Abstract
Photoluminescence coupled with repetitive thermal annealing has been used to determine diffusion coefficients for intermixing in In0.2Ga0.8As/GaAs and GaAs/Al0.2Ga0.8As 100A single quantum wells and to study the effects of doping with silicon and beryllium and of ion implantation on the interdiffusion. It has been shown that the diffusion obeys Pick's law and that doping concentrations of beryllium up to 2.5 x 1019 cm-3 and silicon up to 10 18 cm-3 have no effect on the interdiffusion coefficients in either material system. For the In0.2Ga0.8As/GaAs system it was shown that following implantation and annealing there was a fast interdiffusion process which is independent of implant ion species and anneal temperature. This is thought to be due to recovery of the crystals from implant damage. After this rapid process, it was found that neither gallium nor krypton ions had any further effects on the interdiffusion. However, following arsenic implantation an additional enhanced region of interdiffusion coefficient was observed, with diffusion coefficients an order of magnitude greater than that of a control unimplanted sample. This enhancement is thought to be due to the creation of group in vacancies by the implanted arsenic atoms moving onto group V sites. This fast process was transient in nature returning to that of the unimplanted samples after the well has broadened by about 85A. An activation energy for the diffusion process of 3.7 +/- 0.1 eV was measured over a temperature range of 750-1050°C. This was found to be independent of implanted ion or dopant incorporated in the samples, indicating that the same process controls the interdiffusion in all cases. Similar results were found for the GaAs/Al0.2Ga0.8As system.