Enhanced AlGaN / GaN HEMT device

Abstract

The invention discloses an enhanced AlGaN / GaN HEMT (High Electron Mobility Transistor) device. The device comprises a gate electrode, a p-GaN layer, a source electrode, a passivation layer, a drain electrode, a barrier layer, a channel layer, a buffer layer, a nucleating layer, a substrate electrode and a super junction silicon substrate, the p-GaN layer is embedded into the passivation layer until the p-GaN layer is in contact with the upper surface of the barrier layer, the gate electrode is arranged right above the p-GaN layer, and the source electrode and the drain electrode are respectively connected with the barrier layer. According to the embodiment of the invention, the super junction type silicon substrate is used for replacing a conventional silicon substrate. Under the action of off-state drain electrode voltage stress, the depletion region is formed and extends in the super-junction silicon substrate, so that a part of off-state drain electrode voltage which should be dropped on the epitaxial layer of the device is dropped on the super-junction silicon substrate, thereby optimizing electric field concentration of a conventional enhanced AlGaN / GaN HEMT device in the vertical direction, and improving off-state withstand voltage of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to an enhanced AlGaN / GaN HEMT device. Background Art

[0002] GaN-on-Si power HEMT has excellent performance such as high off-state breakdown voltage, low on-resistance, high operating temperature and high operating frequency, and is one of the research hotspots in the field of semiconductor device technology today. In the production process of GaN-on-Si power HEMT, the heteroepitaxial process will inevitably introduce many defects and unintentional n-type doping impurities into the buffer layer of the device, resulting in the GaN material epitaxially grown on the silicon substrate being weakly n-type, and the device as a whole showing a large vertical leakage current from the substrate electrode to the drain electrode, which leads to a serious premature breakdown problem in GaN-on-Si power HEMT, hindering the further development of GaN-on-Si power HEMT. In practical applications, researchers often use buffer layer compensation doping technology to obtain a high-resistance buffer layer, thereby alleviating the premature breakdown problem. On the one hand, the compensating doping impurities in these buffer layers can act as acceptor defects to reduce the vertical leakage of the device and thus alleviate the problem of premature breakdown. On the other hand, when the device is subjected to external electrical stress, they will capture electrons, but cannot release the electrons immediately when the device is turned on, resulting in a large amount of residual negative charge in the buffer layer of the device. These residual negative charges will be electrically coupled with the channel layer, depleting part of the two-dimensional electron gas (2DEG) in the channel layer, thereby causing serious degradation of the output characteristics of the device, which is also called the current collapse problem caused by the defect capture effect of the buffer layer. Therefore, developing a device structure that can improve the off-state breakdown voltage of silicon-based gallium nitride power HEMT without worsening the current collapse problem caused by the defect capture effect in its buffer layer, and even inhibiting the defect capture effect in the device buffer layer, has become a technical focus that technicians in this field need to solve urgently. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides an enhanced AlGaN / GaN HEMT device, the device comprising:

[0004] Gate electrode, p-GaN layer, source, passivation layer, drain, barrier layer, channel layer, buffer layer, nucleation layer, substrate electrode and super junction silicon substrate;

[0005] The gate electrode is arranged directly above the p-GaN layer, the p-GaN layer is embedded in the passivation layer until it contacts the upper surface of the barrier layer, the source electrode and the drain electrode are respectively connected to the barrier layer, the channel layer is respectively connected to the barrier layer and the buffer layer, and the super junction silicon substrate is respectively connected to the nucleation layer and the substrate electrode.

[0006] Optionally, the super junction silicon substrate includes a p-type doped layer located directly above the substrate electrode 10, a lateral PN junction region located directly above the p-type doped layer, wherein the p-type doped layer is located on the left, the n-type doped layer is located on the right, and an n-type doped layer is located directly above the lateral PN junction region, and the upper surface of the n-type doped layer 124 is connected to the lower surface of the nucleation layer.

[0007] Optionally, the super junction silicon substrate has a thickness of 8 μm.

[0008] Optionally, the thickness of the p-type doping layer 121 in the superjunction silicon substrate is 0.5 μm, and the doping concentration is 1×10 18 cm -3 ~1×10 19 cm -3 .

[0009] Optionally, the thickness of the n-type doping layer 124 in the superjunction silicon substrate is 4.5 μm, and the doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 .

[0010] Optionally, the thickness of the n-type doped layer 122 in the superjunction silicon substrate is 3 μm, the width is half of the overall width of the device, and the doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 .

