The precise determination of the concentrations of defects at thermal equilibrium in Si and Ge by means of simultaneous measurements of positron annihilation and positron diffusion characteristics

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Fort the purpose of precise determination of the concentrations of defects at thermal equilibrium in Si and Ge, the positron annihilation and positron diffusion characteristics were measured as a function of temperature. After constructing the ultra short pulse monoenergetic positron beam in FY1997 and installation of a heating system based on ultra-red light in FY1998, the measurements of positron annihilation characteristics were measured between 300K and 1200K in Ge, and between 300K and 1600K in Si, respectively. In Ge, although the positron annihilation characteristics showed a nearly constant behavior between 300K and 600K and started a slight change above 600K, the diffusion length of positrons showed a big decrease between 300K and 600K and kept a constant value above 600K.In Si, the overall temperature dependence was found to be nearly the same as that in Ge except for the shift to the higher temperature. region as compared with Ge. On the defects at high temperatures at therm … More al equilibrium in Si, two observations reported contradictory results ; one is based on the internal ^<22>Na source produced by proton irradiation, the other is based on the beta gamma coincidence technique using the Pelletron accelerator. The present result is in good agreement with the latter investigation. From the precise result of the present work, it was concluded that the observed results in the former experiment should be due to the growth of vacancy clusters at high temperatures. From the precise analyses of the present results, the observed small change in positron annihilation characteristics in intermediate temperature region was attributed to the presence of self-trapping effect due to positron-lattice coupling.In order to obtain the information on the thermal equilibrium defects, the slow cooling of FZ-, Cz- and Hydrogen-annealed- Si wafers from the high temperature near the melting was examined by the 2D-ACAR measurements. As a result, in the order of contained concentration of oxygen atoms, small oxide precipitates, oxygen substitutional atoms, vacancy-oxygen complexes, and divacancies were observed in the concentration of the order of 10^<15>-10^<16>cm^<-3>. Less