ACTIVATION-ENERGY AND HALL-COEFFICIENT MEASUREMENTS IN LIGHTLY DOPED N-INP IN THE THERMAL FREEZE-OUT REGION

The direct-current resistivity, rho, and Hall coefficient, R(H), of lightly doped n-type InP samples were measured at temperatures (T) down to 12 K and magnetic fields up to 4.8 kG. A sharp exponential increase in rho, as T was decreased, was observed for temperatures below 80 K. The Hall coefficient showed a similar trend, i.e. R(H) increased sharply as T was reduced below 80 K. This is attributed to the freeze-out of conduction electrons onto their donor sites. The donor activation energy, E(d), calculated from the temperature dependence of the resistivity, was less than the theoretical prediction. An enhanced dielectric constant would be a possible candidate for such behaviour. The initial decrease in rho (as T is reduced) recorded in the higher-temperature region is due to impurity scattering probably combined with lattice scattering.