阅读说明：本技术 高电子迁移率晶体管esd保护结构 (High electron mobility transistor ESD protection structure ) 是由 M·艾曼·谢比卜 C·G·廖 于 2019-07-24 设计创作，主要内容包括：本发明公开了一种高电子迁移率晶体管ESD保护结构。多栅极高电子迁移率晶体管(HEMT)可以包括在漏极和源极之间的二维电子气(2DEG)沟道。第一栅极可以设置为邻近漏极和源极之间的2DEG沟道。当在第一栅极和源极之间施加的电压小于与第一栅极相关联的阈值电压时,第一栅极可以配置成耗尽邻近第一栅极的2DEG沟道中的多数载流子。可以在漏极和第一栅极之间、邻近2DEG沟道处设置第二栅极。第二栅极可以电耦合到漏极。当在第二栅极与第二栅极和第一栅极之间的2DEG沟道之间施加的电压小于与第二栅极相关联的阈值电压时,第二栅极可以配置成耗尽邻近第二栅极的2DEG沟道中的多数载流子。与第二栅极相关联的阈值电压可以等于或大于与第一栅极相关联的阈值电压。(The invention discloses an ESD protection structure of a high electron mobility transistor. A multi-gate very High Electron Mobility Transistor (HEMT) may include a two-dimensional electron gas (2DEG) channel between a drain and a source. The first gate may be disposed adjacent to the 2DEG channel between the drain and the source. The first gate can be configured to deplete majority carriers in a 2DEG channel adjacent the first gate when a voltage applied between the first gate and the source is less than a threshold voltage associated with the first gate. A second gate may be disposed between the drain and the first gate, adjacent the 2DEG channel. The second gate may be electrically coupled to the drain. The second gate can be configured to deplete majority carriers in a 2DEG channel adjacent the second gate when a voltage applied between the second gate and the 2DEG channel between the second gate and the first gate is less than a threshold voltage associated with the second gate. The threshold voltage associated with the second gate may be equal to or greater than the threshold voltage associated with the first gate.)

1. A device, comprising:

a wide band gap semiconductor layer;

a wider band gap semiconductor layer disposed on the wide band gap semiconductor layer to form a heterojunction, wherein a two-dimensional electron gas (2DEG) channel is present in the wide band gap semiconductor layer at a boundary adjacent to the wider band gap semiconductor layer;

a source electrode disposed on a first portion of the wider bandgap semiconductor layer;

a drain electrode disposed on a second portion of the wider bandgap semiconductor layer;

a first gate disposed on a third portion of the wider bandgap semiconductor layer between the source and the drain, wherein majority carriers in the 2DEG channel adjacent the first gate are depleted by the first gate when a potential voltage is less than a first threshold voltage applied between the first gate and the source;

a second gate disposed on a fourth portion of the wider bandgap semiconductor layer between the first gate and the drain and electrically coupled to the drain, wherein majority carriers in the 2DEG channel adjacent to the second gate are depleted by the second gate when a potential voltage is less than a second threshold voltage applied between the second gate and a fifth portion of the wider bandgap semiconductor layer, wherein the fifth portion is between the fourth portion and the third portion of the wider bandgap semiconductor layer; and the number of the first and second groups,

wherein the second threshold voltage is greater than or equal to the first threshold voltage.

2. The device of claim 1, wherein said wide bandgap semiconductor layer comprises an unintentionally doped semiconductor layer.

3. The device of claim 1, further comprising:

a third gate disposed on a fifth portion of the wider bandgap semiconductor layer between the first gate and the second gate and electrically coupled to a sixth portion of the wider bandgap semiconductor layer between the second gate and the third gate.

4. The device of claim 1, wherein the second threshold voltage is substantially equal to the first threshold voltage.

5. The device of claim 1, wherein the second threshold voltage is approximately greater than the first threshold voltage by a predetermined amount.

