nitride transistor 230 to achieve enhancement mode operation.

In one embodiment, the source/drain structures 232 may be formed by forming by patterning a hardmask (not shown), such as silicon nitride, silicon oxide, and the like, on the polarization layer intermediate surface and recesses (not shown) may be formed to extend through the polarization layer 204 and into the first gallium nitride layer 202, by any known technique, such as etching. In one embodiment, the recesses (not shown) may be formed with a plasma etch in a chlorine based chemistry. The source/drain structures 232, such as comprising N+ indium gallium nitride, N+ gallium nitride, N+ indium nitride, and any graded combination thereof, may be formed in the recesses (not shown) by epitaxial regrowth from the first gallium nitride layer 202. In one embodiment, the regrowth process may comprise epitaxial crystal growth techniques, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). After the formation of the source/drain structures 232, metallizations 242 may be formed on the source/drain structures 232.

The gate dielectric 236 may be formed from any well-known gate dielectric material, including but not limited to silicon dioxide (S1O ₂ ), silicon oxynitride (SiO _x N _y ), silicon nitride

(S1 ₃ N ₄ ), and high-k dielectric materials such as hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, tantalum silicon oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. The gate dielectric 236 can be formed by well-known techniques, such as chemical vapor deposition ("CVD"), physical vapor deposition ("PVD"), and atomic layer deposition ("ALD"). The gate electrode 238 can be formed of any suitable gate electrode material. In an embodiment of the present disclosure, the gate electrode 238 may be formed from materials that include, but are not limited to, polysilicon, tungsten, ruthenium, palladium, platinum, cobalt, nickel, hafnium, zirconium, titanium, tantalum, aluminum, titanium carbide, zirconium carbide, tantalum carbide, hafnium carbide, aluminum carbide, other metal carbides, metal nitrides, and metal oxides. The gate electrode 238 can be formed by well-known techniques, such as by blanket depositing a gate electrode material and then patterning the gate electrode material with well-known photolithography and etching techniques, as will be understood to those skilled in the art.

As illustrated in FIG. 8, an p-channel gallium nitride transistor 250 may be formed in the portion 226 after a second hardmask 228 (see FIG. 5) has removed and a third hardmask 244 is patterned over the n-channel gallium nitride transistor 230. The p-channel gallium nitride transistor 250 may comprise opposing source/drain structures 252 (one being a source structure and the other being a drain structure) with a gate region 254 defined therebetween and a p-doped gallium nitride layer 262 may be optionally formed over the gate region 254 to improve access resistance, as will be understood to those skilled in the art. A gate dielectric 256 may be formed in the gate region 254 and a gate electrode 258 may be formed on the gate dielectric 256 such that the gate dielectric 256 electrically isolates the gate electrode 258. In one embodiment, the p- channel gallium nitride transistor 250 is an enhancement mode transistor. Thus, as shown, a portion of the p-doped gallium nitride layer 262 may be removed (if present) and a recess 266 may be formed in the second gallium nitride layer 206, such that the gate dielectric 256 may be at least partially embedded in the second gallium nitride layer 206. As will be understood to those skilled in the art, the formation of the recess 266 and embedding the gate dielectric 256 may disrupt a portion of the 2D hole gas 216, such that it does not extend through the gate length L _g of the p-channel gallium nitride transistor 250 to achieve enhancement mode operation.

Furthermore, at least partially embedding the gate dielectric 256 may place the gate

dielectric 256 and gate electronic 258 closer to the 2D hole gas 216 to enable a thin equivalent gate dielectric thickness for greater drive and electrostatics control, as will be understood to those skilled in the art.

In one embodiment, the source/drain structures 252 may be formed by forming by patterning a hardmask (not shown), such as silicon nitride, silicon oxide, and the like, on the polarization layer intermediate surface and recesses (not shown) may be formed to extend into the second gallium nitride layer 206, by any known technique, such as etching. In one embodiment, the recesses (not shown) may be formed with a plasma etch in a chlorine based chemistry. The source/drain structures 252, such as comprising P+ indium gallium nitride, P+ gallium nitride, P+ indium nitride, and any graded combination thereof, may be formed in the recesses (not shown) by epitaxial regrowth from the second gallium nitride layer 206. In one embodiment, the regrowth process may comprise epitaxial crystal growth techniques, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The regrowth of the source/drain structures 252 for the p-channel gallium nitride transistor 250 may induce a uniaxial compressive strain which may improve hole mobility and improve contact resistance. After the formation of the source/drain structures 252, metallizations 264 may be formed on the source/drain structures 252.

