Abstract
The authors have investigated red-emitting (650 nm) resonant-cavity light emitting diodes for use with polymer optical fibres. The small signal modulation response is characterised by a single order roll-off. The -3 dB bandwidth is found to be determined solely by the differential carrier lifetime, T, in the active region and hence dependent on current density, J, alone with no intrinsic size effects. The tau(J) relation allows the calculation of the active region carrier density and hence the recombination parameters (mono- and bimolecular) in the regime where the leakage is small. It is shown that the leakage is insignificant for currents below 200 A/cm(2) at 20degreesC. Above 40degreesC the leakage rises rapidly with temperature, and is evident from a dramatic fall in tau and an accelerated rise in the current required to maintain constant light output.