Hydride vapor phase epitaxial growth method for improving characteristics of semi-insulating gallium nitride through iron-carbon co-doping

Abstract

The invention belongs to the field of semiconductor crystal growth, and relates to a hydride vapor phase epitaxial growth method for improving the characteristics of semi-insulating gallium nitride through iron-carbon co-doping. According to the method, metal Ga and Fe dopants are placed in a container (boat) of a source region, nitrogen, hydrogen chloride gas, ammonia gas and methane are adopted, and the semi-insulating gallium nitride crystal grows and is obtained through flow and temperature regulation and control. Through Fe-C co-doping, the high quality of the gallium nitride crystal is maintained, and the semi-insulating gallium nitride with high resistivity and better stability is obtained. The longitudinal resistance distribution of the obtained semi-insulating silicon carbide crystal is uniform, and the longitudinal semi-insulating characteristic of semi-insulating gallium nitride can be improved, so that the more uniform and more stable semi-insulating gallium nitride crystal is realized.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor crystal growth, and in particular relates to a hydride vapor phase epitaxial growth method for improving the properties of semi-insulating gallium nitride by iron-carbon co-doping. Background Art

[0002] Gallium nitride (GaN), as a third-generation semiconductor material, has the characteristics of large bandgap, strong radiation resistance, high breakdown electric field strength, and high temperature resistance. It has great advantages in the field of high-voltage and high-frequency electronic devices and can enable equipment to work normally under extreme conditions.

[0003] Compared with heteroepitaxial substrates, GaN substrates are the ideal substrate for most GaN-based devices. However, as the devices are facing more and more complex usage situations, the challenges faced by devices made from traditional GaN crystals are also increasing. This is mainly because the resistance of conventional GaN crystals is generally low, which makes their application in high-frequency and high-power devices more limited.

[0004] Semi-insulating semiconductor materials usually include high-purity semi-insulating materials, precisely compensated semi-insulating materials, and amphoteric impurity deep energy level compensated semiconductor materials. In order to adjust the electrical properties of gallium nitride (GaN) crystals, doping technology is widely used. Among the current growth technologies, hydride vapor phase epitaxy (HVPE) is the main method for growing large-sized gallium nitride crystals. This method can provide high-quality gallium nitride crystals to meet the needs of high-performance electronic devices. However, the selection of a suitable doping source is crucial for the HVPE method to grow semi-insulating gallium nitride. Iron doping can produce gallium nitride with high resistivity and is a common doping source for preparing semi-insulating gallium nitride. It is a solid powder material used with a reactor. By controlling the doping amount of Fe, the electrical properties of gallium nitride can be effectively adjusted. However, the doping of Fe is not easy to control during crystal growth. Fe doping has a memory effect, and Fe atoms tend to segregate to the outermost surface layer, which may cause Fe-doped semi-insulating gallium nitride crystals to face the problem of uneven doping. This unevenness can have a negative impact on the performance and reliability of gallium nitride crystals. Summary of the invention

[0005] To solve the existing problems, the present invention provides a hydride vapor phase epitaxial growth method for improving the properties of semi-insulating gallium nitride by iron-carbon co-doping. The purpose of the present invention is to overcome the problems of poor quality, low resistivity and high lifetime of photogenerated carriers of semi-insulating gallium nitride prepared by the existing method.

[0006] A hydride vapor phase epitaxial growth method for improving the properties of semi-insulating gallium nitride by iron-carbon co-doping comprises the following steps: (1) Place a GaN substrate (MOCVD-GaN) prepared by metal organic vapor deposition on a seed crystal holder in the growth region as a seed crystal; place both metal Ga and Fe dopants in a container (boat) in the source region; (2) Nitrogen and ammonia are introduced separately, with nitrogen as the carrier gas, and the temperature of the source area and the growth area are raised by the heater respectively. The pressure is kept at normal pressure for 10-30 minutes to nitride the surface of the seed crystal; (3) Keep ammonia and nitrogen flowing to raise the temperature of the growth zone for a second time; (4) Keep ammonia and nitrogen flowing, and simultaneously introduce HCl gas and carbon (C) dopant gas source into the source region. The metal Ga in the source region reacts with HCl to generate GaCl, and the metal Fe in the source region reacts with HCl to generate FeCl2. Nitrogen is used as a carrier gas to transport GaCl, NH3, FeCl2 and C doping gas source to the growth region, and crystal growth obtains semi-insulating gallium nitride crystals.

