Low-power-consumption GaN HEMT based on p-type AlGaN back barrier structure and preparation method of low-power-consumption GaN HEMT

Abstract

The invention relates to a low-power-consumption GaN HEMT based on a p-type AlGaN back barrier structure and a preparation method of the low-power-consumption GaN HEMT. The HEMT comprises a substrate, a nucleating layer, a buffer layer, a p-type AlGaN back barrier layer, a channel layer, an insertion layer, a top barrier layer and a cap layer which are sequentially arranged from bottom to top. Wherein the content of the Al component in the p-type AlGaN back barrier layer is x, and x ranges from 0 to 1; the source electrode extends into the top barrier layer from the upper surface of one end of the cap layer; the drain electrode extends into the top barrier layer from the upper surface of the other end of the cap layer; and the grid electrode is located between the source electrode and the drain electrode and located on the upper surface of the cap layer. According to the invention, the back barrier structure is made of the p-type AlGaN material, so that the leakage current passing through the buffer layer can be effectively reduced, the power consumption of the device is further reduced, and the breakdown characteristic of the device is improved while the reliability of the device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to a low-power consumption GaN HEMT based on a p-type AlGaN back barrier structure and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN) materials have a larger bandgap compared to traditional silicon (Si) materials. In addition, a two-dimensional electron gas can be formed at the interface of the heterojunction formed by aluminum gallium nitride (AlGaN) and GaN, with an electron mobility of up to 2200cm 2 / V·s, therefore, GaN devices have great advantages in the field of power electronics applications.

[0003] The epitaxial structure of current GaN high electron mobility transistors (HEMT) is mostly heteroepitaxial. Currently, conventional epitaxial structures are mainly realized based on heterogeneous substrates, nucleation layers, buffer layers, channel layers, and barrier layers.

[0004] Although great progress has been made in epitaxial technology, dislocations in GaN materials are still unavoidable. There are a large number of trap states in both the buffer layer and the channel layer. These trap states cause GaN devices to have large leakage currents under high-voltage operating conditions. The magnitude of the leakage current affects the on / off power consumption and breakdown characteristics of the GaN device. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a low-power GaN HEMT based on a p-type AlGaN back barrier structure and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] The first aspect of the present invention provides a low-power GaN HEMT based on a p-type AlGaN back barrier structure, comprising: a substrate, a nucleation layer, a buffer layer, a p-type AlGaN back barrier layer, a channel layer, an insertion layer, a top barrier layer and a cap layer arranged in sequence from bottom to top; wherein the content of the Al component in the p-type AlGaN back barrier layer is x, and x is 0 to 1;

[0007] A source electrode, located on an upper surface of one end of the cap layer and extending to the interior of the top barrier layer;

[0008] A drain electrode, located on the upper surface of the other end of the cap layer and extending to the interior of the top barrier layer;

[0009] The gate is located between the source and the drain and on the upper surface of the cap layer.

[0010] In one achievable method, it further includes:

[0011] A passivation layer covers the surfaces of the cap layer, the source electrode, the drain electrode and the gate electrode.

[0012] In one achievable manner, the material of the substrate includes: one of sapphire, Si, SiC and GaN.

[0013] In one achievable manner, the material of the nucleation layer includes AlN, and has a thickness of 30-200 nm.

[0014] In an achievable manner, the material of the buffer layer includes AlGaN, and the content of the Al component in the buffer layer decreases stepwise from bottom to top to x;

[0015] The thickness of the buffer layer is 0.1-3 μm.

[0016] In one achievable manner, the doping concentration of the p-type AlGaN back barrier layer is 10 15 ~10 20 cm -3 , thickness is 100~400nm.

[0017] In one achievable manner, the material of the channel layer includes GaN, and has a thickness of 100 to 800 nm;

[0018] The material of the insertion layer includes AlN, and the thickness is 1 to 3 nm;

[0019] The material of the top barrier layer includes AlGaN, and the thickness is 10-40nm;

[0020] The material of the cap layer includes GaN, and the thickness thereof is 1 to 3 nm;

[0021] The material of the source electrode and the drain electrode includes: one of Ti / Al laminated metal, Ti / Al / Ni / Au laminated metal and Ti / Al / Mo / Au laminated metal;

[0022] The material of the gate includes one of Ni / Au / Ni laminated metal, Ni / Au laminated metal, W / Au laminated metal and Mo / Au laminated metal.

[0023] The second aspect of the present invention provides a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure, which is used to prepare the low-power GaN HEMT based on a p-type AlGaN back barrier structure provided by the first aspect of the present invention, comprising the following steps:

[0024] S1: cleaning the surface of the substrate;

[0025] S2: preparing a nucleation layer on the upper surface of the substrate;

[0026] S3: preparing a buffer layer on the upper surface of the nucleation layer;

[0027] S4: growing p-type AlGaN with an Al component content of x on the upper surface of the buffer layer to form a p-type AlGaN back barrier layer; wherein x is 0 to 1;

[0028] S5: preparing a channel layer on the upper surface of the p-type AlGaN back barrier layer;

[0029] S6: preparing an insertion layer on the upper surface of the channel layer;

[0030] S7: preparing a top barrier layer on the upper surface of the insertion layer;

[0031] S8: preparing a cap layer on the upper surface of the top barrier layer;

[0032] S9: preparing a source electrode extending to the inside of the top barrier layer on the upper surface of one end of the cap layer, and preparing a drain electrode extending to the inside of the top barrier layer on the upper surface of the other end of the cap layer;

[0033] S10: preparing a gate on the upper surface of the cap layer between the source and the drain.

