Gallium nitride IMPATT diode and preparation method thereof

Abstract

According to the gallium nitride IMPATT diode and the preparation method thereof provided by the invention, the Schottky contact electrode is arranged on the upper surface of the avalanche region of the second region, and the ohmic contact electrode covers the outer surface, far away from the second region, of the first region, so that etching protection by using a metal layer as a hard mask is realized; an ohmic contact electrode and an anode Schottky contact electrode which are used for manufacturing the cathode are flush with the side wall of the active region, so that self-alignment of the device in the etching process is realized; besides, the first passivation layer and the field plate metal on the Schottky contact electrode form a field plate structure, and the self-alignment field plate structure can effectively improve the phenomenon of electric field concentration easily occurring in a semiconductor close to the edge of the anode metal, so that charges uniformly appear below the anode, the electric field distribution is more uniform, the reverse electric leakage is reduced, and the reliability of the device is improved. Therefore, the breakdown voltage of the gallium nitride IMPATT diode is improved, so that the gallium nitride IMPATT diode is closer to an ideal avalanche breakdown voltage value, and a better alternating-current oscillation characteristic is finally realized.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a gallium nitride IMPATT diode and a preparation method thereof. Background Art

[0002] The IMPATT diode is a device with negative differential resistance characteristics within a certain frequency range, and mainly works by using the mechanism of carrier injection and carrier transit time in the breakdown state. Therefore, it has the characteristics of high frequency and high power, and compared with other terahertz electronic devices, the IMPATT diode device also has the advantage of high efficiency as a terahertz frequency source.

[0003] Compared with GaAs-based and Si-based IMPATT, GaN material has a higher saturated electron drift velocity and breakdown electric field. When the IMPATT diode works in the breakdown state, for IMPATT diode devices of the same size and structure, the electron speed in the GaN-based IMPATT is faster, the electron transit time is shorter, and the GaN-based IMPATT can withstand higher voltages. Therefore, for IMAPTT diode devices, GaN-based IMPATT has better high-frequency performance and power performance than GaAs-based and Si-based IMPATT diode devices.

[0004] However, the process growth problem of P-type doping of GaN materials has not been effectively solved, and good P-type doping is the guarantee for the high-efficiency operation of IMPATT devices under high current density. Secondly, good gold-semiconductor contact near the contact between GaN material and metal electrode has high requirements on the surface of P-type doped gallium nitride material. Among the existing technologies, one of the most promising solutions to the problem of P-type doping of GaN materials is to use the reverse breakdown of Schottky electrodes and use Schottky barriers to realize the operation of gallium nitride IMPATT diodes. However, this solution will bring new problems, namely how to manufacture good Schottky barriers and epitaxial growth of N-type GaN materials with low defect density. In addition, due to problems such as heat dissipation and efficiency, the device structure design based on this method has also become a difficult problem.

[0005] Therefore, how to adopt a better structural design to enable the GaN-based IMPATT diode to achieve better AC oscillation characteristics has become a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a gallium nitride IMPATT diode and a preparation method thereof.

[0007] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a gallium nitride IMPATT diode, which has a bilaterally symmetrical structure and includes: a substrate layer, an AlN nucleation layer, a GaN buffer layer, and an n++-GaN ohmic contact layer arranged in sequence from bottom to top;

[0009] The n++-GaN ohmic contact layer is provided with a first region, a second region and a third region; the first region and the third region are symmetrically distributed along the vertical central axis of the second region; the upper surface of the n++-GaN ohmic contact layer is provided with a first groove and a second groove; the first groove is an L-shaped groove and is provided on one side of the upper surface of the n++-GaN ohmic contact layer; the first region is provided between the first groove and the second groove; the second groove is provided between the first region and the second region;

[0010] The first region and the second region both include: an n-GaN drift region, an n+-GaN avalanche termination region and an n-GaN avalanche region arranged in sequence from bottom to top; the second region is also provided with a Schottky contact electrode; the Schottky contact electrode is located on the upper surface of the n-GaN avalanche region of the second region; the n+-GaN avalanche termination region, the n-GaN avalanche region and the Schottky contact electrode of the second region have the same width and are smaller than the width of the n-GaN drift region of the second region;

