Influence of N2/O2 partial pressure ratio during channel layer deposition on the temperature and light stability of a-InGaZnO TFTs

Abstract

The electrical characteristics of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) deposited with different N2/O2 partial pressure ratios (PN/O) are investigated. It is found that the device with 20% PN/O exhibits enhanced electrical stability after positive-bias-stress temperature (PBST) and negative-bias-stress illumination (NBSI), presenting decreased threshold voltage drift (ΔVth). Compared to the N-free TFT, the average effective interface barrier energy (Eτ) of the TFT with 20% PN/O is increased from 0.37 eV to 0.57 eV during the bias-stress process, which agrees with the suppressed ΔVth from 3.0 V to 1.12 V after the PBS at T = 70 °C. X-ray photoelectron spectroscopy analysis revealed that the enhanced stability of the a-IGZO TFT with 20% PN/O should be ascribed to the control of oxygen vacancy defects at the interfacial region.