[0007] Preferably, the container of the source region in step (1) is a quartz or Al2O3 crucible.

[0008] Preferably, the Fe dopant in step (1) may be ferrocene (C 10 H 10 Fe) or Fe2O3 powder or iron powder.

[0009] Preferably, in step (2), the temperatures of the source region and the growth region are controlled at 860-900° C. and 950-1000° C., respectively.

[0010] Preferably, in step (2), the flow rate of ammonia is controlled at 950-1500 mL·min -1 ; The nitrogen flow rate is controlled at 500-1000 mL·min -1 .

[0011] Preferably, in step (3), the growth zone is heated a second time to 1020-1100°C.

[0012] Preferably, the flow rate of HCl gas to metal Ga in step (4) is controlled at 50-100 mL·min -1 ; The flow rate of HCl gas to the metal Fe dopant is controlled at 1-10 mL·min -1 ; Flow rate control of carbon doping gas source 5-50 mL·min -1 .

[0013] Preferably, the crystal growth time in step (4) is 5-10 hours.

[0014] Preferably, in step (4), the C doping gas source is CH4 mixed with nitrogen, with a volume concentration of 2%-7%.

[0015] The present invention relates to a gallium nitride crystal growth method, which achieves the growth of a high-quality gallium nitride epitaxial layer by accurately controlling the flow rate and reaction conditions of various gases. Specifically, the present invention uses four gases, namely nitrogen, hydrogen chloride gas, ammonia and methane, each of which is finely regulated by a flow controller equipped with an inlet pipe to ensure the stable supply of gas and the accuracy of the proportion during the reaction. In the source area, metal gallium is placed in a gallium boat and heated to a high temperature of 860-900°C. At this time, hydrogen chloride gas is introduced through an inlet pipe and chemically reacts with liquid metal gallium to generate gaseous gallium chloride. Subsequently, the gaseous gallium chloride is transported to the growth area through the next section of the pipeline to provide raw materials for the deposition of gallium nitride.

[0016] In order to achieve Fe-C doping, the present invention introduces hydrogen chloride gas into a container containing metal Fe to react with the metal Fe to generate ferrous chloride (FeCl2). Then, the ferrous chloride is transported to the growth zone through a pipeline. At the same time, in order to achieve C doping, the present invention uses CH4 as a C source. CH4 enters the growth zone through a provided pipeline and participates in the deposition process of gallium nitride together with gaseous GaCl, NH3 and FeCl2. Methane decomposes at high temperature to produce carbon atoms, which can replace some nitrogen atoms or gallium atoms in the gallium nitride lattice, thereby achieving the regulation of the properties of gallium nitride.

[0017] In the growth zone, the temperature is controlled between 1020-1100℃, which provides a suitable crystallization temperature for the formation of gallium nitride. Within this temperature range, gaseous GaCl, NH3, FeCl2 and CH4 are mixed and chemically reacted at the seed crystal support position to generate gallium nitride and deposit on the surface of the seed crystal placed on the carrier for epitaxial growth. By precisely controlling the growth conditions and time, semi-insulating gallium nitride with excellent performance can be obtained.

