Evidence of stress dependence in the diffusion of point defects in GaAs/GaAlAs heterostructures

We present experimental results on the selective interdiffusion of GaAs/GaAlAs quantum well heterostructures induced by SiO/sub 2/ and Si/sub 3/N/sub 4/ capping and annealing. Comparative studies show that interdiffusion occurs under SiO/sub 2/ in the case of patterned Si/sub 3/N/sub 4/ strips coated with SiO/sub 2/, while interdiffused areas surprisingly appear below Si/sub 3/N/sub 4/ in the reversed case where patterned SiO/sub 2/ strips are coated with Si/sub 3/N/sub 4/. Our work demonstrates that the diffusion of the excess gallium vacancies, which are responsible for the enhanced interdiffusion, is driven by the stress field generated by the dielectric patterned layers.