A high threshold stability GaN power device and its preparation method

Abstract

The present invention belongs to the technical field of GaN power devices, and specifically relates to a high-threshold stability GaN power device and a preparation method thereof. The high-threshold stability GaN power device provided by the present invention comprises a hole blocking layer arranged on the upper surface of the GaN buffer layer portion; the initial end of the source field plate is located on the upper surface of the source, and the projection position of the edge of the end of the source field plate on the upper surface of the buffer layer is located within the projection area of ​​the hole blocking layer on the upper surface of the GaN buffer layer; the material of the hole blocking layer is N-type GaN. The GaN power device provided by the present invention adds a hole blocking layer of N-type GaN material at a specific area position on the upper surface of the GaN buffer layer, which can effectively play the role of hole blocking and prevent the holes generated by impact ionization from moving toward the gate, thereby achieving high threshold stability and having good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of GaN power devices, and in particular relates to a high-threshold stability GaN power device and a preparation method thereof. Background Art

[0002] Power electronic devices have always been the core and foundation of power electronic technology, playing a vital role in the management and distribution of electricity. The first-generation semiconductor material Si has always played an irreplaceable role in the development of power electronic technology. However, in recent years, as people's requirements for power electronic devices have become higher and higher, Si materials have approached their performance limits. Therefore, the speed of performance improvement of Si-based devices can no longer meet the requirements of modern electronic technology for greater power capacity, higher frequency, and lower loss. The third-generation semiconductor material GaN has the advantages of large bandgap, strong breakdown field, and high electron saturation velocity. The heterostructure based on GaN (AlGaN / GaN) has a high two-dimensional electron gas concentration and high electron mobility. It is the preferred material for preparing a new generation of high-performance power electronic devices and has broad application prospects.

[0003] Due to the polarization effect, the AlGaN / GaN heterostructure will produce a high concentration of two-dimensional electron gas at the AlGaN / GaN interface. Therefore, GaN power devices naturally work in depletion mode, that is, normally-on devices. GaN power devices are high-voltage devices, usually used in high-frequency high-voltage switching scenarios. When the device is working, it will repeatedly go through the process of opening and closing. In the shutdown process, the drain is high voltage and the gate is negative voltage; while in the turn-on process, the voltage on the drain is very small and the voltage on the gate is close to 0V. In the shutdown process, due to the high voltage of the drain, a strong electric field is generated in the GaN buffer layer, and the electrons are accelerated to collide with atoms, resulting in collision ionization. The collision ionization process will produce electron-hole pairs, in which the electrons will drift to the drain and be absorbed; the holes will be attracted to the gate by the negative pressure of the gate, causing hole accumulation under the gate. As a result, when in the on state, the threshold voltage of the GaN device drifts in the negative direction. The negative drift of the threshold voltage of the GaN device will cause the reliability of the device to decrease, and in severe cases, it will cause the device to fail. Summary of the invention

[0004] The purpose of the present invention is to provide a high threshold stability GaN power device and a preparation method thereof. The GaN power device provided by the present invention can achieve high threshold stability and has good application prospects.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a high-threshold stability GaN power device, comprising a substrate layer; a GaN buffer layer arranged on the upper surface of the substrate layer; a hole blocking layer arranged on a portion of the upper surface of the GaN buffer layer; a GaN channel layer arranged on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer; an AlGaN barrier layer arranged on the upper surface of the GaN channel layer; a gate arranged on a portion of the upper surface of the AlGaN barrier layer; a source electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a drain electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a source field plate fixedly connected to the upper surface of the source electrode, wherein the initial end of the source field plate is located on the upper surface of the source electrode, and the projection position of the edge of the terminal end of the source field plate on the upper surface of the buffer layer is located within the region of the projection area of ​​the hole blocking layer on the upper surface of the GaN buffer layer; the material of the hole blocking layer is N-type GaN.

[0007] Preferably, an edge of the end of the source field plate is aligned with a vertical symmetry axis of the hole blocking layer.

[0008] Preferably, the doping element of the N-type GaN is Si, and the doping amount of Si is 2×10 17 ~8×10 17 / cm 3 .

