High-performance Ultraviolet Photodetectors Research Articles

High-Performance Ultraviolet Photodetectors Based on Nanoporous GaN with a Ga2O3 Single-Crystal Layer.

The utilization of a nanoporous (NP) GaN fabricated by electrochemical etching has been demonstrated to be effective in the fabrication of a high-performance ultraviolet (UV) photodetector (PD). However, the NP-GaN PD typically exhibits a low light-dark current ratio and slow light response speed. In this study, we present three types of UV PDs based on an unetched GaN, NP-GaN distributed Bragg reflector (DBR), and NP-GaN-DBR with a Ga2O3 single-crystal film (Ga2O3/NP-GaN-DBR). The unetched GaN PD does not exhibit a significant photoresponse. Compared to the NP-GaN-DBR PD device, the Ga2O3/NP-GaN-DBR PD demonstrates a larger light-dark current ratio (6.14 × 103) and higher specific detectivity (8.9 × 1010 Jones) under 365 nm at 5 V bias due to its lower dark current (3.0 × 10-10 A). This reduction in the dark current can be attributed to the insertion of the insulating Ga2O3 between the metal and the NP-GaN-DBR, which provides a thicker barrier thickness and higher barrier height. Additionally, the Ga2O3/NP-GaN-DBR PD device exhibits shorter rise/decay times (0.33/0.23 s) than the NP-GaN-DBR PD, indicating that the growth of a Ga2O3 layer on the DBR effectively reduces the trap density within the NP-GaN DBR structure. Although the device with a Ga2O3 layer presents low photoresponsivity (0.1 A/W), it should be feasible to use Ga2O3 as a dielectric layer based on the above-mentioned reasons.

High performance of UV photodetectors by integration of plasmonic Ag nanoparticles on GaN

High-performance ultraviolet photodetectors have attracted much attention due to their various potential applications from household to universal. On basis of this, in this work, a high – performance and photoresponse enhancement UV photodetector based on Ag NPs/GaN heterojunction was demonstrated. By incorporating of Ag nanoparticles, light confinement determined by Ag nanostructure offers an effective approach to break through the limitation of the light-mater interaction within the photoactive layers of photodetector. Various size and elemental composition of Ag NPs are fabricated on GaN lead to significant enhancement of photocurrent in UV photodetector. Consequently, an outstanding photoresponsivity of 89 A/W, external quantum efficiency of 2.8 × 103% at low bias voltage of 0.3 V were achieved. The improve photo-response of the Ag NPs-decorated GaN-based photodetector is attributed to the simultaneous effect of strong plasmon absorption, increased injection of hot electrons into the conduction band of GaN. This study will open up the direction to fabricate the high-performance UV photodetector.

High-performance transparent AZO UV photodetectors

In this work, the fabrication of undoped ZnO (ZO) and 3 at.% aluminum (Al) doped ZnO (AZO) thin films (TFs) based transparent photodetectors (PDs) was reported. Both films were spin-coated on fluorine-doped tin oxide (FTO) substrates to investigate the influence of Al doping on the ultraviolet (UV) detection performance of the devices. The systematic characterizations reveal that Al doping positively affects the characteristics of ZO-TFs. The Al doping leads to slight shift in crystalline peaks and induces an enhancement in grain size. In addition, the surface roughness of ZO-TFs gets lower on Al doping. Further, the Al doping improved the transparency and widening of band gap of TFs. The PDs having metal–semiconductor-metal (MSM) configuration were achieved by screen-printing of Ag paste onto ZO and AZO-TFs. The current–voltage (I-V) profiles of the fabricated PDs were measured in the dark and under UV excitation of 365 nm. The AZO-TFs based MSM PD exhibits a spectral responsivity of 326.82 mA/W and an external quantum efficiency of 111.03%. The reproducibility of the fabricated PDs was tested by performing time-dependent photo-response measurements.

Plasmonically-boosted high-performance UV self-biased photodetector based on SiC-based low-dimensional heterojunction via Pt nanostructures deposition