[0034] In one achievable manner, step S3 includes:

[0035] By using a metal organic chemical vapor deposition process, Al source, Ga source, hydrogen and ammonia are introduced into the reaction chamber at the same time, AlGaN is grown on the upper surface of the nucleation layer to form a buffer layer; wherein the flow rate of the Al source is gradually reduced in a step-by-step manner, and the content of the Al component in the buffer layer is gradually reduced in a step-by-step manner from bottom to top to x.

[0036] In one achievable manner, step S4 includes:

[0037] By using a metal organic chemical vapor deposition process, a p-type dopant, an Al source, a Ga source, hydrogen and ammonia are introduced into a reaction chamber at the same time, and a p-type AlGaN with an Al component content of x is grown on the upper surface of the buffer layer to form a p-type AlGaN back barrier layer.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The low-power consumption GaN HEMT based on a p-type AlGaN back barrier structure of the present invention adopts a p-type AlGaN material as a back barrier structure, controls the energy level height between the Fermi level and the bottom of the conduction band of the p-type AlGaN back barrier layer of the device by adjusting the doping concentration and the Al component content of the p-type AlGaN back barrier layer, raises the energy level of the epitaxial structure in a larger range, can suppress the leakage current formed by the two-dimensional electron gas in the channel layer through the trap state in the bulk material to a greater extent, effectively reduces the leakage current through the buffer layer, thereby reducing the power consumption of the device, and improving the breakdown characteristics of the device while improving the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic structural diagram of a low-power GaN HEMT based on a p-type AlGaN back barrier structure provided by an embodiment of the present invention;

[0041] Figure 2 It is a flowchart of the steps of a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure provided by an embodiment of the present invention.

[0042] Reference numerals:

[0043] 1: substrate; 2: nucleation layer; 3: buffer layer; 4: p-type AlGaN back barrier layer; 5: channel layer; 6: insertion layer; 7: top barrier layer; 8: cap layer; 9: source; 10: drain; 11: gate; 12: passivation layer. DETAILED DESCRIPTION

[0044] 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.

[0045] Embodiment 1

[0046] The first aspect of this embodiment provides a low-power GaN HEMT based on a p-type AlGaN back barrier structure. Figure 1 , Figure 1It is a structural schematic diagram of a low-power GaN HEMT based on a p-type AlGaN back barrier structure provided by an embodiment of the present invention. The low-power GaN HEMT based on a p-type AlGaN back barrier structure provided in this embodiment includes: a substrate 1, a nucleation layer 2, a buffer layer 3, a p-type AlGaN back barrier layer 4, a channel layer 5, an insertion layer 6, a top barrier layer 7, a cap layer 8, a source 9, a drain 10, a gate 11 and a passivation layer 12. Among them, the substrate 1, the nucleation layer 2, the buffer layer 3, the p-type AlGaN back barrier layer 4, the channel layer 5, the insertion layer 6, the top barrier layer 7 and the cap layer 8 are arranged in sequence from bottom to top, and the content of the Al component in the p-type AlGaN back barrier layer 4 is x, and x is 0 to 1. The source 9 extends from the upper surface of one end of the cap layer 8 to the inside of the top barrier layer 7. The drain 10 extends from the upper surface of the other end of the cap layer 8 to the inside of the top barrier layer 7. The gate electrode 11 is located between the source electrode 9 and the drain electrode 10 and is located on the upper surface of the cap layer 8. The passivation layer 12 covers the surfaces of the cap layer 8, the source electrode 9, the drain electrode 10 and the gate electrode 11.

[0047] In this embodiment, the doping ions of the p-type AlGaN back barrier layer 4 include Mg and Zn. Specifically, AlGaN material has a larger bandgap width compared to GaN, and has a larger bandgap width between the Fermi level and the bottom of the conduction band of the AlGaN material compared to the GaN material, thereby raising the energy level of the epitaxial structure above the back barrier layer 4 and reducing the leakage current of the buffer layer 3. In this embodiment, p-type AlGaN is used as the back barrier layer, which can make the Fermi level in the p-type AlGaN back barrier layer 4 closer to the top of the valence band on the basis of unintentionally doped AlGaN, thereby making the Fermi level of the p-type AlGaN back barrier layer 4 The bandgap width from the bottom of the conduction band is larger, thereby more effectively increasing the barrier height between the p-type AlGaN back barrier layer 4 and the channel layer 5, and as the effective doping concentration of the p-type AlGaN back barrier layer 4 increases, the barrier height will become higher, and a higher barrier height can better suppress the leakage current formed by the two-dimensional electron gas in the channel through the bulk material, thereby reducing the device power consumption and improving the breakdown characteristics and reliability of the device. Furthermore, this embodiment can further control the energy level height between the Fermi level and the bottom of the conduction band of the p-type AlGaN back barrier layer 4 of the device by adjusting the content of the Al component and the p-type doping concentration in the p-type AlGaN back barrier layer 4, and can suppress the leakage current formed by the two-dimensional electron gas in the channel layer 5 through the trap state in the bulk material to a greater extent. It should be understood that when x is 0, the material of the p-type AlGaN back barrier layer 4 is p-type GaN. When x is 1, the material of the p-type AlGaN back barrier layer 4 is p-type AlN. p-type AlGaN is AlGaN doped with Mg or Zn.

