Junction temperature, spectral shift, and efficiency in GaInN-based blue and green light emitting diodes

The junction temperature of homoepitaxial green and blue GaInN/GaN quantum well light emitting diode (LED) dies is analyzed by micro-Raman, photoluminescence, cathodoluminescence mapping, and forward-voltage methods and compared to finite element simulations. Dies on GaN substrate and sapphire were analyzed under variable drive current up to 200mA (246A/cm2). At 100mA, dies on bulk GaN remain as cool as 355K (83°C) while dies on sapphire heat up to 477K (204°C). The efficiency droop and spectral line shift in green LEDs with increasing current density can now be separated into electrical and thermal contributions.