[0011] The n-GaN drift region, n+-GaN avalanche termination region and n-GaN avalanche region in the first region have equal widths; the first groove and the outer surface of the first region away from the second region are covered with an ohmic contact electrode; the upward outer surface of the second region is covered with a first passivation layer; the first passivation layer is provided with a first notch along the vertical central axis of the second region; the upward outer surface of the first passivation layer is covered with a field plate metal; the field plate metal is in contact with the Schottky contact electrode along the first notch; the second groove, a partial area of ​​the outer surface of the ohmic contact electrode, the outer surface of the field plate metal, the outer surface of the second region, and the outer surface of the first region are all covered with a second passivation layer; the second passivation layer is provided with a second notch along the vertical central axis of the second region.

[0012] Optionally, the material of the n++-GaN ohmic contact layer is n++-GaN, with a thickness of 0.5 to 2.5 μm and a doping concentration of 5×10 18 ~1×10 20 cm -3 .

[0013] Optionally, the material of the n-GaN drift region is n-GaN, with a thickness of 0.5 to 2 μm and a doping concentration of 0.1 to 1×10 17 cm -3 .

[0014] Optionally, the material of the n+-GaN avalanche termination region is n+-GaN, with a thickness of 0.1 to 1 μm and a doping concentration of 0.1 to 5×10 18 cm -3 .

[0015] Optionally, the material of the n-GaN avalanche region is n-GaN, with a thickness of 0.1 to 1 μm and a doping concentration of 0.1 to 5×10 17 cm -3 .

[0016] Optionally, the material of the ohmic contact electrode is a Ti / Al / Ni / Au / Ni metal alloy with a thickness of 400-600 nm.

[0017] Optionally, the material of the Schottky contact electrode is Ni / Au / Ni metal alloy, and the thickness is 300-400 nm.

[0018] Optionally, the material of the first passivation layer and the second passivation layer is SiO2, the thickness of the first passivation layer is 300-500 nm, and the thickness of the second passivation layer is 500-800 nm.

[0019] In a second aspect, the present invention provides a method for preparing a gallium nitride IMPATT diode, which is used to prepare the gallium nitride IMPATT diode of the first aspect, comprising:

[0020] S1, selecting sapphire material as the initial material to form a substrate layer;

[0021] S2, epitaxially growing an AlN nucleation layer on the substrate layer by using a metal organic chemical vapor deposition (MOCVD) method;

[0022] S3, epitaxially growing a GaN buffer layer on the AlN nucleation layer by using a MOCVD method;

[0023] S4, epitaxially growing an n++-GaN ohmic contact layer on the GaN buffer layer by using a MOCVD method;

[0024] S5, epitaxially growing an n-GaN drift region on the n++-GaN ohmic contact layer by using a MOCVD method;

[0025] S6. epitaxially growing an n+-GaN avalanche termination region on the n-GaN drift region by using a MOCVD method;

[0026] S7, epitaxially growing an n-GaN avalanche region on the n+-GaN avalanche termination region by using a MOCVD method;

[0027] S8, etching the n++-GaN ohmic contact layer, the n-GaN drift region, the n+-GaN avalanche termination region and the n-GaN avalanche region using an etching technology, thereby forming a first annular mesa on the upper surface of the n++-GaN ohmic contact layer;

[0028] S9, forming an ohmic contact electrode on the first annular table surface;

[0029] S10, forming a Schottky contact electrode on the n-GaN avalanche region;

[0030] S11, etching the n-GaN drift region, the n+-GaN avalanche termination region and the n-GaN avalanche region using a self-aligned etching technique, thereby forming a second annular mesa on the upper surface of the n++-GaN ohmic contact layer;

[0031] S12, using radio frequency magnetron sputtering equipment to deposit SiO2 on the surface of the second annular table and to open holes to form a first passivation layer;

[0032] S13, forming a field plate metal on the first passivation layer and the Schottky contact electrode;

[0033] S14, etching the n++-GaN ohmic contact layer and the n-GaN drift region using a self-aligned etching technique to obtain a first device;

[0034] S15. Using radio frequency magnetron sputtering equipment, SiO2 is deposited on the upper surface of the first device and holes are opened to form a second passivation layer, thereby obtaining a gallium nitride IMPATT diode.

