Electrical characterization of pseudomorphic GaAs/InGaAs/AlGaAs and AlGaAs/InGaAs/AlGaAs modulation doped field effect transistor-type heterostructures grown by molecular-beam epitaxy

Abstract

We studied the influence of the indium composition y, growth temperature Ts and InGaAs quantum-well channel thickness dch on the 300 and 77 K Hall electrical properties of pseudomorphic modulation doped field effect transistor (MODFET)-type heterostructures grown by molecular-beam epitaxy. In agreement with Nguyen et al., we find an optimum channel thickness of 90 Å for an indium composition y=0.25 of the channel. Significant improvements in sheet resistivity ρs and in carrier concentration nso were obtained by using AlGaAs doped barriers on both sides of the pseudomorphic channel. We were thus able to obtain a two-dimensional electron gas sheet density nso as high as 4.0×1012 cm−2 at 77 K, which is among the highest values ever reported for MODFETs on GaAs.