一种具有极化调制层的AlGaN/GaN HEMT结构

A AlGaN/GaN HEMT structure with polarization modulation layer

针对AlGaN/GaN HEMT器件存在的GaN缓冲层漏电和栅极漏端处电场集中效应导致器件耐压性能不高,无法完全发挥GaN材料高击穿电压优势的问题,提出了一种具有极化调制层的AlGaN/GaN HEMT器件结构。该结构主要有2个特点:一是缓冲层材料用禁带宽度更大的Al_(0.05)Ga_(0.95) N代替GaN,以减小缓冲层漏电,提高击穿电压;其次是在栅漏间势垒层上外延一层极化调制层,该极化调制层由Al组分沿材料生长方向线性降低的Al_(x)Ga_(1-x)N(0<x<0.26)材料构成。根据极化掺杂理论,Al组分逆向渐变的AlGaN材料因极化电荷不平衡会在体内诱导产生空穴。极化调制层的空穴在器件反向关断时有助于缓解栅极边沿电场集中,优化栅漏间电场分布,从而提升器件耐压能力。基于功率器件优值FOM标准,利用Sentaurus TCAD软件对提出结构进行模拟验证。实验结果表明,所提出结构的击穿电压为645 V,比导通电阻为1.09 mΩ·cm^(2),与常规双异质结器件结构相比,击穿电压提高了339%,而比导通电阻仅增加了0.38 mΩ·cm^(2),FOM值达到了382 MW·cm^(-2)。

A AlGaN/GaN HEMT device structure with polarization modulation layer is proposed for the low breakdown voltage of the conventional GaN HEMT,which is caused by the leakage of the GaN buffer and the concentration effect of electric field at closing to the drain under the gate.The structure contains two characteristics.First,Al_(0.05)Ga_(0.95)N with wider energy band gap is used instead of GaN as buffer layer material to reduce the leakage of the buffer layer and increase breakdown voltage.Second,a polarization modulation layer is epitaxially grown on the AlGaN barrier layer between the gate and the drain,which is formed by Al_(x)Ga_(1-x)N with reverse gradient of Al composition(0<x<0.26).According to the theory of polarization doping,AlGaN materials with a graded Al composition will produce the hole due to the uneven polarization charge.The hole in the polarization modulation layer expands the area of the depletion region,raises the electric field between the gate and the drain,relieves the electric field concentration near the gate.The proposed structure is based on the standard of power device figure of merit,and is verified by Sentaurus TCAD.The breakdown voltage,specific on-resistance and FOM value of the proposed structure are 645 V,1.09 mΩ·cm^(2)and 382 MW·cm^(-2).Compared with the double heterojunction structure,the breakdown voltage is increased by 339%,while the specific on-resistance is only increased by 0.38 mΩ·cm^(2).