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 SiO2 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.