Transistor epitaxial wafer, manufacturing method thereof and transistor

Abstract

The invention relates to a transistor epitaxial wafer, a manufacturing method thereof and a transistor. The high-resistance layer comprises a high-resistance superlattice layer, the high-resistance superlattice layer comprises an AlGaN layer and a GaN layer which are alternately arranged in a stacked mode, compared with GaN, the lattice constant of AlGaN is smaller, and therefore the average lattice constant of the high-resistance superlattice layer based on the AlGaN layer and the GaN layer which are alternately arranged is smaller than that of a conventional high-resistance layer based on the GaN layer, and the average lattice constant of the high-resistance superlattice layer based on the AlGaN layer and the GaN layer which are alternately arranged is smaller than that of the conventional high-resistance layer based on the GaN layer. The high-resistance layer with a small lattice constant is more favorable for realizing doping, so that the background doping of the high-resistance layer can be remarkably improved by the high-resistance superlattice layer; meanwhile, in the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle is larger than that of the AlGaN layers on the two sides, the AlGaN layers with the low Al concentration are adopted for transition on the two sides, and dislocation between the AlGaN layers and the GaN layers is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a transistor epitaxial wafer, a manufacturing method thereof, and a transistor. Background Art

[0002] In a semiconductor silicon-based high electron mobility transistor (HEMT), the main function of C doping (i.e., carbon doping) is to control the properties of the semiconductor, which is a process of artificially introducing impurities. For a silicon-based high electron mobility transistor, the introduction of dopants will change the energy band structure of the semiconductor. This change in the energy band structure is crucial for the high-frequency application of the high electron mobility transistor. The height of C doping is also crucial for optimizing the performance of the high electron mobility device. For example, by changing the doping concentration, the threshold voltage of the high electron mobility transistor can be adjusted to make it more suitable for working in different application environments. At the same time, the optimized doping concentration can also enhance the breakdown voltage of the high electron mobility device, thereby improving its stability and reliability. Generally speaking, an appropriate C doping height can improve the working efficiency and service life of the high electron mobility device while maintaining the performance of the semiconductor material.

[0003] However, in the current high electron mobility transistor epitaxial wafers, generally a single-structured C-doped GaN layer is used as the high-resistance layer, and its corresponding C doping concentration is limited and cannot be further improved.

[0004] Therefore, there is an urgent need for a technical solution to effectively increase the background doping concentration of the GaN high-resistance layer in the high electron mobility transistor epitaxial wafer. Summary of the Invention

[0005] In view of the above deficiencies of the prior art, the purpose of the present application is to provide a technical solution for a high electron mobility transistor epitaxial wafer. Based on the alternately stacked AlGaN layer and GaN layer, a high-resistance superlattice layer is designed. Compared with the conventional high-resistance layer based on the GaN layer, its average lattice constant is smaller, and the barrier layer has different absorptions of doping factors in different-structured high-resistance layers, making the high-resistance layer with a small lattice constant more conducive to doping, and thus can increase the background doping concentration of the high-resistance layer in the high electron mobility transistor epitaxial wafer.

[0006] The present invention provides a transistor epitaxial wafer, which is a high electron mobility transistor epitaxial wafer and at least includes a substrate, a first buffer layer, a second buffer layer, a transition layer, a high-resistance layer, a channel layer, and a barrier layer that are sequentially stacked from bottom to top;

[0007] Among them, the high-resistance layer includes a high-resistance superlattice layer, the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers, and along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than that of the AlGaN layers on both sides.

[0008] In the above transistor epitaxial wafer, the high-resistance layer includes a high-resistance superlattice layer, and the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Compared with GaN, the lattice constant of AlGaN is smaller. Therefore, the average lattice constant of the high-resistance superlattice layer based on the alternating AlGaN layers and GaN layers is smaller than the average lattice constant of the conventional high-resistance layer based on GaN layers. And the barrier layer has different adsorption of doping factors in high-resistance layers with different structures, making the high-resistance layer with a smaller lattice constant more conducive to doping. Therefore, the high-resistance superlattice layer of the present invention can significantly improve the background doping of the high-resistance layer, such as carbon doping; at the same time, along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than that of the AlGaN layers on both sides, and the AlGaN layers with a lower Al concentration are used for transition on both sides, reducing the dislocations between the AlGaN layer and the GaN layer, effectively avoiding the lattice mismatch between the AlGaN layer and the GaN layer, and improving the lattice quality and the structural stability of the high-resistance superlattice layer.

[0009] Optionally, the high-resistance layer further includes a first carbon-doped GaN layer and a second carbon-doped GaN layer. The first carbon-doped GaN layer is disposed on the transition layer, the high-resistance superlattice layer is disposed on the first carbon-doped GaN layer, the second carbon-doped GaN layer is disposed on the high-resistance superlattice layer, and the channel layer is disposed on the second carbon-doped GaN layer.

[0010] Optionally, the high-resistance superlattice layer includes a first high-resistance superlattice layer, a second high-resistance superlattice layer, and a third high-resistance superlattice layer that are sequentially stacked from bottom to top. The first high-resistance superlattice layer, the second high-resistance superlattice layer, and the third high-resistance superlattice layer respectively include alternately stacked AlGaN layers and GaN layers.

