飞秒激光制备掺杂黑硅及其光电特性的研究

发布时间：2018-10-12 14:07

【摘要】：硅具有资源丰富、耐高温、易与现有集成电路技术兼容的优点,在半导体行业中具有广泛的应用。但是,硅的禁带宽度为1.12eV,因此对波长长于1100nm的入射光基本无光电响应。这一固有性质限制其在近红外领域的应用。硫族元素超饱和掺杂黑硅突破了这一限制,在可见—近红外波段均具有高吸收的特性。因此,硫族元素掺杂黑硅在近红外探测和光电池等领域具有巨大的应用前景。本文利用飞秒激光辐照具有杂质膜层的硅表面,制备了硒超饱和掺杂黑硅。系统研究了脉冲数目、硒膜厚度对黑硅的表面形貌、光学、电学特性的影响。并基于掺杂黑硅制备n+-n光电探测器,分析探测器的暗电流特性与光电响应特性。研究发现,制备的硒掺杂黑硅在400～2200nm波段吸收率达到90%以上,远高于晶体硅的吸收率。分析认为,在400～1100nm波段,吸收率的提高是由于表面微结构的多次反射作用;在1100～2200nm波段,吸收率的提高是由于表面微结构、表面缺陷与硒元素超饱和掺杂的共同作用。硒掺杂黑硅的表面结构尺寸、吸收率、表面载流子密度均随脉冲数目的增大而升高,但载流子迁移率却随之降低。基于硒掺杂黑硅制备的探测器响应度随脉冲数目增大而提高,脉冲数目为250时响应度最高,在1064nm处达到0.889A/W。当脉冲数目进一步增大至500时,响应度反而降低。分析认为,响应度受到表面吸收率与微结构尺寸的共同影响。脉冲数目过大时,尽管吸收率升高,但表面结构尺寸增大,载流子迁移率过低,大量光生载流子未能成功渡越两极参与导电,因此响应度反而降低。基于以上研究结果,恒定脉冲数目为250,研究不同硒膜厚度对硒掺黑硅及其器件性能的影响。研究发现,硒掺杂黑硅的表面结构尺寸、吸收率、表面载流子密度均随硒膜增大而升高,但载流子迁移率却随之降低。黑硅探测器在1064nm处光电响应度随硒膜厚度增大而增大,硒膜厚度125nm时制备的器件响应度最高。本文根据脉冲数目和硒膜厚度两个变量设计实验,分析材料的表面形貌、光学、电学及光电响应特性,优化实验参数,提高器件光电响应度。在脉冲数目250,硒膜厚度125nm时,制备出响应度最高的探测器,达到1.22A/W。
[Abstract]:Silicon is widely used in semiconductor industry because of its advantages of rich resources, high temperature resistance and compatibility with existing IC technology. However, the band gap of silicon is 1.12eV, so there is no photoelectric response to incident light with wavelength longer than 1100nm. This inherent property limits its application in the near infrared field. The sulfur element oversaturated doped black silicon overcomes this limitation and has high absorption in the visible-near infrared band. Therefore, sulfur doped black silicon has great application prospect in near infrared detection and photocell. Selenium supersaturated doped black silicon was prepared by femtosecond laser irradiation on the surface of silicon with impurity film. The effects of the number of pulses and the thickness of selenium film on the surface morphology, optical and electrical properties of black silicon were systematically studied. N-n photodetectors were prepared based on doped black silicon, and the dark current and photoelectric response characteristics of the detectors were analyzed. It is found that the absorptivity of selenium doped black silicon is over 90% in 400~2200nm band, which is much higher than that of crystal silicon. It is concluded that the increase of absorptivity in 400~1100nm band is due to the multiple reflection of surface microstructure, while in 1100~2200nm band, the increase of absorptivity is due to the interaction of surface microstructure, surface defects and selenium supersaturation doping. The surface structure size, absorptivity and surface carrier density of selenium-doped black silicon increase with the increase of the number of pulses, but the carrier mobility decreases. The responsivity of the detector based on selenium-doped black silicon increases with the increase of the number of pulses. When the number of pulses is 250, the responsivity is the highest, reaching 0.889 A / W at 1064nm. When the number of pulses increases to 500, the responsivity decreases. It is concluded that the responsivity is affected by both the surface absorptivity and the size of the microstructure. When the number of pulses is too large, the surface structure size increases, the carrier mobility is too low, and a large number of photogenerated carriers fail to successfully cross the poles to participate in the conduction, so the responsivity decreases. Based on the above results, the effects of different thickness of selenium film on the properties of selenium-doped black silicon and its devices were studied with constant pulse number of 250. It is found that the surface structure size, absorptivity and surface carrier density of Se-doped black silicon increase with the increase of selenium film, but the carrier mobility decreases. The photoelectric responsivity of the black silicon detector increases with the increase of the thickness of the selenium film at 1064nm, and the highest responsivity of the device is obtained when the thickness of the selenium film is 125nm. In this paper, experiments are designed according to the number of pulses and the thickness of selenium film. The surface morphology, optical, electrical and photoelectric response characteristics of the materials are analyzed, and the experimental parameters are optimized to improve the photoelectric responsivity of the devices. When the number of pulses is 250 and the thickness of selenium film is 125nm, a detector with the highest responsivity of 1.22A / W is prepared.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN249;TN304.1

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