Solar-blind UV Research Articles

High-performance Ga2O3 solar-blind UV photodetectors via film growth regulation and surface state engineering

Gallium oxide (Ga2O3) with a wide bandgap is emerging as one of the most promising candidates for solar-blind photodetectors (SBPDs). However, the practical application of Ga2O3-based SBPDs is impeded by substantial defects-related leakage currents, sluggish response speed, and high-cost, making their practical applications face great challenges. Here, we proposed strategic films growth regulation and surface state engineering to grow high-quality yet economical β-Ga2O3 films, thereby achieving high-performance SBPDs. High-resolution transmission electron microscopy revealed the presence of high-quality films with an extremely regular arrangement of β-Ga2O3 (2‾01) planes. The full width at half maximum and root mean square roughness values are 0.07° and 0.716 nm, respectively. The β-Ga2O3 films demonstrated a significant reduction in VO concentrations after O2/N2 plasma treatment. This process can effectively minimize thermal damage to the sample surface while retaining highly reactive free radicals. The photocurrents of devices can be further enhanced, leading to a larger PDCRs of 8.6 × 107, through N2 plasma treatment. Moreover, the films effectually suppress the persistent photoconductivity effect with τr and τd values of 5.31/0.97 s and 0.49/0.87 s before and after N2 plasma treatment, respectively. We have demonstrated the influence mechanism of O2/N2 plasma treatment on photoelectronic performance. This study provides a practical approach to growing high-quality β-Ga2O3 films and preparing high-performance but low-cost Ga2O3-based SBPDs.

Fabrication of Al doped α-GaOOH nanorod arrays on FTO for self-powered photoelectrochemical solar-blind UV photodetectors

Al doped α-GaOOH nanorod arrays were grown on FTO via hydrothermal processes by using gallium nitrate and aluminum nitrate mixed aqueous solutions with fixed 1:1 mole ratio as precursors. With increasing the gallium nitrate precursor concentrations, the Ga/Al atom ratios in nanorod arrays increase from 0.36 to 2.08, and the length becomes much longer from 650 nm to 1.04 μm. According to the binding energy difference between Ga 2p3/2 core level and its background in x-ray photoelectron spectroscopy, the bandgap is estimated to be around 5.3 ± 0.2 eV. Al doped α-GaOOH nanorod array/FTO photoelectrochemical photodetectors show enhanced self-powered solar-blind UV photodetection properties, with the decrease of Ga precursor concentrations. The maximum responsivity at 255 nm is 0.09 mA W−1, and the fastest response time can reach 0.05 s. The improved photoresponse speed is ascribed from much shorter transportation route, accelerated carrier recombination by recombination centers, and smaller charge transfer resistance at the α-GaOOH/electrolyte interface with decreasing the gallium nitrate precursor concentrations. The stability and responsivity should be further improved. Nevertheless, this work firstly demonstrates the realization of self-powered solar-blind UV photodetection for α-GaOOH nanorod arrays on FTO via Al doping.

Highly Wavelength-Selective Self-Powered Solar-Blind Ultraviolet Photodetector Based on Colloidal Aluminum Nitride Quantum Dots.

Colloidal quantum dots are semiconductor nanocrystals endowed with unique optoelectronic properties. A major challenge to the field is the lack of methods for synthesizing quantum dots exhibit strong photo-response in the deep-ultraviolet (DUV) band. Here, a facile solution-processed method is presented for synthesizing ultrawide bandgap aluminium nitride quantum dots (AlN QDs) showing distinguished UV-B photoluminescence. Combined with the strong optical response in solar blind band, a solution-processed, self-powered AlN-QDs/β-Ga2O3 solar-blind photodetector is demonstrated. The photodetector is characterized with a high responsivity of 1.6mAW-1 under 0V bias and specific detectivity 7.60 × 10-11 Jones under 5V bias voltage with good solar blind selectivity. Given the solution-processed capability of the devices and extraordinary properties of AlN QDs, this study anticipates the utilization of AlN QDs will open up unique opportunities for cost-effective industrial production of high-performance DUV optoelectronics for large-scale applications.

