Search Results (104)

In this study, the influence of HfO₂ interlayer thickness on the performance of heteroepitaxial α-Ga₂O₃ layer-based metal–insulator–semiconductor–insulator–metal (MISIM) ultraviolet photodetectors is examined. A thin HfO₂ interlayer enhances the interface quality and reduces the density of interface traps, thereby improving the performance of UVC photodetectors. The fabricated device with a 1 nm HfO₂ interlayer exhibited a significantly reduced dark current and higher photocurrent than a conventional metal–semiconductor–metal (MSM). Specifically, the 1 nm HfO₂ MISIM device demonstrated a photocurrent of 2.3 μA and a dark current of 6.61 pA at 20 V, whereas the MSM device exhibited a photocurrent of 1.1 μA and a dark current of 73.3 pA. Furthermore, the photodetector performance was comprehensively evaluated in terms of responsivity, response speed, and high-temperature operation. These results suggest that the proposed ultra-thin HfO₂ interlayer is an effective strategy for enhancing the performance of α-Ga₂O₃-based UVC photodetectors by simultaneously suppressing dark currents and increasing photocurrents and ultimately demonstrate its potential for stable operation under extreme environmental conditions. Full article

Transition metal dichalcogenide (TMD) materials have demonstrated promising potential for applications in photodetection due to their tunable bandgaps, high carrier mobility, and strong light absorption capabilities. However, limited by their intrinsic bandgaps, TMDs are unable to efficiently absorb photons with energies below the bandgap, resulting in a significant attenuation of photoresponse in spectral regions beyond the bandgap. This inherently restricts their broadband photodetection performance. By introducing metasurface structures consisting of subwavelength optical elements, localized plasmon resonance effects can be exploited to overcome this absorption limitation, significantly enhancing the light absorption of TMD films. Additionally, the heterogeneous integration process between the metasurface and two-dimensional materials offers low-temperature compatibility advantages, effectively avoiding the limitations imposed by high-temperature doping processes in traditional semiconductor devices. Here, we systematically investigate metasurface-enhanced two-dimensional MoSe₂ photodetectors, demonstrating broadband responsivity extension into the mid-infrared spectrum via precise control of metasurface structural dimensions. The optimized device possesses a wide spectrum response ranging from 808 nm to 10 μm, and the responsivity (R) and specific detection rate (D*) under 4 μm illumination achieve 7.1 mA/W and 1.12 × 10⁸ Jones, respectively. Distinct metasurface configurations exhibit varying impacts on optical absorption characteristics and detection spectral ranges, providing experimental foundations for optimizing high-performance photodetectors. This work establishes a practical pathway for developing broadband optoelectronic devices through nanophotonic structure engineering. Full article

Perovskite, as a promising class of photodetection material, demonstrates considerable potential in replacing conventional bulk light-detection materials such as silicon, III–V, or II–VI compound semiconductors and has been widely applied in various special light detection. Relying solely on the intrinsic photoelectric properties of perovskite gradually fails to meet the evolving requirements attributed to the escalating demand for low-cost, lightweight, flexible, and highly integrated photodetection. Direct manipulation of electrons and photons with differentiation of local electronic field through predesigned optical nanostructures is a promising strategy to reinforce the detectivity. This review provides a concise overview of the optical manipulation strategy in perovskite photodetector through various optical nanostructures, such as isolated metallic nanoparticles and continuous metallic gratings. Furthermore, the special light detection techniques involving more intricate nanostructure designs have been summarized and discussed. Reviewing these optical manipulation strategies could be beneficial to the next design of perovskite photodetector with high performance and special light recognition. Full article

The generation of hot electrons through non-radiative decay processes of surface plasmons (SPs) has been extensively demonstrated, enabling the preparation of high-performance hot-electron photodetectors without limitations imposed by material band gap widths. In this paper, a near-infrared wideband hot-electron metal semiconductor photodetector (WHEMSPD) is proposed based on a metal grating plasmonic structure, and its optical and electrical properties are numerically verified. This structure exhibits excellent broadband characteristics within the long-wave near-infrared range (LW-NIR) of 1200–1800 nm, achieving an absorption of approximately 0.7 between 1200 and 1700 nm, with a peak of 0.98 at 1400 nm. The metal grating structure can effectively enhance the excitation of plasmons on the surface and thus increase the absorption within a larger bandwidth. In terms of electrical performance, the responsivity of the WHEMSPD reaches over 20 mA/W within the wavelength range of 1200–1500 nm, with the peak responsivity reaching 28.3 mA/W around 1320 nm. WHEMSPDs in the LW-NIR can be widely used in military, remote sensing, communication, and other related fields. Full article

