论文标题
超低阈值CW和拉伸紧张的GESN合金中的脉冲激光
Ultra-low threshold cw and pulsed lasing in tensile strained GeSn alloys
论文作者
论文摘要
GESN合金完全基于IV组元素，是光发射器的最有希望的半导体。包含超过8个sn的合金具有基本的直接带隙，类似于传统的III-V半导体，因此可以用于发光设备。在这里，我们报告了用Sinx应激层封装的GESN微型遇险激光器，以产生拉伸应变。 300nm的GESN层具有5.4 at。％SN，这是一种间接的带隙半导体，其压缩应变为-0.32％，通过拉伸应变工程转换为真正的直接带隙半导体。在这种方法中，低SN浓度可以改善缺陷工程，而拉伸应变在Valence Band Edge处提供低密度的状态，即轻孔带。在非常低的光泵功率下观察到连续波（CW）以及脉冲激光。 NS脉冲激发的发射波长为2.5 UM的激光器的阈值低至0.8kWcm^-2 -2，在CW激发下，阈值和1.1kWcm^-2。这些阈值比先前报道的大量GESN激光器低两个以上的数量级，接近SI上IIII-V激光器获得的这些值。目前的结果证明了弱势群体，并且是Si Photonics平台上单层集成的基于SI的激光源的指南。
GeSn alloys are the most promising semiconductors for light emitters entirely based on group IV elements. Alloys containing more than 8 at.% Sn have fundamental direct band-gaps, similar to conventional III-V semiconductors and thus can be employed for light emitting devices. Here, we report on GeSn microdisk lasers encapsulated with a SiNx stressor layer to produce tensile strain. A 300nm GeSn layer with 5.4 at.% Sn, which is an indirect band-gap semiconductor as-grown with a compressive strain of -0.32 %, is transformed via tensile strain engineering into a truly direct band-gap semiconductor. In this approach the low Sn concentration enables improved defect engineering and the tensile strain delivers a low density of states at the valence band edge, which is the light hole band. Continuous wave (cw) as well as pulsed lasing are observed at very low optical pump powers. Lasers with emission wavelength of 2.5 um have thresholds as low as 0.8kWcm^-2 for ns-pulsed excitation, and 1.1kWcm^-2 under cw excitation. These thresholds are more than two orders of magnitude lower than those previously reported for bulk GeSn lasers, approaching these values obtained for III-V lasers on Si. The present results demonstrate the feasabiliy and are the guideline for monolithically integrated Si-based laser sources on Si photonics platform.
