Molecular beam epitaxial growth and characterization of pseudomorphic modulation-doped field effect transistors

Abstract

We have investigated the luminescent and device properties of pseudomorphic AlGaAs/InGaAs modulation-doped field effect transistors (MODFETs) with different InAs molar fractions in the InGaAs channel. Molecular beam epitaxy, which simulataneously deposits group III atoms and As 4 molecules on the substrate surface, was used to grow the random alloy In xGa 1-xAs channel layer for x≤0.4, and migration-enhanced epitaxy (MEE), which alternatingly deposits group III atoms and As 4 molecules on the surface, was used to grow sequential layers of InAs and GaAs in the channel region with large effective x (up to 0.5). For 1 microm gate length MODFETs with random alloy In xGa 1-xAs channels the transconductance g m and saturation drain current I dss exhibit a maximum at x = 0.17 because of the superior electron transport properties of InGaAs compared with GaAs. g m and I dss decrease drastically for x higher than 0.32 as a result of misfit dislocation generation. The photoluminescence peaks of In xGa 1-xAs channels of these MODFET samples show a similar trend, strong intensity for the In 0.17Ga 0.83As channel and very weak intensity for the In 0.4Ga 0.6As channel. However, MODFETs with a nominally (InAs) 2(GaAs) 2 channel grown by MEE exhibit higher g m, I dss and photoluminescence intensity than those with an In 0.4Ga 0.6As channel. © 1991.