Understanding the Role of Temperature and Drain Current Stress in InSnZnO TFTs with Various Active Layer Thicknesses

Thin-film transistor (TFT) devices composed of metal oxide semiconductors have attracted tremendous research attention globally in recent years. Owing to their ability to offer mobility, metal oxide semiconductor materials can enable high-performance TFTs for next-generation integrated display devices. Nevertheless, further breakthroughs of metal oxide TFTs are mainly obstructed by their long-term variability, the reason for which is not yet fully understood. Herein, TFTs based on InSnZnO (ITZO) with various thicknesses (T-ITZO) were prepared and their long-term stabilities under test temperatures and drain current stress were investigated. The results indicate that ITZO TFTs exhibit outstanding electrical properties regardless of the T-ITZO, including a high saturated mobility of over 35 cm(2)V(-1)s(-1) and sharp subthreshold swing. Note that the transfer and output characteristic curves of the device with a thick T-ITZO of 100 nm express an abnormal current surge when high gate and drain voltages are exerted, which is attributed to the floating body effect, caused when the imposed electric field induces impact ionization near the drain side. More interestingly, these drain current stress results further suggest that the abnormal shift behavior of the electrical properties of the ITZO TFTs with a T-ITZO of greater than 75 nm is observed to deteriorate gradually with increasing temperature and drain current bias. This study addresses that such a degradation effect should be restrained for the operation of high-mobility devices.