Band engineering and enhanced photoluminescence via Al donor doping in ZnO thin films

Abstract

Al-doped zinc oxide (AZO) compatible with silicon planar processes were fabricated using a sol-gel method, and their optical properties, with a particular emphasis on luminescence performance and bandgap engineering, were systematically investigated. Analysis of transmission spectra revealed a blue shift in the bandgap of AZO films with increasing Al doping concentration, demonstrating bandgap controllability through doping regulation. Photoluminescence (PL) spectra exhibited dual visible emission peaks at 485 (bluish-green) and 527 nm (green), where the 1 % doping concentration achieved optimal luminescence intensity by balancing defect-mediated recombination and carrier transport. Through the analysis of the PL spectra, we have identified that the visible - light emission peaks at 485 and 527 nm originate from oxygen vacancies and are attributed to the substitution of Al for Zn, respectively. Additionally, based on the PL spectra, we have determined the position of the donor energy level, which is located 1.02 eV below the bottom of the conduction band.