Magnetoresistance of proton irradiated Si0.97Ge0.03 whiskers

Abstract

Whiskers are a new material that is characterized by high structural perfection, chemical resistance and strength which reaches the theoretically possible limit for crystals of small transverse dimensions. The test whiskers were synthesized by the method of chemical transport reactions in a closed bromide system using gold as the initiator of growth. The crystals were irradiated by protons with an energy of 6MeV and doses of 5×1013, 1015 and 1×1017 p+/cm2 at 40°C in a U-120 cyclotron.The effects of proton irradiation and high magnetic fields on the magnetoresistance of Si1-xGex (x = 0,03) whiskers in the 4.2–300K temperature range has been studied. A slight decrease in the electrical resistance of the crystals in the 4.2–40K temperature range during irradiation with small proton doses and a significant increase in their resistance in the entire investigated temperature range for a dose of 1×1017 p+/cm2 have been found. The ionization energy of the impurity atoms in different magnetic fields has been calculated. It has been revealed that the energy level of the impurity depends on the magnetic field but slightly which in turn indicates a independence of the concentration of holes on the magnetic field. It has been shown that a significant magnetoresistance at all studied temperatures was due to the magnetic field-caused decrease in the mobility of free carriers (holes). It has been found that the concentration of holes depends on magnetic field but a little. Conclusion has been made about a negligible expansion of the band gap in magnetic fields of up to 8T.