  Achieving efficient and stable ultraviolet emission is a challenging goal in
optoelectronic devices. Herein, we investigate the UV luminescence of zinc
germanate Zn2GeO4 microwires by means of photoluminescence measurements as a
function of temperature and excitation conditions. The emitted UV light is
composed of two bands (a broad one and a narrow one) associated with the native
defects structure. In addition, with the aid of density functional theory (DFT)
calculations, the energy positions of the electronic levels related to native
defects in Zn2GeO4 have been calculated. In particular, our results support
that zinc interstitials are the responsible for the narrow UV band, which is,
in turn, split into two components with different temperature dependence
behaviour. The origin of the two components is explained on the basis of the
particular location of Zn_i in the lattice and agrees with DFT calculations.
Furthermore, a kinetic luminescence model is proposed to ascertain the
temperature evolution of this UV emission. These results pave the way to
exploit defect engineering in achieving functional optoelectronic devices to
operate in the UV region.

Materials Science