Gallium nitride semiconductor device and preparation method thereof

Abstract

The present invention provides a gallium nitride semiconductor device and a method for fabricating the same. The method includes forming a carbon-doped layer between a buffer layer and a channel layer using an extrinsic dopant via an external carbon doping method. The growth conditions for the external carbon doping method are: a substrate surface temperature greater than or equal to 900°C, a growth pressure greater than or equal to 50 mbar, and a V / III ratio greater than or equal to 200. The gallium nitride semiconductor device exhibits uniform carbon concentration and good device breakdown uniformity.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a gallium nitride semiconductor device and a method for preparing the same. Background Art

[0002] Power devices typically require high breakdown voltage, low on-resistance, and fast switching capabilities. Traditionally, the power semiconductor market has been dominated by silicon power devices. Over the past 20 years, the performance of silicon power devices has approached their theoretical limits, making further improvements extremely difficult.

[0003] Compared to silicon or gallium arsenide, gallium nitride (GaN) semiconductors have a wide bandgap (Eg = 3.4eV), excellent thermal stability, high breakdown voltage, high electron saturation drift velocity, and excellent radiation resistance. In addition, compared to silicon power semiconductors, GaN power semiconductors have low-temperature resistance, which can reduce power conversion losses caused by power semiconductors and minimize power losses in power conversion systems. GaN semiconductor devices have become the new generation of power devices with advantages such as low loss, high voltage resistance, fast switching capability, and high-temperature operation capability. The demand for GaN semiconductors in industrial electronics, power transmission, smart homes, electric vehicles, rail transportation and other fields continues to expand.

[0004] Gallium nitride semiconductor devices (GaN High Electron Mobility Transistors, GaNHEMTs) are high-voltage devices that typically incorporate carbon into the buffer layer via an intrinsic or auto-doping method to achieve a high vertical breakdown voltage. This method controls the concentration of carbon doping by controlling growth conditions at low pressure, a low V / III ratio, and low temperatures. However, due to its high sensitivity to growth conditions, controlling the concentration and uniformity of the incorporated carbon is difficult. Furthermore, due to the low V / III ratio and low growth temperature, the crystal quality obtained using this method is poor, with issues such as poor carbon doping uniformity and poor breakdown uniformity. Summary of the Invention

[0005] A first object of the present invention is to provide a method for preparing a gallium nitride semiconductor device with uniform carbon concentration and good device breakdown uniformity.

[0006] A second object of the present invention is to provide a gallium nitride semiconductor device with uniform carbon concentration and good device breakdown uniformity.

[0007] To achieve the first objective, the present invention provides a method for preparing a gallium nitride semiconductor device, comprising forming a carbon-doped layer by an external carbon doping method using an extrinsic dopant; the growth conditions of the external carbon doping method are: a substrate surface temperature greater than or equal to 900°C, a growth pressure greater than or equal to 50 mbar, and a V / III ratio greater than or equal to 200.

[0008] A preferred solution is that the carbon-doped layer includes a carbon-doped high-resistance layer and an unintentionally doped layer, the carbon concentration of the carbon-doped high-resistance layer is greater than that of the unintentionally doped layer, and the unintentionally doped layer is located between the buffer layer and the carbon-doped high-resistance layer.

[0009] A preferred solution is that the carbon-doped layer includes a carbon-doped high-resistance layer and an unintentionally doped layer, the carbon concentration of the carbon-doped high-resistance layer is greater than that of the unintentionally doped layer, and the unintentionally doped layer is located within the carbon-doped high-resistance layer.

[0010] A further solution is that the carbon-doped high-resistance layer includes a carbon-doped superlattice layer and a carbon-doped gallium nitride layer, and the carbon-doped superlattice layer is a carbon-doped gallium nitride superlattice layer, a carbon-doped aluminum gallium nitrogen superlattice layer or a carbon-doped aluminum nitride superlattice layer.

[0011] A further solution is that the unintentionally doped layer is located between the carbon-doped superlattice layer and the carbon-doped gallium nitride layer.

