Degradation and transient currents in III-Nitride LEDs

摘要

Effect of degradation processes on transient currents in LEDs has been studied. It has been found that transient currents are several orders of magnitude higher than steady-state currents. The transient current time dependencies are non-exponential and show a distribution of relaxation times in the range of 1-100 microseconds. The charge associated with the transient currents is Q ～3x10~(-10) C which corresponds to high number of carrier traps N_t ～ 2xl0~9 in the investigated chips. For one-year old chips an increase of charge and trap number by ～ 25% has been found compared to the fresh chips. Two probable reasons have been suggested to explain the observed increase of number of carrier traps: first one is related to increase of the number of trap sites at dislocations, and second one is a gradual phase separation process in quantum wells resulting in degradation of their quality.