Effective Schottky Barrier Height Model for N‐Polar and Ga‐Polar GaN by Polarization‐Induced Surface Charges with Finite Thickness
Effective Schottky Barrier Height Model for N‐Polar and Ga‐Polar GaN by Polarization‐Induced Surface Charges with Finite Thickness
复制标题
基于有限厚度极化感应表面电荷的 N 极和 Ga 极 GaN 的有效肖特基势垒高度模型
DOI：
10.1002/pssb.201900528
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Makabe Isao
中科院分区：
文献类型：
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作者：
Suemitsu Tetsuya;Makabe Isao
氮极性GaN材料体系是一种很有前途的高频应用，如毫米波应用。肖特基势垒高度是N极GaN器件应用所必需的基本参数之一。本文制备了N极GaN和Ga极GaN的垂直肖特基二极管，实验发现N极GaN的势垒高度比Ga极GaN的势垒高度小0.21 V。势垒高度的差异源于表面以下几埃厚的极化感生表面电荷层。能带分布的数值计算表明，在N极(Ga极)表面，由大量极化电荷引起的明显的能带弯曲根据极化电荷的符号向下(向上)推动导带能量，从而产生两种不同的有效肖特基势垒高度。这种差异可以通过假设极化电荷层厚度约为5 ä来解释。文中还提出了一个简单的分析模型来估算两极之间的势垒高度差。
The nitrogen‐polar GaN material system is a promising candidate for high‐frequency applications, such as those in the millimeter‐wave range. Schottky barrier height is one of fundamental parameters necessary for device applications of N‐polar GaN. Herein, vertical Schottky diodes for both N‐polar and Ga‐polar GaN are prepared, and it is found through experiments that the barrier height of N‐polar GaN is smaller than that of Ga‐polar GaN by 0.21 V. This difference in the barrier height stems from the polarization‐induced surface charge layer of a few angstroms thickness under the surface. Numerical calculation of band profiles suggests that a significant band bending caused by the large amount of polarization charges pushes the conduction band energy downward (upward) in the N‐polar (Ga‐polar) surface depending on the sign of the polarization charges, which results in two different effective Schottky barrier heights. This difference is explained by assuming the polarization‐charge layer thickness of about 5 Å. A simple analytical model to estimate the difference in barrier heights between the two polarities is also proposed.