A preparation method of a strain-balanced superlattice based on InAs / InAsSb

Abstract

The application provides a preparation method of an InAs / InAsSb-based strain-balanced superlattice, which comprises the following steps: step 1, performing degassing on a GaSb (100) substrate; step 2, performing deoxidation treatment on the GaSb (100) substrate; step 3, growing a GaSb buffer layer on the GaSb (100) substrate at a temperature of 465 DEG C, wherein the five-to-three beam current ratio of Sb to Ga is 5; step 4, reducing the temperature to 385 DEG C at a temperature reduction rate of 20 DEG C / min, and growing 100 periods of InAs / InAs x Sb 1‑x superlattice, wherein the In source furnace temperature is 838.3 DEG C, the As source furnace temperature is 380 DEG C, the Sb source furnace temperature is 620 DEG C, the five-to-three beam current ratio of As to In is 6, and the five-to-three beam current ratio of Sb to In is 3.7. The application realizes the growth of a high-quality InAs / InAsxSb1-x type II superlattice structure on a GaSb substrate by a molecular beam epitaxy (MBE) method, the superlattice structure is composed of 100 periods, and the problem of superlattice strain imbalance is solved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic technology, and in particular to a method for preparing strain-balanced superlattices based on InAs / InAsSb. Background Technology

[0002] Currently, the more mature material systems for fabricating mid-wave infrared detectors with high operating temperatures include InSb, HgCdTe (Mercury cadmium telluride, MCT), and type II superlattice materials.

[0003] The narrow bandgap of InSb cannot effectively cover the entire mid-infrared region. Furthermore, mid-infrared focal plane arrays fabricated with InSb require relatively low temperatures (80-100K), limiting their application in small-volume infrared imaging devices. Multi-phase superlattices (MCTs) have been widely used in the mid-infrared field due to their excellent optical absorption efficiency (80% internal quantum efficiency), tunable band structure, and long minority carrier lifetime (2-60μs). However, the presence of toxic elements, high Auger recombination rates, large interband tunneling currents, poor material uniformity, low yield, and weak ionic bond energies of group II-VI superlattices limit their size, performance, operating temperature, and fabrication cost. In particular, achieving uniformity of the focal plane array in MCTs has always been a significant challenge. Type II superlattices, with their excellent electronic bandgap tailoring, long carrier recombination lifetime, low interband tunneling current, good material uniformity, relatively inexpensive substrates, and ability to realize large-area, high-resolution focal plane arrays, have been extensively studied in mid-infrared detection devices.

[0004] The study of type II superlattices focuses on InAs / GaSb and InAs / InAs. x Sb 1-x The main focus is on the presence of Ga atoms in the InAs / GaSb superlattice structure, which leads to Shockley–Read–Hall (SRH) nonradiative recombination and a lower minority carrier lifetime. x Sb 1-x The superlattice contains no Ga atoms, eliminating defect states caused by Ga. Furthermore, the heterojunction interface is simpler, allowing for a longer carrier lifetime. InAs / InAs x Sb 1-x Heterojunctions have two identical elements (In and As), with only Sb being a variable element, resulting in a simpler heterojunction interface structure. InAs / InAs x Sb 1-xThe band structure of a superlattice depends on the layer thickness and the As / Sb ratio. Since In and As can be kept consistently in an open state during molecular beam epitaxy (MBE), the entire superlattice growth process can be completed simply by controlling the Sb source baffle valve, potentially leading to better interface control and higher yields in large-scale production. However, in InAs / InAs... x Sb 1-x Different Sb compositions during superlattice growth lead to lattice mismatch, and the superlattice exhibits strain, which in turn affects detector performance. Summary of the Invention

[0005] To address the issues in existing InAs / InAs technologies x Sb 1-x The different Sb compositions during the superlattice external growth process lead to excessive lattice mismatch, and the superlattice exhibits strain, thus affecting detector performance. One objective of this invention is to provide a method for fabricating a strain-balanced superlattice based on InAs / InAsSb, the method comprising the following steps:

[0006] Step 1: Degas the GaSb(100) substrate;

[0007] Step 2: Deoxidize the GaSb(100) substrate;

[0008] Step 3: Grow a GaSb buffer layer on a GaSb(100) substrate at a temperature of 465℃, wherein the Sb to Ga beam current ratio is 5.

