中文摘要：

本文报道了作者提出的阶梯AlGaN外延层新型AlGaN/GaN HEMTs结构的实验结果.实验利用感应耦合等离子体刻蚀（ICP）刻蚀栅边缘的AlGaN外延层,形成阶梯的AlGaN外延层结构,获得浓度分区的沟道2DEG,使得阶梯AlGaN外延层边缘出现新的电场峰,有效降低栅边缘的高峰电场,从而优化了AlGaN/GaN HEMTs器件的表面电场分布.实验获得了阈值电压-1.5V的新型AlGaN/GaN HEMTs器件.经过测试,同样面积的器件击穿电压从传统结构的67V提高到新结构的106V,提高了58%左右;脉冲测试下电流崩塌量也比传统结构减少了30%左右,电流崩塌效应得到了一定的缓解.

英文摘要：

In this paper,experimental results are reported about the new Al0.25Ga0.75N/GaN high electron mobility transistor（HEMT） with a step AlGaN layer.The rule of 2DEG concentration variation with the thickness of AlGaN epitaxial layer has been applied to the new AlGaN/GaN HEMTs： The step AlGaN layer is formed at the gate edge by inductively coupled plasma etching,the 2DEG concentration in the etched region is much lower than the other parts of the device.A new electric field peak appears at the corner of the step AlGaN layer.The high electric field at the gate edge is decreased effectively due to the emergence of the new electric field peak,and this optimizes the surface electric field of the new AlGaN/GaN HEMTs.The new devices have the same threshold voltage and transconductance as the conventional structure,-1.5 V and 150 m S/mm.That means,the step AlGaN layer does not affect the forward characteristics of the AlGaN/GaN HEMTs.As the more uniform surface electric field distribution usually leads to a higher breakdown voltage（BV）,with the same gate to drain length LGD= 4 μm,the BV can be improved by 58% for the proposed Al0.25Ga0.75N/GaN HEMTs as compared with the conventional structure.At VGS= 1 V,the saturation currents（Isat） is 230 m A/mm for the conventional Al0.25Ga0.75N/GaN HEMT and 220 m A/mm for the partially etched Al0.25Ga0.75N/GaN HEMT（LEtch= 4 μm,LGD= 4 μm）.The decrease of Isat is at most 10 m A/mm.However,as the BV has a significant enhancement of almost 40 V,these drawbacks are small enough to be acceptable.During the pulse I-V test,the current collapse quantity of the conventional structure is almost 40% of the maximum IDS（DC）,but this quantity in the new devices is only about 10%,thus the current collapse effect in Al0.25Ga0.75N/GaN HEMTs has a significant remission for a step AlGaN layer.And as the high electric field peak at the gate edge is decreased,the effect of the gate electrode on electron injection caused by this electric field peak is also included.The injected electro