Si/Ge/Si异质横向SPiN二极管固态等离子体解析模型

采用横向表面PiN(SPiN)二极管构造的硅基可重构天线具有众多优于传统天线的独特优势, 是实现天线小型化和提升雷达与微波通信系统性能的有效技术途径. 本文提出一种Si/Ge/Si异质横向SPiN二极管, 并基于双极扩散模型与Fletcher型边界条件, 在大注入条件下建立了二极管结电压、电流密度与本征区固态等离子体浓度分布解析模型, 并数值模拟分析了本征区长度、P⁺与N⁺区掺杂浓度、外加电压对所建模型的影响. 结果表明, 固态等离子体浓度随本征区长度的增加下降, 随外加电压的增加而指数上升, 随P⁺与N⁺区掺杂浓度的提高而上升, 电流密度随外加电压的增加而指数上升. 同等条件下, 异质SPiN二极管的固态等离子体浓度相比同质二极管提高近7倍以上. 本文所建模型为硅基可重构天线的设计与应用提供有效的参考.

Analytic models for solid state plasma of Si/Ge/Si heterogeneous and lateral SPiN diode

Silicon-based reconfigurable antenna, which is fabricated by heterogeneous and lateral surface PiN (SPiN), is an effective technology to achieve antenna miniaturization and enhance radar and wireless communication system performance. In this paper, the heterogeneous and lateral Si/Ge/Si SPiN diode is presented, that can weaken the band gap narrowing of the P ⁺ and N ⁺ region to improve the injection ratio of PN junction. And the electrical properties of the solid state plasma within the intrinsic region are also studied. Based on the bipolar diffusion model and Fletcher boundary condition, the analytic models of the junction voltage, the current density and the solid state plasma concentration distribution are established for a large injection current, and the numerical simulation has been carried out. Results show that the junction voltage increases linearly with the increase of applied voltage and the solid state plasma concentration at the boundary; and the current density increases exponentially with increasing junction voltage and the applied voltage, respectively. And the applied voltage and the current density of heterogeneous SPiN diode is lower than that of homogeneous SPiN diode under the same condition due to the difference of barrier heights between the heterojunction and homojunction. In addition, results also show that the value of the concentration decreases with increasing length of the intrinsic region; otherwise, it increases with increasing applied voltage and the doping concentration in the P⁺ and N⁺ regions. Under the same conditions, the solid state plasma concentration of the heterogeneous SPiN diode is nearly seven times that of homogeneous diode, which is in excellent agreement with the data published, giving the evidence for the validity of our method. The proposed models provide an effective reference for the design and application of silicon-based reconfigurable antennas.