Temperature-Dependent Spectral Characteristics of AlGaInP Quantum-Well Light-Emitting Diodes

The spectral characteristics of light-emitting diodes (LEDs) based on quaternary AlGaInP compounds incorporating quantum wells were investigated in the temperature range of 77 – 290 K using electroluminescence spectroscopy. At 77 K, the peak emission wavelength was max  571 nm, while the full width at half maximum (FWHM) of the emission band was 9 nm. Lorentzian and Gaussian line-shape functions were fitted to the experimental spectra in order to analyze the dominant broadening mechanisms. It was found that the Lorentzian profile provides better agreement with the measured spectra, indicating the predominance of homogeneous broadening in the investigated structures. The dependences of the emission intensity and the emission peak position on the injection current at 77 K were determined. The Urbach energy was evaluated from the slope of the low-energy tail of the electroluminescence spectra, whereas the carrier temperature was estimated from the high-energy side using the Boltzmann distribution. The temperature dependence of the Urbach energy was found to be linear, allowing the electron–phonon coupling coefficient to be determined as g  0.034. The carrier temperature was shown to increase with injection current and to exceed the lattice (package) temperature because high-energy carriers preferentially overcome the potential barrier in the active region. The obtained results provide insight into the recombination processes and spectral broadening mechanisms in AlGaInP quantum-well LEDs and may be useful for improving the performance of visible-spectrum optoelectronic devices.