Pt/ZnGa₂O₄/p-Si Back-to-Back Heterojunction for Deep UV Sensitive Photovoltaic Photodetection with Ultralow Dark Current and High Spectral Selectivity

Abstract

In this work, a strategy of constructing a back-to-back heterojunction is proposed to fabricate Si-based photovoltaic photodetectors with high deep ultraviolet (DUV) spectral selectivity. By combining Pt with a thickness of 4 nm with a ZnGa 2 O 4 / Si heterojunction, a back-to-back heterojunction is successfully constructed. Based on that, a Pt/ZnGa 2 O 4 /p-Si DUV photovoltaic detector with a low dark current density (∼9.6 × 10 −5 μA/cm 2 ), a large photo-to-dark current ratio (PDCR, >10 5 ), and a fast response speed (decay time <50 ms) is fabricated. At 0 V bias, this device displays a photoresponsivity of about 1.36 mA/W and a high deep ultraviolet−visible (DUV−vis) rejection ratio (R 258 nm /R 420 nm ) of ∼1.1 × 10 5 , which are 1−2 orders of magnitude higher than those of most photovoltaic DUV detectors reported currently. Even at a working temperature of 470 K, the detectivity of this device can still reach ∼1.23 × 10 10 Jones. In addition, compared with Au/ ZnGa 2 O 4 /Si devices, the dark current and PDCR of this Pt/ZnGa 2 O 4 /Si device decrease by 2 orders of magnitude and increase by 1 order of magnitude, respectively. The enhanced performance of this ZnGa 2 O 4 /Si device can be attributed to the higher Schottky barrier established between Pt with a higher work function and ZnGa 2 O 4 . This strategy of adopting a back-to-back heterojunction device structure to hinder the visible light photoresponse of Si-based photodetectors and thus to reduce the dark current of a device can provide a reference for preparing photovoltaic DUV detectors with excellent performance.

Humidity-Resistant Solar-Blind Ultraviolet Photodetectors Based on Solution-Processed Amorphous Scandium Oxide Films

“…The size of the Pt electrode is 0.9 × 1.5 mm 2 . The detectivity of this ScO x SBUV photodetector under 0 and −1 V bias is calculated based on the formula where R is the photoresponsivity, e is the absolute value of electron charge (1.6 × 10 –19 C), and I d is the dark current.…”

Three-dimensional Dirac semimetal (Cd1−xZnx)3As2/Sb2Se3 back-to-back heterojunction for fast-response broadband photodetector with ultrahigh signal-to-noise ratio

“…2b presents a representative current-voltage (I-V) curve of the device in a dark environment. The asymmetric nonlinear characteristic of the I-V curve under forward and reverse biases is attributable to the formed BTB double-heterojunction barrier between the 3D Dirac semimetal (Cd 1−x Zn x ) 3 As 2 and the Sb 2 Se 3 semiconductor [33][34][35]. Additionally, the n-type characteristic of (Cd 1−x Zn x ) 3 As 2 and the p-type behavior of Sb 2 Se 3 were confirmed via Hall coefficient measurement (Table S1).…”

“…Fortunately, the moderate chemical doping of zinc (Zn) into a Cd 3 As 2 film can effectively compensate for the residual electron concentration to reduce the electron state density via the formation of the 3D Dirac semimetal (Cd 1−x Zn x ) 3 As 2 , as revealed in previous studies [30][31][32]. Furthermore, considering the limitation of the photoconductive device structure, constructing a back-to-back (BTB) heterojunction through the combination of the 3D Dirac semimetal with a high-resistance semiconductor may be a reliable strategy for achieving photodetection, because the dark current and device noise will be effectively suppressed [33][34][35]. Antimony selenide (Sb 2 Se 3 ) features a superior light absorption coefficient (>10 6 cm −1 ), suitable band gap, and excellent chemical stability, and thus has the potential for achieving fastresponse broadband photodetection by forming a BTB heterojunction with the 3D Dirac semimetal (Cd 1−x Zn x ) 3 As 2 [36][37][38][39].…”

Extremely High Photovoltage (3.16 V) Achieved in Vacuum-Ultraviolet-Oriented van der Waals Photovoltaics

“…Compared with the VUV photodetectors with p-i-n structure reported previously, the photovoltaic performance of the prepared device is significantly improved (Table S1). ,,,,, By analyzing Raman scattering spectroscopy, the degree of how doping modulates the Fermi level of graphene is extracted. And combined with the photoelectric output of the graphene device, the increase mechanism of V OC of the device is elucidated.…”

“…Getting these two figures of merit improved is an urgent and meaningful need not only for photocells but also for a better performance of the photodetectors operating in current or voltage mode. In previous studies on AlN-based photovoltaic devices, n-type 4H-SiC has been proved as an ideal substrate for heteroepitaxial AlN films and an excellent electron transport layer for devices owing to the advantages of high lattice matching and small electron affinity which provides large contact potential difference. − In previous reports, metals with large work functions such as Pt were usually used as semitransparent window layers to collect photogenerated holes, − but their transmittance to VUV light is limited, which is not conducive to the photoexcitation of absorbing layers. Therefore, optimizing the hole transport layer can be an effective way to further improve the photovoltaic performance of the device.…”