High-stability GaN bidirectional device

Abstract

The invention discloses a high-stability GaN bidirectional device which comprises a substrate and a transition layer, a buffer layer, a back barrier layer, a channel layer and a barrier layer which are sequentially stacked on the substrate, a first grid electrode and a second grid electrode are prepared on a first hole injection layer and a second hole injection layer respectively, and the first hole injection layer and the second hole injection layer are located on the barrier layer; the first source electrode and the second source electrode are prepared on the barrier layer in an ohmic contact mode and located on the two sides of the first hole injection layer and the second hole injection layer; the first source electrode, the first hole injection layer, the second hole injection layer and the second source electrode are isolated from one another through passivation layers; from the angle of energy band, the valence band top of the back barrier layer is lower than the valence band top of the channel layer, so that the hole is prevented from being injected into the substrate. The device has the functions of bidirectional conduction and bidirectional voltage resistance, can effectively inhibit a current collapse effect caused by a surface trap and a substrate effect, and has high dynamic stability and low dynamic conduction resistance; the substrate can be connected with any source electrode and can also be electrically suspended so as to improve the breakdown voltage of the device.

Description

Technical Field

[0001] The invention provides a GaN bidirectional device with high stability, belonging to the field of power electronic devices. Background Art

[0002] The device composed of two GaN devices connected in reverse series has the ability of bidirectional withstand voltage and bidirectional conduction. By overlapping the drain terminals of two GaN devices to form an integrated bidirectional device, the device area can be reduced and the on-resistance can be reduced at the same time (Morita, Tatsuo, et al. "650V 3.1mΩcm 2GaN-based monolithic bidirectional switch usingnormally-off gate injection transistor." 2007IEEE International Electron Devices Meeting. IEEE, 2007). However, for the integrated bidirectional device on the conventional GaN-on-Si epitaxial platform, connecting the integrated device substrate to any source terminal of the device or floating the substrate will cause the device to accumulate negative charges in the buffer layer after the high withstand voltage between the two sources in the off state, which increases the on-resistance of the device.

[0003] At present, a technology for actively switching the substrate connection position of a GaN bidirectional device according to its withstand voltage direction has been proposed (Bahl, Sandeep R., et al. "Bi-directional gallium nitride switch with self-managed substrate bias." US Patent Application No. 13 / 922,352. No. 13 / 922,352). This technology increases the circuit complexity by adding an additional control switch to switch the substrate connection. Summary of the invention

[0004] In order to suppress the dynamic resistance degradation caused by the substrate effect and realize a GaN bidirectional device with high stability and low current collapse effect, the present invention proposes a new GaN device structure, which has the functions of bidirectional conduction and bidirectional withstand voltage, and has an inhibitory effect on the current collapse effect. At the same time, the device has an electrically floating substrate, which enhances the withstand voltage capability of the device.

[0005] The technical solution of the present invention is as follows:

[0006] A GaN bidirectional device comprises a substrate and a transition layer, a buffer layer, a back barrier layer, a channel layer and a barrier layer stacked in sequence on the substrate, wherein a first gate and a second gate are respectively prepared on a first hole injection layer and a second hole injection layer, and the first hole injection layer and the second hole injection layer are located on the barrier layer; a first source electrode and a second source electrode are prepared on the barrier layer by using ohmic contacts, and are located on both sides of the first hole injection layer and the second hole injection layer; the first source electrode, the first hole injection layer, the second hole injection layer and the second source electrode are isolated from each other by a passivation layer; from the perspective of energy band, the valence band top of the back barrier layer is lower than the valence band top of the channel layer, thereby blocking holes from being injected into the substrate.

[0007] In the above-mentioned GaN bidirectional device, in the conventional GaN bidirectional device preparation process, an additional back barrier layer is inserted between the channel layer and the buffer layer, and the back barrier layer can be prepared by MOCVD (metal organic chemical vapor deposition) in epitaxial growth, and its thickness is 1-100nm, preferably 15-25nm. The material of the back barrier layer can be one or more of aluminum gallium nitride, aluminum nitride, indium nitride and aluminum indium gallium nitride.

