MBE growth of mid-wavelength infrared photodetectors based on high quality InAs/AlAs/InAsSb superlattice

•The two factors involved Sb component consist of temperature and Sb/As BEP ratio.•The growth rate of AlAs is limited in a narrow scale in high quality epitaxy.•Growth temperature contributes to the two type of dislocation morphology.•Interfaces between InAs and AlAs layer play an important role in SLs epitaxy. InAs/InAsSb type-II superlattices (T2SLs) with long minority carrier lifetimes are promising candidate for InAs/GaSb T2SLs. In this work, we insert AlAs layers into InAs layers to fabricate the InAs/AlAs/InAsSb SLs, applicated in mid-wavelength infrared detection with 5.1 μm cut-off wavelength. We grew InAs/InAsSb SLs on GaSb substrate by MBE in order to confirm the Sb component in InAsSb layer. Meanwhile, the Sb component versus growth temperature and Sb/As BEP flux ratio was explored in the experiment. After that, 5.6/2.2/5.6/8 ML InAs/AlAs/InAs/InAsSb SLs was grown on GaSb influenced by the growth ratio of AlAs. Experiment data indicates that AlAs layers inserted in InAs layers have a narrow growth rate window in the vicinity of 0.3ML/s for high-quality layer-by-layer growth with RMS 1.7 Å characterized by AFM. Then, the optimal growth temperature is found as Tc with RMS reducing to the minimum 1.7 Å and hardly distinct dislocation morphology. Transmission Electron Microscope is necessary method to characterize the microstructure of superlattice. With samples characterized by HRTEM, it is demonstrated that a period contains four layers with the dark layers representing for InAsSb layers and the three bright layers standing for InAs-AlAs-InAs interlayer structure, which interfaces also exhibit clearly. Finally, quality of SLs epitaxy was researched by HRXRD, varying interfaces between InAs and AlAs layers. The intermediate products InAlAs have been eliminated and the FWHMs descend to 30–40 arcsec with the method of 3-second As soak interface.