The use of magnetic fields in the electrical characterization of semiconductor materials is familiar to everyone in the form of Hall‐effect measurements. However, there is another magnetic‐field‐based phenomenon, magnetoresistance (MR), which is highly useful but not nearly so familiar to the majority of workers. One of the unique features of MR measurements is their applicability to common device structures, in particular, field‐effect transistors (FETs) and contact‐resistance patterns. We will show how channel mobility information can be extracted from the MR data in metal‐semiconductor FETs (MESFETs) and modulation‐doped heterostructure FETs (MODFETs), and also how the material under ohmic contacts can be compared with the unprocessed material to see if appreciable contact‐element diffusion has occurred. Finally, we will consider some common problems which are often overlooked in performing simple Hall‐effect measurements on thin structures. Some useful formulas and plots are presented.
Look, D. C.
(1990). Review of Hall Effect and Magnetoresistance Measurements in GaAs Materials and Devices. Journal of The Electrochemical Society, 137 (1), 260-266.