Abstract: | Measurements of positron lifetime τ and of the shape parameter S of the Doppler-broadened annihilation line are used to study bulk and defect properties in GaP and GaAs1−xPx. τ and S decrease linearly with the composition x of GaAs1−xPx layers. A second lifetime component (τ2 = 290 ps) observed in as-grown GaP is attributed to stoichiometric P vacancies. After neutron irradiation of GaP and GaAs0.13P0.87 positrons are trapped by Ga vacancies (τ2 = 250 ps). These vacancies anneal out in two stages at 200–550 °C and 550–800 °C. |