[0009] Preferably, the doping amount of the Si element is 5×10 17 / cm 3 .

[0010] Preferably, the hole blocking layer has a thickness of 10-30 nm.

[0011] Preferably, the hole blocking layer has a thickness of 15 nm.

[0012] Preferably, the thickness of the GaN channel layer is 500 nm.

[0013] Preferably, the thickness of the AlGaN barrier layer is 20 nm.

[0014] The present invention provides a method for preparing a high threshold stability GaN power device as described in the above technical solution, comprising the following steps:

[0015] Preparing a GaN buffer layer on the upper surface of the substrate layer;

[0016] Preparing a hole blocking layer on the upper surface of the GaN buffer layer;

[0017] Preparing a GaN channel layer on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer;

[0018] Preparing an AlGaN barrier layer on the upper surface of the GaN channel layer to obtain a semi-finished product;

[0019] A gate, a source, a drain and a source field plate are prepared on the semi-finished product to obtain the high threshold stability GaN power device.

[0020] Preferably, the method for preparing the hole blocking layer comprises the following steps:

[0021] SiO is prepared on the upper surface of the GaN buffer layer. 2 Thin film; in the SiO 2 The upper surface of the film is coated with photoresist except for the preparation area of ​​the hole blocking layer, and then etched to obtain SiO 2 layer, the SiO 2 A layer is formed in the preparation area of ​​the hole blocking layer to expose a portion of the upper surface of the GaN buffer layer;

[0022] In the SiO 2 The N-type GaN film is prepared on the upper surface of the layer and the upper surface of the exposed GaN buffer layer, and then the SiO 2 layer and located in SiO 2 An N-type GaN film is formed on the upper surface of the layer to obtain the hole blocking layer.

[0023] The present invention provides a high-threshold stability GaN power device, comprising a substrate layer; a GaN buffer layer arranged on the upper surface of the substrate layer; a hole blocking layer arranged on a portion of the upper surface of the GaN buffer layer; a GaN channel layer arranged on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer; an AlGaN barrier layer arranged on the upper surface of the GaN channel layer; a gate arranged on a portion of the upper surface of the AlGaN barrier layer; a source electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a drain electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a source field plate fixedly connected to the upper surface of the source electrode, wherein the initial end of the source field plate is located on the upper surface of the source electrode, and the projection position of the edge of the terminal end of the source field plate on the upper surface of the buffer layer is located within the region of the projection area of ​​the hole blocking layer on the upper surface of the GaN buffer layer; the material of the hole blocking layer is N-type GaN. In the GaN power device provided by the present invention, when the device is turned off, the drain is subjected to high voltage and the gate is subjected to negative voltage, which causes the two-dimensional electron gas below the gate to be disconnected in the gate region (e.g. Figure 1As shown in the figure, no current can be formed. Due to the presence of high voltage at the drain, a strong electric field is formed in the GaN buffer layer. The strong electric field in the GaN buffer layer is mainly concentrated at the position corresponding to the end of the source field plate (i.e., the projection position of the edge of the end of the source field plate on the upper surface of the GaN buffer layer) and the edge of the drain. This strong electric field will cause collision ionization in the GaN buffer layer, and collision ionization will produce electron-hole pairs, such as Figure 1 As shown, the electrons therein will drift to the drain and be absorbed. The holes therein will be attracted by the negative pressure of the gate, drift toward the gate, and accumulate in the AlGaN barrier layer below the gate and at the interface between the AlGaN barrier layer and the gate. Due to the accumulation of holes, the threshold voltage of the device will shift negatively in the next on state. In the structure of the GaN power device provided by the present invention, due to the presence of the hole blocking layer (i.e., the N-GaN hole blocking layer) of the N-type GaN material in a specific position area, the holes will be blocked by the N-GaN hole blocking layer in the process of drifting toward the gate, that is, they will be recombined by the electrons in the N-GaN hole blocking layer, so that the GaN power device provided by the present invention will not cause hole accumulation under the gate, and the threshold stability of the device is greatly improved. In summary, the GaN power device provided by the present invention adopts an AlGaN / GaN heterostructure. During the epitaxial growth process, a hole blocking layer of N-type GaN material is added to a specific area on the upper surface of the GaN buffer layer, which can effectively play a hole blocking role and prevent the holes generated by impact ionization from moving toward the gate, thereby achieving high threshold stability and having good application prospects.