Incorporating lead (Pb) into the germanium (Ge) lattice emerges as a promising approach for bandgap engineering, enabling luminescence at longer wavelengths and paving the way for enhanced applications in short-wave infrared (SWIR) light sources and photodetectors. In this work, we report on optical properties of GePb alloys fabricated by a complementary metal-oxide semiconductor (CMOS)-compatible process that includes Pb ion implantation followed by solid-phase epitaxial regrowth via flash-lamp annealing. Optical characterization, including photoluminescence spectroscopy and Fourier-transform infrared reflectance spectroscopy, reveals that GePb alloys exhibit a reduced bandgap compared to pure Ge, resulting in longer-wavelength emission, while also providing broadband antireflective properties below 1800 nm wavelengths due to the surface subwavelength nanostructure. These findings position nanostructured GePb as a highly promising candidate for SWIR optoelectronic applications. Full article

Gallium oxide (Ga₂O₃), an ultrawide bandgap semiconductor, is an ideal material for solar-blind photodetectors, but challenges such as low responsivity and response speed persist. In this paper, one-dimensional (1D) Ga₂O₃ nanorods were designed to achieve high photodetection performance due to their effective light absorption and light field confinement. Through modulating source concentration, pH value, temperature, and reaction time, 1D β-Ga₂O₃ nanorods were controllably fabricated using a cost-effective hydrothermal method, followed by post-annealing. The nanorods had a diameter of ~500 nm, length from 0.5 to 3 μm, and structure from nanorods to spindles, indicating that different β-Ga₂O₃ nanorods can be utilized controllably through tuning reaction parameters. The 1D β-Ga₂O₃ nanorods with a high length-to-diameter ratio were chosen to construct metal-semiconductor-metal type photodetectors. These devices exhibited a high responsivity of 8.0 × 10⁻⁴ A/W and detectivity of 4.58 × 10⁹ Jones under 254 nm light irradiation. The findings highlighted the potential of 1D Ga₂O₃ nanostructures for high-performance solar-blind ultraviolet photodetectors, paving the way for future integrable deep ultraviolet optoelectronic devices. Full article

Optoelectronic devices combining single-layer graphene (SLG) and colloidal semiconducting nanocrystal (NC) heterojunctions have recently gained significant attention as efficient hybrid photodetectors. While most research has concentrated on systems using heavy metal-based semiconductor NCs, there is a need for further exploration of environmentally friendly nanomaterials, such as Cu_2−xS. Chemical ligands play a crucial role in these hybrid photodetectors, as they enable charge transfer between the NCs and SLG. This study investigates the photoresponse of an SLG/Cu_2−xS NCs heterojunction, comparing the effect of two short molecules—tetrabutylammonium iodide (TBAI) and 3,4-dimethylbenzenethiol (DMBT)—as surface ligands on the resulting structures. We have analysed charge transfer at the heterojunctions between SLG and the Cu_2−xS NCs before and after modification with TBAI and DMBT using Raman spectroscopy and transconductance measurements under thermal equilibrium. The photoresponse of two hybrid devices based on three layers of Cu₂₋_xS NCs, deposited in one case on SLG/Cu_2−xS/TBAI (“TBAI-only” device) and in the other on SLG/Cu_2−xS/DMBT (“DMBT + TBAI” device), with a TBAI treatment applied, for both, after each layer deposition, has been evaluated under 450 nm laser diode illumination. The results indicate that the TBAI-only device exhibited a significant increase in photocurrent (4 μA), with high responsivity (40 mA/W) and fast response times (<1 s), while the DMBT + TBAI device had lower photocurrent (0.2 μA) and responsivity (2.4 μA), despite similar response speeds. The difference is attributed to DMBT’s π–π interactions with SLG, which enhances electronic coupling but reduces SLG’s mobility and responsivity. Full article

