Stress Engineering With Silicon Nitride Stressors for Ge-on-Si Lasers

Side and top silicon nitride stressors were proposed and shown to be effective in reducing the threshold current I
_th
and in improving the wall-plug efficiency η
_wp
of Ge-on-Si lasers. Side stressors only turned out to be a more efficient way to increase η
_wp
than using the top and side stressors together. With the side stressors and geometry optimizations, a η
_wp
of 34.8% and an I
_th
of 36 mA (J
_th
of 27 kA/cm
²
) can be achieved with a defect limited carrier lifetime (τ
_p,n
) of 1 ns. With τ
_p,n
= 10 ns, an I th of 4 mA (J
_th
of 3 kA/cm
²
) and a η
_w
p of 43.8% can be achieved. These are tremendous improvements from the case with no stressors. These results give strong support to the Ge-on-Si laser technology and provide an effective way to improve the Ge laser performance.