[0035] The present invention provides a gallium nitride IMPATT diode and a preparation method thereof. The gallium nitride IMPATT diode is a bilaterally symmetrical structure, including: a substrate layer, an AlN nucleation layer, a GaN buffer layer and an n++-GaN ohmic contact layer arranged in sequence from bottom to top; a first region, a second region and a third region are arranged on the n++-GaN ohmic contact layer; the first region and the third region are symmetrically distributed along the vertical central axis of the second region; a first groove and a second groove are arranged on the upper surface of the n++-GaN ohmic contact layer; the first groove is an L-shaped groove and is arranged on one side of the upper surface of the n++-GaN ohmic contact layer; the first region is arranged between the first groove and the second groove; the second groove is arranged between the first region and the second region; the first region and the second region both include: an n-GaN drift region, an n+-GaN avalanche termination region and an n-GaN avalanche region arranged in sequence from bottom to top; the second region is also provided with a Schottky contact electrode; the Schottky contact electrode is located in the second region the upper surface of the n-GaN avalanche zone of the second region; the widths of the n+-GaN avalanche termination zone, the n-GaN avalanche zone and the Schottky contact electrode of the second region are equal and smaller than the width of the n-GaN drift zone of the second region; the widths of the n-GaN drift zone, the n+-GaN avalanche termination zone and the n-GaN avalanche zone of the first region are equal; the first groove and the outer surface of the first region away from the second region are covered with an ohmic contact electrode; the upward outer surface of the second region is covered with a first passivation layer; the first passivation layer is provided with a first notch along the vertical central axis of the second region; the upward outer surface of the first passivation layer is covered with a field plate metal; the field plate metal is in contact with the Schottky contact electrode along the first notch; the second groove, a part of the outer surface area of ​​the ohmic contact electrode, the outer surface of the field plate metal, the outer surface of the second region and the outer surface of the first region are all covered with a second passivation layer; the second passivation layer is provided with a second notch along the vertical central axis of the second region. In the present invention, by setting a Schottky contact electrode on the upper surface of the n-GaN avalanche region in the second region, and covering the outer surface of the first region away from the second region with an ohmic contact electrode, a metal layer is used as a hard mask for etching protection, so that the ohmic contact electrode used to make the cathode and the anode Schottky contact electrode are flush with the side wall of the active region, and self-alignment in the device etching process is achieved. In addition, since the field plate metal on the first passivation layer and the Schottky contact electrode forms a field plate structure, the self-aligned field plate structure can effectively improve the electric field concentration phenomenon that is easy to occur in the semiconductor near the edge of the anode metal, so that the charge appears evenly under the anode, the electric field distribution is more uniform, and the reverse leakage is reduced; thereby, the breakdown voltage of the gallium nitride IMPATT diode is increased, making it closer to the ideal avalanche breakdown voltage value, and finally achieving better AC oscillation characteristics. In addition, through the self-aligned integrated structural design, the device preparation error caused by multiple overlays is avoided, and the controllability of the process is improved.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the cross-sectional structure of a gallium nitride IMPATT diode provided in an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of a process for preparing a gallium nitride IMPATT diode provided in an embodiment of the present invention;

[0039] Figure 3 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S7 is executed according to an embodiment of the present invention;

[0040] Figure 4 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S8 is executed according to an embodiment of the present invention;

[0041] Figure 5 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S9 is executed according to an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S10 is executed according to an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S11 is executed according to an embodiment of the present invention;

[0044] Figure 8 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S12 is executed according to an embodiment of the present invention;

[0045] Fig. 9 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S13 is executed according to an embodiment of the present invention;

