Continuous-Wave GeSn Light-Emitting Diodes on Silicon with 2.5 μm Room-Temperature Emission

Silicon-compatible short- and midwave 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. Commercially available infrared light-emitting diodes (LEDs) are predominantly made of III–V materials, which are costly and not silicon-compatible. These materials suffer a degraded performance if the emitting wavelength is longer than 2.35 μm. To address this long-standing challenge, GeSn semiconductors have been proposed as versatile building blocks for silicon-integrated optoelectronic devices. In this regard, this work demonstrates LEDs consisting of a vertical PIN double heterostructure p-Ge0.94Sn0.06/i-Ge0.91Sn0.09/n-Ge0.95Sn0.05 grown epitaxially on a silicon wafer using a germanium interlayer and multiple GeSn buffer layers. The emission from these GeSn LEDs at variable diameters in the 40–120 μm range is investigated under both DC and AC operation modes. The fabricated LEDs exhibit room temperature emission in the extended short-wave range centered around 2.5 μm under an injected current density as low as 45 A/cm2. 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.