[0011] Optionally, the first high-resistance superlattice layer includes N AlGaN layers and N GaN layers, the second high-resistance superlattice layer includes M AlGaN layers and M GaN layers, and the third high-resistance superlattice layer includes N AlGaN layers and N GaN layers, where M is greater than N.

[0012] Optionally, the Al content of the AlGaN layer in the second high-resistance superlattice layer is greater than that of the AlGaN layer in the first high-resistance superlattice layer, and the Al content of the AlGaN layer in the second high-resistance superlattice layer is greater than that of the AlGaN layer in the third high-resistance superlattice layer.

[0013] Optionally, the Al content of the AlGaN layer in the first high-resistance superlattice layer is 5% - 10%, the Al content of the AlGaN layer in the second high-resistance superlattice layer is 25% - 30%, and the Al content of the AlGaN layer in the third high-resistance superlattice layer is 5% - 10%.

[0014] Based on the same inventive concept, the present invention also provides a method for fabricating a transistor epitaxial wafer, where the transistor epitaxial wafer is a high electron mobility transistor epitaxial wafer, including:

[0015] Providing a substrate and forming a first buffer layer, a second buffer layer, and a transition layer sequentially stacked on the substrate;

[0016] Forming a first carbon-doped GaN layer on the transition layer;

[0017] Forming a high-resistance superlattice layer on the first carbon-doped GaN layer;

[0018] Forming a second carbon-doped GaN layer on the high-resistance superlattice layer; and

[0019] Forming a channel layer and a barrier layer sequentially stacked on the second carbon-doped GaN layer;

[0020] Wherein, the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than that of the AlGaN layers on both sides.

[0021] In the method for manufacturing the transistor epitaxial wafer described above, the formed high-resistance layer includes a high-resistance superlattice layer, and the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Compared with GaN, the lattice constant of AlGaN is smaller. Therefore, the average lattice constant of the high-resistance superlattice layer based on the alternately stacked AlGaN layers and GaN layers is smaller than the average lattice constant of the conventional high-resistance layer based on GaN layers. The barrier layer has different adsorption of doping factors in high-resistance layers with different structures, making the high-resistance layer with a smaller lattice constant more conducive to achieving doping. Therefore, the high-resistance superlattice layer of the present invention can significantly improve the background doping of the high-resistance layer, such as carbon doping. At the same time, along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than that of the AlGaN layers on both sides. The AlGaN layers with a lower Al concentration are used for transition on both sides, reducing the dislocations between the AlGaN layer and the GaN layer, effectively avoiding the lattice mismatch between the AlGaN layer and the GaN layer, and improving the lattice quality and the structural stability of the high-resistance superlattice layer.

[0022] Optionally, an epitaxial growth process is used to form the first carbon-doped GaN layer on the transition layer; wherein, the growth pressure of the first carbon-doped GaN layer is 100-150 mbar, the growth temperature is 970-990 °C, the growth rate of TMGa is 2-3 μm / h, and the flow rate of NH3 is 10-15 slm.

[0023] Optionally, the high-resistance superlattice layer includes a first high-resistance superlattice layer, a second high-resistance superlattice layer, and a third high-resistance superlattice layer that are sequentially stacked from bottom to top. The first high-resistance superlattice layer, the second high-resistance superlattice layer, and the third high-resistance superlattice layer respectively include the alternately stacked AlGaN layers and the GaN layers. The step of forming the high-resistance superlattice layer on the first carbon-doped GaN layer includes:

[0024] An epitaxial growth process is used to form the first high-resistance superlattice layer on the first carbon-doped GaN layer. The first high-resistance superlattice layer includes N AlGaN layers and N GaN layers; wherein, the growth pressure of the first high-resistance superlattice layer is 125 mbar, the growth temperature is 940-960 °C, the growth rate of TMAl is 2-4 μm / h, the growth rate of TMGa is 3-4 μm / h, and the flow rate of NH3 is 2-5 slm;

[0025] The second high-resistance superlattice layer is formed on the first high-resistance superlattice layer by an epitaxial growth process. The second high-resistance superlattice layer includes M layers of the AlGaN layer and M layers of the GaN layer. Wherein, the growth pressure of the second high-resistance superlattice layer is 125 mbar, the growth temperature is 940 - 960 °C, the growth rate of TMAl is 4 - 6 μm / h, the growth rate of TMGa is 3 - 4 μm / h, and the flow rate of NH3 is 2 - 5 slm;

[0026] The third high-resistance superlattice layer is formed on the second high-resistance superlattice layer by an epitaxial growth process. The third high-resistance superlattice layer includes N layers of the AlGaN layer and N layers of the GaN layer. Wherein, the growth pressure of the third high-resistance superlattice layer is 125 mbar, the growth temperature is 940 - 960 °C, the growth rate of TMAl is 2 - 4 μm / h, the growth rate of TMGa is 3 - 4 μm / h, and the flow rate of NH3 is 2 - 5 slm;

[0027] Wherein, M is greater than N.

