A GaN / SiC cascode switching device with high temperature protection

Abstract

The present invention discloses a high-temperature protected GaN / SiC cascode switching device, comprising a high-voltage, low-frequency depletion-mode SiC JFET device, a low-voltage, high-frequency enhancement-mode GaN HEMT device, and a pyroelectric device connecting the SiC JFET and GaN HEMT devices and integrated and packaged on a common substrate. The pyroelectric device includes a spontaneously polarized pyroelectric composite material layer. The present invention utilizes the pyroelectric effect of the pyroelectric device, which is sensitive to temperature changes, and the heat generated by the cascode switching device when operating in a high-frequency, high-voltage, and high-current environment to prevent thermal runaway of the SiC JFET device in the cascode device or breakdown of the GaN HEMT device when the GaN / SiC cascode switching device shorts, thereby protecting the SiC JFET and GaN HEMT devices in the cascode switch in the circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power switching devices, and in particular to a GaN / SiC cascode switching device with high-temperature protection. Background Art

[0002] The rapid development of modern new energy technologies, as well as wireless power transmission systems and plasma generators, has placed higher demands on high-frequency electronic power converters. This has prompted power electronics engineers to explore new topologies, semiconductor devices, and packaging technologies to increase power density. Increasing the switching frequency reduces the energy stored in passive components, enabling smaller form factors. High-frequency and high-power converters require faster switching devices with low conduction losses, which is difficult to achieve using Si MOSFETs. Wide-bandgap (WBG) power devices, as third-generation semiconductors, offer low on-resistance, a wide operating temperature range, and can operate at high frequencies (HF, 3-30 MHz) and very high frequencies (VHF, 30-300 MHz). Gallium nitride high electron mobility transistors (GaN HEMTs) and silicon carbide junction field-effect transistors (SiC JFETs) are two commonly used WBG power devices, and their different characteristics lead to different target applications.

[0003] GaN HEMT devices have a small gate charge and are easy to drive at high frequencies. Since the GaN layer is epitaxially grown on other substrates (Si, SiC, or sapphire), the peak electric field appears on the surface of the lateral GaN device. The maximum electric field limitation of the lateral structure results in a relatively low rated voltage (<650V) in GaN HEMT devices, making them suitable for relatively low voltage and high frequency applications.

[0004] Unlike GaN HEMT devices, SiC JFET devices are vertical devices with higher voltage ratings (ranging from hundreds of volts to several kilovolts) than GaN HEMT devices. However, they have large gate charges and require high-power gate drivers, and these gate drive circuits are typically bulky and difficult to design. Therefore, SiC JFET devices are suitable for relatively high-voltage and low-frequency applications.

[0005] Recent research has shown that GaN HEMT devices have high output capacitance (C) in the HF and VHF ranges even under zero voltage switching (ZVS) conditions. oss ) loss, and these losses increase with the increase of dv / dt. Although SiC JFET devices have large gate charges, the C ossEnergy loss is not closely related to frequency, so GaN HEMT devices and SiC JFET devices are integrated in a cascode mode, combining the fast switching capability of GaN HEMT devices and the high-voltage blocking capability and low C of SiC JFET devices at high frequencies. oss Although, GaN / SiC cascode devices combine the advantages of GaN HEMT devices and SiC JFET devices, low voltage (LV) GaN HEMT devices are used for normally-off gate control, normally-on SiC JFET devices provide high voltage (HV) blocking capability, GaN / SiC cascode devices exhibit avalanche capability under high drain bias stress, negligible dynamic on-resistance (R on ) degradation and dynamic threshold voltage (V th ) drift to compensate for the shortcomings of GaN HEMTs, however, reliability and robustness are very important for power semiconductor devices used in industrial and automotive applications, especially under harsh operating conditions such as high temperature, short circuit (SC) and clampless inductive switching. Among them, short circuit events may occur due to unexpected conditions, such as SC on the load and faulty gate control signals in half-bridge configurations. During a short circuit event, the device operates in the saturation region with the on-state gate voltage, high drain-source voltage (V DS ) and high drain current (I D ). Generally speaking, short-circuit events impose extreme local thermal stress on the device. When GaN HEMT devices and SiC JFET devices are combined to operate the switch in a high-temperature and high-voltage field, the frequency of short-circuit events is further increased. Under short-circuit conditions, most of the power loss and heat are generated in the high-voltage SiC JFET device, and the SiC JFET device will experience thermal runaway, resulting in subsequent drain-source breakdown of the GaN HEMT device. Thermal runaway is caused by the positive feedback between the drain leakage current and the junction temperature in the corner of the area where there is no top Al layer (source pad) in the SiC JFET device. Once the GaN HEMT / SiC JFET cascode device short-circuits, the I D The waveform shows the turning point in the on-state and the tail current in the biased state. The SiC JFET device (V th,SiC ) sharply decreases, resulting in a high transient V DS , which will damage the GaN devices in the cascode device. Summary of the Invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a high-temperature protected GaN / SiC cascode switching device, which utilizes the pyroelectric effect of pyroelectric materials to better absorb the heat generated during operation of the cascode GaN / SiC switching device, thereby solving the breakdown problem of the GaN device in the cascode device.

