Determination of excess phosphorus in low-temperature GaP grown by gas source molecular beam epitaxy

GaP films, epitaxially grown at a low temperature (LT) of ∼200°C by gas source molecular beam epitaxy, were reported recently to have excess phosphorus. In this letter, we report on the quantitative determination of the excess phosphorus in the LT films, using various approaches. Analytical scanning transmission electron microscopy, double-crystal x-ray diffraction, and particle-induced x-ray emission showed that the LT GaP films incorporated excess phosphorus of ∼0.6-2 at. %. The amount of excess phosphorus estimated from Raman scattering measurements, using the LO-TO phonon frequency splitting data of the as-grown LT GaP and bulk GaP, was in general agreement with those obtained from other techniques.