A variable resistor and equipment based on GaN devices

Abstract

The present application discloses a variable resistor and a device based on a GaN device, relating to the field of GaN devices. The variable resistor includes a channel layer, a barrier layer, two ohmic contact electrodes, and at least one current limiting electrode. The barrier layer is stacked on the channel layer, and the current limiting electrode is located on the barrier layer. The two ohmic contact electrodes are respectively located on both sides of the active region on the barrier layer, and at least one ohmic contact electrode is short-circuited with one current limiting electrode. The variable resistor is connected in series with a protected power device to form a device. When the current flowing through the device suddenly increases, the saturation voltage of the variable resistor is small, and the variable resistor first enters the saturation current region. Since the saturation current of the variable resistor is small, the overall current in the device is finally clamped at the saturation current of the variable resistor. The present application can reduce the saturation current density of the power device and improve the short-circuit ability.

Description

Technical Field

[0001] This application relates to the field of GaN devices, and particularly to a variable resistor and equipment based on GaN devices. Background Art

[0002] With the continuous development and progress of technology, the role of power devices has become increasingly prominent. In particular, wide bandgap semiconductor devices represented by silicon carbide and gallium nitride have superior characteristics such as high frequency, high efficiency, high power output, high voltage tolerance, high temperature tolerance, and radiation resistance.

[0003] The short-circuit (SC) capability is a key requirement for power switches in modern power electronics applications. Generally speaking, the short-circuit capability of wide bandgap semiconductor power devices is often lower than that of Si power devices of the same specifications. Taking SiC devices as an example, SiC MOSFETs have low on-resistance and high saturation current, and the smaller chip size results in faster temperature rise under short-circuit conditions, which shortens the short-circuit withstand time of the devices. Of course, the short-circuit capability of silicon-based semiconductor devices (such as Si IGBTs) also urgently needs to be improved.

[0004] To address the issue of the robustness of power devices, a common approach is to use an external protection circuit to detect short - circuit events occurring in the device and promptly cut off the device (D.-P. Sadik, J. Colmenares, G. Tolstoy, D. Peftitsis, M. Bakowski, J. Rabkowski, and H.-P. Nee, “Short - circuit protection circuits for silicon - carbide power transistors,” IEEE Trans. Ind. Electron., vol. 63, no. 4, pp. 1995 - 2004, Apr. 2016, doi: 10.1109 / TIE.2015.2506628.). However, this solution requires an additional protection circuit, and the delay time from detection to protection is inevitable. Another solution is to adopt an asymmetric trench structure (SiC MOSFET). The asymmetric trench structure and the adjacent p - well region will form a JFET region to reduce the peak short - circuit current (D. Peters, R. Siemieniec, T. Aichinger, T. Basler, R. Esteve, W. Bergner, and D. Kueck, “Performance and ruggedness of 1200V SiC—trench—MOSFET,” in Proc. 29th Int. Symp. Power Semiconductor Devices IC’s (ISPSD), Sapporo, Japan, May 2017, pp. 239 - 242, doi: 10.23919 / ISPSD.2017.7988904.). However, such a single - channel design will affect the on - resistance. Summary of the Invention

[0005] The objective of this application is to provide a variable resistor and equipment based on GaN devices, which can reduce the saturation current density of power devices and improve the short - circuit capability.

[0006] To achieve the above objective, this application provides the following solutions:

[0007] In a first aspect, this application provides a variable resistor based on GaN devices, including: a channel layer, a barrier layer, two ohmic contact electrodes, and at least one current - limiting electrode. The barrier layer is stacked on the channel layer, and the current - limiting electrode is located on the barrier layer; the two ohmic contact electrodes are respectively located on both sides of the active region on the barrier layer, and at least one ohmic contact electrode is short - circuited with one current - limiting electrode.

