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 (Qt) and the barrier height (Eb) 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.