Effect of Ge Core Size on Photoluminescence from Si Quantum Dots with Ge Core

Abstract

Si quantum dots (Si-QDs) with Ge core were self-assembled on thermally grown SiO2 from alternate thermal decomposition of pure SiH4 and GeH4 diluted with H2. When the sample was excited by a 979 nm line of semiconductor laser at room temperature, photoluminescence (PL) spectra peaked at 0.6-0.75 eV were observed. It is interesting noted that, with decreasing the Ge core size, the PL signals were shifted towered the higher energy side reflecting quantum size effect. We also found that surface passivation of selectively-grown Ge on pre-grown Si-QDs by the formation of Si clad, namely formation of core/shell structures, can enhance the light emission from the Ge core.