Abstract
This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES) depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n-ZnO and p-GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n-ZnO and p-GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n-ZnO/p-GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively.
Highlights
In recent decades, zinc oxide (ZnO) has attracted significant interest for short-wavelength optoelectronics applications for its wide and direct band gap (Eg~3.37 eV at 300 K) [1,2,3]
A short-wavelength band associated with the energy bandgap and a broad long-wavelength band including the involvement of zinc interstitial (Zni), zinc vacancy (VZn), oxygen vacancy (VO), and oxygen interstitial (Oi) defects were generally observed from an undoped n-ZnO film [14,15,16]
To accomplish the aim of an n-ZnO/p-gallium nitride (GaN) heterojunction light emitting diode (LED) that emits pure short-wavelength radiation, it is necessary to address and engineer solutions to the above-mentioned visible emission that emerge from defects in n-ZnO film, as well as the radiation related to the n-ZnO/p-GaN interface and p-GaN epilayer
Summary
Zinc oxide (ZnO) has attracted significant interest for short-wavelength optoelectronics applications for its wide and direct band gap (Eg~3.37 eV at 300 K) [1,2,3]. We reported a LED that radiated only a near-UV emission when it was constructed from a 450 ̋C-annealed n-ZnO/p-GaN heterojunction structure under vacuum atmosphere [18]. This study measured electroluminescence (EL) spectra as a function of n-ZnO/p-GaN heterojunction structures annealed at various temperatures and atmospheres.
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