Reactions of column-III vacancies and interstitials during Zn diffusion-induced disordering of GaAs/AlGaAs multiple-quantum-well structures

Abstract

Different effects related to the reactions of column-III vacancies and interstitials during Zn diffusion into undoped, Si-doped and Be-doped GaAs/AlxGal−xAs multilayered structures are investigated by secondary-ion mass spectrometry and photoluminescence. The disordering is observed behind the Zn diffusion front in all multilayered structures. The disordering rate increases with increasing x. The Be out-diffusion is enhanced in the Zn-diffused region. The column-III interstitial supersaturation caused by Zn diffusion is believed to be responsible for the enhancements of Al–Ga interdiffusion and Be out-diffusion. The column-III interstitial supersaturation is affected by the presence of column-III vacancies. For undoped samples, the in-diffusion of column-III vacancies generated at the surface is a driving force for the out-diffusion of column-III interstitials. The effective Zn diffusivity and the disordering rate are enhanced by Be doping because of the increase in acceptor concentration and the abundance of column-III interstitials. For Si-doped samples that contain a high concentration of column-III vacancies, the increase in donor concentration and the mutual annihilation of column-III interstitials and vacancies leads to a retardation of the Zn diffusion.