[0046] Fig.10 A schematic diagram of the structure of a gallium nitride IMPATT diode device after S14 is executed according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0048] In order to improve the AC oscillation characteristics of a gallium nitride IMPATT diode, an embodiment of the present invention provides a gallium nitride IMPATT diode. Figure 1 A schematic diagram of the cross-sectional structure of a gallium nitride IMPATT diode provided in an embodiment of the present invention. Figure 1 As shown, the GaN IMPATT diode has a bilaterally symmetrical structure, including: a substrate layer 1, an AlN nucleation layer 2, a GaN buffer layer 3, and an n++-GaN ohmic contact layer 4 arranged in sequence from bottom to top;

[0049] The n++-GaN ohmic contact layer 4 is provided with a first region, a second region and a third region; the first region and the third region are symmetrically distributed along the vertical central axis of the second region; the upper surface of the n++-GaN ohmic contact layer 4 is provided with a first groove and a second groove; the first groove is an L-shaped groove and is provided on one side of the upper surface of the n++-GaN ohmic contact layer 4; the first region is provided between the first groove and the second groove; the second groove is provided between the first region and the second region;

[0050] The first region and the second region both include: an n-GaN drift region 5, an n+-GaN avalanche termination region 6 and an n-GaN avalanche region 7 arranged in sequence from bottom to top; the second region is also provided with a Schottky contact electrode 9; the Schottky contact electrode 9 is located on the upper surface of the n-GaN avalanche region 7 of the second region; the n+-GaN avalanche termination region 6, the n-GaN avalanche region 7 and the Schottky contact electrode 9 of the second region have the same width, and are smaller than the width of the n-GaN drift region 5 of the second region;

[0051] The n-GaN drift region 5, the n+-GaN avalanche termination region 6 and the n-GaN avalanche region 7 in the first region have equal widths; the first groove and the outer surface of the first region away from the second region are covered with an ohmic contact electrode 8; the upward outer surface of the second region is covered with a first passivation layer 10; the first passivation layer 10 is provided with a first notch along the vertical central axis of the second region; the upward outer surface of the first passivation layer 10 is covered with a field plate metal 11; the field plate metal 11 is in contact with the Schottky contact electrode 9 along the first notch; the second groove, a partial area of ​​the outer surface of the ohmic contact electrode 8, the outer surface of the field plate metal 11, the outer surface of the second region, and the outer surface of the first region are all covered with a second passivation layer 12; the second passivation layer 12 is provided with a second notch along the vertical central axis of the second region.

[0052] The embodiment of the present invention provides a gallium nitride IMPATT diode, which realizes etching protection by using a metal layer as a hard mask by setting a Schottky contact electrode on the upper surface of the n-GaN avalanche region in the second region and covering the outer surface of the first region away from the second region with an ohmic contact electrode, so that the ohmic contact electrode used to make the cathode and the anode Schottky contact electrode are flush with the side wall of the active region, and self-alignment is achieved during the device etching process. In addition, the field plate metal on the first passivation layer and the Schottky contact electrode forms a field plate structure, and the self-aligned field plate structure can effectively improve the electric field concentration phenomenon that is easy to occur in the semiconductor near the edge of the anode metal, so that the charge appears evenly under the anode, the electric field distribution is more uniform, and the reverse leakage is reduced; thereby, the breakdown voltage of the gallium nitride IMPATT diode is improved, making it closer to the ideal avalanche breakdown voltage value, and finally achieving better AC oscillation characteristics. In addition, through the self-aligned integrated structural design, the device preparation error caused by multiple overlays is avoided, and the controllability of the process is improved.

[0053] It should be noted that, in the embodiment of the present invention, the active region is specifically a region composed of the drift region 5 , the avalanche termination region 6 and the avalanche region 7 .

[0054] Optionally, the material of the n++-GaN ohmic contact layer 4 is n++-GaN, with a thickness of 0.5 to 2.5 μm and a doping concentration of 5×10 18 ~1×10 20 cm -3 .

[0055] Optionally, the material of the n-GaN drift region 5 is n-GaN, with a thickness of 0.5 to 2 μm and a doping concentration of 0.1 to 1×10 17 cm -3 .

