Heterojunction Wide-Bandgap Amorphous Metal Oxide High-Voltage Thin-Film Transistors with High Driving Current and Low Process Temperature

The implementation of high-voltage (HV) applications in monolithic integration has led to increased demand for wide-bandgap high-voltage thin-film transistors (HVTFTs) to solve voltage mismatch problems between HV devices and complementary metal oxide semiconductor (CMOS) integrated circuits. However, typical HVTFTs possess several limitations, including low driving current due to the drain offset structure and high process temperature (>300 °C), limiting high-frequency switching operation and flexible substrate compatibility, thus impeding their application in flexible and wearable HV electronics. This study presents heterojunction wide-bandgap channel-based HVTFTs fabricated using amorphous indium tin zinc oxide (a-ITZO) and indium gallium zinc oxide (a-IGZO) to overcome the limitations of the current HVTFTs. Owing to the heterojunction channel layer, we achieved a much higher driving current of >0.37 mA/mm (ID/W) at VGS = 210 V and VDS = 5 V with a flexible-electronics-compatible channel layer annealing temperature (150 °C), indicating that the TFTs can be even applied in HV flexible/wearable electronics. Therefore, ITZO/IGZO TFTs can withstand considerably higher power than single-layer IGZO HVTFTs, while exhibiting similar HV breakdown characteristics. Additionally, the ITZO/IGZO HVTFTs demonstrate superior electrical stability under high-voltage-bias conditions compared to conventional IGZO HVTFTs. Thus, heterojunction amorphous metal oxide TFTs are suitable for fast switching flexible HV electronic systems while gate-controlled by CMOS technologies.