P-type heat treatment method of gold-doped tellurium-cadmium-mercury material

Abstract

The invention belongs to the technical field of semiconductor material processing and preparation, and particularly provides a P-type heat treatment method of a gold-doped tellurium-cadmium-mercury material, and the method comprises the following steps: S1, preparing a gold-doped tellurium-cadmium-mercury epitaxial material, and carrying out the first heat treatment; s2, growing a protective layer on the surface of the gold-doped tellurium-cadmium-mercury epitaxial material; and S3, carrying out second heat treatment on the gold-doped tellurium-cadmium-mercury epitaxial material on which the protective layer grows in a protective gas atmosphere or in vacuum. According to the P-type heat treatment method provided by the invention, two annealing processes of tellurium mercury source heat treatment and wide band gap coverage vacuum heat treatment are carried out on the gold-doped tellurium cadmium mercury material obtained by epitaxial growth, so that the phenomenon that gold-doped elements migrate and diffuse to a substrate area along with full filling of mercury vacancies when mercury-rich annealing is adopted is effectively avoided; and meanwhile, the second-step vacuum heat treatment can improve the distribution uniformity of gold-doped elements, avoid the phenomenon of an inversion layer or a sandwich layer, obviously improve the phenomenon of interface enrichment and improve the electrical property stability of the gold-doped tellurium-cadmium-mercury epitaxial annealing.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor material processing and preparation, and in particular relates to a P-type heat treatment method for a gold-doped mercury cadmium telluride material. Background Art

[0002] Liquid phase epitaxial growth is the mainstream preparation technology for HgCdTe epitaxial thin films due to its low growth difficulty and good crystal quality. The light absorption layer of the traditional n-on-p type HgCdTe infrared focal plane detector uses HgCdTe material doped with p-type Hg vacancies. Using Au doped atoms to occupy the mercury vacancies in the HgCdTe P-type material can help reduce the mercury vacancy concentration in the HgCdTe P-type material, reduce the density of deep energy level recombination centers, increase the minority carrier lifetime, and reduce the dark current of the device. It is an effective method to improve the overall performance of the device.

[0003] When HgCdTe materials are prepared by tellurium-rich liquid phase epitaxy, the conductivity type of the native HgCdTe thin film material is strong P-type (P-type carrier concentration ≥ 1×10 17 cm -3 ), and cannot be directly applied to the preparation of HgCdTe n-on-p type photovoltaic devices. Therefore, the electrical properties of HgCdTe epitaxial thin film materials usually need to be processed by heat treatment process to adjust the carrier concentration in HgCdTe materials to a suitable level and obtain a P-type carrier concentration of (0.2-2)×10 16 cm -3 Epitaxial thin film materials are used to meet the requirements for preparing HgCdTe n-on-p photovoltaic devices. However, the rapid diffusion of Au doping atoms in HgCdTe materials makes it very easy for gold doping elements to migrate and diffuse to the substrate area as the mercury vacancies are filled. At the same time, inappropriate annealing processes can easily cause Au element enrichment and inhomogeneity problems, which greatly increases the difficulty of replacing mercury vacancies with Au doping elements and effectively improving device performance.

[0004] In the prior art, the P-type heat treatment methods of HgCdTe materials mainly include mercury-rich heat treatment and mercury telluride powder source heat treatment methods. Due to the high mercury partial pressure in mercury-rich heat treatment, gold doping elements are very easy to migrate and diffuse to the substrate area as the mercury vacancies are filled. A short period of annealing will greatly reduce the residual gold concentration in the epitaxy, which is difficult to control. Although the mercury partial pressure of mercury telluride powder source heat treatment is lower than that of mercury-rich heat treatment, gold elements are easily enriched at the interface between the epitaxy and the substrate, resulting in uneven distribution of gold elements, causing unstable electrical properties, and its mercury vacancy filling ability is weak, which cannot achieve the purpose of improving the performance of HgCdTe devices. Therefore, a reasonable annealing method is the key to obtaining HgCdTe epitaxy with uniform distribution of Au atoms and effectively improving the performance of materials and devices. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem of poor distribution uniformity in the existing mercury-rich annealing technology, in which the doping elements migrate and diffuse to the substrate region as the mercury vacancies are fully filled.

[0006] To this end, the present invention provides a P-type heat treatment method for a gold-doped mercury cadmium telluride material, comprising the following steps:

[0007] S1, preparing gold-doped mercury cadmium telluride epitaxial material and performing the first heat treatment;

[0008] S2, growing a protective layer on the surface of the gold-doped mercury cadmium telluride epitaxial material;

[0009] S3. Under a protective gas atmosphere or vacuum, a second heat treatment is performed on the gold-doped mercury cadmium telluride epitaxial material grown with a protective layer.

