Abstract
We report electroluminescence (EL) from single horizontal ZnO microrod (MR) and p-GaN heterojunction light-emitting diodes under forward and reverse bias. EL spectra were composed of two blue emissions centered at 431 and 490 nm under forward biases, but were dominated by a ultraviolet (UV) emission located at 380 nm from n-ZnO MR under high reverse biases. Light-output-current characteristic of the UV emission reveals that the rate of radiative recombination is faster than that of the nonradiative recombination. Highly efficient ZnO excitonic recombination at reverse bias is caused by electrons tunneling from deep-level states near the n-ZnO/p-GaN interface to the conduction band in n-ZnO.
Highlights
ZnO is one of the most potentially useful materials for near-ultraviolet photonic devices such as light-emitting diodes (LEDs) due to its direct wide bandgap energy of 3.37 eV and large exciton binding energy of 60 meV at room temperature (RT) [1,2,3]
After the furnace had naturally cooled down to room temperature, the ZnO MRs were deposited on the Si substrate
The ZnO MR was fixed by Ag paste which served as the cathode, while another Ag electrode on the GaN film worked as the anode
Summary
ZnO is one of the most potentially useful materials for near-ultraviolet photonic devices such as light-emitting diodes (LEDs) due to its direct wide bandgap energy of 3.37 eV and large exciton binding energy of 60 meV at room temperature (RT) [1,2,3]. ZnO p-n junction LEDs with low luminescence efficiency have recently been reported, [4] ZnO-based LEDs still suffer from difficulty in producing reliable and high-quality p-type doping materials [5,6,7]. Various one-dimensional heterojuction micro/ nanodevices have been fabricated [11] Among these structures, the heterojunction LEDs use vertically aligned one-dimensional ZnO structures such as microrods (MRs) and nanorods (NRs) which exhibit better electroluminescence (EL) performance than ZnO film LEDs because determined to evaluate the high-efficiency electroluminescence performance of the diode
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