[0008] In a second aspect, the present application provides a device based on GaN devices, including: a protected power device and the variable resistor based on GaN devices described above. When only one ohmic contact electrode and one current limiting electrode in the variable resistor based on GaN devices are short-circuited, the ohmic contact electrode in the variable resistor based on GaN devices that is not short-circuited with the current limiting electrode is connected in series with the protected power device;

[0009] When one ohmic contact electrode and one current limiting electrode in the variable resistor based on GaN devices are short-circuited, and the other ohmic contact electrode and the other current limiting electrode are short-circuited, any one of the ohmic contact electrodes in the variable resistor based on GaN devices is connected in series with the protected power device.

[0010] According to the specific embodiments provided by the present application, the following technical effects are disclosed in the present application:

[0011] The present application provides a variable resistor and a device based on GaN devices. By providing two ohmic contact electrodes and at least one current limiting electrode on the barrier layer, at least one ohmic contact electrode is short-circuited with one current limiting electrode. When the voltage on the ohmic contact electrode that is not short-circuited with the current limiting electrode is small, the variable resistor operates in the linear region and is equivalent to a small resistor; as the voltage increases, the variable resistor enters the current saturation region, and its equivalent resistance value increases with the increase of the voltage, so it is equivalent to a large resistor with an adjustable resistance value, reducing the saturation current density of the power device and thus improving the short-circuit ability.

[0012] The variable resistor based on GaN devices in the present application is connected in series with the protected power device to form a device, and at least one current limiting electrode is not connected to the protected power device. When the protected power device accidentally short-circuits, the current flowing through the device suddenly increases. The saturation voltage of the variable resistor is small, and the variable resistor first enters the saturation current region. Since the saturation current of the variable resistor is small, the overall current in the device is finally clamped at the saturation current of the variable resistor, reducing the saturation current density of the power device and improving the short-circuit ability. Description of the Drawings

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0014] Figure 1 FIG. 21 is a cross-sectional structure diagram of a variable resistor based on GaN devices with a Schottky contact current limiting electrode provided in an embodiment of the present application;

[0015] Figure 2 Another structural cross-sectional view of a variable resistor of a GaN-based device with a Schottky contact current limiting electrode provided for another embodiment of the present application;

[0016] Figure 3 A structural cross-sectional view of a variable resistor of a GaN-based device with a MIS current limiting electrode structure provided for another embodiment of the present application;

[0017] Figure 4 Another structural cross-sectional view of a variable resistor of a GaN-based device with a MIS current limiting electrode structure provided for another embodiment of the present application;

[0018] Figure 5 A structural cross-sectional view of a variable resistor of a GaN-based device with a P-GaN current limiting electrode structure provided for another embodiment of the present application;

[0019] Figure 6 A structural cross-section of a variable resistor of a GaN-based device having both a first current limiting electrode and a second current limiting electrode provided for another embodiment of the present application;

[0020] Figure 7 A schematic diagram of a GaN-based device provided for an embodiment of the present application.

[0021] Symbol description:

[0022] Substrate - 1, buffer layer - 2, channel layer - 3, barrier layer - 4, first ohmic contact electrode - 5, second ohmic contact electrode - 6, first current limiting electrode - 7a, second current limiting electrode - 7b, first passivation layer - 8, second passivation layer - 8', third passivation layer - 8a, fourth passivation layer - 8b, fifth passivation layer - 8c, sixth passivation layer - 8d, P-GaN layer - 9. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0024] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0025] An embodiment of the present application provides a variable resistor based on a GaN device, including: a channel layer 3, a barrier layer 4, two ohmic contact electrodes, and at least one current limiting electrode. The barrier layer 4 is stacked on the channel layer 3, and the current limiting electrode is located on the barrier layer 4. The two ohmic contact electrodes are respectively located on both sides of the active region on the barrier layer 4, and at least one ohmic contact electrode is short-circuited with one current limiting electrode.

