Fabrication and characteristics of 0.12 μn single and double-recessed gate AlGaAs/lnGaAs/GaAs PHEMTs using a SiNx pre-passivation layer

We report the fabrication and dc and microwave characteristics of 0.12-mu m single and double-recessed T-gate AlGaAs/InGaAs/GaAs pseudomorphic HEMTs (PHEMTs) using a SiNx pre-passivation layer. 300-angstrom and 200-angstrom SiNx layers were deposited by plasma-enhanced chemical vapor deposition (PECVD) at 260 degrees C to protect the device and to define the gate footprint. The single and double-recessed processes were carried out by dry etching techniques. Completed double-recessed T-gate PHEMT devices exhibited a peak transconductance, g(m), of 756 mS/mm, a current-gain-cutoff frequency (f(T)) as high as 124 GHz, and a maximum oscillation frequency (f(max)) of 247 GHz. We fabricated a 4-stage low-noise amplifier (LNA) comprising a two-finger 0.12 mu m x 100 Am PHEMT in each stage. The chip size is 3.7 mm x 1.6 mm and the thickness is 100 mu m.