The InAs/InAsSb nBn structure detector without Ga (GA-free) has fewer internal defects, and the barrier blocks majority carrier while allowing the normal transport of photogenerated carriers. The unique structure can effectively suppress the generation-composite current generated by SRH, and achieve low dark current at high operating temperature. In this paper, a mid-infrared Ga-free nBn T2SL detector is investigated. The device exhibited 7.43x10-6 A/cm2 under 0.5 V bias at 127 K. At 120K, the detector achieves quantum efficiency values of 56%, exhibits excellent photoelectric performance.
The interfacial asymmetry and compositional disorder caused by atomic segregation and exchange significantly affect the electrical properties of the InAs/InAsSb superlattice, leading to deviations from original designs. The study presents a quantitative analysis of the compositional asymmetry of the superlattice and its effects using a segregation model and 8-band k.p model. The composition disorder at each interface, primarily induced by Sb segregation, is examined through the reconstruction of the actual atomic sequence structure based on scanning tunneling microscopy results. Three different atomistic structures of the superlattice are modeled using the k.p method, including the ideal MBE-growth structure, a rebuilt structure with Sb segregation only at the InAs-on-InAsSb interface, and a rebuilt structure with Sb segregation at both interfaces. The results of the modeling highlight the significant influence of Sb segregation on the electronic properties of InAs/InAsSb superlattices.
Sb segregation is the main contributor to the interfacial asymmetry of the InAs/GaSb superlattices. We reconstructed and quantified the Sb segregation profile in the InAs/Ga(In)Sb superlattice by a one-dimensional model using the postprocessing technique on cross-sectional STM images. The model shows a totally different profile between InAs-on-Ga(In)Sb interface and Ga(In)Sb-on-InAs interface. The asymmetric compositional profile is then added to the 8-band k.p model to investigate its effects on the band structures of the superlattice. With the Sb segregation, the effective band gap of the InAs/GaSb superlattice shifts towards a shorter wavelength. We hope that our work would provide a way to accurately predict the band structures of the InAs/GaSb superlattices by considering the nonideal interfaces.
The band structures of the InAs/GaSb type-Ⅱ superlattice are investigated using the 8-band k.p method. The finite difference method (FDE) is used for solving the Schrödinger equation. It is found that a small variation in the valence band offset (VBO, one of the input parameters) could cause a great change in cut-off wavelength, especially at the long-wavelength range. We also developed a GUI application based on this method. Users could quickly get band structure details, such as bandgap energy, miniband energy, and wavefunctions with this GUI. The program and its code are available at https://github.com/STONEDIY/K.p-Mehtod-for-InAs-GaSb-Superlattice-Band-Structure-Calculation.
We report on the fabrication of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers operating in the 2-μm region. Second-order metallic gratings of chromium are patterned by electron beam lithography. The fabricated DBR lasers emit a single-mode continuous wave at 2.04 μm. The side mode suppression ratio (SMSR) is as high as 35dB with a narrow line-width of 37MHz. The devices show a stable single mode operation with current tuning rate of 0.006nm/mA.
We report the optimum growth parameters of InAs/AlSb superlattices (SLs) for interband cascade lasers (ICL) grown by the solid-source molecular beam epitaxy(MBE). The InAs/AlSb superlattices samples were grown on GaSb substrate at different temperatures and characterized by high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and photoluminescence (PL). By changing the group-Ⅴ flux ratio during the SLs growth, the InAs/AlSb superlattices matched to GaSb substrate were obtained. Subsequently, the SLs were grown at different growth temperature. By photoluminescence we found the highest PL intensity was obtained when the SLs samples were grown at 458°C and the PL wavelength is at 1730 nm. From 10 × 10 μm2 AFM image, we found the root mean square (RMS) of the sample grown at 458°C was 1.96 Å which indicates the low surface roughness and god surface morphology.
We demonstrated high power semiconductor diode lasers emitting around 2.1 μm with the micro-stripe broad area (MSBA) structure which was proposed to improve the broad area (BA) lasers’ lateral beam quality. 1.28W output power at 7A at continuous wave (CW) operation was achieved from the uncoated MSBA laser. It is shown that the micro-stripe structure would lead to worse threshold current and slope efficiency of the lasers because of the less-pumped lossy regions. However, the MSBA lasers would have better heat dissipation system with proper micro-stripe structure and gain advantages on power performance at high currents.
We report the wavelength tuning of type-II “W” quantum well of interband cascade laser. By changing the thickness of the InAs electron well, the wavelength of the active region is adjusted. We found that the whole 3-4 μm spectra can be realized and the intensity was basically the same by measuring the photoluminescence (PL) of the active region. It showed that the type-II “W” quantum well of interband cascade laser can achieve 3-4 μm range without attenuation. In addition, we calculated the wavelength of quantum well of different InAs thickness by the 8-band k·p method. And we found that the wavelength of the active region varies with the thickness of the InAs electron well, which is consistent with the theory. In addition, the measured wavelength was different from the theoretical wavelength, which may be due to the As incorporation. The incorporation of As into the InGaSb layer will lead to blue shift in the wavelength.
The semiconductor epitaxial design and lasing characteristics of an optically barrier-pumped GaSb -based semiconductor disk laser (SDL) emitting at 2.0 μm optimized for resonant optical barrier pumping around 1470 nm are presented. Compared to conventional barrier-pumped devices with pump wavelength of 980nm, the novel barrier-pumped device with the smaller quantum deficit reaches a significantly higher power efficiency, and thus a higher output power at a given pump power, due to the lesser internal heat generation. Using an intracavity SiC heat spreader, a cw output power in excess of 300 mW has been achieved at a heat sink temperature of +15 °C, and still more than 500 mW at +10 °C.
We report on successful fabricating of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers emitting at 2080nm. Second-order Bragg gratings of chromium were patterned by electron beam lithography. For 1.5- mm-long laser diode, single mode continuous-wave operation with side mode suppression ratio (SMSR) as high as 30dB is obtained. The line-width of the lasing wave is kept as narrow as 70MHz. The devices show a stable single mode operation with current tuning rate of 0.01nm/mA.
Special processing of rapid thermal annealing on the cavity coating films for 1950 nm wavelength antimonide quantum well Laser diodes are studied. The maximum output power of the laser is greatly improved by RTA process on cavity facet films from around 610mW to above 700mW. The power conversion efficiency is further improved by the simple process by 23.2% than that of the laser coated. And the laser devices become more reliable and have extended service life after the process.
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