A simulation study of photoluminescence silicon nanowires

Abstract

The need for the integration of silicon (Si) nanostructures (NS) in optical devices has led to the search for silicon based materials and structures that emit lights with high quantum efficiency. Since after the observation of room temperature visible photoluminescence (PL) from silicon nanostructures (Quantum dot or wire) and the feasibility of turning the optical response of Si NS by modifying their size, many experimental and theoretical works have been done to explain the origin of the visible photoluminescence mechanism. However, the mechanism of visible luminescence remains unclear despite the efforts. Lately, Si nanostructure with hydrogen and oxygen passivated surface become attractive due to enhanced light emission. the purpose of this research is to develop a hybrid model of quantum confinement effect (QCE), surface state effects (SSE) and exciton energy state (EES) to study PL spectra of Si nanowire using data obtained from experimental and simulation (pseudo-potential approximation and tight binding method) findings. A simple, linear simulation method (matlab codes) is used to examine the optical responses of Si NWs with diameter between 1.5 and 5.8nm. An integrated photoluminescence intensity model is adopted to generate PL spectra. The results of this work indicate that both QCE and surface passivation together with exciton effects determine the optoelectronic properties of Si NWs. We demonstrate that by controlling a set of parameters extracted by fitting the model with experiment and simulation, it is possible to interpret the PL spectral features. The band gap is found to decrease with the increase of NWs diameter and increases more with decreasing oxygenated surface than hydrogenated surface. The finding results are compared with other model calculations and experimental works. The admirable features of the results suggest that the present model is significant for understanding the mechanism of visible PL from Si NWs. The model can be extended for other nanostructures of different shapes and size.