[0010] Specifically, the temperature of the first heat treatment in the above step S1 is 200-250° C., and the treatment time is 24-60 hours.

[0011] Specifically, the first heat treatment in the above step S1 further includes adding mercury telluride powder to provide mercury pressure, and 0.2-0.5 g of mercury telluride powder is added per cubic centimeter of epitaxial annealing space.

[0012] Specifically, the first heat treatment in the above step S1 further includes adding a pure mercury source, with 0.01-0.05 g of mercury added per cubic centimeter of epitaxial annealing space.

[0013] Specifically, the protective layer in the above step S2 is a zinc sulfide protective layer.

[0014] Specifically, the thickness of the protective layer in the above step S2 is

[0015] Specifically, the protective gas in the above step S3 is hydrogen.

[0016] Specifically, in the above step S3, the second heat treatment temperature is 200-250° C., and the treatment time is 5-30 hours.

[0017] Specifically, the carrier concentration of the gold-doped HgCdTe material after the secondary heat treatment is controlled to be (0.2-2)×10 16 cm -3 .

[0018] Specifically, the tooling used in the above heat treatment is a graphite tooling.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] The P-type heat treatment method for mercury cadmium telluride material provided by the present invention performs a two-step annealing process on the gold-doped mercury cadmium telluride material obtained by epitaxial growth, effectively avoiding the phenomenon that the gold doping element migrates and diffuses to the substrate area as the mercury vacancies are fully filled when mercury-rich annealing is adopted. At the same time, the second step of heat treatment under vacuum or protective gas can improve the uniformity of the distribution of the gold doping element, avoid the inversion layer or sandwich layer phenomenon, and the interface enrichment phenomenon is also significantly improved, thereby improving the electrical performance stability of the gold-doped mercury cadmium telluride after epitaxial annealing.

[0021] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the distribution of gold element in the unannealed gold-doped HgCdTe material native sheet.

[0023] Figure 2 This is the distribution of gold elements in the gold-doped mercury cadmium telluride material using the mercury telluride powder source annealing process in Comparative Example 1.

[0024] Figure 3 This is the distribution of gold elements in the gold-doped mercury cadmium telluride material using the mercury-rich annealing process in Comparative Example 2.

[0025] Figure 4 This is the distribution of gold elements in the gold-doped mercury cadmium telluride material using the P-type heat treatment method provided by the present invention in Example 1.

[0026] Figure 5 This is the distribution of gold elements in the gold-doped mercury cadmium telluride material using the P-type heat treatment method provided by the present invention in Example 2.

[0027] Figure 6 This is the distribution of gold elements in the gold-doped mercury cadmium telluride material using the P-type heat treatment method provided by the present invention in Example 3. DETAILED DESCRIPTION

[0028] The technical scheme in the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Although the representative embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be limited by the attached claims and their equivalents.

[0029] The present invention provides a P-type heat treatment method for a gold-doped mercury cadmium telluride material, comprising the following steps:

[0030] S1. Prepare gold-doped mercury cadmium telluride epitaxial material by liquid phase epitaxial growth process, and perform the first heat treatment. The tooling used for heat treatment is preferably a graphite tooling with certain airtightness, the heat treatment temperature is 200-250°C, the heat treatment time is 24-60h, and mercury telluride powder is added to provide mercury pressure, and 0.2-0.5g mercury telluride powder is added per cubic centimeter of annealing space.

[0031] Preferably, 0.01-0.05 g of pure mercury can be added per cubic centimeter of annealing space to lower the vacancy concentration of the material and optimize the material performance.

[0032] S2. growing a protective layer on the surface of the gold-doped mercury cadmium telluride epitaxial material.

[0033] High-temperature annealing can make the gold element evenly distributed, but at the same time the mercury atoms in the epitaxy will also run out, causing the vacancy concentration of the material to increase and affecting the performance. Therefore, it is necessary to grow a protective layer as a cover layer for passive annealing to prevent mercury atoms from diffusing out of the epitaxy during high-temperature annealing.

[0034] The protective layer is preferably a zinc sulfide protective layer, and the thickness of the protective layer is preferably

[0035] S3. In a protective gas atmosphere or vacuum, the gold-doped HgCdTe epitaxial material with a protective layer is subjected to a second heat treatment. The protective gas is preferably hydrogen. The tooling used for the heat treatment is preferably a graphite tooling with a certain degree of airtightness. The heat treatment temperature is 200-250°C and the treatment time is 5-30h. After the two-step annealing, the carrier concentration of the gold-doped HgCdTe film is controlled to be (0.2-2)×10 16 cm -3 .

