We calculate the electronic structures of Ge nanowires at the direct Γ-valley and indirect L-valley under the [100] direction uniaxial stress perpendicular to the nanowire axis using the effective-mass k.p theory, and the results demonstrate the stress along the [100] direction is effective to transform Ge nanowires from the indirect-band-gap to direct-band-gap semiconductor. Moreover, the optical gain and net peak gain under the [100] direction stress are also investigated, and it is interesting that the pure optical gain along the z direction can almost be obtained. Importantly, we find that the photon energy around 0.8 eV corresponding to the gain peak can be realized in Ge nanowires under an appropriate [100] direction stress when the diameter is in the range of 10∼20 nm, which means Ge nanowires can be engineered to be suitable for the telecom wavelength 1550 nm in the field of Si photonics via the [100] direction stress.

我们使用有效质量kp理论计算了在垂直于纳米线轴的 [100] 方向单轴应力下直接 Γ 谷和间接L谷的 Ge 纳米线的电子结构，结果表明沿 [100 ]方向有效地将Ge纳米线从间接带隙半导体转变为直接带隙半导体。此外，还研究了 [100] 方向应力下的光学增益和净峰值增益，有趣的是，沿z方向的纯光学增益几乎可以得到方向。重要的是，我们发现当直径在 10~20 nm 范围内时，Ge 纳米线可以在适当的 [100] 方向应力下实现与增益峰值对应的 0.8 eV 左右的光子能量，这意味着可以设计 Ge 纳米线通过[100]方向应力适用于Si光子学领域的电​​信波长1550nm。