A photoluminescence study of the donor structure in AlxGa1-xAs

A photoluminescence study at low temperatures of Si-doped Al x Ga 1-x As (0<x<0.6) reveals the existence of four donor levels D 1 , D 2 , D 3 , D 4 , in order of increasing ionisation depth. The number of donor levels and the dependence of their ionisation energies on the composition parameter x accords qualitatively with theoretical expectations. D 1 can be identified with the common 'shallow donor'. D 2 and D 3 have been reported in an earlier PL study by Dingle and co-workers (1977). The position of the D 4 level suggests an identification with the DX centre. Its luminescence properties have been the subject of a previous publication.