Room-temperature electroluminescence at 1.3 and 1.5 μm from Ge/Si quantum-dot light-emitting diodes is reported. The devices were fabricated in a mesa-type structure, with a silicon oxide layer on the top for surface/sidewall passivation. Different passivation processes were employed. We found that the integrated electroluminescence intensities were relatively less sensitive to temperature, persisting at nearly the same intensity up to RT. The fabricated device shows an internal quantum efficiency of about 0.015% at RT. The improved emission property is attributed to the reduced nonradiative recombination centers due to the surface passivation and thermal treatment.

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Electroreflectance spectroscopy was used to study the effect of InxGa1−xAs capping layer on InAs quantum dots grown by metalorganic chemical vapor deposition. The optical transitions of the quantum dots and the InxGa1−xAs capping layer were well resolved. The energy shifts in the InxGa1−xAs capping layer show a different trend as compared to a series of referent InxGa1−xAs quantum wells. These results support the concept of strain-driven alloy decomposition during the InxGa1−xAs layer overgrowth.

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