Temperature Dependences of Spectral Parameters of Led Lamps Under Electrical and Optical Excitation

The temperature dependences of emission-band positions of the LED heterostructure and the phosphor of white LED lamps were determined to be linear or quasilinear with temperature coefficients K₁ = –0.38 meV/K, K₂ = 0.147 meV/K, and K₃ = 0.27 meV/K for the bands at 2.7, 2.4, and 2.05 eV, respectively. Overheating of the heterostructure active regions during the test time was estimated using data from the spectral measurements. The estimates were compared with the results of direct temperature measurements. The temperature increased by ~20°C during the test time, which was less than the temperature increase of the electronic subsystem (~50°C), in agreement with literature data obtained for other types of LEDs. The main reason for the change in color temperature of the lamp radiation during operation was thermal quenching of luminescence in the phosphor material.