The gate dielectric 256 may be formed from any well-known gate dielectric material, including but not limited to silicon dioxide (S1O ₂ ), silicon oxynitride (SiO _x N _y ), silicon nitride (S1 ₃ N ₄ ), and high-k dielectric materials such as hafnium oxide, hafnium silicon oxide, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, tantalum silicon oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. The gate dielectric 256 can be formed by well-known techniques, such as chemical vapor deposition ("CVD"), physical vapor deposition ("PVD"), and atomic layer deposition ("ALD"). The gate electrode 258 can be formed of any suitable gate electrode material. In an embodiment of the present disclosure, the gate electrode 258 may be formed from materials that include, but are not limited to, polysilicon, tungsten, ruthenium, palladium, platinum, cobalt, nickel, hafnium, zirconium, titanium, tantalum, aluminum, titanium carbide, zirconium carbide, tantalum carbide, hafnium carbide, aluminum carbide, other metal carbides, metal nitrides, and metal oxides. The gate electrode 258 can be formed by well-known techniques, such as by blanket depositing a gate electrode material and then patterning the gate electrode material with well-known photolithography and etching techniques, as will be understood to those skilled in the art.

As shown in FIG. 9, the third hardmask 244 (see FIG. 8) may be removed and at least one interlayer dielectric layer 272 may be deposited over the n-channel gallium nitride transistor 230 and the p-channel gallium nitride transistor 250. N-channel source/drain contacts 274 may be formed through the interlayer dielectric layer 272 to contact the

metalizations 242 of the n-channel gallium nitride transistor source/drain structures 232 and p- channel source/drain contacts 276 may be formed through the interlayer dielectric layer 272 to contact the metalizations 264 of the p-channel gallium nitride transistor source/drain

structures 252. An n-channel transistor gate contact 282 may be formed through the interlayer dielectric layer 272 to contact the gate electrode 236 and a p-channel transistor gate contact 284 may be formed through the interlayer dielectric layer 272 to contact the gate electrode 256. As further shown in FIG. 9, conductive traces 286 may be formed to appropriately connect components of the n-channel gallium nitride transistor 230 and the p-channel gallium nitride transistor 250, as will be understood to those skilled in the art, thereby forming the CMOS gallium nitride circuit structure 200. The materials and processes used for forming the interlayer dielectric layer 272, the n-channel source/drain contacts 274, the p-channel source/drain contacts 276, the n-channel transistor gate contact 282, the p-channel transistor gate contact 284, and the conductive traces 286 are well known to those skilled in the art, and for the sake of brevity and conciseness will not be described or illustrated herein.

As will be understood to those skilled in the art, in order to minimize interconnect losses, and achieve smaller footprint, as well as other scaling advantages known in the art, the n- channel gallium nitride transistor 230 and the p-channel gallium nitride transistor 250 should be in close proximity to one another. In one embodiment, the n-channel gallium nitride

transistor 230 and the p-channel gallium nitride transistor 250 may be separated by a single gate pitch; for example, less than about lOOnm.

It is understood that the components of the n-channel gallium nitride transistor 230 and the p-channel gallium nitride transistor 250 need not be fabricated separately, rather the steps of masking, unmasking, and re- masking may be undertaken to simultaneously form components for both the n-channel gallium nitride transistor 230 and the p-channel gallium nitride transistor 250, including, but not limited to, the gate dielectrics 236/256, the gate

electrodes 238/258, and the like, depending on process demands, such as temperature.

As shown in FIG. 10, in another embodiment of the present description, the first gallium nitride layer 202 may be formed on a strain material layer 290 having a lattice structure smaller than that of the first gallium nitride layer 202, which may induce a biaxial compressive strain to improve the mobility of the 2D hole gas 216 mobility. The strain material layer 290 may include, but is not limited to, aluminum nitride, aluminum indium nitride, aluminum gallium nitride, and the like.

In another embodiment of the present description, as shown in FIG. 1 1, the p-channel gallium nitride transistor 250 may be stacked on top of the n-channel gallium nitride

transistor 230, so that a common gate 302 could be shared to form a stacked CMOS gallium nitride circuit structure 300. The stacked CMOS gallium nitride circuit structure 300 may have tighter scale integration than the CMOS gallium nitride circuit structure 200 embodiments shown in FIGs. 3-10. As shown in FIG. 12, which is a cross-sectional view along line 12-12 of FIG. 11, the common gate 302 may comprise a gate dielectric 304 surrounding at least one stack 310 comprising the first gallium nitride layer 202, the second gallium nitride layer 206, and the polarization layer 204 therebetween, and a gate electrode 306 surrounding the gate

dielectric 304. An under-fill dielectric 312 may be disposed below the common gate 302 for electrical isolation thereof. In one embodiment, the efficiency of the depletion the 2D electron gas 212 (see FIG. 1 1) and the 2D hole gas 216 (see FIG. 11) may be improved by reducing the width W of the stack 310 to less than about 20nm. Thus, as shown, more than one stack 310 may be fabricated for each CMOS gallium nitride circuit structure 300 to achieve efficient operation thereof. The materials and processes used for forming the CMOS gallium nitride circuit structure 300 illustrated in FIG. 1 1 and 12 are well known to those skilled in the art, and for the sake of brevity and conciseness will not be described or illustrated herein.

