Luminescence spectra of blue and green light-emitting diodes based on multilayer InGaN/AlGaN/GaN heterostructures with quantum wells

The luminescence spectra of blue and green light-emitting diodes based on In x Ga 1− x N/Al y Ga 1− y N/GaN heterostructures with a thin (2–3 nm) In x Ga 1− x N active layer have been investigated in the temperature and current intervals 100–300 K and J =0.01–20 mA, respectively. The spectra of the blue and green light-emitting diodes have maxima in the interavals ℏω max =2.55–2.75 eV and ℏω max =2.38–2.50 eV, respectively, depending on the In content in the active layer. The spectral intensity of the principal band decreases exponentially in the long-wavelength region with energy constant E 0 =45–70 meV; this is described by a model that takes into account the tails of the density of states in the two-dimensional active region and the degree of filling of the tails near the band edges. At low currents radiative tunneling recombination with a voltage-dependent maximum in the spectrum is observed in the spectra of the blue diodes. A model of the energy diagram of the heterostructures is discussed.