A High Responsivity and Photosensitivity Self‐Powered UV Photodetector Constructed by the CuZnS/Ga₂O₃ Heterojunction

Abstract

Ultraviolet (UV) photodetectors (PDs) are widely used in various fields, such as flame sensing, pollution monitoring, space-tospace communication, ozone-layer holes monitoring, UV-emitter calibration and missile plume detection. [1][2][3][4][5] The radiation in UVC band (200-280 nm) is completely absorbed by the earth atmosphere and does not reach the ground. Therefore, UVC is known as the solar-blind ultraviolet range. So, the photodetector operating in UVC band can effectively avoid the interference from solar radiation, resulting in high-precision detection and strong anti-interference ability, even when exposed to sunlight. [6] Meanwhile, with the phenomenon of thinning ozone layer and even ozone layer hole. Monitoring personal UV exposure has excited the interest of researchers. Therefore, the wearable feature of UV-Radiation Monitor, which provides great convenience for people in the process of using, is eagerly desired and expected to be realized for the current research. Mai et al. synthesized Lead-Free Perovskite film such as Cs 2 AgBiCl 6 , Cs 3 Bi 2 Cl x Br 9−x through vapor-phase anion-exchange strategy. [7,8] These photodetectors based on Lead-Free Perovskite have been used as UV imaging sensor for practical application with excellent performances. In addition, the property of self-powered guarantee devices can work without external energy supply. However, many UV PD must work under the relative high bias. The harsh requirement for this kind of devices hinders the process in the use of wearable UV PD undoubtedly. Therefore, the self-powered property of devices provides a guideline toward integrated wearable UV PD.β-Ga 2 O 3 as the ultra-wide bandgap semiconductor has attracted wide spread attention for fabricating the solar-band UV PD. It has huge potential in prominent candidates not only its large band gap of 4.8 eV but also high thermal and chemical stability. [9,10] Therefore, photodetector based on β-Ga 2 O 3 can work in harsh environments. In addition, β-Ga 2 O 3 shows an n-type semiconductor feature which derives from intrinsic oxygen deficiency generally. [11,12] The self-powered system can be driven by a built-in electric field, which is mainly provided by a p-n homojunction, a p-n Fabricating a heterojunction photodetector is efficient to take advantage of the built-in electric field formed by heterojunction and thus improve the performance of photodetector. Herein, a CuZnS/Ga 2 O 3 type-II heterojunction photodetector is designed and constructed by chemical bath deposition for the first time. The photodetector exhibits super high rectifying characteristics (5.7 × 10 4 at ± 1 V), high responsivity (48.01 mA W −1 at 0 V), and detectivity (1.83 × 10 12 Jones at 0 V), which are higher than most of the reported inorganic devices as far as the authors know. Benefiting from built-in electric field constructed by the CuZnS/Ga 2 O 3 type-II heterojunction, the photo-induced electron and hole pairs are quickly separated by the built-in electric field between the Ga 2 O 3 and the CuZnS interface. Th...

Comprehensive Study on Ultra-Wide Band Gap La2O3/ε-Ga2O3 p–n Heterojunction Self-Powered Deep-UV Photodiodes for Flame Sensing

“…To fully investigate the performance of the self-powered La 2 O 3 /ε-Ga 2 O 3 photodetector, we calculated the R and external quantum efficiency (EQE) as a function of light intensities at zero bias, which are illustrated in Figure a. The two parameters along with D * are related to each other; herein, we assume that the shot noise from the I dark is the major component of the total noises, without considering any other internal noises: R = I photo − I dark P · S D * = R S 2 e I dark EQE = h c R e λ where P is the light intensity, S is the efficient illuminated area of the photodetector, e is electron charge, h is Planck’s constant, λ is the wavelength, and c is the speed of light. At 0 V and under illumination with a light intensity of 120 μW/cm 2 , R , D *, and EQE are calculated to be 1.67 mA/W, 2.31 × 10 11 Jones, and 0.82%, respectively.…”

“…With the increase in voltage, more carriers are generated, thus the recovery time is longer. Transient response speed under 254 nm light with light intensity of 488 μW/cm 2 is estimated by fitting with the equation 26 and the τ r /τ d are fitted to be 142.9/135.8 ms During the test, after the device absorbed light around 263 nm, the photogenerated carriers were excited, and due to the PPC effect, the photogenerated carriers could not recombine and disappear immediately, so the responsitivity after wavelengths above 300 nm was slightly higher than that before 250 nm.…”

Microwave-Assisted Synthesis of CuZnS Nanocrystals for Spectrally Flat Visible Light Photodetector Application Using a ZnO/CuZnS Heterojunction

“…ΔI λ is the change in the photocurrent with respect to dark current at wavelength λ. Generally, the EQE of devices follows the given equation below: 52,53 × × EQE absorption collection generation (4) where η absorption , η collection , and η generation are the absorption, charge collection efficiencies, and charge generation (e − −h + ) of the device, respectively. When the device is illuminated with light, the electromagnetic waves pass through the different layers (ZnO/CZS NCs) of devices.…”

“…Semiconducting nanocrystals (NCs) have garnered significant interest in the past century due to their exceptional chemical and physical characteristics like colloidal nature, high internal quantum efficiency, broadband absorption, IR/NIR sensitivity, direct-bandgap nature, etc . In addition, these semiconducting materials exhibit intriguing properties resulting from quantum confinement effects, stemming from their extremely small size. − The unique properties of these NCs have resulted in distinctions between NCs and their bulk counterparts, even when they possess the same composition. , In recent decades, heavy metal-free ternary inorganic NCs-based photovoltaic devices, including Cu 2 S, CuFeS 2 , CuInS 2 (CIS), AgInS 2 (AIS), and CuInSe 2 (CISe), have garnered significant interest − as well as photocatalytic activity such as Cu x Ag 1– x S, Cd x Ag 1– x S, and Zn x Ag 1– x S. − These materials offer advantages such as tunable bandgaps and high absorption coefficients. However, the fabrication of these devices typically relies on vacuum-based techniques. ,, Among them, copper zinc sulfide (CZS) represents a promising and viable alternative for its broadband absorption.…”

Broadband mid-infrared photodetectors utilizing two-dimensional van der Waals heterostructures with parallel-stacked pn junctions

“…The establishment of a built-in electric field within the 2D heterojunction enables the device to work under zero-bias conditions, significantly reducing the dark current [21][22][23]. However, achieving high-sensitivity photodetectors requires not only the reduction of dark current but also the enhancement of photoresponse [24,25]. For devices operating in photovoltaic mode, the exclusive driving force for the separation of photogenerated electronhole pairs originates from the built-in electric field, which is confined within the depletion region.…”