Both CuI and CuI:Zn semiconductor thin films, along with MSM-structured UV photodetectors, were prepared on flexible mica substrates at low temperature (150 °C) by a wet chemical method. The two CuI-based films exhibited a polycrystalline phase with an optical bandgap energy close to 3.0 eV. Hall effect measurements indicated that the CuI thin film sample had p-type conductivity, while the CuI:Zn thin film sample exhibited n-type conductivity, with the latter showing a higher carrier mobility of 14.78 cm²/Vs compared to 7.67 cm²/Vs for the former. The I-V curves of both types of photodetectors showed asymmetric rectification characteristics with rectification ratios at ±3 V of 5.23 and 14.3 for the CuI and CuI:Zn devices, respectively. Flexible CuI:Zn devices exhibited significantly better sensitivity, responsivity, and specific detectivity than CuI devices both before and after static bending tests. It was found that, while the optoelectronic performance of flexible CuI-based photodetectors degraded under tensile stress during static bending tests, they still exhibited good reproducibility and repeatability in their photoresponses. Full article

Ga₂O₃ has received increasing interest for its potential in various applications relating to solar-blind photodetectors. However, attaining a balanced performance with Ga₂O₃-based photodetectors presents a challenge due to the intrinsic conductive mechanism of Ga₂O₃ films. In this work, we fabricated amorphous Ga₂O₃ (a-Ga₂O₃) metal–semiconductor–metal photodetectors through capacitive coupled plasma assisted magnetron sputtering at room temperature. Substantial enhancement in the responsivity is attained by regulating the capacitance-coupled plasma power during the deposition of a-Ga₂O₃. The proposed plasma energy generated by capacitive coupled plasma (CCP) effectively improved the disorder of amorphous Ga₂O₃ films. The results of X-ray photoelectron spectroscopy (XPS) and current-voltage tests demonstrate that the additional plasma introduced during the sputtering effectively adjust the concentration of oxygen vacancy effectively, exhibiting a trade-off effect on the performance of a-Ga₂O₃ photodetectors. The best overall performance of a-Ga₂O₃ photodetectors exhibits a high responsivity of 30.59 A/W, a low dark current of 4.18 × 10⁻¹¹, and a decay time of 0.12 s. Our results demonstrate that the introduction of capacitive coupled plasma during deposition could be a potential approach for modifying the performance of photodetectors. Full article

A facile and low-cost strategy to fabricate CsPbBr₃ single crystals is essential for developing perovskite optoelectronic devices. Herein, we have presented a room temperature anti-solvent precipitate method for growing sub-centimeter-sized CsPbBr₃ single crystals. The as-prepared CsPbBr₃ single crystal has an orthorhombic structure, and phase transition occurs as the measured temperature increases. The as-grown CsPbBr₃ single crystal also shows abundant surface morphologies including footsteps, precipitated crystals, cracks, and pits. Subsequently, a metal–semiconductor–metal (MSM)-structured photodetector was fabricated based on the CsPbBr₃ single crystal. Under 525 nm green light illumination, the photodetector exhibits an obvious response and the photocurrent linearly increases with the increase in the light intensity. The rise time of the photodetector increases from 0.82 s to 2.19 s as the light intensity is enhanced from 15 mW/cm² to 160 mW/cm², indicating that more time is required to reach to a stable photocurrent. However, the decay time is as fast as ~0.82 ms, irrelevant of the light intensity. The photocurrent, under continuous light illumination, was further studied and this indicates that a stronger light intensity can accelerate the attenuation of the device. Full article

Visible light photodetectors are extensively researched with transparent metal oxide holes/electron layers for various applications. Among the metal oxide transporting layers, nickel oxide (NiO) and zinc oxide (ZnO) are commonly adopted due to their wide band gap and high transparency. The objective of this study was to improve the visible light detection of NiO/ZnO photodiodes by introducing an additional quantum dot (QD) layer between the NiO and ZnO layers. Utilizing the unique property of QDs, we could select different sizes of QDs and responsive light wavelength ranges. The resulting red QDs utilized device that could detect light starting at 635 nm to UV (Ultra-violet) light wavelength and exhibited a photoresponsivity and external quantum efficiency (EQE) of 14.99 mA/W and 2.92% under 635 nm wavelength light illumination, respectively. Additionally, the green QDs, which utilized a device that could detect light starting at 520 nm, demonstrated photoresponsivity values of 8.34 mA/W and an EQE of 1.99% under 520 nm wavelength light illumination, respectively. In addition, we used X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) to investigate the origin of the photocurrents and the enhancement of the device’s performance. This study suggests that incorporating QDs with metal oxide semiconductors is an effective approach for detecting visible light wavelengths in transparent optoelectronic devices. Full article

