Chun-Yan Wu, Huinan Zhu, Ming Wang, Jingwei Kang, Chao Xie,* Li Wang and Lin-Bao Luo* 

Abstract:GaSe microbelts was successful synthesized by using Ga/Ga₂Se₃ as the mixture precursors, where excess Ga was required to serve as the metal catalyst. Meanwhile, a spontaneously oxidized surface amorphous oxide (GaOx) layer was presented, which induced a built‐in electric field perpendicular to the surface. Benefiting from this effect, the GaSe microbelt‐based photodetector has attained a high responsivity of ~3866 AW^‐1 and a photoconductive gain up to ~1.06×10⁴. This study sheds light on the controlled synthesis of microstructures and provides a device design concept for high-performance micro/nano optoelectronics.