Electrical characteristics of thin-film transistors (TFTs) based on the solution-processed Zinc Tin Oxide (ZTO) channel layer

Abstract

Transparent amorphous metal oxide-based semiconductors have received significant attention since their inception by Hosono et al. Zinc tin oxide (ZTO), among others, has emerged as a promising candidate for indium-free semiconductors, enabling competitive device performance in comparison with its indium-based counterparts. High manufacturing costs pose an obstacle to the realization of modern large-area and mass-produced electronics. In contrast, the solution-processed deposition of semiconductor layers offers many advantages: simplicity, low-cost, and high throughput, still exhibiting performances more outstanding than conventional silicon in terms of their crucial performance parameters, such as charge-carrier mobility and current on−off ratio. Solution-processed Zinc Tin Oxide (ZTO) thin-film transistors were fabricated. Thin Film transistors TFTs )fabricated with alternating concentrations were found to have enhanced electrical characteristics. It was attributed to the decreased surface roughness, increased oxygen vacancies (acting as donors), and decreased M-OH (acting as traps) ratios as obtained from X-ray Photoelectron Spectroscopy (XPS) analysis. It was also conjectured that low concentration (0.05M) film at the bottom of the alternating concentration film was used as a nucleation layer and helped reduce interface traps. Secondly, ZTO films were subjected to Microwave (MW) assisted annealing for the microwave's different powers. Surface and electrical characterizations were performed. MW-assisted annealing showed reduced hydroxyl groups enhancing dihydroxylation and condensation of ZTO films and more oxygen vacancies produced via hydroxyl groups' decomposition during annealing the electrical characteristics of MW-assisted annealed films. Effects of gamma irradiation on ZTO thin films and TFTs were studied for the different dosages of gamma irradiation. Shifts in the threshold voltage (Vth), changes in the field-effect mobilities (µFE), transconductance (gm), saturation drain current (ID), donor concentration (Nd) were studied for samples irradiated for four weeks with a dose rate of 23.59 rad/sec with a total dose of about 57 MRad. The electrical parameters' changes were attributed to the combined effect of radiation-induced positive oxide traps and negative interface trap charges.