Effect of Annealing Method on Vacancy-Type Defects in Si-Implanted GaAs Studied by a Slow Positron Beam

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The effect of annealing encapsulants on the activation of Si implanted into GaAs was studied by slow positron beam annihilation. For encapsulants, two kinds of silicon nitrides and silicon dioxide were used and capless annealing under arsine ambient was performed for reference purposes. From the measurements of the Doppler-broadened profiles of the positron annihilation as a function of the incident positron energy, gallium vacancy concentrations were estimated. It was found that silicon dioxide cap annealing includes a high concentration of gallium vacancies, which is approximately 2.5 times larger than that for silicon nitride annealing and four times that for capless annealing. With the electrical measurement, the out-diffusion of Ga into the cap insulator film was found to have no enhancing effect on electrical activation.