Fabrication of an efficient GLAD-assisted p-NiO nanorod/n-ZnO thin film heterojunction UV photodiode

Abstract

The glancing angle deposition (GLAD) configuration in RF magnetron sputtering has been utilized to deposit p-type NiO nanorods, which are integrated with n-type ZnO thin film to realize a high performance p–n heterojunction diode for the efficient detection of UV photoradiation. The fabricated nano p-NiO/n-ZnO heterojunction shows excellent rectifying characteristics (rectification ratio ∼ 4 × 10³) with a very low reverse saturation current (∼10⁻¹⁰ A). The heterojunction photodiode exhibits a high current gain (3.71 × 10³), high photoresponsivity (3.24 × 10⁵ A W⁻¹), with a relatively fast response (∼200 ms) and recovery speed (∼25 ms) towards a very low UV intensity of 0.62 μW cm⁻² (λ = 300 nm). Recombination tunneling and space-charge limited current are the probable conduction mechanisms at low and high applied voltages respectively for the fabricated heterojunction diode. The observed high response speed and excellent responsivity of the diode towards deep-UV (λ = 300 nm) radiation might lead to potential military applications such as missile tracking, in addition to optical communications.