Samples which had been implanted with 220keV Si ions to doses ranging from 3 x 1013 to 1015/cm2, and annealed at 850C, were studied. By using transmission electron microscopy, voids were observed in samples with implanted doses of more than 3 x 1014/cm2; after annealing times which were as short as 5s. In the same region where voids were found, capacitance-voltage measurements revealed abnormally low electron concentrations. Also in the same region, secondary ion mass spectrometry measurements detected anomalies in the Si concentration profiles. It was therefore deduced that Si redistribution had occurred. At high Si doses, the onset of void formation, the abnormally low electron concentration, and the Si accumulation anomaly were concurrent. On the basis of the results, it was concluded that voids inhibited electrical activity and led to the Si diffusion anomaly.

Void Formation and Its Effect on Dopant Diffusion and Carrier Activation in Si-Implanted GaAs. S.Chen, S.T.Lee, G.Braunstein, K.Y.Ko, L.R.Zheng, T.Y.Tan: Japanese Journal of Applied Physics, 1990, 29[11], L1950-3