Growth-favored nonpolar BAlN digital alloy with cation-order based tunable electronic structure

Abstract

BAlN, an ultra-wide bandgap semiconductor, has attracted the interest of many due to its potential in high-power electronics and high-efficiency optoelectronics. However, the solid solution alloy (SSA) grown along [0001] direction experiences phase separation, which poses a challenge for device applications. To overcome the issues, we proposed BAlN-based digital alloy (DA) arranged along [10–10] and [11–20] directions. Among the whole range of B composition, the mixing enthalpy of DA is at most 16 % and 13 % of the SSA for [10–10] and [11–20] directions, suggesting an improved growth feasibility of DA. The characteristics of DA, including phonon dispersions, bandgap value, dielectric constant, and potential piezo-response along [0001] direction, were thoroughly investigated. Interestingly, cation orders at the same composition offer a wide range of electric, optical, and mechanical properties, some of which are even better than the conventional SSA. It was possible to achieve a maximum tunability of 25 % for the bandgap, while still maintaining direct bandgap properties for up to 67 % boron component. The DA exhibits excellent thermodynamic stability and its characteristics can be easily adjusted, making it a suitable material for high-quality ultra-wide bandgap BAlN alloy growth and applications.