[0009] Step 4: Cool to 385℃ at a cooling rate of 20℃ / min, and grow InAs / InAs at this temperature for 100 cycles. x Sb 1-x The superlattice has an In source furnace temperature of 838.3℃, an As source furnace temperature of 380℃, and an Sb source furnace temperature of 620℃. The As to In current ratio is 5:3, and the Sb to In current ratio is 3:3.7.

[0010] Preferably, the GaSb(100) substrate is an n-type doped GaSb(100) semiconductor wafer substrate.

[0011] Preferably, in step 1, degassing the GaSb(100) substrate includes the following steps:

[0012] The GaSb(100) substrate is introduced into the degassing chamber and baked at 300°C for 2-3 hours to degas. Degassing is completed when the pressure in the degassing chamber is below 2×10-9 mbar and remains stable.

[0013] Preferably, step 2, the deoxidation treatment of the GaSb(100) substrate includes the following steps:

[0014] The GaSb(100) substrate was introduced into the growth chamber, the initial temperature was set to 100℃, the temperature was increased to 520℃ at a rate of 20℃ / min and maintained for 10min, and the Sb source furnace needle valve was opened during the deoxidation process. Deoxidation was carried out under the protection of Sb atmosphere, and the substrate holder was rotated at a speed of 3rpm.

[0015] Preferably, in step 3, the thickness of the grown GaSb buffer layer is 500 nm.

[0016] This invention provides a method for fabricating strain-balanced superlattices based on InAs / InAsSb. By using molecular beam epitaxy (MBE), high-quality InAs / InAsxSb1-xII type superlattice structures are grown on GaSb substrates. The superlattice structure consists of 100 periods, which solves the problem of strain imbalance in superlattices.

[0017] This invention provides a method for preparing strain equilibrium superlattices based on InAs / InAsSb, utilizing InAs / InAs grown by MBE. x Sb 1-x The superlattice structure exhibits sharp and distinct satellite peaks, with the 0th-order satellite peak nearly coinciding with the substrate peak. This achieves strain balance during material growth and demonstrates excellent stability and repeatability. It can provide a good absorption region material for high-temperature mid-wave infrared detectors, maintaining a small lattice mismatch with the GaSb substrate, thereby improving the performance of the infrared detector.

[0018] This invention provides a method for preparing strain-equilibrium superlattices based on InAs / InAsSb, which achieves InAs / InAsSb by optimizing the growth method. x Sb 1-x Tuning the Sb composition in superlattices to achieve high-quality strain equilibrium InAs / InAs x Sb 1-x The growth of superlattices provides excellent absorption region materials for the fabrication of focal plane arrays for mid-wave infrared detection at high operating temperatures. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1The diagram illustrates the structure of an InAs / InAsSb strain equilibrium superlattice prepared according to a method for preparing an InAs / InAsSb strain equilibrium superlattice in one embodiment of the present invention.

[0021] Figure 2 The diagram illustrates the growth time and source furnace switching sequence during a method for preparing an InAs / InAsSb-based strain equilibrium superlattice according to an embodiment of the present invention.

[0022] Figure 3 The diagram illustrates the relationship between Sb composition, full width at half maximum (FWHM), and strain in strain-equilibrium superlattices of InAs / InAsSb prepared with Sb and In at different 5:3 beam current ratios.

[0023] Figure 4 A schematic diagram of the XRD rocking curve of an InAs / InAsSb strain equilibrium superlattice prepared in one embodiment of the present invention is shown.

[0024] Figure 5 An AFM surface test image of an InAs / InAsSb strain-equilibrium superlattice prepared in one embodiment of the present invention is shown. Detailed Implementation

[0025] To make the above and other features and advantages of the present invention clearer, the invention will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explanation to those skilled in the art and are exemplary only, not restrictive.

[0026] To address the issues in existing InAs / InAs technologies x Sb 1-x The varying Sb composition during superlattice growth leads to lattice mismatch, and the strain in the superlattice affects detector performance. This paper proposes a method for fabricating strain-balanced superlattices based on InAs / InAsSb. According to an embodiment of the invention, InAs / InAsSb superlattices are fabricated using the COMPONENT molecular beam epitaxy system in Germany. x Sb 1-x Superlattice growth is performed.

[0027] According to an embodiment of the present invention, Figure 1 The illustration schematically shows the structure of an InAs / InAsSb strain equilibrium superlattice prepared according to a method for preparing an InAs / InAsSb strain equilibrium superlattice in one embodiment of the present invention. The method for preparing an InAs / InAsSb strain equilibrium superlattice includes the following steps:

[0028] Step 1: Degas the GaSb(100) substrate 101.