[0007] Technical solution: The high-temperature protected GaN / SiC cascode switching device described in the present invention includes a high-voltage, low-frequency depletion-mode SiC JFET device, a low-voltage, high-frequency enhancement-mode GaN HEMT device, and a pyroelectric device that connects the SiC JFET device and the GaN HEMT device and is integrated and packaged on the same substrate; wherein the pyroelectric device includes a spontaneously polarized pyroelectric composite material layer.

[0008] Preferably, the pyroelectric device further comprises a first graphene electrode, a second graphene electrode, and a first aluminum electrode and a second aluminum electrode, which are arranged on the upper side of the pyroelectric composite material layer and on the lower side, and the first graphene electrode and the second graphene electrode and the first aluminum electrode and the second aluminum electrode are conductively isolated by a silicon dioxide insulating layer.

[0009] Preferably, the pyroelectric composite material layer is a polyvinylidene fluoride-trifluoroethylene copolymer composite material layer.

[0010] Preferably, the polyvinylidene fluoride-trifluoroethylene copolymer composite material is a [P(VDF / TrFE) (80 / 20)] polymer composite material having a Curie temperature of 135°C.

[0011] Preferably, the SiC JFET device includes a SiC JFET device drain, a SiC JFET device gate, and a SiC JFET device source arranged on the first surface; the GaN HEMT device includes a GaN HEMT device drain, a GaN HEMT device gate, and a GaN HEMT device source arranged on the first surface; the SiC JFET device drain is connected to an external circuit of a GaN / SiC cascode switching device, the SiC JFET device gate is electrically connected to the GaN HEMT device source, and the SiCJFET device source is electrically connected to the GaN HEMT device drain; the SiC JFET device gate is electrically connected to a first graphene electrode, and the SiC JFET device source is electrically connected to a first aluminum electrode; the GaN HEMT device gate is electrically connected to a second graphene electrode and to an external gate voltage control circuit; the GaN HEMT device source is electrically connected to the second aluminum electrode and to an external circuit of the GaN / SiC cascode switching device.

[0012] Preferably, a closed sub-loop is formed between the second graphene electrode, the second aluminum electrode, the gate of the GaN HEMT device, and the source of the GaN HEMT device; when the temperature change rate of the pyroelectric device dT / dt=0.5°C / s is greater than zero, two voltage sources with opposite polarities are formed between the pyroelectric open-circuit voltage and the gate of the GaN HEMT device and the source of the GaN HEMT device, and the gate-source voltage V GS,GaN <V th,GaN , the GaN HEMT device is in the off state, and the SiC JFET device is in the on state.

