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(a) Schematic diagram of the n-ZnMgO/p-GaN heterojunction LED device. SEM images of ZnMgO thin films with the Mg contents of (b) 0%, (c) 4%, and (d) 15%.
The EL spectra of the (a) n-ZnO/p-GaN and (b) n-Zn0.5Mg0.5O/p-GaN (Zn0.85Mg0.15 in source material) LED devices under various bias voltages. The corresponding PL spectra of the (c) ZnO and (d) Zn0.5Mg0.5O films.
(a) The current-voltage (I-V) characteristics of Zn0.5Mg0.5O before and after the ITO deposition and annealing at 400 °C. The inset shows the leakage current at reverse bias voltage conditions. (b) The electroluminescence and (c) photoluminescence spectra of the annealed Zn0.5Mg0.5O LED device under various bias voltages. Inset in (b) is a photo taken from the device under a bias voltage of 15 V. (d) The electroluminescence spectra of the ITO/n-Zn0.5Mg0.5O/p-GaN heterojunction-based LED device further annealed at 500 °C. The emission peak in (d) has shifted back to the near-UV region.
The energy band diagram of the n-Zn0.5Mg0.5O/p-GaN heterojunction at forward bias conditions. At equilibrium, electrons are captured by the indium-induced deep defect levels (∼2.2 eV above the valence band of ZnMgO) and then recombine with the holes injected from the valence band of GaN to emit light.
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