Thermal stability of GaAs-on-Si grown by MOCVD.

The stability of structural and electrical properties of GaAs directly deposited on Si by MOCVD is examined. Extended annealing at 900C leads to substantial diffusion of Si across the heterointerface while under the same conditions there is no significant motion of Si incorporated during growth as a dopant into the GaAs surface region. The annealing time and layer thickness dependence of Si diffusivity near the interface is consistent with a defect- modulated mechanism. A large fraction of this Si is electrically inactive. Prolonged annealing at 750C causes no obvious changes in morphology or crystallinity of thin (250angstroms) "islanded" films on Si. The thermal activation energy for Si implant electrical activity is independent of film thickness.