[0048] In this embodiment, the material of the substrate 1 includes: one of sapphire, Si, SiC and GaN. The material of the nucleation layer 2 includes AlN, and the thickness is 30-200 nm. The material of the buffer layer 3 includes AlGaN, and the content of the Al component in the buffer layer 3 gradually decreases from bottom to top in a step-by-step manner to x. The thickness of the buffer layer 3 is 0.1-3 μm. The doping concentration of the p-type AlGaN back barrier layer 4 is 10 15 ~10 20 cm -3 , thickness is 100~400nm.

[0049] Specifically, since the nucleation layer 2 has a relatively thick thickness, the content of the Al component in the buffer layer 3 gradually decreases in a step-by-step manner, and the Al content in the material of the top layer of the buffer layer 3 is the same as that of the p-type AlGaN back barrier layer 4. Therefore, in this embodiment, the nucleation layer 2 and the buffer layer 3 are used as a transition buffer structure between the substrate 1 and the p-type AlGaN back barrier layer 4, which can avoid the generation of a parasitic channel between the p-type AlGaN back barrier layer 4 and the buffer layer 3, and can effectively reduce the lattice mismatch and thermal mismatch in the epitaxial material, thereby improving the crystallization quality.

[0050] In this embodiment, the material of the channel layer 5 includes GaN, and the thickness is 100 to 800 nm. The material of the insertion layer 6 includes AlN, and the thickness is 1 to 3 nm. The material of the top barrier layer 7 includes AlGaN, and the thickness is 10 to 40 nm. The material of the cap layer 8 includes GaN, and the thickness is 1 to 3 nm. The materials of the source 9 and the drain 10 each include: one of Ti / Al laminated metal, Ti / Al / Ni / Au laminated metal, and Ti / Al / Mo / Au laminated metal. The material of the gate 11 includes: one of Ni / Au / Ni laminated metal, Ni / Au laminated metal, W / Au laminated metal, and Mo / Au laminated metal.

[0051] Furthermore, the material of the passivation layer 12 includes: one of SiN, SiO2, Al2O3 and HfO2. The channel layer 5 and the top barrier layer 7 are both unintentionally doped. The source 9 and the drain 10 are both ohmic contacts, and the gate 11 is a Schottky contact. Exemplarily, the Ti / Al / Ni / Au laminated metal is Ti, Al, Ni and Au stacked in sequence from bottom to top.

[0052] The second aspect of this embodiment provides a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure, which is used to prepare the low-power GaN HEMT based on a p-type AlGaN back barrier structure provided by the first aspect of this embodiment. Figure 2 , Figure 2The present invention provides a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure. The method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure provided in this embodiment includes the following steps:

[0053] S1: Cleaning the surface of substrate 1.

[0054] Specifically, S1 includes:

[0055] A material selected from sapphire, Si, SiC and GaN is obtained as a substrate 1, and the surface is cleaned and pretreated to eliminate surface dangling bonds, and is heat-treated at 900-1200° C. in a H2 atmosphere reaction chamber to remove surface contaminants.

[0056] S2: preparing a nucleation layer 2 on the upper surface of the substrate 1.

[0057] Specifically, S2 includes:

[0058] A metal organic chemical vapor deposition (MOCVD) process is adopted to deposit AlN with a thickness of 30 to 200 nm on the upper surface of the substrate 1 to form a nucleation layer 2 .

[0059] S3: preparing a buffer layer 3 on the upper surface of the nucleation layer 2 .

[0060] Step S3 includes:

[0061] By using a metal organic chemical vapor deposition process, Al source, Ga source, hydrogen and ammonia are introduced into the reaction chamber at the same time, AlGaN is grown on the upper surface of the nucleation layer 2 to form a buffer layer 3; wherein, the flow rate of the Al source is gradually reduced in a step-by-step manner, and the content of the Al component in the buffer layer 3 is gradually reduced from bottom to top in a step-by-step manner to x. Wherein, x is 0 to 1. The thickness of the buffer layer 3 is 0.1 to 3 μm. It should be understood that the flow rate of the Ga source remains unchanged, and as the flow rate of the Al source gradually decreases, the content of the Al component in AlGaN gradually decreases. By adjusting the flow rate ratio of the Al source and the Ga source, the content of the Al component in AlGaN can be adjusted.

