Cubic GaN is a promising candidate for next-generation power electronics including normally-off, integrated high-electron-mobility transistors, or lateral superjunctions. However, its metastability prevents the material advantage from being translated into functional devices. In this chapter, the reliable growth method of cubic GaN and their characterization is discussed, showing phase-pure cubic GaN stripes with low stacking fault density (3.27 ± 0.18 × 104 cm−1), high structural quality (1284 ± 2 arcsec of full-width at half-maximum), and high optical efficiency (~31.6 ± 0.8%). Furthermore, the growth of cubic nitride alloys on these templates and their characterization is also demonstrated with uniform alloy formation. Finally, the application of cubic GaN and the promising vision of cubic GaN growth on U-grooved Si (100) are presented. Overall, GaN on U-grooved Si (100) can enable next-generation power electronics as well as next-generation photonics.