Extraction of density-of-states in amorphous InGaZnO thin-film transistors from temperature stress studies

•The Al2O3 gate insulator was fabricated by ALD.•The effect of active layer thickness on performance of IGZO TFT is studied.•The temperature instability has been investigated using the density-of-states.•The DOS was calculated based on the experimentally obtained activation energy.

The instability of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with different active layer thicknesses under temperature stress has been investigated through using the density-of-states (DOS). Interestingly, the a-IGZO TFT with 22 nm active layer thickness showed a better stability than the others, which was observed from the decrease of interfacial and semiconductor bulk trap densities. The DOS was calculated based on the experimentally-obtained activation energy (EA), which can explain the experimental observations. We developed the high-performance Al2O3 TFT with 22 nm IGZO channel layer (a high mobility of 7.4 cm2/V, a small threshold voltage of 2.8 V, a high Ion/Ioff 1.8 × 107, and a small SS of 0.16 V/dec), which can be used as driving devices in the next-generation flat panel displays.