[0026] The variable resistor based on the GaN device of the present application is a depletion-type GaN device. Its working principle is as follows: When the voltage on the ohmic contact electrode not short-circuited with the current limiting electrode is small, the variable resistor operates in the linear region and is equivalent to a small resistor. As the voltage increases, the variable resistor enters the current saturation region, and its equivalent resistance value increases with the increase of the voltage, so it is equivalent to a large resistor with an adjustable resistance value.

[0027] In another exemplary embodiment of the present application, Figure 1 FIG. is a cross-sectional view of a structure of a variable resistor based on a GaN device with a Schottky contact current limiting electrode. When the number of current limiting electrodes is one, the current limiting electrode is short-circuited with one of the two ohmic contact electrodes. As Figure 1 shown, the two ohmic contact electrodes are the first ohmic contact electrode 5 and the second ohmic contact electrode 6 respectively, and the current limiting electrode is the first current limiting electrode 7a, and the first current limiting electrode 7a is short-circuited with the first ohmic contact electrode 5.

[0028] In another exemplary embodiment of the present application, based on the etching method, another structure of a variable resistor based on a GaN device with a Schottky contact current limiting electrode is provided, as Figure 2 shown. The only difference from the above embodiment is that a part of the barrier layer 4 in contact with the current limiting electrode is etched. Then the above current limiting electrode and the barrier layer 4 can be replaced by the following structure:

[0029] Etch the barrier layer 4 in the part in contact with the current limiting electrode, and the shape of the current limiting electrode matches the shape of the etched barrier layer 4.

[0030] This embodiment is compared with the variable resistor based on the GaN device with a Schottky contact current limiting electrode shown in the above Figure 1 In the case of this embodiment, a part of the barrier layer 4 is etched. After etching, the barrier layer is thinner, and the absolute value of the threshold voltage of the depletion-type GaN device is smaller. Compared with the unetched case, it will enter the current saturation region faster.

[0031] In another exemplary embodiment of the present application, as Figure 3As shown, a variable resistor based on a GaN device with a MIS current limiting electrode structure of a certain structure is provided, and a passivation layer with a certain thickness is reserved between the current limiting electrode and the barrier layer 4. That is, the variable resistor based on the GaN device further includes: a first passivation layer 8. The first passivation layer 8 is disposed between the current limiting electrode and the barrier layer 4.

[0032] The MIS current limiting electrode structure is also a current limiting electrode structure for forming a variable resistor based on a GaN device, and the effects described in this application can be achieved.

[0033] In another exemplary embodiment of the present application, a variable resistor based on a GaN device with a MIS current limiting electrode structure of another structure is further provided, as Figure 4 shown, the only difference from the variable resistor based on the GaN device with the MIS current limiting electrode structure shown above Figure 3 is that a part of the barrier layer 4 in contact with the current limiting electrode and the passivation layer thereunder is etched. That is, the variable resistor based on the GaN device further includes: a second passivation layer 8'. Etch the barrier layer 4 at the part in contact with the lower surface of the current limiting electrode; the lower surface shape of the second passivation layer 8' matches the shape of the etched barrier layer 4. The second passivation layer 8' is disposed between the current limiting electrode and the etched barrier layer 4.

[0034] This embodiment is compared with the variable resistor based on the GaN device with the MIS current limiting electrode structure shown above Figure 3 in that a part of the barrier layer 4 is etched, and compared with the unetched case, it will enter the saturation current region faster.