[0013] Preferably, a closed sub-loop is formed between the first graphene electrode, the first aluminum electrode, the gate of the SiC JFET device, and the source of the SiC JFET device; when the temperature change rate of the pyroelectric device dT / dt=0.8°C / s is greater than zero, two voltage sources with opposite polarities are formed between the pyroelectric open-circuit voltage and the gate of the SiC JFET device and the source of the SiC JFET device, and the gate-source voltage V GS,SiC <V th,SiC , the SiC JFET device is in the off state, and the GaN HEMT device is in the off state.

[0014] A circuit includes a GaN / SiC cascode switching device.

[0015] The working principle of the GaN / SiC cascode switch device of the present invention is:

[0016] Pyroelectric materials, a key subclass of piezoelectric materials, have attracted increasing attention due to their unique pyroelectric effect, which arises from spontaneous polarization. These materials exhibit broad application prospects due to their diverse electrical responses to time-dependent temperature fluctuations. The pyroelectric effect refers to the change in spontaneous polarization caused by temperature fluctuations in some polar materials. It is well known that pyroelectric materials can convert thermal energy into electrical energy through changes in their internal spontaneous polarization. The pyroelectric electrical response is caused by the oscillation of electric dipoles within the pyroelectric material, which is induced by time-dependent temperature fluctuations. The superposition of many electric dipoles forms a spontaneous polarization (Ps) perpendicular to the plane of the pyroelectric material. This stable spontaneous polarization within the pyroelectric material attracts nearby free particles with positive or negative charges. When the surface of a pyroelectric material is covered by two conductive electrodes, the spontaneous electric field within the pyroelectric material, due to electrostatic induction, induces equal charges of opposite polarity on the two electrodes through an external circuit. When the temperature change rate of the pyroelectric material increases (dT / dt>0), the oscillation of the electric dipole increases, which weakens the spontaneous polarization and drives the electrons released from the surface electrode of the pyroelectric material to migrate in the external circuit and reach a new electrostatic equilibrium state. Similarly, when dT / dt<0, it strengthens the spontaneous polarization and breaks the electrostatic equilibrium again, causing electrons to migrate in the opposite direction in the external circuit. In this patented invention, a high-voltage depletion-mode SiC JFET device die is innovatively packaged on the same substrate in a cascode configuration with a low-voltage enhancement-mode GaN HEMT device die and a pyroelectric device made of a specific pyroelectric material. An adhesive is used inside the switch device package to tightly bond the pyroelectric device, the enhancement-mode GaN HEMT device, and the depletion-mode SiC JFET device together. This allows the pyroelectric device to better absorb the heat generated by the cascode GaN / SiC switch device during operation, thereby utilizing the pyroelectric effect of the pyroelectric material to solve the breakdown problem of the GaN HEMT device in the cascode device.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following outstanding advantages:

[0018] 1. The GaN / SiC cascode high-frequency power switch device of the present invention utilizes the pyroelectric effect of the pyroelectric device, which is sensitive to temperature changes, and the heat generated by the cascode switch itself when operating in a high-frequency, high-voltage, and high-current environment to prevent thermal runaway of the SiC JFET device in the cascode device or breakdown of the GaN HEMT device when the GaN / SiC cascode switch device is short-circuited, thereby protecting the SiC JFET device and GaN HEMT device in the cascode switch in the circuit.

[0019] 2. In the GaN / SiC cascode high-frequency power switching device of the present invention, pyroelectric materials are combined with semiconductor power devices to form a temperature-sensitive power switching device. When the temperature of the power switching device suddenly and sharply increases, the threshold voltage of the device itself is increased, thereby disconnecting the external circuit of the switch to achieve protection of the switching device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the equivalent circuit structure of the switching device of the present invention;

[0021] Figure 2 for Figure 1 When dT / dt=0, the spontaneous polarization (P s ) Schematic diagram;

[0022] Figure 3 for Figure 1 When dT / dt>0, the electric dipole oscillation in the pyroelectric material is enhanced. Schematic diagram of the GaN HEMT device turning off in the cascode switch;

[0023] Figure 4 is a schematic diagram showing the change of the open circuit voltage generated by the pyroelectric device of the present invention over time;

