Direct Band Gap Germanium Microdisks Obtained with Silicon Nitride Stressor Layers

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• 作者：Moustafa El Kurdi ; Mathias Prost ; Abdelhamid Ghrib ; Sébastien Sauvage ; Xavier Checoury ; Grégoire Beaudoin ; Isabelle Sagnes ; Gennaro Picardi ; Razvigor Ossikovski ; Philippe Boucaud
• 刊名：ACS Photonics
• 出版年：2016
• 出版时间：March 16, 2016
• 年：2016
• 卷：3
• 期：3
• 页码：443-448
• 全文大小：446K
• ISSN：2330-4022

文摘

Germanium is an ideal candidate to achieve a monolithically integrated laser source on silicon. Unfortunately bulk germanium is an indirect band gap semiconductor. Here, we demonstrate that a thick germanium layer can be transformed from an indirect into a direct band gap semiconductor by using silicon nitride stressor layers. We achieve 1.75% (1.67%) biaxial tensile strain in 6 (9) μm diameter microdisks as measured from photoluminescence. The modeling of the photoluminescence amplitude vs temperature indicates that the zone-center Γ valley has the same energy as the L valley for a 9 μm diameter strained microdisk and is even less for the 6 μm diameter microdisk, thus demonstrating that a direct band gap is indeed obtained. We deduce that the crossover in germanium from indirect to direct gap occurs for a 1.67% ± 0.05% biaxial strain at room temperature, the value of this parameter varying between 1.55% and 2% in the literature.