In Situ Temperature Measurement of GaN-Based Ultraviolet Light-Emitting Diodes by Micro-Raman Spectroscopy

The junction temperatures of ultraviolet (UV) light-emitting diodes (LEDs) were determined in situ using noncontact micro-Raman spectroscopy. This method is based on the systematic downshift of the Raman peak as junction temperature rises. A calibration measurement was carried out first to establish the relation between junction temperature and the Raman peak, followed by temperature measurements as the forward current increased from 50 mA to 110 mA. A temperature rise from 27°C to 107°C was observed. We have demonstrated that micro-Raman spectroscopy is a viable technique for UV LED junction temperature determination.