Oxygen Plasma Treatment-Improved Source/Drain Contact Property for Achieving High-Performance ZnO Transistors

Oxide transistors are of increasing interest in the field of integrated circuits. In this work, we explore the effects of oxygen plasma treatment on source/drain (S/D) region contact property of the ZnO transistors. Through film characterization, we found that oxygen plasma treatment process not only helps to improve surface morphology of the S/D region but also increases the oxygen vacancies in the ZnO active layer of the device. This suggests the promotion of bonding between the ZnO active layer and the Al S/D electrode, thus reducing the contact barrier and contact resistance. With an oxygen plasma treatment time of 2 min, a distinct decrease of 96.50% in the S/D resistance (R $_{\mathbf {c}}$ ) is achieved, and electrical performance of the ZnO transistors obtains comprehensive improvement. The major properties of the optimized ZnO transistors include a field-effect mobility of 39.56 cm2/Vs, an on-to-off current ratio of ${2}.{89}\times {10}^{{{7}}}$ , a sub-threshold swing of 103.01 mV/decade, and a threshold voltage of -0.50 V. Our work provides an effective strategy to fabricate high-performance ZnO transistors.