Defect Reduction in GaAs/Si Films with the a-Si Buffer Layer Grown by Metalorganic Chemical Vapor Deposition

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.