Partial intermixing of strained InGaAs/GaAs quantum wells

Shallow ion implantation and rapid thermal annealing (RTA) was used to modify the optical properties of strained InGaAs/GaAs quantum wells (QWs). After RTA, QW exciton energies, determined from peak positions of the photoluminescence spectra, shifted significantly to higher energies in the implanted areas, whereas they remained basically unaffected in the unimplanted regions. The magnitudes of the energy shifts depend on the well width, RTA temperature and ion implantation fluence. The shifts were interpreted as arising from modification of the shapes of the as-grown QWs due to diffusion of In out of the well material. This process is enhanced by diffusion of vacancies generated near the sample surface by ion implantation. QWs with compositions near the critical thickness exhibit different behaviour from that of fully pseudomorphic layers, due to the presence of dislocations in these layers.