QUANTUM MAGNETOTRANSPORT IN INGAAS INP AT HIGH MAGNETIC-FIELDS AND LOW-TEMPERATURES/

Quantum Hall effect and Shubnikov-de Haas effect measurements were mad e in two-dimensional electron gas in liquid phase epitaxially grown Ga 0.47In0.53As/InP heterostructures in high magnetic fields in the tempe rature range from 4.2 K down to 60 mK. Two-dimensional electron gas co ncentrations and mobilities were in the range of (1 - 3) x 10(11) cm(- 2) and (1 - 3) x 10(4) cm(2)/(V s), respectively. Corresponding to thi s the i = 1 quantum Hall effect plateau occurred at about 6 T magnetic field; Although fractional occupation numbers of about 0.3 were reach ed, no signs of fractional quantization were detected. Both current an d frequency breakdown of the quantum Hall effect were investigated. Na rrowing of the plateaus with increasing current differs from that meas ured in GaAs/AlGaAs structures because of the different mechanisms of dissipation. The fact that the magnetic length becomes smaller than th e characteristic scale of the disorder seems to be essential in unders tanding the low frequency breakdown via the presence of quasi-classica l electron states.