Thermal annealing study of as-grown n-type MOCVD GaAs

Results of isochronal annealing up to a temperature of 660 K of n-type GaAs grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) are reported. Deep-level transient spectroscopy (DLTS) reveals EL2 as the only electron-emitting deep-level defect in our as-grown material, whereas three hole-emitting levels at Ev+0.09 eV, Ev+0.40 eV and Ev+0.93 eV are observed in the minority-carrier injection spectra. While yielding interesting results on the behavior of these pre-existing deep-level defects, thermal annealing is found to introduce at least four new defects, three in the upper half of the band gap at Ec−0.13 eV, Ec−0.16 eV and Ec−0.36 eV, and one in the lower half at Ev+0.19 eV. Two of these defects, one at Ec−0.16 eV and the other at Ec−0.36 eV, are identified with previously reported annealed-in deep levels in n-GaAs, while the other two defects cannot be identified with any of the deep levels reported in the literature. Data on the annealing behavior and other characteristics of these annealed-in levels are presented. All the pre-existing inadvertent deep-level defects in the as-grown material were found to be stable up to 600 K, beyond which the minority-carrier emitting levels start to anneal out, but EL2 tends to show a slight increase with annealing temperature.