[0028] Optionally, the second carbon-doped GaN layer is formed on the third high-resistance superlattice layer by an epitaxial growth process. Wherein, the growth pressure of the second carbon-doped GaN layer is 100 - 150 mbar, the growth temperature is 970 - 990 °C, the growth rate of TMGa is 2 - 3 μm / h, and the flow rate of NH3 is 10 - 15 slm.

[0029] Based on the same inventive concept, the present invention also provides a transistor. The transistor is a high electron mobility transistor and includes a transistor epitaxial wafer as described in any one of the above, a source electrode, a gate electrode, and a drain electrode. The source electrode and the drain electrode are respectively disposed on the transistor epitaxial wafer and are in ohmic contact with the top of the transistor epitaxial wafer. The gate electrode is disposed on the transistor epitaxial wafer, and the gate electrode penetrates from the top of the transistor epitaxial wafer and extends into the barrier layer but is not in ohmic contact with the transistor epitaxial wafer.

[0030] In the above transistor, a high-resistance superlattice layer formed based on stacked and alternating AlGaN layers and GaN layers makes the average lattice constant of the high-resistance superlattice layer smaller than that of a conventional high-resistance layer based on GaN layers. A high-resistance layer with a small lattice constant is more conducive to doping. Therefore, the high-resistance superlattice layer of the present invention can significantly improve the background doping of the high-resistance layer, thereby reducing the buffer layer leakage of the high electron mobility transistor, alleviating the current collapse aggravated by buffer layer doping, increasing its breakdown voltage, and improving its dynamic on-resistance. At the same time, along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the middle AlGaN layer is greater than that of the AlGaN layers on both sides. The AlGaN layers with a lower Al concentration are used for transition on both sides, reducing the dislocations between the AlGaN layer and the GaN layer, effectively avoiding the lattice mismatch between the AlGaN layer and the GaN layer, improving the lattice quality and the structural stability of the high-resistance superlattice layer, and further enhancing the structural stability and electrical performance stability of the transistor. Description of the Drawings

[0031] Figure 1 FIG. 6 is a schematic structural diagram of a high electron mobility device epitaxial wafer in the prior art;

[0032] Figure 2 FIG. 10 is a schematic structural diagram of a high electron mobility device epitaxial wafer in an embodiment of the present invention;

[0033] Figure 3 is Figure 2 a partial structural diagram of the high-resistance layer 5 in FIG. 16;

[0034] Figure 4 is Figure 2 a partial structural diagram of the high-resistance layer 5 in FIG. 22;

[0035] Figure 5 FIG. 26 is a schematic diagram of the steps of a method for manufacturing a high electron mobility device epitaxial wafer in an embodiment of the present invention;

[0036] Figure 6 FIG. 30 is a schematic diagram of the adjustment and change of some process parameters over time in steps S2 to S4 in an embodiment of the present invention.

[0037] Figure 7 FIG. 34 is a schematic structural diagram of a high electron mobility transistor in an embodiment of the present invention.

[0038] Explanation of the Reference Numerals:

[0039] 1 - Substrate; 2 - First buffer layer; 21 - Al layer; 22 - AlN layer; 3 - Second buffer layer; 4 - Transition layer; 5 - High-resistance layer; 51 - First carbon-doped GaN layer; 52 - High-resistance superlattice layer; 53 - Second carbon-doped GaN layer; 52a - AlGaN layer; 52b - GaN layer; 521 - First high-resistance superlattice layer; 522 - Second high-resistance superlattice layer; 523 - Third high-resistance superlattice layer; 6 - Channel layer; 7 - Barrier layer; 8 - Cap layer; 9 - Source electrode; 10 - Gate electrode; 11 - Drain electrode; 12 - Passivation layer; 13 - Isolation structure. Detailed implementation manners

[0040] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0042] As described in the background art above, the inventors have found through research that an appropriate C doping height can improve the working efficiency and service life of high electron mobility devices while maintaining the performance of semiconductor materials.

[0043] Specifically, as Figure 1 shown is the structure of an epitaxial wafer of a high electron mobility device in the prior art, which includes a substrate 1, a first buffer layer 2, a second buffer layer 3, a transition layer 4, a high-resistance layer 5, a channel layer 6, a barrier layer 7, and a cap layer 8 that are stacked in sequence from bottom to top. Among them, an interface between the channel layer 6 and the barrier layer 7 forms a two-dimensional electron gas. The high-resistance layer 5 is located between the channel layer 6 and the transition layer 4 and exhibits high-resistance characteristics, which can improve the resistivity and breakdown voltage of the high electron mobility device. To further improve the high-resistance characteristics of the high-resistance layer, background doping such as carbon doping can be performed on the high-resistance layer. The superlattice structure formed by carbon doping can improve the high-resistance characteristics of the high electron mobility device and ensure the crystal quality at the same time.

[0044] Among them, the substrate 1 can be a silicon-based substrate, the first buffer layer 2 can be a composite structure of an Al layer 21 and an AlN layer 22, the second buffer layer 3 can be an AlGaN layer, the transition layer 4 can be a high-temperature undoped U-GaN layer, the high-resistance layer 5 can be a carbon-doped GaN layer, the channel layer 6 can be a high-temperature undoped U-GaN layer, the barrier layer 7 can be an AlGaN layer, and the cap layer 8 can be a high-temperature undoped P-GaN layer. The cap layer 8 can be retained or cancelled as the case may be. For details, reference can be made to the prior art and will not be elaborated here.

