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

Ga 2 O 3 (1 wt%)-doped ZnO (GZO) thin films were deposited on α-Al 2 O 3 (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 N 2 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 Ω·cm with 3.9×10 20 /cm 3 carrier concentration and exceptionally high mobility of 60 cm 2 /V·s. These improved physical properties are explained in terms of the translation of doped-Ga atoms from interstitial to substitutional sites.