A delta-doped In0.24Ga0.76As/GaAs pseudomorphic high electron mobility transistor using a graded superlattice spacer

A new delta -doped In0.24Ga0.76As/GaAs pseudomorphic high electron mobility transistor (HEMT) using a graded superlattice spacer grown by molecular be am epitaxy (MBE) has been successfully fabricated and investigated. The pre sent device structure demonstrated a more than 40% enhancement of electron mobility and 20% higher product value of electron mobility and two-dimensio nal electron gas (2DEG) concentration than those of the conventional HEMT w ith single undoped spacer under the same growth specifications. Superior de vice characteristics were achieved by employing the thickness-graded superl attice spacer to accommodate the lattice-mismatch-induced strain and to imp rove the interfacial quality. For a gate length of 1 mum, the maximum drain -to-source saturation current density and extrinsic transconductance of the present HEMT design are 165 mA mm(-1) and 107 mS mm(-1),respectively, at r oom temperature. (C) 2001 Academic Press.