[0011] Optionally, the buffer layer material is Al 0.05 Ga 0.95 N, thickness is 2 μm, n-type doping concentration is 1×10 15 cm -3 .

[0012] Optionally, the distance between the gate electrode and the drain electrode is 8 μm.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. Compared with conventional enhancement-mode AlGaN / GaN HEMT devices, the embodiments of the present application use a superjunction silicon substrate instead of a conventional silicon substrate. When the off-state drain voltage stress acts, a depletion region is formed and extended in the superjunction silicon substrate, so that part of the off-state drain voltage that should have landed on the epitaxial layer of the device lands on the superjunction silicon substrate, thereby optimizing the electric field concentration of the conventional enhancement-mode AlGaN / GaN HEMT device in the vertical direction and improving the off-state withstand voltage of the device. 2. At the same time, the enhancement-mode AlGaN / GaN HEMT device provided in the embodiments of the present application has an almost identical output characteristic curve with the conventional enhancement-mode AlGaN / GaN HEMT device. This is because when the device is in the on state (the drain voltage and the gate voltage are both small), the vertical leakage current from the substrate electrode to the drain electrode inside the HEMT device is small, so the vertical leakage current has a small effect on the charge redistribution inside the device. Correspondingly, the superjunction substrate has a small effect on the charge distribution inside the device, especially near the channel layer. 3. Compared with conventional enhanced AlGaN / GaN HEMT devices, the enhanced AlGaN / GaN HEMT devices provided in the embodiments of the present application have a current collapse phenomenon caused by the optimized buffer layer defect capture effect. This is because, on the one hand, when the device is subjected to the negative voltage stress of the substrate electrode, the superjunction silicon substrate is depleted, and the fixed negative charge generated in the depletion region can be used as the end point of the electric field line from the substrate electrode, so that part of the substrate electrode voltage stress is shared on the superjunction substrate, thereby weakening the influence of the substrate electrode voltage stress on the electrical characteristics of the device buffer layer. On the other hand, when the negative voltage stress of the substrate electrode acts, most of the electrons captured in the device buffer layer come from the vertical leakage current from the substrate electrode to the drain electrode inside the device, and the introduction of the superjunction substrate effectively reduces the vertical leakage current of the device, thereby effectively curbing the electron supply source. In summary, the enhanced AlGaN / GaN HEMT devices provided in the embodiments of the present application have a current collapse phenomenon caused by optimized buffer layer defect capture. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 This is a schematic diagram of the structure of a conventional enhancement-mode AlGaN / GaN HEMT device;

[0017] Figure 2 It is a schematic diagram of the structure of an enhanced AlGaN / GaN HEMT device provided in an embodiment of the present application;

[0018] Figure 3 It is the off-state breakdown characteristic curve of enhanced AlGaN / GaN HEMT devices with different structures;

[0019] Figure 4 It is a graph showing the output characteristic curves of enhanced AlGaN / GaN HEMT devices with different structures;

[0020] Figure 5 It is a schematic diagram of the test waveform for measuring the current collapse phenomenon caused by the buffer layer defect trapping effect of enhanced AlGaN / GaN HEMT devices with different structures;

[0021] Figure 6 The output characteristic curves of enhanced AlGaN / GaN HEMT devices with different structures after being subjected to substrate electrode negative voltage stress of different magnitudes are measured, wherein Figure (a) is an output characteristic curve of a conventional enhanced AlGaN / GaN HEMT device after being subjected to substrate electrode negative voltage stress of different magnitudes, and Figure (b) is an output characteristic curve of the enhanced AlGaN / GaN HEMT device provided by the present invention after being subjected to substrate electrode negative voltage stress of different magnitudes;

[0022] Figure 7 It is a curve diagram showing the relationship between the normalized on-resistance (R / R0) of enhanced AlGaN / GaN HEMT devices with different structures and the magnitude of the negative voltage stress of the substrate electrode;

[0023] Figure numerals: gate electrode 1, p-GaN layer 2, source 3, passivation layer 4, drain 5, barrier layer 6, channel layer 7, buffer layer 8, nucleation layer 9, substrate electrode 10, super junction silicon substrate 12, conventional n-type doped silicon substrate 11, first p-type doped layer 121, first n-type doped layer 122, second p-type doped layer 123 and second n-type doped layer 124. Specific implementation methods

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Example

[0027] Conventional enhancement mode AlGaN / GaN HEMT devices such as Figure 1 As shown, the device includes a substrate electrode 10, an n-type doped silicon substrate 11, a nucleation layer 9, a buffer layer 8, a channel layer 7, a barrier layer 6 and a passivation layer 4 stacked from bottom to top, the p-GaN layer 2 is embedded in the passivation layer 4 until it contacts the upper surface of the barrier layer 6, the gate electrode 1 is arranged directly above the p-GaN layer, the source 3 and the drain 5 are arranged on both sides of the device, and form ohmic contacts with the barrier layer 6 respectively. The thickness of the n-type doped silicon substrate 11 is 8 μm, and the n-type doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 , the distance between the gate electrode and the drain electrode is 8μm.

