Undoped p‐Type ZnO Nanorods Synthesized by a Hydrothermal Method

Abstract

Zinc oxide is a very promising material for short‐wavelength light‐emitting devices due to its large band gap and high exciton binding energy. Although great progress has been made in recent years, p‐type doping and control over native defects introduced during or after material growth are still significant problems that hinder the development of efficient ZnO based optoelectronic devices. Here we demonstrate a versatile method for the growth or p‐type or n‐type ZnO nanorods from the same growth solution at temperature as low as 90 °C, where the conductivity type is controlled by the preparation of the seed layer for nanorod growth. The differences in the conductivity type can be attributed to dependency of native defect concentrations and hydrogen incorporation on the seed layer preparation method. Room temperature electroluminescence has been demonstrated from homojunction and heterojunction light emitting diodes containing p‐ZnO nanorods.

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…Utilizing a wet chemical method, Hsu et al demonstrated intrinsic p-type ZnO nanowires [254]. In their report, p-type or n-type ZnO nanowires could be grown from the same growth solution at 90 °C , and the key to controlling the conductivity type was found to be the preparation of the seed layer.…”

“…Hsu et al demonstrated the hydrothermal synthesis of undoped p-ZnO nanowire arrays, and used as-grown p-type ZnO nanowire arrays to fabricate homojunction LEDs [254]. Figure 43 shows the photoluminescence and electroluminescence spectra of the p-ZnO nanowires on A n-ZnO single crystal substrate.…”

“…More importantly, room temperature electroluminescence has been demonstrated based on homojunction and heterojunction light emitting diodes (LEDs) containing the as-grown p-type ZnO nanowires [254].…”

“…Inset is a camera image of the LED when under bias. The blue peak arises from the exciton recombination of electrons from substrate and holes from the nanowire, and the broad red/near infrared emission is likely to be due to electroplex emission since this band was absent in the photoluminescence spectra [254].…”

“…Basically, to make p-type ZnO nanowires, group-V or group-I element atoms are needed to react and then diffuse through the defects of ZnO to replace oxygen or zinc atoms in ZnO. There have been many efforts using both vapor phase [252,253] and solution phase growth approaches [254]. For example, p-type doping of ZnO nanowire arrays has been reported by post-treatment of as-grown n-type ZnO nanowires, such as using NH 3 plasma treatment [255], and thermal deposition and diffusion of As from GaAs wafers [256].…”