Selective epitaxial growth of GaAs on Ge by MOCVD

摘要

We have selectively grown thin epitaxial GaAs films on Ge substrates with theaid of a 200 nm thin SiO2 mask layer. The selectively grown structures havelateral sizes ranging from 1 um width up to large areas of 1 by 1 mm2. Thegrowth with the standard growth procedure for GaAs growth on Ge substratesreveals a limited amount of GaAs nucleation on the mask area and strong loadingeffects caused by diffusion of group III precursors over the mask area and inthe gas phase. Reduction of the growth pressure inhibits GaAs nucleation on themask area and reduces the loading effects strongly, but favors the creation ofanti phase domains in the GaAs. An optimized growth procedure was developed,consisting of a 13 nm thin nucleation layer grown at high pressure, followed bylow pressure growth of GaAs. This optimized growth procedure inhibits thenucleation of GaAs on the mask area and is a good compromise between reductionof loading effects and inhibition of anti phase domain growth in the GaAs.X-ray diffraction and photoluminescence measurements demonstrate the goodmicroscopic characteristics of the selectively grown layers.