New view on the variation of forward conduction mechanisms derived from electrical stress in UV-A light emitting diodes

Abstract

Abstract The electrical stress induced variation of forward conduction mechanism in ultraviolet light emitting diodes in UV-A spectral range is usually attributed to the increase of trap density. The influence from trap energy level, which plays an equally significant role in the trap-assisted tunneling (TAT) theory, is nevertheless neglected in previous studies. In this work, the effect of electrical stress on the forward conduction mechanism of UV-A light emitting diodes has been studied using temperature-dependent current-voltage measurement and the variation of trap physical parameters has been monitored using deep level transient spectroscopy (DLTS) measurement. For the first time, it is demonstrated that, the rate of TAT increases after electrical stress, and has a much stronger correlation with trap energy level as compared to the trap density.