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为了提升氮化镓(GaN)蓝光发光二极管(LED)光提取效率,设计了双层光子晶体LED模型.提出等效折射率近似方法,简化求解了结构中的介质波导模式分布.从而对模型中顶层光子晶体刻蚀深度d,嵌入式光子晶体厚度T及其距有源层距离D等结构参数进行了优化.同时利用时域有限差分方法对优化结果进行了验证.相比其他仿真方法,模式分析极大地减小了对LED建模优化的计算复杂度,同时从理论上阐明了不同结构参数变化引起LED光提取效率改变的原因.研究发现,当顶层光子晶体满足d≈λ/n_(PhCs)时,结构内大部分高阶导模尚未被截断但源区能量向低阶导模的转化被有效抑制,光提取效率给出极大值.嵌入式光子晶体的引入将激发覆盖层模式,当满足100 nm≤T≤300 nm且100 nm≤D≤200 nm时,覆盖层模式可以从有源层获得较大能量并有效地与顶层光子晶体耦合,极大地提升了光提取效率.本文优化结果使得LED光提取效率提升了4倍,对高性能GaN蓝光LED的设计制造具有重要意义.
In order to improve the light extraction efficiency of GaN blue light-emitting diode (LED), a double-layer photonic crystal LED model is designed and an equivalent refractive index approximation method is proposed to simplify the distribution of dielectric waveguide modes in the structure. The depth of top photonic crystal etching d, the thickness T of embedded photonic crystal and the distance D from the active layer are optimized, and the optimization results are verified by the finite difference time-domain method.Compared with other simulation methods, The analysis greatly reduces the computational complexity of LED modeling optimization and at the same time theoretically elucidates the reason for the change of LED light extraction efficiency caused by the change of different structural parameters.It is found that when the top photonic crystal satisfies d≈λ / n_ (PhCs ), Most of the high-order guided modes in the structure have not been cut off yet the conversion of the energy of the source region to the low-order guided modes is effectively suppressed and the light extraction efficiency gives a maximum value. The introduction of embedded photonic crystals will stimulate the overlay mode, When 100 nm≤T≤300 nm and 100 nm≤D≤200 nm are satisfied, the cladding mode can obtain more energy from the active layer and effectively couple with the top photonic crystal, which greatly improves the light extraction efficiency. Results Optimization of text so that the LED light extraction efficiency by 4 times, important for the design of high performance GaN blue LED manufacture.