[0029] The GaSb(100) substrate 101 uses an n-type doped GaSb(100) semiconductor wafer substrate for InAs / InAs... x Sb 1-x Growth of superlattices.

[0030] Before growth, the GaSb(100) substrate 101 needs to be degassed to prevent the introduction of impurities from the outside that could affect the superlattice growth quality. The GaSb(100) substrate 101 is placed in a degassing chamber and baked at 300°C for 2-3 hours to remove gas. When the pressure in the degassing chamber is below 2 × 10⁻⁶... -9 mbar and remain stable, i.e., degassing is completed, and the GaSb(100) substrate 101 is transferred into the growth chamber for deoxidation and epitaxy.

[0031] Step 2: Deoxidize the GaSb(100) substrate.

[0032] The GaSb(100) substrate 101 was deoxidized at 520℃ to remove the surface oxide layer and thus improve the growth quality of the superlattice material.

[0033] The GaSb(100) substrate was introduced into the growth chamber, with an initial temperature of 100℃. The temperature was increased to 520℃ at a rate of 20℃ / min and maintained for 10 minutes. During deoxidation, the Sb source furnace needle valve was opened to allow deoxidation to proceed under an Sb atmosphere, preventing the desorption of Sb atoms from the substrate. The substrate adapter was rotated at 3 rpm during both deoxidation and growth to ensure uniformity.

[0034] Step 3: At a temperature of 465°C, a GaSb buffer layer 102 is grown on a GaSb(100) substrate 101, wherein the Sb to Ga beam current ratio is 5.

[0035] To compensate for the increased surface roughness of the GaSb(100) substrate 101 after deoxidation, therefore, in InAs / InAs x Sb 1-x Before the growth of superlattice 103, a GaSb buffer layer 102 is grown to achieve InAs / InAs. x Sb 1-x Lattice matching between the superlattice and the substrate.

[0036] Based on GaSb buffer layer 102 and InAs / InAs x Sb 1-xThe required beam current for each source furnace in the superlattice 103 growth was determined, and the source furnace temperatures for Ga and In, as well as the sizes of the As and Sb needle valves, were determined to control the beam current. A beam current ratio of 5:3 for Sb / Ga was selected, and a 500 nm GaSb buffer layer 102 was grown at 465 °C.

[0037] Step 4: Cool to 385℃ at a rate of 20℃ / min, and grow InAs / InAs at this temperature for 100 cycles. x Sb 1-x The superlattice (12ML / 4ML) has an In source furnace temperature of 838.3℃, an As source furnace temperature of 380℃, and an Sb source furnace temperature of 620℃. The As to In 5:3 beam current ratio is 6, and the Sb to In 5:3 beam current ratio is 3.7.

[0038] like Figure 2 The diagram shows the growth time and source furnace switching sequence during the fabrication of a strain equilibrium superlattice based on InAs / InAsSb according to one embodiment of the present invention. In a specific embodiment, firstly, the In source furnace temperature is set to 838.3℃, the As source furnace temperature is set to 380℃, and the As to In beam current ratio of 5:3 is set to 6, ensuring that the In and As source furnaces are in the on state and maintained for 40.8s to form the InAs layer.

[0039] Then, the InSb interface is formed by interrupting for 3 seconds, thereby blocking the replacement of family V elements.

[0040] Finally, the three source furnaces, In, As, and Sb, were turned on simultaneously. The In source furnace temperature was set to 838.3℃, the As source furnace temperature to 380℃, and the Sb source furnace temperature to 620℃. The 5:3 beam ratio of As to In was 6, and the 5:3 beam ratio of Sb to In was 3.7. The InAsSb layer was grown for 17.5 seconds.

[0041] The In source furnace temperature was 838.3℃, the As source furnace temperature was 380℃, and the Sb source furnace temperature was 620℃, and these temperatures were maintained constant throughout the growth process. The In beam current at 838.3℃ was obtained through preliminary beam current measurements. The beam current was controlled by adjusting the opening and closing of the group V source furnace needle valve, maintaining the As / In 5:3 beam current ratio at 6 and the Sb / In 5:3 beam current ratio at 3.7, thus ensuring 100 cycles of InAs / InAs growth. x Sb 1-x Superlattice growth.

[0042] Experimental verification.

