Crystal orientation of CdTe Film on GaAs by MOCVD.

The native oxide on (100) GaAs substrates influences the epitaxial crystal orientations of CdTe films grown by MOCVD. Annealing GaAs substrates to about 585C in hydrogen can be effectively remove the oxide film. On annealed (100) GaAs substrates, (111) CdTe films with excellent morphology can be reproducibly grown. Whereas on unannealed (100) GaAs substrate, (100) CdTe will be obtained unless the substrate is freshly prepared. Cross-sectional TEM shows that the (100)CdTe/(100)GaAs interface has a high defect density because of the large lattice mismatch between (100)CdTe and (100)GaAs. TEM studies also show the formation of twin plates within the (111) CdTe epilayer. The density of the twin plates decrease progressively towards the surface of the CdTe film.