通过太赫兹光谱学测定半导体掺杂范围的可及性
Accessibility of doping ranges of semiconductors by terahertz spectroscopy
AI总结：
本文通过太赫兹光谱学研究半导体掺杂范围的可测性，提出灵敏度度量并建立热图，揭示了不同材料和厚度下掺杂范围的依赖关系。
摘要：
尽管已建立的半导体测量技术如四点探针或电容-电压测量需要与材料物理接触，太赫兹光谱学是完全无接触的。其测量半导体掺杂的能力已为人所知，但太赫兹光谱学确切可测的掺杂范围并不明显。因此，我们引入了一个灵敏度度量来明确是否可以通过反射太赫兹时域光谱学对半导体样品进行表征。该量值考虑了具有特定层厚、掺杂类型和掺杂水平的半导体材料，并基于数值模拟。在本工作中，我们计算了相关半导体材料（SiC、Si、GaN）在具有最多三层的现实层堆栈中的灵敏度值。它被用来根据感兴趣的样品结构的厚度和载流子密度创建有意义的热图。通过将各种使用太赫兹技术进行的测量映射到这些热图上，验证了灵敏度的合理性。基于这些，太赫兹光谱学可测的载流子密度范围大致从10¹⁵ cm⁻³到10²⁰ cm⁻³，但依赖于材料、掺杂类型和样品厚度。此外，灵敏度值允许对未来的光电导天线和太赫兹系统改进的潜在好处进行有根据的评估，这通过基于不同带宽的模拟进行了演示。
英文摘要：
While established semiconductor measurement techniques such as four-point probe or capacitance-voltage measurements require a physical contact to the material, terahertz spectroscopy is completely contact-free. Its capability to measure the doping of semiconductors is well known, yet the exact doping ranges that are accessible to terahertz spectroscopy are not obvious. Therefore, we introduce a sensitivity metric to clarify whether a semiconductor sample can be characterized in principle by reflection terahertz time-domain spectroscopy. This quantity takes into account the semiconductor material with a certain layer thickness, doping type, and doping level and is based on numerical simulations. In this work, we calculate this sensitivity value for relevant semiconductor materials (SiC, Si, GaN) in realistic layer stacks with up to three layers. It is used to create meaningful heat maps depending on the thicknesses and charge carrier densities of the sample structures of interest. The plausibility of the sensitivity is validated by mapping a variety of measurements with terahertz techniques from us and from other groups onto these heat maps. Based on these, the accessible range of charge carrier densities for terahertz spectroscopy spans roughly from 10$^{15}$ cm$^{-3}$ to 10$^{20}$ cm$^{-3}$, but with dependencies on material, doping type, and sample thickness. Furthermore, the sensitivity value allows for a substantiated assessment of the possible benefits future improvements of photoconductive antennas and terahertz systems could have, which is demonstrated by simulations based on varied bandwidths.
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