Optical Transitions in Direct-Bandgap Ge1鈥搙Snx Alloys

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• 作者：D. Stange ; S. Wirths ; N. von den Driesch ; G. Mussler ; T. Stoica ; Z. Ikonic ; J. M. Hartmann ; S. Mantl ; D. Gr眉tzmacher ; D. Buca
• 刊名：ACS Photonics
• 出版年：2015
• 出版时间：November 18, 2015
• 年：2015
• 卷：2
• 期：11
• 页码：1539-1545
• 全文大小：576K
• ISSN：2330-4022

文摘

A comprehensive study of optical transitions in direct-bandgap Ge_0.875Sn_0.125 group IV alloys via photoluminescence measurements as a function of temperature, compressive strain and excitation power is performed. The analysis of the integrated emission intensities reveals a strain-dependent indirect-to-direct bandgap transition, in good agreement with band structure calculations based on the 8-band k路p and deformation potential methods. We have observed and quantified 螕 valley鈥揾eavy hole and 螕 valley鈥搇ight hole transitions at low pumping power and low temperatures in order to verify the splitting of the valence band due to strain. We will demonstrate that the intensity evolution of these transitions supports the conclusion about the fundamental direct bandgap in compressively strained GeSn alloys. The presented investigation, thus, demonstrates that direct-bandgap group IV alloys can be directly grown on Ge-buffered Si(001) substrates despite their residual compressive strain.