结温对高压白光LED光谱特性的影响

高压LED因其自身突出的特点在照明领域有着潜在的应用优势,但作为一种新型功率LED,其光电热特性仍需深入研究。该实验对6和9V GaN基高压LED芯片进行了相同结构和工艺条件的封装,对封装样品进行了10~70℃的变温度光谱测试,并进行了从控温平台温度到器件结温的转换。为保证器件的电流密度相同,6和9V样品光谱测试的工作电流分别设定为150和100mA。结果显示,结温升高会导致蓝光峰值波长红移、波长半高宽增大、光效下降和显色指数上升等现象。在相同平台温度和注入功率下,9V样品的结温低于6V样品;随着温度的升高,9V样品波长半高宽的增加量比6V样品少1.3nm,光效下降量少1.13lm·W~(-1),显色指数上升量少0.28。以上表明,与低压LED相比,高压LED有着更低的工作结温和更小的温度影响。原因在于,相同环境温度下高压LED具有更好的电流扩展性和更少的发热量。此特性在高压LED的研究、发展与应用等方面具有参考价值。此外,峰值波长仍与结温有着较好的线性度,在光谱设备精度较高的情况下可继续作为结温的敏感参数。

Effect of Junction Temperature on EL Spectra of GaN-Based White High Voltage LEDs

High voltage light emitting diodes (HV-LEDs)have potential advantages on general lighting application for their spe-cial features.But as novel power LEDs,their optical,electrical and thermal characteristics still need to be further studied.In this paper,6 and 9 V GaN-based HV-LEDs were packaged in the same package structure and process conditions.The optical characteristics of two samples were investigated under different temperatures range from 10 to 70 ℃ which were calibrated to j unction temperatures using thermal impedance measurement.To ensure the same current density,working current was set to 150 mA for 6 V sample and 100 mA for 9 V sample respectively.Results show that the increasing junction temperature has a great effect on EL spectra of two samples,such as peak wavelength red-shifting,full width at half maximum (FWHM)broade-ning,luminous efficiency reducing and color rendering index (CRI)increasing.The junction temperature of 9V sample is lower than that of 6 V sample in the same platform temperature and inj ection power.With temperature increasing,the extended quan-titative value of FWHM for 9 V sample is 1.3 nm less than that of 6 V sample,the reduced quantitative value of luminous effi-ciency is 1.13 lm·W-1 less than that of 6 V sample,while the increased quantitative value of CRI is 0.28 less than that of 6 V sample.Those data suggest that EL spectra of HV-LEDs is less affected by junction temperature than traditional LEDs.It is be-cause HV-LEDs perform better in current spreading and generate less heat.This conclusion has reference value for study,devel-opment and applications of GaN-based HV-LEDs.In addition,peak wavelength still has a good linear relationship with junction temperature and it can be a temperature-sensitive parameter when the spectra measurement accuracy is enough.