Self-Powered Bi₂Se₃/Si Position-Sensitive Detector and Its Performance Enhancement by Introducing a Si Nanopyramid...

Bi₂Se₃, as a novel 3D topological insulator (TI), is expected to be a strong candidate for next-generation optoelectronic devices due to its intriguing optical and electrical properties. In this study, a series of Bi₂Se₃ films with different thicknesses of 5-40 nm were successfully prepared on planar-Si substrates and developed as self-powered light position-sensitive detectors (PSDs) by introducing lateral photovoltaic effect (LPE). It is demonstrated that the Bi₂Se₃/planar-Si heterojunction shows a broad-band response range of 450-1064 nm, and the LPE response is strongly dependent on the Bi₂Se₃ layer thickness, which can be mainly attributed to the thickness-modulated longitudinal carrier separation and transport. The 15 nm thick PSD shows the best performance with a position sensitivity of up to 89.7 mV/mm, a nonlinearity of lower than 7%, and response time as fast as 62.6/49.4 μs. Moreover, to further enhance the LPE response, a novel Bi₂Se₃/pyramid-Si heterojunction is built by constructing a nanopyramid structure for the Si substrate. Owing to the improvement of the light absorption capability in the heterojunction, the position sensitivity is largely boosted up to 178.9 mV/mm, which gets an increment of 199% as compared with that of the Bi₂Se₃/planar-Si heterojunction device. At the same time, the nonlinearity is still kept within 10% as well due to the excellent conduction property of the Bi₂Se₃ film. In addition, an ultrafast response speed of 173/97.4 μs is also achieved in the newly proposed PSD with excellent stability and reproducibility. This result not only demonstrates the great potential of TIs in PSD but also provides a promising approach for tuning its performance.