Light Density Research Articles

EXTH-76. TRANSLATIONAL BARRIERS IN 5-ALA PHOTODYNAMIC THERAPY FOR GLIOMAS: A SYSTEMATIC REVIEW OF THE IN VIVO LANDSCAPE AND FUTURE DIRECTIONS FOR CLINICAL APPLICABILITY

Abstract INTRODUCTION Photodynamic therapy (PDT) is an emerging investigational therapeutic for gliomas marked by variable success. Several strategies to increase its efficacy have been attempted, and although promising, challenges that have hindered translational progress persist. The objective of this study was to analyze translational barriers through a systematic review and appraisal of the in vivo literature. Method: PRISMA guidelines were utilized to identify studies that reported translational in vivo data of 5-aminolevulinic acid (5-ALA) PDT in murine glioma models. Databases were searched from inception to 2022, using the terms: “photodynamic therapy” AND (“5-ALA” OR “ALA” OR “PPIX”) AND “in vivo” AND (“glioma” OR “glioblastoma” OR astrocytoma”). Study design parameters were appraised, and mechanistic and translational outcomes across all studies were evaluated and compared. Result: Eight studies (2002-2019) were included. The most common animal model used was immunosuppressed rats orthotopically implanted with glioma cells. Only two studies used syngeneic models. No studies validated findings in external cohorts or patient-derived xenografts. Experimental light power densities ranged widely from 0.5-100mW/ cm2. Only three studies utilized a longitudinal delivery strategy, and all found significantly decreased tumor volume and increased survival compared to high-dose single-session PDT. For mechanistic endpoints, only one study investigated the impact of PDT on the immune response, finding increased TME CD8+ T-cell infiltration in the experimental group. Safety endpoints, including hemorrhage, elevated intracranial pressure (ICP), and off-target cortical damage, were measured in only three studies, in which high power densities were associated with increased hemorrhage and elevated ICP. CONCLUSION While in vivo evidence for 5-ALA PDT is compelling, this appraisal uncovers discrepancies in power densities, lack of validation in putative translational models, and limited understanding of PDT impact on the immune response and TME. Future preclinical investigations that address these barriers will offer distinct and necessary steps toward effective clinical translation.

The effect of light intensity, spectrum, and photoperiod on the physiological performance of Asparagopsis taxiformis tetrasporophytes

Over the last several years there has been increased interest in large scale cultivation of the red seaweed Asparagopsis taxiformis due to its ability to reduce methane emissions in ruminant animals. However, research focused on developing strategies to optimize culture conditions for this alga is still relatively scarce. Both light quality and quantity are widely known to differentially influence any alga's photosynthetic rates, metabolic budgets and ultimately biomass and bio-active compound production. Optimization of cultivation conditions for algae requires the understanding and fine-tuning of light parameters including Photon Flux Density (PFD), light spectrum, and photoperiod, as well as culture density which largely governs light quantity (PFD) and quality (spectrum) within the culture. Here we explore the effects of light intensity, spectral light distribution, and day length on the physiological performance of the tetrasporophyte stage of A. taxiformis in culture using a series of experiments. The results were used to characterize the optimal light and biomass density range for cultivation, and a model was developed to optimize the light path in a cultivation vessel. Spectral light optimization revealed a significant reduction in cyanobacterial contamination for cultures illuminated with blue LED light. Artificially extending light duration longer than 12 h per day did not improve algal growth. The insights gained from these experimental results may be used to inform the design of tank-based A. taxiformis cultivation systems to support high yield and stable production of this emerging commercial crop.

Photocurable High-Energy Polymer-Based Materials for 3D Printing

Digital light processing (DLP) or stereolithography is the most promising method of additive manufacturing (3D printing) of products based on high-energy materials due to, first of all, the absence of a high-temperature impact on the material. This paper presents research results of an ultraviolet (UV)-cured urethane methacrylate polymer containing 70 wt.% of high-energy solid powder based on ammonium salts, which is intended for digital light processing. Polymerization of the initial slurry is studied herein. It is shown that the addition of coarse powder transparency for the UV radiation to resin increases its curing depth. The thickness of the layer, which can polymerize, varies from 600 µm to 2 mm when the light power density ranges from 20 to 400 mJ/cm2, respectively. In DLP-based 3D printing, the obtained material density is 92% of the full density, while the compressive strength is 29 ± 3 MPa, and the ultimate tensile strength is 13 ± 1.3 MPa. The thermogravimetric analysis shows the decrease in the thermal decomposition temperature of UV-cured resin with high-energy additives compared to the thermal decomposition temperatures of the initial components separately. Thermal decomposition is accompanied by intensive heat generation. The burning rate of obtained samples grows from 0.74 to 3.68 mm/s, respectively, at the pressure growth from 0.1 to 4 MPa. Based on the results, it can be concluded that DLP-based 3D printing with the proposed UV photocurable resin is rather promising for the fabrication of multicomponent high-energy systems and complex profile parts produced therefrom.

