High-transconductance delta-doped InAs/AlSb HFET's with ultrathin silicon-doped InAs quantum well donor layer

Modulation-doping of InAs/AlSb quantum wells generally requires the use of chalcogenide donor impurities because silicon, the usual donor of choice in MBE, displays an amphoteric behavior in antimonide compounds, In this letter, we demonstrate the use of an ultrathin 9 Angstrom silicon-doped InAs well to delta-dope the current-carrying InAs channel of an InAs/AlSb heterostructure field-effect transistor (HFET), Using this new approach, we have fabricated delta-doped 0.6-mu m gate InAs/AlSb HFET's with a measured extrinsic transconductance of 800 mS/mm at V-DS = 0.8 V, a cutoff frequency f(T) = 60 GHz (f(MAX) = 87 GHz), and well-behaved I-V curves, HFET's with a 2-mu m gatelength also feature very high transconductances in the 700-800 mS/mm range at V-DS = 1.5 V, The present work eliminates the requirement for chalcogenide compound donor sources to delta-dope InAs/AlSb quantum wells by allowing the use of silicon in the fabrication of high-performance InAs/AlSb HFET's.