Common-drain bidirectional switch

Abstract

A bidirectional switch for high power electronic devices is compact and has low on-resistance. A bidirectional switch includes several layers epitaxially grown on a substrate, the epitaxial layer including a channel layer and a barrier layer grown on the channel layer, the interface of the barrier layer and the channel layer defining a heterojunction inducing a two-dimensional electron gas (2DEG) within the channel layer, the 2DEG extending laterally at the interface between the barrier layer and the channel layer. The bidirectional switch includes two ohmic source contacts, each in contact with the 2DEG channel layer near opposite ends of the 2DEG. The bidirectional switch also includes two gate electrodes disposed between the two source contacts above the barrier layer. The voltage applied to the gate electrodes controls the current in the bidirectional switch between the two contacts.

Description

BACKGROUND OF THE INVENTION

[0001] Electronic circuits typically include transistors that act as electronic switches to regulate or control current in a portion of the circuit. One type of transistor is a field effect transistor, where a voltage is applied to a gate terminal to turn the transistor on and off. A semiconductor channel region is disposed between a drain terminal and a source terminal. When the transistor is turned on, current flows through the semiconductor channel region between the source terminal and the drain terminal. When the transistor is turned off, little or no current flows through the semiconductor channel region between the source terminal and the drain terminal. The gate terminal is disposed over the semiconductor channel region between the source terminal and the drain terminal. The voltage on the gate terminal creates an electric field that affects whether the semiconductor channel region conducts current, and thus the term "field effect transistor" is used.

[0002] Silicon has traditionally been used to fabricate transistors. However, compared to silicon transistors, semiconductor materials with a wider bandgap can be used to fabricate transistors that operate at higher voltages and switch higher powers with higher efficiency. Silicon carbide (SiC), aluminum nitride (AlN), gallium nitride (GaN), and zinc oxide (ZnO) are each examples of wide bandgap semiconductor materials that can be used to fabricate power electronic devices. One way to use such wide bandgap semiconductor materials is to grow two different semiconductor materials to form a heterojunction.

[0003] The two semiconductor materials can have sufficiently different bandgaps such that when brought together, the cusp in the conduction band of the structure lies exactly below the Fermi level at the top surface of the channel layer. This means that electrons can flow freely within this region. This region is thin in depth and forms a plane parallel to the top surface of the channel region. Thus, this region is referred to as the "2DEG" region (two-dimensional electron gas) to emphasize its planar form. Additionally, due to the high mobility of electrons in this region, this region is also referred to as the 2DEG "electron sea". Thus, the 2DEG region is highly conductive. The 2DEG region forms the channel region of a power semiconductor to allow high current with relatively low resistance to pass through. A field effect transistor using such a 2DEG is referred to as a "high electron mobility transistor" (or HEMT).

[0004] The subject matter claimed herein is not limited to embodiments that solve any disadvantages or operate only in environments such as those described above. Rather, this background is provided only to illustrate an example of the technical field in which some embodiments described herein may be practiced. SUMMARY OF THE INVENTION

[0005] The embodiments described herein relate to a bidirectional switch for high-power electronic devices. The bidirectional switch is compact in size and has a low on-resistance, which will be explained later. The bidirectional switch includes a plurality of epitaxial layers grown on a substrate along a specific crystal direction. The epitaxial layers include a buffer layer, a channel layer, and a barrier layer epitaxially grown on the substrate. The buffer layer prevents crystal defects from entering the channel layer. The interface between the barrier layer and the channel layer defines a heterojunction that induces a two-dimensional electron gas (2DEG) in the channel layer. The 2DEG extends perpendicular to the epitaxial growth direction.

[0006] The bidirectional switch further includes two ohmic contacts, each in contact with the 2DEG of the channel layer, near opposite ends of the 2DEG. Thus, the 2DEG defines the channel of the bidirectional switch through which current can flow in either direction from one contact to the other (hence the term "bidirectional switch"). The bidirectional switch also includes two gate electrodes disposed on the barrier layer and between the two contacts. The voltage applied to these gate electrodes controls whether current flows in the bidirectional switch between the two contacts.

[0007] The bidirectional switch can be considered, for example, as two high electron mobility transistors (HEMTs) with their drains connected together. That is, the first of the two ohmic contacts can be used as the source contact of the first HEMT, and the two gate electrodes closest to the first contact can be used as the gate electrodes of the first HEMT. On the other hand, the second of the two ohmic contacts can be used as the source contact of the second HEMT, and the other of the two gate electrodes can be used as the gate electrode of the second HEMT. The portion of the 2DEG between the two gate electrodes can be defined as a common drain region where the drains of each of the first HEMT and the second HEMT are connected. An enhancement-mode (E-mode) HEMT is typically on when a gate-to-source voltage higher than the threshold voltage is applied to its gate, and an enhancement-mode (E-mode) HEMT is typically off when a gate-to-source voltage lower than the gate-to-source threshold voltage is applied to the gate.

[0008] In the operation of a conventional E-mode HEMT, the voltage at the drain of the HEMT is typically higher than the voltage at the source of the HEMT. In this state, if the gate-to-source voltage is higher than the threshold voltage of the HEMT, current will flow from the drain to the source through the 2DEG. This can be referred to as a HEMT operating in "forward conduction". However, if the source voltage is significantly higher than the drain voltage (referred to as "reverse conduction"), the gate control for conduction may be lost. This is because the HEMT also has another threshold voltage called the "gate-to-drain threshold voltage", which has no effect in forward conduction but dominates in reverse conduction. That is, because the voltage applied to the gate is relative to the source voltage, and because the source voltage is significantly higher than the drain voltage, the voltage applied to the gate will be much higher than the gate-to-drain threshold voltage. This means that regardless of the control signal applied to the gate, the HEMT is always conducting. Therefore, the HEMT is always conducting in the reverse conduction mode. Therefore, in a bidirectional switch, either one of the two HEMTs having the higher voltage applied to its source contact (referred to herein as the "upstream HEMT") will operate in the reverse conduction mode and thus be turned on. On the other hand, the other HEMT having the lower voltage applied to its source contact (referred to herein as the "downstream HEMT") can control its current through the gate-to-source voltage (forward conduction).

[0009] Therefore, at any given moment, it is determined whether to allow current to flow or block current in the bidirectional switch by operating which HEMT among the downstream HEMTs at that given moment. That is, if the gate voltage of the downstream HEMT is higher than the threshold voltage, current will flow through the bidirectional switch. On the other hand, if the gate voltage of the downstream HEMT is less than the threshold voltage, current is blocked from passing through the bidirectional switch.

[0010] Furthermore, regarding the epitaxial structure of the bidirectional switch, the 2DEG portion between the two gate electrodes serves as a common drain, and the overall size of the bidirectional switch can be approximately the same as that of a single HEMT. This is because the length of the common drain portion of the 2DEG is approximately the same as the distance between the gate electrode and the drain contact of a single HEMT. This also allows the bidirectional switch to have an on-resistance approximately the same as that of a single HEMT, because the on-resistance of the HEMT is dominated by the distance between the gate electrode and the drain contact of the HEMT. Therefore, the bidirectional switch according to the principles described herein allows a bidirectional switch in high-power applications, while also allowing the bidirectional switch to have a small on-resistance and a compact size of a typical E-mode HEMT.

