GaN基蓝光发光二极管分布布拉格反射器的设计

Design of distributed Bragg reflectors for GaN-based light-emitting diodes

采用传输矩阵法对GaN基蓝光发光二极管分布布拉格反射器(DBR)反射光谱进行研究。计算发现正入射时S偏振(TE模)与P偏振(TM模)反射带是一致的;S偏振和P偏振反射带随着入射角的增大都向高频(短波)方向移动,且两者之间的差别也随之增大,DBR反射带蓝移快慢与入射介质相关;低折射率入射介质时DBR具有更宽角度响应。通过修改结构参数多次计算表明:入射角修正的方法能较快地找到提高全方向反射的结构。复合DBR以降低反射率或者成倍增加膜层厚度为代价实现大角度范围的反射.复合DBR比传统DBR有更好的光谱特性,这对提高发光二极管的出光效率有现实意义。

The reflected spectra of GaN-based distributed Bragg reflector （DBR） for blue light-emitting diodes （LED） are studied by transfer matrix method. The results show that reflective spectra of S-polarized and P-polarized plane waves are the same at normal incidence, but both of them move to high frequency and the difference between them increase rapidly with increasing angle of incidence. Change rate of DBR reflected spectra is related to incident medium, and low refractive index of incident medium has a broader incident response. By modifying the structural parameters, it＇s found that correcting the thickness of films by the angle of incidence for increasing wide-angle reflection is a good method. Coupled DBR increases wide-angle reflection at the cost of reducing reflectivity or doubled the thickness of films. Reflected spectra of coupled DBR design is better than that of the conventional DBR design, which is important to enhance light extraction efficiency from LED.