Highly Sensitive Narrowband AlGaN Solar Blind Ultraviolet Photodetectors Using Polarization Induced Heterojunction Barrier

Highly Sensitive Narrowband AlGaN Solar Blind Ultraviolet Photodetectors Using Polarization Induced Heterojunction Barrier

Piezoelectricity Enhanced Self-Powered Solar-Blind Ultraviolet Photodetectors Based on Ga2O3/ZnO Heterojunction

Piezoelectricity Enhanced Self-Powered Solar-Blind Ultraviolet Photodetectors Based on Ga₂O₃/ZnO Heterojunction

Cadmium Hydroxyl Chloride with Balanced Band Gap and Second-Harmonic-Generation Response.

Ultraviolet (UV) nonlinear-optical (NLO) materials are crucial in laser technology due to their ability to modulate light frequency. In this work, when d10 cations, hydroxyl groups, and Cl atoms were combined, a cadmium double salt, Cd(OH)Cl, was synthesized by a simple hydrothermal method. It has a large phase-matched second-harmonic-generation (SHG) response at 1064 nm (2.5 × KDP) with a short UV-cutoff edge (260 nm), which can be applied in a solar-blind UV band. Theoretical calculations suggest that [Cd(OH)3Cl3] groups lead to a large SHG response. Our work may shed light on the exploration of new NLO materials in metal hydroxyl chlorides.

Electronic transport and optical properties of five different phases (α, β, ε, δ and γ) of Ga2O3: A first-principles study

In the field of power and ultraviolet devices, Ga2O3 becomes an emerging semiconductor due to its large energy bandgap and suitable optical absorption wavelength at solar blind ultraviolet band. In this work, the electronic and optical properties of five Ga2O3 polymorphs are investigated by the first-principles calculations to study their potential in ultraviolet devices. The geometry structures, electronic structure, optical and electronic transport properties of five polymorphs have been investigated through GGA + U approach and deformation potential theory. Based on the deformation potential theory, the anisotropic electron mobility of five Ga2O3 polycrystals is obtained by analyzing the parameters obtained from the first-principles calculation. TCAD simulations using calculation results before show the spectral response of MSM solar-blind detectors based on five polymorphs, and indicating that ε-Ga2O3 is the best candidate material for solar blind UV detector. This work provides theoretical insights for the preparation of different phase gallium oxide materials and devices.

Reduction of oxygen vacancies in Mg–N codoped Ga2O3 films for improving solar-blind UV photodetectors performance

Solar-blind photodetectors based on gallium oxide (Ga2O3) have shown possibilities in optical imaging, spatial communication, and other fields. The high oxygen vacancy (VO) content inherent in Ga2O3 film would inevitably result in poor photoelectric detection capability. This work suggests using a codoping for reducing VO concentrations in Ga2O3 films. In a N2O atmosphere, magnesium and nitrogen codoped gallium oxide (Mg–N:Ga2O3) films were grown using the pulsed laser deposition (PLD) technique on (0001) sapphire substrates. It is possible to produce codoped Ga2O3 thin films with low oxygen vacancy density and high crystalline quality by thoroughly examining and optimizing preparation conditions. Metal-semiconductor-metal (MSM) photodetectors were constructed using both pristine and Mg–N codoped Ga2O3 thin films as the active layer. The photodetector with a codoped active layer outperforms those with pristine Ga2O3, with a quick decay time of 20 ms, a high sensitivity of 2.61 × 105, and a high responsivity of 0.191 A/W under 254 nm UV light irradiation, highlighting the significance of the VO concentration decrease in the application of Ga2O3-based solar-blind photodetectors.

