High positive magnetoresistance in Ge films at low temperatures

Abstract

High positive magnetoresistance is found and investigated in p-Ge films on GaAs at low temperatures (1.4–4.2 K) and in magnetic fields up to 14 T. The film resistance grows exponentially with magnetic field. At a temperature of 1.4 K and in a magnetic field of 14 T, the film resistance is increased by a factor of 3.8. The magnetoresistance also grows exponentially as temperature is reduced. The Mott variable-range hopping conduction is observed in the films studied in the 1.4–21 K temperature range. It is shown that experimentally observed magnetoresistance agrees well with the theory of compression of wave functions of the localized states in the plane normal to magnetic field. This results in reduction of their overlapping, decrease of electron tunneling probability, and consequently, considerable growth of film resistance. Based on experimental resistance dependences on temperature and magnetic field, the parameters of hopping resistivity in Ge films on GaAs are determined. A possibility of transition to interference effects in conduction leading to localization of charge carriers and negative magnetoresistance at temperature decrease is also discussed.