Year: 2026
Type: article
Abstract: In this paper we investigate the structural properties and thermal stability of metastable Ge 1 − x Sn x epilayers ( ∼ 4.5 at.% Sn) grown directly on Si(001) substrates by high-resolution x-ray diffraction and Raman spectroscopy. Our results demonstrate that both 70 and 140 nm films are fully relaxed ( R = 100.0 % and 101.9 % ), with no detectable residual strain in the 70 nm film ( | ε ∥ | < 0.02 % ) and a small tensile strain (+0.09%) in the thicker film. The thermal stability of the heterostructures was evaluated up to 813 K using temperature-dependent Raman spectroscopy and scanning electron microscopy. The surface-weighted Raman response (532 nm excitation) and surface morphology of the 70 nm film remain largely preserved, although post-annealing x-ray diffraction reveals a reduction of the substitutional Sn content from 4.5 to 3.15 at.%. In contrast, the 140 nm film undergoes severe degradation, characterized by significant attenuation and broadening of the Ge–Ge longitudinal optical phonon mode, alongside enhanced surface Sn segregation. These findings demonstrate that the thermal stability of direct GeSn/Si heterostructures is governed by the initial defect structure established during epitaxial growth, providing key design rules for understanding the fabrication of GeSn-based optoelectronic devices.
Institution: Indian Institute of Technology Gandhinagar
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Award: G328050186
OpenAlex ID: W7221782759