The DC and microwave characteristics of two sets of AlGaAs/InGaAs PHEMT's having a gate length of 0.2 μm are compared. The first set is composed of devices fabricated using a trilayer electron beam resist process for T-gate recess and metallization. The second set is composed of devices fabricated using a new four-layer electron beam resist process which enables the asymmetric placement of a T-gate in a wide recess trench. Devices fabricated using the four-layer resist process showed improved breakdown voltage lower gate-drain feedback capacitance lower output conductance and higher fmax with only slight reduction of drain current and transconductance. For example the off-state drain-source breakdown voltage increased from 5.2 to 12.5 V and the fmax increased from 133 to 158 GHz as the drain side cap recess Lud was increased from 0 to 0.55 μm.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering