Quantum Magnetotransport in InGaAs/InP at High Magnetic Fields and Low Temperatures

Quantum Hall effect and Shubnikov-de Haas effect measurements were made in two-dimensional electron gas in liquid phase epitaxially grown Ga0.47In0.53As/InPheterostructures in high magnetic fields in the temperature range from 4.2 K down to 60 mK.Two-dimensional electron gas concentrations and mobilities were in the range of (1 -3) x 1011 cm-2 and(1 -3) x 104 cm2 /(V s), respectively.Corresponding to this the i = 1 quan- tum Hall effect plateau occurred at about 6 T magnetic field.Although fractional occupation numbers of about 0.3 were reached, no signs of fractional quantization were detected.Both current and frequency breakdown of the quantum Hall effect were investigated.Narrowing of the plateaus with increasing current differs from that measured in GaAs/AlGaAs structures because of the different mechanisms of dissipation.The fact that the magnetic length becomes smaller than the characteristic scale of the disorder seems to be essential in understanding the low frequency breakdown via the presence of quasi-classical electron states.