[0028] The present invention provides an enhanced AlGaN / GaN HEMT device, such as Figure 2 As shown, it specifically includes: the same as the conventional enhanced AlGaN / GaN HEMT device, including source 3, drain 5, gate electrode 1, substrate electrode 10, passivation layer 4, p-GaN layer 2, barrier layer 6, channel layer 7, buffer layer 8 and nucleation layer 9. The difference is that the super junction silicon substrate 12 is used instead of Figure 1 The conventional n-type doped silicon substrate 11 is shown. The thickness of the superjunction silicon substrate 12 is 8 μm, and the thickness of the first p-type doped layer 121 in the superjunction silicon substrate 12 is 0.5 μm, and its doping concentration is 1×10 18 cm -3 ~1×10 19 cm -3 The thickness of the second p-type doped layer 123 in the superjunction silicon substrate 12 is 3 μm, the width is half of the overall width of the device, and the doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 The thickness of the first n-type doped layer 122 in the superjunction silicon substrate 12 is 3 μm, the width is half of the overall width of the device, and the doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 The thickness of the second n-type doping layer 124 in the superjunction silicon substrate 12 is 4.5 μm, and its doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 The buffer layer material is Al 0.05 Ga 0.95 N, with a thickness of 2 μm and an n-type doping concentration of 1×10 15 cm-3 .

[0029] Sentaurus TCAD semiconductor device simulation software was used to Figure 1 , Figure 2 The conventional enhanced AlGaN / GaN HEMT device shown and the enhanced AlGaN / GaN HEMT device provided in the embodiment of the present application are modeled and simulated to compare their off-state breakdown characteristics, output characteristics and current collapse characteristics caused by the defect capture effect in the buffer layer. In the simulation, the substrate electrode negative voltage stress test is used to characterize the current collapse characteristics caused by the defect capture effect in the buffer layer of the two devices. Figures 3 to 7 The simulation parameters in the simulation are set as follows: the n-type silicon substrate doping concentration of the conventional enhancement mode HEMT device is 1×10 16 cm -3 In an enhanced HEMT device provided in an embodiment of the present application, the doping concentration of the first p-type doping layer 121 is 1×10 19 cm -3 The doping concentration of the second p-type doping layer 123 is 1×10 16 cm -3 , the doping concentration of the first n-type doping layer 122 is 1×10 16 cm -3 The doping concentration of the second n-type doping layer 124 is 1×10 16 cm -3 .in, Figure 6 (a) is the output characteristic curve of a conventional enhanced AlGaN / GaN HEMT device after negative voltage stress of different sizes on the substrate electrode. Figure 6 (b) is a graph showing the output characteristic of the enhanced AlGaN / GaN HEMT device provided by the present invention after being subjected to substrate electrode negative voltage stress of different magnitudes.

[0030] like Figure 3 , 4 The off-state breakdown characteristic curve and output characteristic curve of the two devices are compared. Figure 3 and Figure 4In the figure, the horizontal axis is the drain voltage, the vertical axis is the drain current, and the other test conditions are shown in the legend. It can be seen from the simulation results that the enhanced AlGaN / GaN HEMT device provided in the embodiment of the present application has a significantly improved off-state withstand voltage, and its output characteristics are almost the same as those of the conventional enhanced AlGaN / GaN HEMT device. The reason for this result is that, on the one hand, under the off-state condition, the voltage-dividing effect of the superjunction substrate alleviates the vertical electric field concentration of the AlGaN / GaN HEMT. On the other hand, in the on-state, the vertical leakage in the device is small, so the substrate engineering design has little effect on the redistribution of charges inside the device, especially near the channel layer, resulting in the two devices having almost identical output characteristics.