In another embodiment, the layered structure 210 of FIG. 3 may be flipped and fabrication of the n-channel gallium nitride transistor components and the p-channel gallium nitride transistor components reversed to form the CMOS gallium nitride circuit structure 320 of FIG. 13 or the CMOS gallium nitride circuit structure 330 of FIG. 14.

As will be understood to those skilled in the art, embodiments of the present description may not only be relevant to all system-on-chip products, such as those that will require direct battery high voltage switching transistors such as for DC-to-DC conversion, but may also be applicable in the fabrication of control and drive circuitries, as well as logic peripheries, e.g. microprocessors, static random access memory, and communication processors.

FIG. 15 is a flow chart of a process 400 of fabricating a CMOS circuit structure according to an embodiment of the present description. As set forth in block 402, a layer structure may be formed by depositing a polarization layer on a first gallium nitride layer and depositing a second gallium nitride layer on the polarization layer. A portion of one of the first gallium nitride layer and the second gallium nitride layer and a portion of the polarization layer may be removed to form a polarization layer intermediate surface, as set forth in block 404. As set forth in block 406, one of a p-channel transistor and an n-channel transistor may be formed on the polarization intermediate surface. The other of the p-channel transistor and the n-channel transistor may be formed on the remaining portion of one of the the first gallium nitride layer and the second gallium nitride layer, as set forth in block 408. FIG. 16 illustrates a computing device 500 in accordance with one implementation of the present description. The computing device 500 houses a board 502. The board 502 may include a number of components, including but not limited to a processor 504 and at least one communication chip 506A, 506B. The processor 504 is physically and electrically coupled to the board 502. In some implementations the at least one communication chip 506A, 506B is also physically and electrically coupled to the board 502. In further implementations, the communication chip 506A, 506B is part of the processor 504.

Depending on its applications, the computing device 500 may include other components that may or may not be physically and electrically coupled to the board 502. These other components include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth).

The communication chip 506A, 506B enables wireless communications for the transfer of data to and from the computing device 500. The term "wireless" and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip 206 may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.1 1 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device 500 may include a plurality of

communication chips 306A, 306B. For instance, a first communication chip 506A may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip 506B may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.

The processor 504 of the computing device 500 may include CMOS circuits formed -channel gallium nitride transistors and n-channel gallium nitride transistors, as described above. The term "processor" may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory. Furthermore, the communication chip 506A, 506B may include CMOS circuits formed from p-channel gallium nitride transistors and n-channel gallium nitride transistors.

In various implementations, the computing device 500 may be a laptop, a netbook, a notebook, an ultrabook, a smartphone, a tablet, a personal digital assistant (PDA), an ultra mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set- top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device 300 may be any other electronic device that processes data.

It is understood that the subject matter of the present description is not necessarily limited to specific applications illustrated in FIGs. 1-16. The subject matter may be applied to other microelectronic device and assembly applications, as well as any other appropriate transistor applications, as will be understood to those skilled in the art.

The following examples pertain to further embodiments, wherein Example 1 is a CMOS circuit structure comprising a layered structure including a first gallium nitride layer and a second gallium nitride layer separated by a polarization layer, wherein the layered structure includes an polarization layer intermediate surface; one of a p-channel transistor and an n- channel transistor formed proximate the polarization layer intermediate surface; and the other of the p-channel transistor and an n-channel transistor formed on one of the first gallium nitride layer and the second gallium nitride layer.

In Example 2, the subject matter of Example 1 can optionally include the p-channel transistor being an enhancement mode transistor. In Example 3, the subject matter of any of Examples 1 and 2 can optionally include the n-channel transistor being an enhancement mode transistor.

In Example 4, the subject matter of any of Examples 1 to 3 can optionally include the polarization layer being selected from the group consisting of aluminum gallium nitride, aluminum indium nitride, indium gallium nitride, aluminum nitride, and aluminum gallium nitride. In Example 5, the subject matter of any of Examples 1 to 4 can optionally include a strain material layer, wherein the first gallium nitride layer abuts the strain material layer.

In Example 6, the subject matter of Example 5 can optionally include the strain material layer being selected from the group consisting of aluminum nitride, aluminum indium nitride, aluminum gallium nitride, and aluminum indium gallium nitride.

In Example 7, the subject matter of any of Example 1 to 6 can optionally include the layered structure including a 2D electron gas within the first gallium nitride layer proximate the polarization layer and a 2D hole gas within the second gallium nitride layer; and wherein the n- channel transistor is formed proximate the polarization layer intermediate surface and the p- channel transistor is formed proximate the second gallium nitride layer.

