Photoluminescence of GaN grown by molecular-beam epitaxy on a freestanding GaN template

Abstract

Photoluminescence (PL) studies were performed on a 1.5-μm-thick GaN layer grown by molecular-beam epitaxy on a freestanding GaN template that in turn was grown by hydride vapor-phase epitaxy. PL spectra from both the epilayer and the substrate contain a plethora of sharp peaks related to excitonic transitions. We identified the main peaks in the PL spectrum. Taking advantage of the observation of donor bound exciton peaks and their associated two-electron satellites, we have determined the binding energies of two distinct shallow donors (28.8 and 32.6 meV), which are attributed to Si and O, respectively.