Control of dislocations in heteroepitaxial AlN films by extrinsic supersaturated vacancies introduced through thermal desorption of heteroatoms

Efficient reduction of dislocations is a key topic in heteroepitaxial AlN films for optoelectronic or electronic applications. For this purpose, we explore a strategy of supersaturated vacancy engineering to promote the climb and meeting of dislocations. Through the intentional incorporation and subsequent thermal desorption of heteroatoms, the thermodynamic limitation for vacancy concentration under equilibrium conditions is broken, i.e., the concentration depends directly on the desorption number of heteroatoms, instead of formation energy. As such, extrinsic supersaturated vacancies can be introduced, significantly magnifying the climb of dislocations and thus enhancing the probability of dislocation meeting and annihilating. Specifically, the supersaturated vacancy engineering is applied to AlN on sapphire with a lattice mismatch as high as 13.3%, which demonstrates a threading dislocation density of 1.56 × 108 cm-2, one order of magnitude lower than that by conventional methods. Furthermore, 280-nm deep-ultraviolet light-emitting diodes are fabricated on such AlN template, and the light output power reaches 39.1 mW at 200 mA, 56% better than that without this approach. This study sheds light on the effective control of vacancies and dislocations and then paves the way for heteroepitaxial films of high quality, as well as consequent optoelectronic or electronic devices of high performance.