[0031] like Figure 5 As shown in the figure, this figure is a schematic diagram of the test waveform of the current collapse characteristics caused by the buffer layer defect capture effect of the two devices. This test mainly characterizes the current collapse characteristics caused by the buffer layer defect capture effect in the two devices by applying negative voltage stress on the substrate electrode to the two devices. Before the stress begins, the static on-resistance of the two devices is measured first. During the stress stage, the gate, drain, and source of the device are grounded, and a negative voltage stress of the substrate electrode is applied to the device for a duration of t stress (Under this stress condition, most of the defect capture in the device occurs inside the buffer layer.) Then the stress is removed, an on-state pulse is applied to the device, and the output characteristic curve and on-resistance of the device after being subjected to stress are obtained. Finally, the following is summarized: Figure 6 The output characteristic curves of the two devices shown in FIG. 1 after negative voltage stress on the substrate electrode of different magnitudes is applied, as well as the output characteristic curves of the two devices shown in FIG. Figure 7 The normalized on-resistance R / R0 (R: on-resistance after stress; R0: static on-resistance) of the two devices shown in Figure 1 is related to the negative voltage stress V StressThe relationship diagram of the size of. It can be seen from the simulation results that the enhanced AlGaN / GaN HEMT device provided in the embodiment of the present application has significantly improved current collapse characteristics caused by the defect capture effect of the buffer layer. After the negative voltage stress of the substrate electrode with a magnitude of -500V and a duration of 1000S, the on-resistance of the conventional enhanced AlGaN / GaN HEMT device increased by 198%, while the on-resistance of the enhanced AlGaN / GaNHEMT device provided in the embodiment of the present application remained almost unchanged. There are two reasons for this result: on the one hand, under the negative voltage stress of the substrate electrode, the superjunction substrate is depleted, and the fixed negative charge generated by the depletion can serve as the end point of the electric field line from the substrate electrode, sharing part of the voltage of the substrate electrode, so that the effect of the substrate bias stress on the buffer layer is weakened. On the other hand, the introduction of the superjunction silicon substrate reduces the vertical leakage of the device, thereby weakening the supply of trapped electrons in the buffer layer. In summary, the superjunction silicon substrate reduces the number of electrons trapped in the buffer layer, which also reduces the number of residual negative charges in the buffer layer after the stress is removed. Correspondingly, the depletion effect of these negative charges on the two-dimensional electron gas is weakened, and thus the current collapse phenomenon caused by the defect capture effect of the buffer layer is suppressed.

[0032] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An enhanced AlGaN / GaN HEMT device, characterized in that: The device comprises: a gate electrode, a p-GaN layer, a source electrode, a passivation layer, a drain electrode, a barrier layer, a channel layer, a buffer layer, a nucleation layer, a substrate electrode and a super junction silicon substrate; The gate electrode is arranged directly above the p-GaN layer, the p-GaN layer is embedded in the passivation layer until it contacts the upper surface of the barrier layer, the source electrode and the drain electrode are respectively connected to the barrier layer, the channel layer is respectively connected to the barrier layer and the buffer layer, and the super junction silicon substrate is respectively connected to the nucleation layer and the substrate electrode.

2. The enhancement mode AlGaN / GaN HEMT device according to claim 1, characterized in that: The super junction silicon substrate includes a p-type doped layer located directly above the substrate electrode 10, a lateral PN junction region located directly above the p-type doped layer, wherein the p-type doped layer is located on the left, the n-type doped layer is located on the right, and the n-type doped layer is located directly above the lateral PN junction region, and the upper surface of the n-type doped layer 124 is connected to the lower surface of the nucleation layer.

3. The enhancement mode AlGaN / GaN HEMT device according to claim 2, characterized in that: The thickness of the super junction silicon substrate is 8 μm.

4. The enhancement mode AlGaN / GaN HEMT device according to claim 2, characterized in that: The thickness of the p-type doping layer 121 in the superjunction silicon substrate is 0.5 μm, and the doping concentration is 1×10 18 cm -3 ~1×10 19 cm -3 .

5. The enhancement mode AlGaN / GaN HEMT device according to claim 2, characterized in that: The thickness of the n-type doping layer 124 in the superjunction silicon substrate is 4.5 μm, and the doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 .

6. The enhancement mode AlGaN / GaN HEMT device according to claim 2, characterized in that: The thickness of the n-type doped layer 122 in the superjunction silicon substrate is 3 μm, the width is half of the overall width of the device, and the doping concentration is 1×10 15 cm -3 ~1×10 16 cm -3 .

7. The enhancement mode AlGaN / GaN HEMT device according to claim 2, characterized in that: The buffer layer material is Al 0.05 Ga 0.95 N, thickness is 2 μm, n-type doping concentration is 1×10 15 cm -3 .

8. The enhancement mode AlGaN / GaN HEMT device according to claim 2, characterized in that: The distance between the gate electrode and the drain electrode is 8 μm.

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