A method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy

Abstract

The present invention discloses a method for preparing a silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy, the method comprising the following steps: placing a substrate in an MBE cavity, controlling the vacuum in the cavity to be lower than 1×10 ‑10 Torr, heat the substrate to 940‑960°C and keep it for 28‑32 min, then lower the substrate temperature to 550‑570°C, set the Ga source temperature to 680‑700°C, adjust the electron beam current of the silicon source to #imgabs0#, open the silicon source electron beam baffle and the Ga source baffle, and grow the absorption layer; after the epitaxy of the absorption layer is completed, the substrate temperature is increased by 80‑100°C, during which the silicon source electron beam current is kept unchanged, and after 900‑1100 s of growth, the growth is stopped, and the epitaxial wafer is sent into the buffer chamber to wait for the vacuum in the growth chamber to be lower than 1×10 ‑10 The present invention realizes the structure of the impurity barrier band by controlling the growth beam, growth temperature and growth mode of the barrier layer.

Description

Technical Field

[0001] The invention relates to the field of semiconductor material preparation, and in particular to a method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy. Background Art

[0002] Silicon-doped gallium very long-wave infrared blocking impurity band (BIB) is a typical non-intrinsic silicon-based semiconductor material, in which the absorption wavelength can reach 5-20μm. Its wavelength is an important technical means to achieve low-temperature target detection, and plays an important role in low-temperature infrared target detection and deep space exploration. Silicon-doped gallium BIB is the core of very long-wave infrared detection. The common preparation methods of BIB are:

[0003] Chemical vapor deposition (CVD). CVD is the mainstream method for realizing silicon-based very long wave infrared detectors at home and abroad. For example, through the chemical reaction of silane and triethylgallium, a highly doped blocking impurity band absorption layer and an intrinsic blocking layer are realized. However, the disadvantage of CVD is that it reacts at high temperatures, which will cause the doping atoms in the high concentration area to diffuse to the low concentration area, causing the device interface layer to become wider, introducing impurity defects, and thus increasing the dark current and noise of the device.

[0004] Molecular beam epitaxy (MBE). Through thermal evaporation of doped element beam source furnace and electron beam source evaporation of silicon, the substrate temperature is adjusted to finally obtain a wafer with a blocking impurity band. However, it is limited by the capacity of the silicon electron beam source furnace and the memory effect in the cavity. The blocking layer epitaxy has a high doping concentration, which makes the device unable to become a blocking impurity band structure but more like a photoconductive device structure.

[0005] Ion implantation method. Ion implantation is usually used to prepare planar impurity blocking bands. Ning Dai's research group used ion implantation to form a planar highly doped absorption layer. This method has the disadvantages of shallow vertical depth of the absorption layer and uneven vertical concentration distribution, which makes it impossible to improve quantum efficiency. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a method for preparing silicon-doped gallium very long wave infrared detection materials based on molecular beam epitaxy. Based on the molecular beam epitaxy technology, during epitaxial growth in the molecular beam epitaxy system, a pure silicon block (resistivity>10000Ω·cm) is used as the epitaxial silicon source material, and a gallium source (7N) is used as the doping source material. A 4-inch (100) high-resistance silicon substrate or a low-resistance silicon substrate with surface ion implantation is placed in the growth chamber. The current and voltage of the electron beam evaporation source and the temperature of the gallium evaporation source are regulated by interconnecting the crystal oscillator (QCM) and the electron impact emission spectroscopy (EIES), and finally a structure that blocks the impurity band is realized during the epitaxial process.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy comprises the following steps:

[0009] (1) Place the substrate into the MBE chamber and control the vacuum in the chamber to be less than 1×10 -10 Torr, heat the substrate to 940-960℃, keep it for 28-32min, then lower the substrate temperature to 550-570℃, set the Ga source temperature to 680-700℃, and adjust the electron beam current of the silicon source to

[0010] (2) Opening the silicon source electron beam baffle and the Ga source baffle to grow the absorption layer;

[0011] (3) After the epitaxy of the absorption layer is completed, the substrate temperature is raised by 80-100°C. During this period, the electron beam current of the silicon source is kept unchanged. After 900-1100 seconds of growth, the growth is stopped and the epitaxial wafer is sent to the buffer chamber to wait for the vacuum in the growth chamber to be lower than 1×10 -10 Torr, and then sent into the growth chamber for barrier layer growth.

