Finite temperature optoelectronic properties of BAs from first principles

Abstract

The high thermal conductivity of boron arsenide (BAs) makes it a promising material for optoelectronic applications in which thermal management is central. In this work, we study the finite temperature optoelectronic properties of BAs by considering both electron-phonon coupling and thermal expansion. The inclusion of electron-phonon coupling proves imperative to capture the temperature dependence of the optoelectronic properties of the material, while thermal expansion makes a negligible contribution due to the highly covalent bonding character of BAs. We predict that with increasing temperature the optical absorption onset is subject to a red shift, the absorption peaks become smoother, and the phonon-assisted absorption at energies below those of the optical gap has a coefficient that lies in the range 10 −3 -10 −4 cm −1 . We also show that good agreement with the measured indirect band gap of BAs is only obtained if exact exchange, electron-phonon coupling, and spin-orbit coupling effects are all included in the calculations.

Theory of the special displacement method for electronic structure calculations at finite temperature

“…V A is to choose the values of the normal coordinates x qν and y qν so that Eqs. (36) and (43) reproduce the WL average given by Eq. ( 31) in the limit of dense Brillouin-zone sampling.…”

“…Supercell methods derive from earlier frozenphonon approaches [2,40], and do not require the ex-plicit evaluation of electron-phonon matrix elements. In order to sample thermal disorder, the first attempts in this area relied on the Monte Carlo sampling of quantum nuclear wavefunctions, either in the atomic configuration space [25,41,42] or in the space of normal vibrational modes [19,20,43]. The formal basis for this approach is provided by a theory developed in the 1950s by Williams [44] and Lax [45] to study defects in solids, and recently extended by Zacharias et al to finitetemperature optical spectra, phonon-assisted optical processes, and band gap renormalization [25].…”

Electronic and valleytronic properties of crystalline boron-arsenide tuned by strain and disorder

“…12,16 For the sake of clarity, we shall mention here ref. 17 which explore the role played by different exchange-correlation functionals and spin–orbit coupling, showing that the band gap of BAs crystal can vary from 1.197 to 1.717 eV. Here, based on generalized gradient approximation (GGA) we estimate an indirect gap of 1.22 eV.…”

Indirect Band Gap Semiconductors for Thin-Film Photovoltaics: High-Throughput Calculation of Phonon-Assisted Absorption

“…Such calculations are very demanding. As a consequence, ab initio calculations of momentum-indirect absorption have so far been limited to a few materials. − …”