Photoluminescence studies of as-grown, as well as hydrogenated undoped AlGaAs epitaxial layers, which had been grown by metalorganic vapor phase epitaxy were carried out in order to study the effective passivation of defect centers. Observations were made of the presence of defect-bound exciton lines, and of bound exciton lines in photoluminescence experiments. It was found that, upon hydrogenation, the defect-bound exciton luminescence was considerably reduced; due to passivation of the defects. It was also found that, upon hydrogenation, the excitonic features were enhanced and the photoluminescence emission that was associated with the deep levels was quenched. However, it was well-known that H out-diffused during heat treatment, and it was expected that the photoluminescence spectra would revert back to that seen in as-grown layers. Moreover, a comparison showed that, in a sample that had been grown at a higher substrate temperature (780C), the photoluminescence peak of pair recombination which involved the C acceptor was seen. In samples which had been grown at a lower substrate temperature (730C), this peak was almost absent. This result agreed with earlier work which indicated that, in samples which were grown at higher substrate temperatures, the incorporation of C was greater than for samples which were grown at a lower substrate temperature.

R.Muralidharan, T.Srinivasan, R.Tyagi, M.V.G.Padmavati, M.Bal, R.K.Purohit, S.K.Agarwal: Applied Physics Letters, 1995, 67[14], 2066-8