Investigation of field-plate gate on heterojunction doped-channel field effect transistors

In this work, we report a metal-splitting fieldplate gate on heterojunction doped-channel field effect transistors (HDCFETs) with an application of GaAs-bulk. Experimentally, a HDCFET with a gate-metal length of 0.4 μm, a field-plate length of 0.6 μm, and a bulk thickness of 120 nm was successfully fabricated for comparing to that with a 1-μm traditional planar-gate. The current density (451 mA/mm), transconductance (225 mS/mm), breakdown voltages (VBD(DS)/VBD(GD)=22/−25.5 V), gate-voltage swing (2.24 V), unity current-gain and power-gain frequencies (ft/fmax=17.2/32 GHz) are improved as compared to those of 1-μm gate device without field plates. At 1.8 GHz with a VDS of 4.0 V operation, a maximum power-added efficiency (PAE) of 36 % with an output power of 13.9 dBm and a power gain of 8.7 dB was obtained. Saturated output power and linear power gain are 316 mW/mm and 13 dB, respectively.