Transformation of GaAs into an indirectL-band-gap semiconductor under uniaxial strain

Abstract

We report the direct-to-indirect band-gap transition in GaAs under nonhydrostatic compression. Uniaxial strain was produced in GaAs single crystals by impact loading along the [100] and [111] orientations up to longitudinal stresses of 5.5 GPa. Band-gap shifts were determined from low-temperature photoluminescence measurements from Te- and Zn-doped samples. For strain along the [100] direction, GaAs undergoes a $\ensuremath{\Gamma}\text{\ensuremath{-}}X$ band transition similar to what occurs under hydrostatic pressure. Strain along [111], in contrast, produces a large splitting of the $L$ band. This causes the $L$-band minimum to plunge downward and transform GaAs into an indirect $L$-band-gap semiconductor.