Temperature depended IV-curve method for determining LED internal quantum efficiency

Abstract

A new method for determining the internal quantum efficiency (IQE) of band-to-band luminescence of a light-emitting diodes (LED) is proposed and considered. The IQE value is represented by the product of g and θ values, where g is the band-to-band recombination fraction of the total current and θ is the internal quantum yield of band-to-band recombination, i.e. the fraction of the radiative part of this channel. As shown in the paper, g value can be determined from the experimental IV-curve. The θ value is determined based on the model of the band-to-band channel as a recombination defect. With decreasing temperature, the nonradiative part of the band-to-band channel critically decreases, while the radiative part does not depend on temperature. At ultimately low temperatures, the internal quantum yield of the channel tends to unity. This property allows determining θ values for any temperature using the analysis of the experimental temperature dependence of the electroluminescence intensity. Determining g and θ values allows finding IQE for any temperature (including room temperature). The method has been approved for LEDs fabricated on the basis of MOVPE grown AlGaAs heterostructures with InGaAs multiple quantum wells emitting at wavelength of on 850, 910 and 940 nm. All LEDs have shown maximal IQE of about 80 %–90 %.