Stress engineering with silicon nitride stressors for Ge-on-Si lasers

TL;DR

This paper demonstrates that silicon nitride stressors, especially side stressors, significantly enhance Ge-on-Si laser performance by reducing threshold current and increasing efficiency, with optimized geometries and defect-limited carrier lifetimes.

Contribution

It introduces the use of silicon nitride stressors for Ge-on-Si lasers and shows their effectiveness in performance improvement through geometry optimization.

Findings

Side stressors outperform top and side combinations in efficiency.

Achieved wall-plug efficiency of 30.5% with 50 mA threshold current.

Significant improvements in laser performance with optimized stressors and carrier lifetimes.

Abstract

Side and top silicon nitride stressors were proposed and shown to be effective ways to reduce the threshold current Ith and improve the wall-plug efficiency {\eta}wp of Ge-on-Si lasers. Side stressors only turned out to be a more efficient way to increase {\eta}wp than using top and side stressors together. With the side stressors only and geometry optimizations, a {\eta}wp of 30.5% and an Ith of 50 mA (Jth of 37 kA/cm2) can be achieved with the defect limited carrier lifetime of 1 nsec. With the defect limited carrier lifetime of 10 nsec, an Ith of 7.8 mA (Jth of 5.8 kA/cm2) and a wall-plug efficiency of 38.7% can be achieved. These are tremendous improvements from the case without any stressors. These results give strong support to the Ge-on-Si laser technology and provide an effective way to improve the Ge laser performance.