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

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.

Automated summary

BAlN-based digital alloy (DA) arranged along [10-10] and [11-20] directions overcomes the phase separation issue of solid solution alloy (SSA) along [0001] direction and shows improved growth feasibility. DA exhibits a wide range of electric, optical, and mechanical properties due to cation orders at the same composition, some of which are even superior to conventional SSA. Additionally, DA demonstrates excellent thermodynamic stability and adjustability, making it a suitable material for high-quality ultra-wide bandgap BAlN alloy growth and applications.