TEMPERATURE-DEPENDENT MINORITY-CARRIER LIFETIME MEASUREMENTS OF RED ALGAAS LIGHT-EMITTING-DIODES

Electroluminescent decay and internal quantum efficiency measurements are made as a function of temperature on two double heterostructure AlGaAs light emitting diodes (LEDs) that emit in the visible (red) portion of the spectrum. The electroluminescent lifetimes increase by more than a factor of ten and the internal quantum efficiency falls by a factor of three as the temperature is raised from 90 to 400K. By analyzing the data with a model that accounts for the transfer with increasing temperature of the minority-carrier electrons from the direct-gap to the indirect-gap minima in the p-type active layer of these near-crossover LEDs, values for the radiative and nonradiative lifetimes as a function of tenlperature are obtained. A fit to the radiative-lifetime data results in an estimate of 1.3 x 10(-10) cm(3)s(-1) for the room-temperature radiative recombination coefficient of Al0.39Ga0.61As, which is very similar to values reported for GaAs. The nonradiative lifetimes are found to be nearly independent of temperature from 220 to 400K and provide upper limits of 940 and 1250 cms(-1) for the interface recombination velocities of the two samples. These values are roughly an order of magnitude lower than any previously reported values for high-Al-content (x > 0.3) AlxGa1-xAs heterostructures.