John Kouvetakis

TL;DR: In this article, the basic properties of the GeSiSn alloy were reviewed and some new results on its optical properties were presented, and the approach that has been followed to model heterostructures containing geSiSn layers for applications in modulators, quantum cascade lasers, and photovoltaics.

Abstract: Photoluminescence spectroscopy has been used to determine the direct gap E0 of Ge1−ySny alloys over a broad compositional range from pure Ge to Sn concentrations exceeding 10%. A fit of the compositional dependence of E0 using a standard quadratic expression is not fully satisfactory, revealing that the bowing parameter (quadratic coefficient) b0 is compositionally dependent. Excellent agreement with the data is obtained with b0(y) = (2.66 ± 0.09) eV − (5.4 ± 1.1)y eV. A theoretical model of the bowing is presented, which explains the strong compositional dependence of the bowing parameter and suggest a similar behavior for the indirect gap. Combining the model predictions with experimental data for samples with y ≤ 0.06, it is proposed that the bowing parameter for the indirect gap is bind(y) = (1.11 ± 0.07) eV − (0.78 ± 0.05)y eV. The compositional dependence of the bowing parameters shifts the crossover concentration from indirect to direct gap behavior to yc = 0.087, significantly higher than the valu...

TL;DR: The tetrameric gallane [HClGaN3]4 (1) as mentioned in this paper is an example of a gallane with an eight-membered Ga4N4 rings with Ga atoms bridged by α-nitrogens of the azide groups.

TL;DR: In this article, the authors obtained supersaturated metastable compositions (y∼25%) near the indirect to direct band gap crossover predicted by first principles simulations, and extensive characterizations of composition, structure, and morphology show that the SiSn∕GeSn films grow lattice matched via a "compositional pinning" mechanism.

TL;DR: Crucial advantages of this new and potentially practical CVD method are the significant vapor pressure of the precursor that permits rapid mass transport at 22 degrees C and the facile decomposition pathway that allows film growth at temperatures as low as 200 degrees C with considerable growth rates up to 800 Å/min.