Ultrawide-bandgap semiconductors beyond SiC and GaN: A multidimensional framework for the emerging fourth generation

The evolution of semiconductor technologies is better understood as an application-driven expansion of accessible operating space than as a monotonic increase in bandgap. Silicon established scalable integrated electronics, III-V compounds enabled direct-bandgap optoelectronics and high-mobility radio-frequency (RF) devices, and SiC and GaN extended semiconductor operation toward high-field, high-temperature and high-efficiency power and RF systems. Emerging applications increasingly demand combinations of higher critical fields, thermal robustness, deep-ultraviolet functionality, extreme-environment tolerance and scalable manufacturability that push beyond conventional wide-bandgap platforms. Here, we develop a multidimensional working framework for the emerging fourth-generation ultrawide-bandgap (UWBG) semiconductor landscape, in which bandgap serves as a scope-defining material parameter rather than the sole driver of technological evolution. Diamond, β-Ga 2 O 3 and AlN or Al-rich nitrides are evaluated as complementary platforms in terms of intrinsic material limits, crystal and epitaxial manufacturability, doping and contacts, thermal and interface constraints, reliability and device opportunities. Diamond is further examined as an extended case study to illustrate how wafer scaling, defect control, doping and heterogeneous integration determine whether exceptional intrinsic properties can be translated into manufacturable power, thermal-management and quantum technologies. This framework emphasizes that practical semiconductor performance is governed by coupled material, interface, device and system-level constraints rather than by bandgap alone.