Recombination dynamics in ultraviolet light-emitting diodes with Si-doped AlxGa1−xN∕AlyGa1−yN multiple quantum well active regions

Abstract

Ultraviolet (UV) light-emitting diodes with AlxGa1−xN∕AlyGa1−yN multiple quantum well active regions, doped in the barriers with different Si doping levels, show a sharp near-band edge emission line (UV luminescence). Some samples have a broad subband gap emission band centered at about 500 nm (green luminescence) in addition to the near-band edge emission. The electroluminescence intensities of the UV and green emission line are studied as a function of the injection current. For the sample grown on the AlN substrate under optimized growth conditions, the UV luminescence intensity increases linearly with the injection current, following a power law with an exponent of 1.0, while the green luminescence intensity increases sublinearly with the injection current. On the contrary, the samples grown on the sapphire substrate show a superlinear (to the power of 2.0) and linear (to the power of 1.0) dependence on the injection current for the UV and green luminescence, respectively. A theoretical model is proposed to explain the relationship between the luminescence intensities and the injection current. The results obtained from the model are in excellent agreement with the experimental results. The model provides a method to evaluate the dominant recombination process by measuring the exponent of the power-law dependence.