Optical transient current spectroscopy, photoluminescence spectroscopy and excitonic electro-absorption spectroscopy were used to investigate the evolution of defects in low-temperature grown multiple quantum-well structures during post-growth rapid thermal annealing. The samples were grown at 350C, using molecular beam epitaxy, onto (001)GaAs substrates which were miscut by 3.4° off (001) and towards (111)A. Following growth, the samples were subjected to rapid thermal annealing (500 to 800C, 30s). It was found that the integrated photoluminescence intensity first decreased with annealing temperature, reached a minimum at 600C and finally recovered at higher temperatures. The optical transient current spectroscopic measurements showed that, besides AsGa antisites and As clusters, there were several relatively shallow deep levels with excitation energies of less than 0.3eV in as-grown and annealed (500C) samples. At annealing temperatures above 600C, the optical transient current spectroscopic signals from AsGa antisites and shallower deep levels became weaker, indicating a decrease in these defects. It was argued that the excess As atoms grouped together to form As clusters during annealing.

Evolution from Point Defects to Arsenic Clusters in Low-Temperature Grown GaAs/AlGaAs Multiple Quantum Wells. M.H.Zhang, Y.J.Han, Y.H.Zhang, Q.Huang, C.L.Bao, W.X.Wang, J.M.Zhou, L.W.Lu: Journal of Crystal Growth, 2000, 217[4], 355-9