  Silicon-compatible short- and mid-wave infrared emitters are highly
sought-after for on-chip monolithic integration of electronic and photonic
circuits to serve a myriad of applications in sensing and communication. To
address this longstanding challenge, GeSn semiconductors have been proposed as
versatile building blocks for silicon-integrated optoelectronic devices. In
this regard, this work demonstrates light-emitting diodes (LEDs) consisting of
a vertical PIN double heterostructure
p-Ge$_{0.94}$Sn$_{0.06}$/i-Ge$_{0.91}$Sn$_{0.09}$/n-Ge$_{0.95}$Sn$_{0.05}$
grown epitaxially on a silicon wafer using germanium interlayer and multiple
GeSn buffer layers. The emission from these GeSn LEDs at variable diameters in
the 40-120 $\mu$m range is investigated under both DC and AC operation modes.
The fabricated LEDs exhibit a room temperature emission in the extended
short-wave range centered around 2.5 $\mu$m under an injected current density
as low as 45 A/cm$^2$. By comparing the photoluminescence and
electroluminescence signals, it is demonstrated that the LED emission
wavelength is not affected by the device fabrication process or heating during
the LED operation. Moreover, the measured optical power was found to increase
monotonically as the duty cycle increases indicating that the DC operation
yields the highest achievable optical power. The LED emission profile and
bandwidth are also presented and discussed.