[0011] Additional features and advantages will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the teachings herein. The features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims. The features of the invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] To describe the manner in which the advantages and features of the circuits, systems, and methods described herein can be obtained, a more particular description of the embodiments briefly described herein will be presented by reference to the specific embodiments thereof that are illustrated in the accompanying drawings. It should be understood that these drawings depict only typical embodiments of the circuits, systems, and methods described herein and are thus not to be considered limiting of their scope, and certain circuits, systems, and methods will be described and explained with additional specificity and detail by use of the drawings, wherein:

[0013] Figure 1 A cross-sectional view of a bidirectional switch is shown in which the principles described herein may be practiced and which is only one example of a bidirectional switch consistent with the principles described herein;

[0014] Figure 2 A bidirectional switch is shown that is Figure 1 an example of a bidirectional switch but shown in the form of a circuit structure;

[0015] Figure 3 A bidirectional switch is shown that includes Figure 2 an example of a bidirectional switch and a switching circuit with a biased substrate;

[0016] Figure 4 A bidirectional switch is shown that represents Figure 3 an example of the bidirectional switch in but shows the switching circuit in more detail;

[0017] Figure 5 A cross-sectional view of a bidirectional switch is shown that is Figure 1 an example of the bidirectional switch in but includes a field plate;

[0018] Figure 6 A bidirectional switch is shown that is Figure 5 an example of the bidirectional switch in but shown in the form of a circuit structure and having field plate control;

[0019] Figure 7 A bidirectional switch is shown that is Figure 3 an example of the bidirectional switch in but shows an example of the switching circuit in more detail;

[0020] Figure 8shows a bidirectional switch, which is Figure 7 an example of the bidirectional switch of Figure 7 but shows a further simplified form of the example switch circuit shown in

[0021] Figure 9 shows a waveform diagram, which shows an example of a signal representing Figure 8 the voltages at different positions in the bidirectional switch of DETAILED DESCRIPTION

[0022] The embodiments described herein relate to bidirectional switches for high-power electronic devices. The bidirectional switch is compact in size and has a low on-resistance, which will be explained later. The bidirectional switch includes a number of epitaxial layers grown on a substrate along a specific crystal direction. The epitaxial layers include a buffer layer, a channel layer, and a barrier layer epitaxially grown on the substrate. The buffer layer prevents crystal defects from entering the channel layer. The interface between the barrier layer and the channel layer defines a heterojunction that induces a two-dimensional electron gas (2DEG) in the channel layer. The 2DEG extends perpendicular to the epitaxial growth direction.

[0023] The bidirectional switch also includes two ohmic contacts, each in conductive contact with the 2DEG of the channel layer, near opposite ends of the 2DEG. Thus, the 2DEG defines the channel of the bidirectional switch through which current can flow in either direction from one contact to the other (hence the term "bidirectional switch"). The bidirectional switch also includes two gate electrodes disposed on the barrier layer and between the two contacts. The voltage applied to these gate electrodes controls whether current flows in the bidirectional switch between the two contacts.

[0024] The bidirectional switch can, for example, be considered as two high electron mobility transistors (HEMTs) with their drains connected together. That is, the first of the two ohmic contacts can be used as the source contact of the first HEMT, and the two gate electrodes closest to the first contact can be used as the gate electrodes of the first HEMT. On the other hand, the second of the two ohmic contacts can be used as the source contact of the second HEMT, and the other of the two gate electrodes can be used as the gate electrode of the second HEMT. The portion of the 2DEG between the two gate electrodes can be defined as a common drain region where the drains of each of the first HEMT and the second HEMT are connected. When a gate-to-source voltage higher than the threshold voltage is applied to its gate, an enhancement-mode (E-mode) HEMT is typically in the on state, and when a gate-to-source voltage lower than the gate-to-source threshold voltage is applied to the gate, an enhancement-mode (E-mode) HEMT is typically in the off state.

[0025] In the operation of a conventional E-mode HEMT, the voltage at the drain of the HEMT is typically higher than the voltage at the source of the HEMT. In this state, if the gate-to-source voltage is higher than the threshold voltage of the HEMT, current will flow from the drain to the source through the 2DEG. This can be referred to as a HEMT operating in "forward conduction". However, if the source voltage is significantly higher than the drain voltage (referred to as "reverse conduction"), the gate control of conduction may be lost. This is because the HEMT also has another threshold voltage called the "gate-to-drain threshold voltage", which has no effect in forward conduction but dominates in reverse conduction. That is, because the voltage applied to the gate is relative to the source voltage, and because the source voltage is significantly higher than the drain voltage, the voltage applied to the gate will be much higher than the gate-to-drain threshold voltage. This means that regardless of the control signal applied to the gate, the HEMT is always conducting. Therefore, the HEMT is always conducting in the reverse conduction mode. Therefore, in a bidirectional switch, either one of the two HEMTs having the higher voltage applied to its source contact (referred to herein as the "upstream HEMT") will operate in the reverse conduction mode and thus be turned on. On the other hand, the other HEMT having the lower voltage applied to its source contact (referred to herein as the "downstream HEMT") can control its current through the gate-to-source voltage (forward conduction).

[0026] Therefore, at any given moment, it is determined whether to allow current to flow or block current in the bidirectional switch by operating which HEMT among the downstream HEMTs at that given moment. That is, if the gate voltage of the downstream HEMT is higher than the threshold voltage, current will flow through the bidirectional switch. On the other hand, if the gate voltage of the downstream HEMT is less than the threshold voltage, current is blocked from passing through the bidirectional switch.

[0027] Furthermore, regarding the epitaxial structure of the bidirectional switch, the 2DEG portion between the two gate electrodes serves as a common drain, and the overall size of the bidirectional switch can be approximately the same as that of a single HEMT. This is because the length of the common drain portion of the 2DEG is approximately the same as the distance between the gate electrode and the drain contact of a single HEMT. This also allows the bidirectional switch to have approximately the same on-resistance as a single HEMT, because the on-resistance of the HEMT is dominated by the distance between the gate electrode and the drain contact of the HEMT. Therefore, the bidirectional switch according to the principles described herein allows a bidirectional switch in high-power applications, while also allowing the bidirectional switch to have a small on-resistance and a compact size of a typical E-mode HEMT.

[0028] Figure 1A cross-sectional view of a bidirectional switch 100 is shown, in which the principles described herein can be practiced, and which is merely an example of a bidirectional switch consistent with the principles described herein. The bidirectional switch 100 includes an epitaxial layer (not labeled) grown on a substrate 110. The epitaxial layer is composed of a buffer layer 115, a channel layer 120, and a barrier layer 130 epitaxially grown on the channel layer 120.

