Abstract
Secondary-ion mass spectroscopy, energy dispersion spectrometry, and Raman spectroscopy reveal that SiGe dots grown by ultrahigh-vacuum chemical vapor deposition at 600°C exhibit significant intermixing with an average Ge composition of ∼50%. Raman spectroscopy shows the top SiGe quantum dots of the 20-layer sample to be more relaxed than those of the 5-layer samples. As a result, the electroluminescence from the top SiGe quantum dots of the 20-layer sample has the higher peak energy at ∼0.84eV as compared to ∼0.82eV for the 5-layer sample. The external tensile mechanical strain can compensate the built-in compressive strain of SiGe quantum dots and increase electroluminescence energy.
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