[0056] Optionally, the material of the n+-GaN avalanche termination region 6 is n+-GaN, with a thickness of 0.1 to 1 μm and a doping concentration of 0.1 to 5×10 18 cm -3 .

[0057] Optionally, the material of the n-GaN avalanche region 7 is n-GaN, with a thickness of 0.1 to 1 μm and a doping concentration of 0.1 to 5×10 17 cm -3 .

[0058] Optionally, the material of the ohmic contact electrode 8 is a Ti / Al / Ni / Au / Ni metal alloy with a thickness of 400-600 nm.

[0059] Optionally, the material of the Schottky contact electrode 9 is Ni / Au / Ni metal alloy, and the thickness is 300-400 nm.

[0060] Optionally, the material of the first passivation layer 10 and the second passivation layer 12 is SiO 2 , the thickness of the first passivation layer 10 is 300-500 nm, and the thickness of the second passivation layer 12 is 500-800 nm.

[0061] Optionally, the material of the field plate metal 11 is Ni / Au double-layer metal with a thickness of 100-200 nm.

[0062] Based on the same inventive concept, an embodiment of the present invention further provides a method for preparing a gallium nitride IMPATT diode, which is used to prepare the gallium nitride IMPATT diode of the above embodiment. Figure 2 A schematic diagram of a process for preparing a gallium nitride IMPATT diode provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, including:

[0063] S1. Select sapphire material as the initial material to form a substrate layer 1.

[0064] It should be noted that, in the embodiment of the present invention, the thickness of the substrate layer 1 is 330-430 μm.

[0065] S2. epitaxially grow an AlN nucleation layer 2 on the substrate layer 1 by using a metal organic chemical vapor deposition (MOCVD) method.

[0066] Specifically, in the embodiment of the present invention, triethylgallium and high-purity nitrogen are used as gallium source and nitrogen source respectively, and a metal organic chemical vapor deposition MOCVD method is adopted to grow a 20-40 nm thick AlN nucleation layer 2 at a temperature of 950° C. and a pressure of 40 Torr.

[0067] S3 . epitaxially grow a GaN buffer layer 3 on the AlN nucleation layer 2 by using a MOCVD method.

[0068] Specifically, triethylgallium and high-purity nitrogen are used as gallium source and nitrogen source respectively, and a metal organic chemical vapor deposition MOCVD method is adopted to grow a 0.5-2 μm unintentionally doped GaN buffer layer 3 at a temperature of 950° C. and a pressure of 40 Torr.

[0069] S4. epitaxially grow an n++-GaN ohmic contact layer 4 on the GaN buffer layer 3 by using a MOCVD method.

[0070] Specifically, triethylgallium and high-purity nitrogen were used as gallium source and nitrogen source respectively, and silane was used as n-type doping source. Metal organic chemical vapor deposition (MOCVD) method was used to grow n++-GaN ohmic contact layer 4 with a thickness of 0.5 to 2.5 μm at a temperature of 1050°C and a pressure of 40 Torr. The doping concentration was 5×1018 ~1×10 20 cm -3 .

[0071] S5 . epitaxially grow an n-GaN drift region 5 on the n++-GaN ohmic contact layer 4 by using a MOCVD method.

[0072] Specifically, triethylgallium and high-purity nitrogen are used as gallium source and nitrogen source respectively, silane is used as n-type doping source, and metal organic chemical vapor deposition MOCVD method is used to grow 0.5-2 μm n-GaN drift region 5 at a temperature of 1050°C and a pressure of 40 Torr, with a doping concentration of 0.1-1×10 17 cm -3 .

[0073] S6. epitaxially grow an n+-GaN avalanche termination region 6 on the n-GaN drift region 5 by using a MOCVD method.

[0074] In this embodiment, triethylgallium and high-purity nitrogen are used as gallium source and nitrogen source respectively, silane is used as n-type doping source, and metal organic chemical vapor deposition MOCVD method is used to grow 0.1-1 μm n+-GaN avalanche termination region 6 at a temperature of 1050°C and a pressure of 40 Torr, with a doping concentration of 0.1-5×10 18 cm -3 .

