title: Violet-blue LEDs based on p-GaN/n-ZnO nanorods and their stability.
abstract: In this paper, we report a fabrication, characterization and stability study of p-GaN/n-ZnO nanorod heterojunction light-emitting devices (LEDs). The LEDs were assembled from arrays of n-ZnO vertical nanorods epitaxially grown on p-GaN. LEDs showed bright electroluminescence in blue (440 nm), although weaker violet (372 nm) and green-yellow (550 nm) spectral components were also observed. The device characteristics are generally stable and reproducible. The LEDs have a low turn-on voltage (∼5 V). The electroluminescence (EL) is intense enough to be noticed by the naked eye, at an injection current as low as ∼ 40 µA (2.1 × 10(-2) A cm(-2) at 7 V bias). Analysis of the materials, electrical and EL investigations point to the role of a high quality of p-n nano-heterojunction which facilitates a large rectification ratio (320) and a stable reverse current of 2.8 µA (1.4 × 10(-3) A cm(-2) at 5 V). Stability of EL characteristics was investigated in detail. EL intensity showed systematic degradation over a short duration when the LED was bias-stressed at 30 V. At smaller bias (<20 V) LEDs tend to show a stable and repeatable EL characteristic. Thus a simple low temperature solution growth method was successfully exploited to realize nanorod/film heterojunction LED devices with predictable characteristics.
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon Tong, Hong Kong.
authors.forename: Shrawan
authors.initials: S
authors.lastname: Jha
authors.forename: Jin-Cheng
authors.initials: JC
authors.lastname: Qian
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Kutsay
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Kovac
authors.forename: Chun-Yan
authors.initials: CY
authors.lastname: Luan
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Zapien
authors.forename: Wenjun
authors.initials: W
authors.lastname: Zhang
authors.forename: Shuit-Tong
authors.initials: ST
authors.lastname: Lee
authors.forename: Igor
authors.initials: I
authors.lastname: Bello