Impurity-induced disordering in III–V multi-quantum wells and superlattices

Abstract

Impurity-induced disordering seems to be a general phenomenon affecting all III–V materials. This paper reviews this phenomenon. Before the available data on impurity-induced disordering is discussed, the diffusion mechanisms for the dopants are briefly reviewed, and for silicon-doped material a more detailed discussion is provided because of its technological importance. Moreover, there has been no critical review of the recent progress in silicon diffusion mechanisms. In zinc-diffused multi-quantum wells and superlattices the mechanism for the enhancement of the interdiffusion seems to be primarily by the fast diffusion of group III interstitials whose concentration has been significantly increased over their equilibrium value by the diffusion of the dopant. For silicon impurity-induced disorder the situation is less clear. However, it is certain that the effect of the position of the Fermi level on the native defect concentrations plays a significant role in the disordering mechanism. The study of the other dopants which cause diffusion-induced disordering is less advanced. For n-type dopants there is an argument which suggests that they all have a common cause, namely the increase in the group III triply charged vacancy which is caused by the increase in the Fermi energy. This will be explored in this review. A brief discussion of ion implantation-induced disordering is also provided. This essentially provides a bibliography of the past work in this field. It is clear, for at least one dopant, that there needs to be some damage to the crystal before the enhancement of the interdiffusion occurs. However, for other dopants too much damage reduces the enhancement of the intermixing.