[0012] Preferably, the resistivity of the substrate is 0.0005-0.001Ω·cm.

[0013] Preferably, the thickness of the absorption layer is 6-10 μm; more preferably, the thickness of the absorption layer is 8 μm.

[0014] Preferably, the barrier layer has a thickness of 4-6 μm; more preferably, the barrier layer has a thickness of 5 μm.

[0015] Preferably, in step (1), the substrate temperature is heated to 950°C and maintained for 30 minutes, then the substrate temperature is reduced to 560°C, and the Ga source temperature is set to 690°C.

[0016] Preferably, in step (2), the time for growing the absorption layer is 75000-85000 seconds.

[0017] Preferably, in step (3), the growth time of the material being fed into the growth chamber is 45000-55000 seconds.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention utilizes high-purity vacuum epitaxy to effectively reduce the concentration of compensating impurities. The vacuum is less than 1×10 -10 Torr, avoiding the deposition of residual gas in the chamber during the process of atoms evaporating from the source and depositing on the substrate, which helps to suppress the compensation impurity concentration.

[0020] The present invention utilizes a low-temperature BIB structure full epitaxy method. Compared with other epitaxy methods such as CVD, the diffusion coefficient of the corresponding Ga source is minimized at low temperatures, thereby avoiding gradient diffusion from high concentration to low concentration.

[0021] The present invention controls the different growth temperatures between the absorption layer and the barrier layer. In the epitaxial process, it helps the surface diffusion of atoms, improves the diffusion of silicon atoms deposited on the surface when the epitaxial intrinsic silicon substrate is increased, and improves the quality of the wafer. The sample is transferred into the buffer cavity to avoid the memory effect of the cavity, thereby realizing the intrinsic barrier layer.

[0022] The present invention determines the growth beam current when growing BIB by comparing the lattice quality under different growth beam currents. And at this growth rate, 4-inch single crystal silicon was obtained.

[0023] The present invention explores the optimal growth temperature within the scope of the present invention by precisely controlling the substrate temperature and the temperature of Ga, thereby ensuring that the doping concentration is uniform and meets the diffusion concentration of the blocking impurity band.

[0024] In order to avoid the influence of memory effect, the temperature of the present invention is increased by 100°C after the epitaxy of the absorption layer is completed. After 1000s of epitaxy, the epitaxial wafer is placed in a buffer chamber, and after waiting for the vacuum in the growth chamber to be restored, the growth is carried out according to the original substrate temperature to reduce the doping concentration in the intrinsic layer, thereby effectively suppressing the dark current of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a silicon-doped gallium barrier impurity band prepared by an MBE method embodiment of the present invention;

[0026] Figure 2 RHEED fringe imaging of the epitaxial surface before epitaxy;

[0027] Figure 3 This is a picture of a 4-inch (100) crystal wafer substrate;

[0028] Figure 4 This is the concentration distribution diagram of BIB prepared in Example 1, and the gray part is the interface area;

[0029] Figure 5 is the XRD half-peak width at different growth rates;

[0030] Figure 6 It is a CVD epitaxial Si doped P BIB structure. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0033] Example 1

[0034] Figure 1 The schematic diagram of the structure of the silicon-doped gallium blocking impurity band prepared in an embodiment of the present invention is a preparation method comprising the following steps:

[0035] Pure silicon block (resistivity> 10000Ω·cm) was used as epitaxial silicon source material, and gallium source (7N) was used as doping source material. A 4-inch molecular beam epitaxy device was used to perform epitaxy of the material structure. The vacuum in the MBE chamber was lower than 1×10 -10 Torr, the substrate temperature was heated to 950°C and maintained for 30 minutes, while the Ga source temperature was raised to 690°C. The silicon evaporation beam current was adjusted to The substrate temperature was lowered to 560°C. At this time, the Rheed (2×1) of the substrate was striped, indicating that the surface of the material was flat. The silicon electron beam baffle and the Ga source baffle were opened, and the 8μm absorption layer was grown for 80,000 seconds. After the absorption layer epitaxy was completed, the substrate temperature was increased by 100°C. During this period, the silicon electron beam source was kept unchanged. After 1000s of growth, the growth was stopped. The epitaxial wafer was transferred into the buffer chamber and the vacuum in the growth chamber was waited for to be lower than 1×10 -10 Torr, after being introduced, the barrier layer is grown. After 50,000 seconds of growth, the temperature is naturally lowered to 80°C in a vacuum and stopped.