[0012] In a further embodiment, the number of carbon-doped superlattice layers is at least two, the unintentionally doped layer is located between two adjacent carbon-doped superlattice layers, and the carbon-doped gallium nitride layer is located above the uppermost carbon-doped superlattice layer.

[0013] A preferred solution is that the unintentionally doped layer is an unintentionally doped gallium nitride layer, an unintentionally doped aluminum gallium nitride layer, an unintentionally doped gallium nitride superlattice layer, an unintentionally doped aluminum gallium nitride superlattice layer or an unintentionally doped aluminum nitride superlattice layer.

[0014] A preferred solution is that the carbon concentration of the unintentionally doped layer is less than 5E18 atoms / cm 3 The carbon concentration of the carbon-doped high-resistance layer is greater than 5E18 atoms / cm 3 .

[0015] In a preferred embodiment, the extrinsic dopant is one or more of propane, methane, and ethylene. The growth conditions for the carbon-doped high-resistance layer using the external doping method are as follows: substrate surface temperature of 1000°C, growth pressure of 50 mbar, and V / III ratio of 1890. The growth conditions for the unintentionally doped layer using the external doping method are as follows: substrate surface temperature of 1050°C, growth pressure of 200 mbar, and V / III ratio of 400.

[0016] To achieve the above-mentioned second objective, the present invention provides a gallium nitride semiconductor device, a substrate, and a buffer layer, a carbon-doped layer, a channel layer, and a barrier layer sequentially formed on the substrate; the carbon-doped layer is manufactured according to the above-mentioned method for preparing a gallium nitride semiconductor device.

[0017] The beneficial effects of the present invention are that the carbon-doped layer is grown using an external doping method at a higher temperature, higher V / III ratio, and higher pressure than those under intrinsic growth conditions, thereby achieving high crystal quality and suppressing the inherent intrinsic doping effect. By suppressing the intrinsic doping effect, the uniformity of carbon incorporation can be improved. The resulting suppressed carbon-doped layer has better carbon incorporation uniformity and device breakdown uniformity. Furthermore, the carbon-doped layer is located in the center of the epitaxial-integrated structure, resulting in high resistivity and high breakdown voltage. The carbon-doped superlattice structure can enhance the high-resistance characteristics of gallium nitride semiconductor devices while ensuring crystal quality. The unintentionally doped layer is a low-carbon doped layer with higher crystal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. 1 is a schematic structural diagram of a gallium nitride semiconductor device according to a first embodiment of the present invention.

[0019] Figure 2 This is a comparison chart of carbon concentration curves inside the first embodiment of the gallium nitride semiconductor device of the present invention at different flow rates of extrinsic dopants and carbon concentration curves inside gallium nitride semiconductor devices obtained by existing intrinsic methods.

[0020] Figure 3 1 is a comparison diagram of the vertical breakdown voltage curve of the first embodiment of the gallium nitride semiconductor device of the present invention and the vertical breakdown voltage curve of the existing gallium nitride semiconductor device obtained by the intrinsic method.

[0021] Figure 4 FIG. 1 is a schematic structural diagram of a second embodiment of a gallium nitride semiconductor device according to the present invention.

[0022] Figure 5 FIG. 1 is a schematic structural diagram of a gallium nitride semiconductor device according to a third embodiment of the present invention.

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0024] Gallium nitride semiconductor device and its manufacturing method, first embodiment

[0025] See also Figure 1The gallium nitride semiconductor device includes a substrate 11, a buffer layer 12, a carbon-doped layer 13, a channel layer 14, a barrier layer 15, and a cap layer 16 sequentially formed on the substrate 11. The carbon-doped layer 13 is located between the buffer layer 12 and the channel layer 14. The substrate 11 is made of sapphire, glass, or silicon carbide. The buffer layer 12 is made of aluminum nitride or aluminum gallium nitride. The channel layer 14 is an unintentionally doped gallium nitride layer. The barrier layer 15 is made of aluminum gallium nitride.

