Jung Cho

Enhancement of Photoluminescence and Electrical Properties of Ga-Doped ZnO Thin Film Grown on α-Al2O3(0001) Single-Crystal Substrate by rf Magnetron Sputtering through Rapid Thermal Annealing

Ga2O3 (1 wt%)-doped ZnO (GZO) thin films were deposited on α-Al2O3(0001) by rf magnetron sputtering at 550°C and a polycrystalline structure was obtained. As-grown GZO thin films show poor electrical properties and photoluminescence (PL). For the improvement of these properties, GZO thin films were annealed at 800–900°C in N2 atmosphere for 3 min. After rapid thermal annealing, deep-defect-level emission disappears and near-band emission is greatly enhanced. Annealed GZO thin films show very low resistivity of 2.6×10-4 Ωcm with 3.9×1020/cm3 carrier concentration and exceptionally high mobility of 60 cm2/Vs. These improved physical properties are explained in terms of the translation of doped-Ga atoms from interstitial to substitutional sites.

Effects of H 2 Annealing Treatment on Photoluminescence and Structure of ZnO : Al / Al2 O 3 Grown by Radio-Frequency Magnetron Sputtering

Al-doped zinc oxide (AZO) thin films have been grown on Al 2 O 3 (0001) substrate by radio-frequency (rf) magnetron sputtering at 550°C. The AZO films have been annealed by a rapid thermal process in H 2 exposure with a temperature range of 600-1000°C. Effects of hydrogen on the AZO films have been investigated using photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The as-grown AZO film shows only broad deep defect-level PL. After annealing at 600°C, deep defect-level emission is quenched and near-band-edge (NBE) emission is observed at around 382 nm (3.2 eV), which can be explained by the H 2 passivation effect. At elevated temperature, two interesting peaks corresponding to violet (406 nm, 3.05 eV) and blue (436 nm, 2.84 eV) emissions have been observed for the first time in annealed AZO thin films. Incorporation of hydrogen and formation of oxygen deficient in annealed AZO films have been studied using XPS. Surface morphology and microstructure of AZO films have been carried out by SEM.