Localised joule heating in AlGaInP light emitting diodes
Localised optical emission spectra have been obtained from AlGaInP light emitting devices measured across the surface of the LED from the p-contact to the perimeter under DC operation. Shifts in the peak wavelength of the spectral emission were observed that correspond to a non-uniform temperature distribution, providing direct evidence that heat generation occurs locally in the active region around the central p-contact. This effect becomes more apparent with less conductive current spreading layers as a result of current crowding around the p-contact. Devices with current spreading layers of lower sheet resistance were also found to operate with better thermal management since their injection current density is more uniformly spread in the active region.
