Temperature-dependent luminescent properties of dual-wavelength InGaN LEDs

Abstract

Temperature-dependent luminescent properties of dual-wavelength blue-cyan light emitting diodes (LEDs) based on InGaN quantum wells were investigated by means of photo- (PL) and electroluminescence (EL) spectroscopy techniques. The results showed that the thickness of the interwell GaN layer had a great impact on the spectra (especially on the EL ones) at room temperature. At low temperatures, however, the EL spectra are nearly identical for all the samples regardless the differences at room temperature. The differences in the temperature behavior of the above-bandgap PL spectra can be explained in terms of different areas of carrier collection region for the samples with different interwell barrier thickness, as evidenced by the below-bandgap PL spectra measurements as well as by the Beer's law calculations. Additionally, an anomalous increase of the above-bandgap PL intensity is observed at the temperature range of ~120–150 K, which is absent in the case of below-bandgap excitation.