6. The device of claim 1, wherein:

the wide band gap semiconductor layer comprises a substantially intrinsic gallium nitride (GaN) layer;

the wider band gap semiconductor layer comprises an aluminum gallium nitride (AlGaN) layer; and

the first gate and the second gate comprise p-type doped gallium nitride (GaN).

7. The device of claim 1, wherein:

the first gate and the second gate have substantially similar dimensions; and

the third portion and the fourth portion of the wider bandgap semiconductor layer have substantially similar dimensions.

8. A device, comprising:

a first gallium nitride (GaN) -based semiconductor region;

a second GaN-based semiconductor region having a wider band gap than the first GaN-based semiconductor region, the second GaN-based semiconductor region being disposed on the first GaN-based semiconductor region, wherein a heterojunction is established at an interface between the first GaN-based semiconductor region and the second GaN-based semiconductor region;

a first conductor disposed on a first portion of the second GaN-based semiconductor region to form a source electrode;

a second conductor disposed on a second portion of the second GaN-based semiconductor region to form a drain electrode;

a third GaN-based semiconductor region disposed on a third portion of the second GaN-based semiconductor region, adjacent to the heterojunction between the source and the drain, to form a first gate; and

a fourth GaN-based semiconductor region disposed on a fourth portion of the second GaN-based semiconductor region, adjacent to a heterojunction between the first gate and the drain, to form a second gate, wherein the second gate is electrically coupled to the drain, and wherein a threshold voltage associated with the second gate is equal to or greater than a threshold voltage associated with the first gate.

9. The device of claim 8, further comprising:

a silicon substrate on which the first GaN-based semiconductor region is disposed.

10. The device of claim 9, further comprising:

one or more lattice transition regions disposed between the silicon substrate and the first GaN-based semiconductor region.

11. The device of claim 8, further comprising:

a fifth GaN-based semiconductor region disposed on a fifth portion of the second GaN-based semiconductor region, adjacent to a heterojunction between the first gate and the second gate, to form a third gate, wherein the third gate is electrically coupled to a sixth portion of the second GaN-based semiconductor region between the third gate and the second gate, and wherein a threshold voltage associated with the third gate is equal to or greater than the threshold voltage associated with the first gate.

12. The device of claim 8, wherein:

majority carriers in a heterojunction adjacent the first gate are depleted when a potential voltage less than the threshold voltage associated with the first gate is applied between the first gate and the source; and

when a potential voltage less than a threshold voltage associated with the second gate is applied between the second gate and a fifth portion of the second GaN-based semiconductor layer disposed between the first gate and the second gate, majority carriers in a heterojunction adjacent to the second gate deplete.

13. A device, comprising:

a drain electrode;

a source electrode;

a two-dimensional electron gas (2DEG) channel between the drain and the source;

a first gate disposed adjacent the 2DEG channel between the drain and the source, wherein the first gate is configured to deplete majority carriers in the 2DEG channel adjacent the first gate when a voltage applied between the first gate and the source is less than a threshold voltage associated with the first gate;

a second gate disposed adjacent the 2DEG channel between the drain and the first gate and electrically coupled to the drain, wherein the second gate is configured to deplete majority carriers in the 2DEG channel adjacent the second gate when a voltage applied between the second gate and the 2DEG channel between the second gate and the first gate is less than a threshold voltage associated with the second gate; and

wherein the threshold voltage associated with the second gate is equal to or greater than the threshold voltage associated with the first gate.

14. The device of claim 13, further comprising:

a first layer of a group III/V semiconductor compound; and

a second layer of a group III-V semiconductor compound comprising a group III element, wherein the 2DEG channel is present in the first layer adjacent to an interface between the first layer and the second layer.

15. The device of claim 14, wherein the first gate and the second gate comprise a III-V semiconductor compound.

Background

Computing systems have made a significant contribution to the advancement of modern society and are utilized in many applications to achieve advantageous results. Numerous devices, such as desktop Personal Computers (PCs), laptop PCs, tablet PCs, netbooks, smart phones, servers, and the like, have facilitated increased productivity and decreased costs for communicating and analyzing data in most areas of entertainment, education, commerce, and science. One common aspect of computing devices and other electronic devices is switching devices that open and close quickly with relatively low on-resistance, pass large currents, and/or have large breakdown voltages. Switching devices that can be quickly turned on and off with relatively low on-resistance, pass large currents, and/or have large breakdown voltages are commonly used in many electronic devices such as voltage converters, high frequency transmitters and receivers.

