CMOS Compatible Al-Doped ZnO Sol-Gel Thin-Film Properties

Zinc oxide (ZnO) is a low-cost class of n-type inorganic semiconductors with a large exciton binding energy (approximate to 60 meV), wide direct bandgap (3.37 eV), and the most important material for various fields of industrial and deep-tech applications. Herein, a complementary metal-oxide-semiconductor (CMOS) temperature compatible (400 degrees C)- integrated circuit (IC) process based on the sol-gel method is described. The properties of aluminum (Al)-doped ZnO (AZO) thin films were investigated. The Al content, Al/(Al+Zn) ratio, varies from 0 to 10% and exhibits compressive stresses from -4 to -1.8 GPa. At low dopant concentrations, the Al content acts as an electrical dopant, while at higher dopant concentrations, it acts as an impurity. The electrical resistivity, which was only 3 x 10(-3) omega cm, is inversely related to the orientation of the thin film, which was preferably along the (0 0 2) direction. The optical bandgap energy of AZO thin films was determined to be in the range of 3.34-3.87 eV. Herein, a novel method to change the Al content of doped AZO thin films to improve their properties is described, which is suitable for next-generation flexible, microsystem, and optoelectronic devices.