[0062] S4: growing p-type AlGaN with an Al component content of x on the upper surface of the buffer layer 3 to form a p-type AlGaN back barrier layer 4, where x is 0-1.

[0063] Step S4 includes:

[0064] By using a metal organic chemical vapor deposition process, a p-type dopant, an Al source, a Ga source, hydrogen and ammonia are introduced into the reaction chamber at the same time, and a p-type AlGaN with an Al component content of x is grown on the upper surface of the buffer layer 3 to form a p-type AlGaN back barrier layer 4. The thickness of the p-type AlGaN back barrier layer 4 is 100 to 400 nm, the doping type is p-type doping, and the doping concentration is 10 15 ~10 20 cm -3 In this embodiment, the p-type dopant is a Mg source or a Zn source, and further, the Mg source is cyclopentadienyl magnesium (C5H5)2Mg.

[0065] S5 : forming a channel layer 5 on the upper surface of the p-type AlGaN back barrier layer 4 .

[0066] Specifically, S5 includes:

[0067] The MOCVD process is used to deposit GaN with a thickness of 100-800 nm on the upper surface of the p-type AlGaN back barrier layer 4 to form the channel layer 5 .

[0068] S6 : preparing an insertion layer 6 on the upper surface of the channel layer 5 .

[0069] Specifically, S6 includes:

[0070] The insertion layer 6 is formed by depositing AlN with a thickness of 1 to 3 nm on the upper surface of the channel layer 5 using the MOCVD process.

[0071] S7 : preparing a top barrier layer 7 on the upper surface of the insertion layer 6 .

[0072] Specifically, S7 includes:

[0073] By adopting the MOCVD process, AlGaN with a thickness of 10-40 nm is deposited on the upper surface of the insertion layer 6 to form a top barrier layer 7 .

[0074] S8: preparing a cap layer 8 on the upper surface of the top barrier layer 7 .

[0075] Specifically, S8 includes:

[0076] GaN with a thickness of 1 to 3 nm is deposited on the upper surface of the top barrier layer 7 by using the MOCVD process to form a cap layer 8 .

[0077] S9: preparing a source electrode 9 extending to the inside of the top barrier layer 7 on the upper surface of one end of the cap layer 8 , and preparing a drain electrode 10 extending to the inside of the top barrier layer 7 on the upper surface of the other end of the cap layer 8 .

[0078] Specifically, S9 includes:

[0079] A source groove is formed at one end of the cap layer 8, and a drain groove is formed at the other end of the cap layer 8. Both the source groove and the drain groove extend from the upper surface of the cap layer 8 to the inside of the top barrier layer 7. A source metal is deposited in the source groove by metal evaporation or magnetron sputtering to form a source 9, and a drain metal is deposited in the drain groove to form a drain 10.

[0080] In this embodiment, the source metal and the drain metal both include one of a Ti / Al stacked metal, a Ti / Al / Ni / Au stacked metal, and a Ti / Al / Mo / Au stacked metal.

[0081] S10 : forming a gate electrode 11 on the upper surface of the cap layer 8 between the source electrode 9 and the drain electrode 10 .

[0082] Specifically, S10 includes: using a metal evaporation or magnetron sputtering process to deposit a gate metal on the upper surface of the cap layer 8 between the source 9 and the drain 10 to form a gate 11. In this embodiment, the gate metal includes: one of Ni / Au / Ni laminated metal, Ni / Au laminated metal, W / Au laminated metal and Mo / Au laminated metal. There is a gap between the gate 11 and the source 9 and the drain 10.

[0083] In this embodiment, after step S10, the following step is further included:

[0084] The epitaxial wafer obtained in step S10 is placed in a plasma enhanced chemical vapor deposition (PECVD) reaction chamber, and a passivation layer 12 is deposited on the surface of the cap layer 8, the surface of the source electrode 9, the surface of the drain electrode 10, and the surface of the gate electrode 11. Specifically, the material of the passivation layer 12 includes: one of SiN, SiO2, Al2O3 and HfO2. Photolithography and etching are performed on the passivation layer 12 on the source electrode 9, the drain electrode 10 and the gate electrode 11 to form electrode contact holes.

[0085] The low-power GaN HEMT based on the p-type AlGaN back barrier structure provided in the present embodiment adopts the p-type AlGaN material as the back barrier structure. By adjusting the Al component content and the p-type doping concentration in the p-type AlGaN back barrier layer 4, the energy level height between the Fermi level and the bottom of the conduction band of the device p-type AlGaN back barrier layer 4 can be effectively controlled, and the energy level of the epitaxial structure can be raised in a larger range, which can suppress the two-dimensional electron gas in the channel layer 5 to a greater extent to form a leakage current through the trap state in the bulk material, effectively reduce the leakage current through the buffer layer 3, and thus reduce the power consumption of the device, improve the device reliability and improve the breakdown characteristics of the device; in addition, the present embodiment uses the nucleation layer 2 and the buffer layer 3 as a transition buffer structure between the substrate 1 and the p-type AlGaN back barrier layer 4, which can avoid the generation of a parasitic channel between the p-type AlGaN back barrier layer 4 and the buffer layer 3, and can effectively reduce the lattice mismatch and thermal mismatch in the epitaxial material, and improve the crystal quality.

