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通过自洽求解一维泊松方程和薛定谔方程,得到了p-GaN/p-Al_xGa_(1-x)N异质结界面处的价带结构和二维空穴气(2DHG)分布,研究了A1组分和压电极化效应对界面处2DHG性质的影响,给出了异质界面处2DHG的面密度、浓度分布以及价带结构.实验结果表明:随着Al组分的增加,异质结界面处势阱明显加深变窄,这使得2DHG的峰值密度加速上升,也使得面空穴密度近直线上升;压电极化效应也明显使界面处势阱加深变窄,并且使费米能级向势垒顶端移动,峰值浓度的位置向界面处移动;另外,价带带阶高度和受主杂质浓度对2DHG的影响较小.利用这层2DHG制作的p-Al_xGa_(1-x)N的欧姆接触,电流电压特性明显好于直接制作的电极,说明了2DHG可以显著改善p-Al_xGa_(1-x)N的欧姆接触性能.
The valence band structure and 2DHG distribution at p-GaN / p-Al_xGa_ (1-x) N heterojunction interface were obtained by solving one-dimensional Poisson equation and Schrödinger equation. Al component and piezoelectric polarization on the properties of 2DHG at the interface, the areal density, concentration distribution and valence band structure of 2DHG at the heterogeneous interface are given.The experimental results show that with the increase of Al composition, the heterogeneity The potential well at the junction interface is obviously deepened and narrowed, which accelerates the peak density of 2DHG and makes the density of surface holes nearly linearly increase. The piezoelectric polarization also obviously deepens and narrows the potential well at the interface, And the position of the peak concentration moves toward the interface. In addition, the influence of valence band height and acceptor impurity concentration on 2DHG is small.Using this layer of p-Al_xGa_ (1-x) N Ohmic contact, and the current-voltage characteristics are obviously better than that of the directly fabricated electrode. It shows that 2DHG can significantly improve the ohmic contact properties of p-Al_xGa_ (1-x) N.