Advanced Design of a III‐Nitride Light‐Emitting Diode via Machine Learning

AbstractGallium nitride (GaN)‐based light‐emitting diodes (LEDs) have obtained great market success in the past 20 years. However, the traditional research paradigm, i.e., experimental trial‐and‐error method, no longer adapts to the industry development. In this work, an efficient approach is demonstrated to design and optimize GaN‐based LED structures via machine learning (ML). By using the dataset of GaN‐based LED structures over the past decade to train four typical ML models, it is found that the convolutional neural network (CNN) provides the most accurate prediction, with a root mean square error (RMSE) of 1.03% for internal quantum efficiency (IQE) and 11.98 W cm−2 for light output power density (LOPD). Based on the CNN model, 1) the feature importance analysis is adopted to reveal the critical features for LED performance; 2) the predicted trends of IQE and LOPD match well with the physical mechanism, being consistent with the experimental and simulation results; and 3) a high‐throughput screening is demonstrated to predict the properties of over 20 000 structures within seconds to obtain high efficiency LED structures. This ML‐based LED design method enables direct guiding of the LED structure optimization in terms of key parameter selection during manufacturing and greatly accelerates the development cycle of GaN‐based LEDs.

Classical calculation of differential cross section for a beam deflected by a concentric refractive index field.

Ray tracing is a fundamental geometric-optics issue which gives a single ray path but seldom presents the collective behavior of light. The optical field distribution usually involves the calculation of an electromagnetic field and is rarely discussed from the perspective of geometric optics. However, in this paper, we show for a concentric medium with spherically symmetric refractive index, how the relative angular distribution of refractive beams can be obtained from the pure classical geometric optics method. As a measurement of the distribution, we introduce the concept of the differential cross section (DCS), which can be calculated from the relation between aiming distance and deflecting the angle of the ray. We present a general method to solve this relation from both Snell's law in a constant medium and the optical Binet equation (OBE) in a gradient-index (GRIN) medium. Even without observing the collective traces, the DCS can independently give a quantitative description for the deflected light density of concentric media at different directions. It may act as a reference index for the design of beam deflector.

Far-red light mediates light energy capture and distribution in soybeans (Glycine max L.) under the shade

Shade avoidance syndrome (SAS) is an important measure of how plants respond to shade. Shade conditions are characterized by low light density and low red-to-far-red light (R/FR) ratio. However, low light intensity and low R/FR ratio play considerable and diverse roles in SAS. In the present study, soybean plants were grown in the presence and absence of additional FR at two light levels to investigate the different effects on soybean plants. Compared with normal light intensity, net photosynthetic rate significantly decreased in low light, but increased in low R/FR ratio. Chlorophyll a fluorescence transient curves showed that the absorption of light flux increased under low light intensity and low R/FR ratio, whereas the number of photo reaction centers decreased under low light intensity. In addition, the content of porphyrins and chlorophyll metabolites (magnesium protoporphyrin IX, protochlorophyllide, and chlorophyll a and b) was significantly enhanced by low light intensity and the relative gene expression levels of protoporphyrin IX magnesium chelatase, chlorophyll a oxygenase and protochlorophyllide oxidoreductases involved in the porphyrin pathway were significantly increased. The inhibitory effects of low light on the photosynthetic rate and biomass of soybean plants were alleviated by a low R/FR ratio. A low R/FR ratio optimized light capture and achieved efficient light energy utilization under low light intensity by fine-tuning the chlorophyll level and the relative gene expression level of critical chlorophyll biosynthesis-related enzymes.

