High efficiency microwave power AlGaAs/InGaAs PHEMTs fabricated by dry etch single gate recess

An optimized pseudomorphic high electron mobility transistor (PHEMT) epitaxial structure processed with a novel single gate recess technique is shown to achieve 850 mW of output power (760 mW·mm^-1 saturated power density) with 50% power added efficiency at X-band when operated at a CW and nearly class A condition. The multi-finger devices (14×80 μm) retain high extrinsic transconductances (380-420 mS·mm^-1), with exceptional breakdown voltage (>18 V). The combination of optimized epi layer structure design and uniform gate recess using a damage-free, etch-stop, dry plasma processing step produces consistently and uniformly high f_T values (80 GHz at V_DS=1 V, 35 GHz at V_DS=7 V) even at low I_DS (100 mA·mm^-1).