Electron mobility in Si-doped AlGaAs alloy and GaAs-AlAs pseudo-alloy

We compare the electrical properties of an AlGaAs thin layer and a GaAs-AlA s short-period superlattice, both being doped uniformly with silicon. The c arrier thermal activation is interpreted within the framework of the multid onor splitting of the deep silicon state, the so-called DX centre. We focus on the scattering mechanisms involved in the two structures. In addition t o classical scattering processes, alloy scattering is introduced to account for the behaviour of the Hall mobility with temperature in the alloy. We u tilize the persistent electron photoionization effect in investigating the increase of the Hall mobility with the free carrier concentration. We find that interface roughness scattering cannot account alone for the experiment al behaviour in the superlattice and we suggest that an additional anisotro pic scattering process is probably responsible for this discrepancy owing t o the two-semiconductor structure of the pseudo-alloy.