Self-powered α-GaOOH nanorod array/FTO photoelectrochemical photodetectors for solar-blind UV photodetection

We have grown α-GaOOH nanorod array/FTO structures with different precursor concentrations by hydrothermal processes without any seed layers. The optical bandgap is ∼5.1 eV, indicating their ability of solar-blind UV photodetection. Photoelectrochemical (PEC) properties of α-GaOOH nanorod array/FTO photodetectors as photoanodes show self-powered solar-blind UV photodetection. Due to the similar width of depletion regions of α-GaOOH nanorod array/FTO PEC photodetectors with changing the precursor concentrations, the peak responsivity is nearly the same. And they also show the similar response time (decay processes) ranging from 0.061s to 0.072s. Compared with the reported bare α-GaOOH nanorod arrays or heterojunctions, the maximum responsivity of 0.29 mA/W at 245 nm is comparable. However, fast collection speed without block of these seed layers between nanorod arrays and FTO results in faster response speed of 0.012 s in this work. Therefore, this article provides basic research in realizing high-performance self-powered α-GaOOH PEC photodetectors without seed layers.

Phase Transition and Bandgap Engineering of MgSnO Thin Films for Solar-Blind Ultraviolet Photodetector Applications

Phase Transition and Bandgap Engineering of MgSnO Thin Films for Solar-Blind Ultraviolet Photodetector Applications

Transmission enhancement in coupled nanohole and nanodisk arrays for solar blind UV filter

Extraordinary optical transmission (EOT) based on metallic nanohole array has great potential for optical filtering, owing to its spectral selectivity and structure-dependent tunability. However the transmittance of EOT is relatively low owing to the large loss of the metal film, particularly in the UV waveband. Herein, we propose a high transmission narrowband ultraviolet filter based on aluminum compound nanostructures on a UV-grade fused silica substrate. These compound nanostructures are consisted of periodic nanodisk and nanohole arrays with the same period in a staggered rectangular arrangement. Numerical simulations using the finite-difference time-domain (FDTD) method have shown that the compound structures exhibit high transmittance of over 70% and a narrower bandwidth of less than 50 nm in the 200–300 nm spectral region compared with the conventionally EOT of pure metallic nanohole arrays. Moreover, a broad suppression in the wavelength ranges of 300 to 1100 nm was achieved. The enhanced performance is attributed to the coupling between the surface plasmon polariton (SPP) of nanohole arrays and the localized surface plasmon resonance (LSPR) of nanodisk arrays. The compound coupled nanostructures can be used in solar-blind ultraviolet detectors and the enhancement mechanism has potential for use in other spectral regions.

Self-powered solar blind ultraviolet photodetector based on amorphous (In0.23Ga0.77)2O3/bixbyite (In0.67Ga0.33)2O3 heterojunction

Self-powered solar-blind ultraviolet photodetectors are considered for potential applications in secure communication and space detection. However, high-quality p-type wide bandgap semiconductors are nonexistent due to the self-compensation effect, which makes the design of p-n homojunction photodetectors a challenging proposition to date. In this work, a self-powered solar-blind ultraviolet photodetector is fabricated and discussed, based on a novel heterojunction of (InxGa1−x)2O3 ternary alloy films with two different compositions, which has a flexible design and can be easily fabricated for different applications. The heterojunction consists of an amorphous (In0.23Ga0.77)2O3 on the top of a bixbyite (In0.67Ga0.33)2O3 film prepared by radio frequency magnetron sputtering. The amorphous (In0.23Ga0.77)2O3/bixbyite (In0.67Ga0.33)2O3 heterojunction photodetector exhibits a responsivity of 5.78 mA/W, a detectivity of 1.69 × 1011 cm Hz1/2 W−1, and a high solar-blind UV (248 nm)/visible light (450 nm) rejection ratio of 1.39 × 103 at zero bias, suggesting decent spectral selectivity and high performance. The responsivity and peak wavelength of this photodetector can be tuned by the film thickness of the amorphous (In0.23Ga0.77)2O3. This work provides a new design for self-powered solar-blind UV detectors based on ternary alloy heterojunctions.

High performance solar-blind UV detector with Mg0.472Zn0.528O/Mg0.447Zn0.553O double layer structure on MgO substrate.

