Microscopic and Macroscopic Bipolar Injection and Carrier Recombination in Single-layer Si Nanocrystals

Abstract

Si nanocrystals (NCs) based optoelectronic devices have attracted more and more attentions due to the quasi-direct energy band structure and the adjustable band gap of Si NCs. In these optoelectronic devices, the carrier injection and recombination process is a crucial issue and needs to be deeply understood. Here, bipolar carrier injection and recombination process in a single layer of Si NCs was observed at the microscopic and macroscopic scales, by electrostatic force microscopy (EFM) and alternating-current electroluminescence (ac EL) measurement, respectively. EFM result showed that opposite charges could be injected into the single-layer Si NCs and they would laterally recombine with each other. On the other hand, the single-layer Si NCs also showed a frequency dependent EL intensity, which was attributed to the time limitation of carrier injection and radiative recombination process.