[0008] like Figure 2 As shown, the basic principle of the above-mentioned GaN bidirectional device is demonstrated. When a positive bias is applied between the first gate G1 and the first source S1, or between the second gate G2 and the second source S2, the first hole injection layer P1 and the second hole injection layer P2 will inject holes into the back barrier layer and be blocked by the back barrier layer. At the same time, the holes will diffuse along the back barrier layer, thereby forming a hole conductive layer on the upper surface of the back barrier layer. The hole conductive layer can shield the negative charge in the buffer layer. In addition, the conductive layer can also shield the modulation effect of the substrate voltage on the two-dimensional electron gas, thereby suppressing the substrate effect.

[0009] In the above-mentioned GaN bidirectional device, the substrate can be a silicon substrate, a sapphire substrate, an aluminum nitride substrate, a silicon carbide substrate, etc. The transition layer is used to balance the lattice and stress mismatch in epitaxy, and can be made of aluminum nitride, gallium nitride, or a mixture of the two. The buffer layer is used to reduce the off-state leakage current of the device and increase the breakdown voltage of the device. It is a high-resistance layer and can be made of carbon- or iron-doped aluminum nitride, gallium nitride, or a mixture of the two. The channel layer provides a conductive channel for the two-dimensional electron gas, and its material is gallium nitride. The material of the barrier layer can be selected from one or more of aluminum gallium nitride, aluminum nitride, indium nitride, and aluminum indium gallium nitride, and a two-dimensional electron gas can be provided through the polarization effect. The material of the passivation layer can be at least one of dielectric materials such as aluminum oxide (Al2O3), silicon dioxide (SiO2), silicon nitride (SiN), aluminum nitride (AlN), and hafnium oxide (HfO2). The first and second hole injection layers are made of P-type doped semiconductors, which may be one or more of gallium nitride, aluminum gallium nitride, aluminum nitride, indium nitride, etc., and have a thickness of 1-400 nm, preferably 70-120 nm.

[0010] Furthermore, the GaN bidirectional device adds a P-type doped semiconductor thin layer next to the first hole injection layer and / or the second hole injection layer. The material of the P-type doped semiconductor thin layer can be one or more of gallium nitride, aluminum gallium nitride, aluminum nitride, indium nitride, etc. The longitudinal section of the P-type doped semiconductor thin layer can be a long strip, a trapezoid, etc. The thickness of the P-type doped semiconductor thin layer is 1-400nm, preferably 10-40nm, depending on different design requirements and preparation processes. When the device is turned on, the P-type doped semiconductor thin layer can also inject holes into the back barrier layer, increasing the injection layer area for injecting holes. At the same time, the movable holes in the P-type doped semiconductor thin layer can also shield surface traps, reducing the current collapse effect formed by the surface traps repelling the channel two-dimensional electron gas.

[0011] Furthermore, in the GaN bidirectional device, the first gate and the first source (or the second gate and the second source) of the device are short-circuited by interconnecting metal or other means to form a GaN device with bidirectional voltage resistance and unidirectional conduction capability.

[0012] The substrate of all the above device structures can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

[0013] Beneficial effects of the present invention:

[0014] The GaN bidirectional integrated device of the present invention can effectively suppress the current collapse effect caused by surface traps and substrate effects, so that the device has high dynamic stability and low dynamic on-resistance. At the same time, the substrate can be electrically floating, which can enhance the voltage resistance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a two-dimensional cross-sectional view of the first GaN bidirectional device structure proposed in the first embodiment of the present invention;

[0016] Figure 2 The basic principle of the device in the first embodiment is shown;

[0017] Figure 3 is a two-dimensional cross-sectional view of a second GaN bidirectional device structure proposed in the second embodiment of the present invention;

[0018] Figure 4 is a two-dimensional cross-sectional view of a third GaN bidirectional device structure proposed in Embodiment 3 of the present invention;

[0019] Figure 5 is a two-dimensional cross-sectional view of a fourth GaN bidirectional device structure proposed in Embodiment 4 of the present invention;

[0020] Figure 6 is a two-dimensional cross-sectional view of a fifth GaN bidirectional device structure proposed in Embodiment 5 of the present invention;

[0021] Figure 7 is a two-dimensional cross-sectional view of a sixth GaN bidirectional device structure proposed in Embodiment 6 of the present invention;

[0022] In the figure, G1 and G2 are gates, S1 and S2 are sources, P1 and P2 are hole injection layers, and P3 and P4 are P-type semiconductor thin layers. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and cannot be understood as limiting the present invention.

