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 met- alorganic 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 1.8nm and growth temperature of 620℃. 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.