Mg0.472Zn0.528O/Mg0.447Zn0.553O double layer structure UV detectors are made on single structure MgO substrate by PLD method, and the effect of different thickness top MgZnO layer on the UV response characteristics of the detector are studied. Compared with the single layer MgZnO detector that made by Mg0.3Zn0.7O target, the Mg0.472Zn0.528O/Mg0.447Zn0.553O double layer detector with 30 nm top layer, shows much higher deep UV response (21.3 A W-1at 265 nm), much smaller dark current(66.9 pA) and much higher signal-to-noise ratio (2.8 × 105) at 25 V bias voltage. And the device also shows relative high response (23.1 A W-1) at 235 nm deep UV light at 25 V bias voltage, which is mainly attributed by the bottom MgZnO layer with higher Mg composition. When the top layer is 66.7 nm thick, the response of the Mg0.472Zn0.528O/Mg0.447Zn0.553O detector reached 228.8 A W-1at 255 nm under 25 V bias voltage, the signal-to-noise ratio of which is 10573 under 20 V bias voltage, and the near UV response of the device is also big because of more h-MgZnO in top MgZnO layer. When the top layer reached 90.2 nm, there are much more h-MgZnO in the top MgZnO layer, the peak response of the Mg0.472Zn0.528O/Mg0.447Zn0.553O detector is just 6.65 A W-1at 320 nm under 25 V bias voltage, the signal-to-noise ratio of which is 1248. The high Mg composition bottom MgZnO decrease the dark current of the Mg0.472Zn0.528O/Mg0.447Zn0.553O detector, both the 2DEG effect of the double layer structure and the amplify effect of the mix-phase MgZnO top layer, increased theIuvand deep UV response of the Mg0.472Zn0.528O/Mg0.447Zn0.553O detector. Therefore, the double layer Mg0.472Zn0.528O/Mg0.447Zn0.553O detector is more sensitive at faint deep UV light compared with previous reported MgZnO detectors, and the MgxZn1-xO/MgyZn1-yO detector shows similarIuvand signal-noise-ratio at faint deep UV light as high-temperature fabricated AlxGa1-xN/AlyGa1-yN detectors.

Enabling Broadband Solar-Blind UV Photodetection by a Rare-Earth Doped Oxyfluoride Transparent Glass-Ceramic.

Oxyfluoride transparent glass-ceramics (GC) are widely used as the matrix for rare-earth (RE) ions due to their unique properties such as low phonon energy, high transmittance, and high solubility for RE ions. Tb3+ doped oxyfluoride glasses exhibit a large absorption cross section for ultraviolet (UV) excitation, high stability, high photoluminescence quantum efficiency, and sensitive spectral conversion characteristics, making them promising candidate materials for use as the spectral converter in UV photodetectors. Herein, a Tb3+ doped oxyfluoride GC isdeveloped by using the melt-quenching method, and the microstructure and optical properties of the GC sample are carefully investigated. By combining with a Si-based photo-resistor,a solar-blind UV detector is fabricated, which exhibits a significant photoelectric response with a broad detection range from 188 to 400nm. The results indicate that the designed UV photodetector is of great significance for the development of solar-blind UV detectors.

Measurement of sensitivity of solar blind UV cameras to solar light

Measurement of sensitivity of solar blind UV cameras to solar light

Enhanced performance of solar-blind UV detectors based on Ti3C2Tx/AlGaN heterojunction

Enhanced performance of solar-blind UV detectors based on Ti3C2Tx/AlGaN heterojunction

Influence of annealing pretreatment in different atmospheres on crystallization quality and UV photosensitivity of gallium oxide films.

