Two-dimensional (2D) α-In2Se3/Ta2NiSe5 heterojunction photodetector with high sensitivity and fast response in a wide spectral range

As a typical representative of group III-VI two-dimensional (2D) layered semiconductors, α-In2Se3 with layer-dependent direct bandgap (1.39–1.45 eV) has attracted great attention in optoelectronics. At present, various α-In2Se3 based photodetectors have been developed, which show ultrahigh responsivity and detectivity at visible (VIS) wavelengths. However, despite the high sensitivity, the response time is quite long, and the realization of broadband detection from VIS to infra-red (IR) wavelengths is also challenging for these α-In2Se3 photodetectors. In this paper, we introduced a narrow and direct bandgap 2D semiconductor Ta2NiSe5 and made an α-In2Se3/Ta2NiSe5 heterojunction photodetector, which achieved a wide response wavelength of 405–1550 nm with high performance. Originating from the n-type nature of the two semiconductors and the particular type-I energy band alignment, the potential barriers of holes at the α-In2Se3/Ta2NiSe5 interface is much higher than that of electrons, which leads to an ultra-high responsivity. At 520 nm illumination, the photoresponsivity is 12 A/W and 533 A/W under a self-driven state and a slight bias voltage of 0.1 V, respectively. The highest detectivity is over 8.2 × 1013 Jones. Furthermore, the rise and fall time is shortly at 25 and 423 μs, respectively. We believe that the high-sensitive, broadband, and fast photodetector has great potential in the emerging field of 2D optoelectronics.