[0029] Figure 1 A coordinate system 105 is also shown. The y-axis is shown as vertical in Figure 1 The positive y-direction is the direction in which epitaxial growth occurs to sequentially form the buffer layer 115, the channel layer 120, and the barrier layer 130. Conversely, the x-axis is horizontal in Figure 1 and perpendicular to the direction of epitaxial growth. The direction parallel to the y-axis will be referred to as "along" the y-axis. The direction parallel to the x-axis will be referred to as "along" the x-axis.

[0030] The interface between the channel layer 120 and the barrier layer 130 defines a heterojunction that induces a two-dimensional electron gas (referred to herein as "2DEG") 140 within the channel layer 120, through which current can flow when the bidirectional switch 100 is turned on. The 2DEG 140 extends parallel to the interface between the channel layer 120 and the barrier layer 130, and thus extends along the x-axis. The 2DEG 140 is formed because the channel layer 120 and the barrier layer 130 are made of different semiconductor materials with sufficiently different bandgaps such that when joined together, the combined bandgap just drops below the Fermi level within the channel layer 120, thereby forming a region of high electron concentration (2DEG 140). By way of example only, if the channel layer 120 is composed of gallium nitride (GaN) and the barrier layer 130 is composed of aluminum gallium nitride (AlGaN), the bandgap difference will be sufficient to generate the 2DEG 140. However, the principles described herein are not limited to the types of semiconductor materials that make up the channel layer 120 and the barrier layer 130.

[0031] The bidirectional switch 100 further includes a first contact 150A, a second contact 150B, a first gate electrode 160A, and a second gate electrode 160B. The first contact 150A and the second contact 150B are disposed at opposite ends (along the x-axis) of the 2DEG 140. More specifically, in Figure 1 the first contact 150A is disposed to be electrically connected to the left end of the 2DEG 140, while the second contact 150B is disposed to be electrically connected to the right end of the 2DEG 140.

[0032] The first gate electrode 160A and the second gate electrode 160B (along the positive y-direction) are disposed on the barrier layer 130 and (along the x-axis) between the first contact 150A and the second contact 150B. In Figure 1In this case, the first gate electrode 160A is closer to the first contact 150A, while the second gate electrode 160B is closer to the second contact 150B. A part of the 2DEG 140 under the gate electrode 160A is affected by the voltage applied to the gate electrode 160A. Similarly, a part of the 2DEG 140 under the gate electrode 160B is affected by the voltage applied to the gate electrode 160B. For example, when the bilateral switch 100 is turned on, the 2DEG 140 is continuous under each of the gate electrode 160A and the gate electrode 160B, allowing current to flow freely between the first contact 150A and the second contact 150B. However, when the bilateral switch 100 is turned off, the 2DEG 140 is discontinuous under the gate electrode 160A or the gate electrode 160B.

[0033] The bilateral switch 100 can be considered, for example, as two enhancement-mode high electron mobility transistors (E-mode HEMTs) whose drains are connected together. For example, the bilateral switch includes a first HEMT 101 and a second HEMT 102. The first contact 150A is the source contact of the first HEMT 101, and the first gate electrode 160A is the gate electrode of the first HEMT 101. Similarly, the second contact 150B is the source contact of the second HEMT 102, and the second gate electrode 160B is the gate electrode of the second HEMT 102. The portion of the 2DEG 140 between the first gate electrode 160A and the second contact 160B can be considered as a common drain region 170 where the drains of each of the first HEMT 101 and the second HEMT 102 are connected.

[0034] The first HEMT 101 is an E-mode HEMT because there is a p-doped semiconductor portion 161A between the first gate electrode 160A and the barrier layer 130. Similarly, the second HEMT 102 is another E-mode HEMT because there is another p-doped semiconductor portion 161B between the second gate electrode 160B and the barrier layer 130.

[0035] If the drain voltage of the HEMT 101 is higher than the voltage applied to the source contact 150A, and a zero voltage is applied to the gate electrode 160A relative to the source contact 150A, the p-doped semiconductor portion 161A will cause the 2DEG 140 to be discontinuous under the gate electrode 160A. Similarly, if the drain voltage of the HEMT 102 is higher than the voltage applied to the source contact 150B, and a zero voltage is applied to the gate electrode 160B relative to the source contact 150B, the p-doped semiconductor portion 161B will cause the 2DEG 140 to be discontinuous under the gate electrode 160B.

[0036] In the normal operation of a typical HEMT, the drain voltage is more positive than the source voltage. In this state, when the gate-to-source voltage is higher than the threshold voltage of the device, the E-mode HEMT conducts. Thus, current will flow from the drain to the source, herein referred to as "forward conduction". Additionally, if the drain voltage is more positive than the source voltage, the E-mode HEMT turns off when the gate voltage is less than the threshold voltage of the device.

[0037] However, if the source voltage is more positive than the drain voltage (referred to as "reverse conduction"), the gate control of the current can be different. This is because the HEMT also has another threshold voltage called the "gate-to-drain" threshold voltage, which has no effect in forward conduction but dominates in reverse conduction. That is, because the voltage applied to the gate is with respect to the source voltage, and because the source voltage is significantly higher than the drain voltage, the voltage applied to the gate will be much higher than the gate-to-drain threshold voltage. This means that the HEMT is always on regardless of the control signal applied to the gate. Thus, the HEMT is always on in the reverse conduction mode.

[0038] Thus, in the bidirectional switch 100, either one of the two HEMTs having the higher voltage applied to its source contact (herein referred to as the "upstream HEMT") will operate in reverse conduction and thus be on. On the other hand, the other HEMT having the lower voltage applied to its source contact (herein referred to as the "downstream HEMT") can be controlled to turn off when a voltage less than its gate electrode-to-source threshold voltage is applied to its gate electrode, or to turn on (in forward conduction) when at least the gate electrode-to-source threshold voltage is applied to its gate electrode.

[0039] Thus, at any given moment, it is determined whether to allow current to flow or block current in the bidirectional switch 100 by operating which HEMT among the downstream HEMTs at that given moment. That is, if the gate voltage of the downstream HEMT is higher than the threshold voltage of the device, current is allowed to flow through the bidirectional switch 100. On the other hand, if the gate voltage of the downstream HEMT is less than the threshold voltage, current flow through the bidirectional switch 100 is blocked.

[0040] An example of the operation of the bidirectional switch 100 will now be briefly described in terms of the components of the bidirectional switch 100. Assume that the first contact 150A (the source contact of the first HEMT 101) and the gate electrode 160A have a high voltage (e.g., +100 volts) applied thereto, and the second contact 150B has a low voltage (e.g., ground) applied thereto. This means that the second HEMT 102 is the "downstream HEMT". Additionally, assume that the downstream HEMT 102 is initially off, and thus the bidirectional switch 100 is off. Recall that the voltage applied to the gate electrode 160A is with respect to the source contact 150A.

