Enhanced capture of photogenerated carriers by optimum forward bias condition in blue and green (In,Ga)N single-quantum-well diodes

Vertical capture processes of photogenerated carriers in the c -plane blue and green (In,Ga)N single-quantum-well light-emitting-diodes have been investigated by comparing variations in photoluminescence (PL) intensity as a function of applied voltage (-10+4.5 V) at low temperature (20 K) under direct (ex = 380 nm) and indirect (ex = 325 nm) excitation. One striking result of the bias dependent PL intensity is that the photogenerated carriers are efficiently captured into the active layer by optimum forward bias condition. That is, with increasing forward bias, the PL intensity by the indirect excitation is strongly enhanced within a certain specific forward voltage range, while the PL intensity by the direct excitation is moderately varied. The optimum bias condition is caused by interplay of carrier capture and internal quantum efficiency. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim