多孔硅量子点的受激辐射:陷阱态的作用

Stimulated emission in porous silicon quantum dots:the role of trap states

经激光辐照和高温退火后能够在硅基上生成氧化多孔硅结构。用514nm的激光泵浦，观测到该多孔硅的受激辐射。当激励强度超过阈值时，在650～750nm区域有很强的受激发光峰。这些受激发光峰的半高宽小于0．5nm。激光辐照和高温退火后，在样品上能形成某些特殊的氧化结构。在傅里叶红外光谱分析中，显示有硅氧双键或硅氧桥键在硅表面形成。计算结果表明：当硅氧双键或硅氧桥键形成时，电子的陷阱态出现在纳晶硅的带隙中。价带顶和陷阱态之间的粒子数反转是解释这种受激辐射的关键。

Stimulated emission has been observed from porous silicon formed by irradiation and annealing when optically excited by a 514 nm laser. When the excitation intensity exceeded a threshold, very sharp peaks emerged in the emission spectra from 650-750 nm. The full width at half maximum（FWHM） of the emission park with Lorentzian shape is less than 0.5 nm. The sample has a special oxide structure which was fabricated by laser irradiation and annealing treatment on silicon. In the Fourier transform infrared spectroscopy（FTIR）, some peaks emerge due to Si= O bonds and Si--O--Si bonds in the oxidation porous structure. Calculation shows that trap electronic states appear in the band gap of the smaller nanocrystal when double bonds or bridge bonds are formed between silicon and oxygen. The stimulated emission could be explained by population inversion between the top of the valence band and the trap＇ states.