[0024] Figure 5 Schematic diagram of the pyroelectric effect principle of the pyroelectric composite material layer of the present invention (a is the pyroelectric effect principle diagram; b is the current direction diagram when dT / dt>0; c is the charge distribution diagram when dT / dt=0; d is the current direction diagram when dT / dt<0);

[0025] Figure 6 Schematic diagram of the equivalent circuit of the cascode switch when the GaN HEMT device is turned off when dT / dt>0;

[0026] Figure 7 When dT / dt>>0, the oscillation of the electric dipole of the pyroelectric material further increases, and the SiC JFET device and GaN HEMT device in the cascode switch device are simultaneously turned off.

[0027] Figure 8 Schematic diagram of the equivalent circuit at the switch when both the SiC JFET device and the GaN HEMT device are off when dT / dt>>0;

[0028] Figure 9 It is a schematic flow chart of an embodiment of a cascode switching device of the present invention.

[0029] Reference numerals:

[0030] 1. SiC JFET device; 11. SiC JFET device drain; 12. SiC JFET device gate; 13. SiC JFET device source;

[0031] 2. Pyroelectric device; 21. Pyroelectric composite material layer; 22. First graphene electrode; 23. Second graphene electrode; 24. First aluminum electrode; 25. Second aluminum electrode; 26. Silicon dioxide insulating layer;

[0032] 3. GaN HEMT device; 31. GaN HEMT device drain; 32. GaN HEMT device gate; 33. GaN HEMT device source;

[0033] 4. External gate voltage control circuit. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1-9 , clearly and completely describing the technical solutions of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by ordinary technicians in this field fall within the scope of protection of the present invention.

[0035] like Figure 1As shown, a high-temperature protected GaN / SiC cascode switch device of the present invention includes a high-voltage, low-frequency depletion-mode SiC JFET device 1, a low-voltage, high-frequency enhancement-mode GaN HEMT device 3, and a pyroelectric device 2 connecting the SiC JFET device 1 and the GaN HEMT device 3 and integratedly packaged on the same substrate; wherein the pyroelectric device 2 includes a pyroelectric composite material layer 21 with spontaneous polarization; specifically, the pyroelectric composite material layer 21 is a polyvinylidene fluoride-trifluoroethylene copolymer composite material layer, more specifically, the polyvinylidene fluoride-trifluoroethylene copolymer is a [P(VDF / TrFE)(80 / 20)] polymer with a Curie temperature of 135°C, and the [P(VDF / TrFE)(80 / 20)] polymer composite material can be purchased from relevant companies, such as Kunshan Hisense Electronics Co., Ltd. The pyroelectric device 2 further includes a first graphene electrode 22 and a second graphene electrode 23 disposed on the upper side of the pyroelectric composite material layer 21, and a first aluminum electrode 24 and a second aluminum electrode 25 disposed on the lower side. The first graphene electrode 22 and the second graphene electrode 23, as well as the first aluminum electrode 24 and the second aluminum electrode 25, are electrically isolated by a silicon dioxide insulating layer 26. The first graphene electrode 22 and the second graphene electrode 23 are screen-printed using an ATMA at-25pa (USA) screen printing device at a constant pressure and a scraper speed of 220 mm / s (scraper material: Shore A). 70A0605) is prepared by screen printing graphene ink on a flat plate of a [P(VDF / TrFE)(80 / 20)] pyroelectric composite material layer 22. The first graphene electrode 22 and the second graphene electrode 23 produced by screen printing have a uniform thickness of 9 μm. In order to keep the graphene electrode film active, the ratio of the [P(VDF / TrFE)(80 / 20)] material layer to the graphene electrode thickness is set to 5.8 (52 / 9), that is, the thickness of the pyroelectric material [P(VDF / TrFE)(80 / 20)] used is 52 μm, the thickness of the graphene electrode is 9 μm, and the surface area is 2×2 mm 2 The first aluminum electrode 24 and the second aluminum electrode 25 are obtained by using 200nm thick electron beam vapor deposition (Edwards FL-400) of metal aluminum ions; on the basis of the first graphene electrode 22, the second graphene electrode 23 and the first aluminum electrode 24, the second aluminum electrode 25 of the pyroelectric device 2, an area of ​​0.2×2mm is etched in the center position between the first graphene electrode, the second graphene electrode and the first aluminum electrode, the second aluminum electrode toward the pyroelectric composite material layer 21 by ion beam etching. 2 , a rectangular groove with a thickness of 18 μm was then formed by controlling the deposition temperature at 120 °C and the deposition rate at / min, a low-temperature plasma-enhanced chemical vapor deposition (PECVD) method was used to deposit a 0.2×2mm thick rectangular groove etched in the direction of the graphene electrode toward the pyroelectric material. 2 , a SiO2 film with a thickness of 18μm is deposited in a rectangular groove etched in the direction of the aluminum electrode toward the pyroelectric material with an area of ​​0.2×2mm 2 , a SiO2 film with a thickness of 18 μm, the deposited SiO2 film is used as the silicon dioxide insulating layer 26 for the conductive insulating layer of the first graphene electrode and the second graphene electrode, and the first aluminum electrode and the second aluminum electrode respectively.

