Germanium under High Tensile Stress: Nonlinear Dependence of Direct Band Gap vs Strain
Germanium under High Tensile Stress: Nonlinear Dependence of Direct Band Gap vs Strain
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DOI：
10.1021/acsphotonics.6b00429
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发表时间：
2016-10-01
期刊：
影响因子：
7
通讯作者：
Calvo, Vincent
中科院分区：
文献类型：
--
作者：
Guilloy, Kevin;Pauc, Nicolas;Calvo, Vincent
锗是作为硅光子学的激光源的强有力的候选者。人们普遍认为，锗的能带结构可以通过拉伸应变来改变，从而减小其直接带隙和间接带隙之间的能量差。然而，最广泛采用的传统间隙变形势模型来描述这种转变恰好已经调查了只有1%的单轴加载应变。在这项工作中，我们使用微桥的几何形状，单轴应力锗沿着[100]高达100（100）= 3.3%的纵向应变，然后进行电吸收光谱。我们准确地测量在伽马点的导带和轻，重空穴价带之间的能隙，并计算使用紧束缚模型的理论依赖性。我们测量了锗的流体静力学和四阶剪切变形势为a = -9.1 +/- 0.3 eV和B = -2.32 +/- 0.06 eV，并引入了一个二阶变形势，它提供了更好的实验和理论关系。这些新的高应变系数将适用于未来CMOS兼容激光器和基于高应变锗的光电器件的设计。
Germanium is a strong candidate as a laser source for silicon photonics. It is widely accepted that the band structure of germanium can be altered by tensile strain so as to reduce the energy difference between its direct and indirect band gaps. However, the conventional gap deformation potential model most widely adopted to describe this transition happens to have been investigated only up to 1% uniaxially loaded strains. In this work, we use a microbridge geometry to uniaxially stress germanium along [100] up to epsilon(100) = 3.3% longitudinal strain and then perform electroabsorption spectroscopy. We accurately measure the energy gap between the conduction band at the Gamma point and the light- and heavy-hole valence bands and calculate the theoretical dependency using a tight-binding model. We measure the hydrostatic and tetragonal shear deformation potential of germanium to be a = -9.1 +/- 0.3 eV and b = -2.32 +/- 0.06 eV and introduce a second-order deformation potential that provides a better fit for both experimental and theoretical relations. These new high-strain coefficients will be suitable for the design of future CMOS-compatible lasers and optoelectronic devices based on highly strained germanium.