title: Secondary growth mechanism of SiGe islands deposited on a mixed-phase microcrystalline Si by ion beam co-sputtering.
abstract: We discuss the SiGe island co-sputtering deposition on a microcrystalline silicon (μc-Si) buffer layer and the secondary island growth based on this pre-SiGe island layer. The growth phenomenon of SiGe islands on crystalline silicon (c-Si) is also investigated for comparison. The pre-SiGe layer grown on μc-Si exhibits a mixed-phase structure, including SiGe islands and amorphous SiGe (a-SiGe) alloy, while the layer deposited on c-Si shows a single-phase island structure. The preferential growth and Ostwald ripening growth are shown to be the secondary growth mechanism of SiGe islands on μc-Si and c-Si, respectively. This difference may result from the effect of amorphous phase Si (AP-Si) in μc-Si on the island growth. In addition, the Si-Ge intermixing behavior of the secondary-grown islands on μc-Si is interpreted by constructing the model of lateral atomic migration, while this behavior on c-Si is ascribed to traditional uphill atomic diffusion. It is found that the aspect ratios of the preferential-grown super islands are higher than those of the Ostwald-ripening ones. The lower lateral growth rate of super islands due to the lower surface energy of AP-Si on the μc-Si buffer layer for the non-wetting of Ge at 700 °C and the stronger Si-Ge intermixing effect at 730 °C may be responsible for this aspect ratio difference.
authors.affiliation: Institute of Optoelectronic Information Materials, Yunnan University, Kunming 650091, People's Republic of China. Department of Physics, Semiconductor Photonics Research Center, Xiamen University, Xiamen 361005, People's Republic of China.
authors.forename: S Y
authors.initials: SY
authors.lastname: Ke
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: F
authors.initials: F
authors.lastname: Qiu
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Wang
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: Y
authors.initials: Y
authors.lastname: Yang