[0086] Embodiment 2

[0087] On the basis of Example 1, this embodiment provides a low-power GaN HEMT based on a p-type AlGaN back barrier structure, including: a substrate 1, a nucleation layer 2, a buffer layer 3, a p-type AlGaN back barrier layer 4, a channel layer 5, an insertion layer 6, a top barrier layer 7, a cap layer 8, a source 9, a drain 10, a gate 11 and a passivation layer 12. The positional relationship of the various structures of the device provided in this embodiment is the same as that in Example 1, and will not be repeated here. In this embodiment, the material of the substrate 1 is silicon carbide, the thickness of the nucleation layer 2 is 200nm, the thickness of the buffer layer is 0.1μm, x is 0.1, and the material of the p-type AlGaN back barrier layer 4 is Al 0.1 GaN, thickness 100nm, doping concentration 10 17 cm -3 The thickness of the channel layer 5 is 100 nm. The thickness of the insertion layer 6 is 1 nm. The material of the top barrier layer 7 is Al 0.2 GaN, with a thickness of 10 nm, and the thickness of the cap layer 8 is 1 nm.

[0088] This embodiment provides a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure, comprising the following steps:

[0089] Step 1: Pre-treat the surface of the silicon carbide substrate to eliminate dangling bonds, thereby obtaining substrate 1.

[0090] Specifically, the silicon carbide substrate was immersed in an HF acid solution for 1 minute, and then ultrasonically cleaned in an acetone solution, an anhydrous ethanol solution, and deionized water for 10 minutes each, and the cleaned silicon carbide substrate was blown dry with nitrogen. The dried silicon carbide substrate was heat-treated in a H2 atmosphere reaction chamber at a temperature of 1000° C. to remove surface contaminants, thereby obtaining substrate 1.

[0091] Step 2: Place the substrate 1 in the MOCVD system, set the pressure of the reaction chamber to 20 Torr and the temperature to 900°C, and simultaneously introduce an Al source with a flow rate of 250 μmol / min, a hydrogen with a flow rate of 1200 sccm, and an ammonia with a flow rate of 3000 sccm into the reaction chamber to grow 200 nm thick AlN on the substrate 1 to obtain a nucleation layer 2.

[0092] Step 3: Al source, Ga source with a flow rate of 45 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time to grow 0.1 μm thick AlGaN on the nucleation layer 2 to obtain a buffer layer 3. In this step, the flow rate of the Al source is gradually reduced from 200 μmol / min to 10 μmol / min in a stepwise manner.

[0093] Step 4: At the same time, Al source with a flow rate of 20 μmol / min, Ga source with a flow rate of 90 μmol / min, Mg source or Zn source with a flow rate of 2 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber to grow a 100 nm thick layer on the buffer layer 3 with a doping concentration of 10 17 cm -3 p-type Al 0.1 GaN, and a p-type AlGaN back barrier layer 4 is obtained.

[0094] Step 5: Ga source with a flow rate of 90 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time to grow GaN with a thickness of 100 nm on the p-type AlGaN back barrier layer 4 to obtain a channel layer 5.

[0095] Step 6: Al source with a flow rate of 40 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time to grow AlN with a thickness of 1 nm on the channel layer 5 to obtain the insertion layer 6.

[0096] Step 7: Al source with a flow rate of 15 μmol / min, Ga source with a flow rate of 40 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time to grow Al with a thickness of 10 nm on the insertion layer 6. 0.2 GaN, and a top barrier layer 7 is obtained.

[0097] Step eight: simultaneously introduce a Ga source with a flow rate of 40 μmol / min, a hydrogen with a flow rate of 1200 sccm, and an ammonia with a flow rate of 3000 sccm into the reaction chamber to grow 1 nm thick GaN on the top barrier layer 7 to obtain a cap layer 8.

[0098] Step 9: Form a source groove at one end of the cap layer 8 and a drain groove at the other end of the cap layer 8. Both the source groove and the drain groove extend from the upper surface of the cap layer 8 to the inside of the top barrier layer 7. Then place the sample in a magnetron sputtering reaction chamber and maintain the reaction chamber pressure at 8.8×10 -2 Pa, using aluminum and titanium targets with a purity of 99.999%, Ti / Al metal is deposited in the source groove and the drain groove, and annealed at a high temperature of 830° C. for 30 seconds to obtain the source 9 and the drain 10.

[0099] Step 10: Place the sample obtained in step 9 in the metal evaporation reaction chamber and control the pressure of the reaction chamber to 8.8×10 -2 Pa, using nickel and gold targets with a purity of 99.999%, deposit metal Ni / Au / Ni with a thickness of 45nm / 200nm / 200nm on the upper surface of the cap layer 8 between the source 9 and the drain 10 as the gate 11.

[0100] Step 11: Place the sample obtained in step 10 into a PECVD reaction chamber, and deposit 20 nm thick SiN at a high temperature of 400° C. to obtain a passivation layer 12.

