LATTICE DAMAGE AND ATOMIC MIXING INDUCED BY AS++ IMPLANTATION AND THERMAL ANNEALING IN ALAS/GAAS MULTIPLE QUANTUM-WELL STRUCTURES

The lattice damage and the nature of the atomic intermixing of Al and Ga induced by As+ + implantation and thermal annealing in AlAs/GaAs multiple quantum-well structures were investigated. The photoluminescence spectra, which show multiple peaks after implantation and annealing, were analyzed based on the shifts of the excitonic peaks arising from quantum wells located at different depths. The depth profiles of intermixing were obtained using a procedure of successive layer-by-layer chemical etching followed by photoluminescence measurements. It is found that the atomic mixing is maximum near the sample surface and decreases monotonically with depth, suggesting that the profiles follow more closely the ion induced damage than the ion density. It is also observed that the radiation damage extends beyond 1-mu-m. Within 0.3-mu-m from the surface, the damage is relatively heavy and the atomic intermixing increases rapidly with ion dose. Beyond 0.3-mu-m, the degree of intermixing is only sensitive to the anneal temperature but not to the implantation dose. The results show that both direct collisions and interdiffusion are responsible for the atomic mixing. For the samples implanted with ion doses below 10(14) cm-2 and annealed at 650-degrees-C, the optical activation from radiation damage is appreciable. However, the interdiffusion becomes important only at temperatures near and above 800-degrees-C.