Si/SnSe-Nanorod Heterojunction with Ultrafast Infrared Detection Enabled by Manipulating Photo-Induced Thermoelectric Behavior

Abstract

Photothermal detectors have attracted tremendous research interest in uncooled infrared imaging technology but with a relatively slow response. Here, Si/SnSe-nanorod (Si/SnSe-NR) heterojunctions are fabricated as a photothermal detector to realize high-performance infrared response beyond the bandgap limitation. Vertically standing SnSe-NR arrays are deposited on Si by a sputtering method. Through manipulating the photoinduced thermoelectric (PTE) behavior along the c-axis, the Si/SnSe-NRs heterojunction exhibits a unique four-stage photoresponse with a high photoresponsivity of 106.3 V W–1 and high optical detectivity of 1.9 × 1010 cm Hz1/2 W–1 under 1342 nm illumination. Importantly, an ultrafast infrared photothermal response is achieved with the rise/fall time of 11.3/258.7 μs. Moreover, the coupling effect between the PTE behavior and external thermal excitation enables an improved response by 288.4%. The work not only offers a new strategy to develop high-speed photothermal detectors but also performs a deep understanding of the PTE behavior in a heterojunction system.

Photostimulated Pyrothermoelectric Coupling in Two-Dimensional Tin Monoselenide Enabling Zero-Biased Multimodal Transducers

“…For bulk monochalcogenides, the presence of inversion symmetry forbids their pyroelectricity. However, spontaneous polarization of SnSe monolayer, a new class of the noncentrosymmetric 2D materials, is allowed in the armchair direction due to symmetry breaking, resulting in in-plane pyroelectricity in the group IV monochalcogenide monolayer. , Our presented 2D SnSe multilayers inevitably contain partial SnSe 2 hexagonal structure as ascertained by Raman and XPS results, presumably enabling in-plane pyroelectricity induced by symmetry breaking via forming localized lattice strain, which is advocated by the previous results involving pyroelectricity of SnSe with columnar structure . Hence, the pyroelectricity of 2D SnSe multilayers leads to random oscillation of structural dipoles within a small degree by alignment axes by thermal fluctuation, resulting in instantaneous potential .…”

“…29,40 Our presented 2D SnSe multilayers inevitably contain partial SnSe 2 hexagonal structure as ascertained by Raman and XPS results, presumably enabling in-plane pyroelectricity induced by symmetry breaking via forming localized lattice strain, which is advocated by the previous results involving pyroelectricity of SnSe with columnar structure. 41 Hence, the pyroelectricity of 2D SnSe multilayers leads to random oscillation of structural dipoles within a small degree by alignment axes by thermal fluctuation, resulting in instantaneous potential. 40 Furthermore, we ascertained that crystallinity enhancement by increasing the thickness of SnSe (∼20 nm) using 10 wt % single-source precursor inhibits the instantaneous pyroelectric current and leads to boosted persistent photocurrent governed by the thermo-phototronic phenomenon, as represented in Figure S2, Supporting Information.…”

A high-sensitivity SnSe/Si heterojunction position-sensitive detector for ultra-low power detection

“…The lateral I-V curves of the planar-SnSe film (α The band gap for n-Si is 1.12 eV, while for SnSe it is 0.97 eV. 44 A built-in electric field (Eb) is formed near the interface when the SnSe-NR layer is grown onto the Si substrate, pointing from Si to SnSe due to the difference in the Fermi levels (E f ).…”

“…The band gap for n-Si is 1.12 eV, while for SnSe it is 0.97 eV. 44 A built-in electric field (Eb) is formed near the interface when the SnSe-NR layer is grown onto the Si substrate, pointing from Si to SnSe due to the difference in the Fermi levels ( E f ). And the E f of the Si near the interface is closer to the valence band top ( E v ) due to energy band bending, resulting in the formation of a layer of high hole concentration known as the inversion layer.…”

All-in-One Optoelectronic Logic Gates Enabled by Bipolar Spectral Photoresponse of CdTe/SnSe Heterojunction

“…In a heterojunction photodetector, a four-stage photoresponse behavior is usually induced by two mechanisms, the pyroelectric polarization effect and the PTE effect, respectively. ,− In the CdTe/SnSe heterojunction, the 1550 nm light with a photon energy of ∼0.8 eV is smaller than the band gap of CdTe/SnSe (1.43/0.87 eV). According to the polarization theory, the pyroelectric polarization originates from the varied temperatures.…”