PHOTO-LUMINESCENCE AT DISLOCATIONS IN GAAS AND INP

The influence of dislocations on the radiative recombination of electron-hole pairs in GaAs and InP is investigated by spatially resolved photoluminescence measurements. The shape of the spectra is unchanged at individual dislocations, while the overall intensity is lowered by about 30% in a region of 5-10 μm around the dislocations. This relative change of intensity is temperature independent in the investigated range 10-300 K. Deformation-induced dislocations, prepared by plastic deformation at 600°C, behave similarly to as-grown dislocations. These statements hold for 60°dislocations and screw dislocations in both n-type and p-type material. Search for dislocation-induced electronic levels in the band gap by deep-level transient spectroscopy, optical absorption, and photoluminescence of GaAs samples with very high dislocation density gives no evidence for such levels. Our findings suggest that the quenching of the radiative recombination near dislocations is caused by an enhancement of the nonradiative bulk mechanisms, rather than by an additional mechanism at dislocations. Possible reasons for this enhancement are discussed. Under special circumstances precipitation or segregation of impurity atoms at dislocations is observed; in these cases the spectrum at dislocations is changed compared to the bulk.