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利用有效质量理论自洽求解Poisson和Schrdinger方程理论研究了背势垒插入层对InAlN/GaN晶格匹配异质结构的电学性能的影响。研究表明,对于In0.17Al0.83N/AlN/GaN的异质结构,AlN的临界厚度为2.43 nm。此时,异质结中二维电子气(2DEG)浓度达到2.49×1013 cm-2,且不随势垒层厚度的变化而变化。重点模拟研究了具有背势垒的InAlN/AlN/GaN/AlGaN/GaN和InAlN/AlN/GaN/InGaN/GaN两种结构的能带结构和2DEG的分布情况。理论结果表明,采用AlGaN背势垒结构时,对于AlGaN的任意Al组分,GaN沟道层导带底能量均被抬升,增强了AlN/GaN三角势阱对2DEG的限制作用,提高了电子迁移率。采用InGaN/GaN作为背势垒结构,当InGaN厚度为2或3 nm时,三角势阱中的2DEG随InGaN中In组分的增加先升高后降低,这主要是由于GaN/InGaN界面处产生的正极化电荷的影响,引起电子在AlN/GaN三角势阱和InGaN/GaN势阱之间的分布变化。
The influence of back barrier insertion layer on the electrical properties of InAlN / GaN lattice-matched heterostructures was investigated using the Poisson and Schrödinger equations based on the effective mass theory. The results show that the critical thickness of AlN is 2.43 nm for the heterostructure of In0.17Al0.83N / AlN / GaN. In this case, the 2DEG concentration in the heterojunction reaches 2.49 × 1013 cm-2, which does not change with the thickness of the barrier layer. The energy band structure and 2DEG distribution of InAlN / AlN / GaN / AlGaN / GaN and InAlN / AlN / GaN / InGaN / GaN with back barrier are mainly studied. The theoretical results show that with the AlGaN back-barrier structure, the energy at the bottom of the conduction band of the GaN channel layer is raised for any Al composition of the AlGaN layer, which enhances the limitation of the AlN / GaN triangular well to 2DEG and enhances the electron transport rate. When InGaN / GaN is used as the back-barrier structure, the 2DEG in the triangular well increases first and then decreases with the increase of In content in InGaN when the thickness of InGaN is 2 or 3 nm, which is mainly due to the increase of the InGaN / Of the positive polarization charge, causing the distribution of electrons between the AlN / GaN triangular well and the InGaN / GaN potential well.