Control of Electronic Properties of One-Dimensionally Self-Aligned Si-Ge based Quantum Dots and Its Electroluminescence

用纯SiH_4和/或Si_2H_6控制低压化学气相沉积（LPCVD），用He稀释5%的GeH_4选择性地制备Ge LPCVD，热氧化和氧化Ge热脱附，成功地在超薄SiO_2上制备了自对准硅基量子点（Si-QDs）。当从n-Si（100）衬底注入载流子作为电子，从Au顶部电极注入载流子作为空穴时，在室温下近红外区域的电致发光（EL）随着正偏置电流的增加而增加，阈值电压低至~ 1。在Au顶电极上2v。值得注意的是，在面点密度为~10^<13> cm^<-2>的情况下，EL阈值电压降低到~10^<11> cm^<-2>的约60%，在相同电流密度下，与~10^<11> cm^<-2>的情况相比，发射强度显著提高了约425倍。这清楚地证明了自对准结构的辐射复合率增加，而且由于随着点密度的增加电流泄漏减少，复合效率也有所提高。

Self-aligned Si-based quantum dots(Si-QDs) have been successfully fabricated on ultrathin SiO_2 by controlling low-pressure chemical vapor deposition(LPCVD) using pure SiH_4 and/or Si_2H_6, selective Ge LPCVD from 5% GeH_4 diluted with He, thermal oxidation of the dots and subsequent thermal desorption of Ge oxide. 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 ~10^<13> cm^<-2>, the EL threshold voltage was reduced down to~ 60% of that of ~10^<11> cm^<-2> and emission intensity was enhanced markedly by a factor of ~425 in comparison with the case of ~10^<11> 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.