Investigation of ultraviolet ZnO nanostructure light emitting diodes
Date Issued
2010
Date
2010
Author(s)
Lu, Tzu-Chun
Abstract
ZnO related materials together with nanostructure LEDs have attracted great interests as the new short wavelength lighting source due to the superior optical and electrical characteristics of ZnO. For there are still difficulties in realizing ZnO homojunction LEDs, GaN is the most suitable substitute for p type material due to many of the physical properties are similar to ZnO. Many groups make effort to fabricate ZnO/p-GaN heterojunction LEDs, but how to suppress the defect related emission and thus achieve high purity ultraviolet (UV) light emission from ZnO are still under concerned.
To overcome these problems, we demonstrate ZnO/p-GaN LEDs with high quality ZnO thin film by RF sputtering at room temperature together with the post annealing. Asymmetric SiO2 confinement barriers of properly designed with ZnO in between are then carried out to exhibit UV radiative recombination in the ZnO layer. Moreover, by improving the interface of ZnO and p-GaN using surface treatments, the UV light emission with suppressing defect states from simple ZnO/p-GaN heterostructures without any confinement layers can be further realized.
For the superior physical properties of nanostructures, ZnO nanowire/p-GaN LEDs are also fabricated using hydrothermal synthesis for the single crystal ZnO nanowire arrays growth. MgO blocking layer between ZnO nanorod and p-GaN are inserted to enhance the UV emission from ZnO nanowires. Furthermore, the “inverted triangle” profile is formed due to the deposition of SiNx on ZnO nanorods. This special shape of nanorod arrays not only makes the continuous contact but also suppresses the deep level emission. We further extract the UV emission under low temperature, the luminescence together with the temperature effect are also discussed.
All the results mentioned above lead us to realize pure UV emission with great suppressed defect band in both ZnO thin film/p-GaN LEDs and ZnO nanowire/p-GaN LEDs. With low cost, low temperature, easily fabrication method and properly designed of structures, ZnO based LEDs indeed have great potential to become the UV light sources.
Subjects
UV light emitting diodes
ZnO
carrier confinement structure
nanorod
low temperature electroluminescence
Type
thesis
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