[0045] However, in current high electron mobility transistor epitaxial wafers, the structures of the carbon-doped high-resistance layers 5 are relatively single, and the corresponding carbon doping concentrations are limited, making it impossible to further improve the high-resistance characteristics of high electron mobility devices.

[0046] Based on this, this application hopes to provide a solution capable of solving the above technical problems, and its detailed content will be elaborated in the subsequent embodiments.

[0047] As Figures 2 - 3 shown, the present invention provides a high electron mobility transistor epitaxial wafer, which at least includes a substrate 1, a first buffer layer 2, a second buffer layer 3, a transition layer 4, a high-resistance layer 5, a channel layer 6, and a barrier layer 7 that are sequentially stacked from bottom to top;

[0048] Among them, the high-resistance layer 5 includes a high-resistance superlattice layer 52, and the high-resistance superlattice layer 52 includes alternately stacked AlGaN layers 52a and GaN layers 52b. Along the direction from the transition layer 4 to the channel layer 6, in the high-resistance superlattice layer 52, the Al content of the middle AlGaN layer 52a is greater than that of the AlGaN layers 52a on both sides.

[0049] Specifically, as Figures 2 - 3 shown, the high-resistance layer 5 further includes a first carbon-doped GaN layer 51 and a second carbon-doped GaN layer 53. The first carbon-doped GaN layer 51 is disposed on the transition layer 4, the high-resistance superlattice layer 52 is disposed on the first carbon-doped GaN layer 51, the second carbon-doped GaN layer 53 is disposed on the high-resistance superlattice layer 52, and the channel layer 6 is disposed on the second carbon-doped GaN layer 53.

[0050] Specifically, as Figure 4 shown, the high-resistance superlattice layer 52 includes a first high-resistance superlattice layer 521, a second high-resistance superlattice layer 522, and a third high-resistance superlattice layer 523 that are sequentially stacked from bottom to top. The first high-resistance superlattice layer 521, the second high-resistance superlattice layer 522, and the third high-resistance superlattice layer 523 each include alternately stacked AlGaN layers 52a and GaN layers 52b.

[0051] More specifically, the first high-resistance superlattice layer 521 includes N layers of AlGaN layers 52a and N layers of GaN layers 52b, the second high-resistance superlattice layer 522 includes M layers of AlGaN layers and M layers of GaN layers 52b, and the third high-resistance superlattice layer 523 includes N layers of AlGaN layers 52a and N layers of GaN layers 52b, where M is greater than N. Here, 1 layer of AlGaN layer 52a and an adjacent 1 layer of GaN layer 52b form one composite structure layer, or are denoted as 1 cycle loop.

[0052] In an alternative embodiment of the present invention, as Figure 4 shown, the first high-resistance superlattice layer 521 includes 3 layers of AlGaN layers 52a and 3 layers of GaN layers 52b, the second high-resistance superlattice layer 522 includes 14 layers of AlGaN layers and 14 layers of GaN layers 52b, and the third high-resistance superlattice layer 523 includes 3 layers of AlGaN layers 52a and 3 layers of GaN layers 52b, that is, N = 3 and M = 14. That is to say, the high-resistance superlattice layer 52 includes 20 layers of composite structure layers or 20 cycle loops.

[0053] It should be noted that N is not limited to 3 and M is not limited to 14. In other alternative embodiments of the present invention, the values of M and N can be flexibly selected as positive integers as long as M is greater than N, so that the number of composite structure layers of the second high-resistance superlattice layer 522 is greater than the number of composite structure layers of the first high-resistance superlattice layer 521 and the third high-resistance superlattice layer 523; at the same time, the number of composite structure layers of the first high-resistance superlattice layer 521 and the third high-resistance superlattice layer 523 is not necessarily exactly equal and can be flexibly designed according to the situation, which is not limited herein.

[0054] Specifically, as Figure 4 shown, the Al content of the AlGaN layer 52a in the second high-resistance superlattice layer 522 is greater than the Al content of the AlGaN layer 52a in the first high-resistance superlattice layer 521, and the Al content of the AlGaN layer 52a in the second high-resistance superlattice layer 522 is greater than the Al content of the AlGaN layer 52a in the third high-resistance superlattice layer 523. That is to say, the Al content of the AlGaN layer 52a in the middle second high-resistance superlattice layer 522 is the largest.

[0055] For example, in an alternative embodiment of the present invention, the Al content of the AlGaN layer 52a in the first high-resistance superlattice layer 521 is 5% - 10%, the Al content of the AlGaN layer 52a in the second high-resistance superlattice layer 522 is 25% - 30%, and the Al content of the AlGaN layer 52a in the third high-resistance superlattice layer 523 is 5% - 10%.

