Structural and optical characterizations of InPBi thin films grown by molecular beam epitaxy

InPBi thin films have been grown on InP by gas source molecular beam epitaxy. A maximum Bi composition of 2.4% is determined by Rutherford backscattering spectrometry. X-ray diffraction measurements show good structural quality for Bi composition up to 1.4% and a partially relaxed structure for higher Bi contents. The bandgap was measured by optical absorption, and the bandgap reduction caused by the Bi incorporation was estimated to be about 56 meV/Bi%. Strong and broad photoluminescence signals were observed at room temperature for samples with x (Bi) < 2.4%. The PL peak position varies from 1.4 to 1.9 mu m, far below the measured InPBi bandgap.