Annealing behaviour of GaAs implanted with 70 MeV 120Sn ions

摘要

Single crystal GaAs substrates implanted with 70 MeV 120Sn have been investigated by X-ray diffraction (XRD) and electrical resistance measurements after annealing in the temperature range 373-823 K. XRD measurements for the samples annealed up to 723 K show two peaks, one due to the substrate and another due to the implant damaged layer. The strain parameter from the measured separation between the substrate and layer peaks of several symmetric and asymmetric reflections after each annealing step has been calculated. Strain recovery occurs in two predominant annealing stages, one at about 500 K and the other at about 700 K. Temperature dependence (100-300 K) of resistance of these samples indicates that electrical conduction in the samples annealed up to 723 K, is dominated by variable range hopping. Localized states density at the Fermi level N(EF), estimated from temperature dependence of sample resistance after each annealing step, shows two annealing stages similar to those observed from XRD measurements. Isothermal annealing carried out at two different annealing temperatures (523 and 573 K) indicates the activation energy Ea = 0.16 eV for the first annealing stage.