Electroluminescence from Silicon and Germanium Nanostructures
Silicon (Si) and germanium (Ge) have an indirect band gap transitions; however when they are miniaturized to nanometer scale, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) increases, and hence the transition changes to direct due to confinement. In this paper we explain photoluminescence (PL) and electroluminescence (EL) and formulate models to study electroluminescence from Si and Ge nanostructures. Using the models we got computational results to explain the dependence of EL on different parameters like size of the nanocluster, applied voltage, band gap energy, and wavelength for pure silicon nanocrystal (Si-nc) and for oxygen and hydrogen terminated Si-nc. The EL and PL intensities occurs at the same energy; however, the EL intensity has sharp Gaussian sub peaks and red shifted compared to the PL intensity. To get our result, we used the idea of quantum confinement model (QCM), that can explain PL and EL on pure Si nanostructures and Si-terminated with impurities.
Keywords: Quantum confinement, Nanostructure, Exciton binding energy, Electroluminescence