Suppressing Dislocations and Excess Compressive Stress in High-Temperature-Annealed AlN Films through Macrostep-Induced Dislocation Inclination

High-temperature annealing (HTA) is a simple yet effective method for reducing threading dislocation densities (TDDs) in AlN films. However, it often results in excess compressive stress, causing serious deterioration of surface morphology. Conventional stress modulation techniques, such as inserting a three-dimensional interlayer, can alleviate this problem but will adversely affect crystalline quality. This study introduces a novel approach to overcoming these challenges by combining HTA with subsequent regrowth on sapphire substrates with large offcut angles. In AlN films grown on these substrates, zigzag-type macrosteps are formed due to the larger offcut angles, which inclines dislocations, enhancing the likelihood of threading dislocation annihilation and generating tensile stress. This inclination facilitates dislocation interactions and annihilations by aligning Burgers vectors for more effective dislocation merging. Although the surface morphology may degrade with a 4° offcut angle due to excessive dislocation bending and stress release, AlN films grown on substrates with a 2° offcut angle exhibited optimal results, achieving a low TDD of 3.55 × 10 8 cm –2 and residual stress of −0.22 GPa. This approach effectively balances stress and dislocation dynamics, underscoring its potential for optimizing AlN films in advanced electronic and optoelectronic applications.