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亮点文章
基于大栅金属高度的GaN沟道与AlGaN沟道HEMT器件击穿电压提升机理研究
第一作者 | 王中旭
通讯作者 | 赵胜雷,张进成
研究亮点
本文首次提出,采用大栅金属高度可以有效提高GaN沟道与AlGaN沟道HEMT器件击穿电压。仿真表明,提高栅金属高度可以扩大耗尽区宽度,降低峰值电场,从而提高栅漏平均击穿电场和击穿电压。该方法较简单有效,可推广至所有横向半导体器件,以提高器件击穿特性。
研究背景
氮化镓基高电子迁移率晶体管器件(Gallium Nitride High-electron-mobility transistors: GaN HEMT)作为第三代半导体器件,在高压大功率领域具有广泛的应用前景。GaN与AlN的临界击穿电场分别为3.3 MV/cm与12 MV/cm,AlGaN材料相对于GaN材料具有更为优越的击穿特性。已报道的GaN基MISHEMT器件,获得了3000 V的击穿电压和1 MV/cm的平均击穿电场,AlGaN基HEMT则获得了1650 V的击穿电压和1.65 MV/cm的平均击穿电场。虽然研究人员已经提出多种方法提高器件击穿电压,但是GaN沟道与AlGaN沟道HEMT的栅漏平均击穿电场强度相对于理论值还有很大提升空间,需进一步提升GaN沟道与AlGaN沟道HEMT的击穿特性。
研究方法及结果
本工作中,作者基于耗尽电容模型,提出增加栅金属高度可以有效提高GaN基HEMT器件击穿特性。通过提高栅金属高度,可以增加栅侧壁电容,进一步拓展耗尽区,从而缓解电场强度,提高击穿电压。随器件栅漏间距的增加,为了使栅侧壁电容明显增加,栅金属厚度的增加幅度也需要更大才能起到显著作用。基于栅漏间距7 μm的无场板GaN沟道HEMT,将栅金属厚度从0.8 μm提高到1.6 μm,击穿电压从953 V提高到1310 V。在相同的尺寸下,沟道层铝组分为40%的AlGaN沟道HEMT器件,增加栅金属厚度的器件电势分布更加均匀,击穿电压可以从1535 V提高到1763 V,即栅漏平均击穿电场强度提高至2.51 MV/cm。仿真与分析表明,提高栅金属高度可以有效提升GaN基HEMT的击穿特性。栅金属高度的提升并不影响直流输出和转移特性,对器件特征导通电阻没有影响,因此可以有效提升器件功率品质因数。此外,对于场板结构,可通过改变场板的厚度影响场板侧壁电容,进而对器件击穿特性产生类似的影响。
研究意义或前景
本工作提出了一种提高GaN基HEMT器件击穿特性的方法,并通过仿真证明GaN沟道与AlGaN沟道HEMT器件均可通过增加栅金属厚度的方法,显著提高器件击穿电压和功率品质因数。该研究可以拓展至所有横向半导体器件,以提升横向半导体器件的综合特性。
文章来源
Chin. Phys. B, 2020, 29 (2): 027301
Breakdown voltage enhancement in GaN channel and AlGaN channel HEMTs using large gate metal height
Zhong-Xu Wang(王中旭)1, Lin Du(杜林)2, Jun-Wei Liu(刘俊伟)1, Ying Wang(王颖)3, Yun Jiang(江芸)2, Si-Wei Ji(季思蔚)2, Shi-Wei Dong(董士伟)3, Wei-Wei Chen(陈伟伟)3, Xiao-Hong Tan(谭骁洪)4, Jin-Long Li(李金龙)4, Xiao-Jun Li(李小军)3, Sheng-Lei Zhao(赵胜雷)1, Jin-Cheng Zhang(张进成)1, Yue Hao(郝跃)1
1 Key Laboratory for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China;
2 Shanghai Precision Metrology and Testing Research Institute, Shanghai 201109, China;
3 China Academy of Space Technology(Xi'an), Xi'an 710000, China;
4 Sichuan Institute of Solid-State Circuits, CETC, Chongqing 400060, China
Keywords: GaN channel HEMTs, AlGaN channel HEMTs, breakdown voltage, gate metal height
A large gate metal height technique is proposed to enhance breakdown voltage in GaN channel and AlGaN channel high-electron-mobility-transistors (HEMTs). For GaN channel HEMTs with gate-drain spacing LGD=2.5 μm, the breakdown voltage VBR increases from 518 V to 582 V by increasing gate metal height h from 0.2 μm to 0.4 μm. For GaN channel HEMTs with LGD=7 μm, VBR increases from 953 V to 1310 V by increasing h from 0.8 μm to 1.6 μm. The breakdown voltage enhancement results from the increase of the gate sidewall capacitance and depletion region extension. For Al0.4Ga0.6N channel HEMT with LGD=7 μm, VBRincreases from 1535 V to 1763 V by increasing h from 0.8 μm to 1.6 μm, resulting in a high average breakdown electric field of 2.51 MV/cm. Simulation and analysis indicate that the high gate metal height is an effective method to enhance breakdown voltage in GaN-based HEMTs, and this method can be utilized in all the lateral semiconductor devices.
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