Integrating metallic halide perovskites with established modern semiconductor technology is significant for promoting the development of application-level optoelectronic devices. To realize such devices, exploring the growth dynamics and interfacial carrier dynamics of perovskites deposited on the core materials of semiconductor technology is essential. Herein, we report the incommensurate heteroepitaxy of highly oriented single-crystal cesium lead bromide (CsPbBr) on c-wurtzite GaN/sapphire substrates with atomically smooth surface and uniform rectangular shape by chemical vapor deposition. The CsPbBr microplatelet crystal exhibits green-colored lasing under room temperature and has a structural stability comparable with that grown on van der Waals mica substrates. Time-resolved photoluminescence spectroscopy studies show that the type-II CsPbBr-GaN heterojunction effectively enhances the separation and extraction of free carriers inside CsPbBr. These findings provide insights into the fabrication and application-level integrated optoelectronic devices of CsPbBr perovskites.