Optical study of narrow band gap InAsxSb1-x (x=0, 0.25, 0.5, 0.75, 1) alloys

Abstract

The structural, electronic, and optical properties of InAs, InSb, and their ternary alloys InAsxSb1-x (x=0.25, 0.5, 0.75) are investigated within density functional theory utilizing the wien2k package. We find that the lattice constants and bulk moduli as a function of x are in best agreement with Vegard's linear rule. When computing the electronic band structures with the modified Becke-Johnson exchange-correlation functional (mBJLDA), our results for the band gaps of InAs, InSb, and their ternary alloys are in good agreement with the available experimental results while the conventional Wu-Cohen generalized gradient approximation (GGA) functional leads to zero or close to zero band gaps. In particular, our mBJLDA results confirm experimental evidence that the minimum band gap occurs for As concentrations around x≈0.3. Furthermore, we investigate the dielectric function of these compounds within the random phase approximation using both the Wu-Cohen GGA and the mBJLDA functionals. While the mBJLDA results of our fully first-principles calculations show good agreement of the peak positions in ε2(ω) with experiments, the peaks in the optical spectra based on the Wu-Cohen GGA band structure appear redshifted compared to experiment. We further identify the interband transitions responsible for the structures in the spectra. Looking at the optical matrix element, we note that the major peaks are dominated by transition from the Sb 5p (As 4p) states to In s states for InSb and InAs0.25Sb0.75 (InAs, InAs0.75Sb0.25, and InAs0.5Sb0.5). © 2015 American Physical Society.