DIFFUSION INDUCED DISORDER OF GAAS/ALGAAS SUPERLATTICES

Superlattice and multiquantum well structures of differing III-V semiconductors are remarkably stable to thermal annealing. This is in complete contrast to the instability of these structures when an impurity such as Zn or a grown-in impurity such as silicon is diffused into them. Selective area impurity induced disordering of multiquantum well structures has over recent years emerged as a potentially powerful technique for the fabrication of opto-electronc devices and consequently the mechanisms causing this effect are of paramount importance. This paper will therefore concentrate on reviewing the current state of understanding of the fundamental mechanisms. There are however several common threads, for example in N-type materials, the involvement of group III vacancies is generally accepted. Whereas, in the case of P-type dopants like Zn the oversaturation of self-interstitials is required for the enhancement of the interdiffusion. The exact details of the mechanisms will only be found by careful experimentation and modelling.