Due to their high wavelength selectivity and strong anti-interference capability, solar-blind UV photodetectors hold broad and important application prospects in fields like flame detection, missile warnings, and secure communication. Research on solar-blind UV detectors for amorphous Ga2O3 is still in its early stages. The presence of intrinsic defects related to oxygen vacancies significantly affects the photodetection performance of amorphous Ga2O3 materials. This paper focuses on growing high quality amorphous Ga2O3 films on silicon substrates through atomic layer deposition. The study investigates the impact of annealing atmospheres on Ga2O3 films and designs a blind UV detector for Ga2O3. Characterization techniques including atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for Ga2O3 film analysis. Ga2O3 films exhibit a clear transition from amorphous to polycrystalline after annealing, accompanied by a decrease in oxygen vacancy concentration from 21.26% to 6.54%. As a result, the response time of the annealed detector reduces from 9.32 s to 0.47 s at an external bias of 10 V. This work demonstrates that an appropriate annealing process can yield high-quality Ga2O3 films, and holds potential for advancing high-performance solar blind photodetector (SBPD) development.

Mineral oil emulsion species and concentration prediction using multi-output neural network based on fluorescence spectra in the solar-blind UV band.

The accurate monitoring of oil spills is crucial for effective oil spill recovery, volume determination, and cleanup. Oil slicks become emulsified under the effects of wind and waves, which increases the consistency of the oil spills. This phenomenon makes oil spills more challenging to handle and exacerbates environmental pollution. In this study, the variation of the solar-blind ultraviolet (UV) fluorescence spectra obtained from simulated oil spills with different oil types and oil-water ratios was investigated. By designing and constructing a multi-angle excitation and detection system, an apparent fluorescence peak of the oil emulsions was observed at around 290 nm under 220 nm excitation. By utilizing competitive adaptive reweighted sampling (CARS) and multi-output neural network algorithms, both the types and concentrations of the emulsified oils were obtained simultaneously. The classification accuracy for identifying the oil type exceeds 98%, and the mean absolute percentage error (MAPE) for concentration regression is around 2%. The results indicate that active solar-blind UV fluorescence could become a supplementary method for on-site oil spill detection to achieve comprehensive monitoring of oil spills. This study provides potential applications for UV-induced fluorescence spectrometry in oil spill on-site monitoring during the daytime.

Ultrasensitive Narrowband Organic Phototransistor for Solar-Blind Ultraviolet Detection and Imaging

Solar-blind ultraviolet (SBUV) photodetectors has extensive applications in fields such as military operations, agriculture, and flame detection. However, most current ultraviolet detection is based on inorganic materials, and there is...

Investigation on the growth aspects and properties of rubidium hydrogen succinate hydrate single crystal for NLO applications.

A novel semiorganic nonlinear optical single crystal of rubidium hydrogen succinate hydrate (RbHSH) was grown at room temperature using the slow evaporation solution growth technique (SEST) with water as a solvent for nonlinear optical applications. The grown crystal is a triclinic system with a centrosymmetric space group of P1̄ and the compound is stabilized by intramolecular O-H-O and C-H-O bonding. FTIR spectral studies were used to determine the various functional groups present in the material. The optical transmission spectra of the grown crystal demonstrated that a transparency of 89%, with a low cut off wavelength of 240 nm and an energy band gap of 5.21 eV, which is beneficial to developing advanced photonic and optoelectronic devices in the solar blind UV area. The grown crystal is thermally stable upto 174 °C. The electrical properties of RbHSH crystal exhibit low dielectric loss and a low dielectric constant at high frequencies tends to have good optical characteristics. Mechanical analysis demonstrated that the grown crystal shows the normal indentation size effect (ISE) and falls into the hard material category with n = 1.4. Photoconductivity measurements revealed negative photoconductivity. Photoluminescence studies showed that RbHSH emits blue light with a wavelength of 484 nm. Hirshfeld surface analysis was used to analyze intermolecular interactions in the RbHSH crystal. The grown RbHSH crystal piezoelectric charge coefficient have been calculated (d33 = 13 pC N-1) and it is suitable for piezoelectric device applications. Under continuous-wave laser excitation, the third order nonlinear refractive index (n2), absorption coefficient (β), and susceptibility (χ(3)) of the RbHSH crystal were found to be 1.6639 × 10-12 (cm2 W-1), 1.1739 × 10-5 (cm W-1) and 4.86331 × 10-9 esu, respectively.