Hydrostatic pressure was used to study a resonant Raman mode which was observed at 47/cm in highly disordered ion-implanted unannealed material. The mode shifted weakly with pressure (-0.07/cmGPa), thus helping to confirm that this band-resonant vibration arose from the breathing mode of Ga vacancies. These were expected to be present in high concentrations. The pressure coefficient of the longitudinal optical phonon in these (5.5nm) nano-crystals was measured to be 3.6/cmGPa. The good agreement between this value, and the pressure shift of this phonon in bulk GaAs, implied that the bulk modulus was independent of scale down to at least this size of crystallite.

T.Sauncy, M.Holtz, R.Zallen: Physical Review B, 1994, 50[15], 10702-5