AlGaInP大功率发光二极管发光效率与结温的关系

Relationship between light efficiency and juction temperature of high power AlGaInP light-emitting diode

目前,AlGaInP大功率发光二极管(LED)存在的主要问题是大电流工作时发热严重,主要是由于电流扩展不均匀、出光面电极对光子的阻挡和吸收以及器件材料与空气折射率之间的差距引起的全反射现象,这些因素造成大功率LED出光受到限制、发光效率低、亮度不高.提出了一种复合电流扩展层和复合分布式布拉格反射层(DBR)的新型结构LED,使得注入电流在有源区充分地扩散,同时提高了常规单DBR对光子的反射率.结果显示,这种新型结构LED比常规结构LED的性能得到了很大的提升,350mA注入电流下两者的输出光功率分别为49.48和17mW(未封装).同时,对器件发热进行了量化测试,分析了LED发光效率与结温的关系,在350mA注入电流下新型结构LED与常规结构LED的流明效率的比值与结温升的比值保持一致,通过减少内部发热,控制结温可以大大提高LED的发光效率.

One of the main problems of high power AlGaInP light-emitting diode （LED） is the heat generated seriously at large working current,which is caused by the weak current spreading,the photon blocking and absorbing of p-type or n-type electrode,and the critical reflection at the interface between the device and air.The heat inside can lead to the restriction on light output,and gives rise to low light efficiency and the low luminous intensity.In this paper,we introduce a new LED structure which is composed of compound current spreading layers and compound distribute Bragg reflector （DBR） layers.For the new structure LED,the injected current spreads adequately and the reflectivity is improved by the compound DBR layers.The testing results show that the performance of new structure LED is much better than that of the conventional LED,and that at a working current of 350 mA,the output powers of the two kinds of LEDs （which are unpackaged） are 17 and 49.48 mW respectively.At the same time,the heat testing results show the relationship between LED light efficiency and juction temperature,and the consistence between the juction temperature ratio and the ratio of light efficiency for the two kinds LEDs,which implies that LED light efficiency can be improved by reducing heat generated inside and reducing the juction temperature.