Implantation-enhanced interdiffusion of CdTe-ZnTe heterostructures

Implantation-enhanced interdiffusion of CdTe-ZnTe strained heterostructures is studied by photoluminescence, channeling, transmission electron microscopy, and secondary-ion-mass spectrometry. In the tellurides, implantation defects significantly diffuse and anneal out during implantation, so that only residual extended defects are found, at depths several times greater than the implantation projected range Rp. As a result, interdiffusion is achieved during the implantation, and not during the subsequent annealing which only serves to eliminate the residual defects, thereby restoring the optical properties of the heterostructures. Evidence has been found for trapping of residual defects at the interfaces, perhaps due to strain, and of slower diffusion in multiple quantum wells than in bulk material. These interface-trapped defects are quite hard to anneal out, so that single quantum wells exhibit poor optical properties after implantation and annealing, while multiple quantum wells give rise to nice photoluminescence spectra with sharp blue-shifted lines and appear as promising candidates to realize lateral confinement.