Computational Materials Design: Tuning Optoelectronic Response in GaxIn1-xBiyP1-y Alloys via Structural Matching to InP

Abstract

This theoretical study presents a computational investigation into the structural, electronic, and optical properties of GaxIn1-xBiyP1-y quaternary alloys specifically lattice-matched to an InP substrate, utilizing density functional theory (DFT). The calculations were performed using the full-potential linearized augmented plane wave (FP-LAPW) method. Structural properties were assessed using the local density approximation (LDA) and the Wu-Cohen generalized gradient approximation (WC-GGA), with WC-GGA used to define the lattice-matching target based on the calculated InP lattice constant. Electronic properties were determined using the Engel-Vosko GGA (EV-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) functionals. Optical properties were analyzed in detail, with optical band gaps derived using Tauc's method. Lattice-matching conditions to InP were established, yielding calculated lattice constants around 5.9 Å for matched compositions (x, y), in excellent agreement with the experimental InP value (5.869 Å). Band structure analysis confirms these alloys are direct band gap semiconductors at the Γ point for all studied lattice-matched compositions. The investigation of optical properties reveals that the electronic band gaps (via TB-mBJ) correspond to wavelengths spanning approximately 0.91 μm to 2.46 μm, while Tauc analysis yields optical band gaps corresponding to ~0.9 μm to ~1.56 μm, all while maintaining lattice matching. These findings highlight GaxIn1-xBiyP1-y/InP alloys as promising materials for optoelectronic devices, particularly for telecommunication applications operating at 1.3 μm and 1.55 μm, due to their tunable optoelectronic characteristics and structural compatibility with InP.