Switching Mechanism behind the Device Operation Mode in SnO‐TFT

Abstract Oxide semiconductor‐based complementary inverter technology is one of the crucial topics to advance oxide device technology to the next stage of development. However, the absence of high‐performance p‐channel oxide thin‐film transistor (TFT) hinders the development of oxide‐complementary inverter circuit. Tin monoxide (SnO) is a promising oxide semiconductor to develop not only p‐channel but also ambipolar oxide TFTs. However, the understanding of device operation mode in SnO‐TFT is still insufficient to control the TFT operation modes and to further improve the device performance. The origin of switching mechanism behind the different operation modes in SnO‐TFT is clarified by performing back‐channel defect engineering. It is found that back‐channel subgap defects that involve deep donor‐like and deep acceptor‐like states control the device operation modes of SnO‐TFT. High‐density defects remove the ambipolarity from SnO‐TFT and make the device to only operate in p‐channel mode. ALD‐Al 2 O 3 passivation effectively reduces these defects and produces good ambipolar SnO‐TFTs with p‐channel mobility of ≈1.2 cm 2 V −1 s −1 and n‐channel mobility of ≈0.03 cm 2 V −1 s −1 , respectively. The complementary‐like inverter is fabricated using two identical ambipolar SnO‐TFTs and exhibits the voltage gain of 64.1 ± 12.0 and 48.8 ± 6.8 for the first and third quadrants, respectively.