OPTICAL RECOVERY OF PHOTOQUENCHING AT THE MIDGAP ELECTRON TRAPS (EL2 FAMILY) IN GAAS

Partial optical recovery from the metastable state to the normal state was observed at the EL2 centers in liquid encapsulated Czochralski GaAs from photocapacitance measurements. It was found that the optical recovery spectrum has a peak at 0. 855 ev with FWHM of 0. 13 ev and that the recovery process has a strong non-exponentiality. Photoquenching transients at the optically recovered levels show that they are not regarded as a single level. The transition scheme between these states is found to be inconsistent within a simple configuration coordinate diagram model but is more likely to be due to various defect reactions in sizable defects. The result supports an arsenic cluster model for the origin of the EL2 family which we have already proposed.