[0041] In this case, since the gate-to-source voltage is zero volts, the gate electrode 160A will still be high (e.g., +100 volts). Then, the upstream HEMT will operate in reverse conduction, and its drain 170 will be at a voltage of 100 - Vth, where Vth is the threshold voltage of the device. Similarly, if a positive gate-to-source voltage (e.g., +6 volts, higher than Vth) is applied to the gate electrode 160A with respect to the source contact 150A, the gate electrode 160A will also still be high (e.g., +106 volts). In this case, since the 2DEG 140 is formed under the gate electrode 160A, there is a continuous 2DEG from 150A to the drain 170, and the voltage at the drain 170 will be 100 volts. In either case, when a high voltage is applied to the contact 150A, the gate electrode 160A will also be higher than the common drain region 170, regardless of the voltage applied to the gate electrode 160A with respect to the contact 150A. Therefore, when a high voltage is applied to the source contact 150A, the upstream HEMT 101 will exceed its gate-to-drain threshold voltage, the upstream HEMT 101 will operate in reverse conduction, and the voltage at the common drain region 170 will be pulled up to a voltage close to that at the source contact 150A.

[0042] However, since the voltage at the common drain region 170 will be pulled up to a voltage higher than that at the second contact 150B (the source contact of the second HEMT 102), whether the two-way switch 100 allows or blocks current flow will be determined by the operation of the second HEMT (i.e., the downstream HEMT). That is, if a voltage less than Vth is applied to the second gate electrode 160B, the 2DEG 140 will be discontinuous under the second gate electrode 160B, and the two-way switch 100 will block the current.

[0043] On the other hand, if a voltage higher than the threshold voltage Vth of the second HEMT 102 is applied to the second gate electrode 160B, the 2DEG 140 will become continuous under the second gate electrode 160B. Therefore, the second HEMT 102 will operate in forward conduction, and the two-way switch 100 will alternatively conduct current from the first contact 150A to the second contact 150B.

[0044] The two-way switch 100 is "two-way". If a high voltage is applied to the second contact 150B while a low voltage is applied to the first contact 150A, the operation of the two-way switch 100 will be mirrored.

[0045] In addition, regarding the epitaxial structure of the bidirectional switch 100, since the portion of the 2DEG 140 between the two gate electrodes serves as the common drain region 170, the overall size of the bidirectional switch 100 can actually be the same as that of a single HEMT (but can be slightly larger than a single HEMT). This is because the length of the common drain region 170 perpendicular to the epitaxial growth direction is approximately the same as the distance between the gate electrode and the drain contact of a single HEMT. This also allows the bidirectional switch 100 to have a conduction resistance approximately the same as that of a single HEMT, since the conduction resistance of an HEMT is governed by the distance between the gate electrode and the drain contact of the HEMT. Thus, the bidirectional switch 100 according to the principles described herein allows a bidirectional switch in high-power applications, while also allowing the bidirectional switch to have a small conduction resistance and a compact size typical of an E-mode HEMT.

[0046] Additional circuit components can be used to assist the operation of the bidirectional switch 100. To begin introducing these additional circuit components, Figure 2 a bidirectional switch 200 is shown, which bidirectional switch 200 is Figure 1 an example of the bidirectional switch 100, but shown in circuit form. That is, Figure 2 the bidirectional switch 200 includes a first HEMT 210 and a second HEMT 220. The first HEMT 210 can be Figure 1 an example of the first HEMT 101. The second HEMT 220 can be Figure 1 an example of the second HEMT 102.

[0047] The first HEMT 210 has a gate electrode 211 that controls whether current flows between its drain contact 212 and its source contact 213. Similarly, the second HEMT 220 has a gate electrode 221 that controls whether current flows between its drain contact 222 and its source contact 223. The drain contact 212 of the first HEMT 210 and the drain contact 222 of the second HEMT 220 are connected together to form a common drain 230.

[0048] Figure 2 The source contacts 213, source contact 223, gate electrode 211, gate electrode 221, and common drain 230 can be Figure 1Corresponding examples of the first contact 150A, the second contact 150B, the first gate electrode 160A, the second gate electrode 160B, and the common drain region 170. In addition, to control the voltages applied to the gate electrodes 211 and 221, the bidirectional switch 200 further includes gate drivers 240 and 250. Specifically, the gate driver 240 controls the voltage applied to the gate electrode 211 of the HEMT 210 relative to the source contact 213 of the HEMT 210. In addition, the gate driver 250 controls the voltage applied to the gate electrode 221 of the HEMT 220 relative to the source contact 223 of the HEMT 220.

[0049] To give Figure 2 A brief example of the operation of the bidirectional switch 200, assume that a high voltage (e.g., +100 volts) is applied to the source contact 213 of the first HEMT 210, as shown by the ellipse 201. In addition, assume that a low voltage (e.g., ground) is applied to the source contact 223 of the second HEMT 220, as shown by the ellipse 202. In this case, the first HEMT 210 will act as the upstream HEMT and will thus operate in reverse conduction because the voltage at the source contact 213 will be sufficiently higher than the voltage at the common drain 230.

[0050] In addition, in this case, the second HEMT 220 will act as the downstream HEMT and will thus be able to operate in forward conduction when turned on because the voltage at the common drain 230 will be higher than the voltage at the source contact 223 of the second HEMT 220. Therefore, if the gate driver 250 applies a gate voltage greater than the threshold voltage of the second HEMT 220, current will be allowed to flow from the source contact 213 of the first HEMT 210 through the bidirectional switch 200 to the source contact 223 of the second HEMT 220. On the other hand, if the gate driver 250 applies a gate voltage less than the threshold voltage of the second HEMT 220, current flow through the bidirectional switch 200 will be blocked.

[0051] Of course, the two-way switch 200 is "two-way". If the source contact 223 of the second HEMT 220 is changed to have a high voltage applied thereto, and the source contact 213 of the first HEMT 210 is changed to have a low voltage applied thereto, the operation of the two-way switch 200 will be mirrored. In this case, the second HEMT 220 will act as the upstream HEMT, and the first HEMT 210 will act as the downstream HEMT. That is, if a gate voltage higher than the threshold voltage of the first HEMT 210 is applied to the gate driver 240, current will flow through the two-way switch 200 from the source contact 223 of the second HEMT 220 to the source contact 213 of the first HEMT 210. On the other hand, if a voltage less than the threshold voltage of the first HEMT 210 is applied to the gate driver 240, current flow through the two-way switch 200 will be blocked.

[0052] For illustrative purposes only, the above example describes the use of the two-way switch 200 with one terminal of the two-way switch 200 temporarily fixed at 100 volts and the other terminal of the two-way switch 200 temporarily fixed at ground. This is simply to keep the illustration of the operation of the two-way switch 200 simple. However, the two-way switch will also operate for rapidly fluctuating voltages. The HEMTs 210 and 220 will simply operate appropriately as upstream and downstream HEMTs at any given moment. Thus, the two-way switch 200 can be used to switch digital or analog signals.

