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.