A wide ultraviolet spectra response photodetector based on epitaxial growth of highly-oriented ε-Ga2O3 crystal on diamond substrate

In recent years, diamond has shown great potential in solar-blind ultraviolet (UV) photodetection due to its ultrawide bandgap (∼ 5.5 eV) and other superior semiconductor properties. However, the response region of diamond photodetector is usually smaller than 230 nm, which cannot cover the whole solar-blind region from 200 to 280 nm. In this work, an ε-Ga2O3/diamond photodetector with wide spectra responsivity from 210 (or even lower) to 260 nm was fabricated. High-quality ε-Ga2O3 film with columnar crystal was epitaxially grown on single crystalline CVD diamond substrate by pulse laser deposition (PLD). TEM characterization revealed that the ε-Ga2O3 film grew along the <001> orientation on diamond (100) substrate. The deep ultraviolet (DUV) photodetector based on the ε-Ga2O3/diamond structure showed a high light-to-dark ratio over 5.7 × 104 and good linear response to the incident light power density from 10 to 400 mW/cm2. Moreover, compared to other photodetectors, the fabricated ε-Ga2O3/diamond photodetector achieved high responsivity and wide spectra response region from 210 to 260 nm, with high solar-blind rejection ratio of 104 (R 240/R 280) and 165 (R 210/R 280), respectively. The extension of spectra region with high responsivity of the ε-Ga2O3/diamond photodetector can be attributed to the thin thickness of ε-Ga2O3 film (around 200 nm) and parts of the DUV light were absorbed by diamond. The high responsivity and wide spectra response region indicate the fabricated ε-Ga2O3/diamond photodetector can be used for the detection of ultraviolet in the most of the DUV region.

Photodiode behavior and capacitive performance of ZnO nanoflakes synthesized by electrochemical deposition

ZnO flake interlayers were fabricated by the electrochemical deposition technique on p-Si to obtain Au/ZnO/p-Si heterostructures for Schottky-type photodiode applications and to test the capacitive performance of the structures. ZnO flake structures were investigated by x-ray diffractometry and scanning electron microscopy measurements, and their crystalline and flake-like structures were confirmed. The Au/ZnO/p-Si heterostructures were characterized by current–voltage (I–V) measurements for various illumination densities of light from dark to 150 mW cm−2. Various heterostructure parameters such as the ideality factor, barrier height, series resistance and rectifying ratio (RR) values were determined by I–V characteristics. The heterostructure exhibited a high RR of 6.85 × 103. The detection parameters revealed 0.49 mA W−1 responsivity and 2.69 × 109 Jones specific detectivity values. Furthermore, capacitance–voltage (C–V) measurements were employed to obtain the capacitive behavior of the Au/ZnO/p-Si heterostructure at various frequencies. Based on these results, Au/ZnO/p-Si heterostructures have potential for photodiode applications.

Comparison of Al/TiO2/p-Si and Al/ZnO/p-Si photodetectors

The importance of the photodetectors has grown due to their potential in the automation system and optical communications. We fabricated Al/TiO2/p-Si and Al/ZnO/p-Si Schottky-type photodetectors. TiO2 and ZnO interlayers were grown by atomic layer deposition (ALD). The photodetection properties of these devices were studied and compared by I–V and I-t measurements for various light power densities and various wavelengths. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectra were employed to determine morphological and elemental analysis of the TiO2 and ZnO interlayers. While the SEM images showed smooth surfaces, EDX spectra approved successful synthesis of the TiO2 and ZnO interlayers with good stoichiometry. The diode parameters such as ideality factor, series resistance and barrier height values were calculated and compared in detail. The responsivity and detectivity of the fabricated photodetectors were determined as a function of illumination power density and wavelength. The responsivity values of the Al/TiO2/p-Si and Al/ZnO/p-Si photodetectors were determined as 0.02 and 0.76 A/W, respectively. Both photodetectors exhibited good performance for visible light. However, Al/ZnO/p-Si photodetector reached 173.08% external quantum efficiency (EQE) for 550 nm. According to results, Al/ZnO/p-Si photodetector exhibited better detection performance than Al/TiO2/p-Si.

Spatial association between socio-economic health service factors and sepsis mortality in Thailand.

