Study of the dependence of Ga/sub 0.47/In/sub 0.53/As/Al/sub x/ In/sub 1-x/As power HEMT breakdown voltage on Schottky layer design and device layout

A systematic study of the improvement of Ga/sub 0.47/In/sub 0.53/As/Al/sub x/ In/sub 1-x/As HEMT (high electron mobility transistor) breakdown voltage by varying the Schottky layer design and device geometry is presented. The HEMT structure investigated is a modulation-doped Ga/sub 0.47/In/sub 0.53/As/Al/sub x/ In/sub 1-x/As on InP device with a sheet of charge placed at the center of the 300 AA wide channel. The device with a gate length of 0.5 mu m, a source-drain spacing of 5 mu m, and an Al/sub 0.7/In/sub 0.3/As Schottky layer exhibited the best breakdown characteristics of mod BV/sub gd/ mod =6.8 V and BV/sub ds/=7.8 V. The typical transistor had a maximum transconductance of 500 mS/mm, a full channel current of 700 mA/mm for a gate bias of 0.4 V, and a current gain cutoff frequency of over 80 GHz. The power performance was measured on 500- mu m-wide devices at 4 GHz and V/sub ds/=4.5 V. Under Class AB operating conditions, the output power density, power-added efficiency, and power gain were 0.45 W/mm, 59%, and 14.25 dB, respectively.