Hopping conduction in n-type indium antimonide below 1 k

Abstract

Abstract Measurements of the longitudinal and transverse resistivity of n-type indium antimonide in magnetic fields up to 40 kG and for temperatures down to 30 mK are described. The resistivity is given by the relation p1 exp (E 1/kT) + p 3 exp (E 3/kT) + p 0 exp (T 0/T) x where for T > 1 K the first term, arising from the freeze-out of the electrons, is important; for 1 K T < 0·3 K the second term, associated with activated hopping, dominates; and for T < 0·3 variable-range hopping, given by the third term, is important. Expressions for x and T 0 in the variable-range-hopping region have been derived assuming the density of states at the Fermi energy (a) is a constant and (b) varies with energy as C ϵ 2. Donor wavefunctions given either by Yafet, Keyes and Adams (1956) or by Hasegawa and Howard (1961) are considered in both cases. The best fit to the results is obtained with a constant density of states and Yafet, Keyes and Adams wavefunctions. The measured values of T 0 are, however, much lower than the...