Growth and characterization of GaAs films on Ge/Si composite substrates by metalorganic chemical vapor deposition.

We report the results of studies which have been made on heteroepitaxial layers of GaAs and AlGaAs grown by metalorganic chemical vapor deposition on composite substrates that consist of four different types of heteroepitaxial layered structures of Ge and Ge-Si grown by molecular beam epitaxy on (100)-oriented Si substrates. It is found that of the four structures studied, the preferred composite substrate is a single layer of Ge ~ 1micron thick grown directly on a Si buffer layer. The double crystal X- ray rocking curves of 2micron thick GaAs films grown on such substrates have FWHM values as small as 168 arc sec. Transmission electron micrographs of these Ge/Si composite substrates has shown that the number of dislocations in the Ge heteroepitaxial layer can be greatly reduced by an anneal at about 750C for 30 min which is simultaneously carried out during the growth of the GaAs layer.