While possessing fully superior electrical, optical and mechanical capabilities, the third-generation semiconductor SiC is extensively recognized as one of the most important candidates to developing high-temperature CMOS, intense-radiation hard detectors, high-power electron devices, and other fields. However, the fabrication of low-dimensional SiC structures presents a challenge, limiting its forward-looking applications, particularly for the miniaturized and integrated self-powered ultraviolet (UV) photodetectors. Herein, a high-performance UV photodetector, which involving a p-SiC film, a Ga-doped ZnO microwire coated by Pt nanoparticles (PtNPs@ZnO:Ga MW), a single-layer graphene (Gr) as transparent electrode, was constructed. The device exhibits pronounced UV photodetection capabilities, containing a high On/Off ratio (>105), a peak responsivity approaching 0.266 A/W, a specific detectivity exceeding 1.50 × 1013 Jones, and an exceptional external quantum efficiency closing to 98.7% upon 335 nm illumination at 0 V bias. The detector shows an admirable performance and quite competitive within their class. In the device, the surface-coated PtNPs enable to optimize ZnO:Ga/SiC interfacial performances containing significant enhancement of photoelectric conversion efficiency, efficient suppression of surface/interface defects and trapping centers, and other parameters, thus giving rise to qualitative enhancement of the overall detector properties. Simultaneously, the use of Gr electrode as transparent window allows for maximum UV light absorption and boosts transport properties for the photocarriers. This work presents a valuable reference for the development of high-performance low-dimensional SiC-based photodetecting devices, exploring an important step toward potential optoelectronic applications.

Scalable flexible and stretchable high performance UV photodetector based on MoS2-WO3/Ag composite on a PU substrate by utilizing LIG electrodes

The rapid advancements in photodetector device technologies have captivated the optoelectronic industry owing to their strong features, such as wearability, stretchability, energy efficiency, scalability and cost-effectiveness. However, there is still scope for enhancement in device performance, reliability, and scalable fabrication. In this research work, we have proposed a novel strategy for fabricating stretchable ultraviolet (UV) photodetector (PD) on a polyethylene glycol solution-processed synthesis of MoS2-WO3/Ag composite-based nanocrystals onto a polyurethane (PU) substrate. Moreover, laser induced graphene (LIG) interdigitated electrode arrays for swift photogenerated charge extraction due to their high conductivity. The device displays high photoresponsivity, external quantum efficiency, and specific detectivity, measured at 6.84 A/W, 143 %, and 2.87×1011 Jones, respectively. Additionally, the device demonstrates a quick response time of 80 ms when exposed to 360 nm light, indicating its high speed. These essential advantages have a great potential for applications in real life and mass production. The integration of advanced materials and LIG electrodes enhances the device capability for next-generation stretchable, flexible and wearable electronic devices.

Structural and optical properties of position-controlled n-ZnO nanowire arrays: Potential applications in optoelectronics

Highly position-controlled ZnO nanowire (NW) arrays and nanowire-cluster (NW–C) arrays are grown on mask-patterned gallium nitride (GaN) substrates by hydrothermal method. Electroluminescence (EL) emissions with blue-violet light at forward-bias(fb) voltage, EL emissions with yellow light at reverse-bias(rb) voltage, and EL emission at both rb voltages and rb voltages were achieved by the adjustment of the size of the heterojunction interface between wire arrays and film. The high rb current is attributed to electron tunneling transport edge effect via a narrow tunnel barrier. The obtained results highlight that the EL characteristics of ZnO NWs can be tuned and controlled through the size of the heterojunction interface between wire arrays and film. Besides, the nonplanar heterogeneous structure of ZnO NW arrays/GaN film also shown a great spectral response characteristic in the ultraviolet(UV) band, which proves that the structure of is worthy of being studied to achieve high performance UV photodetectors.

Integrating interface engineering and plasmonic effect to boost photoresponse performance of ZnO:Ga/GaN heterojunction self-powered UV photodetectors

The ability to function without an external power supply makes photodetectors highly promising for use in a new generation of wirelessly and independently operated ultraviolet (UV) photodetection and imaging systems. However, self-powered photodetectors' high dark current, inadequate light harvesting, and poor carrier separation prevent them from attaining high-efficiency UV photodetection and imaging. Herein, a high-performance heterojunction UV photodetector consisting of a single Ga-doped ZnO microwire enshrouded by Ag nanowires (AgNWs@ZnO:Ga MW), a MgO electron blocking layer, and a p-type GaN wafer was proposed. Taking full advantage of the interface engineering and plasmonic effects, the AgNWs@ZnO:Ga MW/MgO/GaN photodetector achieves high photodetection performance with an excellent responsivity of 262 mA/W, a remarkable external quantum efficiency of 92.37%, and a high detectivity of 1.966 × 1012 Jones under 370 nm illumination with power density of 0.22 mW/cm2. Furthermore, it also demonstrates ultrafast pulsed photoresponse speed with a rise/fall time of 3.64 μs/252 μs. An UV imaging system is designed based on the AgNWs@ZnO:Ga MW/MgO/GaN self-powered photodetector, allowing for high-quality, accurate, and distinct object imaging. This work combines interface engineering and plasmonic effects for achieving high-performance UV photodetection, which provides a strategic approach to the development of highly efficient optoelectronic devices.