[0101] Step 12: Perform photolithography and etching on the passivation layer 12 on the source electrode 9, the drain electrode 10 and the gate electrode 11 to form electrode contact holes.

[0102] Embodiment 3

[0103] On the basis of Example 1, this embodiment provides a low-power GaN HEMT based on a p-type AlGaN back barrier structure, including: a substrate 1, a nucleation layer 2, a buffer layer 3, a p-type AlGaN back barrier layer 4, a channel layer 5, an insertion layer 6, a top barrier layer 7, a cap layer 8, a source 9, a drain 10, a gate 11 and a passivation layer 12. The positional relationship of the various structures of the device provided in this embodiment is the same as that in Example 1, and will not be repeated here. In this embodiment, the material of the substrate 1 is sapphire, the thickness of the nucleation layer 2 is 100nm, the thickness of the buffer layer is 2μm, x is 0.2, and the material of the p-type AlGaN back barrier layer 4 is Al 0.2 GaN, thickness 250nm, doping concentration 10 18 cm -3 The thickness of the channel layer 5 is 500 nm. The thickness of the insertion layer 6 is 2 nm. The material of the top barrier layer 7 is Al 0.3 GaN, thickness is 25nm, and the thickness of the cap layer 8 is 2nm.

[0104] This embodiment provides a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure, comprising the following steps:

[0105] Step 1: Pre-treat the surface of the sapphire substrate to eliminate dangling bonds, thereby obtaining substrate 1.

[0106] Specifically, the sapphire substrate was immersed in an HF acid solution for 1 minute, and then ultrasonically cleaned in an acetone solution, an anhydrous ethanol solution, and deionized water for 10 minutes each, and the cleaned sapphire substrate was blown dry with nitrogen. The dried sapphire substrate was heat-treated in a H2 atmosphere reaction chamber at 1000° C. to remove surface contaminants, thereby obtaining a substrate 1.

[0107] Step 2: Place the substrate 1 in the MOCVD system, set the pressure of the reaction chamber to 20 Torr and the temperature to 900°C, and simultaneously introduce an Al source with a flow rate of 275 μmol / min, a hydrogen with a flow rate of 1200 sccm, and an ammonia with a flow rate of 4000 sccm into the reaction chamber to grow 100 nm thick AlN on the substrate 1 to obtain a nucleation layer 2.

[0108] Step 3: Al source, Ga source with a flow rate of 40 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time to grow 2 μm thick AlGaN on the nucleation layer 2 to obtain the buffer layer 3. In this step, the flow rate of the Al source is gradually reduced from 275 μmol / min to 15 μmol / min in a stepwise manner.

[0109] Step 4: At the same time, an Al source with a flow rate of 30 μmol / min, a Ga source with a flow rate of 80 μmol / min, a Mg source or a Zn source with a flow rate of 3 μmol / min, a hydrogen gas with a flow rate of 1400 sccm, and an ammonia gas with a flow rate of 4000 sccm are introduced into the reaction chamber to grow a 250 nm thick layer on the buffer layer 3 with a doping concentration of 10 18 cm -3 p-type Al 0.2 GaN, and a p-type AlGaN back barrier layer 4 is obtained.

[0110] Step 5: Ga source with a flow rate of 80 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 4000 sccm are introduced into the reaction chamber at the same time to grow GaN with a thickness of 500 nm on the p-type AlGaN back barrier layer 4 to obtain a channel layer 5.

[0111] Step 6: Al source with a flow rate of 50 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 4000 sccm are introduced into the reaction chamber at the same time to grow AlN with a thickness of 2 nm on the channel layer 5 to obtain the insertion layer 6.

[0112] Step 7: Al source with a flow rate of 25 μmol / min, Ga source with a flow rate of 50 μmol / min, hydrogen with a flow rate of 1400 sccm, and ammonia with a flow rate of 4000 sccm are introduced into the reaction chamber at the same time to grow Al with a thickness of 25 nm on the insertion layer 6. 0.3 GaN, and a top barrier layer 7 is obtained.

[0113] Step eight: simultaneously introduce a Ga source with a flow rate of 50 μmol / min, a hydrogen with a flow rate of 1400 sccm, and an ammonia with a flow rate of 4000 sccm into the reaction chamber to grow 2 nm thick GaN on the top barrier layer 7 to obtain a cap layer 8.

[0114] Step 9: Form a source groove at one end of the cap layer 8 and a drain groove at the other end of the cap layer 8. Both the source groove and the drain groove extend from the upper surface of the cap layer 8 to the inside of the top barrier layer 7. Then place the sample in a magnetron sputtering reaction chamber and maintain the reaction chamber pressure at 8.8×10 -2 Pa, using aluminum and titanium targets with a purity of 99.999%, Ti / Al / Ni / Au metals are deposited in the source groove and the drain groove, and annealed at a high temperature of 830°C for 30s to obtain the source 9 and the drain 10.

[0115] Step 10: Place the sample obtained in step 9 in the metal evaporation reaction chamber and control the pressure of the reaction chamber to 8.8×10 -2Pa, using nickel and gold targets with a purity of 99.999%, deposit metal Ti / Au with a thickness of 40nm / 100nm on the upper surface of the cap layer 8 between the source 9 and the drain 10 as the gate 11.

