Characterization of InP S-doped with Er by FFT photoreflectance

InP S-doped with erbium (Er) by organometallic vapour phase epitaxy (OMVPE) has been systematically investigated by room-temperature photoreflectance (PR) spectroscopy. The PR spectra are observed with many periods of Franz-Keldysh oscillation (FKO) above the band-gap energy due to an electric field existing in the epitaxial layer. Fast Fourier transform (FFT) is successfully applied to the PR spectra to calculate the electric field precisely from the FKO. The transformed spectra exhibit two peaks clearly. The main peak corresponds to the FKO, while the other peak to the split-off transition. The electric field deduced from FKO decreases with the increasing cap-layer thickness and the Er-exposure duration. Behaviours of the electric fields are discussed based on the existence of ErP