Recent Advances in PVT Growth of Large-Diameter, High-Quality Aluminum Nitride Single Crystals

Abstract

Aluminum Nitride (AlN), an ultra-wide bandgap semiconductor, boasts a direct bandgap of 6.2 eV, exceptional thermal conductivity (340 W m⁻¹ K⁻¹), and a high breakdown electric field (15.4 MV cm⁻¹), making it highly attractive for deep ultraviolet optoelectronics and high-frequency power applications. Despite these advantages, the industrial deployment of AlN is impeded by the challenges in producing large, defect-controlled single crystals. The Physical Vapor Transport (PVT) method has emerged as a leading technique for fabricating high-quality AlN crystals. This review systematically examines recent technological breakthroughs in PVT-grown AlN, including both homogeneous and heterogeneous substrate strategies, thermal field and stress management, mechanisms of point defect formation, and the integration of simulation techniques for process optimization. Innovations in temperature gradient control, gas-phase composition, seed crystal orientation, and novel crucible designs have enabled the stable growth of 2–4 inch AlN single crystals with markedly reduced impurity levels. Future research should emphasize the integration of multi-scale modeling with experimental validation to surmount existing growth limitations and accelerate the practical application of AlN in advanced electronic devices.