[0043] With the As / In 5:3 beam ratio kept constant at 6, the Sb / In 5:3 beam ratio was varied to 0.9, 1.6, 2.3, 3, and 3.7, resulting in five groups of InAs / InAs... xSb 1-x Superlattice growth. High-resolution X-ray diffraction (HRXRD) was used to characterize the grown superlattice structure, and the Sb composition, strain, and full width at half maximum (FWHM) were obtained by fitting the test data. Table 1 shows the Sb composition, FWHM, and strain of InAs / InAsSb strain equilibrium superlattices prepared with different 5:3 beam current ratios. Figure 3 The diagram shows the relationship between Sb composition, full width at half maximum (FWHM), and strain in strain-equilibrium superlattices of InAs / InAsSb prepared with different 5:3 beam current ratios of Sb and In.

[0044] Table 1. Five groups of InAs / InAs1-xSbx superlattices with different V / III ratios

[0045]

[0046] From Table 1 and Figure 3 The data shows that as the Sb / In beam ratio increases, the full width at half maximum (FWHM) of the superlattice gradually decreases, the Sb- fraction increases, and the strain gradually decreases until lattice matching achieves strain equilibrium. The superlattice structure that reaches strain equilibrium is InAs / InAs. 0.64955 Sb 0.35405 .

[0047] like Figure 4 The diagram shows the XRD rocking curve of the strain equilibrium superlattice of InAs / InAsSb prepared in one embodiment of the present invention. Figure 5 The image shows an AFM surface image of an InAs / InAsSb strain equilibrium superlattice prepared in one embodiment of the present invention. The present invention provides a method for preparing an InAs / InAsSb strain equilibrium superlattice, which achieves precise control of the Sb composition by adjusting the V / III ratio of As / In and Sb / In, resulting in a strain equilibrium superlattice structure of InAs / InAsSb. 0.64955 Sb 0.35405 This allows the zero-order satellite peak of the superlattice to coincide with the substrate peak in the XRD test data, achieving lattice matching. This provides an absorption layer material with high absorption coefficient and high lattice quality for mid-wave infrared detectors operating at high temperatures, thereby improving detector performance.

[0048] By measuring the beam currents of three source furnaces (In, As, and Sb), the relationship between the In beam current magnitude and temperature was obtained, as well as the relationship between the As and Sb beam current magnitudes and the size of the source furnace crucible needle valve. The InAs / InAs ratio was determined using the As / In beam current ratio and the Sb / In beam current ratio. xSb 1-x The V / III ratio of elements during superlattice growth, and how to adjust the InAs / InAs ratio by changing the V / III ratio during growth. x Sb 1-x The Sb composition in the superlattice achieves strain equilibrium.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a strain equilibrium superlattice based on InAs / InAsSb, characterized in that, The preparation method includes the following steps: Step 1: Degas the GaSb(100) substrate; Step 2: Deoxidize the GaSb(100) substrate; Step 3: Grow a GaSb buffer layer on a GaSb(100) substrate at a temperature of 465℃, wherein the Sb to Ga beam current ratio is 5. Step 4: Cool to 385℃ at a cooling rate of 20℃ / min, and grow InAs / InAs at this temperature for 100 cycles. x Sb 1-x The superlattice has an In source furnace temperature of 838.3℃, an As source furnace temperature of 380℃, an Sb source furnace temperature of 620℃, an As to In 5:3 beam current ratio of 6, and an Sb to In 5:3 beam current ratio of 3.

7. Step 1, the degassing of the GaSb(100) substrate includes the following steps: The GaSb(100) substrate was placed in the degassing chamber and baked at 300°C for 2-3 hours to remove gas. When the pressure in the degassing chamber was below 2×10⁻⁶, the degassing was completed. - 9 mbar and maintain a stable state to complete degassing; Step 2, the deoxidation treatment of the GaSb(100) substrate includes the following steps: The GaSb (100) substrate was introduced into the growth chamber, the initial temperature was set to 100℃, the temperature was increased to 520℃ at a rate of 20℃ / min and maintained for 10min, and the Sb source furnace needle valve was opened during the deoxidation process. Deoxidation was carried out under the protection of Sb atmosphere, and the substrate holder was rotated at a speed of 3rpm.

2. The preparation method according to claim 1, characterized in that, The GaSb(100) substrate is an n-type doped GaSb(100) semiconductor wafer substrate.

3. The preparation method according to claim 1, characterized in that, In step 3, the thickness of the grown GaSb buffer layer is 500 nm.

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