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

通过控制低压化学气相沉积（LPCVD）工艺，采用纯SiH_4和/或Si_2H_6，用He稀释的5%GeH_4进行选择性LPCVD，对量子点进行热氧化，然后对Ge氧化物进行热脱附，成功地在SiO_2衬底上制备了自对准的Si基量子点（Si-QD）。在具有如此制备的自对准点的半透明金栅二极管中，当载流子从n-Si（100）衬底注入到自对准Si-QD中用于电子和从Au顶部电极注入到自对准Si-QD中用于空穴时，在室温下近红外区域中的电致发光（EL）变得可观察到，并且在正偏压下电流增加超过低至约1的阈值电压。在Au顶部电极处为2 V。注意，在面点密度为约10 μ cm-3的情况<13>下<-2>，EL阈值电压降低到约10 μ cm-3的阈值电压的约60%<11>，<-2>并且在相同电流密度下与约10 μ cm-3的情况相比，发射强度显著增强约425<11><-2>倍。这清楚地证明了不仅自对准结构中的辐射复合率增加，而且由于随着点密度增加电流泄漏减少而提高了复合效率。

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.