[0036] The effect of the P-type heat treatment method of the gold-doped mercury cadmium telluride material of the present invention is studied below through specific examples.

[0037] Embodiment 1:

[0038] This embodiment provides a P-type heat treatment method for a gold-doped mercury cadmium telluride material, comprising the following steps:

[0039] S1. Prepare gold-doped HgCdTe epitaxial material by liquid phase epitaxial growth process, and detect the distribution of gold element in the gold-doped HgCdTe epitaxial material, such as Figure 1 shown.

[0040] Place the gold-doped HgCdTe epitaxial material in a well-sealed container with a space of about 100 cm 3 50 g of mercury telluride powder and 2 g of pure mercury were added to the graphite tooling, and the first heat treatment was carried out at 220 ° C for 48 h.

[0041] S2. Grow a zinc sulfide protective layer on the surface of the gold-doped mercury cadmium telluride epitaxial material with a thickness of

[0042] S3. In a hydrogen atmosphere, the gold-doped HgCdTe epitaxial material with a zinc sulfide protective layer is subjected to a second heat treatment to make the gold element evenly distributed. The heat treatment temperature is 220° C. and the treatment time is 20 hours.

[0043] The distribution of gold elements in the gold-doped HgCdTe material after heat treatment is as follows: Figure 4 As shown, the electrical properties were tested at 77K, and the results are shown in Table 1.

[0044] Embodiment 2:

[0045] This embodiment provides a P-type heat treatment method for a gold-doped mercury cadmium telluride material, comprising the following steps:

[0046] S1. Prepare gold-doped HgCdTe epitaxial material by liquid phase epitaxial growth process, and detect the distribution of gold element in the gold-doped HgCdTe epitaxial material, such as Figure 1 shown.

[0047] Place the gold-doped HgCdTe epitaxial material in a well-sealed space of about 100 cm 3 20 g of mercury telluride powder was added to the graphite tooling and the first heat treatment was carried out at 200 °C for 60 h.

[0048] S2. Grow a zinc sulfide protective layer on the surface of the gold-doped mercury cadmium telluride epitaxial material with a thickness of

[0049] S3. In a hydrogen atmosphere, the gold-doped HgCdTe epitaxial material with a zinc sulfide protective layer is subjected to a second heat treatment to make the gold element evenly distributed. The heat treatment temperature is 200° C. and the treatment time is 30 hours.

[0050] The distribution of gold elements in the gold-doped HgCdTe material after heat treatment is as follows: Figure 5 As shown, the electrical properties were tested at 77K, and the results are shown in Table 1.

[0051] Embodiment 3:

[0052] This embodiment provides a P-type heat treatment method for gold-doped mercury cadmium telluride material, comprising the following steps:

[0053] S1. Prepare gold-doped HgCdTe epitaxial material by liquid phase epitaxial growth process, and detect the distribution of gold element in the gold-doped HgCdTe epitaxial material, such as Figure 1 shown.

[0054] Place the gold-doped HgCdTe epitaxial material in a well-sealed container with a space of about 100 cm3 35 g of mercury telluride powder and 5 g of pure mercury were added to the graphite tooling, and the first heat treatment was carried out at 250 ° C for 24 h.

[0055] S2. Grow a zinc sulfide protective layer on the surface of the gold-doped mercury cadmium telluride epitaxial material with a thickness of

[0056] S3. In a hydrogen atmosphere, the gold-doped HgCdTe epitaxial material with a zinc sulfide protective layer is subjected to a second heat treatment to make the gold element evenly distributed. The heat treatment temperature is 250° C. and the treatment time is 10 hours.

[0057] The distribution of gold elements in the gold-doped HgCdTe material after heat treatment is as follows: Figure 6 As shown, the electrical properties were tested at 77K, and the results are shown in Table 1.

[0058] Comparative Example 1:

[0059] This comparative example provides a method for heat treating a mercury telluride powder source of a gold-doped mercury cadmium telluride material, comprising the following steps:

[0060] The gold-doped HgCdTe epitaxial material was prepared by using Example 1. The gold-doped HgCdTe epitaxial material was placed in a well-sealed container with a space of about 100 cm. 3 50 g of mercury telluride powder was added to a graphite tool and heat treated at 220 ° C for 48 h.

[0061] The distribution of gold elements in the gold-doped HgCdTe material after heat treatment is as follows: Figure 2 As shown, the electrical properties were tested at 77K, and the results are shown in Table 1.

