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.