[0024] Furthermore, in the present invention, the thickness of the hole blocking layer is 10-30 nm. If the thickness of the hole blocking layer is too small, the crystal growth quality of N-type GaN in the hole blocking layer will be poor, the electron concentration will be low, and the hole blocking effect will not be achieved. If the thickness of the hole blocking layer is too large, it will affect the growth quality of the subsequent GaN channel layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a high threshold stability GaN power device provided by the present invention in a device-off state;

[0026] Figure 2 A schematic diagram of a structure in which a GaN buffer layer is prepared on the upper surface of a substrate layer in an embodiment of the present invention;

[0027] Figure 3 In the embodiment of the present invention, SiO is prepared on the upper surface of the GaN buffer layer. 2 Schematic diagram of the layer structure;

[0028] Figure 4 In the embodiment of the present invention, SiO 2Schematic diagram of the structure of preparing N-type GaN film on the upper surface of the layer;

[0029] Figure 5 It is a schematic diagram of the structure of preparing a hole blocking layer on the upper surface of a GaN buffer layer in the implementation of the present invention;

[0030] Figure 6 It is a schematic diagram of the structure of preparing the initial thin films of the GaN channel layer and the AlGaN barrier layer in an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the structure of preparing a gate in an embodiment of the present invention;

[0032] Figure 8 This is a schematic diagram of the structure of preparing an initial thin film of a passivation layer in an embodiment of the present invention;

[0033] Fig. 9 A schematic diagram of the structure of a high threshold stability GaN power device provided by the present invention;

[0034] In the figure: 1 is the substrate layer, 2 is the GaN buffer layer, 3 is the GaN channel layer, 4 is the hole blocking layer, 5 is the AlGaN barrier layer, 5-1 is the initial film of the AlGaN barrier layer, 6 is the source, 7 is the drain, 8 is the gate, 9 is the source field plate, 10 is the SiO 2 layer, 11 is an N-type GaN thin film, 12 is a two-dimensional electron gas, 13 is an electron-hole pair, 14 is a passivation layer, and 14-1 is an initial thin film of the passivation layer. DETAILED DESCRIPTION

[0035] The present invention provides a high-threshold stability GaN power device, comprising a substrate layer; a GaN buffer layer arranged on the upper surface of the substrate layer; a hole blocking layer arranged on a portion of the upper surface of the GaN buffer layer; a GaN channel layer arranged on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer; an AlGaN barrier layer arranged on the upper surface of the GaN channel layer; a gate arranged on a portion of the upper surface of the AlGaN barrier layer; a source electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a drain electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a source field plate fixedly connected to the upper surface of the source electrode, wherein the initial end of the source field plate is located on the upper surface of the source electrode, and the projection position of the edge of the terminal end of the source field plate on the upper surface of the buffer layer is located within the region of the projection area of ​​the hole blocking layer on the upper surface of the GaN buffer layer; the material of the hole blocking layer is N-type GaN.

[0036] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0037] The structural schematic diagram of the high threshold stability GaN power device provided by the present invention is as follows Fig. 9 As shown, the schematic diagram of the high threshold stability GaN power device provided by the present invention in the device off state is as follows Figure 1 As shown below. Fig. 9 The structure of the high threshold stability GaN power device provided by the present invention is described in detail.

[0038] The high threshold stability GaN power device provided by the present invention comprises a substrate layer 1. In the present invention, the material of the substrate layer 1 preferably comprises one or more of Si, sapphire and SiC. The present invention has no special requirements for the thickness of the substrate layer 1, and it can be set according to the conventional setting in the art.

[0039] The high threshold stability GaN power device provided by the present invention comprises a GaN buffer layer 2 arranged on the upper surface of the substrate layer. The present invention has no special requirements on the thickness of the GaN buffer layer 2, and the thickness can be set according to the conventional setting in the art.

