Compositional dependence of the exciton reduced mass inGaAs1−xBix(x=0–10%)

Abstract

We report the compositional dependence of the exciton reduced mass, ${\ensuremath{\mu}}_{\text{exc}}$, of ${\text{GaAs}}_{1\ensuremath{-}x}{\text{Bi}}_{x}$ in a very large Bi concentration range $(x=0\text{--}10.6\mathrm{%})$. Photoluminescence under high magnetic fields ($B$ up to 30 T) shows that ${\ensuremath{\mu}}_{\text{exc}}$ increases rapidly until $x\ensuremath{\sim}1.5\mathrm{%}$ and then oscillates around $\ensuremath{\sim}0.08\text{ }{m}_{0}$, ${m}_{0}$ being the electron mass in vacuum, up to about $x=6\mathrm{%}$. Surprisingly, for $x>8\mathrm{%}$ the exciton reduced mass decreases below the GaAs value, in agreement with the expectations of a $k\ensuremath{\cdot}p$ model. Such a behavior reveals the existence of different concentration intervals, where continuum states of the valence and conduction band hybridize with Bi-related levels at different extents, thus conferring to the band edges a localized or bandlike character for $x<6\mathrm{%}$ and $x>8\mathrm{%}$, respectively.