InGaP/InGaAs Pseudomorphic Heterodoped-Channel FETs With a Field Plate and a Reduced Gate Length by Splitting Gate Metal

Depositing gate metal across a step undercut between the Schottky barrier layer and the insulator-like layer is employed to obtain a reduced gate length of 0.4 mum with an additional 0.6-mum field plate from a 1-mum gate window. Most dc and ac characteristics including current density (I DSS =451mA/mm), transconductance (g m,max =225mS/mm), breakdown voltages (V BD(DS) /V BD(GD) =22/-25.5V), gate-voltage swing (GVS=2.24V), cutoff, and maximum oscillation frequencies (f t /f max =17.2/32GHz) are improved as compared to those of a 1-mum gate device without field plate. At a V DS of 4.0 V, a maximum power added efficiency of 36% with an output power of 13.9 dBm and a power gain of 8.7 dB are obtained at a frequency of 1.8 GHz. The saturated output power and the linear power gain are 316 mW/mm and 13 dB, respectively