Exemplary switching devices that can be turned on and off quickly with relatively low on-resistance, pass large currents, and/or have large breakdown voltages are High Electron Mobility Transistors (HEMTs), also known as Heterostructure Field Effect Transistors (HFETs) or modulation doped field effect transistors (MODFETs). An enhancement mode HEMT turns on and conducts between its drain and source terminals in response to the positive voltage between its gate and source terminals being above the threshold voltage of the device. An enhancement mode HEMT typically turns off in response to the voltage between its gate and source terminals being below a threshold voltage. When the enhancement mode HEMTs are off, a small negative voltage may be applied between their gate and source terminals to reduce leakage current. HEMTs are also easily damaged by high voltages due to overvoltage events, Electrostatic Discharge (EDS) events, etc. Therefore, there is a need for a protection circuit for use with HEMTs and other similar devices without affecting the switching operation of the devices.

Disclosure of Invention

The present technology may be best understood by referring to the following description and accompanying drawings that are used to illustrate embodiments of the present technology for a High Electron Mobility Transistor (HEMT) having an overall electrostatic discharge (ESD) protection structure. The device may include a multi-gate HEMT including a trigger gate and one or more additional gates configured to couple a drain structure of a diode.

In one implementation, the device may include a wider bandgap semiconductor layer disposed on the wide bandgap semiconductor layer to form a heterojunction, wherein a two-dimensional electron gas (2DEG) channel occurs in the wide bandgap semiconductor layer at a boundary adjacent to the wider bandgap semiconductor layer. The source electrode may be disposed on a first portion of the wider bandgap semiconductor layer and the drain electrode may be disposed on a second portion of the wider bandgap semiconductor layer. The first gate electrode may be disposed on a third portion of the wider bandgap semiconductor layer between the source and drain electrodes. The second gate may be disposed on a fourth portion of the wider bandgap semiconductor layer between the first gate and the drain and electrically coupled to the drain. When a potential voltage less than the first threshold voltage is applied between the first gate and the source, majority carriers in the 2DEG channel adjacent to the first gate may be depleted by the first gate. When a potential voltage less than the second threshold voltage is applied between the fifth portion of the wider bandgap semiconductor layer and the second gate between the fourth portion and the third portion of the wider bandgap semiconductor layer, majority carriers in the 2DEG channel adjacent to the second gate may be depleted by the second gate. The second threshold voltage may be greater than or equal to the first threshold voltage.

The device may optionally include one or more additional gates. For example, a third gate may be disposed on a fifth portion of the wider bandgap semiconductor layer between the first gate and the second gate, and may be electrically coupled to a sixth portion of the wider bandgap semiconductor layer between the second gate and the third gate. The third threshold voltage may also be greater than or equal to the first threshold voltage.

In another implementation, a device may include an aluminum gallium nitride (AlGaN) layer disposed on a gallium nitride (GaN) layer. A heterojunction can be established in the GaN layer adjacent to an interface between the GaN layer and the AlGaN layer. A first conductor may be disposed on a first portion of the AlGaN layer to form a source, and a second conductor may be disposed on a second portion of the AlGaN layer to form a drain. A first GaN region may be disposed on a third portion of the AlGaN layer adjacent to the heterojunction between the source and the drain to form a first gate. A second GaN region may be disposed on a fourth portion of the AlGaN layer adjacent to the heterojunction between the first gate and the drain to form a second gate. The second gate may be electrically coupled to the drain. The threshold voltage associated with the second gate may be equal to or greater than the threshold voltage associated with the first gate. Also, the device may optionally include one or more additional gates.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

Drawings

Embodiments of the present technology are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

fig. 1 shows a schematic diagram of an enhancement mode HEMT, in accordance with aspects of the present technique.

