Insights into Metastable Defects in Semi-Insulating GaAs from Electronic Raman Studies of Nonequilibrium Holes

We have analyzed the metastable defects in undoped semi-insulating GaAs from a new perspective, that of the electronic Raman scattering of holes generated on the compensated, residual shallow acceptors by cw neodymium-doped yttrium aluminum garnet laser radiation. The scattering results, when correlated with the several photoquenching phenomena, provide information on (i) the charge state of $\mathrm{EL}2\mathrm{}$ defects before they undergo the transition from a normal to a metastable state, and (ii) the relationship between ${\mathrm{As}}_{\mathrm{Ga}}$ compensating centers and metastable $\mathrm{EL}2\mathrm{}$ defects.