Pressure effect on the luminescence from the deep level in gallium arsenide

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Abstract
The luminescence band with a peak at 0.68 eV associated with the main deep donor EL2 in undoped GaAs, is studied at 4.2 and 77 K under quasihydrostatic high pressure up to 2.4 GPa. The peak of the EL2-related band shifts with pressure at a rate of 0.015 eV/GPa, which is only 14% of the band-edge shift. We suggest that the luminescence is due to the transition between the conduction band and the EL2 level and that the electronic state of the EL2 level originates mainly from the Γ minimim of the conduction band. The Franck-Condon shift Δ is optically determined to be 0.12±0.01 eV using pressure tuning monitored by the luminescence intensity with the below-band-gap excitation.