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.

Recent Advances in Metal Halide‐Based Perovskite Light‐Emitting Diodes

“…[8] Thec olor of EL can be controlled by suitable tuning of the bandgap.I ninorganic semiconductors,t he bandgap can be tuned from UV/Vis to near infrared (NIR)b yu sing the alloying method (see Figure 1). Inorganic semiconductors have al ong life time and stability but are still color impure (e.g.,G aN and InGaN-based LEDsh ave ag reen emission band along with the characteristic blue emission) [9][10][11] and require expensive high-temperature,h igh-vacuum-basedp rocesses for fabrication.I nt he meantime,r esearcherss tarted working on low-cost solution-processable organic semiconductors (polymersa nd small molecules) as emissive layer for LEDs (organic LEDso rO LEDs). In the 1950s,E Lw as observed by Bernanosee tal.…”

High-Resolution Light-Emitting Diode Array Based on an Ordered ZnO Nanowire/SiGe Heterojunction

“…Since the fabrication of heavily doped p-type ZnO is very difficult, the formation of p-n homojunctions with good rectifying behavior remains challenging. To address this problem, heterojunction-based ZnO LEDs, including p-GaN/n-ZnO, p-polymer/n-ZnO, and p-Si/n-ZnO devices, have been investigated as alternative structures [3]- [5]. In particular, ZnO/Si LED devices have been studied extensively because Si is one of the most important semiconductor materials in state-of-the-art integrated circuits.…”

Wavelength-tunable infrared light emitting diode based on ordered ZnO nanowire/Si1–x Ge x alloy heterojunction

“…ZnO nanowires are regarded as one of the most promising materials for next-generation optoelectronics due to their large exciton binding energy and wide direct bandgap energy at room temperature [7]. Since the fabrication of high quality p-ZnO involves great challenges to form p-n homojunctions [8,9], ZnO LEDs based on heterojunctions including p-GaN/n-ZnO, p-polymer/n-ZnO and p-Si/n-ZnO have been investigated as alternative structures [10][11][12][13][14][15][16].…”