Measurement and Analysis of Thermal Parameters and Efficiency of Laser Heterostructures and Light-Emitting DiodesA thermal resistance characterization of semiconductor quantum-well heterolasers in the AlGaInAs-AlGaAs system (λst≈ 0.8 μm), GaSb-based laser diodes (λst≈ 2 μm), and power GaN light-emitting diodes (visible spectral region) was performed. The characterization consists in investigations of transient electrical processes in the diode sources under heating by direct current. The time dependence of the heating temperature of the active region of a source ΔT(t), calculated from direct bias change, is analyzed using a thermalRTCTequivalent circuit (the Foster and Cauer models), whereRTis the thermal resistance andCTis the heat capacity of the source elements and external heat sink. By the developed method, thermal resistances of internal elements of the heterolasers and light-emitting diodes are determined. The dominant contribution of a die attach layer to the internal thermal resistance of both heterolaser sources and light-emitting diodes is observed. Based on the performed thermal characterization, the dependence of the optical power efficiency on current for the laser diodes is determined.
Analysis of the thermal resistance of power lightemitting diodes (LEDs) of Cree and Rebel types is developed. Components of the thermal resistance of the diodes are determined and several distinguishes between different methods are obtained. Behavior of bottleneck effect related to definite interfaces is established. The value of LED active junction area is evaluated too.
Thermal relaxation differential spectrometry (TRDS) was used to study the thermal parameters of samples with various design features for heat removal -a powerful LED lamp (150 W) used in industrial and street lighting, low power LED lamps (4 W) with filament emitters, as well as SMD emitter. It is shown that the method of thermal relaxation differential spectrometry is effectively applicable to the study of the structure of thermal parameters of both high-power and low-power LED devices. The method is informative and allows to study in the distribution of thermal resistance and heat flux over the volume and layers of the LED device detail. The use of the TRDS method allows the optimization of the thermal design of LED devices to reduce the overheating temperature of their active regions, and, therefore, to reduce the degradation of LED devices.
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