[0036] Figure 4 The concentration distribution diagram of BIB prepared in Example 1, the gray part is the interface area. Figure 4 It can be seen that by the above-mentioned growth method of the absorption layer and the barrier layer, compared with Figure 6 The concentration distribution obtained by testing the conventional CVD epitaxial BIB wafer can achieve a narrow interface between the absorption layer and the barrier layer.

[0037] Example 2

[0038] The preparation method of this embodiment is the same as that of embodiment 1, except that the evaporation beam of silicon is adjusted to

[0039] Example 3

[0040] The preparation method of this embodiment has the same growth conditions as the absorption layer of embodiment 1, and the difference from embodiment 1 is that the evaporation beam of silicon is adjusted to The best growth rate is determined by comparing epitaxial doped absorption layer films grown at different growth rates.

[0041] Figure 5 Shows different growth rates The XRD half-peak width under HR-XRD was used to test the corresponding film and obtain the (400) rocking curve. The half-peak width of XRD can reflect the orderly arrangement of the lattice. For the best.

[0042] Through Example 1, it can be seen that MBE can realize BIB structure. The proposal of this method is conducive to the extension to other BIB epitaxy methods, and realizes 4-inch, 13μm thick BIB structure epitaxy. At the same time, the intrinsic layer concentration test reaches the current SIMS test limit (5×10 14 cm -3 ). This is also the only reported full-structure epitaxial growth using the MBE method.

[0043] Compared with the traditional CVD growth method, the growth temperature of CVD is generally around 850°C-1100°C, which results in a high diffusion coefficient of the doping element. The interface width is often greater than 1 μm, which is higher than the interface width of the present invention of less than 1 μm.

[0044] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy, characterized in that: The following steps are involved: (1) Place the substrate into the MBE chamber and control the vacuum in the chamber to be less than 1×10 -10 Torr, heat the substrate to 940-960℃, keep it for 28-32min, then lower the substrate temperature to 550-570℃, set the Ga source temperature to 680-700℃, and adjust the electron beam current of the silicon source to (2) Opening the silicon source electron beam baffle and the Ga source baffle to grow the absorption layer; (3) After the epitaxy of the absorption layer is completed, the substrate temperature is raised by 80-100°C. During this period, the silicon source electron beam current is kept unchanged. After 900-1100 seconds of growth, the growth is stopped and the silicon source electron beam baffle and the Ga source baffle are closed at the same time. The epitaxial wafer is sent into the buffer chamber and the vacuum of the MBE chamber is waited for to be lower than 1×10 -10 Torr, and then sent into the MBE chamber, opened the silicon source electron beam baffle, and started the barrier layer growth.

2. The method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy according to claim 1, characterized in that: The resistivity of the substrate is 0.0005-0.001 Ω·cm.

3. The method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy according to claim 1, characterized in that: The thickness of the absorption layer is 6-10 μm.

4. The method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy according to claim 1, characterized in that: The thickness of the barrier layer is 4-6 μm.

5. The method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy according to claim 1, characterized in that: In step (1), the substrate temperature is heated to 950°C and maintained for 30 minutes, then the substrate temperature is reduced to 560°C and the Ga source temperature is set to 690°C.

6. The method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy according to claim 1, characterized in that: In step (2), the time for growing the absorption layer is 75000-85000s.

7. The method for preparing silicon-doped gallium very long wave infrared detection material based on molecular beam epitaxy according to claim 1, characterized in that: In step (3), the growth time of entering the MBE cavity is 45000-55000s.

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