There is a need for a good quality thin film diode using a metal oxide p–n heterojunction as it is an essential component for the realization of flexible large‐area electronics. However, metal oxide‐based diodes normally show poor rectification characteristics whose origin is still poorly understood; this is holding back their use in various applications. A systematic study of the origins of the poor performance is performed based on bias‐stress measurements using a cuprous oxide (Cu2O)/amorphous zinc‐tin oxide (a‐ZTO) heterojunction as an example. This suggests that multiple carrier trapping and thermal release of carriers in defect states stemming from oxygen vacancies at the heterojunction interface is the primary cause of poor rectification. It is demonstrated that a plasma treatment is an effective way to optimize the population of oxygen vacancies at the heterojunction interface based on extensive material analyses, allowing a significant improvement in the diode performance with a much‐enhanced rectification ratio from ≈20 to 10 000, and a consequent facilitation of the next‐generation of ubiquitous electronics.

No abstract

hydrogenated amorphous silicon (a-Si:H) for the active channel layer used in thin film transistors (TFTs) for display back planes. [1] This is due to the higher mobility of AOSs compared to a-Si:H, and AOSs can be deposited at room temperature with excellent uniformity, thus opening potential applications such as flexible electronics, sensors, displays, and radio frequency identification tags. In addition to TFTs, AOSs have been incorporated in fundamental devices such as p-n junction diodes, with a variety of combinations of n-type and p-type oxide films. Example of oxide-based diodes include NiO x /ZnO fabricated using pulsed laser deposition (PLD) at up to 650 °C [2] showing rectification of 2.6 × 10 10 , Cu 2 O/Ga 2 O 3 made by thermal oxidation of copper at 1010 °C and PLD at room temperature (RT) exhibiting rectification of 4 × 10 4 , [3] Cu 2 O/indiumgallium-zinc oxide (IGZO) by magnetron sputtering at RT rectifying with ratio 3.4