Fig. 2 illustrates a block diagram of an enhancement mode HEMT in accordance with aspects of the present technique.

Fig. 3 illustrates a block diagram of an enhancement mode HEMT in accordance with aspects of the present technique.

Detailed Description

Reference will now be made in detail to embodiments of the present technology, examples of which are illustrated in the accompanying drawings. While the technology will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present technology, numerous specific details are set forth in order to provide a thorough understanding of the present technology. However, it is understood that the present technology may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present technology.

Some embodiments of the technology below are presented in terms of routines, modules, logic blocks, and other symbolic representations of operations on data within one or more electronic devices. The description and representations are the means used by those skilled in the art to most effectively convey the substance of their work to others skilled in the art. A routine, module, logic block, etc., is here, and generally, conceived to be a self-consistent sequence of procedures or instructions leading to a desired result. The process includes physical manipulations of physical quantities. Usually, though not necessarily, these physical manipulations take the form of electrical or magnetic signals capable of being stored, transferred, compared, and otherwise manipulated in an electronic device. For convenience, and with reference to common usage, such signals are referred to as data, bits, values, elements, symbols, characters, terms, numbers, strings, and the like, in reference to embodiments of the present technology.

It should be borne in mind, however, that all of these terms are to be interpreted as referring to physical manipulations and quantities, and are merely convenient labels and will be further interpreted in accordance with the terminology commonly used in the art. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the discussion of the present technology, discussions utilizing terms such as "receiving" or the like, refer to the actions and processes of an electronic device, such as an electronic computing device, that manipulates and transforms data. Data is represented as physical (e.g., electronic) quantities within electronic device's logic circuits, registers, memories, etc., and it is converted to other data similarly represented as physical quantities within the electronic device.

In this application, the use of separators is intended to include conjunctions. The use of definite or indefinite articles is not intended to indicate cardinality. In particular, a reference to "the" object or "an" object is intended to mean one of a possible plurality of such objects. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Fig. 1 shows a schematic diagram of an enhancement mode HEMT, in accordance with aspects of the present technique. The HEMT may be used as an electrostatic discharge (ESD) clamp. The HEMT 100 can include a drain 110, a source 120, a first gate 130, and a second gate 140. The two-dimensional electron gas (2DEG) channel of the HEMT 100 can be disposed between the drain 110 and the source 120 of the HEMT 100. The first gate 130 may be disposed adjacent to the 2DEG channel between the drain 110 and the source 120. The first gate 130 can be configured to deplete majority carriers in a 2DEG channel adjacent the first gate 130 when an electrical potential applied between the first gate 130 and the source 120 is less than a threshold voltage associated with the first gate 130. The second gate 140 may be disposed between the drain 110 and the first gate 130, adjacent to the 2DEG channel. The second gate 140 may be electrically coupled to the drain 110. The second gate 140 can be configured to deplete majority carriers in the 2DEG channel adjacent the second gate 140 when a voltage between the second gate 140 and the 2DEG channel between the second gate 140 and the first gate 130 is less than a threshold voltage associated with the second gate. The first gate may be referred to as a trigger gate and the second gate may be referred to as a drain structure of the coupling diode. The threshold voltage associated with the second gate 140 may be equal to or greater than the threshold voltage associated with the first gate 130. In one implementation, the threshold voltage associated with the first and second gates 130, 140 may be about 1-2 volts.

When a voltage less than a threshold voltage associated with the first gate 130 is applied to the first gate 130 and majority carriers in the 2DEG channel are depleted near the first gate 130, the 2DEG channel does not conduct current between the source 110 and the drain 120, and the HEMT 100 is off. When a voltage less than the threshold voltage associated with the second gate 140 is applied to the second gate 140 and the majority carriers in the 2DEG channel are depleted near the second gate 140, the 2DEG channel does not conduct current between the source 110 and the drain 120, and the HEMT 100 is also off. When the voltage applied to the first and second gates 130, 140 is greater than the threshold voltage associated with the respective gate 130, 140, the 2DEG channel can conduct current between the source 100 and drain 120 and the HEMT 100 is on. When the HEMT 100 is on, substantially all of the current flows from the drain 120 to the source 110. Substantially no current flows through the second gate 140 to the source 110.

