Direct Band Gap Germanium Microdisks Obtained with Silicon Nitride Stressor Layers
2016; American Chemical Society; Volume: 3; Issue: 3 Linguagem: Inglês
10.1021/acsphotonics.5b00632
ISSN2330-4022
AutoresM. El Kurdi, Mathias Prost, A. Ghrib, S. Sauvage, Xavier Chécoury, G. Beaudoin, I. Sagnes, Gennaro Picardi, Razvigor Ossikovski, P. Boucaud,
Tópico(s)Semiconductor Quantum Structures and Devices
ResumoGermanium 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.
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