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Void Formation and Its Effect on Dopant Diffusion and Carrier Activation in Si-Implanted GaAs

GaAs samples, implanted with 220 keV Si to doses ranging from 3×1013 to 1×1015 cm-2 and annealed at 850°C were studied. Using transmission electron microscopy (TEM), voids were found in samples with implant doses ≥3×1014 cm-2 after an annealing time as short as 5 s. In the same region where voids were found, capacitance-voltage measurements showed abnormaly low electron concentrations. Also in the same region, secondary ion mass spectrometry (SIMS) measurements showed anomalies in the Si concentration profiles and required the interpretation that a Si redistribution process had occurred. At high Si implant doses, the onset of void formation, the abnormaly low electron concentration, and the Si accumulation anomaly are concurrent. Based on these results, we conclude that voids inhibit the Si electrical activity and lead to the Si diffusion anomaly.