[0056] Thus, in the above high electron mobility transistor epitaxial wafer, the high-resistance superlattice layer 52 includes alternately stacked AlGaN layers 52a and GaN layers 52b. The lattice constant of AlGaN is smaller than that of GaN. Therefore, the average lattice constant of the high-resistance superlattice layer based on the alternating AlGaN layers and GaN layers is smaller than the average lattice constant of the conventional high-resistance layer based on GaN layers. The barrier layer adsorbs different doping factors in high-resistance layers with different structures, making the high-resistance layer with a smaller lattice constant more conducive to doping. Therefore, the high-resistance superlattice layer 52 of the present invention can significantly improve the background doping of the high-resistance layer 5, such as carbon doping. At the same time, along the direction from the transition layer 4 to the channel layer 6, in the high-resistance superlattice layer 52, the Al content of the middle AlGaN layer 52a is greater than that of the AlGaN layers 52a on both sides. The AlGaN layers 52a with a lower Al concentration are used for transition on both sides, reducing the dislocations between the AlGaN layer 52a and the GaN layer 52b, effectively avoiding the lattice mismatch between the AlGaN layer 52a and the GaN layer 52b, and improving the lattice quality and the structural stability of the high-resistance superlattice layer.

[0057] It can be understood that the substrate 1 can be a silicon-based substrate, the first buffer layer 2 can be a composite structure of an Al layer 21 and an AlN layer 22, the second buffer layer 3 can be an AlGaN layer, the transition layer 4 can be a high-temperature undoped U-GaN layer, the channel layer 6 can be a high-temperature undoped U-GaN layer, and the barrier layer 7 can be an AlGaN layer. The high electron mobility transistor epitaxial wafer further includes structural layers such as a cap layer. Details can be found in the prior art and will not be elaborated here.

[0058] The high electron mobility transistor epitaxial wafer of the present invention further includes a cap layer, a passivation layer, and electrodes (not shown in the figure). Details can be found in the prior art and will not be elaborated here.

[0059] Based on the same inventive concept, as Figure 5 shown, the present invention also provides a method for manufacturing a high electron mobility transistor epitaxial wafer, which includes:

[0060] S1. Providing a substrate and forming a first buffer layer, a second buffer layer, and a transition layer sequentially stacked on the substrate;

[0061] S2. Forming a first carbon-doped GaN layer on the transition layer;

[0062] S3. Forming a high-resistance superlattice layer on the first carbon-doped GaN layer;

[0063] S4. Forming a second carbon-doped GaN layer on the high-resistance superlattice layer; and

[0064] S5. Forming a channel layer and a barrier layer sequentially stacked on the second carbon-doped GaN layer;

[0065] Among them, the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than that of the AlGaN layers on both sides.

[0066] In the method for manufacturing the above-mentioned high electron mobility transistor epitaxial wafer, the manufactured high-resistance layer includes a high-resistance superlattice layer, and the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Compared with GaN, the lattice constant of AlGaN is smaller. Therefore, the average lattice constant of the high-resistance superlattice layer based on the alternating AlGaN layers and GaN layers is smaller than the average lattice constant of the conventional high-resistance layer based on GaN layers. And the barrier layer adsorbs different doping factors in high-resistance layers with different structures, making the high-resistance layer with a smaller lattice constant more conducive to doping. Therefore, the high-resistance superlattice layer of the present invention can significantly improve the background doping of the high-resistance layer, such as carbon doping; at the same time, along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than that of the AlGaN layers on both sides. The AlGaN layers with a lower Al concentration are used for transition on both sides, reducing the dislocations between the AlGaN layer and the GaN layer, effectively avoiding the lattice mismatch between the AlGaN layer and the GaN layer, and improving the lattice quality and the structural stability of the high-resistance superlattice layer.

[0067] Specifically, in step S1, as Figure 2 shown, a first buffer layer 2, a second buffer layer 3, and a transition layer 4 are sequentially formed on the substrate 1 by an epitaxial growth process. Among them, the substrate 1 can be a silicon-based substrate, the first buffer layer 2 can be a composite structure of an Al layer 21 and an AlN layer 22, the second buffer layer 3 can be an AlGaN layer, and the transition layer 4 can be a high-temperature undoped U-GaN layer.

[0068] Specifically, in step S2, as Figures 2 - 4 shown, a first carbon-doped GaN layer 51 is formed on the transition layer 4 by an epitaxial growth process. In an optional embodiment of the present invention, the epitaxial growth process parameters are as follows: the growth pressure is 100 - 150 mbar, the growth temperature is 970 - 990 °C, the growth rate of TMGa (i.e., trimethylgallium) is 2 - 3 μm / h, and the flow rate of NH3 is 10 - 15 slm. A first carbon-doped GaN layer 51 with a thickness of 0.5 μm is obtained by epitaxial growth.

