Full InGaN red light emitting diodes
A. Dussaigne, Frédéric Barbier, B. Damilano, Sébastien Chenot, Adeline Grenier, Anne‐Marie Papon, B. Samuel, Badhise Ben Bakir, David Vaufrey, J Pillet, A. Gasse, Olivier Ledoux, Maria Rozhavskaya, D. Sotta
Abstract
The full InGaN structure is used to achieve red light emitting diodes (LEDs). This LED structure is composed of a partly relaxed InGaN pseudo-substrate fabricated by Soitec, namely, InGaNOS, a n-doped buffer layer formed by a set of InxGa1−xN/GaN superlattices, thin InyGa1−yN/InxGa1−xN multiple quantum wells, and a p doped InxGa1−xN area. p-doped InGaN layers are first studied to determine the optimal Mg concentration. In the case of an In content of 2%, an acceptor concentration of 1 × 1019/cm3 was measured for a Mg concentration of 2 × 1019/cm3. Red electroluminescence was then demonstrated for two generations of LEDs, including chip sizes of 300 × 300 μm2 and 50 × 50 μm2. The differences between these two LED generations are detailed. For both devices, red emission with a peak wavelength at 620 nm was observed for a pumping current density of 12 A/cm2. Red light-emission is maintained over the entire tested current range. From the first to the second LED generation, the maximum external quantum efficiency, obtained in the range of 17–40 A/cm2, was increased by almost one order of magnitude (a factor of 9), thanks to the different optimizations.