Sepsis is a significant global health issue causing organ failure and high mortality. The number of sepsis cases has recently increased in Thailand making it crucial to comprehend the factors behind these infections. This study focuses on exploring the spatial autocorrelation between socio-economic factors and health service factors on the one hand and sepsis mortality on the other. We applied global Moran's I, local indicators of spatial association (LISA) and spatial regression to examine the relationship between these variables. Based on univariate Moran's I scatter plots, sepsis mortality in all 77 provinces in Thailand were shown to exhibit a positive spatial autocorrelation that reached a significant value (0.311). The hotspots/ high-high (HH) clusters of sepsis mortality were mostly located in the central region of the country, while the coldspots/low-low (LL) clusters were observed in the north-eastern region. Bivariate Moran's I indicated a spatial autocorrelation between various factors and sepsis mortality, while the LISA analysis revealed 7 HH clusters and 5 LL clusters associated with population density. Additionally, there were 6 HH and 4 LL clusters in areas with the lowest average temperature, 4 HH and 2 LL clusters in areas with the highest average temperature, 8 HH and 5 LL clusters associated with night-time light and 6 HH and 5 LL clusters associated with pharmacy density. The spatial regression models conducted in this study determined that the spatial error model (SEM) provided the best fit, while the parameter estimation results revealed that several factors, including population density, average lowest and highest temperature, night-time light and pharmacy density, were positively correlated with sepsis mortality. The coefficient of determination (R2) indicated that the SEM model explained 56.4% of the variation in sepsis mortality. Furthermore, based on the Akaike Information Index (AIC), the SEM model slightly outperformed the spatial lag model (SLM) with an AIC value of 518.1 compared to 520.

Sorptivity Analysis of Lightweight Concrete Based on Fly Ash and Bottom Ash

Lightweight concrete has a density lower than conventional concrete, which ranges between 1,400-1,800 Kg/cm3. The use of lightweight concrete as a more sustainable construction material continues to be developed to reduce the weight of the building. Fly ash as a residue from coal combustion has a high SiO2 content as a cement substitute. Bottom ash with a light density can also be used as a substitute for fine aggregate. Sorptivity test in lightweight concrete aims to determine concrete's ability to absorb water and how the pores in concrete behave. Sorptivity testing was carried out by a 5x5x5(cm3) mortar sample that was immersed in water. Then the mortar was weighed based on time intervals of 1, 5, 10, 20, 30, and 60 minutes, then continued for 2, 3, 4, 5, and 6 hours and 1, 2, 3, 4, 5, 6, 7, and 8 days. The results showed that the use of fly ash and bottom ash could increase the sorptivity value in the mortar up to 0.45%, where the function of the fly ash and bottom ash is to fill the pores in the mortar so that the water content that seeps into the mortar is reduced. Thus, the use of fly ash and bottom ash to support ecologically friendly and lighter building results in more sustainable material properties.

Selective Growth of MAPbBr3 Rounded Microcrystals on Micro-Patterned Single-Layer Graphene Oxide/Graphene Platforms with Enhanced Photo-Stability.

The synergistic combination of hybrid perovskites with graphene-related materials is leading to optoelectronic devices with enhanced performance and stability. Still, taking advantage of the solution processing of perovskite onto graphene is especially challenging. Here, MAPbBr3 perovskite is grown on single-layer graphene/graphene oxide (Gr/GO) patterns with 120 µm periodicity using a solution-processed method. MAPbBr3 rounded crystals are formed with sizes ranging from nanometers to microns, either forming continuous films or dispersed particles. A detailed morphological and structural study reveals a fully oriented perovskite and very different growth habits on the Gr/GO micro-patterns, which we relate to the substrate characteristics and the nucleation rate. A simple method for controlling the nucleation rate is proposed based on the concentration of the precursor solution and the number of deposited perovskite layers. The photoluminescence is analyzed in terms of the crystal size, strain, and structural changes observed. Notably, the growth on top of Gr/GO leads to a huge photostability of the MAPbBr3 compared with that on glass. Especially outstanding is that of the microcrystals, which endure light densities as high as 130 kW/cm2. These results allow for anticipating the design of integrated nanostructures and nanoengineered devices by growing high-stability perovskite directly on Gr/GO substrates.

Canopy tree mortality depends on the proportion of crown exposed to sunlight, but this effect varies with species' wood density

AbstractUnderstanding what drives changes in tree mortality as well as the covariates influencing trees' response is a research priority to predict forest responses to global change. Here, we combined drone photogrammetry and ground‐based data to assess the influence of crown exposure to light (relative to total crown area), growth deviations (relative to conspecifics), tree size, and species' wood density (as a surrogate for light‐demanding and shade‐tolerant life‐history strategies) on the mortality of 984 canopy trees in an Amazon terra firme forest. Trees with lower wood density were less prone to die when their proportion of crown was more exposed to sunlight, but this relationship with relative crown exposure weakened and slightly reversed as wood density increased. Trees growing less than their species average had higher mortality, especially when the species' wood density decreased. The role of wood density in determining the survival of canopy trees under varying light conditions indicates differential responses of light‐demanding versus shade‐tolerant species. Our results highlight the importance of accounting for life‐history strategies, via plant functional types, in vegetation dynamic models aiming to predict forest demography under a rapidly changing climate.Abstract in Spanish is available with online material.

