Ultraviolet electroluminescence from ordered ZnO nanorod array/p-GaN light emitting diodes
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Abstract:
The highly ordered and aligned ZnO nanorod arrays were grown on p-GaN substrates via a facile hydrothermal process assisted by the inverted self-assembled monolayer template, from which the ZnO nanorod/p-GaN heterojunction light emitting diodes (LEDs) were fabricated. The ZnO nanorod-based LEDs exhibit a stronger ultraviolet emission of 390 nm than the ZnO film-based counterpart, which is attributed to the low density of interfacial defects, the improved light extraction efficiency, and carrier injection efficiency through the nano-sized junctions. Furthermore, the LED with the 300 nm ZnO nanorods has a better electroluminescence performance compared with the device with the 500 nm nanorods.Keywords:
Nanorod
Ultraviolet
Wide-bandgap semiconductor
We report enhanced light output of GaN-based light-emitting diodes (LEDs) with vertically aligned ZnO nanorod arrays. The ZnO nanorod arrays were prepared on the top layer of GaN LEDs using catalyst-free metalorganic vapor phase epitaxy. Compared to conventional GaN LEDs, light output of GaN LEDs with the ZnO nanorod arrays increased up to 50% and 100% at applied currents of 20 and 50mA, respectively. The source of the enhanced light output is also discussed.
Nanorod
Wide-bandgap semiconductor
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Commercially available GaN blue LEDs have been characterized for use as light sources for chemical sensors. These new LEDs are a double heterojunction structure of InGaN/AlGaN that have a peak output at 450 nm. Other groups have investigated these devices for full color displays. This investigation addresses parameters critical to chemical sensors. Several different paramters were characterized including spectra verses drive current, spectra before and after aging, output power verses drive current, and lifetime. The results of this characterization indicate that these devices perform well for some chemical sensors.
Characterization
Wide-bandgap semiconductor
Indium gallium nitride
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Wide-bandgap semiconductor
Indium nitride
Solid-State Lighting
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Electroluminescent (EL) diode utilizing poly(methylphenylsilane) (PMPS) has been fabricated and its optical and electroluminescent characteristics have been investigated. We have succeeded in demonstrating ultraviolet emission at 353 nm from the PMPS EL diode for the first time.
Ultraviolet
Ultraviolet light
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We report on Mg doping in the barrier layers of InGaN/GaN multiple quantum wells (MQWs) and its effect on the properties of light-emitting diodes (LEDs). Mg doping in the barriers of MQWs enhances photoluminescence intensity, thermal stability, and internal quantum efficiency of LEDs. The light output power of LEDs with Mg-doped MQW barriers is higher by 19% and 27% at 20 and 200 mA, respectively, than that of LEDs with undoped MQW barriers. The improvement in output power is attributed to the enhanced hole injection to well layers in MQWs with Mg-doped barriers.
Wide-bandgap semiconductor
Quantum Efficiency
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Wide-bandgap semiconductor
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GaN nanorods and nanosheets with non-polar facets are used as templates to form InGaN QW active regions for LEDs on the nonpolar facets. Uniform, narrow spectra light emitting regions are formed on the nonpolar facets.
Nanorod
Wide-bandgap semiconductor
Template
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The effects of InGaN-based light-emitting diodes (LEDs) with Al composition increasing and decreasing GaN-AlGaN barriers along the growth direction are studied numerically. Simulation results suggest that the LEDs with GaN-AlGaN composition-decreased barriers show more significant enhancement of light-output power and internal quantum efficiency than LEDs with composition-increasing GaN-AlGaN barriers when compared with the conventional LED with GaN barriers, due to the improvement in hole injection efficiency and electron blocking capability. Moreover, the optical performance is further improved by replacing GaN-AlGaN barriers with AlGaN-GaN barriers of the same Al composition-decreasing range, which are mainly attributed to the modified band diagrams. In addition, the major causes of the different efficiency droop behaviors for all the designed structures are explained by the electron leakage current and the different increase rates of hole concentration with injection current.
Wide-bandgap semiconductor
Quantum Efficiency
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Wide-bandgap semiconductor
Blocking (statistics)
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