Top-Down Synthesis of Wurtzite Gallium Nitride Colloidal Quantum Dots via Defect-Driven Fragmentation

The synthesis of colloidal gallium nitride (GaN) quantum dots (QDs) is limited by the instability of organic ligands at the high GaN crystallization temperatures. Here, we report a top-down, defect-driven fragmentation strategy that yields high-purity colloidal GaN QDs at 50°C and ambient pressure. This process is facilitated by nitrogen-containing organic solvents, which we propose lower the energy barrier for native point defect segregation to the crystal surface, thereby promoting controlled structural subdivision. Defect extraction is supported by the progressive suppression of deep-level defect luminescence and the emergence of sharp, quantum-confined emission with a full width at half maximum of 38.8 nm. Direct observation of crystal fragmentation via identical-location transmission electron microscopy corroborates the mechanism. Post-synthesis analysis reveals extensive crystallite subdivision and the formation of surface Ga²⁺ states. This strategy offers a scalable route to high-quality GaN QDs and provides a foundation for exploring the defect-mediated synthesis of nanostructures from other chemically robust semiconductors.