EVIDENCE OF STRESS DEPENDENCE IN SIO2 SI3N4 ENCAPSULATION-BASED LAYERDISORDERING OF GAAS/ALGAAS QUANTUM-WELL HETEROSTRUCTURES/

Spatial selectivity of layer disordering induced in GaAs/AlGaAs quantu m well heterostructures using SiO2 and Si3N4 capping and annealing was investigated using low temperature photoluminescence in conjunction w ith cross-sectional transmission electron microscopy. Comparative stud y reveals opposite behaviors for patterned Si3N4 covered with SiO2 and patterned SiO2 covered with Si3N4. In the former, layer disordering o ccurs in the regions located under the SiO2 strips and in the latter l ayer disordering surprisingly occurs under the Si3N4 strips while it i s inhibited in the SiO2-capped areas. These results are in agreement w ith a proposed interdiffusion model based on the effect on Ga vacancy diffusion of the stress distribution generated in the heterostructure during annealing by the capping layers. This work clearly demonstrates that the diffusion of point defects, such as the Ga vacancies, which are responsible for the layer disordering, can be piloted by the stres s held imposed to the semiconductor and opens new perspectives for def ect engineering. (C) 1997 American Vacuum Society.