Enhanced GeSn Microdisk Lasers Directly Released on Si

TL;DR

This paper demonstrates strain-free GeSn microdisk lasers directly on silicon, achieving better optical confinement and thermal management, leading to higher operation temperatures and lower lasing thresholds compared to suspended devices.

Contribution

It introduces a novel strain-free GeSn microdisk laser fabrication on Si that enhances optical and thermal performance over traditional suspended structures.

Findings

Improved optical confinement in strain-free GeSn cavities on Si.

Significant reduction in device temperature increase during operation.

Increased operation temperature by ~40 K and 30% lower lasing threshold.

Abstract

GeSn alloys are promising candidates for complementary metal-oxide-semiconductor (CMOS)-compatible, tunable lasers. Relaxation of residual compressive strain in epitaxial GeSn has recently shown promise in improving the lasing performance. However, the suspended device configuration that has thus far been introduced to relax the strain is destined to limit heat dissipation, thus hindering the device performance. Herein, we demonstrate that strain-free GeSn microdisk laser devices fully released on Si outperform the canonical suspended devices. This approach allows to simultaneously relax the limiting compressive strain while offering excellent thermal conduction. Optical simulations confirm that, despite a relatively small refractive index contrast between GeSn and Si, optical confinement in strain-free GeSn optical cavities on Si is superior to that in conventional strain-free GeSn cavities suspended in the air. Moreover, thermal simulations indicate a negligible temperature increase in our device. Conversely, the temperature in the suspended devices increases substantially reaching, for instance, 120 K at a base temperature of 75 K under the employed optical pumping conditions. Such improvements enable increasing the operation temperature by ~40 K and reducing the lasing threshold by 30%. This approach lays the groundwork to implement new designs in the quest for room temperature GeSn lasers on Si.