[0018] The present invention has the following beneficial effects compared with the prior art: The present invention realizes the growth of semi-insulating gallium nitride crystals by Fe-C co-doping at appropriate temperature and gas flow rate. C doping will not have a particularly large impact on the quality of the prepared gallium nitride, and the high quality of the gallium nitride crystal can be maintained. By combining the doping characteristics of Fe and C, the negative impact of a single doping source can be resolved. Through the carrier capture effect of deep energy level defects, a semi-insulating gallium nitride with high resistivity and better stability is obtained. The longitudinal resistance distribution of the obtained semi-insulating silicon carbide crystal is uniform, which can improve the longitudinal semi-insulating characteristics of the semi-insulating gallium nitride, thereby achieving a more uniform and stable semi-insulating crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of a horizontal atmospheric pressure HVPE device with dual doping sources, where: 1 and 5 are hydrogen chloride gas (HCl), 2 is ammonia gas (NH3), 3 is nitrogen gas (N2), 4 is a carbon (C) dopant gas source, 6 is an iron (Fe) dopant source, 7 is metal gallium (Ga), 8 and 9 are heaters, 10 is a seed crystal holder, and 11 is a seed crystal; Figure 2 A diagram of a GaN crystal grown by the present invention; Figure 3 This is a high-resolution X-ray diffraction (XRD) comparison diagram of iron-doped and iron-carbon co-doped in the present invention; Figure 4 It is a comparison chart of the resistivity test results of the iron-only doping and the iron-carbon co-doping in the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with embodiments and drawings, but the protection scope of the present invention is not limited thereto.

[0021] The schematic diagram of the HVPE growth device for realizing Fe-C co-doping in the present invention is as follows: Figure 1 shown.

[0022] Embodiment 1: A hydride vapor phase epitaxial growth method for improving the properties of semi-insulating gallium nitride by iron-carbon co-doping (1) placing a 2-inch MOCVD-GaN substrate on a seed crystal holder 10 in a growth region as a seed crystal 11; placing metal Ga7 in a container in a source region, and placing iron powder (Fe)6 in a container in the source region; (2) Nitrogen 2 is introduced as a carrier gas, and ammonia 3 is introduced. The temperature of the source region and the growth region are controlled at 860°C and 1000°C respectively through heaters 8 and 9. The pressure is kept at normal pressure for 20 minutes to nitride the surface of the seed crystal. The flow rate of ammonia 3 is controlled at 1500 mL min -1 ; Nitrogen 2 flow rate was controlled at 1000 mL·min -1 ; (3) The temperature of the growth zone is raised to 1050° C. by heater 9 again; (4) HCl gas 1, 5 and CH4 (carbon-doped gas source 4) mixed with N2 at a concentration of 5% are introduced into the source region at the same time. Ammonia 2 is used as a carrier gas to transport the growth source to the growth region, and the crystal is grown to obtain a semi-insulating GaN crystal. The flow rate of HCl gas 1 to metal Ga7 is controlled at 70 mL min -1 ; The flow rate of HCl gas 5 to iron powder (Fe) 6 was controlled at 1 mL min -1 ; Flow rate control of carbon doping gas source 4: 15 mL·min -1 ; Growth time is 10 hours. Figure 2Semi-insulating gallium nitride crystal shown.

[0023] Embodiment 2: A hydride vapor phase epitaxial growth method for improving the properties of semi-insulating gallium nitride by iron-carbon co-doping (1) placing a 2-inch MOCVD-GaN substrate on a seed crystal holder 10 in a growth region as a seed crystal 11; placing metal Ga7 in a container in a source region, and placing iron powder (Fe)6 in a container in the source region; (2) Nitrogen 2 is introduced as a carrier gas, and ammonia 3 is introduced. The temperature of the source region and the growth region are controlled at 800°C and 950°C respectively through heaters 8 and 9. The pressure is kept at normal pressure for 10 minutes to nitride the surface of the seed crystal. The flow rate of ammonia 3 is controlled at 1000 mL min -1 ; Nitrogen 2 flow rate was controlled at 800 mL·min -1 ; (3) The temperature of the growth zone is raised to 1080° C. by heater 9 again; (4) HCl gas 1, 5 and CH4 (carbon-doped gas source 4) mixed with N2 at a concentration of 5% are introduced into the source region at the same time. Ammonia 2 is used as a carrier gas to transport the growth source to the growth region, and the crystal is grown to obtain a semi-insulating gallium nitride crystal; the flow rate of HCl gas 1 to metal Ga7 is controlled at 50 mL min -1 ; The flow rate of HCl gas 5 to iron powder (Fe) 6 was controlled at 5 mL·min -1 ; Flow rate control of carbon doping gas source 4 5 mL·min -1 ; The growth time is 10 hours, and semi-insulating gallium nitride crystals are obtained.

