Defect Reduction in GaAs/Si Films with the a-Si Buffer Layer Grown by Metalorganic Chemical Vapor Deposition**Supported by the Fund of State Key Laboratory of Information Photonics and Optical Communications of Beijing University of Posts and Telecommunications, the National Basic Research Program of China under Grant No 2010CB327601, the Natural Science Foundational Science and Technology Cooperation Projects under Grant No 2011RR000100,

Abstract

The growth of GaAs epilayers on silicon substrates with a thin amorphous silicon (a-Si) buffer layer by metalorganic chemical vapor deposition is investigated in detail. Combining with the two-step growth method, the growth conditions of the a-Si buffer layer are optimized for growth of high-quality GaAs/Si epilayers. The a-Si buffer layer exhibits the best effect with thickness of 1.8 nm and growth temperature of 620°C. It is found that the introduction of this a-Si layer on Si substrates effectively reduces the dislocation density in GaAs/Si films. As compared with the dislocation density of 5 × 107 cm−2 in the GaAs/Si sample without the a-Si layer, a density of 3 × 105 cm−2 is achieved in the sample with the a-Si layer, and the defect reduction mechanism is discussed in detail.