Electroluminescence from One-Dimensionally Self-Aligned Si-Based Quantum Dots with High Areal Dot Density

Abstract

Self-aligned Si-based quantum dots (QDs) with an areal density as high as ∼1013 cm-2 have been successfully fabricated on GeH4-adsorbed ultrathin SiO2 by the process sequence consisting of Si-QDs formation by controlling low-pressure chemical vapor deposition (LPCVD) using pure Si2H6, selective Ge-LPCVD from 5% GeH4 diluted with He, thermal oxidation of the dots, thermal desorption of Ge oxide, and subsequent formation of the Si-QDs. In semitransparent Au-gate diodes with self-aligned dots so-prepared, when carriers were injected to the self-aligned Si-QDs from the n-Si(100) substrate for electrons and from the Au top electrode for holes, electroluminescence (EL) in the near-infrared region at room temperature becomes observable with an increase in current at positive biases over a threshold voltage as low as ∼1.2 V at the Au top electrode. Note that, in the case of an areal dot density of ∼1013 cm-2, the EL threshold voltage was reduced down to ∼60% of that of ∼1011 cm-2 and emission intensity was enhanced markedly by a factor of ∼425 in comparison with the case of ∼1011 cm-2 under the same current density. This is clear evidence of not only an increase in radiative recombination rate in the self-aligned structure but also an improvement of recombination efficiency due to a decrease in current leakage with increasing dot density.