[0116] Step 11: Place the sample obtained in step 10 into a PECVD reaction chamber, and deposit 30 nm thick SiN at a high temperature of 400° C. to obtain a passivation layer 12.

[0117] Step 12: Perform photolithography and etching on the passivation layer 12 on the source electrode 9, the drain electrode 10 and the gate electrode 11 to form electrode contact holes.

[0118] Embodiment 4

[0119] On the basis of Example 1, this embodiment provides a low-power GaN HEMT based on a p-type AlGaN back barrier structure, including: a substrate 1, a nucleation layer 2, a buffer layer 3, a p-type AlGaN back barrier layer 4, a channel layer 5, an insertion layer 6, a top barrier layer 7, a cap layer 8, a source 9, a drain 10, a gate 11 and a passivation layer 12. The positional relationship of the various structures of the device provided in this embodiment is the same as that in Example 1, and will not be repeated here. In this embodiment, the material of the substrate 1 is Si, the thickness of the nucleation layer 2 is 30nm, the thickness of the buffer layer is 3μm, x is 0.3, and the material of the p-type AlGaN back barrier layer 4 is Al 0.3 GaN, thickness 400nm, doping concentration 10 19 cm -3 The thickness of the channel layer 5 is 800 nm. The thickness of the insertion layer 6 is 3 nm. The material of the top barrier layer 7 is Al 0.4 GaN, thickness is 40nm. Cap layer 8 has a thickness of 3nm.

[0120] This embodiment provides a method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure, comprising the following steps:

[0121] Step 1: Pre-treat the surface of the Si material to eliminate dangling bonds to obtain a substrate 1.

[0122] Specifically, the Si substrate was immersed in an HF acid solution for 1 minute, and then ultrasonically cleaned in an acetone solution, an anhydrous ethanol solution, and deionized water for 10 minutes each, and the cleaned Si substrate was blown dry with nitrogen. The dried Si substrate was heat-treated in a H2 atmosphere reaction chamber at 1000° C. to remove surface contaminants, thereby obtaining a substrate 1.

[0123] Step 2: Place the substrate 1 in the MOCVD system, set the pressure of the reaction chamber to 20 Torr and the temperature to 900°C, and simultaneously introduce an Al source with a flow rate of 300 μmol / min, a hydrogen with a flow rate of 1400 sccm, and an ammonia with a flow rate of 6000 sccm into the reaction chamber to grow a 30 nm thick AlN on the substrate 1 to obtain a nucleation layer 2.

[0124] Step 3: Al source, Ga source with a flow rate of 35 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 3000 sccm are introduced into the reaction chamber at the same time to grow 3 μm thick AlGaN on the nucleation layer 2 to obtain a buffer layer 3. In this step, the flow rate of the Al source is gradually reduced from 300 μmol / min to 20 μmol / min in a stepwise manner.

[0125] Step 4: At the same time, Al source with a flow rate of 40 μmol / min, Ga source with a flow rate of 70 μmol / min, Mg source or Zn source with a flow rate of 4 μmol / min, hydrogen with a flow rate of 1500 sccm, and ammonia with a flow rate of 5000 sccm are introduced into the reaction chamber to grow a 400 nm thick and doping concentration of 10 on the buffer layer 3. 19 cm -3 p-type Al 0.3 GaN, and a p-type AlGaN back barrier layer 4 is obtained.

[0126] Step 5: Ga source with a flow rate of 70 μmol / min, hydrogen with a flow rate of 1200 sccm, and ammonia with a flow rate of 5000 sccm are introduced into the reaction chamber at the same time to grow GaN with a thickness of 800 nm on the p-type AlGaN back barrier layer 4 to obtain a channel layer 5.

[0127] Step 6: Al source with a flow rate of 60 μmol / min, hydrogen with a flow rate of 1400 sccm, and ammonia with a flow rate of 5000 sccm are introduced into the reaction chamber at the same time to grow AlN with a thickness of 3 nm on the channel layer 5 to obtain the insertion layer 6.

[0128] Step 7: Al source with a flow rate of 45 μmol / min, Ga source with a flow rate of 60 μmol / min, hydrogen with a flow rate of 1500 sccm, and ammonia with a flow rate of 5000 sccm are introduced into the reaction chamber at the same time to grow Al with a thickness of 40 nm on the insertion layer 6. 0.4 GaN, and a top barrier layer 7 is obtained.

[0129] Step eight: simultaneously introduce a Ga source with a flow rate of 60 μmol / min, a hydrogen with a flow rate of 1500 sccm, and an ammonia with a flow rate of 5000 sccm into the reaction chamber to grow 3 nm thick GaN on the top barrier layer 7 to obtain a cap layer 8.

[0130] Step 9: Form a source groove at one end of the cap layer 8 and a drain groove at the other end of the cap layer 8. Both the source groove and the drain groove extend from the upper surface of the cap layer 8 to the inside of the top barrier layer 7. Then place the sample in a magnetron sputtering reaction chamber and maintain the reaction chamber pressure at 8.8×10 -2 Pa, using aluminum and titanium targets with a purity of 99.999%, Ti / Al / Mo / Au metal is deposited in the source groove and the drain groove, and annealed at a high temperature of 830°C for 30s to obtain the source 9 and the drain 10.