[0026] The carbon-doped layer 13 includes a carbon-doped high-resistance layer 131 and an unintentionally doped layer 132. The carbon concentration of the carbon-doped high-resistance layer 131 is greater than that of the unintentionally doped layer 132, and the carbon concentration of the carbon-doped high-resistance layer 131 is greater than 5E18 atoms / cm 3 The carbon concentration of the unintentionally doped layer 132 is less than 5E18 atoms / cm 3 .

[0027] The carbon-doped high-resistance layer 131 includes a carbon-doped superlattice layer 1311 and a carbon-doped gallium nitride layer 1312. The unintentionally doped layer 132 is located between the buffer layer 12 and the carbon-doped superlattice layer 1311. The carbon-doped superlattice layer 1311 is a carbon-doped gallium nitride superlattice layer, a carbon-doped aluminum gallium nitrogen superlattice layer, or a carbon-doped aluminum nitride superlattice layer.

[0028] The unintentionally doped layer 132 is an unintentionally doped gallium nitride layer, an unintentionally doped aluminum gallium nitride layer, an unintentionally doped gallium nitride superlattice layer, an unintentionally doped aluminum gallium nitride superlattice layer, or an unintentionally doped aluminum nitride superlattice layer.

[0029] The method for fabricating a gallium nitride semiconductor device includes forming a carbon-doped high-resistance layer 131 and an unintentionally doped layer 132 using an external carbon doping method using an extrinsic dopant. The extrinsic dopant is one or more of propane, methane, and ethylene. Growth conditions for the external carbon doping method are: a substrate 11 surface temperature greater than or equal to 900°C, a growth pressure greater than or equal to 50 mbar, and a V / III ratio greater than or equal to 200. The carbon doping concentration can be controlled by controlling the flow rate of the intrinsic dopant.

[0030] In this embodiment, the carbon-doped high-resistance layer 131 is formed using the external doping method under the following growth conditions: substrate 11 surface temperature of 1000°C, growth pressure of 50 mbar, and V / III ratio of 1890. The unintentionally doped layer 132 is formed using the external doping method under the following growth conditions: substrate 11 surface temperature of 1050°C, growth pressure of 200 mbar, and V / III ratio of 400.

[0031] Figure 2 The graph is a comparison of carbon concentration curves inside the gallium nitride semiconductor device of the present invention under different flow rates of extrinsic dopants and a carbon concentration curve inside the gallium nitride semiconductor device obtained by an existing intrinsic method. Figure 3The vertical breakdown voltage curve of the gallium nitride semiconductor device of the present invention is compared with the vertical breakdown voltage curve of the gallium nitride semiconductor device obtained by the existing intrinsic method.

[0032] Depend on Figure 2 and Figure 3 It can be seen that the carbon bonding uniformity and device breakdown uniformity of the gallium nitride semiconductor device obtained by the external doping method are significantly better than those of the existing gallium nitride semiconductor device obtained by the intrinsic method.

[0033] As can be seen above, the carbon-doped layer is grown using an external doping method, at a higher temperature, higher V / III ratio, and higher pressure than those under intrinsic growth conditions, to achieve high crystal quality and suppress the intrinsic doping effect. This suppressed carbon-doped layer exhibits improved carbon bonding uniformity and device breakdown uniformity. Furthermore, the carbon-doped layer is located in the center of the epitaxial-pi structure, resulting in high resistivity and high breakdown voltage. The carbon-doped superlattice structure enhances the high-resistance characteristics of gallium nitride semiconductor devices while ensuring crystal quality. The unintentionally doped layer is a low-carbon doped layer with high crystal quality.

[0034] Gallium nitride semiconductor device and its manufacturing method, second embodiment

[0035] As an explanation of the second embodiment of the gallium nitride semiconductor device and the method for manufacturing the same according to the present invention, only the differences from the first embodiment of the gallium nitride semiconductor device and the method for manufacturing the same are described below.

