Optimized recess etching criteria for T-gate fabrication achieving ft= 290 GHz at Lg= 124 nm in metamorphic HEMT with In0.7Ga0.3As channel

Abstract

We propose criteria for recess etching to fabricate T-gate used in InGaAs HEMTs. By patterning additional rectangular pads on the source and drain metals in the e-beam lithography step, it is possible to measure the drain-to-source resistance (R) and current (I). the ratio (Γ) of before and after etching for each R and I can be used as criteria to determine the point in time to stop etching. By performing recess etching with Γ= 1.97 for R and Γ= 0.38 for I on an epiwafer having cap doping concentration of 2= 10 cm and channel indium content of 0.7, we have fabricated InGaAs mHEMT device showing g= 1603 mS/mm and f= 290 GHz at L= 124 nm. The criteria presented can be applied to InGaAs HEMTs with various epitaxial structures.