Optical transient current spectroscopy was used to investigate defects in low-temperature grown material following post-growth rapid thermal annealing. Two samples were grown at (A) 220C and (B) 360C, onto (001)GaAs substrates. After growth, samples were subjected to rapid thermal annealing (500 to 800C, 30s). Before annealing, X-ray diffraction measurements had shown that the concentrations of excess As were 2.5 x 1019 (A) and 1019/cm3 (B). It was found that there were strong negative decay signals in the optical transient current for annealed A. Due to the influence of the strong negative decay signals, it was impossible to identify deep levels clearly. Three deep levels could be identified in B, before annealing. These comprised 2 shallower deep levels and a so-called AsGa antisite defect. There were still 3 deep levels at an annealing temperature of 600C. However, their structures were different to those in as-grown samples. Optical transient current strong negative decay signals were also observed for annealed B. It was concluded that optical transient current negative decay signals were related to As clusters.

Investigation of Defects in Low-Temperature Grown GaAs Using Optical Transient Spectroscopy. Y.H.Zhang, L.W.Lu, M.H.Zhang, Q.Huang, C.L.Bao, J.M.Zhou: Journal of Crystal Growth, 2000, 220[4], 351-4