Under normal operating conditions, the enhancement mode HEMT 100 is turned off. However, under ESD conditions, the depletion region under the first and second gates is reduced, exposing a continuous 2DEG channel between the drain and source to discharge ESD current from the drain to the source. In addition, the HEMT 100 can withstand negative voltages between the gate and the source to reduce power loss due to leakage current through the device without disrupting the operation of the device. In one implementation, the second gate may be configured to have a depletion layer punch-through (punch through) of about 10 to 12 volts (V) when a positive voltage is applied to the source with respect to the drain.

Referring now to fig. 2, a block diagram of an enhancement mode HEMT is shown in accordance with aspects of the present technique. The HEMT 100 can include a wider band gap semiconductor layer 205 disposed on a wide band gap semiconductor 210 to form a heterojunction. The terms "wide bandgap" and "wider bandgap" are used herein to describe the bandgap of the various materials relative to each other. In general, a narrow bandgap refers to a class of semiconductors such as silicon (Si) and germanium (G), while gallium nitride (GaN) can be considered a wide bandgap semiconductor, while aluminum gallium nitride (AlGaN) can be considered a wider bandgap semiconductor. The wide band gap semiconductor layer 210 may be a substantially intrinsic semiconductor layer. As used herein, the term "substantially intrinsic" refers to an unintentionally doped semiconductor, which may include one or more impurities/dopants unintentionally contained in the semiconductor. The 2DEG channel 215 may occur in the wide bandgap semiconductor layer 210 adjacent to the boundary of the wider bandgap semiconductor layer 205. In one implementation, the wider band gap semiconductor layer 205 may be a group III/V semiconductor compound including a group III element, and the wide band gap semiconductor layer 210 may be a group III/V semiconductor compound. For example, the wide band gap semiconductor layer 210 may include gallium nitride (GaN), and the wider band gap semiconductor layer 205 may include aluminum gallium nitride (AlGaN). The majority carriers in the 2DEG channel 215 may be electrons in a heterojunction formed between the AlGaN layer 205 and the GaN layer 210.

The HEMT 100 can also include a drain 220, a source 225, a first gate 230 and a second gate 235. The source electrode 225 can be disposed on a first portion of the wider bandgap semiconductor layer 205 and the drain electrode 220 can be disposed on a second portion of the wider bandgap semiconductor layer 205. In one implementation, the drain 220 and source 225 may include conductors, such as titanium (Ti), titanium nitride (TiN), tungsten (W), titanium Tungsten (TiW), molybdenum (Mo), etc., which may form a good ohmic contact with the 2DEG channel 215 through the wider bandgap semiconductor layer 205. In one implementation, the first and second gates 230, 235 may comprise doped III-V semiconductor compounds. For example, the doped group III/V semiconductor compounds of the first and second gates 330, 335 may include p-type doped GaN. In one implementation, the second gate 235 may be spaced apart from the first gate 230 by about 1 micrometer (μm) or less. In one implementation, the channel length of the second gate 235 may be substantially less than the channel length of the first gate 230. The channel length of the second gate 235 may be significantly smaller such that when the voltage at the source 225 is positive and reaches a level, the conduction mechanism of the channel of the second gate 235 is at or above the punch-through mechanism set by the drain induced barrier lowering mechanism. For example, the channel length of the second gate 235 may be adjusted such that a predetermined punch-through voltage of about 10V to 12V is achieved for an ESD event.