[0040] The high threshold stability GaN power device provided by the present invention comprises a hole blocking layer 4 disposed on the upper surface of the GaN buffer layer. The material of the hole blocking layer 4 is N-type GaN. In the present invention, the doping element of the N-type GaN is preferably Si, and the doping amount of Si is preferably 2×10 17 ~8×10 17 / cm 3 More preferably, 5×10 17 / cm 3 The thickness of the hole blocking layer is preferably 10-30 nm, more preferably 15 nm.

[0041] The high threshold stability GaN power device provided by the present invention comprises a GaN channel layer 3 arranged on the remaining upper surface of the GaN buffer layer 2 and the upper surface of the hole blocking layer 4. In the present invention, the thickness of the GaN channel layer 3 is preferably 500 nm.

[0042] In the present invention, a GaN buffer layer is first grown on the upper surface of the substrate layer. Because the lattice constants of the substrate layer material and the GaN material do not match, a GaN buffer layer is grown. After the GaN buffer layer is grown, a GaN channel layer is then grown. In the upper part of the GaN channel layer, two-dimensional electron gas will exist to form current, so it is called a channel layer.

[0043] The high threshold stability GaN power device provided by the present invention comprises an AlGaN barrier layer 5 arranged on the upper surface of the GaN channel layer. In the present invention, the thickness of the AlGaN barrier layer 5 is 20 nm.

[0044] The high threshold stability GaN power device provided by the present invention comprises a gate 8 arranged on a portion of the upper surface of the AlGaN barrier layer 5 .

[0045] In the present invention, the projection area of ​​the gate 8 on the upper surface of the GaN buffer layer 2 does not overlap with the projection area of ​​the hole blocking layer 4 on the upper surface of the GaN buffer layer 2 .

[0046] The high threshold stability GaN power device provided by the present invention comprises a source electrode 6 in ohmic contact with the GaN channel layer 3 and the AlGaN barrier layer 5 .

[0047] In the present invention, the gate 8 is close to the source 6 and far away from the drain 7. That is, the distance between the gate 8 and the source 6 is smaller than the distance between the gate 8 and the drain 7.

[0048] The high threshold stability GaN power device provided by the present invention comprises a drain 7 in ohmic contact with the GaN channel layer 3 and the AlGaN barrier layer 5 .

[0049] The high threshold stability GaN power device provided by the present invention comprises a source field plate 9 fixedly connected to the upper surface of the source electrode 6, the initial end of the source field plate 9 is located on the upper surface of the source electrode 6, and preferably, the edge of the initial end of the source field plate 9 is aligned with the outer edge of the source electrode 6. The projection position of the edge of the terminal end of the source field plate 9 on the upper surface of the GaN buffer layer 2 is located within the region of the projection area of ​​the hole blocking layer 4 on the upper surface of the GaN buffer layer 2.

[0050] In the present invention, the edge of the end of the source field plate 9 is aligned with the vertical symmetry axis of the hole blocking layer 4, that is, the projection position of the edge of the end of the source field plate 9 on the upper surface of the GaN buffer layer 2 preferably coincides with the center point position of the projection area of ​​the hole blocking layer 4 on the upper surface of the GaN buffer layer 2. In the present invention, the projection shape of the edge of the end of the source field plate 9 on the upper surface of the GaN buffer layer 2 is a straight line, and the projection position of the edge of the end of the source field plate 9 on the upper surface of the GaN buffer layer 2 preferably coincides with the center point position of the projection area of ​​the hole blocking layer 4 on the upper surface of the GaN buffer layer 2, that is, the center point position of the projection area of ​​the hole blocking layer 4 on the upper surface of the GaN buffer layer 2 is located on the straight line of the projection of the edge of the end of the source field plate 9 on the upper surface of the GaN buffer layer 2.

[0051] In the present invention, the effect of aligning the edge of the end of the source field plate 9 with the vertical symmetry axis of the hole blocking layer 4 is: since the position in the GaN buffer layer 2 corresponding to the edge of the end of the source field plate 9 (i.e., the position of the projection of the edge of the end of the source field plate 9 on the upper surface of the GaN buffer layer 2) is the area with the strongest electric field in the GaN buffer layer 2, that is, the place where collision ionization is most intense, therefore, when the edge of the end of the source field plate 9 is aligned with the vertical symmetry axis of the hole blocking layer 4, the hole blocking layer 4 can most effectively block holes from drifting toward the gate 6.