[0035] In another exemplary embodiment of the present application, in order to implement the function of the variable resistor, the variable resistor based on the GaN device can also be a variable resistor based on the GaN device with a P-GaN current limiting electrode structure. When there is a P-GaN layer 9 with a certain thickness between the current limiting electrode and the barrier layer 4, a variable resistor based on the GaN device with a P-GaN current limiting electrode structure is formed. The passivation layer can be divided into four parts, corresponding to 8a, 8b, 8c, and 8d respectively. As Figure 5 shown, the variable resistor based on the GaN device with a P-GaN current limiting electrode structure is the same as the above Figure 1The structure of the variable resistor of the GaN-based device with a Schottky contact current limiting electrode is different in that the variable resistor of the GaN-based device further includes: a P-GaN layer 9, a third passivation layer 8a, a fourth passivation layer 8b, a fifth passivation layer 8c, and a sixth passivation layer 8d. The P-GaN layer 9 is located on one side of the active region on the barrier layer 4; the third passivation layer 8a, the fourth passivation layer 8b, the fifth passivation layer 8c, and the sixth passivation layer 8d are all located on the barrier layer and are separated from each other; both ends of the fourth passivation layer 8b extend and overlap on the P-GaN layer 9 and the ohmic contact electrode on the same side as the P-GaN layer 9; both ends of the fifth passivation layer 8c extend and overlap on the P-GaN layer 9 and the ohmic contact electrode on the different side from the P-GaN layer 9; the current limiting electrode is matched and arranged on the third passivation layer 8a, the fourth passivation layer 8b, the fifth passivation layer 8c, the P-GaN layer 9, and the ohmic contact electrode on the same side as the P-GaN layer 9.

[0036] The third passivation layer 8a, the fourth passivation layer 8b, the fifth passivation layer 8c, and the sixth passivation layer 8d can be made of materials such as SiO2, Si3N4, etc.

[0037] This embodiment and the above Figures 1 to 4 Compared with the variable resistor of the GaN-based device shown above, the current limiting electrode of this embodiment has a P-GaN structure, and the P-GaN structure has the effect of depleting the two-dimensional electron gas. By reasonably controlling the doping concentration and thickness of the P-GaN structure, the effect of partially depleting the two-dimensional electron gas can be achieved. This makes the absolute value of the threshold voltage of the variable resistor of the GaN-based device smaller, so that it can enter the current saturation region faster.

[0038] Figures 1 to 5 The current limiting electrodes shown above are all the first current limiting electrode 7a, and the first current limiting electrode 7a is short-circuited with the first ohmic contact electrode 5.

[0039] In another exemplary embodiment of the present application, when the number of current limiting electrodes is two, both current limiting electrodes are located on the barrier layer 4 and are respectively located on both sides of the active region on the barrier layer 4; the current limiting electrodes located on the same side of the active region on the barrier layer 4 are short-circuited with the ohmic contact electrodes. Figure 6 Show the first ohmic contact electrode 5, the second ohmic contact electrode 6, the first current limiting electrode 7a, and the second current limiting electrode 7b. The first current limiting electrode 7a is short-circuited with the first ohmic contact electrode 5, and the second current limiting electrode 7b is short-circuited with the second ohmic contact electrode 6.

[0040] Figures 1 to 5 The variable resistors of the GaN-based device shown above can all include two current limiting electrodes and adopt Figure 6 the structure shown above.

[0041] In another exemplary embodiment of the present application, the variable resistor based on GaN devices in all of the above embodiments may further include: a substrate 1 and a buffer layer 2. The buffer layer 2, a channel layer 3, and a barrier layer 4 are sequentially stacked on the substrate 1. That is, the common structural part of the variable resistor based on GaN devices in all of the above embodiments is: the substrate 1 and the buffer layer 2, the channel layer 3, and the barrier layer 4 sequentially stacked on the substrate 1. The substrate 1 can be selected from Si substrate, SiC substrate, sapphire substrate, and GaN substrate, and its function is to reduce mechanical stress and provide support. The buffer layer 2 can be a combination of one or more of materials such as GaN, AlN, InGaN, AlGaN, InAlGaN, etc. The buffer layer 2 is used to reduce the off-state leakage current of the device and improve the breakdown voltage of the device, and it is a high-resistance layer. The channel layer 3 can be materials such as GaN, InGaN, AlGaN, InAlGaN, etc., and the channel layer 3 provides a conductive channel for the two-dimensional electron gas. The barrier layer 4 can be a combination of one or more of materials such as GaN, AlN, AlGaN, InGaN, InAlGaN, etc., and can provide a two-dimensional electron gas through the polarization effect. Both the two ohmic contact electrodes and the current limiting electrode are metal electrodes.