[0036] The principle of adding the silicon dioxide insulating layer 26 between the first graphene electrode, the second graphene electrode and the first aluminum electrode, the second aluminum electrode of the pyroelectric device 2 is as follows: if there is no silicon dioxide insulating layer between the first graphene electrode, the second graphene electrode and the first aluminum electrode, the second aluminum electrode, the depletion mode SiC JFET device gate 12 and the enhancement mode GaN HEMT device gate 32 will be connected together through the graphene electrode, the depletion mode SiC JFET device source 13 and the enhancement mode GaN HEMT device source 33 will be connected together through the aluminum electrode, and the depletion mode SiC JFET device source 13 and the enhancement mode GaN HEMT device drain 31 will be connected. In this case, it is equivalent to a direct short circuit between the enhancement mode SiC JFET device drain and the enhancement mode GaN HEMT device source. The above two connection methods are not desirable for cascode GaN HEMT devices and SiC JFET devices. Therefore, the main function of the silicon dioxide insulating layer here is to prevent the depletion mode SiC JFET device gate and the enhancement mode GaN The gate of the HEMT device is shorted to prevent shorting between the drain and source of the enhancement-mode GaN, thereby ensuring the normal operation of the internal equivalent circuit of the GaN / SiC cascode switch device. Furthermore, a silicon dioxide insulating layer is added between the first and second graphene electrodes and the first and second aluminum electrodes, so that half of the pyroelectric composite material layer of the pyroelectric device is connected to the depletion-mode SiC JFET device through the first graphene electrode and the first aluminum electrode, and the other half is connected to the enhancement-mode GaN HEMT device through the second graphene electrode and the second aluminum electrode. The pyroelectric composite material layer of the pyroelectric device senses the same temperature changes of the two devices, which is equivalent to dividing the pyroelectric device 2 into two small pyroelectric devices, which simultaneously control the shutdown of the SiC JFET device and the GaN HEMT device.

[0037] The SiC JFET device 1 includes a SiC JFET device drain 11, a SiC JFET device gate 12, and a SiC JFET device source 13 arranged on the first surface; the GaN HEMT device 3 includes a GaN HEMT device drain 31, a GaN HEMT device gate 32, and a GaN HEMT device source 33 arranged on the first surface; the SiC JFET device drain 11 is connected to the GaN / SiC cascode switch device external circuit, the SiC JFET device gate 12 is electrically connected to the GaN HEMT device source 33, and the SiC JFET device source 13 is electrically connected to the GaN HEMT device drain 31; the SiC JFET device gate 12 is electrically connected to the first graphene electrode 22, and the SiC JFET device source 13 is electrically connected to the first aluminum electrode 24; the GaN HEMT device gate 32 is electrically connected to the second graphene electrode 23, and is also electrically connected to the external gate voltage control circuit 4; the GaN The HEMT device source 33 is electrically connected to the second aluminum electrode 25 and is also connected to an external circuit of the GaN / SiC cascode switching device.