[0131] Step 10: Place the sample obtained in step 9 in the metal evaporation reaction chamber and control the pressure of the reaction chamber to 8.8×10 -2 Pa, using nickel and gold targets with a purity of 99.999%, deposit metal Ti / Au with a thickness of 60nm / 200nm on the upper surface of the cap layer 8 between the source 9 and the drain 10 as the gate 11.

[0132] Step 11: Place the sample obtained in step 10 into a PECVD reaction chamber, and deposit 40 nm thick SiN at a high temperature of 400° C. to obtain a passivation layer 12.

[0133] Step 12: Perform photolithography and etching on the passivation layer 12 on the source electrode 9, the drain electrode 10 and the gate electrode 11 to form electrode contact holes.

[0134] 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 protection scope of the present invention.

Claims

1. A low-power GaN HEMT based on a p-type AlGaN back barrier structure, characterized in that: include: A substrate, a nucleation layer, a buffer layer, a p-type AlGaN back barrier layer, a channel layer, an insertion layer, a top barrier layer and a cap layer are sequentially arranged from bottom to top; wherein the content of the Al component in the p-type AlGaN back barrier layer is x, and x is 0 to 1; A source electrode, located on an upper surface of one end of the cap layer and extending to the interior of the top barrier layer; A drain electrode, located on the upper surface of the other end of the cap layer and extending to the interior of the top barrier layer; The gate is located between the source and the drain and on the upper surface of the cap layer.

2. A low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 1, characterized in that: Also includes: A passivation layer covers the surfaces of the cap layer, the source electrode, the drain electrode and the gate electrode.

3. The low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 1, characterized in that: The material of the substrate includes: one of sapphire, Si, SiC and GaN.

4. The low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 1, characterized in that: The material of the nucleation layer includes AlN, and the thickness is 30-200 nm.

5. The low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 1, characterized in that: The material of the buffer layer includes AlGaN, and the content of the Al component in the buffer layer decreases stepwise from bottom to top to x; The thickness of the buffer layer is 0.1-3 μm.

6. The low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 1, characterized in that: The doping concentration of the p-type AlGaN back barrier layer is 10 15 ~10 20 cm -3 , thickness is 100~400nm.

7. The low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 1, characterized in that: The material of the channel layer includes GaN, and the thickness is 100-800nm; The material of the insertion layer includes AlN, and the thickness is 1 to 3 nm; The material of the top barrier layer includes AlGaN, and the thickness is 10-40nm; The material of the cap layer includes GaN, and the thickness thereof is 1 to 3 nm; The material of the source electrode and the drain electrode includes: one of Ti / Al laminated metal, Ti / Al / Ni / Au laminated metal and Ti / Al / Mo / Au laminated metal; The material of the gate includes one of Ni / Au / Ni laminated metal, Ni / Au laminated metal, W / Au laminated metal and Mo / Au laminated metal.

8. A method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure, characterized in that: The method for preparing the low-power consumption GaN HEMT based on the p-type AlGaN back barrier structure according to any one of claims 1 to 7 comprises the following steps: S1: cleaning the surface of the substrate; S2: preparing a nucleation layer on the upper surface of the substrate; S3: preparing a buffer layer on the upper surface of the nucleation layer; S4: growing p-type AlGaN with an Al component content of x on the upper surface of the buffer layer to form a p-type AlGaN back barrier layer; wherein x is 0 to 1; S5: preparing a channel layer on the upper surface of the p-type AlGaN back barrier layer; S6: preparing an insertion layer on the upper surface of the channel layer; S7: preparing a top barrier layer on the upper surface of the insertion layer; S8: preparing a cap layer on the upper surface of the top barrier layer; S9: preparing a source electrode extending to the inside of the top barrier layer on the upper surface of one end of the cap layer, and preparing a drain electrode extending to the inside of the top barrier layer on the upper surface of the other end of the cap layer; S10: preparing a gate on the upper surface of the cap layer between the source and the drain.

9. The method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 8, characterized in that: Step S3 includes: By using a metal organic chemical vapor deposition process, Al source, Ga source, hydrogen and ammonia are introduced into the reaction chamber at the same time, AlGaN is grown on the upper surface of the nucleation layer to form a buffer layer; wherein the flow rate of the Al source is gradually reduced in a step-by-step manner, and the content of the Al component in the buffer layer is gradually reduced in a step-by-step manner from bottom to top to x.

10. The method for preparing a low-power GaN HEMT based on a p-type AlGaN back barrier structure according to claim 8, characterized in that: Step S4 includes: By using a metal organic chemical vapor deposition process, a p-type dopant, an Al source, a Ga source, hydrogen and ammonia are introduced into a reaction chamber at the same time, and a p-type AlGaN with an Al component content of x is grown on the upper surface of the buffer layer to form a p-type AlGaN back barrier layer.

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