[0042] The embodiment of the present application also provides a device based on GaN devices, as Figure 7 shown, including: a protected power device and the variable resistor based on GaN devices described above. When only one ohmic contact electrode and one current limiting electrode in the variable resistor based on GaN devices are short-circuited, the ohmic contact electrode in the variable resistor based on GaN devices that is not short-circuited with the current limiting electrode is connected in series with the protected power device. When one ohmic contact electrode and one current limiting electrode in the variable resistor based on GaN devices are short-circuited, and the other ohmic contact electrode and the other current limiting electrode are short-circuited, any one of the ohmic contact electrodes in the variable resistor based on GaN devices is connected in series with the protected power device.

[0043] The variable resistor based on GaN devices proposed in the present application is connected in series with the protected power device to form a device combining a power device and the variable resistor based on GaN devices described in the present application. It becomes a power device with improved short-circuit capability.

[0044] The protected power device can be devices such as SiC MOSFET, Si IGBT, GaN HEMT, etc. If the protected power device is SiC MOSFET, connect the source electrode of the SiC MOSFET to an ohmic contact electrode in the variable resistor that is not short-circuited with the current limiting electrode. When the variable resistor is Figure 6When the structure shown is considered, the first ohmic contact electrode 5 is short-circuited with the first current limiting electrode 7a, and the second ohmic contact electrode 6 is short-circuited with the second current limiting electrode 7b. Then, either the first ohmic contact electrode 5 or the second ohmic contact electrode 6 is connected to the source of the SiC MOSFET. When a short circuit occurs in the protected power device and the current of the entire module (including the protected power device and the variable resistor based on the GaN device in this application) suddenly increases, the saturation voltage of this variable resistor is relatively small. Therefore, the variable resistor based on the GaN device proposed in this application enters the saturation state first, and the depletion layer expands until the channel where the two-dimensional electron gas is located is pinched off. Moreover, the saturation current of this variable resistor is relatively small. Thus, the current flowing through the entire module at this time is clamped in the saturation current of the variable resistor based on the GaN device. At this time, the variable resistor based on the GaN device in this application is equivalent to a current source. When the circuit operates normally, this depletion-mode GaN device operates in the linear current region and is equivalent to a small resistor. Therefore, the depletion-mode GaN device in this application is equivalent to a variable resistor, and the resistance changes with the voltage, achieving the effect of reducing the short-circuit current of the protected power device.

[0045] The variable resistor based on the GaN device proposed in this application is connected in series with other power devices, which can clamp the saturation current of the power device and achieve the purpose of improving the short-circuit ability of the power device.

[0046] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity in description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0047] In this article, specific examples are used to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application. At the same time, for those of ordinary skill in the art, according to the idea of this application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. An equipment based on GaN devices, characterized in that, Comprising: A protected power device and a variable resistor based on a GaN device; The variable resistor based on the GaN device is a depletion-mode GaN device; The variable resistor based on the GaN device includes: a channel layer, a barrier layer, two ohmic contact electrodes, and at least one current-limiting electrode; The barrier layer is stacked on the channel layer, and the current-limiting electrode is located on the barrier layer; the two ohmic contact electrodes are respectively located on both sides of the active region on the barrier layer; At least one ohmic contact electrode is short-circuited with one current-limiting electrode; When only one ohmic contact electrode and one current-limiting electrode in the variable resistor based on the GaN device are short-circuited, the ohmic contact electrode in the variable resistor based on the GaN device that is not short-circuited with the current-limiting electrode is connected in series with the protected power device; when the voltage on the ohmic contact electrode that is not short-circuited with the current-limiting electrode is small, the variable resistor operates in the linear region and is equivalent to a small resistor; as the voltage increases, the variable resistor enters the current saturation region, and the equivalent resistance value of the variable resistor increases with the increase of the voltage, so it is equivalent to a large resistor with an adjustable resistance value; When one ohmic contact electrode and one current-limiting electrode in the variable resistor based on the GaN device are short-circuited, and the other ohmic contact electrode and the other current-limiting electrode are short-circuited, any one of the ohmic contact electrodes in the variable resistor based on the GaN device is connected in series with the protected power device; when the protected power device is short-circuited and the current of the equipment suddenly increases, the variable resistor enters the saturation state first, and the current flowing through the equipment at this time is clamped in the saturation current of the variable resistor, and the variable resistor is equivalent to a current source at this time; when the circuit is working normally, the variable resistor operates in the linear current region and is equivalent to a small resistor.

