Low Dislocation Density Homoepitaxy Ultraviolet-A Micro-LEDs Scale Down to 3 μm

Ultraviolet-A (UVA) micro-LEDs are increasingly garnering attention in fields such as additive manufacturing. However, the majority of these devices currently use heteroepitaxial substrates, where high stress from lattice mismatch leads to strong polarization and high dislocation densities, severely limiting the optoelectronic performance. This letter explores the characteristics of homoepitaxially grown UVA micro-LEDs with sizes down to <tex-math notation="LaTeX">3~μ m </tex-math> . At the material level, we report an in-plane compressive stress of 0.043 GPa and a dislocation density of <tex-math notation="LaTeX">10^6 </tex-math> cm−2, which is two to three orders of magnitude lower than that of traditional hetero-epitaxial substrates. At the device level, we examine the size effects from <tex-math notation="LaTeX">100~μ m </tex-math> down to <tex-math notation="LaTeX">3~μ m </tex-math> . The ideality factor and series resistance can reach a minimum value of 1.43 and <tex-math notation="LaTeX">4.85~Ω </tex-math> respectively. Owing to the enhanced crystal quality, all devices exhibit stable emission wavelengths, minimal efficiency droop, and uniform emission across the entire surface.