Tailoring Type II Strained Layer InAs/InGaSb Superlattices for Long Wavelength Infrared Detector Applications

摘要

A comprehensive theoretical study has been carried out on the design of long wavelength infrared detector materials from type II InAs/In_xGa_(1-x)Sb strained layer superlattices (SLs) with absorption energies in the 10-12 μm range. Absorption α(ηω) calculations are difficult, however, because of the strong misalignment of the band edges of the two host materials at the interface and because of a large lattice mismatch. The influence from strain, layer thickness, and alloy composition on the SL energy band gaps E_g~(SL), cut-off wavelengths λ_c, and optical matrix elements have been analyzed. A modified empirical tight binding (ETB), effective bond-orbital (EBO) and 8 * 8 k.p models are employed in the study of band structure. The strain in the ETB is included by scaling the matrix elements according to the Harrison's universal 1/d~2 rule and by modifying the angular dependence while in the EBO and k.p schemes it is incorporated via the deformation theory. The study of α(ηω) for thin layer SLs in the k.p scheme revealed enhancement of absorption with increasing In composition x in In_xGa_(1-x)Sb at a fixed energy due to the large overlap of electron-hole wave-functions.