Modelling of Light-Emitting Diodes (2009-)

The operating temperature of light-emitting diodes (LEDs) affects their lifetime. Metrology Research Institute has developed models to help estimate the junction temperatures and lifetimes of LEDs.
Blue LED
Blue light-emitting diode chip.

Metrology Research Institute has studied the optical properties of light-emitting diodes over the years. Based on the data gathered, we have developed state-of-the-art spectral models describing the electroluminescence spectra of AlGaInP and InGaN light-emitting diodes (LEDs) that are the most efficient and common semiconductor alloys able to produce visible radiation. Our spectral models take into account the effective optical joint density of states (JDOS) that depends on the materials and geometrical dimensions used and its thermally induced occupation probability, modelled by weighting the JDOS with the Maxwell-Boltzmann distribution. One spectrum at known temperature for one LED specimen is needed for calibrating the model parameters of each LED type. Then, the model can be used for determining the junction temperature optically from the spectral measurement, as the junction temperature is one of the free parameters. We have validated the models using the multiple spectra of AlGaInP and InGaN LEDs measured at various current levels and the temperatures from 303 K to 398 K. The models work with a few kelvins uncertainty and they are able to model both sides of the spectra.

Contact persons: Anna Vaskuri and Petri Kärhä

References

[1] A. Vaskuri, H. Baumgartner, P. Kärhä, G. Andor, and E. Ikonen, "Modeling the spectral shape of InGaAlP-based red light-emitting diodes," Journal of Applied Physics 118, 203103 (2015).

[2] A. Vaskuri, P. Kärhä, H. Baumgartner, O. Kantamaa, T. Pulli, T. Poikonen, and E. Ikonen, "Relationships between junction temperature, electroluminescence spectrum, and ageing of light-emitting diodes," Metrologia 55, S86–S95 (2018).

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