[0075] S7. epitaxially grow an n-GaN avalanche region 7 on the n+-GaN avalanche termination region 6 by using a MOCVD method.

[0076] In this embodiment, triethylgallium and high-purity nitrogen are used as gallium source and nitrogen source respectively, silane is used as n-type doping source, and metal organic chemical vapor deposition MOCVD method is used to grow 0.1-1 μm n-GaN avalanche region 7 at a temperature of 1050°C and a pressure of 40 Torr, with a doping concentration of 0.1-5×10 17 cm -3 Correspondingly, Figure 3 A schematic diagram of the device structure after S7 is executed according to an embodiment of the present invention.

[0077] S8. Etch the n++-GaN ohmic contact layer 4, the n-GaN drift region 5, the n+-GaN avalanche termination region 6 and the n-GaN avalanche region 7 using an etching technique, thereby forming a first annular mesa on the upper surface of the n++-GaN ohmic contact layer 4.

[0078] Specifically, a large circular mask pattern with a radius of 65 to 85 μm is formed by photolithography on the n-GaN avalanche region 7, and then the reactive ion etching (RIE) method is used to etch the structure using a BCl3 / Cl2 gas etching source, and a first annular table is formed on the n++-GaN ohmic contact layer 4. The thickness of the first annular table is 1.2 to 1.5 μm, and then the device is wet-processed with a tetramethylammonium hydroxide solution (TMAH), and heated in a water bath at 80°C for 60 minutes to repair the etched damaged layer on the GaN surface. Correspondingly, Figure 4 A schematic diagram of the device structure after S8 is executed according to an embodiment of the present invention.

[0079] S9, forming an ohmic contact electrode 8 on the first annular mesa.

[0080] Specifically, on the first annular table, a vacuum electron beam evaporation device is used to sequentially evaporate Ti / Al / Ni / Au / Ti multilayer metals with thicknesses of 20nm, 140nm, 55nm, 45nm, and 150nm, respectively, and then the metal is stripped to form an ohmic contact electrode 8, and then the entire device is subjected to rapid thermal annealing at 750°C, annealing time of 3min, and annealing gas of nitrogen to form an ohmic contact. Correspondingly, Figure 5 A schematic diagram of the device structure after S9 is executed according to an embodiment of the present invention.

[0081] S10 , forming a Schottky contact electrode 9 on the n-GaN avalanche region 7 .

[0082] Specifically, on the upper surface of the n-GaN avalanche region 7, a vacuum electron beam evaporation device is used to sequentially evaporate Ti / Al / Ni multilayer metals with thicknesses of 50nm, 150nm, and 150nm, respectively, and then the Schottky contact electrode 9 is formed by metal stripping. Correspondingly, Figure 6 This is a schematic diagram of the device structure after S10 is executed according to an embodiment of the present invention.

[0083] S11 , etching the n-GaN drift region 5 , the n+-GaN avalanche termination region 6 and the n-GaN avalanche region 7 by using a self-aligned etching technique, thereby forming a second annular mesa on the upper surface of the n++-GaN ohmic contact layer 4 .

[0084] Specifically, a reactive ion etching (RIE) method is used to etch with a BCl3 / Cl2 gas etching source to form a second annular table on the n++-GaN ohmic contact layer 4, and the thickness of the second annular table is 400-600 nm. Then, the device is heated in a water bath at 80°C for 60 minutes using a tetramethylammonium hydroxide solution (TMAH) to repair the etched damaged layer on the GaN surface. Correspondingly, Figure 7 A schematic diagram of the device structure after S11 is executed according to an embodiment of the present invention.

[0085] S12, using radio frequency magnetron sputtering equipment to deposit SiO2 on the surface of the second annular table and to open holes to form a first passivation layer 10.