2. The equipment based on GaN devices according to claim 1, characterized in that, When the number of current-limiting electrodes is one, the current-limiting electrode is short-circuited with one of the two ohmic contact electrodes.

3. The equipment based on GaN devices according to claim 1, wherein When the number of current-limiting electrodes is two, the two current-limiting electrodes are both located on the barrier layer and are respectively located on both sides of the active region on the barrier layer; The current-limiting electrode located on the same side of the active region on the barrier layer is short-circuited with the ohmic contact electrode.

4. The equipment based on GaN devices according to claim 1, wherein Etch the barrier layer in the part in contact with the current-limiting electrode, and the shape of the current-limiting electrode matches the shape of the etched barrier layer.

5. The equipment based on GaN devices according to claim 1, characterized in that, The variable resistor based on the GaN device further includes: a first passivation layer; The first passivation layer is disposed between the current-limiting electrode and the barrier layer.

6. The equipment based on GaN devices according to claim 1, characterized in that, The variable resistor based on the GaN device further includes: a second passivation layer; Etch the barrier layer in the part in contact with the lower surface of the current-limiting electrode; the lower surface shape of the second passivation layer matches the shape of the etched barrier layer; The second passivation layer is disposed between the current-limiting electrode and the etched barrier layer.

7. The equipment based on GaN devices according to claim 1, characterized in that, The variable resistor based on the GaN device further includes: a P-GaN layer, a third passivation layer, a fourth passivation layer, a fifth passivation layer, and a sixth passivation layer; The P-GaN layer is located on one side of the active region on the barrier layer; The third passivation layer, the fourth passivation layer, the fifth passivation layer, and the sixth passivation layer are all located on the barrier layer and are separated from each other; Both ends of the fourth passivation layer respectively extend and stack on the P-GaN layer and the ohmic contact electrode on the same side as the P-GaN layer; Both ends of the fifth passivation layer respectively extend and stack on the P-GaN layer and the ohmic contact electrode on the different side from the P-GaN layer; The current limiting electrode is arranged in a matching manner on the third passivation layer, the fourth passivation layer, the fifth passivation layer, the P-GaN layer and the ohmic contact electrode on the same side as the P-GaN layer.

8. The equipment based on GaN devices according to claim 1, characterized in that, The variable resistor based on the GaN device further includes: a substrate and a buffer layer; A buffer layer, a channel layer and a barrier layer are sequentially stacked on the substrate.

9. The equipment based on GaN devices according to claim 8, characterized in that, The substrate is one of an Si substrate, an SiC substrate, a sapphire substrate and a GaN substrate; The material of the buffer layer is one or more of GaN, AlN, InGaN, AlGaN and InAlGaN; The material of the channel layer is one or more of GaN, InGaN, AlGaN and InAlGaN; The material of the barrier layer is one or more of GaN, AlN, AlGaN, InGaN and InAlGaN; Both of the ohmic contact electrodes and the current limiting electrode are metal electrodes.

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