[0052] The high threshold stability GaN power device provided by the present invention preferably further includes a passivation layer 14 disposed on the remaining upper surface of the AlGaN barrier layer 5 except the gate, and disposed on the upper surface of the gate 8. In the present invention, the upper surface of the passivation layer 14 contacts the lower surface of the source field plate 9, that is, the source field plate 9 is located on the upper surface of the source 6 and part of the passivation layer 14 at the same time.

[0053] The present invention provides a method for preparing a high threshold stability GaN power device as described in the above technical solution, comprising the following steps:

[0054] Preparing a GaN buffer layer on the upper surface of the substrate layer;

[0055] Preparing a hole blocking layer on the upper surface of the GaN buffer layer;

[0056] Preparing a GaN channel layer on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer;

[0057] Preparing an AlGaN barrier layer on the upper surface of the GaN channel layer to obtain a semi-finished product;

[0058] A gate, a source, a drain and a source field plate are prepared on the semi-finished product to obtain the high threshold stability GaN power device.

[0059] The present invention prepares a GaN buffer layer on the upper surface of the substrate layer. The present invention has no special requirements on the preparation method of the GaN buffer layer, and it can be prepared in an MOCVD device according to conventional operations in the art.

[0060] After obtaining the GaN buffer layer, the present invention prepares a hole blocking layer on the upper surface of the GaN buffer layer. In the present invention, the method for preparing the hole blocking layer preferably includes the following steps:

[0061] SiO is prepared on the upper surface of the GaN buffer layer. 2 Thin film; in the SiO 2 The upper surface of the film is coated with photoresist except for the preparation area of ​​the hole blocking layer, and then etched to obtain SiO 2layer, the SiO 2 A layer is formed in the preparation area of ​​the hole blocking layer to expose a portion of the upper surface of the GaN buffer layer;

[0062] In the SiO 2 The N-type GaN film is prepared on the upper surface of the layer and the upper surface of the exposed GaN buffer layer, and then the SiO 2 layer and located in SiO 2 An N-type GaN film is formed on the upper surface of the layer to obtain the hole blocking layer.

[0063] The present invention prepares SiO on the upper surface of the GaN buffer layer. 2 Thin film; in the SiO 2 The upper surface of the film is coated with photoresist except for the preparation area of ​​the hole blocking layer, and then etched to obtain SiO 2 layer, the SiO 2 The layer exposes part of the upper surface of the GaN buffer layer in the preparation area of ​​the hole blocking layer. 2 The thin film is preferably prepared in a PECVD device. 2 The thickness of the film is preferably 100 nm. After the etching is completed, the present invention preferably further comprises degumming the etched semi-finished product to obtain the SiO 2 layer.

[0064] Obtain the SiO 2 After the SiO 2 The N-type GaN film is prepared on the upper surface of the layer and the upper surface of the exposed GaN buffer layer, and then the SiO 2 layer and located in SiO 2 The hole blocking layer is obtained by forming an N-type GaN film on the upper surface of the layer. In the present invention, before preparing the N-type GaN film, the present invention preferably treats the SiO 2 The semi-finished product of the layer is cleaned. The N-type GaN film is preferably prepared in an MOCVD device, and the method for preparing the N-type GaN film is preferably to dope Si elements during the growth of GaN to form an N-GaN film (an N-type semiconductor). The acid etching method is preferably performed using an inorganic strong acid, and the inorganic strong acid is preferably hydrofluoric acid.

[0065] After the hole blocking layer is obtained, the present invention prepares a GaN channel layer on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer. The GaN channel layer is preferably prepared in an MOCVD device.

[0066] After obtaining the GaN channel layer, the present invention prepares an AlGaN barrier layer on the upper surface of the GaN channel layer to obtain a semi-finished product. The AlGaN barrier layer is preferably prepared in an MOCVD device.

