氧化硅层中的锗纳米晶体团簇量子点

采用氧化和析出的方法在氧化硅中凝聚生成锗纳米晶体量子点结构. 其形成的锗晶体团簇没有突出的棱角和支晶结构，锗晶体团簇的轮廓较圆混，故可以用球形量子点模型来模拟实际的锗晶体团簇. 对比了在长时间退火氧化条件下和在短时间退火用激光照射氧化条件下所生成的锗纳米晶体结构的PL光谱和对应的锗纳米晶体团簇的尺寸分布. 短时间退火氧化条件下生成的锗纳米晶体较小(3.28—3.96nm)，长时间退火用激光照射氧化条件下所生成的锗纳米晶体较大(3.72—4.98nm)；其分布结构显示某些尺寸的锗纳米晶体团簇较稳定，适当的氧化条件可以得到尺寸分布范围较窄的锗纳米晶体团簇. 用量子点受限模型计算了锗纳米晶体团簇的能隙结构，用Monte Carlo方法模拟了PL光谱和对应的锗纳米晶体团簇的尺寸分布，分别与实验结果符合较好. 关键词： 锗晶体团簇 纳米晶体 量子点 激光照射

Germanium quantum dots formed by oxidation of SiGe alloys

We report the investigation on the oxidation behavior of Si_1-xGe_x alloys (x=0.05, 0.15, and 0.25). In the PL spectra of Germanium quantum dots formed by the oxidation of Si_1-xGe_x substrate, at high oxidation temperature (800℃—1000℃) an emission band from 550nm to 720nm would originate from the diameter distribution of germanium nanoparticles (Ge clusters diameter: 3nm—4nm); and at low oxidation temperature (400℃—600℃) with Laser beam radiation, there is an emission band from 650nm to 900nm which may have come from the germanium clusters (diameter: 4nm—5nm). It is clearly seen that there are several peaks at 572nm, 620nm, 671nm, 724nm, 769nm, 810nm and 861nm wavelengths along the emission band, which are correlated to the quantum confinement effect with 3.32nm, 3.54nm, 3.76nm, 3.98nm, 4.17nm, 4.35nm and 4.62nm diameters of the germanium clusters, respectively. The simulation result with MC method demonstrates that the germanium clusters of the above diameters are more stable under the above conditions. A quantum confinement model has been set up, and calculations with the UHFR method and the quantum confinement analysis have been proposed to explain the PL spectra.