Anomalous behavior of a quantized Hall plateau in a high-mobility Si metal-oxide–semiconductor field-effect transistor

Measurements at 14 T and 340 mK of the quantized Hall resistance of the i=4 plateau of a Si metal-oxide-semiconductor field-effect transistor (Si-MOSFET) made with a precision of 0.015 ppm and an accuracy of 0.005 ppm revealed unexpected irregularities. Smooth variations of ±0.04 ppm were observed across the plateau even though the Si-MOSFET had a mobility of 1.2 ${\mathrm{m}}^2$/V s and a diagonal resistivity less than 0.002 ppm of the plateau resistivity. Furthermore, measurements over a period of several months indicated that the plateau shape is metastable. A variety of possible causes for these phenomena are discussed, but none provides a satisfactory explanation.