Isolated Hydrogen Molecules in GaAs

Molecular hydrogen was directly observed in crystalline GaAs by Raman spectroscopy. At T0ex0ex=0ex0ex77K, GaAs samples that have been exposed to a hydrogen/deuterium plasma exhibit four vibrational lines at $2842.6$, $3446.5$, $3925.9$, and 3934.1cm^-1, 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 D₂, HD, and H₂ molecules, respectively.