[0038] The implementation method of the high temperature protection GaN / SiC cascode switch device of the present invention is as follows: Figure 9 The workflow shown is:

[0039] like Figure 1 As shown, the GaN / SiC cascode switch device is manufactured and packaged according to the process requirements. The drain electrode 11 of the SiC JFET device and the source electrode 33 of the GaN / SiC cascode switch device are electrically connected to the external circuit respectively to complete the circuit connection. The external gate voltage control circuit 4 applies a uniformly varying drive signal to the gate electrode 32 of the GaN HEMT device. When the gate-source voltage applied to the GaN HEMT device 3 reaches 2V, the gate-source voltage of the depletion-mode SiC JFET device 1 reaches -7V in a very short time and is turned on.

[0040] like Figure 2 As shown in the figure: when the GaN / SiC cascode switch device starts to work in the circuit, multiple electric dipoles in the pyroelectric device 2 are superimposed to form a spontaneous polarization (P) perpendicular to the plane of the pyroelectric composite material layer 21. s ), spontaneous polarization (P s ) direction is from the first aluminum electrode 24, the second aluminum electrode 25 to the first graphene electrode 22, the second graphene electrode 23; at this time, the stable spontaneous polarization inside the pyroelectric composite material layer 21 attracts nearby free particles with positive or negative charges; when the surface of the pyroelectric composite material layer 21 is covered with two conductive electrodes, the spontaneous electric field inside the pyroelectric composite material layer 21 induces equal charges of opposite polarities on the two electrodes through an external circuit based on electrostatic induction;

[0041] As GaN / SiC cascode switching devices operate in a high-frequency and high-voltage environment, a large leakage current I flows through the switching device. D , according to the heat generation formula Q in physical electricity t =UIt=I 2 Rt, the common source and common gate switching device will generate a certain amount of heat Q as the circuit operation time t changes. t , where I is the leakage current flowing through the cascode switching device, and R is the on-resistance of the cascode switching device;

[0042] like Figure 3 As shown, the heat generated by the cascode switching device will be absorbed by the pyroelectric device 2 that is closely attached to them. Since the pyroelectric composite material layer 21 has a spontaneous polarization effect, as time changes, once the SiC JFET device 1 in the cascode switching device experiences thermal runaway or the switch short-circuits, the temperature absorbed by the pyroelectric device 2 will suddenly no longer change slowly over time, but will change rapidly over time. In the same period of time, the pyroelectric composite material layer 21 in the pyroelectric device 2 will absorb more heat generated by the cascode switching device, causing dT / dt to increase significantly. At this time, the oscillation degree of the electric dipole of the pyroelectric composite material layer 21 will be further enhanced, and the spontaneous polarization of the pyroelectric composite material layer 21 will be weakened, thereby driving electrons to flow in the loop formed by the first graphene electrode 22, the SiC JFET device gate 12, the SiC JFET device source 13 and the first aluminum electrode 24, and the second graphene electrode 23, the GaN HEMT device gate 32, the GaN The current flows in the loop formed by the HEMT device source 33 and the second aluminum electrode 25, reaching a new electrostatic equilibrium state. The current directions in the two loops are as follows: Figure 3 The direction of the current i is shown.

[0043] like Figure 4 As shown, according to the relationship between pyroelectric current intensity and temperature change rate i p =dQ / dt=pS(dT / dt), the current range can be determined. Then, according to V=(p / εr)hdT, the open circuit voltage range of the pyroelectric device 2 with temperature change can be obtained as 0-24V. When dT / dt=0.5℃ / s of the pyroelectric device 2 is greater than zero, the pyroelectric composite material layer 21 has a pyroelectric effect. The principle of the pyroelectric effect is as follows Figure 5 As shown, the pyroelectric device 2 will generate an open circuit voltage of 2V. When the dT / dt of the pyroelectric device 2 is 1.0°C / s, the pyroelectric device 2 will generate an open circuit voltage of 20V. In the above formula, p is the pyroelectric coefficient and its value is -31μC / (m 2K), Q is the pyroelectric charge, S is the electrode surface area, and εr is the relative dielectric constant of PVDF, which is 7.

