Effect of light illumination on the low-frequency noises in amorphous-IGZO TFTs

Abstract

We investigate the low frequency noise (LFN) behaviors of the amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) under light illumination. The LFNs are measured after the illumination of light with various wavelengths, and the measured data shows that the normalized noise spectral density (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">id</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) significantly decreases after the illumination of blue light. This phenomenon can be attributed to the increased number of carriers after the illumination of blue light in a-IGZO TFTs. In some devices, we found that the transfer curve and the S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">id</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> significantly changes when source and drain biases are exchanged. The exact mechanism causing this phenomenon is not exactly known yet, but the different Schottky barrier height between source/a-IGZO interface and drain/a-IGZO interface is considered as a possible cause of this phenomenon. We also found that the Schottky contact noise from the contact can be significantly reduced by illuminating the blue light on the contact region in a-IGZO TFTs.