Fig. 1. (a) Cross-sectional transmission electron microscopy (TEM) image of the Ge0.91Sn0.09/Ge MQW structure grown on the Si substrate with a Ge cap layer; the inset below is the selected-area diffraction pattern of the Ge0.91Sn0.09 well layer; the inset above shows EDX linear scanning of elemental contents in the GeSn/Ge quantum well structure. The red and blue lines represent Sn and Ge concentrations, respectively. (b) HR-TEM image of the Ge0.91Sn0.09/Ge QW interface. (c) XRD-RSM from the (−2–24) plane of the MQW structure.

Fig. 2. (a) Schematic of horizontal GeSn/Ge MQW p−i−n ridge waveguide LEDs on a Si (100) substrate. (b) Cross-sectional schematic of this horizontal device. (c) Scanning electron microscope (SEM) image of the ridge waveguide LEDs device. (d) Typical I-V characteristics of the device; inset: the relationship between ln I and V and the fitted curve of ideal factor η.

Fig. 3. (a) EL spectra of horizontal Ge0.91Sn0.09/Ge MQW p−i−n ridge waveguide LEDs at room temperature with different power density. (b) EL spectral peak wavelength as a function of power density. (c) PL spectrum of the as-grown sample and the EL spectrum of the device.

Fig. 4. (a) Band diagram for one period of the Ge0.91Sn0.09/Ge quantum well by theoretical calculation. (b) Temperature-dependent PL spectra of the as-grown sample at the temperature range 80 K to 290 K.

Fig. 5. Output power of this device plotted as a function of J at room temperature.