[0024] Comparative Example 1: Only the Fe dopant is introduced, and in step 4 of Example 1, the introduction of the carbon doping gas source is stopped, and the other steps are the same as in Example 1.

[0025] Experimental Example: High-resolution X-ray diffraction (XRD) was used to observe the gallium nitride crystals obtained in Example 1 and Comparative Example 1. The results are as follows: Figure 3 As shown, the half-peak width of Fe-doped only is 123 arc seconds (arcsec), and the half-peak width of Fe-C co-doped is 68 arc seconds (arcsec). The reduction of the half-peak width indicates that the crystal quality is improved. The resistivity distribution of the gallium nitride crystal obtained by testing Example 1 and Comparative Example 1 with a resistivity tester is shown in the following figure. Figure 4 As shown, the GaN crystal co-doped with Fe and C has more uniform doping and more uniform resistivity distribution.

[0026] In summary, Fe-C co-doping in HVPE-grown GaN crystals can effectively improve the crystal quality of semi-insulating GaN, the uniformity of doping, increase the resistivity, and reduce the lifetime of photogenerated carriers.

Claims

1. A method for hydride vapor phase epitaxial growth of semi-insulating gallium nitride by iron-carbon co-doping, characterized in that: The growth method mainly comprises the following steps: (1) Place a GaN substrate (MOCVD-GaN) prepared by metal organic vapor deposition on a seed crystal holder in the growth region as a seed crystal; place both metal Ga and Fe dopants in a container (boat) in the source region; (2) Nitrogen and ammonia are introduced separately, with nitrogen as the carrier gas, and the temperature of the source area and the growth area are raised by the heater respectively, and the pressure is kept at normal pressure for 10-30 minutes; (3) Keep ammonia and nitrogen flowing to raise the temperature of the growth zone for a second time; (4) Keep ammonia and nitrogen flowing, and simultaneously introduce HCl gas and carbon (C) dopant gas source into the source region. The metal Ga in the source region reacts with HCl to generate GaCl, and the metal Fe in the source region reacts with HCl to generate FeCl2. Nitrogen is used as a carrier gas to transport GaCl, NH3, FeCl2 and C doping gas source to the growth region, and crystal growth obtains semi-insulating gallium nitride crystals.

2. The growth method according to claim 1, characterized in that The container of the source region in step (1) is a quartz or Al2O3 crucible.

3. The growth method according to claim 1, characterized in that: The Fe dopant in step (4) may be ferrocene (C 10 H 10 Fe) or Fe2O3 powder or iron powder.

4. The growth method according to claim 1, characterized in that: In the step (2), the temperatures of the source region and the growth region are controlled at 860-900°C and 950-1000°C, respectively.

5. The growth method according to claim 1, characterized in that In step (2), the flow rate of ammonia is controlled at 950-1500 mL·min -1 ; The nitrogen flow rate is controlled at 500-1000 mL·min -1 .

6. The growth method according to claim 1, characterized in that: In the step (3), the growth zone is heated up a second time to 1020-1100°C.

7. The growth method according to claim 1, characterized in that In step (4), the flow rate of HCl gas to metal Ga is controlled at 50-100 mL min -1 ; The flow rate of HCl gas to the metal Fe dopant is controlled at 1-10 mL·min -1 ; Flow rate control of carbon doping gas source 5-50 mL·min -1 .

8. The growth method according to claim 1, characterized in that: The crystal growth time in step (4) is 5-10 hours.

9. The growth method according to claim 1, characterized in that: In step (4), the carbon doping gas source is CH4 mixed with nitrogen, with a volume concentration of 2%-7%.

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