Ion beam-induced and thermal reactions at Fe:GaAs interface

Ion beam-induced and thermal reactions at Fe:GaAs interface are studied by using conversion electron Moessbauer spectroscopy and small angle X-ray diffraction measurements. A thin film of Fe (enriched to 30% in 57Fe Moessbauer isotope) was deposited in UHV environment on <100> oriented semi-insulating GaAs substrates. Some of the samples were ion-mixed by 130keV Ar+ ions at dose values of 3x1015 and 1016ions/cm2. The asdeposited and ion-mixed samples were annealed at different temperatures up to a maximum of 500degC. It was observed that ion mixing led to precipitation of disordered and/or defective binary phase along with ferromagnetic Fe3GaAs ternary phase which upon vacuum annealing at 500degC for 1 h leads to a mixture of structurally well-defined Fe3Ga, FeAs and FeAs2 phases. The combined analysis of Moessbauer and X-ray data is shown to reveal the location of the phases below the samples surface. The mechanism for phase formation and associated reaction kinetics at Fe/GaAs interface is discussed in the light of the experimental results. (author). 25 refs., 5 figs., 1 tab