In Example 8, the subject matter of Example 7 can optionally include a recess in the second gallium nitride layer disrupting a portion of the 2D hole gas.

In Example 9, the subject matter of any of Examples 1 to 6 can optionally include the layered structure including a 2D electron gas within the first gallium nitride layer proximate the polarization layer and a 2D hole gas within the second gallium nitride layer; and wherein the p- channel transistor is formed proximate the polarization layer intermediate surface and the n- channel transistor is formed proximate the first gallium nitride layer.

In Example 10, the subject matter of Example 9 can optionally include a recess in the first gallium nitride layer disrupting a portion of the 2D electron gas. The following examples pertain to further embodiments, wherein Example 1 1 is a method of fabricating a CMOS circuit structure comprising forming a layered structure comprising depositing a polarization layer on a first gallium nitride layer and depositing a second gallium nitride layer on the polarization layer; removing a portion of one of the first gallium nitride layer and the second gallium nitride layer and a portion of the polarization layer to form a polarization layer intermediate surface; forming one of a p-channel transistor and an n-channel transistor on the polarization layer intermediate surface; and forming the other of the p-channel transistor and the n-channel transistor on a remaining portion of one of the first gallium nitride layer and the second gallium nitride layer.

In Example 12, the subject matter of Example 1 1 can optionally include forming the p-channel transistor comprising forming a p-channel enhancement mode transistor. In Example 13, the subject matter of any of Examples 1 1 to 12 can optionally include forming the n-channel transistor comprising forming an n-channel enhancement mode transistor.

In Example 14, the subject matter of any of Examples 1 1 to 13 can optionally include depositing the polarization layer comprising depositing a material selected from the group consisting of aluminum gallium nitride, aluminum indium nitride, indium gallium nitride, aluminum nitride, and aluminum indium gallium nitride.

In Example 15, the subject matter of any of Examples 1 1 to 14 can optionally include depositing the first gallium nitride layer on a strain material layer.

In Example 16, the subject matter of Example 15 can optionally include the strain material layer being selected from the group consisting of aluminum nitride, aluminum indium nitride, aluminum gallium nitride, and aluminum indium gallium nitride.

In Example 17, the subject matter of any of Example 1 1 to 16 can optionally include forming the layered structure comprising forming a 2D electron gas within the first gallium nitride layer proximate the polarization layer and forming a 2D hole gas within the second gallium nitride layer; and wherein the n-channel transistor is formed proximate the polarization layer intermediate surface and the p-channel transistor is formed proximate the second gallium nitride layer.

In Example 18, the subject matter of Example 17 can optionally include forming a recess in the second gallium nitride layer to disrupt a portion of the 2D hole gas.

In Example 19, the subject matter of Example 1 1 to 16 can optionally include forming the layered structure includes forming a 2D electron gas within the first gallium nitride layer proximate the polarization layer and forming a 2D hole gas within the second gallium nitride layer; and wherein the p-channel transistor is formed proximate the polarization layer intermediate surface and the n-channel transistor is formed proximate the first gallium nitride layer.

In Example 20, the subject matter of Example 19 can optionally include forming a recess in the first gallium nitride layer to disrupt a portion of the 2D electron gas.

The following examples pertain to further embodiments, wherein Example 21 is an electronic system, comprising a board and a microelectronic device attached to the board, wherein the microelectronic device includes at least one CMOS circuit structure comprising a layered structure including a first gallium nitride layer and a second gallium nitride layer separated by a polarization layer, wherein the layered structure includes an polarization layer intermediate surface; one of a p-channel transistor and an n-channel transistor formed proximate the polarization layer intermediate surface; and the other of the p-channel transistor and an n- channel transistor formed on one of the first gallium nitride layer and the second gallium nitride layer.

In Example 22, the subject matter of Example 21 can optionally include the layered structure including a 2D electron gas within the first gallium nitride layer proximate the polarization layer and a 2D hole gas within the second gallium nitride layer; and wherein the n- channel transistor is formed proximate the polarization layer intermediate surface and the p- channel transistor is formed proximate the second gallium nitride layer.

In Example 23, the subject matter of Example 22 can optionally include a recess in the second gallium nitride layer disrupting a portion of the 2D hole gas. In Example 24, the subject matter of Example 21 can optionally the layered structure including a 2D electron gas within the first gallium nitride layer proximate the polarization layer and a 2D hole gas within the second gallium nitride layer; and wherein the p-channel transistor is formed proximate the polarization layer intermediate surface and the n-channel transistor is formed proximate the first gallium nitride layer. In Example 25, the subject matter of Example 24 can optionally include a recess in the first gallium nitride layer disrupting a portion of the 2D electron gas.

Having thus described in detail embodiments of the present description, it is understood that the present description defined by the appended claims is not to be limited by particular details set forth in the above description, as many apparent variations thereof are possible without departing from the spirit or scope thereof.