[0024] Embodiment 1: The first GaN bidirectional device structure in the present invention

[0025] like Figure 1As shown, the device structure includes a substrate, a transition layer, a buffer layer, a back barrier layer, a channel layer and a barrier layer, as well as a passivation layer, a field plate and other structures required in traditional HEMT devices. The source electrodes S1 and S2 are respectively prepared at the left and right ends of the gates G1 and G2 using ohmic contacts, and the gates G1 and G2 are respectively prepared on the hole injection layers P1 and P2, and the hole injection layers P1 and P2 are prepared on the barrier layer. According to the current preparation process, the hole injection layers P1 and P2 use P-type doped semiconductors, which can be gallium nitride, aluminum gallium nitride, aluminum nitride, indium nitride, etc. The substrate can be one or more of a silicon substrate, a sapphire substrate, aluminum nitride or silicon carbide. The transition layer is used to balance the lattice and stress mismatch in epitaxy, and can be aluminum nitride, gallium nitride or a mixture of the two. The buffer layer is used to reduce the off-state leakage current of the device and increase the breakdown voltage of the device. It is a high-resistance layer and can be doped with carbon or iron. Its material is aluminum nitride, gallium nitride or a mixture of the two. The back barrier layer can be a mixture of at least one or more of aluminum gallium nitride, aluminum nitride, indium nitride and aluminum indium gallium nitride. From the perspective of energy band, the valence band top of the back barrier layer is lower than the valence band top of the channel layer. The channel layer provides a conductive channel for the two-dimensional electron gas, and its material is gallium nitride. The barrier layer material can be a mixture of at least one or more of aluminum gallium nitride, aluminum nitride, indium nitride and aluminum indium gallium nitride, and can provide a two-dimensional electron gas through the polarization effect. The material of the passivation layer can be at least one of dielectric materials such as aluminum oxide (Al2O3), silicon dioxide (SiO2), silicon nitride (SiN), aluminum nitride (AlN), hafnium oxide (HfO2), etc. The isolation layer can be one of etching isolation or injection isolation or a mixture of the two. Injection isolation can use elements such as fluorine, nitrogen, and boron.

[0026] When the device is turned on, the hole injection layers P1 and P2 will inject holes into the back barrier layer and be blocked by the back barrier layer. At the same time, the holes will diffuse along the back barrier layer, thereby forming a hole conductive layer on the upper surface of the back barrier layer. Figure 2 As shown. The hole conductive layer can shield the negative charges in the buffer layer. Moreover, the hole conductive layer can also shield the modulation effect of the substrate voltage on the two-dimensional electron gas, thereby achieving the suppression effect on the substrate effect.

[0027] The device substrate can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

[0028] Embodiment 2: The second GaN bidirectional device structure in the present invention

[0029] The second GaN bidirectional device prepared in this embodiment is as follows Figure 3As shown, a section of P-type semiconductor thin layer P3 is added next to any hole injection layer P1 or P2, and the other structures are consistent with the first embodiment. The added P-type semiconductor thin layer increases the injection layer area for injecting holes into the back barrier layer when the device is turned on, further improving the device's ability to suppress substrate effects. At the same time, when the device is turned on, the movable holes in the P-type semiconductor thin layer P3 will shield the influence of the negative surface charges captured by the surface traps on the concentration of the two-dimensional electron gas in the channel, suppressing the current collapse effect caused by the surface traps, thereby achieving a more stable GaN bidirectional device.

[0030] The device substrate can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

[0031] Embodiment 3: The third GaN bidirectional device structure in the present invention

[0032] The third GaN bidirectional device prepared in this embodiment is as follows Figure 4 As shown, a section of P-type semiconductor thin layer P3 and P4 are added next to the two hole injection layers P1 and P2, respectively, and the other structures are consistent with the first embodiment. The added P-type semiconductor thin layer increases the injection layer area for injecting holes into the back barrier layer when the device is turned on, further improving the device's ability to suppress substrate effects. At the same time, when the device is turned on, the movable holes in P3 and P4 will shield the influence of the negative surface charges captured by the surface traps on the concentration of the two-dimensional electron gas in the channel, suppressing the current collapse effect caused by the surface traps, thereby achieving a more stable GaN bidirectional device.

