Author(s): Wan, FS (Wan, Fengshuo); Xu, C (Xu, Chi); Wang, XY (Wang, Xiaoyu); Xu, GY (Xu, Guoyin); Cheng, BW (Cheng, Buwen); Xue, CL (Xue, Chunlai)

Source: JOURNAL OF CRYSTAL GROWTH Volume: 577 Article Number: 126399 DOI: 10.1016/j.jcrysgro.2021.126399 Published: JAN 1 2022

Abstract: Ge1-xSnx materials with constant and step-graded compositions have been successfully grown on Ge/Si(0 0 1) substrates by using low temperature molecular beam epitaxy (LT-MBE). It has been observed that both completely strained and partially relaxed GeSn materials with the same composition could be formed within the same sample, without adjusting any growth parameters. The residual in-plane strain in GeSn changes in a specific pattern from the GeSn/Ge interface towards the surface. The lower section of the GeSn material remains fully strained and free of dislocations, while most of the threading dislocations are located in the upper section of the layer, causing considerable strain relaxation within this section while maintaining the composition unchanged. This behavior could be explained by kinetic roughening and dislocation generation mechanisms at low temperatures and is remarkably different from GeSn materials grown by chemical vapor deposition (CVD), which exhibit a gradual strain relaxation process as growth continues. This work contributes to the fundamental understanding of the strain relaxation mechanisms of GeSn materials grown by MBE, which is instructive for improving the material quality in the future.

Accession Number: WOS:000718377900001

ISSN: 0022-0248

eISSN: 1873-5002

Full Text: https://www.sciencedirect.com/science/article/pii/S0022024821003742?via%3Dihub