[0053] Normally, the source contact of a HEMT is connected to the substrate such that the substrate and the source of the HEMT have the same voltage. However, in the case of a two-way switch, the substrate should be connected to the source of the downstream HEMT rather than the source of the upstream HEMT. Thus, a substrate biasing circuit can be used that actively switches the substrate to connect to the source of any one of the downstream HEMTs at any given time. For example Figure 3 A two-way switch 300 is shown, which includes Figure 2 an example of the two-way switch 200 of Figure 1 and a switching circuit 320 for biasing the substrate 310. For example, the substrate 310 can be Figure 2 the substrate 110 of Figure 3 For purposes of explanation,

[0054] In Figure 3In [the figure], the switch circuit 320 is configured to switch to connect the substrate 310 to either the source contact 213 or 223 having a lower voltage. For example, assume a higher voltage is applied to the source contact 213 of the first HEMT 210. In this case, the switch circuit 320 connects the other source contact 223 to the substrate 310. On the other hand, assume a higher voltage is applied to the source contact 223 of the second HEMT 220. In this case, the switch circuit 320 connects the other source contact 213 to the substrate 310.

[0055] Figure 4 A bidirectional switch 400 is shown, and the bidirectional switch 400 represents Figure 3 an example of the bidirectional switch 300 in [the figure], but shows the switch circuit 320 in more detail. For purposes of explanation, Figure 3 the elements of the bidirectional switch 300 in [the figure] are shown with the same element numbers in Figure 4 [the figure]. In Figure 4 [the figure], an example switch circuit 320 includes a sense amplifier 410 and a switch module 420. The sense amplifier 410 has a first sense amplifier input node 411 connected to the source contact 213 of the first HEMT 210, a second sense amplifier input node 412 connected to the source contact 223 of the second HEMT 220, and a sense amplifier output node 413 connected to the switch module 420. In operation, the sense amplifier 410 senses which of the source contact 213 and the source contact 223 has a higher voltage and outputs a signal representing the result. Then, based on the sense amplifier output signal, the switch module 420 then switches to connect the substrate 310 to the one of the source contact 213 or the source contact 223 having the lower voltage.

[0056] Thus, the sense amplifier 410 and the switch module 420 together provide a way by which the substrate can be consistently connected to the one of the source contact 213 or the source contact 223 to which a lower voltage is applied. Thus, consistent operation of the bidirectional switch can be achieved regardless of which source contact has a higher or lower voltage applied thereto.

[0057] Because the bidirectional switch according to the principles described herein uses HEMTs, the bidirectional switch can be used to control high voltages and currents. Thus, a large voltage difference between the source contact of the upstream HEMT and the gate electrode of the downstream HEMT may result in a large electric field peak in the channel layer on the side of the downstream gate electrode closer to the drain of the upstream HEMT. Such a large electric field peak may cause the bidirectional switch to degrade rapidly over time. Therefore, to help reduce the magnitude of the electric field peak, a field plate can be used in the bidirectional switch.

[0058] For example, Figure 5Shows a cross-sectional view of a bidirectional switch 500, which is an example of the bidirectional switch 100 of Figure 1 , but the first HEMT 101 (labeled 101' in Figure 5 ) includes field plates 511 to 513, and the second HEMT 102 (labeled 102' in Figure 5 ) includes field plates 514 to 516. The remaining elements of HEMT 101' are similar to those of HEMT 101 in Figure 1 , and thus have the reference numerals introduced in Figure 1 . Similarly, the remaining elements of HEMT 102' are similar to those of HEMT 102 in Figure 1 , and thus have the reference numerals introduced in Figure 1 . In the illustrated embodiment, there are six field plates 511 to 516 in the bidirectional switch 500, but the principle described herein is not limited to the number of field plates included in the bidirectional switch.

[0059] The field plates 511 to 516 are each disposed on the barrier layer 130. The field plates 511 to 513 are part of HEMT 101', while the field plates 514 to 516 are part of HEMT 102'. Since HEMT 101' and HEMT 102' are symmetric and mirror images of each other about the center of the common drain region 170, the field plates 511, 512, and 513 are identical in structure and function to the field plates 516, 515, and 514, respectively. As a side note, the region below the field plates 511 to 516 may be composed of a dielectric material that contributes to the structural stability and electrical isolation between the elements of the bidirectional switch 500.

[0060] In operation, to help mitigate the large electric field peak on the downstream gate electrode side closer to the upstream drain region, a bias (e.g., with a lower voltage from the source contact of the downstream HEMT) can be applied to the field plates of the downstream HEMT, while leaving the field plates of the upstream HEMT floating without any voltage bias. To describe one way of achieving this, it will be described in Figure 5 one after the other Figure 6 .

[0061] Figure 6 Shows a bidirectional switch 600, which is an example of the bidirectional switch 500 of Figure 5 , but shown in the form of a circuit structure. Figure 6 The bidirectional switch 600 of Figure 3 may include, for example, the elements of the bidirectional switch 300 of Figure 3 . Thus, for simplicity, Figure 6 the elements of the bidirectional switch 300 of Figure 5The HEMTs 101' and 102' include Figure 1 field plates not included in the HEMTs 101 and 102, so Figure 6 the HEMTs in Figure 6 are labeled as HEMT 210' and HEMT 220'. Specifically, Figure 5 the HEMT 210' is Figure 6 an example of the HEMT 101', while Figure 5 the HEMT 220' is

[0062] Figure 6 The bidirectional switch 600 also includes a field plate biasing circuit composed of a field plate control unit 610, a field plate 620, and a field plate 630. By way of example only, the field plate 620 may represent a single field plate or may represent a group of field plates of the first HEMT 210' (e.g., Figure 5 the field plates 511 to 513 of the first HEMT 101'). Similarly, the field plate 630 may represent a single field plate or may represent a group of field plates of the second HEMT 220' (e.g., Figure 5 the field plates 514 to 516 of the second HEMT 102').

[0063] In operation, as explained above with respect to Figure 3 when a higher voltage is applied to the source contact of the upstream HEMT and a lower voltage is applied to the source contact of the downstream HEMT, the switching circuit 320 connects the substrate 310 to the source contact of the downstream HEMT. Similarly, and roughly simultaneously, the field plate control unit 610 disconnects the field plate of the upstream HEMT from the source contact of the upstream HEMT and connects the field plate of the downstream HEMT to the source contact of the downstream HEMT. Thus, the field plate of the downstream HEMT can be biased with a lower voltage from the source contact of the downstream HEMT, thereby more effectively reducing the large electric field peak on the side of the downstream gate electrode closer to the upstream source contact.

[0064] In some embodiments, the field plate control unit 610 may instead connect the field plate of the downstream HEMT to a different voltage source such that the field plate of the downstream HEMT can be biased with a voltage different from the lower voltage from the source contact of the downstream HEMT. In one embodiment, the field plate of the downstream HEMT may instead be connected to the gate electrode of the downstream HEMT such that the field plate receives a biasing voltage from the gate electrode. In this case, the field plate closest to each gate electrode may be composed of the same material as the p-doped semiconductor portion (e.g., p-doped gallium nitride). In any case, Figure 5 and Figure 6 the bidirectional switch includes field plates that can be biased such that the electric field peak in the channel layer is reduced, thereby increasing the operating efficiency and lifespan of the bidirectional switch.

