Photon recycling as the dominant process of luminescence generation in an electron beam excited n-InP epilayer grown on an n(+)-InP substrate

We examine the room-temperature dispersive and non-dispersive cathodoluminescent (CL) signals produced by an n-InP/n(+)-InP homojunction as a function of excitation beam energy. The non-intentionally doped epilayer of the homojunction is thick enough (2.5 mu m) that it can be investigated independently of the substrate by choosing beam energies lower than 25 keV. The red-shift of CL peak, as well as the drastic change of the shape of the CL spectra, observed when increasing the beam energy, are explained in terms of photon recycling. The luminescence of the epilayer is found to be governed by the recycling of photons originating from the substrate. This leads to an increase of the external luminescence efficiency of the epilayer compared with that expected in homojunctions with undoped substrates. We also present a determination of the diffusion-recombination parameters of the structure.