摘要:
通过自洽求解一维泊松方程和薛定谔方程, 得到了p-GaN/p-AlxGa1-xN异质结界面处的价带结构和二维空穴气（2DHG）分布, 研究了Al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-AlxGa1-xN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-AlxGa1-xN的欧姆接触性能.
Abstract:
In this paper, the characteristics of the two-dimensional hole gas (2DHG) in p-GaN/p-AlxGa1-xN heterojunction is investigated in detail, based on self-consistent solutions of one-dimensional Poisson and Schr?dinger equations. The valence band structures and the 2DHG distributions are calculated in the cases of different Al components and piezoelectric polarization effects. Then, the influences of Al components and piezoelectric polarization effects on 2DHG are analysed specifically. The results show that with the increase of Al component, the quantum well at the heterojunction interface turns deeper and narrower, which leads to an accelerated growth of the 2DHG peak density and a line increase of the 2DHG sheet concentration. Furthermore, piezoelectric polarization effects also make the quantum well at the heterojunction interface deeper and narrower, at the same time, the Fermi level moves close to the top of the barrier and the location of peak density moves close to the heterojunction interface. In addition, the influences of valence band offset and acceptor doping concentration on 2DHG are relatively small. Ohmic contact of p-AlxGa1-xN is fabricatea with the 2DHG, and its I-V characteristic is much better than that without the 2DHG, which indicates that the 2DHG can significantly improve the performance of p-AlxGa1-xN ohmic contact.
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