HALL MEASUREMENTS OF THE INSULATING PHASES AT NU=1.5 AND NU-SIMILAR-TO-0.5 IN P-TYPE SI SI1-XCEX HETEROSTRUCTURES USING PULSED MAGNETIC-FIELDS/

Low temperature (0.3 K) Hall resistivities (rho(xy)) of the two dimens ional hole system in high quality p-type Si/Si1-xGex single heterojunc tions have been measured in pulsed magnetic fields to 50 T. Clean Hall measurements are obtained by subtracting the raw signals from four se parate field pulses. Hall data are presented in the Landau level filli ng factor regime upsilon = 1.5 where we have previously identified an insulating phase (IP). This IF, characterised by a rapid increase in r ho(xx) as T --> 0 K and non-linear I-V measurements, is shown to incre ase at large tilt angles. The corresponding Hall resistivity in the IP region, measured in tilted pulsed magnetic fields, remains finite and close to the classical value. Preliminary pulsed magneto-transport re sults are presented for a second IP which indicate that both rho(xx) a nd rho(xy) increase dramatically for upsilon < 0.5. (C) 1998 Elsevier Science B.V. All rights reserved.