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

通过控制纯SiH4和/或Si2H6的低压化学气相沉积(LPCVD)，用5%的GeH4和He稀释的选择性Ge LPCVD，点的热氧化和Ge氧化物的热脱附，在超薄的SiO_2上成功地制备了自对准的硅基量子点(Si-QD)。在这种自对准的半透明自对准金栅二极管中，当载流子从n-Si(100)衬底注入自对准的硅量子点时，当载流子从金顶电极注入电子和从金顶电极注入空穴时，可以观察到室温下近红外区的电致发光(EL)，在Au顶电极的正偏压下电流增加到低至~1.2V的阈值电压。注意，在面上点密度为~10^lt；13；cm；-2的情况下，在相同电流密度下，EL阈值电压降低到~10^；lt；11；cm；-2&gt；的~60%，发射强度显著增强约425倍。这不仅是自对准结构中辐射复合速率增加的明显证据，而且由于电流泄漏随着点密度的增加而减少，复合效率也因此而提高。

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.