[0086] In the embodiment of the present invention, a RF magnetron sputtering device is first used, the RF power is 100W, the target distance is 20cm, and when the pressure of the reaction chamber is 0.4Pa, Ar and O2 are introduced with a flow ratio of 20:2 to sputter a SiO2 film with a thickness of 300nm, and then a reactive ion etching RIE method is used to etch the SiO2 film using a CF4 / O2 gas etching source to form a first passivation layer 10. Correspondingly, Figure 8 A schematic diagram of the device structure after S12 is executed according to an embodiment of the present invention.

[0087] S13 , forming a field plate metal 11 on the first passivation layer 10 and the Schottky contact electrode 9 .

[0088] Specifically, on the upper surface of the first passivation layer 10 and the Schottky contact electrode 9, a vacuum electron beam evaporation device is used to sequentially evaporate Ti / Al / Ni multilayer metals with thicknesses of 50nm, 150nm, and 150nm, respectively, and then the field plate metal 11 is formed by metal stripping. Correspondingly, Fig. 9 A schematic diagram of the device structure after S13 is executed according to an embodiment of the present invention.

[0089] S14, etching the n++-GaN ohmic contact layer 4 and the n-GaN drift region 5 using a self-aligned etching technique to obtain a first device.

[0090] In this embodiment, a reactive ion etching (RIE) method is used to etch with a BCl3 / Cl2 gas etching source to form a step on the n++-GaN ohmic contact layer 4, with a step thickness of 600-800 nm, to obtain a first device. Then, a tetramethylammonium hydroxide solution (TMAH) is used to heat the first device in a water bath at 80°C for 60 minutes to repair the etched damaged layer on the GaN surface. Correspondingly, Fig.10 A schematic diagram of the device structure after S14 is executed according to an embodiment of the present invention.

[0091] S15, using radio frequency magnetron sputtering equipment to deposit SiO2 on the upper surface of the first device and to open holes to form a second passivation layer 12, thereby obtaining a gallium nitride IMPATT diode.

[0092] In the embodiment of the present invention, a RF magnetron sputtering device is first used, the RF power is 100W, the target distance is 20cm, and when the pressure of the reaction chamber is 0.4Pa, Ar and O2 are introduced with a flow ratio of 20:2 to sputter a SiO2 film with a thickness of 600nm. Then, a reactive ion etching RIE method is used to etch the SiO2 film using a CF4 / O2 gas etching source to form a second passivation layer 12. Correspondingly, Figure 1 That is, a schematic diagram of the device structure after S14 provided in the embodiment of the present invention is executed.

[0093] It should be noted that the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention.

[0094] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0095] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A gallium nitride IMPATT diode, characterized in that: The gallium nitride IMPATT diode has a bilaterally symmetrical structure, comprising: a substrate layer (1), an AlN nucleation layer (2), a GaN buffer layer (3), and an n++-GaN ohmic contact layer (4) arranged in sequence from bottom to top; The n++-GaN ohmic contact layer (4) is provided with a first region, a second region and a third region; the first region and the third region are symmetrically distributed along the vertical central axis of the second region; the upper surface of the n++-GaN ohmic contact layer (4) is provided with a first groove and a second groove; the first groove is an L-shaped groove and is provided on one side of the upper surface of the n++-GaN ohmic contact layer (4); the first region is provided between the first groove and the second groove; the second groove is provided between the first region and the second region; The first region and the second region both comprise: an n-GaN drift region (5), an n+-GaN avalanche termination region (6) and an n-GaN avalanche region (7) arranged in sequence from bottom to top; the second region is also provided with a Schottky contact electrode (9); the Schottky contact electrode (9) is located on the upper surface of the n-GaN avalanche region (7) of the second region; the n+-GaN avalanche termination region (6), the n-GaN avalanche region (7) and the Schottky contact electrode (9) of the second region have equal widths and are smaller than the width of the n-GaN drift region (5) of the second region; The n-GaN drift region (5), the n+-GaN avalanche termination region (6) and the n-GaN avalanche region (7) of the first region have equal widths; the first groove and the outer surface of the first region away from the second region are covered with an ohmic contact electrode (8); the outer surface of the second region facing upwards is covered with a first passivation layer (10); the first passivation layer (10) is provided with a first notch along the vertical center axis of the second region; the outer surface of the first passivation layer (10) facing upwards is covered with a field plate metal (11); the field plate metal (11) is in contact with the Schottky contact electrode (9) along the first notch; the second groove, a partial area of ​​the outer surface of the ohmic contact electrode (8), the outer surface of the field plate metal (11), the outer surface of the second region and the outer surface of the first region are all covered with a second passivation layer (12); the second passivation layer (12) is provided with a second notch along the vertical center axis of the second region.

2. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the n++-GaN ohmic contact layer (4) is n++-GaN, with a thickness of 0.5 to 2.5 μm and a doping concentration of 5×10 18 ~1×10 20 cm -3 .

3. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the n-GaN drift region (5) is n-GaN, with a thickness of 0.5 to 2 μm and a doping concentration of 0.1 to 1×10 17 cm -3 .

4. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the n+-GaN avalanche termination region (6) is n+-GaN, with a thickness of 0.1 to 1 μm and a doping concentration of 0.1 to 5×10 18 cm -3 .

5. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the n-GaN avalanche region (7) is n-GaN, with a thickness of 0.1 to 1 μm and a doping concentration of 0.1 to 5×10 17 cm -3 .

6. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the ohmic contact electrode (8) is Ti / Al / Ni / Au / Ni metal alloy, and the thickness is 400-600nm.

7. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the Schottky contact electrode (9) is Ni / Au / Ni metal alloy, and the thickness is 300-400 nm.

8. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the first passivation layer (10) and the second passivation layer (12) is SiO2; the thickness of the first passivation layer (10) is 300 to 500 nm, and the thickness of the second passivation layer (12) is 500 to 800 nm.

9. The gallium nitride IMPATT diode according to claim 1, characterized in that: The material of the field plate metal (11) is Ni / Au double-layer metal with a thickness of 100-200 nm.

10. A method for preparing a gallium nitride IMPATT diode, characterized in that: For preparing the gallium nitride IMPATT diode according to any one of claims 1 to 9, comprising: S1, selecting sapphire material as an initial material to form a substrate layer (1); S2, epitaxially growing an AlN nucleation layer (2) on the substrate layer (1) by using a metal organic chemical vapor deposition (MOCVD) method; S3, epitaxially growing a GaN buffer layer (3) on the AlN nucleation layer (2) by using a MOCVD method; S4, epitaxially growing an n++-GaN ohmic contact layer (4) on the GaN buffer layer (3) by using a MOCVD method; S5, epitaxially growing an n-GaN drift region (5) on the n++-GaN ohmic contact layer (4) by using a MOCVD method; S6, epitaxially growing an n+-GaN avalanche termination region (6) on the n-GaN drift region (5) by using a MOCVD method; S7, epitaxially growing an n-GaN avalanche region (7) on the n+-GaN avalanche termination region (6) by using a MOCVD method; S8, etching the n++-GaN ohmic contact layer (4), the n-GaN drift region (5), the n+-GaN avalanche termination region (6) and the n-GaN avalanche region (7) using an etching technology, thereby forming a first annular mesa on the upper surface of the n++-GaN ohmic contact layer (4); S9, forming an ohmic contact electrode (8) on the first annular table surface; S10, forming a Schottky contact electrode (9) on the n-GaN avalanche region (7); S11, etching the n-GaN drift region (5), the n+-GaN avalanche termination region (6) and the n-GaN avalanche region (7) using a self-aligned etching technique, thereby forming a second annular mesa on the upper surface of the n++-GaN ohmic contact layer (4); S12, using radio frequency magnetron sputtering equipment to deposit SiO2 on the surface of the second annular table and to open holes to form a first passivation layer (10); S13, forming a field plate metal (11) on the first passivation layer (10) and the Schottky contact electrode (9); S14, etching the n++-GaN ohmic contact layer (4) and the n-GaN drift region (5) using a self-aligned etching technique to obtain a first device; S15, using radio frequency magnetron sputtering equipment to deposit SiO2 on the upper surface of the first device and to open holes to form a second passivation layer (12), thereby obtaining the gallium nitride IMPATT diode.

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