基于VIA族和IB族杂质深能级的硅亚带隙光谱响应机理研究

Silicon sub-bandgap spectral response has significant applications in integrated optical communications and night vision technology. It is found that ultrafast laser hyperdoping of VIA and IB group impurities into silicon can extend silicon response wavelength to 2200 nm. But, the physical mechanism behind the broad spectral response is still ambiguous up to now, and no valid evidence can explain this unique optoelectronic property. Evidently, sub-bandgap spectral response is caused by the absorption of low energy-photons and optical-to-electric conversion. However, the optical excitation and transition of low energy-photons in silicon bandgap is closely related to the impurity-introduced deep levels. So, in this item, the influence of ultrafast laser irradiation on the substitution, activation of VIA and IB group impurities in silicon, and on the properties of impurity-introduced deep levels will be investigated comprehensively by a combination of deep level transient spectroscopy method with photocurrent activation test technique under non equilibrium ion implantation doping. At last, the effects of impurity-introduced deep levels on the generation and recombination of photo carriers will be studied to illuminate the physical source of silicon near infrared spectral response broadened by the VIA and IB group impurities. Finally, the sub-bandgap spectral response model will be built based on theoretical physics to provide theoretical and technical guidance for the fabrication of novel silicon optoelectronic devices.

硅亚带隙光谱响应在集成光通信与夜视成像中具有重要的应用价值。研究发现，超快激光非平衡掺杂VIA族和IB族杂质，可将硅的光谱响应波长拓宽至2200 nm。但是，宽光谱响应背后的物理机制，至今仍处于猜测推究阶段，国际上尚无科学依据予以阐释。亚带隙光谱响应对应低能光子的吸收与光电转换。而杂质深能级与低能光子在硅能带中的激发跃迁紧密关联。基于此，该课题拟在非平衡离子注入掺杂下，借助深能级瞬态谱测试、光电流激活能测试等技术，深入剖析超快激光对VIA族和IB族深能级杂质的替位、激活以及对其深能级特性的物理修正作用。通过研究杂质深能级对光生载流子的激发复合过程，最终揭示VIA族和IB族杂质深能级拓宽硅近红外光谱响应的物理根源，并建立纯物理的亚带隙光电响应模型，为新型硅光电子器件的研发提供理论与技术指导。

本课题采用飞秒激光辐照在晶体硅表层掺杂硒、硫、金元素，开展了晶体硅表层特种光电材料特性和器件特性的探索研究，取得了良好的研究结果。其主要表现在：1）利用离子注入和飞秒激光辐照掺杂的方法，制备出表面平整的硫、硒元素重掺薄层，通过Hall、SIMS、ECV、背散射谱等测试分析，硫、硒杂质原子在晶体硅中的替位率约达到30%，激活率约达到10%，载流子浓度达到1x1017/cm3，达到半导体器件工作浓度。2）通过深能级瞬态谱测试分析，硒杂质在晶体硅中具有两处深能级，分别位于硅导带下0.34eV和0.525eV处，被认为是硒间隙杂质原子所产生。3）在上述基础上制备了掺硫、掺硒元素的硅pn结，其在980nm波长的量子效率超过300%，光电效应达到15A/W。另外，在硅中掺硒、硫、金都在1200至1600nm波段观察到红外响应特性，但这种红外的光电响应不高，主要是该红外响应与深能级有关。