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 similar to 4700 cm(2)/Vs at room temperature up to similar to 7300 cm(2)/Vs at 9.4 K. On the other hand, short-channel quasi-ballistic devices show a low gMR mobility of similar to 2700 and similar to 3900cm(2)/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.