Recessed-gate structure approach toward normally off high-voltage AlGaN/GaN HEMT for power electronics applications
Recessed-gate structure approach toward normally off high-voltage AlGaN/GaN HEMT for power electronics applications
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DOI：
10.1109/ted.2005.862708
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发表时间：
2006-02-01
影响因子：
3.1
通讯作者：
Omura, I
中科院分区：
文献类型：
--
作者：
Saito, W;Takada, Y;Omura, I
为了实现电力电子用高压AlGaN/GaN高电子迁移率晶体管(HEMTs)的常关工作，研究了一种凹栅结构。凹栅结构对于实现常断高压AlGaN/GaN HEMTs非常有吸引力，因为栅极阈值电压可以通过凹槽的刻蚀深度来控制，而不会显著增加导通电阻特性。采用这种结构，仅在栅电极下，阈值电压就可以随着二维电子气(2DEG)浓度的降低而提高，而在其他沟道区，如漏和栅之间的沟道中，2DEG浓度不会降低。实验证明了阈值电压的提高。制作的凹栅器件的阈值电压提高到-0.14V，而没有凹栅结构的阈值电压约为-4V，器件的导通电阻保持在4m欧米伽中心点cm(2)，击穿电压为435V，导通电阻和击穿电压的折衷特性与正常导通器件相同。从器件设计的角度出发，利用栅极下AlGaN层厚度与二维气体密度之间的关系，模拟了常关型器件的导通电阻。结果表明，采用MIS栅结构，在凹槽边缘和栅极之间不存在偏移区的凹槽刻蚀将进一步提高导通电阻。模拟结果表明，对于阈值电压高达+1V的常关型AlGaN/GaN HEMT，其导通电阻可能低于1m欧米伽中心点cm(2)。
A recessed-gate structure has been studied with a view to realizing normally off operation of high-voltage AlGaN/GaN high-electron mobility transistors (HEMTs) for power electronics applications. The recessed-gate structure is very attractive for realizing normally off high-voltage AlGaN/GaN HEMTs because the gate threshold voltage can be controlled by the etching depth of the recess without significant increase in on-resistance characteristics. With this structure the threshold voltage can be increased with the reduction of two-dimensional electron gas (2DEG) density only under the gate electrode without reduction of 2DEG density in the other channel regions such as the channel between drain and gate. The threshold-voltage increase was experimentally demonstrated. The threshold voltage of fabricated recessed-gate device increased to -0.14 V while the threshold voltage without the recessed-gate structure was about -4 V. The specific on-resistance of the device was maintained as low as 4 m Omega center dot cm(2) and the breakdown voltage was 435 V. The on-resistance and the breakdown voltage tradeoff characteristics were the same as those of normally on devices. From the viewpoint of device design, the on-resistance for the normally off device was modeled using the relationship between the AlGaN layer thickness under the gate electrode and the 2DEG density. It is found that the MIS gate structure and the recess etching without the offset region between recess edge and gate electrode will further improve the on-resistance. The simulation results show the possibility of the on-resistance below 1 m Omega center dot cm(2) for normally off AlGaN/GaN HEMTs operating at several hundred volts with threshold voltage up to +1 V.