30-nm InAs PHEMTs With f[subscript T] = 644 GHz and f[subscript max] = 681 GHz

Abstract

We present 30-nm InAs pseudomorphic HEMTs (PHEMTs) on an InP substrate with record fT characteristics and well-balanced fT and f[subscript max] values. This result was obtained by improving short-channel effects through widening of the side-recess spacing (L[subscript side]) to 150 nm, as well as reducing parasitic source and drain resistances. To compensate for an increase in Rs and Rd due to L[subscript side] widening, we optimized the ohmic contact process so as to decrease the specific ohmic contact resistance (Rc) to the InGaAs cap to 0.01 Ω·mm. A 30-nm InAs PHEMT with t[subscript ins] = 4 nm exhibits excellent gm,max of 1.9 S/mm, fT of 644 GHz, and f[subscript max] of 681 GHz at V[subscript DS] = 0.5 V simultaneously. To the knowledge of the authors, the obtained fT in this work is the highest ever reported in any FET on any material system. This is also the first demonstration of simultaneous fT and f[subscript max] higher than 640 GHz in any transistor technology.