Characteristics Analysis of IGZO TFT and Logic Unit in the Temperature Range of 8–475 K

Abstract

The effect of high- and low-temperature conditions on the performance of IGZO TFT and logic circuits were investigated in this work. In the temperature range of 250−350 K, the performance of the IGZO TFT did not show significant changes and exhibited a certain degree of high- and low-temperature resistance. When the temperature was below 250 K, as the temperature decreased, the threshold voltage (VTH) of the IGZO TFT significantly increased, the field effect mobility (μFE) and the on state current (ION) significantly decreased. This is attributed to the lower excitation degree of charge carriers at extremely low temperatures, resulting in fewer charge carriers transitioning to the conduction or valence bands, and the formation of defects also limits carrier migration. When the temperature exceeded 350 K, as the temperature increased, more electrons could escape from the bandgap trap state and become free charge carriers, and the IGZO layer was thermally excited to produce more oxygen vacancies, resulting in higher μFE and lower VTH. In addition, the drain current noise spectral density of IGZO TFT conformed to the 1/ƒ noise characteristic, and the degradation mechanism of IGZO TFT over a wide temperature range was confirmed based on the changes in noise spectral density at different temperatures. In addition, an inverter logic unit circuit was designed based on IGZO TFT, and the performance changes over a wide temperature range were analyzed. This lays the foundation for IGZO TFT to be applied in integrated circuits with harsh environments.