用于功率变换的高击穿增强型AlGaN/GaN HEMTs

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

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。

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 CF4 plasma treatment. The results showed that by expanding the distance of gate todrain, LCD from 5μm to 15μm, the breakdown voltage of the device rapidly increased 350 V （from 50 V to 400 V） while the threshold voltage of the device, VTH decreased from --4 V to 0. 5 V by the modulation technology of CF4 plasma. When the distance of source-terminated field plate, LFP was 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 LaD and LFp about 15μm and 3 μm were 475 V and 2.9 mΩ·cm^2 respectively. The results from RF measurement showed that with the variation of VGS, the fT and fMAX parameters 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 AIGaN/ GaN HEMTs was very suitable for high switching power application.