Luminescence properties of GaP1−xNx alloys grown on nominally (001)-oriented GaP-on-Si substrates by chemical beam epitaxy

We investigate the optical properties of GaP1−xNx alloys, grown by chemical beam epitaxy (CBE) on (001)-oriented GaP-on-Si substrates, using cathodoluminescence and photoluminescence spectroscopy. In contrast to plasma-assisted molecular beam epitaxy, the optical properties of GaP1−xNx layers grown by CBE are found to be unaffected by ex situ rapid thermal annealing treatments. Regarding the effect of the N mole fraction, the luminescence intensity remains high for compositions up to the lattice match, then it decreases. Temperature-dependent measurements revealed the existence of two independent thermally activated quenching processes as well as the presence of localized states caused by compositional fluctuations. Upon extracting the long-range fluctuation energies, we derived a coupling coefficient value of 2.24 eV to describe the dependence of the band gap energy on x using the band anti-crossing model.