ScAlMgO4 as a promising substrate for InGaN-based long wavelength emitters: demonstration of far-red LEDs

A nitride semiconductor InGaN is a key material for visible optical devices such as light-emitting diodes (LEDs) and laser diodes. Recently, InGaN-based red LEDs attain increasing interest due to potential application in micro- LED displays. However, the emission efficiency is the highest in the blue spectral range and drastically decreases at longer emission wavelengths. One reason is the large lattice mismatch between the InGaN emitters and the host material of GaN. To circumvent lattice-mismatch-induced issues, ScAlMgO₄ substrates are attractive because the host material can be replaced from GaN to InGaN lattice matched to ScAlMgO₄, which can reduce strain in the InGaN emitters. Herein, we demonstrate far-red (∼700 nm wavelength) LEDs based on In_xGa_1−xN/InyGa_1−yN quantum wells (x < y) grown on lattice-matched In_yGa_1−yN/ScAlMgO₄ (0001) templates for the first time.