Secondary-ion mass spectrometry and photoluminescence methods were used to study Zn diffusion into GaAs/Ga0.8Al0.2As multi quantum-well structures which were uniformly doped with Si to concentrations of between 1017 and 1019/cm3. The secondary-ion mass spectrometry profiles which were measured after Zn diffusion at 575C revealed a large effect of the background Si doping level upon the Zn diffusion process and upon Zn diffusion-induced disordering of the multi quantum-well structures. It was found that the Zn diffusivity and the disordering rate significantly decreased with increasing Si background concentration. Before Zn diffusion, the photoluminescence spectra of the multi quantum-well samples revealed an increased intensity of the Si donor-VIII complex emission band with increased Si doping level. This indicated that the VIII concentration in the multi quantum-well structures increased as the Si background concentration increased. After Zn diffusion, a large decrease in the intensity of the VIII-related emission band was detected in the photoluminescence spectra which were obtained from Zn-diffused regions. The results were explained in terms of the kick-out mechanism of Zn diffusion. During the incorporation of Zn into the crystal lattice, column-III interstitials were generated. The supersaturation of IIII behind the Zn diffusion front resulted in an enhancement of Al-Ga interdiffusion in the Zn-diffused region. Since IIII and VIII could mutually annihilate, a reduction in IIII concentration occurred in the Zn-diffused region of Si-doped samples which contained a high VIII concentration. As a result, Zn diffusion and disordering of the multi quantum-well structures were retarded with increasing Si-doping level.

N.H.Ky: Materials Science Forum, 1995, 196-201, 1643-8