Charge carrier mobilities are conveniently measured in simple, homostructure field-effect transistors (FET's) by means of the geometric magnetoresistance (GMR) technique. Heterostructure FET's, however, are more complicated because of multiple conducting regions, as well as multiple conducting bands within a given region. We apply a multilayer GMR mobility model to a frequently used heterostructure FET design, namely, the Al0.3Ga0.7As conduction band. In the particular MODFET structure studied here, the lowest GaAs subband mobility ranges from 5.7X103 cm2/Vs at threshold to 6.9X103 cm2/Vs at saturation while Al0.3Ga0.7As mobility is about 5X102 cm2/Vs. This is the first time that the various mobilities in MODFET structures have been separately measured.
Look, D. C.,
Norris, G. B.,
& Morkoç, H.
(1985). Magnetoresistance Method To Determine GaAs and Alxga1-Xas Mobilities in Alxga1-Xas/GaAs Modulation-Doped Field-Effect Transistor Structures. Applied Physics Letters, 47 (3), 267-269.