Growth characteristics and properties of Ga-doped ZnO (GZO) thin films grown by thermal and plasma-enhanced atomic layer deposition

The growth characteristics and electrical and optical properties of gallium-doped ZnO (GZO) grown by thermal atomic layer deposition (Th-ALD) and plasma-enhanced atomic layer deposition (PE-ALD) were investigated as a function of key growth parameters including the growth temperature. While GZO films are generally deposited at high growth temperatures above 300 °C, room temperature deposition is possible using PE-ALD. The chemical properties of the films were analyzed by X-ray photoelectron spectroscopy and their electrical properties including the carrier concentration, mobility, and resistivity were investigated by Hall measurements. The lowest resistivity of 1.49 × 10−3 Ω cm was obtained for the Th-ALD GZO film grown at 300 °C. The transmittance was enhanced to over 85% in the visible light range when Ga was doped on a ZnO film. In addition, a GZO bottom-gated thin film transistor (TFT) was fabricated and exhibited good electrical properties.