Geometrical Magnetoresistance as a Tool for Carrier Mobility Extraction in InGaAs MOSFETs

In this work, we for the first time show that the geometrical magnetoresistance (gMR) effect is a powerful tool for extracting the carrier mobility in diffusive InGaAs near-surface quantum well MOSFETs. The technique shows excellent agreement to Hall effect measurements, confirming its validity. In addition, the gMR approach is less time-consuming, is suitable for measurements directly on the FETs of interest, and works well even at low carrier concentrations. We investigate the temperature and gate dependence of the carrier mobility, from room temperature down to cryogenic temperatures. The peak gMR mobility for long-channel diffusive devices increases from ~4700 cm2/Vs at room temperature up to ~7300 cm2/Vs at 9.4 K. On the other hand, short-channel quasi-ballistic devices show a low gMR mobility of ~2700 and ~3900 cm2/Vs at room temperature and 9.4 K, respectively. By comparing the extracted mobility from devices with different gate lengths and using quantum transport simulations, we address this drop in extracted gMR mobility to an increased degree of ballistic transport and display the limitations of the gMR method for quasi-ballistic transport.