The first gate 230 may be disposed on a third portion of the wider bandgap semiconductor layer 205 between the source 225 and the drain 220. When a voltage less than the first threshold voltage is applied between the first gate 230 and the source 225, majority carriers in the 2DEG channel 215 adjacent the first gate can be depleted 240 by the first gate 230. The second gate 235 may be disposed on a fourth portion of the wider bandgap semiconductor layer 205 between the first gate 230 and the drain 220. The second gate 235 may be electrically coupled to the drain 220. When a voltage less than the second threshold voltage is applied between the second gate electrode 235 and a fifth portion of the wider bandgap semiconductor layer 205 between the fourth portion and the third portion of the wider bandgap semiconductor layer 205, majority carriers in the 2DEG channel 215 adjacent to the second gate electrode 235 may be depleted 250 by the second gate electrode 235. The second threshold voltage may be equal to or greater than the first threshold voltage.

The first and second gates 230, 235 may have substantially similar dimensions. For example, the length, width, and thickness of the p-type doped GaN layers 230, 235 may be substantially the same. Similarly, the dimensions of the third and fourth portions of the wider bandgap semiconductor layer 205 adjacent the first and second gate electrodes 230, 235 may have substantially similar dimensions. For example, the AlGaN layer 205 adjacent to the first and second gates 230, 235 may be substantially uniform in thickness. If the HEMT 100 is configured to have substantially equal first and second threshold voltages, the concentration of the additional group III element (e.g., aluminum) in the wider bandgap semiconductor layer 205 adjacent the first and second gates 230, 235 may be substantially equal. If the HEMT 100 is configured with a second gate 235 having an associated second threshold voltage that is greater than the first threshold voltage associated with the first gate 230, the concentration of the additional group III element (e.g., aluminum) in the wider bandgap semiconductor layer 205 adjacent the second gate 235 can be greater than the concentration of the additional group III element (e.g., aluminum) in the wider bandgap semiconductor layer 205 adjacent the first gate 230.

When a voltage less than the threshold voltage associated with the first gate 230 is applied to the first gate 230 and the majority carriers in the 2DEG channel are depleted near the first gate 230, then the 2DEG channel cannot conduct current between the source 225 and the drain 220, and the HEMT 100 is off. When a voltage less than the threshold voltage associated with the second gate 235 is applied to the second gate 235 and the majority carriers in the 2DEG channel are depleted near the second gate 235, then the 2DEG channel cannot conduct current between the drain 220 and the source 225 and the HEMT 100 is also off. When the voltage applied to the first and second gates 230, 235 is greater than the threshold voltage associated with the respective gates 230, 235, the 2DEG channel can conduct current between the drain 220 and the source 225, and the HEMT 100 is turned on.

Under normal operating conditions, the enhancement mode HEMT 100 is off. However, under ESD conditions, the depletion region under the first and second gates is reduced, exposing a continuous 2DEG channel between the drain and source for discharging ESD current. In addition, the HEMT 100 can withstand negative voltages between the gate and the source to reduce power loss due to leakage current through the device without disrupting the operation of the device.

The HEMT 100 can also include a substrate 255 on which the wide band gap semiconductor layer 210 can be formed. In one implementation, the substrate may be silicon, silicon carbide, or the like, which may provide for ease of forming the wide band gap semiconductor layer 210 by methods such as epitaxial deposition. The HEMT 100 can optionally include a lattice transition layer 260 between the wider band gap semiconductor layer 205 and the wide band gap semiconductor layer 210 to reduce the lattice mismatch between the two layers. In one implementation, lattice transition layer 260 may include an aluminum nitride (AlN) layer. The HEMT 100 can further include a first gate contact 265 disposed on the first gate 230 and a second gate contact 270 disposed on the second gate 235. In one implementation, the first and second gate contacts 265, 270 may include conductors, such as titanium (Ti), titanium nitride (TiN), tungsten (W), titanium Tungsten (TiW), molybdenum (Mo), etc., which may form good ohmic contacts to the respective first and second gates 230, 235. The HEMT 100 can also include many other layers, regions, structures, elements, etc. that are known to those skilled in the art or are apparent to those skilled in the art in conjunction with aspects of the present technique. However, because these other layers, regions, structures, elements, etc. are not germane to an understanding of aspects of the present technology, they are not described here again.

