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

Bi2Se3, as a novel 3D topologicalinsulator(TI), is expected to be a strong candidate for next-generation optoelectronicdevices due to its intriguing optical and electrical properties. Inthis study, a series of Bi2Se3 films with differentthicknesses of 5-40 nm were successfully prepared on planar-Sisubstrates and developed as self-powered light position-sensitivedetectors (PSDs) by introducing lateral photovoltaic effect (LPE).It is demonstrated that the Bi2Se3/planar-Siheterojunction shows a broad-band response range of 450-1064nm, and the LPE response is strongly dependent on the Bi2Se3 layer thickness, which can be mainly attributed tothe thickness-modulated longitudinal carrier separation and transport.The 15 nm thick PSD shows the best performance with a position sensitivityof up to 89.7 mV/mm, a nonlinearity of lower than 7%, and responsetime as fast as 62.6/49.4 mu s. Moreover, to further enhance theLPE response, a novel Bi2Se3/pyramid-Si heterojunctionis built by constructing a nanopyramid structure for the Si substrate.Owing to the improvement of the light absorption capability in theheterojunction, the position sensitivity is largely boosted up to178.9 mV/mm, which gets an increment of 199% as compared with thatof the Bi2Se3/planar-Si heterojunction device.At the same time, the nonlinearity is still kept within 10% as welldue to the excellent conduction property of the Bi2Se3 film. In addition, an ultrafast response speed of 173/97.4 mu s is also achieved in the newly proposed PSD with excellentstability and reproducibility. This result not only demonstrates thegreat potential of TIs in PSD but also provides a promising approachfor tuning its performance.