[0062] Comparative Example 2:

[0063] This comparative example provides a mercury-rich heat treatment method for a gold-doped mercury cadmium telluride material, comprising the following steps:

[0064] The gold-doped mercury cadmium telluride epitaxial material was prepared by using Example 1. The gold-doped mercury cadmium telluride epitaxial material was placed in a vacuum quartz tube for closed-tube heat treatment, and 1 g of mercury was added. The heat treatment temperature was 250° C. and the heat treatment time was 20 h.

[0065] The distribution of gold elements in the gold-doped HgCdTe material after heat treatment is as follows: Figure 3 As shown, the electrical properties were tested at 77K, and the results are shown in Table 1.

[0066] Table 1 Electrical properties of Au-doped HgCdTe materials at 77K

[0067] <![CDATA[Carrier concentration cm -3 > <![CDATA[Mobility cm 2 ·v -1 ·s -1 > Example 1 1.071E+16 4.416E+02 Example 2 1.614E+16 3.982E+02 Example 3 1.416E+16 4.025E+02 Comparative Example 1 1.582E+16 4.057E+02 Comparative Example 2 6.167E+15 4.501E+02

[0068] As shown in Table 1, by using the heat treatment method of the present invention, the carrier concentration of HgCdTe material is controlled at (0.2-2)×10 16 cm -3 , meeting the device's electrical performance requirements for the P-type absorption layer. In comparison, among the three embodiments, the annealing treatment condition of the mercury telluride powder in Example 1 with 2g of mercury has a lower carrier concentration, indicating that there are fewer deep energy level defects of mercury vacancies in the material, which is beneficial to the control of the body leakage current of the mercury cadmium telluride device material. Although the mercury-rich annealing in Comparative Example 2 can reduce the vacancy concentration to a lower level, Figure 1-6 It can be seen that after the mercury-rich annealing process of the unannealed gold-doped HgCdTe primary wafer, the gold doping element migrates and diffuses to the substrate area as the mercury vacancies are filled, and the gold doping concentration in the epitaxy increases from 10 16 Dropped below 10 15 cm -3 Powder annealing significantly deteriorates the distribution uniformity of Au elements in the epitaxy, and serious enrichment occurs at the interface between the epitaxy and the substrate. By adopting the secondary annealing process of the present invention, the uniformity of Au elements in the HgCdTe epitaxy is significantly improved, and the interface enrichment phenomenon is also significantly improved.

[0069] In summary, the P-type heat treatment method of the mercury cadmium telluride material provided by the present invention performs a two-step annealing process of mercury telluride source heat treatment and wide bandgap coverage vacuum heat treatment on the gold-doped mercury cadmium telluride material obtained by epitaxial growth, which effectively avoids the phenomenon that the gold doping elements migrate and diffuse to the substrate area as the mercury vacancies are fully filled when mercury-rich annealing is adopted. At the same time, the second step of vacuum heat treatment can improve the uniformity of the distribution of the gold doping elements, avoid the inversion layer or sandwich layer phenomenon, and the interface enrichment phenomenon is also significantly improved, thereby improving the electrical performance stability of the gold-doped mercury cadmium telluride after epitaxial annealing.

[0070] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A P-type heat treatment method for gold-doped mercury cadmium telluride material, characterized in that: The following steps are involved: S1, preparing gold-doped mercury cadmium telluride epitaxial material and performing the first heat treatment; S2, growing a protective layer on the surface of the gold-doped mercury cadmium telluride epitaxial material; S3. Under a protective gas atmosphere or vacuum, a second heat treatment is performed on the gold-doped mercury cadmium telluride epitaxial material grown with a protective layer.

2. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: The temperature of the first heat treatment in step S1 is 200-250° C., and the treatment time is 24-60 hours.

3. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: The first heat treatment in step S1 further includes adding mercury telluride powder to provide mercury pressure, and 0.2-0.5 g of mercury telluride powder is added per cubic centimeter of annealing space.

4. The P-type heat treatment method of gold-doped HgCdTe material according to claim 3, characterized in that: The first heat treatment in step S1 also includes adding a pure mercury source, with 0.01-0.05 g of mercury added per cubic centimeter of annealing space.

5. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: The protective layer in step S2 is a zinc sulfide protective layer.

6. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: The thickness of the protective layer in step S2 is 7. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: In step S3, the protective gas is hydrogen.

8. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: The second heat treatment temperature in step S3 is 200-250° C., and the treatment time is 5-30 hours.

9. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: After two heat treatments, the carrier concentration of gold-doped HgCdTe material is controlled at (0.2-2)×10 16 cm -3 .

10. The P-type heat treatment method of gold-doped HgCdTe material according to claim 1, characterized in that: The tooling used for heat treatment is graphite tooling.

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