Fine structure of another blue luminescence band in undoped GaN

Abstract

A blue luminescence band, labeled BL3, has been found in undoped GaN samples grown by hydride vapor phase epitaxy. It has a maximum at 2.8 eV and a phonon-related fine structure at its high-energy side. The zero-phonon line of this band consists of a duplet with two sharp lines at 3.0071 and 3.0147 eV. Three phonon modes, including the LO mode with an energy of 91.3 meV and two pseudolocal phonon modes with energies of 39.6 and 68.2 meV, form the characteristic fine structure of the BL3 band. The BL3 band is attributed to internal transitions from excited states located near the conduction band to the 0/+ transition level of unknown defect. The defect is preliminarily identified as the RY3 center, which is also responsible for bright red-yellow luminescence bands in the studied samples.