Electrically Injected GeSn Vertical-Cavity Surface Emitters on Silicon-on-Insulator Platforms

An efficient electrically injected group-IV light source compatible with the complementary metal-oxide-semiconductor (CMOS) process is the holy grail for realizing functional, intelligent electronic-photonic integrated circuits for a wide range of applications. The group-IV GeSn material is considered as a promising solution for efficient light sources because its bandgap can be fundamentally transformed from indirect to direct with appropriate Sn compositions. However, an important challenge in realizing efficient electrically injected light emitters is the incorporation of an optical cavity with electrical structures. Here we demonstrate, to the best of our knowledge, the first electrically injected GeSn vertical-cavity surface emitter on the silicon-on-insulator platform. A vertical cavity employing a buried oxide layer and a deposited SiO 2 top layer as reflectors is developed for enhancing the electroluminescence in the GeSn active layer. Room-temperature electroluminescence experiments reveal clear cavity-resonant modes with adequate vertical-cavity Q -factor and greatly enhanced electroluminescence. Most importantly, under electrical injection, considerably reduced optical loss in the GeSn optical cavity was found at room temperature, toward achieving electrically injected optical gain. In addition, theoretical models for evaluating the optical gain and loss are presented for estimating net optical gain. These results on our GeSn vertical-cavity surface emitter pave the way toward efficient, continuous-wave electrically injected GeSn lasers operating at room temperature for electronic–photonic integrated circuits.