High-temperature annealing has been regarded as an effective technology to improve the performance of Ga₂O₃-based solar-blind photodetectors (SBPDs). However, as a metastable phase, ε-Ga₂O₃ thin film may undergo phase transformation during post-annealing. Therefore, it is necessary to investigate the effect of the phase transition and the defect formation or desorption on the performance of photodetectors during post-annealing. In this work, the ε-Ga₂O₃ thin films were grown on c-plane sapphire with a two-step method, carried out in a metal-organic chemical vapor deposition (MOCVD) system, and the ε-Ga₂O₃ metal-semiconductor-metal (MSM)-type SBPDs were fabricated. The effects of post-annealing on ε-Ga₂O₃ MSM SBPDs were investigated. As a metastable phase, ε-Ga₂O₃ thin film undergoes phase transition when the annealing temperature is higher than 700 °C. As result, the decreased crystal quality makes an SBPD with high dark current and long response time. In contrast, low-temperature annealing at 640 °C, which is the same as the growth temperature, reduces the oxygen-related defects, as confirmed by X-ray photoelectron spectroscopy (XPS) measurement, while the good crystal quality is maintained. The performance of the SBPD with the post-annealing temperature of 640 °C is overall improved greatly compared with the ones fabricated on the other films. It shows the low dark current of 0.069 pA at 10 V, a rejection ratio (R_peak/R₄₀₀) of 2.4 × 10⁴ (R_peak = 230 nm), a higher photo-to-dark current ratio (PDCR) of 3 × 10⁵, and a better time-dependent photoresponse. These results indicate that, while maintaining no phase transition, post-annealing is an effective method to eliminate point defects such as oxygen vacancies in ε-Ga₂O₃ thin films and improve the performance of SBPDs. Full article

Metal halide perovskites, emerging innovative and promising semiconductor materials with notable properties, have been a great success in the optoelectronic and photocatalytic fields. At the same time, two-dimensional (2D) materials, including graphene, transition metal dichalcogenides (TMDCs), black phosphorus (BP) and so on, have attracted significant interest due to their remarkable attributes. While substantial advancements have been made in recent decades, there are still hurdles in enhancing the performance of devices made from perovskites or 2D materials and in addressing their stability for reliable use. Recently, heterostructures combining perovskites with cost-effective 2D materials have exhibited significant advancements in both efficiency and stability, attributed to the unique properties at the heterointerface. In this review, we provide a thorough overview of perovskite and 2D material heterostructures, spanning from synthesis to application. We begin by detailing the diverse fabrication techniques, categorizing them into solid-state and solution-processed methods. Subsequently, we delve into the applications of perovskite and 2D material heterostructures, elaborating on their use in photodetectors, solar cells, and photocatalysis. We conclude by spotlighting existing challenges in developing perovskite and 2D material heterostructures and suggesting potential avenues for further advancements in this research area. Full article

In this study, quasi-two-dimensional Bi_xSn_1−xO₂ (BTO) thin films were fabricated using a liquid metal transfer method. The ultraviolet (UV) photodetector based on BTO thin films was constructed, and the ultrahigh responsivity of 589 A/W was observed at 300 nm UV light illumination. Interestingly, by dropping ethanol during light-off period, the recovery time induced by the persistent photoconductivity (PPC) effect is reduced from 1.65 × 10³ s to 5.71 s. Furthermore, the recovery time can also be reduced by dropping methanol, propylene glycol, NaNO₂, and Na₂SO₃ after light termination. The working mechanisms are attributed to the rapid consumption of holes stored in BTO thin films by reaction with those solutions. This work demonstrates that the BTO thin films have potential applications in high-performance UV detectors and present an innovation route to weaken the PPC effects in semiconductors by introducing chemical liquids on their surface. Full article

β-Ga₂O₃, with excellent bandgap, breakdown field, and thermal stability properties, is considered to be one of the most promising candidates for power devices including field-effect transistors (FETs) and for other applications such as Schottky barrier diodes (SBDs) and solar-blind ultraviolet photodetectors. Ohmic contact is one of the key steps in the β-Ga₂O₃ device fabrication process for power applications. Ohmic contact techniques have been developed in recent years, and they are summarized in this review. First, the basic theory of metal–semiconductor contact is introduced. After that, the representative literature related to Ohmic contact with β-Ga₂O₃ is summarized and analyzed, including the electrical properties, interface microstructure, Ohmic contact formation mechanism, and contact reliability. In addition, the promising alternative schemes, including novel annealing techniques and Au-free contact materials, which are compatible with the CMOS process, are discussed. This review will help our theoretical understanding of Ohmic contact in β-Ga₂O₃ devices as well as the development trends of Ohmic contact schemes. Full article