Carrier Concentration Dependence of Negative Longitudinal Magnetoresistance for n-InSb at 77 K

Abstract

Reliable dependences of negative longitudinal magnetoresistance (NLM) for n-type InSb on carrier concentration n and on mobility µ are investigated at 77 K up to 1.8 T with a number of specimens, whose n range from 5×1013 cm-3 to 4×1017 cm-3 and µ from 7×105 cm2/V·s to 4×104 cm2/V·s. The maximum NLM, ρ// (1.8 T)/ρ0∼0.5, occurs at n∼3×1015 cm-3 and correspondingly at µ∼2×105 cm2/V·s just before the occurrence of carrier degeneracy (n=4×1015 cm-3 at 77 K) in accordance with existing theories. NLM disappears with increasing n because of degeneracy, while it becomes less negative with decreasing n due to decreasing ionized impurity scattering and crystal inhomogeneity. The disappearance of NLM at n<1×1014 cm-3 is revived by the annealing process to remove inhomogeneity.