[0067] After obtaining the semi-finished product, the present invention prepares the gate, source, drain and source field plate on the semi-finished product to obtain the high threshold stability GaN power device. In the present invention, the material of the source, drain, gate and source field plate preferably includes metal. The thickness of the source, drain, gate and source field plate is preferably 1-7 μm, and can be 4 μm in the embodiment. The present invention has no special requirements for the preparation method of the source, drain, gate and source field plate.

[0068] In the present invention, the high threshold stability GaN power device preferably also includes: a passivation layer 14 is arranged on the remaining upper surface of the AlGaN barrier layer 5 except the gate, and is also arranged on the upper surface of the gate 8. The preparation method after obtaining the semi-finished product is replaced by: the present invention prepares the gate, passivation layer, source, drain and source field plate on the semi-finished product to obtain the high threshold stability GaN power device.

[0069] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0070] Example 1

[0071] (1) Place the substrate layer 1 in a MOCVD device. In this embodiment, the material of the substrate layer 1 is Si, sapphire or SiC. Epitaxially grow a GaN buffer layer 2, such as Figure 2 shown.

[0072] (2) Use PECVD equipment to grow a layer of SiO on the surface of the GaN buffer layer 2 The film thickness is 100nm. Then on SiO 2 The upper surface of the film except the area where the hole blocking layer is prepared is coated with a photoresist, and then etched to remove the SiO 2 The film will be etched away because it has no photoresist protection, and the SiO 2 The film will not be etched away because of the photoresist, and then the resist is removed to obtain SiO 2 Layer, such as Figure 3 shown.

[0073] (3) After cleaning the wafer in step (2), place it back into the MOCVD device to epitaxially grow a layer of N-GaN film (such as Figure 4As shown in Figure 2). N-GaN film is formed by doping Si in the process of growing GaN to form an N-type semiconductor. The thickness of the N-GaN film is 10~30nm, and the thickness in this embodiment is 15nm. The doping amount of Si is 2×10 17 ~8×10 17 / cm 3 In this embodiment, the doping amount of Si is 5×10 17 / cm 3 .

[0074] (4) After the N-GaN film is grown, the wafer obtained in step (3) is placed in an HF acid solution to 2 The N-GaN layer is removed, and the N-GaN film above it will be removed, leaving only the N-GaN film in a specific area, that is, the N-GaN hole blocking layer is obtained. Figure 5 shown.

[0075] (5) The wafer is placed in MOCVD to grow GaN channel layer and AlGaN barrier layer thin film in sequence. The thickness of GaN channel layer is 500nm, and the thickness of AlGaN barrier layer thin film is 20nm. The structure after growth is as follows: Figure 6 As shown, Figure 6 The dotted line in the figure is the two-dimensional electron gas 12, which is caused by the piezoelectric polarization of the AlGaN barrier layer and the GaN channel layer, as well as the spontaneous polarization of the GaN channel layer itself. Electrons have only two degrees of freedom in the two-dimensional electron gas 12, so the mobility is very high. The conductivity of GaN power devices is achieved by the two-dimensional electron gas 12, that is, the two-dimensional electron gas 12 provides the working current of the device.

[0076] (6) Then, the subsequent wafer fabrication process is carried out, that is, the gate is prepared on the upper surface of the initial film of the AlGaN barrier layer, such as Figure 7 As shown. The initial film of the passivation layer is prepared on the upper surface of the gate and the remaining upper surface of the initial film of the AlGaN barrier layer, as shown Figure 8 Then, the source and drain patterns are obtained by etching the initial thin film of the passivation layer and the initial thin film of the AlGaN barrier layer by photolithography, and finally, a part of the initial thin film of the passivation layer and the initial thin film of the AlGaN barrier layer are removed by etching to obtain the passivation layer and the AlGaN barrier layer, and finally, the source, drain and source field plate are prepared to obtain a high threshold stability GaN power device, as shown in FIG. Fig. 9 In this embodiment, the edge of the initial end of the source field plate is aligned with the outer edge of the source, the position of the terminal edge of the source field plate is vertically aligned with the center point of the N-GaN hole blocking layer, and the source field plate is located on the upper surface of the source and part of the passivation layer.

