Measuring the surface temperature of light-emitting diodes by thermoreflectance

Abstract

As the latest applications of LEDs require more harsh operating conditions, understanding the device thermal properties becomes more essential for further improving the device efficiencies. In applications where heat dissipation can be a critical issue, thermoreflectance (TR) can be utilized as a useful noncontact measurement technique for analyzing the thermal properties. In this paper, we investigate the TR method of measuring the surface temperature, using a lateral-type blue LED chip under high-power operation. The TR we employ measures the change in reflectivity from the Au metal electrode. By comparing with surface/junction temperatures measured by other methods based on the thermocouple and the forward voltage, we find that the TR method can provide accurate and reliable results of measuring the surface temperature of modern LEDs. A useful insight can also be obtained from the temperature distribution on the LED chip surface.

Dynamic opto-electro-thermal characterization of solid state lighting devices: measuring the power conversion efficiency at high current densities

“…It can be seen that few pulses are performed and the value of 'n' rarely exceeds 10. This issue arises from the [36], Xi et al [37], Jiang et al [38], Keppens et al [27], Cheng et al [39], Liu et al [40], Kim and Han [41], Oh and Cho [42], Prinate et al [43], Lee et al [44], Tamdogan et al [45], Ozluk at al [46]., Zheng et al [47], and Onwukaeme et al [32]. Each colored line indicates the temperature difference between T p,1 and Tp,n.…”

“…Legend provides author indication (oldest to most recent from top to the bottom), studied device types, and k factors obtained from the pulses with minimum value of I f,p . References from top to bottom are Xi et al[36], Xi et al[37], Jiang et al[38], Keppens et al[27], Cheng et al[39], Liu et al[40], Kim and Han[41], Oh and Cho[42], Prinate et al[43], Lee et al[44], Tamdogan et al[45], Ozluk at al[46]., Zheng et al[47], and Onwukaeme et al[32]. Each colored line indicates the temperature difference between T p,1 and Tp,n.…”

A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes

“…Recently, Zheng et al [ 145 ] employed the thermoreflectance method to study the surface temperature of lateral-type blue LED chips (see Figure 7 ). In their measurements, a reflectivity change of the golden metal electrode was recorded, and it was observed that the thickness of the electrode was sufficiently thick to hide unwanted reflections from the underlying materials.…”

“…References from top to bottom are Xi et al [ 62 ], Xi et al [ 64 ], Jian et al [ 186 ], Keppens et al [ 184 ], Cheng et al [ 114 ], Liu et al [ 203 ], Kim and Han [ 190 ], Oh and Cho [ 196 ], Prinate et al [ 94 ], Lee et al [ 111 ], Tamdogan et al [ 164 ], Ozluk at al. [ 115 ], Zheng et al [ 145 ], and Onwukaeme et al [ 188 ]. Reprinted with permission from Ref.…”