[0044] like Figure 3 As shown, the second graphene electrode 23 on the right side of the silicon dioxide insulating layer 26 on the pyroelectric composite material layer 21 is connected to the gate 32 of the GaN HEMT device, and the second aluminum electrode 25 on the right side of the silicon dioxide insulating layer 26 is connected to the source 33 of the GaN HEMT device. Once the SiC JFET device 1 in the cascode switching device in the circuit experiences thermal runaway or short circuit, the switching device generates a large amount of heat, causing the dT / dt of the pyroelectric device to reach 0.5°C / s>0, and the pyroelectric device 2 generates an open-circuit voltage of 2V. At this time, the open-circuit voltage of the pyroelectric device 2 and the gate-source voltage of the GaN HEMT device 3 are equivalent to forming two voltage sources with opposite polarities between the gate 32 of the GaN HEMT device and the source 33 of the GaN HEMT device, and the gate-source voltage of the SiC JFET device 1 is equivalent to forming two voltage sources with opposite polarities between the gate 12 of the SiC JFET device and the source 13 of the SiC JFET device. If it is assumed that Figure 1 The external gate voltage control circuit 4 provides a driving voltage with an amplitude of 3V. According to Kirchhoff's voltage law KVL, at this time, V G,GaN -V S,GaN =V GS,GaN =3V-2V=1V <V th,GaN =2V, the GaN HEMT device 3 is immediately turned off and in the off state. Since the open-circuit voltage is small at this time, the gate-source voltage of the SiC JFET device 1 is not less than its threshold voltage. The SiC JFET device 1 is not turned off and is in the on state, but the overall cascode switch device is turned off. At this time, in order to turn on the GaN HEMT device 3, the external gate voltage control circuit 4 provides a pulse signal with an amplitude of at least 4V, such as Figure 6 FIG. 4 shows an equivalent circuit diagram of a cascode switching device when the GaN HEMT device 3 is turned off.

[0045] like Figure 7As shown, the first graphene electrode 22 of the pyroelectric composite material layer 21 on the left side of the silicon dioxide insulating layer 26 is connected to the SiC JFET device gate 12, the first aluminum electrode 24 on the left side of the silicon dioxide insulating layer 26 is connected to the SiC JFET device source 13, the SiC JFET device gate 12 is connected to the GaN HEMT device source 33, and the SiC JFET device source 13 is connected to the GaN HEMT device drain 31. When the SiC JFET device 1 in the cascode switch device in the circuit experiences thermal runaway or the switch is short-circuited, a large amount of heat is generated, causing the pyroelectric device 2 to generate an open circuit voltage of 20V when dT / dt = 1.0℃ / s>0; if it is assumed that Figure 1 The external gate voltage control circuit 4 provides a driving voltage with an amplitude of 3V. According to Kirchhoff's voltage law KVL, V G,GaN -V S,GaN =V GS,GaN =3V-20V=-17V <V th,GaN =2V, GaN HEMT device 3 is immediately turned off and is in the disconnected state. Since the open circuit voltage is large at this time, V G,SiC -V S,SiC =V GS,SiC -20V <V th,SiC , the SiC JFET device 1 is also turned off and is in the off state. Figure 8 FIG. 1 shows an equivalent circuit diagram of a cascode switching device when both the GaN HEMT device 3 and the SiC JFET device 1 are turned off.

[0046] In summary, when the cascode switch device operates in a high-frequency, high-voltage, and high-current environment, it utilizes the heat generated by its own operation and the pyroelectric effect of the pyroelectric device to avoid thermal runaway of the SiC JFET device in the cascode switch device or breakdown of the GaN HEMT device when a short circuit occurs in the GaN / SiC cascode switch device, thereby protecting the SiC JFET device and GaN HEMT device in the cascode switch device in the circuit.