High-Performance Ultraviolet Photodetector Arrays Based on Recessed-Gate HEMT with a Buried p-GaN Layer

High-Performance Ultraviolet Photodetector Arrays Based on Recessed-Gate HEMT with a Buried p-GaN Layer

Highly Responsive Gate-Controlled p-GaN/AlGaN/GaN Ultraviolet Photodetectors with a High-Transmittance Indium Tin Oxide Gate.

This work presents highly responsive gate-controlled p-GaN/AlGaN/GaN ultraviolet photodetectors (UVPDs) on Si substrates with a high-transmittance ITO gate. The two-dimensional electron gas (2DEG) in the quantum well of the polarized AlGaN/GaN heterojunction was efficiently depleted by the p-GaN gate, leading to a high photo-to-dark current ratio (PDCR) of 3.2 × 105. The quantum wells of the p-GaN/AlGaN and AlGaN/GaN heterojunctions can trap the holes and electrons excited by the UV illumination, thus efficiently triggering a photovoltaic effect and photoconductive effect, separately. Furthermore, the prepared photodetectors allow flexible adjustment of the static bias point, making it adaptable to different environments. Compared to traditional thin-film semi-transparent Ni/Au gates, indium tin oxide (ITO) exhibits higher transmittance. Under 355 nm illumination, the photodetector exhibited a super-high responsivity exceeding 3.5 × 104 A/W, and it could even exceed 106 A/W under 300 nm illumination. The well-designed UVPD combines both the advantages of the high-transmittance ITO gate and the structure of the commercialized p-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs), which opens a new possibility of fabricating large-scale, low-cost, and high-performance UVPDs in the future.

The enhanced responsivity and response speed of SnO2 visible-blind transparent photodetectors via the SiO2 passivation layer.

Recently, transparent ultraviolet (UV) photodetectors have gained wide attention for their giant potential in integrated transparent electronics applications. SnO2 films as a common candidate for visible-blind transparent ultraviolet photodetectors have attracted increasing attention. In this work, high-performance visible-blind transparent UV photodetectors based on SnO2 thin film and a SiO2 passivation layer were successfully synthesized by the sol-gel spin coating method for the first time. The obtained SnO2/SiO2 hybrid device has a transmittance of nearly 80% in the visible band at 400-700 nm and demonstrates a high responsivity of 769 mA W-1 and a detection sensitivity of 1.24 × 1014 Jones under UV light illumination. The UV-C/UV-A rejection ratio is greater than 106, indicating that the device has good photo-selectivity. In addition, after the introdution of the SiO2 layer, the response speed is 2 times higher than that of pure SnO2. The presence of the SiO2 layer reduces the exposed area of SnO2, passivates the oxygen vacancies on the surface of SnO2 and inhibits the surface chemical adsorption. The above results provide a new perspective for improving the performance of SnO2 thin film for visible-blind transparent ultraviolet photodetectors.

Preparation of ZnO Nanosheet Array and Research on ZnO/PANI/ZnO Ultraviolet Photodetector.

High-performance ultraviolet photodetectors have important scientific research significance and practical application value, which has been the focus of researchers. In this work, we have constructed a highly photosensitive UV photodetector with a unique "sandwich" structure, which was mainly composed of two layers of ZnO nanosheet arrays and one layer of polyaniline (PANI). The results showed that the UV current of ZnO/PANI devices was 100 times higher than that of pure ZnO devices under the same UV irradiation time. At a 365 nm wavelength, the device had excellent photocurrent responsiveness and photoconductivity. This high performance was attributed to the large specific surface area of ZnO nanosheets and the p-n junction formed between P-type PANI nano-porous film and N-type ZnO nanosheets. This provides a solid theoretical basis for the application of ZnO nanosheets in ultraviolet detection, and possesses significance for the development of ultraviolet photodetectors.