[0069] Specifically, as Figures 3 - 4As shown, the high-resistance superlattice layer 52 includes a first high-resistance superlattice layer 521, a second high-resistance superlattice layer 522, and a third high-resistance superlattice layer 523 that are stacked in sequence from bottom to top. The first high-resistance superlattice layer 521, the second high-resistance superlattice layer 522, and the third high-resistance superlattice layer 523 respectively include AlGaN layers 52a and GaN layers 52b that are alternately stacked. The step S3 of forming the high-resistance superlattice layer 52 on the first carbon-doped GaN layer 51 includes:

[0070] S31. Use an epitaxial growth process to form the first high-resistance superlattice layer 521 on the first carbon-doped GaN layer 51. The first high-resistance superlattice layer 521 includes N AlGaN layers 52a and N GaN layers 52b. For example, the growth pressure is 125 mbar, the growth temperature is 940 - 960 °C, the growth rate of TMAl (trimethylaluminum) is 2 - 4 μm / h, the growth rate of TMGa is 3 - 4 μm / h, and the flow rate of NH3 is 2 - 5 slm;

[0071] S32. Use an epitaxial growth process to form the second high-resistance superlattice layer 522 on the first high-resistance superlattice layer 521. The second high-resistance superlattice layer 522 includes M AlGaN layers 52a and M GaN layers 52b. For example, the growth pressure is 125 mbar, the growth temperature is 940 - 960 °C, the growth rate of TMAl is 4 - 6 μm / h, the growth rate of TMGa is 3 - 4 μm / h, and the flow rate of NH3 is 2 - 5 slm;

[0072] S33. Use an epitaxial growth process to form the third high-resistance superlattice layer 523 on the second high-resistance superlattice layer 522. The third high-resistance superlattice layer 523 includes N AlGaN layers 52a and N GaN layers 52b. For example, the growth pressure is 125 mbar, the growth temperature is 940 - 960 °C, the growth rate of TMAl is 2 - 4 μm / h, the growth rate of TMGa is 3 - 4 μm / h, and the flow rate of NH3 is 2 - 5 slm;

[0073] Wherein, M is greater than N.

[0074] More specifically, in step S31, because there is a lattice mismatch in the transition region between the AlGaN layer 52a and the GaN layer 52b, a higher AL component will cause larger dislocations, resulting in a decrease in lattice quality. Therefore, a lower AL component growth is used for the transition, and N cycles of the AlGaN / GaN superlattice are grown to obtain the first high-resistance superlattice layer 521. In an alternative embodiment of the present invention, the thickness of the AlGaN layer 52a is 2 nm, the thickness of the GaN layer 52b is 20 nm, and the first high-resistance superlattice layer 521 includes 3 cycles, totaling 66 nm.

[0075] More specifically, in step S32, on the basis of the first high-resistance superlattice layer 521, M loops of ALGaN / GaN superlattice are continuously grown to obtain the second high-resistance superlattice layer 522. At this time, the growth temperature, growth pressure, growth rate of TMGa, and flow rate of NH3 are kept unchanged, and the flow rate of TMAL is appropriately increased to increase the content of Al component. In an alternative embodiment of the present invention, the thickness of the AlGaN layer 52a is 2 nm, the thickness of the GaN layer 52b is 20 nm, and the second high-resistance superlattice layer 522 includes 14 loops, with a total thickness of 308 nm.

[0076] More specifically, in step S33, on the basis of the second high-resistance superlattice layer 522, N loops of ALGaN / GaN superlattice are continuously grown to obtain the third high-resistance superlattice layer 523. At this time, the growth temperature, growth pressure, growth rate of TMGa, and flow rate of NH3 are kept unchanged, and the flow rate of TMAL is returned to the growth condition of the first high-resistance superlattice layer 521 to reduce the content of Al component again for lattice overmatching. In an alternative embodiment of the present invention, the thickness of the AlGaN layer 52a is 2 nm, the thickness of the GaN layer 52b is 20 nm, and the third high-resistance superlattice layer 523 includes 3 loops, with a total thickness of 66 nm.

[0077] Specifically, as Figure 6 shown, when forming the first high-resistance superlattice layer 521, the second high-resistance superlattice layer 522, and the third high-resistance superlattice layer 523, TMAl is introduced alternately at intervals. TMAl is turned on when forming the AlGaN layer 52a and turned off when forming the GaN layer 52b. As Figure 6 shown is a schematic diagram of the changes of TMAl, growth pressure, and growth temperature with time during steps S2 - S4 of the present invention. Among them, Press is the growth pressure and Temp is the growth temperature.

[0078] Specifically, in step S4, as Figures 3 - 4 shown, an epitaxial growth process is used to form the second carbon-doped GaN layer 53 on the third high-resistance superlattice layer 523. In an alternative embodiment of the present invention, the parameters of the epitaxial growth process are as follows: the growth pressure is 100 - 150 mbar, the growth temperature is 970 - 990 °C, the growth rate of TMGa is 2 - 3 μm / h, and the flow rate of NH3 is 10 - 15 slm. The second carbon-doped GaN layer 53 with a thickness of 0.7 μm is obtained through epitaxial growth.

[0079] Specifically, in step S5, as Figure 2As shown, an epitaxial growth process is used to form a channel layer 6, a barrier layer 7, a cap layer 8, and a passivation layer that are sequentially stacked on the second carbon-doped GaN layer 53, completing the growth of the overall structure of the high electron mobility transistor. A metal layer is formed on the passivation layer and etched to form electrodes.

