Effects of background n- and p-type doping on Zn diffusion in GaAs AlGaAs multiple-quantum-well structures

The effects of background n- and p-type doping on Zn diffusion in GaAs/AlGa As multilayered structures are investigated by secondary-ion-mass spectrome try and photoluminescence measurements. Zn diffusions are performed at 575 degrees C into Si-doped, Be-doped, and Si/Be-codoped identical GaAs/Al0.2Ga 0.8As multiple-quantum-well structures. The results obtained by secondary-i on-mass spectrometry show that the Zn diffusion induces an enhancement of B e out-diffusion and the disordering of all structures. The effective Zn dif fusivity and the disordering rate are increased by Be doping and reduced by Si doping. Photoluminescence measurements give information about the react ions of different point defects during the diffusion process. Before Zn dif fusion, the Si-doped structures contain a high concentration of column-III vacancies, whereas As vacancies are the dominant defects in the Be-doped st ructures. After Zn diffusion, we observe a reduction of column-III vacancy concentration in Si-doped structures and an increase of column-III intersti tial concentration in Be-doped structures. A model based on the "kick-out" mechanism of Zn diffusion is proposed to explain our observations. The supe rsaturation of column-III interstitials behind the Zn diffusion front is re sponsible for the enhancements of Al-Ga interdiffusion and Be out-diffusion . The effective Zn diffusivity is controlled by the background donor or acc eptor concentration ahead of the Zn diffusion front and by the concentratio n of column-III interstitials behind the Zn diffusion front. For Be-doped s tructures, the increase in the background acceptor concentration and the su persaturation of column-III interstitials in the Zn-diffused region results in an enhancement of the Zn diffusivity. For Si-doped structures, the effe ctive Zn diffusivity decreases with increasing background donor concentrati on. Moreover, the concentrations of column-III interstitials and column-III vacancies in the Zn-diffused region are reduced due to their mutual annihi lation, leading to a retardation of Zn diffusion. (C) 1999 American Institu te of Physics. [S0021-8979(99)05913-7].