The effects of background n-type or p-type doping upon Zn diffusion in multi-layered structures were investigated by performing secondary ion mass spectrometry and photoluminescence measurements. The Zn was diffused, at 575C, into Si-doped, Be-doped or Si and Be co-doped GaAs/Ga0.8Al0.2As multiple quantum-well structures. The secondary ion mass spectrometry results showed that Zn diffusion led to an enhancement of Be out-diffusion, and to disordering of all of the structures. The effective Zn diffusivity, and the disordering rate, were increased by Be doping and were reduced by Si doping. Photoluminescence measurements yielded information concerning the reactions of various point defects during diffusion. Before Zn diffusion, the Si-doped structures contained a high concentration of column-III vacancies, whereas As vacancies were the predominant defects in Be-doped structures. After Zn diffusion, a reduction in the column-III vacancy concentration was observed in Si-doped structures and an increase in column-III interstitial concentrations was noted in Be-doped structures. A model which was based upon the kick-out mechanism of Zn diffusion was proposed in order to explain the observations. A supersaturation of column-III interstitials behind the Zn diffusion front was deemed to be responsible for the enhancement in Al-Ga interdiffusion and Be out-diffusion. The effective Zn diffusivity was controlled by the background donor or acceptor concentration ahead of the Zn diffusion front, and by the concentration of column-III interstitials behind the Zn diffusion front. In the case of Be-doped structures, the increase in the background acceptor concentrations and the supersaturation of column-III interstitials in the Zn-diffused region resulted in an enhancement of the Zn diffusivity. In the case of Si-doped structures, the effective Zn diffusivity decreased with increasing background donor concentration. The concentrations of column-III interstitials and column-III vacancies in the Zn-diffused region were reduced, due to their mutual annihilation; thus leading to a retardation of Zn diffusion.

Effects of Background n- and p-Type Doping on Zn Diffusion in GaAs/AlGaAs Multiple Quantum-Well Structures N.H.Ky, F.K.Reinhart, J.D.Ganière, B.Deveaud, B.Blanchard: Journal of Applied Physics, 1999, 86[1], 259-66