SiO_2/Ge:SiO_2/SiO_2夹层结构红外光发射的起源

Origin of Infrared Photoluminescence from SiO_2/Ge: SiO_2/SiO_2 Sandwiched Structure

我们借助傅立叶变换红外光谱（ＦＴ－ＩＲ）以及光致激发谱（ＰＬＥ），研究了 ＳｉＯ_２／Ｇｅ：ＳｉＯ_２／ＳｉＯ_２夹层结构红外光发射的起源。谱分析表明，该红外光发射并非起源于纳米锗、硅的量子限制效应以及锗、硅的中性氧空位，而与锗的氧化物紧密相关。ＰＬＥ的结果证实它们来源于ＧｅＯ色心ＴⅡ’→Ｓ０的光学跃迁，给出的ＧｅＯ电子态模型描述了载流子激发和复合的过程。

Enhanced 395nm ultraviolet photoluminescence (PL) has been obtained from the SiO2/Ge SiO2/ SiO2 sandwiched structure. As light source for optical data storage system, this structure will be very useful in optoelectronic integration. Simultaneously, infrared light emission peaked at 780nm was also observed in this novel structure. In this paper, we discussed the origin of the infrared PL in terms of infrared spec- troscopy (FT-IR) and FL excitation (PLE) spectra. The constancy of the 780nm PL band with annealing temperature does suggest that it can not arise from both the quantum confinement on Ge, Si nanocrystals and the oxygen deficient defects of Ge and Si, because PL from these radiative centers all have peak shifts to some extent. The experimental results from FT-IR strongly suggest that the Ge-O-Ge vibration intensity and the 780nm PL intensity have a similar behavior with annealing temperature. So it is reasonable to be- lieve that the infrared PL band is very related to Ge oxides. Further PLE examination results indicate that it has the similar excitation process to the 395nm ultraviolet PL which comes from TⅡ'(T)→S0 optical transitions in GeO color centers, which has been confirmed by many research groups. So we believe that the 780nm PL should also originate from GeO color centers. The schematic diagram of electronic states of GeO molecule is presented to describe the carriers' excitation and recombination process in this kind of centers. The TⅡ'→S0 optical transitions in GeO color center is responsible for the infrared PL. In GeO molecules, all radiative transitions are intramolecular. Thus the PL bands from the GeO color centers are hardly influ- enced by the SiO2 network. That is why 780nm infrared PL has no wavelength change with different annealing temperature. Our work paves the way for the sandwiched structure's device applications.