Embodiments of the HEMT 100 device are compatible with GaN and GaN on silicon (Si) and therefore can be integrated in circuits fabricated using GaN or GaN on Si device technology. Thus, the HEMT 100 can be readily used as GaN in circuits based on Si technology and/or ESD clamps in GaN.

In aspects, the HEMT may comprise a plurality of additional gates. Referring now to fig. 3, a block diagram of an enhancement mode HEMT is shown in accordance with aspects of the present technique. The HEMT300 can include a wider band gap semiconductor layer 305 disposed on a wide band gap semiconductor 310 to form a heterojunction. The wide band gap semiconductor layer 310 may be a substantially intrinsic semiconductor layer. The 2DEG channel 315 may occur in the wide bandgap semiconductor layer 310 adjacent to the boundary of the wider bandgap semiconductor layer 305. In one implementation, the wider band gap semiconductor layer 305 may be a group III/V semiconductor compound including a group III element, and the wide band gap semiconductor layer 310 may be a group III/V semiconductor compound. For example, wide band gap semiconductor layer 310 may include gallium nitride (GaN), while wider band gap semiconductor layer 305 may include aluminum gallium nitride (AlGaN). The majority carriers in the 2DEG channel 315 may be electrons in a heterojunction formed between the AlGaN layer 305 and the GaN layer 310.

The HEMT300 may further include a drain 320, a source 325, a first gate 330, a second gate 335, and a third gate 340. The source 325 may be disposed on a first portion of the wider bandgap semiconductor layer 305 and the drain 320 may be disposed on a second portion of the wider bandgap semiconductor layer 305. In one implementation, the drain 320 and source 325 may comprise conductors, such as titanium (Ti), titanium nitride (TiN), tungsten (W), titanium Tungsten (TiW), molybdenum (Mo), etc., which may form a good ohmic contact with the 2DEG channel 315 through the wider bandgap semiconductor layer 305. In one implementation, the first and second gates 330, 335 may comprise doped III/V semiconductor compounds. For example, the doped group III/V semiconductor compounds of the first and second gates 330, 335 may include p-type doped GaN.

The first gate 330 may be disposed on a third portion of the wider bandgap semiconductor layer 305 between the source 325 and drain 320. The second gate electrode 335 may be disposed on a fourth portion of the wider bandgap semiconductor layer 305 between the first gate electrode 330 and the drain electrode 320. The second gate 335 may be electrically coupled 345 to the drain 320. A third gate 340 may be disposed on a fifth portion of the wider bandgap semiconductor layer 305 between the first gate 330 and the second gate 335. The third gate 340 may be electrically coupled 350 to a sixth portion of the wider bandgap semiconductor layer 305 between the second gate 335 and the third gate 340. When a voltage less than the first threshold voltage is applied between the first gate 330 and the source 325, majority carriers in the 2DEG channel 315 adjacent the first gate 330 can be depleted 355 by the first gate 330. When a potential voltage less than the second threshold voltage is applied between the second gate 335 and the third gate 340, majority carriers in the 2DEG channel 315 adjacent the second gate 335 can be depleted 360 by the second gate 335. When a voltage less than the third threshold voltage is applied between the third gate 340 and the first gate 330, majority carriers in the 2DEG channel adjacent to the third gate 340 can be depleted 365 by the third gate 340. The second threshold voltage and the third threshold voltage may be greater than or equal to the first threshold voltage. The HEMT300 may include any number of additional gates configured similarly to the third gate 340.