[0065] Return to Figure 3 the concept of the substrate bias circuit introduced in Figure 7 which shows another way to connect the substrate 310 to the source contact of the downstream HEMT. Specifically, Figure 7 a bidirectional switch 700 is shown, which is Figure 3 an example of the bidirectional switch 300 of , but shows an example of the switch circuit 320 in more detail. For the sake of brevity, Figure 3 the elements of the bidirectional switch 300 of Figure 7 are shown using the same element numbers in .

[0066] In Figure 7 the example switch circuit 320 includes resistors 710 and 720 and diodes 730 and 740. As Figure 7 shown, the resistor 710 is connected between the substrate 310 and the source contact 213 of the HEMT 210, and the resistor 720 is connected between the substrate 310 and the source contact 223 of the HEMT 220. Each of the resistors 710 and 720 can be a very large resistor (e.g., 500 kΩ to 1 MΩ) that maintains a low bias current.

[0067] In addition, the anodes of the diodes 730 and 740 are connected to the substrate 310, the cathode of the diode 730 is connected to the source contact 223 of the HEMT 220, and the cathode of the diode 740 is connected to the source contact 213 of the HEMT 210. As an example, the diodes 730 and 740 can be fast diodes, such as Schottky diodes (e.g., made of silicon carbide or gallium nitride). In addition, for the purpose of explanation, it is assumed that each of the diodes 730 and 740 has a forward bias threshold voltage of about 1 V. Therefore, when one of the diodes 730 or 740 conducts, there may be a voltage drop of about 1 V across that diode.

[0068] Note that in Figure 7 although not shown, the bidirectional switch 700 may also include a field plate and a field plate bias circuit as described in Figure 6 such as shown by the ellipses 701 and 702 in Figure 7 .

[0069] To give an example of the operation of the bidirectional switch 700, assume that a higher voltage is provided to the source contact 213 of the HEMT 210, and a lower voltage is provided to the source contact 223 of the HEMT 220. In this case, the diode 740 will be reverse-biased, thus preventing current from flowing from the source contact 213 to the substrate 310. However, the diode 730 will be forward-biased, and current will flow from the substrate 310 through the diode 730 and to the source contact 223 until the voltage of the substrate 310 (within the forward threshold voltage of the diode 730) approaches the voltage at the source contact 223.

[0070] On the other hand, assume that a higher voltage is provided to the source contact 223 of the HEMT 220, while a lower voltage is provided to the source contact 213 of the HEMT 210. In this case, the diode 730 will be reverse-biased, while the diode 740 will be forward-biased, thus making the voltage of the substrate 310 substantially the same as the voltage at the source contact 213. Therefore, Figure 7 the bidirectional switch 700 provides another way by which the substrate 310 can be biased with the voltage present at the source contact of any one of the downstream HEMTs. In this self-biasing circuit, each source of the HEMT has a low dynamic resistance of the diode 730 or 740.

[0071] However, the example of the switch circuit 320 shown can also be simplified. Figure 7 One way to implement the switch circuit 320 uses only one resistor and one diode, as Figure 8 shown. Figure 8 A bidirectional switch 800 is shown, which is an example of the bidirectional switch 700 of Figure 7 but in a simplified form. For the purpose of explanation, Figure 7 the elements of the bidirectional switch 700 of Figure 8 are shown using the same element numbers in

[0072] In Figure 8In this case, the example switch circuit 320 includes only a resistor 710 and a diode 730. The resistor 710 is connected between the substrate 310 and the source contact 213 of the HEMT 210. The anode of the diode 730 is connected to the substrate 310, and the cathode of the diode 730 is connected to the source contact 223 of the HEMT 220. As described above, when the source contact 213 is positive with respect to the source contact 223, the diode 730 conducts, and 223 is connected to the substrate 310, across which there is a diode voltage drop. However, when the source contact 223 is positive with respect to the source contact 213, the diode 730 is reverse-biased and no current flows through the resistor 710. Thus, except for a small voltage drop due to leakage current, the source contact 213 and the substrate 310 are at substantially the same potential. Under these conditions, the source contact 213 sees the resistance of the resistor 710. To explain the operation of the bidirectional switch 800, Figure 9 A signal diagram 900 is shown, which shows the waveforms at various positions in the bidirectional switch 800. The signal diagram 900 represents the operation of the bidirectional switch 800 when open.

[0073] Two signals 901 and 902 are shown, which show V Test and V sub voltage waveforms. The horizontal axis represents time passing from left to right. The vertical axis of each of the signals 901 and 902 represents the amplitude of the signal. The time is divided into four general time periods 911, 912, 913, and 914.

[0074] The signal 901 represents a sinusoidal test voltage V applied to the source contact 213 of the HEMT 210 Test (in volts). The source contact 223 of the HEMT 220 is at 0 volts. As Figure 9 shown, the sinusoidal test voltage V Test oscillates about 0 volts. Thus, in the signal diagram 900, the voltage at the source contact 213 oscillates between being lower than the voltage at the source contact 223 (e.g., during time periods 911 and 913) and being higher than the voltage at the source contact 223 (e.g., during time periods 912 and 914). Thus, during time periods 911 and 913, the HEMT 210 is the downstream HEMT and the HEMT 220 is the upstream HEMT. On the other hand, during time periods 912 and 914, the HEMT 220 is the downstream HEMT and the HEMT 210 is the upstream HEMT.

[0075] The signal 902 represents the substrate voltage V at the substrate 310 Sub (in volts). For purposes of explanation, each of the sinusoidal test voltage V Test and the substrate voltage V Sub is in Figure 8be marked at its corresponding position therein.

[0076] During time period 911, the sinusoidal test voltage VTest is negative. Thus, the voltage at source contact 213 is lower than the voltage at source contact 223, and HEMT 210 is the downstream HEMT. Additionally, upstream HEMT 220 is in the reverse conduction state. Also, diode 730 is reverse-biased and blocks current from flowing from source contact 223 to substrate 310. Since diode 730 is reverse-biased, substrate 310 becomes effectively connected to source contact 213 of HEMT 210 via resistor 710. Thus, during time period 911, the substrate voltage V Sub becomes approximately equal to the sinusoidal test voltage V at source contact 213 of downstream HEMT 210 Test .

[0077] At the start of time period 912, the sinusoidal test voltage V Test becomes positive. Thus, the voltage at source contact 213 is higher than the voltage at source contact 223, and at this time HEMT 220 is the downstream HEMT. Additionally, upstream HEMT 210 is in the reverse conduction state. Also, in this case, diode 730 is forward-biased and substrate 310 becomes effectively connected to source contact 223 of HEMT 220 via diode 730. Thus, during time period 912, the substrate voltage V Sub becomes approximately equal to the source voltage V at source contact 223 of downstream HEMT 220 S .

