The extended short-wave infrared (eSWIR) band (1.7?3 μm) has garnered significant attention due to its critical applications in smoke/fire penetration detection, maritime target recognition, long-range optical communication, and lidar. At present, the material system of detectors in this band faces multiple technical challenges: traditional InGaAs materials can extend detection wavelengths by increasing indium composition, but severe lattice mismatch leads to elevated crystal defect densities, significantly degrading device performance. HgCdTe materials offer excellent spectral tunability, yet their complex epitaxial processes and device fabrication technologies result in prohibitively high production costs. In contrast, InAs/AlSb superlattice (SL) materials demonstrate unique advantages. By alternately growing InAs and AlSb semiconductor layers via molecular beam epitaxy (MBE), this system effectively suppresses generation-recombination (GR) dark currents, trap-assisted tunneling, and band-to-band tunneling, while maintaining low epitaxial and device manufacturing costs. However, two critical challenges remain in InAs/AlSb SL epitaxial growth: alternating layers lack common cations/anions, making interfacial properties decisive for device performance, and residual arsenic contamination during MBE may adversely affect material quality. This study optimizes the surface morphology and interfacial quality of InAs/AlSb SLs by precisely regulating growth temperature parameters. Material quality is systematically evaluated by using atomic force microscopy (AFM), high-resolution X-ray diffraction (HRXRD), and photoluminescence (PL) spectroscopy. The goal is to develop high-performance eSWIR detectors operable at room temperature, advancing practical applications in this spectral range.

The method uses in-situ reflection high-energy electron diffraction to monitor the surface lattice of the substrate. When the reconfiguration diffraction fringe transformation of 2×5 to 1×3 occurs on the GaSb surface, the temperature T_c at this time is used as the reference temperature. Set the growth temperature of SL near the reference temperature. AFM and HRXRD instruments are used to characterize the surface mass and interface mass of materials. The temperature dependent PL spectrum of the material is tested using a Fourier transform infrared spectrometer, and the PL spectrum is analyzed using Varshni empirical formula, Segall formula, and power law fitting formula. The PL signal comprehensively analyzes the effect of growth temperature on the crystalline and optical quality of InAs/AlSb SL materials. In addition, the influence of arsenic background on InAs/AlSb SL materials during the epitaxial growth process is also studied. The test method also uses Fourier-transform infrared spectroscopy (FTIR) to test the PL spectrum signal of variable temperature, which is used to characterize the band gap energy change of the material and determine optical properties.

The prepared InAs/AlSb SL material has a smooth surface morphology and interface quality. The surface root-mean-square (RMS) roughness is as low as 0.2 nm, and the full width at half maximum (FWHM) of HRXRD is 50.7 arcsec. Growing at low temperatures, the material surface has pore defects, and as the temperature increases, the surface becomes smoother. As the growth temperature of SL material continues to rise, needle-like defects appeare on the surface (Fig. 1). In addition, as the growth temperature increases, the FWHM of HRXRD shows a trend of first decreasing and then increasing (Table 2). The study on optical properties of optimized InAs/AlSb SL shows that the temperature sensitivity coefficient value fitted by Varshni is the lowest. The power-law fitting PL intensity of the sample under laser intensity dependence indicates that the nonradiative recombination rate is lower under high temperature (140 K and 200 K) testing (Table 3). In addition, by controlling the As needle valve opening to 9.9% and 8.8%, the arsenic flux is 4×10^-7 mbar and 3×10^-7 mbar, respectively. PL shows that the bandgap energy of the material at low temperatures is V-shaped. The localization depth is 8.79 meV and 4.9 meV, respectively, and they increase with the increase of the arsenic background (Fig. 4). Finally, the dependence of PL intensity on excitation power is tested. The material recombination of As background at low temperatures (<90 K) is due to the emission of localized states towards the microstrip. Under the high-temperature test, the non-radiative recombination rate of SL material decreases with the decrease of As background (Fig. 5).

This study compares the performance of various InAs/AlSb SLs. Samples S1?S6, grown under different temperatures, are characterized using HRXRD, AFM, and FTIR. Sample S3 exhibits significant advantages in HRXRD FWHM (50.7 arcsec), surface RMS roughness (0.2 nm), and temperature sensitivity coefficient extracted from Varshni fitting (α=0.108 meV/K). Notably, its temperature sensitivity coefficient markedly outperforms bulk InAs, InSb, and AlSb materials. Furthermore, power-law fitting of excitation power-dependent photoluminescence (PL) signals reveals that as temperature increases (140?200 K), the recombination mechanism transitions from radiative-dominant to non-radiative-dominant, with sample S3 demonstrating the lowest non-radiative recombination rate. Consequently, the InAs/AlSb SL grown at T_c-15 ℃ achieves optimal crystal and optical quality. Additionally, the impact of arsenic background on optical properties of SL materials is investigated. PL peak energy versus temperature curves for samples S7 and S8 exhibit distinct V-shaped profile. Fitting results indicate that sample S7 (8.79 meV) exhibits deeper carrier localization compared to sample S8 (4.79 meV). Analysis of the excitation power-dependent PL intensity reveals that low-temperature (about 10 K) signals in samples S7 and S8 originate from free-to-bound or donor-acceptor pair recombination, involving free electrons in the SL conduction band and localized holes. At temperatures above 90 K, PL signals arise from recombination between free electrons and holes in SL minibands. Moreover, sample S3 without arsenic background has a lower non-radiative recombination rate in the high-temperature region (90?290 K), so sample S3 has a better high-temperature operation capability for eSWIR application scenarios. Finally, the localization effect of samples S7 and S8 at low temperatures will affect carrier transport, which provides a new idea for future infrared devices.