Electrical Performance and Stability Improvement of p-Channel SnO Thin-Film Transistors Using Atomic-Layer-Deposited Al₂O₃ Capping Layer

The incorporation of an atomic-layer-deposited Al
₂
O
₃
capping layer was proposed as an effective method to enhance the electrical performance and stability of p-channel SnO thin-film transistors (TFTs). The SnO TFT with the Al
₂
O
₃
capping layer demonstrated better electrical characteristics, such as higher field-effect mobility (μ
_FE
= 1.7 cm
²
/V·s), smaller subthreshold swing (SS = 2.9 V/dec), and larger current on/off ratio (ION/OFF = 1.6 × 10
⁴
), than the pristine SnO TFT (μ
_FE
= 1.5 cm
²
/V·s, SS = 3.8 V/dec, and I
_ON/OFF
= 6.9 × 10
²
). Furthermore, the Al
₂
O
₃
-capped SnO TFT exhibited significantly enhanced electrical stability under an applied negative-gate-bias stress compared to the pristine device. The observed phenomena were mainly attributed to the decreased number of oxygen-vacancy-induced hole trap states within the SnO owing to diffused hydrogen from the atomic-layer-deposited Al
₂
O
₃
layer. Our experimental results thus demonstrate that incorporating the atomic-layer-deposited Al
₂
O
₃
capping layer is a simple and effective method for improving the electrical characteristics of p-channel SnO TFTs.