[0078] At the start of time period 913, the sinusoidal test voltage V Test becomes negative and the operation is the same as that described for time period 911. During time period 914, V test becomes positive and the operation is exactly the same as that described for time period 912.

[0079] Thus, the bidirectional switch according to the principles described herein allows a bidirectional switch in high-power applications while also allowing the bidirectional switch to have a small on-resistance and a compact size of a typical E-mode HEMT (such as an E-mode GaN HEMT). Additionally, the various embodiments of the bidirectional switch described herein allow for consistent substrate biasing, thus allowing for consistent and predictable operation of the bidirectional switch. Finally, the bidirectional switch also allows for biasing of the downstream field plate, thus reducing the peak electric field in the channel layer and allowing for reduced device degradation and increased lifetime.

[0080] Text support part

[0081] Clause 1. A bidirectional switch, comprising: a plurality of layers epitaxially grown on a substrate along a specific growth direction, the epitaxial layers including a channel layer and a barrier layer epitaxially grown on the channel layer, an interface between the barrier layer and the channel layer defining a heterojunction, the heterojunction inducing a two-dimensional electron gas (2DEG) in the channel layer, the 2DEG extending perpendicular to the epitaxial growth direction; a first contact, the first contact being an ohmic contact with a first portion of the 2DEG; a second contact, the second contact being an ohmic contact with a second portion of the 2DEG; a first gate electrode, the first gate electrode being disposed above the barrier layer and between the first contact and the second contact; and a second gate electrode, the second gate electrode being disposed above the barrier layer and between the first gate electrode and the second contact, the 2DEG between the first gate electrode and the second gate electrode defining a common drain region, such that a first high electron mobility transistor has the first contact as a source contact, the first gate electrode as a gate electrode, and the common drain region as a drain, and such that a second high electron mobility transistor has the second contact as a source contact, the second gate electrode as a gate electrode, and the common drain region as a drain, wherein the bidirectional switch includes the first high electron mobility transistor and the second high electron mobility transistor connected in series with the common drain region.

[0082] Clause 2. The bidirectional switch according to Clause 1, the bidirectional switch further comprising: a first gate driver configured to control the first high electron mobility transistor by applying a voltage to the first gate electrode relative to the first contact; and a second gate driver configured to control the second high electron mobility transistor by applying a voltage to the second gate electrode relative to the second contact.

[0083] Clause 3. The bidirectional switch according to Clause 1, the bidirectional switch further comprising: a first p-doped semiconductor portion located between the first gate electrode and the barrier layer such that when zero volts is applied to the first gate electrode, the 2DEG is discontinuous under the first gate electrode, such that the first high electron mobility transistor is a first enhancement-mode high electron mobility transistor; and a second p-doped semiconductor portion located between the second gate electrode and the barrier layer such that when zero volts is applied to the second gate electrode, the 2DEG is discontinuous under the second gate electrode, such that the second high electron mobility transistor is a second enhancement-mode high electron mobility transistor.

[0084] Clause 4. The two-way switch according to Clause 1, wherein the two-way switch further comprises a substrate biasing circuit, the substrate biasing circuit comprising: a substrate; and a switching circuit configured to disconnect the substrate from the first contact and connect the substrate to the second contact when the voltage on the first contact is higher than the voltage on the second contact, and the switching circuit is further configured to disconnect the substrate from the second contact and connect the substrate to the first contact when the voltage on the second contact is higher than the voltage on the first contact.

[0085] Clause 5. The two-way switch according to Clause 4, wherein the switching circuit comprises: a sense amplifier having a first input node in conductive contact with the first contact and a second input node in conductive contact with the second contact, the sense amplifier configured to generate a signal at an output node, the sense amplifier output signal depending on the voltages present at the first input node of the sense amplifier and the second input node of the sense amplifier; and a switching module driven by the sense amplifier output based on the sense amplifier output signal to connect the substrate to the first contact of the two-way switch or the second contact of the two-way switch.

[0086] Clause 6. The two-way switch according to Clause 1, wherein the two-way switch further comprises a field plate biasing circuit, the field plate biasing circuit comprising: a field plate control unit; a first field plate disposed above the barrier layer and the common drain region; and a second field plate disposed above the barrier layer and the common drain region and disposed perpendicular to the epitaxial growth direction between the first field plate and the second gate electrode.

[0087] Clause 7. The two-way switch according to Clause 6, further comprising a field plate control unit configured to: disconnect the first field plate from the first contact and connect the second field plate to the second contact when the voltage on the first contact is higher than the voltage on the second contact, and disconnect the second field plate from the second contact and connect the first field plate to the first contact when the voltage on the first contact is lower than the voltage on the second contact.

[0088] Clause 8. The two-way switch according to Clause 6, wherein the first field plate is connected to the first gate electrode.

[0089] Clause 9. The two-way switch according to Clause 8, wherein the first field plate is made of p-doped gallium nitride.

[0090] Clause 10. For the bidirectional switch described in Clause 6, the bidirectional switch further includes: a third field plate, which is disposed above the barrier layer and the common drain region along the epitaxial growth direction and is disposed between the first field plate and the second field plate perpendicular to the epitaxial growth direction; a fourth field plate, which is disposed above the barrier layer along the epitaxial growth direction and is disposed between the third field plate and the second field plate perpendicular to the epitaxial growth direction; a fifth field plate, which is disposed above the barrier layer along the epitaxial growth direction and is disposed between the third field plate and the fourth field plate perpendicular to the epitaxial growth direction; and a sixth field plate, which is disposed above the barrier layer along the epitaxial growth direction and is disposed between the fourth field plate and the fifth field plate perpendicular to the epitaxial growth direction.

[0091] Clause 11. For the bidirectional switch described in Clause 10, the distance between the third field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the first field plate and the barrier layer along the epitaxial growth direction, the distance between the fourth field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the second field plate and the barrier layer along the epitaxial growth direction, the distance between the fifth field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the third field plate and the barrier layer along the epitaxial growth direction, and the distance between the sixth field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the fourth field plate and the barrier layer along the epitaxial growth direction.

[0092] Clause 12. For the bidirectional switch described in Clause 10, the first field plate, the third field plate and the fifth field plate are electrically connected together, and the second field plate, the fourth field plate and the sixth field plate are electrically connected together.

[0093] Clause 13. For the bidirectional switch described in Clause 4, the switch circuit further includes: a resistor, which is connected between the first contact and the substrate; and a diode, which has an anode connected to the substrate and a cathode connected to the second contact.

[0094] Clause 14. For the bidirectional switch described in Clause 13, the resistor is a first resistor, the diode is a first diode, and the switch circuit further includes: a second resistor, which is connected between the substrate and the second contact; and a second diode, which has an anode connected to the substrate and a cathode connected to the first contact.

[0095] Clause 15. The bidirectional switch according to Clause 14, wherein both the first diode and the second diode are silicon carbide (SiC) Schottky diodes.

[0096] Clause 16. The bidirectional switch according to Clause 14, wherein both the first diode and the second diode are gallium nitride (GaN) diodes.

