Dose-dependent mixing of AlAs-GaAs superlattices by Si ion implantation

Abstract

The effects of Si ion implantation and annealing on AlAs‐GaAs superlattices are examined with secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). Samples implanted with 180 keV ²⁸Si⁺ of doses ranging from 3×10¹³ to 3×10¹⁵ cm⁻² are examined before and after a 3‐h 850 °C anneal. Both the TEM and RBS channeling data indicate the formation of a heavily damaged surface layer where diffusion of Al is inhibited even after thermal annealing. After annealing, however, significant mixing is observed at depths well beyond the implant range. Depth‐dependent diffusion lengths of Al and Si are derived from the SIMS data. The diffusion coefficient of Si is markedly reduced in the unmixed regions with both the Si and Al concentrations exhibiting abrupt forward and rear diffusion fronts.