Enhanced temperature and light stability of amorphous indium-gallium-zinc oxide thin film transistors by interface nitrogen doping

The electrical characteristics of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) with an ultrathin nitrogenated a-IGZO (a-IGZO:N) layer embedded at the channel/gate dielectric interface are investigated under positive gate-bias stress temperature (PBST) and negative bias illumination stress (NBIS). The devices with a-IGZO:N layer show enhanced electrical stability, with significantly reduced threshold voltage shift. Meanwhile, it is found that the average effective energy barrier for the positive gate-bias stress process in the TFTs with a-IGZO:N layer increases, which causes fewer channel carriers trapped in the channel/gate dielectric interface or insulator. According to x-ray photoelectron spectroscopy analyses, the concentration of oxygen vacancies (O_V) is reduced when nitrogen is incorporated into the a-IGZO films. Therefore, the improved electrical stability of the a-IGZO TFTs upon PBST and NBIS is attributed to the reduction of interface O_V-related defects by nitrogen doping.