Origin of Ambipolar Behavior in p-Type Tin Monoxide Semiconductors: Impact of Oxygen Vacancy Defects

Abstract

In this study, we examine the effect of oxygen vacancies (V-O) near the back surface of p-type tin monoxide (SnO) semiconductors on the device performance of its thin-film transistors (TFTs). Non-stoichiometry of the SnO surface layer was controlled through oxidant exposure conditions during alumina (Al2O3) growth using plasma-enhanced atomic layer deposition (PEALD). During the initial period of Al2O3 deposition, trimethylaluminum precursorsabsorbedoxygenfromthe SnOlayer and created the V-O, which can form a V-O-rich region at the Al2O3/SnO interface. By modulating the oxygen plasma density during the PEALD process, the V-O was effectively controlled, allowing the electrical characteristics to transition from ambipolar behavior to p-channel only conduction. This study demonstrates the importance of the back surface of SnO, suggesting a new perspective of ambipolar behavior in p-type SnO semiconductors.