单片集成GaAs增强／耗尽型赝配高电子迁移率晶体管

介绍了单片集成GaAs增强／耗尽型赝配高电子迁移率晶体管（PHEMT）工艺。借助栅金属的热处理过程，形成了热稳定性良好的Pt／Ti／Pt／Au栅。AFM照片结果表明Pt金属膜表面非常平整，2nm厚度膜的粗糙度RMS仅为0．172nm。通过实验，我们还得出第一层Pt金属膜的厚度和退火后的下沉深度比大概为1：2。制作的增强型／耗尽型PHEMT的闽值电压（定义于1mA／mm）、最大跨导、最大饱和漏电流密度、电流增益截止频率分别是＋0．185／-1．22V、381．2／317．5mS／mm、275／480mA／mm、38／34GHz。增强型器件在4英寸圆片上的阈值电压标准差为19mV。

Monolithic Integration of GaAs Enhancement/depletion-mode PHEMTs

A monolithic integration of GaAs/InGaAs/AlGaAs Enhancement/Depletion mode pHEMTs process is presented. With appropriate gate annealing process,the Pt/Ti/Pt/Au gate shows high thermal stability. AFM photograph show an extremely smooth surface obtained,with a root-mean-square(RMS)roughness of 0. 172 nm for a 2 nm thick Pt film. By experiment,it was found that the ratio between the thick of first layer Pt film and penetration depth is about 1∶2.E-mode PHEMT exhibits a threshold voltage of 0.185V(defined at 1mA/ mm),peak transconductance of 381.2 mS/mm,and maximum drain current densities of 395mA/mm. On the other hand,a threshold voltage voltage of -1.22 V ,peak transconductance of 317.5mS/mm,and maximum drain current densities of 513mA/ mm for D-mode pHEMTs are obtained. The unity current gain cutoff frequency for E/D-mode PHEMTs are 38 and 34GHz,respectively.The standard deviation of the threshold voltage is as small as 19mV for E-mode devices on a 4-inch wafer.