High-performance self-powered solar-blind ultraviolet photodetector based on a 4H-SiC/ZnGa2O4 heterojunction and its application in optical communication

With the urgent demand for low power consumption, environment-friendly, and portable devices, self-powered solar-blind ultraviolet (UV) photodetectors that only rely on built-in electric fields without external power sources have received extensive attention. In this paper, we have demonstrated a self-powered solar-blind UV photodetector based on a 4H-SiC/ZnGa2O4 heterojunction, along with its application in optical communication. At 0 V bias, the device exhibits a peak responsivity of 115 mA/W with an external quantum efficiency of 58.4% at 244 nm, a fast response speed with a rise/decay time of 18.36/16.15 ms, and a high UV-vis rejection ratio of 4.5 × 104, suggesting that the device has an excellent self-powered solar-blind UV photodetection performance. The exceptional performance of the photodetector is mainly attributed to the 4H-SiC/ZnGa2O4 type I heterojunction with a large conduction band offset (ΔEC = 0.99 eV) and a large valence band offset (ΔEV = 0.75 eV), which is determined by the x-ray photoelectron spectroscopy technique. Moreover, the solar-blind UV optical communication is realized by utilizing the 4H-SiC/ZnGa2O4 heterojunction device to receive signals modulated by the solar-blind UV light. This work provides an effective approach to realizing high-performance self-powered solar-blind UV photodetectors and their potential applications in optical communication.

Laser Microengineering in SnO2 microwire array films for high performance ultraviolet photodetectors

Tin oxide (SnO2) has emerged as promising applications in ultraviolet photodetectors (UV PDs) due to its prominent photoelectronic properties. However, the slow photoresponse of UV PDs based on SnO2 films limits the application. In this work, the absorbing intermediate layer-assisted femtosecond (fs) laser microprocessing technology is employed to engineer the SnO2 microwire arrays (MWAs) thin film. The obtained UV PDs based on SnO2 MWA films exhibit enhanced responsivity and ultrafast response in the UV region. Under light irradiation with a wavelength of 365 nm, the optimized responsivity and rising/decaying time reach 1.62 A/W and 0.89/2.3 ms with the bias voltage of 5 V. The results demonstrate that the SnO2 MWA film can serve as a high-performance photodetector in the UV region.

Growth of Low-defect Si-Doped Ga2O3 Film on Fluorine-doped Tin Oxide Substrate for Self-powered and High-performance Ultraviolet Photodetector

Growth of Low-defect Si-Doped Ga₂O₃ Film on Fluorine-doped Tin Oxide Substrate for Self-powered and High-performance Ultraviolet Photodetector

O, N co-doped CuCrO2 as efficient hole transport layer for high-performance ultraviolet photodetectors

The optoelectronic properties and film-formation characteristics of CuCrO2 are optimized through oxygen (O) and nitrogen (N) co-doping using the space-limited domain annealing method in ambient air. After O, N co-doping at 100 °C, the conductivity of CuCrO2 is enhanced due to a decrease in trap-state density and an increase in hole concentration, thereby facilitating carrier transport. With a work function (WF) of 5.24 eV and an electron affinity (χ) of 2.29 eV, the CuCrO2 films serves as both a hole transport layer (HTL) and an electron-blocking layer, playing a pivotal role in enhancing photogenerated holes extraction while suppressing nonradiative charge recombination at the heterojunction interface. Consequently, the responsivity and detectivity of the device with FTO/TiO2 NRs/O, N co-doped CuCrO2/Au structure reach 188 mA W−1 and 3.14 × 1013 cm Hz1/2 W−1 in self-powered mode, respectively. Simultaneously, the rise/decay time is reduced to just 31.2/32.1 ns. Furthermore, after applying a bias of − 2 V, the photodetector demonstrates significantly improved performance with a responsivity of up to 5 × 105 mA/W (365 nm, 0.97 mW cm−2) and an apparent quantum efficiency of ∼30,000%. These results highlight the promising potential of utilizing O, N co-doped CuCrO2 HTL for constructing high-performance optoelectronic devices.

Vapor‐phase anion‐exchange strategy‐assisted high-performance CsPbCl3 perovskite photodetectors for ultraviolet imaging applications

CsPbCl3 perovskite holds potential for application in the field of ultraviolet (UV) detection due to its exceptional response to UV light and resistance to UV-induced oxidation. However, existing CsPbCl3 films mostly require high-temperature and high-pressure conditions for their preparation. In this investigation, we introduce a CsPbCl3 photodetector based on the anion exchange method, featuring a vertical structure of FTO/TiO2/CsPbCl3/Au. This proposal aims to alleviate challenges in film formation and enhance film quality. To enhance photoresponse, a TiO2 transport layer is employed to modify the surface defects. Experimental results demonstrate a significant reduction in carrier recombination probability, decrease the dark current by three orders of magnitude, and improve the on/off ratio by 6.17 × 103 times of the device. The optimized device achieves an on/off ratio of 2.04 × 105 under an illumination intensity of 39.8 mW/cm2, exhibiting a response time of 4.70/1.91 ms and a detectivity of 2.72 × 1012 Jones. Owing to its high performance, the potential of this proposed photodetector can be extended for use in weak-light UV imaging. Our research offers a feasible method for the scalable production of self-powered, high-performance UV photodetectors.

