AlScN Pseudosubstrates for High Indium Content InGaN Alloy Epitaxy.

Abstract

Nitride-based semiconductors are vital for efficient optoelectronic devices in the ultraviolet to green spectral range. However, producing red-emitting InGaN micro-LEDs is challenging due to lattice mismatch with traditional GaN substrates. This mismatch causes strain relaxation, compositional gradients, and defects in high-indium-content InGaN films. These issues severely limit device efficiency, and the potential of alternative substrates to address these challenges is not fully explored. Here, we show that Al1-xScxN pseudosubstrates with adjustable lattice parameters greatly improve lattice matching of InGaN. Using plasma-assisted molecular beam epitaxy, we grow 120 nm-thick, phase-pure Al1-xScxN layers (0.1 < xSc < 0.2). This enables high-quality deposition of In0.28Ga0.72N layers and a uniform indium distribution compared to growth directly on GaN. AlScN-supported films exhibit no compositional pulling effect common for conventional substrates. This uniformity is confirmed by room-temperature photoluminescence, showing a narrow emission at 538 nm. Our results demonstrate that AlScN pseudosubstrates are promising for future integrated red micro-LED devices.