The first, second and third gates 330, 335, 340 may have substantially similar dimensions. For example, the length, width, and thickness of the p-type doped GaN layers 330, 335, 340 may be substantially the same. Similarly, the dimensions of the third, fourth, and fifth portions of the wider bandgap semiconductor layer 305 adjacent to the first, second, and third gate electrodes 330, 335, 340 may have substantially similar dimensions. For example, the thickness of the AlGaN layer 305 adjacent to the first, second and third gates 330, 335, 340 may be substantially uniform. If the HEMT300 is configured to have substantially equal first, second and third threshold voltages, the concentration of the additional group III element (e.g., aluminum) in the wider bandgap semiconductor layer 305 adjacent to the first, second and third gates 330, 335, 340 can be substantially equal. If the HEMT300 is configured to have a second gate 335 and/or a third gate 340 with associated second and/or third threshold voltages that are greater than the first threshold voltage associated with the first gate 330, the concentration of the additional group III element (such as aluminum) in the wider bandgap semiconductor layer 305 adjacent the second and third gates 335, 340 can be greater than the concentration of the additional group III element (such as aluminum) in the wider bandgap semiconductor layer 305 adjacent the first gate 330.

When a voltage less than the threshold voltage associated with the first gate 330 is applied to the first gate 330 and the majority carriers in the 2DEG channel are depleted near the first gate 330, the 2DEG channel cannot conduct current between the drain 320 and the source 325, and the HEMT300 turns off. When a voltage less than the threshold voltage associated with the second gate 335 is applied to the second gate 335 and the majority carriers in the 2DEG channel are depleted near the second gate 335, the 2DEG channel cannot conduct current between the drain 320 and the source 325, and the HEMT300 is also off. When a voltage less than the threshold voltage associated with the third gate 340 is applied to the third gate 340 and the majority carriers in the 2DEG channel are depleted near the third gate 340, the 2DEG channel cannot conduct current between the drain 320 and the source 325, and the HEMT300 is also off. When the voltages applied to the first, second, and third gates 330, 335, 340 are greater than the threshold voltages associated with the respective gates 330, 335, 340, the 2DEG channel can conduct current between the drain 320 and the source 325, and the HEMT300 is turned on.

Under normal operating conditions, the enhancement mode HEMT300 is turned off. However, under ESD conditions, the depletion regions under the first, second and third gates decrease, exposing a continuous 2DEG channel between the drain and source to discharge ESD current. In addition, the HEMT300 can withstand negative voltages between the gate and the source to reduce power loss due to leakage current through the device without disrupting the operation of the device.

The HEMT300 can further include a substrate 370 on which the wide band gap semiconductor layer 310 can be formed. In one implementation, substrate 370 may be silicon, silicon carbide, or the like, which may be readily formed into wide band gap semiconductor layer 310 by methods such as epitaxial deposition. The HEMT300 can optionally include a lattice transition layer 375 between the wide band gap semiconductor layer 310 and the wider band gap semiconductor layer 305 to reduce the lattice mismatch between the two layers. In one implementation, lattice transition layer 375 may include an aluminum nitride (AlN) layer. The HEMT300 can further include a first gate contact 380 disposed on the first gate 330, a second gate contact 385 disposed on the second gate 335, a third gate contact 385 disposed on the third gate 340, and a body contact 395 for coupling the third gate 340 to the wider bandgap semiconductor layer 305 between the second gate 335 and the third gate 340. In one implementation, the first, second and third gate contacts 380, 385, 390 and the body contact 395 may include conductors, such as titanium (Ti), titanium nitride (TiN), tungsten (W), titanium Tungsten (TiW), molybdenum (Mo), etc., which may form good ohmic contacts with the respective first, second and third gates 330, 335, 340 and the wider bandgap semiconductor layer 305. The HEMT300 may also include many other layers, regions, structures, elements, etc. that are known to those skilled in the art or that will be apparent to those skilled in the art in combination with aspects of the present technique. However, because these other layers, regions, structures, elements, etc. are not germane to an understanding of aspects of the present technology, they are not described here again.

Embodiments of the HEMT300 device are compatible with GaN and GaN on silicon (Si) and therefore can be integrated in circuits fabricated on Si device technology using GaN or GaN. Thus, the HEMT300 can be easily used as GaN in circuits based on Si technology and/or ESD clamps in GaN.

The foregoing descriptions of specific embodiments of the present technology have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the technology and its practical application, to thereby enable others skilled in the art to best utilize the technology and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.