Electroluminescence characteristics of LED with Si/SiGe multiple quantum well under different doping conditions

In this thesis we demonstrated 1.3~1.4μm wavelength light emission from 10-period Si/Si0.85Ge0.15 quantum-well (QW) structures. There are two different samples in our investigation: p-i-n and p-p-n structures, grown by UHVCVD system. For the p-i-n sample, the QW structure is in the depletion region of diode, while for the p-p-n sample it is in the electron diffusion region of diode.
According to our experiment results, the luminescence of QW dominates and the luminescence of Si is only observed at high bias for p-i-n sample at low temperature. However, the luminescence intensity of QW decreases with temperature because the carriers get more energy to escape the well. For p-p-n sample, the luminescence intensity of Si is enhanced because of the high p-type doping in the Si buffer layer, which causes lots of electron-hole recombination.
At room temperature, the efficiency is low for both samples. At low temperature, the efficiency of the p-p-n sample is higher than that of the p-i-n sample. The high hole-concentration in the electron diffusion region (p-type region) may enhance the recombination rate. We also discussed the temperature dependence of the QW luminescence and the activation energy of holes in the well. The activation energy decreases as the current injection increases. The difference in activation energy between these two samples is about 23meV at the same injection condition.