[0080] Thus, in the present invention, the high-resistance layer 5 is mainly composed of a high-resistance superlattice layer formed by alternately stacking AlGaN layers and GaN layers. The lattice constant of GaN > the lattice constant of AlGaN > the lattice constant of AlN. This makes the average lattice constant of the high-resistance superlattice layer smaller than the average lattice constant of a conventional high-resistance layer based on a GaN layer. And the barrier layer has different absorptions of doping factors in high-resistance layers with different structures, making the high-resistance layer with a smaller lattice constant more conducive to doping. Therefore, the high-resistance superlattice layer of the present invention can significantly improve the background doping of the high-resistance layer. For example, in an optional embodiment of the present invention, on the premise of the same thickness and other parameter specifications, Figure 1 the carbon doping level of the high-resistance layer 5 in the high electron mobility transistor epitaxial wafer shown is (3 - 4)×10 18 , while after improvement, as shown in Figures 2 - 4 the carbon doping level of the high-resistance layer 5 in the high electron mobility transistor epitaxial wafer shown can reach (5 - 7)×10 19 ; at the same time, the influence of pressure and temperature on doping is also relatively large. The diffusion rate of dopants is faster under low-pressure conditions, and low temperature also helps to improve carbon doping. The improvement of carbon doping is achieved by comprehensively adjusting the changes in growth pressure, temperature, and growth mode.

[0081] In addition, based on the same inventive concept, the present invention also provides a high electron mobility transistor. As shown in Figure 7 it includes the above-mentioned high electron mobility transistor epitaxial wafer, a source electrode 9, a gate electrode 10, and a drain electrode 11. The source electrode 9 and the drain electrode 11 are respectively disposed on the high electron mobility transistor epitaxial wafer and are in ohmic contact with the top (cap layer 8 or barrier layer 7) of the high electron mobility transistor epitaxial wafer. The gate electrode 10 is disposed on the high electron mobility transistor epitaxial wafer. The gate electrode 10 penetrates from the top of the high electron mobility transistor and extends into the barrier layer 7 but is not in ohmic contact with the high electron mobility transistor.

[0082] Specifically, as shown in Figure 7As shown, based on the above-mentioned high electron mobility transistor epitaxial wafer, the fabrication of the high electron mobility transistor is completed based on deposition and etching processes. First, based on deposition and etching processes, a source electrode 9 and a drain electrode 11 are simultaneously formed on the cap layer 8 of the above-mentioned high electron mobility transistor epitaxial wafer. Then, a passivation layer 12 is formed based on the deposition process. After that, based on etching and deposition processes, a gate electrode 10 is formed, and the gate electrode 10 is not in ohmic contact with the high electron mobility transistor, but is insulated and isolated through a deposited dielectric layer. At the same time, an isolation structure 13 is also formed to isolate the device area through the isolation structure 13.

[0083] Among them, the cap layer 8 on the high electron mobility transistor epitaxial wafer can be cancelled or retained depending on the difference in the structure type of the transistor.

[0084] In the above-mentioned high electron mobility transistor, a high-resistance superlattice layer formed based on alternating stacked AlGaN layers and GaN layers makes the average lattice constant of the high-resistance superlattice layer smaller than the average lattice constant of a conventional high-resistance layer based on GaN layers. A high-resistance layer with a small lattice constant is more conducive to doping. Therefore, the high-resistance superlattice layer of the present invention can significantly improve the background doping of the high-resistance layer, thereby reducing the buffer layer leakage of the high electron mobility transistor, alleviating the current collapse aggravated due to buffer layer doping, increasing its breakdown voltage, and improving its dynamic on-resistance. At the same time, along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer in the middle position is greater than the Al content of the AlGaN layers on both sides. The AlGaN layers with lower Al concentrations are used for transition on both sides, reducing the dislocations between the AlGaN layer and the GaN layer, effectively avoiding the lattice mismatch between the AlGaN layer and the GaN layer, improving the lattice quality and the structural stability of the high-resistance superlattice layer, and further improving the structural stability and electrical performance stability of the high electron mobility transistor.

[0085] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A transistor epitaxial wafer, the transistor epitaxial wafer being a high electron mobility transistor epitaxial wafer, characterized in that, It at least includes a substrate, a first buffer layer, a second buffer layer, a transition layer, a high-resistance layer, a channel layer, and a barrier layer which are sequentially stacked from bottom to top; Wherein, the high-resistance layer includes a high-resistance superlattice layer, and the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer at the middle position is greater than that of the AlGaN layers on both sides.

2. The epitaxial wafer of a transistor according to claim 1, wherein The high-resistance layer further includes a first carbon-doped GaN layer and a second carbon-doped GaN layer. The first carbon-doped GaN layer is disposed on the transition layer, the high-resistance superlattice layer is disposed on the first carbon-doped GaN layer, the second carbon-doped GaN layer is disposed on the high-resistance superlattice layer, and the channel layer is disposed on the second carbon-doped GaN layer.

3. The epitaxial wafer of the transistor according to claim 2, wherein, The high-resistance superlattice layer includes a first high-resistance superlattice layer, a second high-resistance superlattice layer, and a third high-resistance superlattice layer which are sequentially stacked from bottom to top. The first high-resistance superlattice layer, the second high-resistance superlattice layer, and the third high-resistance superlattice layer respectively include alternately stacked AlGaN layers and GaN layers.

