Insights into structural and dynamical characteristics of III-V boron polytypes

Abstract

III-V boron materials are a class of semiconductors with a wide range of outstanding properties and applications. In this paper, the density functional theory is used to explore the structural phase stability, atomic structure, electron band structures and dynamics properties of cubic (3C) and hexagonal (2H) polytypes of boron III-V compounds. We show that polytypism has generally a weak impact on electronic and lattice dynamics properties of BP, BAs, BSb, and BBi.We find small total energy difference between cubic and hexagonal boron-V compounds (~18.7meV/atom, ~15.8meV/atom, ~6.9meV/atom, and ~15.8meV/atom for BP, BAs, BSb and BBi respectively). Accurate quasiparticle (modified Becke-Johnson (mBJ) potential, and local density approximation-1/2) schemes predicted indirect bandgap for 3C and 2H phases of BP, BAs and BSb. Interestingly, BBi evidence narrower direct bandgap for both cubic (~0.38eV) and hexagonal (~0.19eV) crystal polytypes, which makes BBi compound a promising candidate for optoelectronic applications such as infrared sources and detectors. The dynamical stability of 2H boron compounds has also been studied to unravel the possible feasibility of experimental realizations of these compounds. Moreover, we find that the phonon properties of boron III-V compounds contrast considerably with other III-V materials, such the overbending of the transverse optical branches, the bunching of the acoustic branches, the weak LO-TO splitting, and the atypical negative Born effective charges.