用于功率变换的高击穿增强型AlGaN/GaN HEMTs

首次采用CF4等离子体技术实现可用于功率变换的增强性AlGaN/GaN功率器件。实验结果表明,当AlGaN/GaN器件经功率150W和时间150s等离子体轰击后,器件阈值电压从-4V被调制约为0.5V,表现为增强型。当漂移区LGD从5μm增加到15μm,器件的击穿电压从50V迅速增大到400V,电压增幅达350V。采用长度为3μm源场板结构将器件击穿电压明显地提高,击穿电压增加约为475V,且有着比硅基器件更低的比导通电阻,约为2.9mΩ.cm2。器件模拟结果表明,因源场板在远离栅边缘的漂移区中引入另一个电场强度为1.5MV/cm的电场,从而有效地释放了存在栅边缘的电场,将高达3MV/cm的电场减小至1MV/cm。微波测试结果表明,器件的特征频率fT和最大震荡频率fMAX随Vgs改变,正常工作时两参数均在千兆量级。栅宽为1mm的增强型功率管有较好的交直流和瞬态特性,正向电流约为90mA。故增强型AlGaN/GaN器件适合高压高频大功率变换的应用。

High-breakdown Voltage Field-plated Normally-OFF AlGaN/GaN HEMTs for Power Switch Application

The enhancement-mode (E-mode) high breakdown voltage AlGaN/GaN HEMTs with source-terminated field plate was firstly fabricated for high frequency and high power application,employing CF4plasma treatment. The results showed that by expanding the distance of gate to drain,LGDfrom 5 μm to 15 μm,the breakdown voltage of the device rapidly increased 350 V (from 50 V to 400 V) while the threshold voltage of the device,VTHdecreased from-4 V to 0.5 V by the modulation technology of CF4 plasma. When the distance of source-terminated field plate,LFPwas about 3 μm,the breakdown voltage of the device was apparently improved because the electric field near the gate edge was effectively shielded. The breakdown voltage and the specific on-resistance for the LGDand LFP about 15 μm and 3 μm were 475 V and 2.9 m Ω·cm2respectively. The results from RF measurement showed that with the variation of VGS,the fTand fMAXparameters of the device with source-terminated field plate were the order of Gigahertz frequency. The DC,AC and transient characteristics of E-mode power AlGaN/GaN HEMTs were satisfied and its forward current was about 90 mA. Therefore the E-mode AlGaN/GaN HEMTs was very suitable for high switching power application.