AlGaInP大功率发光二极管发光效率与结温的关系

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,350 mA注入电流下两者的输出光功率分别为4 关键词： 复合电流扩展层 复合分布式布拉格反射层 出光效率 结温     

High-Temperature Characteristics of Ti/Al/Ni/Au Ohmic Contacts to n-GaN

We present the high-temperature characteristics of Ti/Al/Ni/Au（15 nm/220 nm/40 nm/50 nm） multiplayer contacts to n-type GaN （Nd = 3.7 × 10^17 cm^-3, Nd = 3.0 × 10^18 cm^-3）. The contact resistivity increases with the measurement temperature. Furthermore, the increasing tendency is related to doping concentration. The higher the doped, the slower the contact resistivity with decreasing measurement temperature. Ti/Al/Ni/Au ohmic contact to heavy doping n-GaN takes on better high temperature reliability. According to the analyses of XRD and AES for the n-GaN/Ti/Al/Ni/Au, the Au atoms permeate through the Ni layer which is not thick enough into the AI layer even the Ti layer.     

GaN基大功率白光LED的高温老化特性

对大功率GaN基白光LED在85℃下进行了高温加速老化实验.经6500 h的老化,样品光通量退化幅度为28％ ～33％.样品的Ⅰ-V特性变化表明其串联电阻和反向漏电流不断增大,原因可归结为芯片欧姆接触的退化及芯片材料中缺陷密度的提高.样品的热特性变化显示出各结构层热阻均明显增大,这是由散热通道上各层材料的老化及焊料层出...     

序进应力在线加速退化模型研究

针对线下参数退化模型由于温度冲击而引入误差的问题,基于在线序进应力加速退化实验,建立了在线参数退化模型,提高了以参数变化为计算基础的参数退化模型的准确性.并以3CG120型高频晶体管为例,在150–230 ℃范围内进行了在线序进应力加速实验.利用建立的在线参数退化模型,得到3CG120型高频晶体管的寿命误差为6.5%,比线下参数退化模型的误差(23.2%)要小. 关键词： 序进应力加速实验 参数退化 在线测量     

功率型白光LED光学特性退化分析

将GaN基蓝光芯片涂敷YAG荧光粉和透明硅胶制成额定功率为1 W的白光发光二极管(LED),对其施加900mA的电流应力,在老化过程中测量白光LED的主要光学参数,考察其光学特性的退化情况。经过4 200 h的老化,样品光通量退化为初始值的15%~18% 。样品的漏电流明显增大,表明芯片有源区缺陷密度提高,但光谱分布图中蓝光部分的辐射量未减少,仅观察到黄光部分辐射量的减少,推断出YAG荧光粉的转换效率降低。同时,从原理上分析了样品色温逐渐增大,显色指数基本不变的原因,对大功率白光LED在照明领域的应用有一定的借鉴意义。     

Evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistors by structure function method

The evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistor (HEMT) by structure function method is proposed in this paper.The evaluation is based on the transient heating measurement of the AlGaN/GaN HEMT by pulsed electrical temperature sensitive parameter method.The extracted chip-level and package-level thermal resistances of the packaged multi-finger AlGaN/GaN HEMT with 400-μm SiC substrate are 22.5 K/W and 7.2 K/W respectively,which provides a non-invasive method to evaluate the chip-level thermal resistance of packaged AlGaN/GaN HEMTs.It is also experimentally proved that the extraction of the chiplevel thermal resistance by this proposed method is not influenced by package form of the tested device and temperature boundary condition of measurement stage.