Spatial assessment of nighttime anthropization in the Comoé National Park in Côte d’Ivoira (West Africa)

Abstract Protected areas play a crucial role in preserving biological diversity, providing ecosystem services, and regulating hydroclimatic processes. However, the environmental balance of these areas is increasingly under threat due to rapid population growth, high demand for natural resources, and the effects of global warming. To address this, sustainable management of protected areas is essential. This study aims to develop a methodology for monitoring and assessing levels of nocturnal anthropogenic aggression in the Comoé National Park (CNP) in Côte d’Ivoire. By using geospatial data from the Day/Night Band of the Visible Infrared Imaging Radiometer Suite (VIIRS/DNB), the study characterizes the nocturnal anthropization of CNP through the use of several indices. First, light reflectance density is used to identify nighttime light emission foci. Second, the lighted area density index (LADI) is employed to understand the nature of nocturnal activities taking place within CNP, as indicated by artificial light at night (ALAN). Finally, the light intensity index (LII) is used to evaluate the degree of influence of nocturnal anthropogenic activities on biodiversity. The study also found important activities through LADI and observed a high level of light pollution in CNP. Ultimately, the findings of this study indicate that there is a significant level of nocturnal anthropization within CNP, highlighting the need for effective management and conservation efforts in the area.

The Characterization of Mechanical and Chemical Properties of Recycled Styrofoam Waste Employing Extrusion Process

&lt;p&gt;&lt;em&gt;Styrofoam waste is a polystyrene plastic-based waste in the form of foam with low density. Scavengers or recyclers are not interested in receiving styrofoam waste because of its light density which makes it ineffective in transportation and storage. Styrofoam waste can actually be converted into solid polystyrene products through a thermal-extrusion process but data regarding the optimum operating temperature and the characteristics of the resulting solid polystyrene products are not yet available. The purpose of this study was to investigate the properties of solid polystyrene products resulting from recycled styrofoam waste and determine the optimum temperature of the thermal-extrusion treatment process to be compared with the characteristics of the original polystyrene based on the results of tensile and impact tests. In this study, the processing was carried out using the thermal-extrusion method; Styrofoam is melted and extruded into a mold to produce polystyrene solids. The research was carried out with variations in extrusion temperature at 180°C, 200°C, and 220°C. The polystyrene solids are then molded into tensile and impact test specimens by injection molding. The results showed that the optimal extrusion temperature was 200°C with tensile and impact strength values of 27.55 MPa and 1,069 j/m2, respectively. Compared to the original polystyrene, the tensile strength value is 25.3% lower and the impact strength value is 29.5% lower. The decrease in the tensile and impact strength values is due to the shortening of the molecular bonds in the recycled polystyrene during the thermal-extrusion treatment process. Even though the tensile strength and impact are still lower, the use of styrofoam waste using the thermal-extrusion method has the potential to be developed at the production and commercialization stage because the resulting product has good economic value and can also reduce the use of original polystyrene and at the same time can solve the problem of styrofoam waste.&lt;/em&gt;&lt;/p&gt;

A Reversed Inverse Faraday Effect

The inverse Faraday effect is a magneto‐optical process allowing the magnetization of matter by an optical excitation carrying a non‐zero spin. In particular, a right circular polarization generates a magnetization in the direction of light propagation and a left circular polarization in the opposite direction to this propagation. Herein, it demonstrates that by manipulating the spin density of light, i.e., its polarization, in a plasmonic nanostructure, a reversed inverse Faraday effect is generated. A right circular polarization will generate a magnetization in the opposite direction of the light propagation, a left circular polarization in the direction of propagation. Also, it demonstrates that this new physical phenomenon is chiral, generating a strong magnetic field only for one helicity of the light, the opposite helicity producing this effect only for the mirror structure. This new optical concept opens the way to the generation of magnetic fields with unpolarized light, finding application in the ultrafast manipulation of magnetic domains and processes, such as spin precession, spin currents, and waves, magnetic skyrmion or magnetic circular dichroism, with direct applications in data storage and processing technologies.

