Current and Temperature Measurement via Spectral Decomposition of Light Emission from a GaN Power Diode

This paper proposes a method of monitoring light emission from wide-bandgap III-N power devices which will determine the ON state current in the device needed for power electronic converter control. Measurement of current is accomplished via real-time measurement of the spectral content of light emission from a III-N device under forward steady-state bias. At the same time, it is demonstrated that local base die temperature is simultaneously measured. Fast measurement of the spectral content of light emission is accomplished by passing the light through optical filters centered around peaks in the spectrum corresponding to light emission due to exciton recombination in the device. Measurements of the spectral content about these peaks is calibrated versus varying on-state currents and junction temperatures of a representative GaN PN device. These measurements are then used to demonstrate a proof-of-concept extraction of real-time temperature and current variation under test waveforms. Accuracy of current prediction is shown to be within 1%. Methods of improving the temperature predictions and measurement of realistic current waveforms within a converter environment are proposed.