# The direct and indirect optical absorptions of cubic BAs and BSb

## TL;DR

This study uses first-principles calculations to analyze the optical absorption properties of cubic BAs and BSb, revealing doping strategies to enhance visible-range absorption for photoelectric applications.

## Contribution

It provides a systematic analysis of direct and indirect optical absorptions of BAs and BSb, including the effects of doping and temperature, which was not previously explored.

## Key findings

- Absorption onset corresponds to the indirect bandgap considering phonon-assisted processes.
- Doping reduces the direct bandgap, enhancing visible-range optical absorption.
- Temperature influences the absorption spectra, causing redshift and spectrum smoothing.

## Abstract

Recently, boron arsenide (BAs) has been measured high thermal conductivity in the experiments, great encouraging for the low-power photoelectric devices. Therefore, in the present work, we have systematically investigated the direct and indirect optical absorptions of BAs and BSb and the doping effect of congeners by using first-principles calculations. We obtain the absorption onset corresponding to the value of indirect bandgap by considering the phonon-assisted second-order optical absorptions. And the redshift of absorption onset, enhancement and smoothness of optical absorptions spectra are also captured in the temperature-dependent calculations. In order to introduce one-order absorptions into the visible range, the doping effect of congeners on optical absorptions is studied without the assists of phonon. It is found that the decrease of local direct bandgap after doping derives from either the small bandgap in the prototypical III-V semiconductors or CBM locating at R$_c$ point. Thus, doping of congeners can improve the direct optical absorptions in visible range.