Bulk and surface conduction by high-purity n-type InSb at low temperature when subjected to intense magnetic fields

Publisher Website
Google Scholar
Abstract
Measurements of the temperature dependence of the resistance of high-purity specimens of n-type InSb as a function of magnetic field are reported in the ranges T=4.2-0.3K and B=0-7.5 T. Unless the specimen is suitably etched, the huge increase of resistance with increasing magnetic field and falling temperature is limited by surface conductance, sometimes to a maximum resistance as low as approximately 100 k Omega . In this respect etching in H2O2/HF solution is more effective than in CP4-A. Bulk conduction is found to be governed by two activated components. The first is attributed to freeze-out of carriers from conduction band to donor states and the second to thermally activated hopping via donor sites. Energies controlling freeze-out seem to correspond to the transition 1s to 1p0 rather than 1s to CB. Hopping energies of a few tenths of a meV increase with magnetic field but slowly decrease with doping. As expected, the pre-exponential hopping parameter is a strong function of magnetic field and doping. Below approximately 0.8K, the temperature dependence of the hopping component becomes weaker in accordance with the increasing importance of long-range hopping. Surface conduction seems to be almost entirely controlled by an activation energy that depends strongly on the particular surface condition.