[0036] See also Figure 4 In this embodiment, the unintentionally doped layer 232 is located within the carbon-doped high-resistance layer 231 and between the carbon-doped superlattice layer 2311 and the carbon-doped gallium nitride layer 2312 .

[0037] Gallium nitride semiconductor device and its manufacturing method, third embodiment

[0038] As an explanation of the third embodiment of the gallium nitride semiconductor device and the method for manufacturing the same according to the present invention, only the differences from the third embodiment of the gallium nitride semiconductor device and the method for manufacturing the same described above are described below.

[0039] See also Figure 5 In this embodiment, the number of carbon-doped superlattice layers 3311 is at least two, the unintentionally doped layer 332 is located between two adjacent carbon-doped superlattice layers 3311, and the carbon-doped gallium nitride layer 3312 is located above the topmost carbon-doped superlattice layer 3311.

[0040] In addition, the number of carbon-doped high-resistance layers and unintentionally doped layers can also be more than two, and multiple carbon-doped high-resistance layers and multiple unintentionally doped layers can be grown alternately. The above changes can also achieve the purpose of the present invention.

[0041] Finally, it should be emphasized that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a gallium nitride semiconductor device, characterized in that: include: forming a carbon-doped layer between the buffer layer and the channel layer by an external carbon doping method using a non-intrinsic dopant; The growth conditions of the external carbon doping method are: substrate surface temperature greater than or equal to 900° C., growth pressure greater than or equal to 50 mbar, and V / III ratio greater than or equal to 200; The carbon-doped layer includes a carbon-doped high-resistance layer and an unintentional doping layer, wherein the carbon concentration of the carbon-doped high-resistance layer is greater than the carbon concentration of the unintentional doping layer; The unintentional doping layer is located between the buffer layer and the carbon-doped high-resistance layer, or the unintentional doping layer is located within the carbon-doped high-resistance layer; The extrinsic dopant is one or more of propane, methane and ethylene; The growth conditions of the external doping method used to form the carbon-doped high-resistance layer are as follows: substrate surface temperature is 1000° C., growth pressure is 50 mbar, and V / III ratio is 1890; The growth conditions of the external doping method used to form the unintentionally doped layer are as follows: substrate surface temperature of 1050° C., growth pressure of 200 mbar, V / III ratio of 400; The carbon-doped high-resistance layer includes a carbon-doped superlattice layer and a carbon-doped gallium nitride layer, wherein the carbon-doped superlattice layer is a carbon-doped gallium nitride superlattice layer, a carbon-doped aluminum gallium nitrogen superlattice layer or a carbon-doped aluminum nitride superlattice layer; The carbon concentration of the unintentionally doped layer is less than 5E18 atoms / cm 3 The carbon concentration of the carbon-doped high-resistance layer is greater than 5E18 atoms / cm 3 .

2. The method for preparing a gallium nitride semiconductor device according to claim 1, wherein: The unintentionally doped layer is located between the carbon-doped superlattice layer and the carbon-doped gallium nitride layer.

3. The method for preparing a gallium nitride semiconductor device according to claim 1, wherein: The number of the carbon-doped superlattice layers is at least two, the unintentionally doped layer is located between two adjacent carbon-doped superlattice layers, and the carbon-doped gallium nitride layer is located above the uppermost carbon-doped superlattice layer.

4. The method for preparing a gallium nitride semiconductor device according to any one of claims 1 to 3, wherein: The unintentionally doped layer is an unintentionally doped gallium nitride layer, an unintentionally doped aluminum gallium nitride layer, an unintentionally doped gallium nitride superlattice layer, an unintentionally doped aluminum gallium nitride superlattice layer or an unintentionally doped aluminum nitride superlattice layer.

5. A gallium nitride semiconductor device, characterized in that The method comprises a substrate and a buffer layer, a carbon doping layer, a channel layer and a barrier layer sequentially formed on the substrate; The carbon-doped layer is manufactured by the method for manufacturing a gallium nitride semiconductor device according to any one of claims 1 to 4.

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