4. The epitaxial wafer of a transistor according to claim 3, wherein, The first high-resistance superlattice layer includes N AlGaN layers and N GaN layers. The second high-resistance superlattice layer includes M AlGaN layers and M GaN layers. The third high-resistance superlattice layer includes N AlGaN layers and N GaN layers, and M is greater than N.

5. The epitaxial wafer of a transistor according to claim 3, characterized in that, The Al content of the AlGaN layer in the second high-resistance superlattice layer is greater than that of the AlGaN layer in the first high-resistance superlattice layer, and the Al content of the AlGaN layer in the second high-resistance superlattice layer is greater than that of the AlGaN layer in the third high-resistance superlattice layer.

6. The epitaxial wafer of a transistor according to claim 5, wherein, The Al content of the AlGaN layer in the first high-resistance superlattice layer is 5% - 10%. The Al content of the AlGaN layer in the second high-resistance superlattice layer is 25% - 30%. The Al content of the AlGaN layer in the third high-resistance superlattice layer is 5% - 10%.

7. A manufacturing method of a transistor epitaxial wafer, the transistor epitaxial wafer being a high electron mobility transistor epitaxial wafer, characterized in that, Comprising: Providing a substrate and forming a first buffer layer, a second buffer layer, and a transition layer which are sequentially stacked on the substrate; Forming a first carbon-doped GaN layer on the transition layer; Forming a high-resistance superlattice layer on the first carbon-doped GaN layer; Forming a second carbon-doped GaN layer on the high-resistance superlattice layer; And Forming a channel layer and a barrier layer which are sequentially stacked on the second carbon-doped GaN layer; Wherein, the high-resistance superlattice layer includes alternately stacked AlGaN layers and GaN layers. Along the direction from the transition layer to the channel layer, in the high-resistance superlattice layer, the Al content of the AlGaN layer at the middle position is greater than that of the AlGaN layers on both sides.

8. The manufacturing method of the transistor epitaxial wafer according to claim 7, wherein, The first carbon-doped GaN layer is formed on the transition layer by an epitaxial growth process; wherein, the growth pressure of the first carbon-doped GaN layer is 100-150 mbar, the growth temperature is 970-990 °C, the growth rate of TMGa is 2-3 μm / h, and the flow rate of NH3 is 10-15 slm.

9. The manufacturing method of the transistor epitaxial wafer according to claim 7, wherein The high-resistance superlattice layer includes a first high-resistance superlattice layer, a second high-resistance superlattice layer, and a third high-resistance superlattice layer that are stacked in sequence from bottom to top. The first high-resistance superlattice layer, the second high-resistance superlattice layer, and the third high-resistance superlattice layer respectively include the AlGaN layer and the GaN layer that are stacked alternately. The step of forming the high-resistance superlattice layer on the first carbon-doped GaN layer includes: The first high-resistance superlattice layer is formed on the first carbon-doped GaN layer by an epitaxial growth process. The first high-resistance superlattice layer includes N layers of the AlGaN layer and N layers of the GaN layer; wherein, the growth pressure of the first high-resistance superlattice layer is 125 mbar, the growth temperature is 940-960 °C, the growth rate of TMAl is 2-4 μm / h, the growth rate of TMGa is 3-4 μm / h, and the flow rate of NH3 is 2-5 slm; The second high-resistance superlattice layer is formed on the first high-resistance superlattice layer by an epitaxial growth process. The second high-resistance superlattice layer includes M layers of the AlGaN layer and M layers of the GaN layer; wherein, the growth pressure of the second high-resistance superlattice layer is 125 mbar, the growth temperature is 940-960 °C, the growth rate of TMAl is 4-6 μm / h, the growth rate of TMGa is 3-4 μm / h, and the flow rate of NH3 is 2-5 slm; The third high-resistance superlattice layer is formed on the second high-resistance superlattice layer by an epitaxial growth process. The third high-resistance superlattice layer includes N layers of the AlGaN layer and N layers of the GaN layer; wherein, the growth pressure of the third high-resistance superlattice layer is 125 mbar, the growth temperature is 940-960 °C, the growth rate of TMAl is 2-4 μm / h, the growth rate of TMGa is 3-4 μm / h, and the flow rate of NH3 is 2-5 slm; Wherein, M is greater than N.

10. The manufacturing method of the transistor epitaxial wafer according to claim 9, characterized in that, The second carbon-doped GaN layer is formed on the third high-resistance superlattice layer by an epitaxial growth process; wherein, the growth pressure of the second carbon-doped GaN layer is 100-150 mbar, the growth temperature is 970-990 °C, the growth rate of TMGa is 2-3 μm / h, and the flow rate of NH3 is 10-15 slm.

11. A transistor, the transistor being a high electron mobility transistor, characterized in that, It includes the transistor epitaxial wafer, source electrode, gate electrode, and drain electrode according to any one of claims 1-6. The source electrode and the drain electrode are respectively disposed on the transistor epitaxial wafer and are in ohmic contact with the top of the transistor epitaxial wafer. The gate electrode is disposed on the transistor epitaxial wafer, and the gate electrode penetrates from the top of the transistor epitaxial wafer and extends into the barrier layer but is not in ohmic contact with the transistor epitaxial wafer.

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