一种对称极化掺杂增强型高压GaN HFET

A Symmetrically Polarization-Doped Enhancement-Mode High-Voltage GaN HFET

针对传统AlGaN/GaN HFET击穿电压远低于理论值,以及阈值电压与开态电流之间存在制约关系的问题,提出一种对称极化掺杂增强型高压GaN HFET。采用Al组分对称渐变的AlGaN势垒层,因极化梯度分别在正向渐变AlGaN层和逆向渐变AlGaN层中诱导产生了三维电子气(3DEG)和三维空穴气(3DHG)。利用3DHG,阻断了源极与3DEG之间的纵向导通沟道,实现了新的增强型模式。同时,正向渐变AlGaN层的高浓度3DEG显著提升了器件输出电流。器件关断时,极化电荷形成的极化结有助于耗尽漂移区,优化了电场分布,提升了器件耐压。与传统AlGaN/GaN HFET相比,新器件的击穿电压从39V提高至919V,饱和漏电流提升了103.5%。

For the conventional AlGaN/GaN HFET,the breakdown voltage is far lower than its theoreticaI limit, and there is a trade-off between the threshold voltage and the on-state current.A symmetrically polarization-doped enhancement-mode high-voltage GaN HFET (SPD-HFET)was proposed.It featured back-to-back graded AlGaN barrier,which formed polarization gradient and then induced the three-dimensional electron gas (3DEG)and three- dimensional hole gas (3DHG)in the positive and negative graded AIGaN layers respectively.The SPD-HFET utilized 3DHG to block the vertical conductive channel between the source and 3DEG,thereby a new enhancementmode operation was achieved.The output current was significantly improved due to the high-density 3DEG in the positive graded AlGaN layer.In the off-state,the polarization-junction assisted depleting the drift region,thus the electric field distribution was optimized,and the device's breakdown voltage was drastically enhanced.Compared with that of conventional structures,the breakdown voltage of the SPI)-HFET was increased from 39V to 919V, and the saturation drain current was increased by 103.5%.