High-performance self-powered ultraviolet photodetector based on PVK/amorphous-WO3 organic-inorganic heterojunction

Ultraviolet (UV) photodetectors have found wide-ranging applications, ranging from optical communications to chemical detection. High performance UV photodetectors that can be self-powered are highly desirable in many applications as they can minimize energy consumption during operation. Herein, a self-powered UV photodetector, which consisted of poly(9-vinylcarbazole) (PVK)/amorphous-WO3 organic-inorganic heterojunction with PEDOT:PSS as a hole transport layer, was fabricated using a two-step method at low temperature. The effect of WO3, PVK and PEDOT:PSS films on the performances of the photodetector was also investigated. Under optimized parameters, the PEDOT:PSS/PVK/WO3 photodetector exhibited a maximum responsivity of 12.41 AW−1, specific detectivity of 1.80 × 1013 Jones, photo-dark current ratio of 103 at reverse bias and typical rectification characteristic when exposed to 365 nm light irradiation. The photoelectric conversion mechanism of this novel PVK/WO3 heterojunction is discussed using energy band diagrams. This work presents a method to produce a high performance WO3-based heterostructure at low temperature, which has the potential for UV imaging.

Facile fabrication of low-defect spinel zinc ferrite oxide thin film for high-performance ultraviolet photodetector

ZnFe2O4 (ZFO) has gained much attention for numerous applications such as photocatalysis and lithium-ion batteries owing to its unique magnetic, optical, and electrical properties, low toxicity, and high chemical stability. However, current research on this material for the development of solid-state photodetectors is insufficient. For the first time, a high-purity and compact ZFO thin film was prepared via a simple sol-gel method and used as an efficient n-type photoactive material for ultraviolet A (UVA) detection. When ZFO is coupled with a p-type polymer, the high-quality p-n heterojunction can be used as a self-powered UV detector with a high on/off ratio of > 103, excellent detectivity of 3 × 1011 Jones, and a linear relationship between the photocurrent and light intensity. Accordingly, this study suggests that the novel ZFO-based photodiode prepared via a facile process could be industrially scalable and employed in practical UV detection applications.

Observation of photoelectric-induced microplasma avalanche breakdown in AlGaN ultraviolet photodiode with separate absorption and multiplication structure

Amplification of weak ultraviolet signals has always been a challenging issue to design and fabricate high-performance ultraviolet photodetectors. Here, we observe a distinctive microplasma breakdown behavior in AlGaN-based ultraviolet avalanche photodiodes with artificial mesa architecture. At 107 V breakdown voltage, the photocurrent increases sharply whereas dark current intriguingly remains at the extremely low level of 0.1 nA as the applied voltage increases. Simultaneously, a significant blue luminescence phenomenon is observed at the mesa edge of photodiode at breakdown voltage, indicating the occurrence of microplasma breakdown. Ultimately, the microplasma avalanche photodiode achieves a record-high avalanche gain of 3 × 106 with light–dark current ratio readily exceeding 107. Kelvin probe force microscopy was employed to reveal the physical mechanism of localized avalanche breakdown induced by photoelectric effects and elaborate the microplasma discharge process, which is related to surface states. The unprecedented detection mode of photocurrent triggering avalanche events while remaining low dark current is anticipated to effectively shield the background noise and amplify ultraviolet signals. It is worth further research to explore its possibility on high-sensitivity ultraviolet photodetection.

Spherulitic Crystallization of CsCu2I3 for High Performance Ultraviolet Photodetectors.

Ternary copper halides have become promising materials for UV photodetection due to their stability and eco-friendliness. However, the uncontrollable crystallization induces high-concentration defects in these films, inherently limiting further improvement in device performance. Herein, we reveal the antisolvent-assisted crystallization kinetics mechanism of CsCu2I3 during the film-forming process. The nucleation rate is manipulated by adjusting precursor supersaturation using different antisolvents, resulting in decreased density and preferential orientation of the nuclei within the wet film. Subsequent annealing leads to a homogeneous and low-defect CsCu2I3 film with 40-μm-scale spherulites. A resulting visible-blind ultraviolet photodetector exhibits a responsivity of 8.73 A W-1, a specific detectivity of 5.28 × 1012 jones, and a response speed of 1.12 ms. The unencapsulated photodetector shows negligible degradation of responsivity in ambient air (∼70% humidity) for one month. Moreover, the flexible device with a responsivity of 420.2 mA W-1 and a detectivity of 1.18 × 1012 jones also shows excellent bending stability.