[0033] The device substrate can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

[0034] Embodiment 4: The fourth GaN bidirectional device structure in the present invention

[0035] The fourth GaN bidirectional device prepared in this embodiment is as follows Figure 5 As shown, the gate G1 and source S1 (or gate G2 and source S2) of the GaN device of this example are connected by interconnecting metal or other means to form a GaN device with bidirectional voltage resistance and unidirectional conduction function. The other structures and effects of this example are consistent with those of the first embodiment. The interconnecting metal can be any conductive metal and is not the main innovation of the present invention.

[0036] The device substrate can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

[0037] Embodiment 5: The fifth GaN bidirectional device structure in the present invention

[0038] The fifth GaN bidirectional device prepared in this embodiment is as follows Figure 6As shown, the gate G1 and source S1 (or gate G2 and source S2) of the GaN device of this example are connected by interconnecting metal or other means to form a GaN device with bidirectional voltage resistance and unidirectional conduction function. The other structures and effects of this example are consistent with those of the second embodiment. The interconnecting metal can be any conductive metal and is not the main innovation of the present invention.

[0039] The device substrate can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

[0040] Embodiment 6: The sixth GaN bidirectional device structure in the present invention

[0041] The sixth GaN bidirectional device prepared in this embodiment is as follows Figure 7 As shown, the gate G1 and source S1 (or gate G2 and source S2) of the GaN device of this example are connected by interconnecting metal or other means to form a GaN device with bidirectional voltage resistance and unidirectional conduction function. The other structures and effects of this example are consistent with those of the third embodiment. The interconnecting metal can be any conductive metal and is not the main innovation of the present invention.

[0042] The device substrate can be connected to any source level; it can also be electrically floating to increase the device breakdown voltage.

Claims

1. A GaN bidirectional device, comprising a substrate and a transition layer, a buffer layer, a back barrier layer, a channel layer and a barrier layer stacked in sequence on the substrate, wherein a first gate and a second gate are respectively prepared on a first hole injection layer and a second hole injection layer, and the first hole injection layer and the second hole injection layer are located on the barrier layer; a first source and a second source are prepared on the barrier layer by ohmic contact, and are located on both sides of the first hole injection layer and the second hole injection layer; the first source, the first hole injection layer, the second hole injection layer and the second source are isolated from each other by a passivation layer; from the energy band perspective, the valence band top of the back barrier layer is lower than the valence band top of the channel layer, thereby blocking holes from being injected into the substrate.

2. The GaN bidirectional device according to claim 1, characterized in that: The back barrier layer is made of one or more materials selected from the group consisting of aluminum gallium nitride, aluminum nitride, indium nitride and aluminum indium gallium nitride.

3. The GaN bidirectional device according to claim 1, characterized in that: The substrate is a silicon substrate, a sapphire substrate, an aluminum nitride substrate or a silicon carbide substrate.

4. The GaN bidirectional device according to claim 1, characterized in that: The material of the transition layer is aluminum nitride and / or gallium nitride; the material of the buffer layer is carbon or iron doped aluminum nitride and / or gallium nitride; the material of the channel layer is gallium nitride; the material of the barrier layer is selected from one or more of aluminum gallium nitride, aluminum nitride, indium nitride and aluminum indium gallium nitride; the first hole layer and the second hole injection layer use P-type doped semiconductors, selected from one or more of gallium nitride, aluminum gallium nitride, aluminum nitride and indium nitride.

5. The GaN bidirectional device according to claim 1, characterized in that: A P-type doped semiconductor thin layer is added beside the first hole injection layer and / or the second hole injection layer.

6. The GaN bidirectional device according to claim 5, characterized in that: The material of the P-type doped semiconductor thin layer is one or more of gallium nitride, aluminum gallium nitride, aluminum nitride, and indium nitride.

7. The GaN bidirectional device according to claim 1, characterized in that: The first gate and the first source are short-circuited, or the second gate and the second source are short-circuited.

8. The GaN bidirectional device according to claim 7, characterized in that: The first gate and the first source, or the second gate and the second source, are short-circuited by interconnecting metal.

9. The GaN bidirectional device according to claim 5, characterized in that: The first gate and the first source are short-circuited, or the second gate and the second source are short-circuited.

10. The GaN bidirectional device according to claim 9, characterized in that: The first gate and the first source, or the second gate and the second source, are short-circuited by interconnecting metal.

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