Electrical stability enhancement of GeInGaO thin-film transistors by solution-processed Li-doped yttrium oxide passivation

Low-temperature fabrication of an HfO2 passivation layer for amorphous indium–gallium–zinc oxide thin film transistors using a solution process

“…The 150 °C-annealed a-IGZO TFT with PMMA passivation, which is a commonly-used organic passivation layer, showed proper switching characteristic, as reported previously 11 , 12 . However, the a-IGZO TFT with Y 2 O 3 passivation, which is the most widely studied solution-processed passivation among inorganic materials, showed no switching characteristic, while the a-IGZO TFT with HfO 2 passivation showed proper switching characteristic 13 – 15 . This indicated that the thermal energy at the annealing temperature at 150 °C was insufficient for the Y 2 O 3 precursor solution to form a passivation layer, which resulted in an excess carrier concentration in the channel layer 13 .…”

“…The oxygen vacancy (V o ) in the channel layer can act as a trap site and lead to PBS instability 15 , 29 . Hence, XPS depth analyses for the channel layers of the a-IGZO TFTs without passivation and with the HfO 2 passivation layer were also made, to confirm additional benefits of the solution-processed HfO 2 passivation.…”

“…In this study, a solution-processed hafnium oxide (HfO 2 ) passivation layer was fabricated at low temperature (150 °C) using an aqueous solution of hafnium chloride (HfCl 4 ) because strongly hydrated HfCl 4 decomposes and transforms into HfO 2 at lower temperature than anhydrous HfCl 4 . The electrical characteristics and stability of the indium–gallium–zinc oxide (a-IGZO) TFT with HfO 2 passivation were compared with those of a-IGZO TFTs without passivation, and with the commonly used PMMA and Y 2 O 3 passivation 11 – 15 . Thermogravimetric analysis and differential scanning calorimetry (TGA/DSC) and X-ray photoelectron spectroscopy (XPS) analysis of the HfO 2 passivation layer verified the formation of the HfO 2 passivation layer at 150 °C.…”