Evolution of Defect in AlGaN-based Deep Ultraviolet Light Emitting Diodes During Electrical Stress

This work provides an intensive investigation of defect evolution in the degradation process induced by electrical stress of AlGaN-based deep ultraviolet light emitting diodes. The reduced optical power and the increased leakage current are directly related to a new generated electron trap B with an energy level in the range of 0.25-0.38 eV, which is extracted from deep level transient spectroscopy (DLTS) measurement. The significantly increased "yellow" band peak in PL spectra and the linear relation between DLTS signal and pulse width indicate that, defect B corresponds to Ga vacancy along dislocation. The increase of Ga vacancy is accompanied with a decrease of hole trap A with energy level of 0.29-0.34 eV. Combining with first-principle calculation and experimental results, it is demonstrated that the generation of Ga vacancy is originated from the variation in Mg-related defect along dislocation.