Photoinduced carrier transport mechanism in pn - and nn -GaN/GaON heterojunctions

Abstract

The unexpected high persistent photoconductivity effect in Ga2O3 material hinders the application of deep-ultraviolet photodetectors, while GaON can effectively avoid the effect caused by oxygen vacancies through anion engineering. As the behaviors of the carrier’s transport are crucial and essential to the photoelectric conversion processes, analysis of the carrier transport mechanism is helpful to propose feasible and effective strategies for high-performance photodetectors. In this work, GaN/GaON pn- and nn-heterojunctions with various thicknesses of GaON thin films were obtained by oxidizing the n-GaN and p-GaN films, and their photoinduced carrier transport mechanism has been comprehensively investigated. At a low bias, as the electric field is limited in the GaON layer and only the carriers generated in the GaON layer can be collected by the electrodes for both GaN/GaON pn- and nn-heterojunctions, the current increases linearly with an increase in the voltage. At a high bias, the electric field can affect the GaN/GaON heterojunction interface. For the GaN/GaON nn-heterojunction, the current continues to increase with increasing voltage as a small potential barrier is created between GaON and n-GaN to separate and transport the photogenerated carriers. However, for the GaN/GaON pn-heterojunction, the current increases slowly and then rapidly with an increase in the high voltage, because the electric field is not strong enough to help the carriers cross the potential barrier caused by the reverse GaN/GaON pn-heterojunction first and then overcome the barrier with a higher voltage.