Beryllium-doped polycrystalline GaN films: Optical and grain boundary properties

Be-doped polycrystalline GaN films were deposited by radio frequency sputtering of a GaN/Be composite target onto fused silica substrates. The films were characterized by optical measurements, while the microstructural information was obtained from scanning electron microscopy, atomic force microscopy and X-ray diffraction studies. Grain boundary parameters like density of trap states ( Q t) and the barrier height ( E b) at the grain boundaries were estimated from the broadening of the absorption tail. Photoluminescence measurement at 80 K exhibited two strong transitions located ∼ 2.1 eV and ∼ 2.7 eV along with lower intensity peaks for band edge luminescence at ∼ 3.47 eV and 3.28 eV for films deposited at T = 423 K and 623 K, respectively.