Strain Relaxation and Relative Defect Density with Thickness in MBE-Grown Ge_0.85Sn_0.15 on Ge(001)

Journal Article · Thu Jun 11 00:00:00 UTC 2026 · Crystal Growth and Design

DOI: https://doi.org/10.1021/acs.cgd.6c00174 · OSTI ID:3376577

Baral, Dinesh  ^[1]; Eldose, Nirosh M.  ^[1]; Zhang, Diandian  ^[1]; Stanchu, Hryhorii ^[1]; Maia de Oliveira, Fernando  ^[1]; Kryvyi, Serhii ^[1]; Zamani-Alavijeh, Mohammad ^[1]; Benamara, Mourad ^[1]; Mazur, Yuriy I.  ^[1]; Du, Wei ^[1]; Yu, Shui-Qing ^[1]; Salamo, Gregory J. ^[1]

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1. Univ. of Arkansas, Fayetteville, AR (United States)

Germanium–tin (GeSn) alloys are emerging as promising materials for mid-infrared optoelectronics and silicon-compatible photonic devices, owing to their tunable direct bandgap. However, the growth of high-quality GeSn films with high Sn content remains challenging due to strain-induced defect formation. In this study, we investigate the role of film thickness on strain-induced relaxation, defect density, and Sn segregation. A series of five samples with varying thicknesses and ∼15% Sn-containing GeSn layers were grown, ranging from the critical thickness for strain relaxation to the onset of Sn segregation. All GeSn samples were analyzed using X-ray diffraction reciprocal space mapping (XRD-RSM) to explore the evolution of strain-induced relaxation as a function of thickness. Photoluminescence measurements reveal that increasing the GeSn thickness enhances strain relaxation while reducing defect-related emission, indicating a decrease in effective defect density prior to reaching the threshold thickness of GeSn layer. At a thickness of ∼150 nm, the GeSn layer shows the onset of Sn segregation, evident in the XRD-RSM spectrum, marking the threshold thickness for Sn segregation. This work defines an effective growth window in terms of thickness (35 to 150 nm) for fabricating relaxed, defect-suppressed GeSn layers with 15% Sn content. These findings emphasize the crucial role of thickness control in balancing strain relaxation and defect suppression, advancing the fabrication of high-quality, high Sn-content relaxed GeSn using molecular beam epitaxy.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). μ-ATOMS; Univ. of Arkansas, Fayetteville, AR (United States)
• Sponsoring Organization: Office of Naval Research; USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0023412
• OSTI ID: 3376577
• Journal Information: Crystal Growth and Design, Journal Name: Crystal Growth and Design Journal Issue: 13 Vol. 26; ISSN 1528-7505; ISSN 1528-7483
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English