Measurement of junction temperature in a nitride light-emitting diode

The steady junction temperatures of a nitride light-emitting diode (LED) under various currents were measured. The measurements revealed a thermal resistance of R_T = 63.47 K/W. These data were further used to determine the evolution of the junction temperature with time. The transients of the junction temperature after the device was turned on were found to be described effectively on the basis of the theoretical curves. The thermal conductivity of the substrate was deduced and found to be higher for two reasons. The first is related to the optical power carried by photons. The second involves the difference between the p-mesa area and the chip area, which is a unique characteristic of nitride LEDs grown on insulating substrates.