图形化反射镜能提高LED 芯片的光提取效率． 在蓝宝石衬底背面制备三角周期排列的微米尺寸SiO₂ 圆台形结构，再沉积金属Al，构成图形化反射镜． 基于Monte Carlo光线追迹方法的三维光学仿真表明，相比平面反射镜，图形化Al 反射镜可使芯片光提取效率提升7.5%． 实验测试结果表明，输入电流为20mA 时，相比平面反射镜，图形化Al 反射镜可提升芯片输出光功率8.4%，而芯片的电学性能无恶化． 基于有限元方法的二维热力学仿真讨论表明，图形化反射镜有利于芯片获得更低的温度和热应力，且微结构附近的应力集中对芯片性能的影响可忽略．

Patterned reflectors can improve the light-extraction efficiency of light-emitting diode ( LED) chips.Inthe investigation,a triangular lattice of the micro-scale SiO₂-cone array was placed on the backside of a sapphiresubstrate,and then the metal Al was deposited on the lattice,so that a patterned reflector was built.Three-dimensionalsimulation results obtained through the Monte Carlo ray tracing method show that,as compared with the planemirror,the SiO₂-cone patterned Al backside reflector can improve the light-extraction efficiency of LED chips by7.5%.Experimental results indicate that,when the injection current is 20mA,the LED samples with the patternedreflector achieve a light-output power increase by 8.4% without the degradation of the electrical performance,incomparison with those with plane mirrors.It is found from the two-dimensional finite-element thermodynamic simulationsthat the pattern reflector helps to achieve lower chip temperature and smaller chip thermal-stress in comparisonwith the plane mirror.In addition,the thermal stress concentration in the vicinity of micro-structures has littleeffect on the performance of LED chips.