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采用数值算法自洽求解Poisson和Schrdinger方程,计算了AlGaN势垒层的应变弛豫度对高Al含量AlGaN/GaN高电子迁移率晶体管(HEMT)中的导带结构、电子浓度以及二维电子气(2DEG)薄层电荷密度的影响.利用所获得的精确薄层电荷密度与栅电压的关系,采用非线性电荷控制模型解析求解了应变弛豫度对AlxGa1-xN/GaNHEMT直流输出特性的影响.计算表明,应变弛豫度为0时所获得的Al0.50Ga0.50N/GaNHEMT的最大二维电子气薄层电荷密度为2.42×1013cm-2,最大漏电流为2482.8mA/mm;应变弛豫度为1时所获得的最大二维电子气薄层电荷密度为1.49×1013cm-2,最大漏电流为1149.7mA/mm.模拟结果同已有的测试数据相比,符合较好.对模拟结果的分析表明,对高Al含量的AlGaN/GaNHEMT进行理论研究时需要考虑应变弛豫度的影响,减小AlGaN势垒层的应变弛豫度可显著提高器件的性能.
The Poisson and Schrödinger equations were solved by numerical algorithm and the strain relaxation of AlGaN barrier layer was calculated for the conduction band structure, electron concentration and two-dimensional (2D) structure of AlGaN / GaN high electron mobility transistor (HEMT) The influence of strain relaxation on the DC output characteristics of AlxGa1-xN / GaNHEMT was solved by using the nonlinear charge control model. By using the relationship between the accurate sheet charge density and gate voltage, The calculated results show that the maximum two-dimensional electron gas charge density of Al0.50Ga0.50N / GaNHEMT obtained at strain relaxation is 2.42 × 1013cm-2 and the maximum leakage current is 2482.8mA / mm. The strain relaxation The maximum two-dimensional electron gas sheet charge density is 1.49 × 1013cm-2 and the maximum leakage current is 1149.7mA / mm when the electrical conductivity is 1. The simulation result is in good agreement with the existing test data. The results show that the theoretical study of AlGaN / GaNHEMT with high Al content needs to consider the effect of strain relaxation. Decreasing the strain relaxation of AlGaN barrier layer can significantly improve the device performance.