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.

Automated summary

This paper describes a CMOS process based on the sol-gel method for temperature compatible (400 degrees C) integrated circuits. The properties of aluminum-doped zinc oxide (AZO) thin films were investigated, and it was found that the electrical resistivity is related to the orientation and aluminum content. This research is of great significance for next-generation flexible, microsystem, and optoelectronic devices.