[0077] It can be seen from the above embodiments that in the structure of the GaN power device provided by the present invention, due to the presence of the hole blocking layer (i.e., N-GaN hole blocking layer) of N-type GaN material in a specific position area, holes will be blocked by the N-GaN hole blocking layer in the process of drifting toward the gate, that is, they will be recombined by the electrons in the N-GaN hole blocking layer, so that the GaN power device provided by the present invention will not cause hole accumulation under the gate, and the threshold stability of the device is greatly improved. In summary, the GaN power device provided by the present invention adopts an AlGaN / GaN heterostructure, and during the epitaxial growth process, a layer of hole blocking layer of N-type GaN material is added to a specific area on the upper surface of the GaN buffer layer, which can effectively play a role in hole blocking, preventing holes generated by collision ionization from moving toward the gate, thereby achieving high threshold stability and having good application prospects.

[0078] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A high threshold stability GaN power device, characterized in that: It includes a substrate layer; a GaN buffer layer arranged on the upper surface of the substrate layer; a hole blocking layer arranged on a portion of the upper surface of the GaN buffer layer; a GaN channel layer arranged on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer; an AlGaN barrier layer arranged on the upper surface of the GaN channel layer; a gate arranged on a portion of the upper surface of the AlGaN barrier layer; and a source electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; a drain electrode in ohmic contact with the GaN channel layer and the AlGaN barrier layer; A source field plate fixedly connected to the upper surface of the source, the initial end of the source field plate is located on the upper surface of the source, and the projection position of the edge of the terminal end of the source field plate on the upper surface of the buffer layer is located within the area of ​​the projection area of ​​the hole blocking layer on the upper surface of the GaN buffer layer; the material of the hole blocking layer is N-type GaN.

2. The high threshold stability GaN power device according to claim 1, characterized in that: The edge of the end of the source field plate is aligned with the vertical symmetry axis of the hole blocking layer.

3. The high threshold stability GaN power device according to claim 1, characterized in that: The doping element of the N-type GaN is Si, and the doping amount of Si is 2×10 17 ~8×10 17 / cm 3 .

4. The high threshold stability GaN power device according to claim 3, characterized in that: The doping amount of Si element is 5×10 17 / cm 3 .

5. The high threshold stability GaN power device according to claim 1 or 3, characterized in that: The thickness of the hole blocking layer is 10-30 nm.

6. The high threshold stability GaN power device according to claim 5, characterized in that: The thickness of the hole blocking layer is 15 nm.

7. The high threshold stability GaN power device according to claim 1, characterized in that: The thickness of the GaN channel layer is 500 nm.

8. The high threshold stability GaN power device according to claim 1, characterized in that: The thickness of the AlGaN barrier layer is 20 nm.

9. The method for preparing a high threshold stability GaN power device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Preparing a GaN buffer layer on the upper surface of the substrate layer; Preparing a hole blocking layer on the upper surface of the GaN buffer layer; Preparing a GaN channel layer on the remaining upper surface of the GaN buffer layer and the upper surface of the hole blocking layer; Preparing an AlGaN barrier layer on the upper surface of the GaN channel layer to obtain a semi-finished product; A gate, a source, a drain and a source field plate are prepared on the semi-finished product to obtain the high threshold stability GaN power device.

10. The preparation method according to claim 9, characterized in that: The method for preparing the hole blocking layer comprises the following steps: A SiO2 film is prepared on the upper surface of the GaN buffer layer; a photoresist is coated on the upper surface of the SiO2 film except for the preparation area of ​​the hole blocking layer, and then the photoresist is etched to obtain a SiO2 layer on the upper surface of the GaN buffer layer, wherein the SiO2 layer exposes a portion of the upper surface of the GaN buffer layer in the preparation area of ​​the hole blocking layer; An N-type GaN film is prepared on the upper surface of the SiO2 layer and the upper surface of the exposed GaN buffer layer, and then the SiO2 layer and the N-type GaN film on the upper surface of the SiO2 layer are removed by acid etching to obtain the hole blocking layer.

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