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We clarify the effect of the stress in GaN templates on the subsequent AIlnGaN deposition by simply growing 150nm AIInGaN on a 30μm GaN template (sample 1) prepared by hydride vapor phase epitaxy and a 2.3μm thin control GaN template (sample 2) prepared by metalorganic chemical vapor deposition. X-ray diffraction and secondary iron mass spectroscopy measurements reveal the stress states (tensile stress and full relaxed for samples 1 and 2, respectively) and compositions (Al0.169In0.01 Ga0.821N, Al0.171In0.006 Ga0.823N for samples 1 and 2, respectively) of AlInGaN. By carefully eliminating other possible factor, as template surface roughness, it is concluded that different stress states of AlInGaN should stem from different stress states of GaN templates. 相似文献
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Frontiers of Physics - Recent progress in the observation of surface-enhanced Raman scattering (SERS) is reviewed to examine the possibility of finding a novel route for the effective... 相似文献
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By using high-temperature deep-level transient spectroscopy(HT-DLTS) and other electrical measurement techniques,localized deep levels in n-type AlxGa1-xN epitaxial films with various Al compositions(x = 0, 0.14, 0.24, 0.33, and 0.43)have been investigated. It is found that there are three distinct deep levels in AlxGa1-xN films, whose level position with respect to the conduction band increases as Al composition increases. The dominant defect level with the activation energy deeper than 1.0 eV below the conduction band closely follows the Fermi level stabilization energy, indicating that its origin may be related to the defect complex, including the anti-site defects and divacancies in AlxGa1-xN films. 相似文献
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为了获得高效率的AlGaN基深紫外发光二极管,提出了具有渐变量子垒的氮极性结构来调控载流子的传输.通过氮极性结构在p型电子阻挡层中形成的反向极化诱导势垒,改善空穴注入和电子泄漏问题.另外研究了不同的渐变方向和渐变程度对器件性能的影响.模拟结果显示,在12nm的AlGaN量子垒上沿着(000-1)方向从Al组分0.65线性渐变到0.6,可以有效平衡量子垒的势垒高度和斜率,从而极大的增强空穴注入,光输出功率相较于传统结构提高了53.6%.该设计为电子泄漏和空穴注入问题提供了直接而有效的解决方案,在实现更高效率的深紫外发光二极管方面显示出广阔的前景. 相似文献
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Dual-color(blue and green) InGaN/GaN nanorod light-emitting diodes(LEDs) with three different nanorod diameters are fabricated. Enhancement of luminescence intensity per area is observed in blue and green wells,to varying degrees. When the diameter is 40 nm, it sharply decreases, which could be explained by the sidewall nonradiative recombination. Time-resolved photoluminescence is conducted to study the carrier lifetime. High recombination rate is observed in nanorod arrays, and is an order of magnitude less than that of the planar LED.When the diameter is 40 nm, the nonradiative lifetime decreases, and this explains the decrease of intensity. The3 D-FDTD simulations show the enhancement of light extraction out of geometry structure by calculating the transmittance of the nanorod arrays. 相似文献
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Large-scale SiO2 photonic crystal for high efficiency GaN LEDs by nanospherical-lens lithography 下载免费PDF全文
Wafer-scale SiO2 photonic crystal (PhC) patterns (SiO2 air-hole PhC, SiO2-pillar PhC) on indium tin oxide (ITO) layer of GaN-based light-emitting diode (LED) are fabricated via novel nanospherical-lens lithography. Nanoscale polystyrene spheres are self-assembled into a hexagonal closed-packed monolayer array acting as convex lens for expo- sure using conventional lithography instrument. The light output power is enhanced by as great as 40.5% and 61% over those of as-grown LEDs, for SiO2-hole PhC and SiO2-pillar PhC LEDs, respectively. No degradation to LED electrical properties is found due to the fact that SiO2 PhC structures are fabricated on ITO current spreading electrode. For SiO2- pillar PhC LEDs, which have the largest light output power in all LEDs, no dry etching, which would introduce etching damage, was involved. Our method is demonstrated to be a simple, low cost, and high-yield technique for fabricating the PhC LEDs. Furthermore, the finite difference time domain simulation is also performed to further reveal the emission characteristics of LEDs with PhC structures. 相似文献