Laser Crystallization of Transparent AZO Films on Sapphire With High Electron Mobility for Photo-Application

Transparent and conductive alumina-doped ZnO (AZO) films were deposited on sapphire substrates at room temperature by room temperature pulsed laser deposition (PLD) and then followed by laser crystallization at 500K. As implied by the Multiphysics Simulation, X-ray diffraction spectra and morphological characterizations show grain growth and crystallinity enhancement during the crystallization process, resulting in less film internal imperfections. With lower internal defects, higher conductivity and transmittance were expected. Electrical and optical measurements show that the crystallization process dramatically improves the electron mobility and conductivity while the carrier concentration decreases, which in turn increases infrared transmittance. Under an optimal laser crystallization condition, AZO films with low resistivity of 9.90×10⁻⁴ Ω-cm and a high electron mobility of 79 cm²/Vs. UV-Vis-IR transmittance spectrum shows the laser crystallization significantly enhanced the AZO film transparency to 6000nm with over 60% transmittance. And the crystallized AZO film shows 36% higher transmittance than room temperature PLD deposited AZO film over 900–5000nm wavelength range.