[0047] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high-temperature protected GaN / SiC cascode switching device, characterized in that: The invention comprises a high-voltage, low-frequency depletion-type SiC JFET device (1), a low-voltage, high-frequency enhancement-type GaN HEMT device (3), and a pyroelectric device (2) connected to the SiC JFET device (1) and the GaN HEMT device (3) and integrated and packaged on the same substrate; wherein the pyroelectric device (2) comprises a spontaneously polarized pyroelectric composite material layer (21); the pyroelectric device (2) further comprises a first graphene electrode (22), a second graphene electrode (23) arranged on the upper side of the pyroelectric composite material layer (21) and a first aluminum electrode (24), a second aluminum electrode (25) arranged on the lower side; the first graphene electrode (22) and the second graphene electrode (23) and the first aluminum electrode (24) and the second aluminum electrode (25) are electrically isolated by a silicon dioxide insulating layer (26); The SiC JFET device (1) comprises a SiC JFET device drain (11), a SiC JFET device gate (12), and a SiC JFET device source (13) arranged on a first surface; the GaN HEMT device (3) comprises a GaN HEMT device drain (31), a GaN HEMT device gate (32), and a GaN HEMT device source (33) arranged on the first surface; the SiC JFET device drain (11) is connected to an external circuit of a GaN / SiC cascode switch device, the SiC JFET device gate (12) is electrically connected to the GaN HEMT device source (33), and the SiC JFET device source (13) is electrically connected to the GaN HEMT device drain (31); the SiC JFET device gate (12) is electrically connected to a first graphene electrode (22), and the SiC JFET device source (13) is electrically connected to a first aluminum electrode (24); the GaN The gate electrode (32) of the HEMT device is electrically connected to the second graphene electrode (23) and to an external gate voltage control circuit (4); the source electrode (33) of the GaN HEMT device is electrically connected to the second aluminum electrode (25) and to an external circuit of a GaN / SiC cascode switch device.

2. The high temperature protection GaN / SiC cascode switch device according to claim 1, characterized in that: The pyroelectric composite material layer (21) is a polyvinylidene fluoride-trifluoroethylene copolymer composite material layer.

3. The high temperature protection GaN / SiC cascode switch device according to claim 2, characterized in that: The polyvinylidene fluoride-trifluoroethylene copolymer composite material is a [P(VDF / TrFE) (80 / 20)] polymer composite material with a Curie temperature of 135°C.

4. The high temperature protection GaN / SiC cascode switch device according to claim 1, characterized in that: A closed sub-circuit is formed among the second graphene electrode (23), the second aluminum electrode (25), the gate (32) of the GaN HEMT device, and the source (33) of the GaN HEMT device; when the temperature change rate dT / dt of the pyroelectric device (2) is greater than zero, i.e., dT / dt = 0.5 °C / s, two voltage sources with opposite polarities are formed between the pyroelectric open-circuit voltage and the gate (32) and the source (33) of the GaN HEMT device. After superposition, the gate-source voltage VGS,GaN of the GaN HEMT device (3) is less than Vth,GaN, and the GaN HEMT device (3) is in the off state, and the SiC JFET device (1) is in the on state.

5. The high temperature protection GaN / SiC cascode switch device according to claim 1, characterized in that: A closed sub-circuit is formed among the first graphene electrode (22), the first aluminum electrode (24), the gate (12) of the SiC JFET device, and the source (13) of the SiC JFET device; when the temperature change rate dT / dt of the pyroelectric device (2) is greater than zero, i.e., dT / dt = 0.8 °C / s, two voltage sources with opposite polarities are formed between the pyroelectric open-circuit voltage and the gate (12) and the source (13) of the SiC JFET device. After superposition, the gate-source voltage VGS,SiC of the SiC JFET device (1) is less than Vth,SiC, and the SiC JFET device (1) is in the off state, and the GaN HEMT device (3) is in the off state.

6. A circuit, characterized in that: The circuit includes the GaN / SiC cascode switching device as described in any one of claims 1-5.

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