[0097] Clause 17. The bidirectional switch according to Clause 1, wherein the barrier layer is made of aluminum gallium nitride (AlGaN), and the channel layer is made of gallium nitride (GaN).

[0098] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the above-described features or acts, or the order of the above acts. On the contrary, these specifically described features and acts are disclosed as exemplary forms of implementing the claims.

[0099] The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. All changes within the meaning and range of equivalence of the claims are embraced within their scope.

[0100] When an element is introduced in the appended claims, the articles "a", "an", "the", and "said" are intended to mean that there is one or more of the element. The terms "comprising", "including", and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

Claims

1. A bidirectional switch, comprising: Several layers epitaxially grown on a substrate along a specific growth direction, the epitaxial layers comprising a channel layer and a barrier layer epitaxially grown on the channel layer, the interface between the barrier layer and the channel layer defining a heterojunction, the heterojunction inducing a two-dimensional electron gas (2DEG) in the channel layer, the 2DEG extending perpendicular to the epitaxial growth direction; a first contact, the first contact being an ohmic contact to a first portion of the 2DEG; a second contact, the second contact being an ohmic contact to a second portion of the 2DEG; a first gate electrode, the first gate electrode being disposed above the barrier layer and between the first contact and the second contact; and a second gate electrode, the second gate electrode being disposed above the barrier layer and between the first gate electrode and the second contact, the 2DEG between the first gate electrode and the second gate electrode defining a common drain region, so that the first high electron mobility transistor has the first contact as a source contact, the first gate electrode as a gate electrode, and the common drain region as a drain, and The second high electron mobility transistor has the second contact as a source contact, the second gate electrode as a gate electrode and the common drain region as a drain, wherein the bidirectional switch includes the first high electron mobility transistor and the second high electron mobility transistor connected in series with the common drain region.

2. The bidirectional switch according to claim 1, further comprising: a first gate driver configured to control the first high electron mobility transistor by applying a voltage to the first gate electrode relative to the first contact; and A second gate driver is configured to control the second high electron mobility transistor by applying a voltage to the second gate electrode with respect to the second contact.

3. The bidirectional switch according to claim 1, further comprising: a first p-doped semiconductor portion, the first p-doped semiconductor portion being located between the first gate electrode and the barrier layer such that when zero volts is applied to the first gate electrode, the 2DEG is discontinuous under the first gate electrode such that the first high electron mobility transistor is a first enhancement mode high electron mobility transistor; and A second p-doped semiconductor portion, the second p-doped semiconductor portion is located between the second gate electrode and the barrier layer, so that when zero volts is applied to the second gate electrode, the 2DEG is discontinuous under the second gate electrode, so that the second high electron mobility transistor is a second enhancement mode high electron mobility transistor.

4. The bidirectional switch according to claim 1, further comprising a substrate bias circuit, wherein the substrate bias circuit comprises: substrate; and a switch circuit configured to disconnect the substrate from the first contact and connect the substrate to the second contact when a voltage on the first contact is higher than a voltage on the second contact, The switch circuit is also configured to disconnect the substrate from the second contact and connect the substrate to the first contact when a voltage on the second contact is higher than a voltage on the first contact.

5. The bidirectional switch according to claim 4, wherein the switch circuit comprises: a sense amplifier having a first input node in conductive contact with the first contact, the sense amplifier also having a second input node in conductive contact with the second contact, the sense amplifier being configured to generate a signal at an output node, the sense amplifier output signal being dependent on voltages present at the first input node of the sense amplifier and the second input node of the sense amplifier; and A switch module is driven by a sense amplifier output based on the sense amplifier output signal to connect the substrate to the first contact of the bidirectional switch or the second contact of the bidirectional switch.

6. The bidirectional switch according to claim 1, further comprising a field plate bias circuit, wherein the field plate bias circuit comprises: Field board control unit; a first field plate, the first field plate being disposed above the barrier layer and the common drain region; and A second field plate is disposed above the barrier layer and the common drain region and between the first field plate and the second gate electrode perpendicular to the epitaxial growth direction.

7. The bidirectional switch according to claim 6, further comprising a field plate control unit, wherein the field plate control unit is configured as: When the voltage on the first contact is higher than the voltage on the second contact, disconnecting the first field plate from the first contact and connecting the second field plate to the second contact, and When the voltage on the first contact is lower than the voltage on the second contact, the second field plate is disconnected from the second contact, and the first field plate is connected to the first contact. The bidirectional switch of claim 6 , wherein the first field plate is connected to the first gate electrode. 9 . The bidirectional switch according to claim 8 , wherein the first field plate is made of p-doped gallium nitride.

10. The bidirectional switch according to claim 6, further comprising: a third field plate, the third field plate being disposed above the barrier layer and the common drain region along the epitaxial growth direction and disposed between the first field plate and the second field plate perpendicular to the epitaxial growth direction; a fourth field plate, the fourth field plate being disposed above the barrier layer along the epitaxial growth direction and disposed between the third field plate and the second field plate perpendicular to the epitaxial growth direction; a fifth field plate, the fifth field plate being disposed above the barrier layer along the epitaxial growth direction and disposed between the third field plate and the fourth field plate perpendicular to the epitaxial growth direction; as well as A sixth field plate is disposed above the barrier layer along the epitaxial growth direction and perpendicular to the epitaxial growth direction and between the fourth field plate and the fifth field plate.

11. The bidirectional switch according to claim 10, The distance between the third field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the first field plate and the barrier layer along the epitaxial growth direction. The distance between the fourth field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the second field plate and the barrier layer along the epitaxial growth direction. The distance between the fifth field plate and the barrier layer along the epitaxial growth direction is greater than the distance between the third field plate and the barrier layer along the epitaxial growth direction, and A distance between the sixth field plate and the barrier layer along the epitaxial growth direction is greater than a distance between the fourth field plate and the barrier layer along the epitaxial growth direction.

12. The bidirectional switch according to claim 10, The first field plate, the third field plate and the fifth field plate are electrically connected together, and The second field plate, the fourth field plate, and the sixth field plate are electrically connected together.

13. The bidirectional switch according to claim 4, wherein the switch circuit further comprises: a resistor connected between the first contact and the substrate; and A diode having an anode connected to the substrate and a cathode connected to the second contact.

14. The bidirectional switch according to claim 13, wherein the resistor is a first resistor, the diode is a first diode, and the switch circuit further comprises: a second resistor connected between the substrate and the second contact; and A second diode has an anode connected to the substrate, the second diode also having a cathode connected to the first contact. 15 . The bidirectional switch of claim 14 , wherein the first diode and the second diode are both silicon carbide (SiC) Schottky diodes. 16 . The bidirectional switch of claim 14 , wherein the first diode and the second diode are both gallium nitride (GaN) diodes. 17 . The bidirectional switch according to claim 1 , wherein the barrier layer is made of aluminum gallium nitride (AlGaN), and the channel layer is made of gallium nitride (GaN).

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