Isolated Hydrogen Molecules in GaAs

Abstract

Molecular hydrogen was directly observed in crystalline GaAs by Raman spectroscopy. At $T=77\mathrm{}\mathrm{K}$, GaAs samples that have been exposed to a hydrogen/deuterium plasma exhibit four vibrational lines at $2842.6$, $3446.5$, $3925.9$, and $3934.1{\mathrm{cm}}^{-1\mathrm{}}$, respectively. With a pure hydrogen plasma only the two high frequency lines can be seen and with a pure deuterium plasma only the lowest frequency is observed. We attribute these frequencies to the rovibrational modes of isolated interstitial ${\mathrm{D}}_2$, HD, and ${\mathrm{H}}_2$ molecules, respectively.