ABSTRACT

The focus of this chapter is to understand the role of defects and damage on intermixing. Ion implantation is a precise and reproducible way of introducing controllable amount of impurities and/or defects in the near surface region. Thus, defect-and/or impurity-assisted interdiffusion process can be easily controlled. The two major mechanisms for intermixing (disordering) are direct collision and diffusion processes [1]. However, the effect of direct collisional disordering is only appreciable at high implantation doses. Although the doses of protons used in this study could be quite high, it is expected that direct collisional disordering is negligible due to

the small mass of this ion. Arsenic and oxygen implantations in this work fall into the diffusion regime because of the small doses used. The diffusion process, on the other hand, relies on impurities and/or native defects and their diffusion rates. A high temperature treatment step is usually required to initiate the interdiffusion process and at the same time remove or minimise the undesirable defects. Although an abrupt GaAs-AlGaAs interface can be grown easily, due to the small diffusion coefficient of Al-Ga [2,3], the presence of impurities and other defects may enhance this diffusion coefficient by orders of magnitude [1-6].