By examining two types of lateral InGaN/GaN light emitting diodes with different contact patterns, we demonstrate that in the intermediate range of current where the space-charge region dominates in the device performance, the ideality factor (β) increases from 1.9 (current spreading design) up to 2.4 (current crowding design). This modification of β-factor could be erroneously treated as the change of free carrier recombination nature. The current crowding design is also responsible for the local overheating and heavier efficiency droop that occurs at the characteristic current 2.3 times smaller in comparison with the current spreading design.
Current-induced electrical efficiency degradation (EED) is identified as a strong power conversion efficiencylimiting factor for vertical blue InGaN-on-SiC light-emitting diodes (LEDs). It is found that EED is caused by an increase in series resistance that follows current crowding. EED starts at the moderate-current domain (≥ 10 −3 A) and limits the power conversion efficiency at the level of ≤75% in the high-current domain (>1.0 A). By decreasing current spreading length, EED also causes the optical efficiency to degrade and stands for an important aspect of the vertical LED's performance.
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