Brightness Degradation Controlled by Current Induced Metastable Defect Creation in a-SiC:H Based Light Emitting Diodes

A study of the electroluminescence degradation of a-SiC:H based light emitting devices (LED) is presented for the first time. The best initial peak brightness obtained is 4.2 cd/m2. All LEDs reported in this paper emit a red light which, when operated under continuous bias in a not fully darkened room, is visible for several minutes, depending on degradation rate. The time dependence of LED degradation, which is reversible upon annealing, can be explained if self-annealing is taken into account. There is evidence of an improved LED performance for lower temperature operation. Pulsed operation, with respect to dc operation, produces a markedly lower defect production rate, associated to a higher brightness after degradation. The possibility of some optimization of the operation parameters (peak current, duty cycle) is discussed.