The Impact of Physical Home Environment and Patient Age on Pulmonary Tuberculosis Incidence in Slum Settings

Pulmonary tuberculosis continues to be a major public health issue in Indonesia and worldwide, aligning with sustainable health development goals. Among the five areas with high incidence rates, Kotabaru Regency is facing an increase in suspected cases, particularly in densely populated areas. In 2022, there was a noticeable rise in suspected cases of pulmonary TB, reaching 133, with 89 cases concentrated in the slums of Kotabaru Regency. The objective of this study is to investigate the impact of factors such as the physical house environment and patient age on the incidence of pulmonary tuberculosis in the slums within the working area of the Dirgahayu Health Center in Kotabaru Regency for the year 2023. This analytical observational study utilized a case-control approach with 46 samples and employed instruments such as the Hygrometer, Luxmeter, and Rollmeter. The dependent variable was the incidence of pulmonary tuberculosis, while independent variables included occupancy density, ventilation, home lighting, humidity, and age. Bivariate analysis using the Chi-Square test and multivariate analysis using the Multiple Logistic Regression Test were conducted. The results of the Chi-Square test showed a correlation between age (p = 0.437), home lighting (p = 0.008), ventilation (p = 0.000), occupancy density (p = 0.003), and the incidence of pulmonary tuberculosis. Home lighting, ventilation, and occupancy density demonstrated a significant correlation with tuberculosis incidence, while patient age did not have a substantial influence. Conclusions regarding humidity could not be drawn due to insufficient data that met the requirements. Ventilation was found to be the most influential variable, with an Exp(B) value of 10.961.

Red InGaN Micro-LEDs on Silicon Substrates: Potential for Multicolor Display and Wavelength Division Multiplexing Visible Light Communication

Red micro light-emitting diodes (micro-LEDs) on silicon substrates are crucial for the realization of large-scale, high-quality, low-cost micro-LED displays, and are also beneficial for high-speed visible light communication (VLC). In this letter, micro-LEDs with different sizes were fabricated. The maximum light output power density of the 20 μm pixel can reach 3.36 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is 14 times higher than that of the largest pixel (150 μm). By adjusting the pixel size and injection current, a direct color shift from red to green can be observed. Moreover, multicolor emission with uniform brightness can be realized by adjusting duty cycle, which has broad application prospect in monolithic, multicolor displays. Despite the significant blue shift phenomenon, the peak wavelength of all pixels is still greater than 630 nm at the current density of 100 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which means that red light can be emitted in a large current density range to meet various application scenarios requiring different driving conditions. We have realized red, yellow and green micro-LED transmitters on Si substrate by changing the driving current density and modulation bandwidth up to 533.15 MHz is achieved when emitting green light. This is the report of red-emission micro-LEDs on Si substrates for visible light communication for the first time. And we proposed a proof-of-concept monolithic, multicolor wavelength division multiplexing scheme that achieved a total allowable transmission data rate of 2.35 Gbps. Such micro-LED is expected to be applied in multicolor displays, high-speed multi-channel VLC, color-tunable light sources, etc. In particular, due to its high integration and miniaturization, it is expected to be used in future practical application scenarios such as wearable communication devices and smartwatches.

Light-triggered 2D electron gas in a GaN-based HEMT with sandwiched p-GaN layers.

In this work, a p-n junction-coupled metal-insulator-semiconductor (MIS) normally-off high-electron-mobility transistor (HEMT) UVPD is proposed. A two-dimensional electron gas (2DEG) at the AlN/U-GaN interface is entirely depleted with a dark current of 1.97 × 10-11 A because of the design of the sandwiched p-GaN layers. Under 365 nm illumination, the 2DEG is light triggered at Vds = 1 V with a high light on/off ratio of over 107 at a light power density of 286.39 mW·cm-2. Meanwhile, it exhibits fast rise and decay times of 248.39 and 584.79 µs, respectively. Moreover, a maximum responsivity (R) of 2.33 A/W, a maximum EQE of 793%, and a D* of 1.08 × 1013 Jones are obtained at Vds = 1 V. This can be attributed to the built-in electric fields in the configuration, which accelerate the flow of photogenerated carriers into the AlN/U-GaN channel. Additionally, the device showcases stable durability, repeatability, and a low driving voltage, making it highly suitable for applications in UV communication and space exploration.

Modulation of carrier transport in bipolar response BDD/SnO2 p+-n heterojunction UV photodetectors

A unique band-to-band tunneling (BTBT) phenomenon has been discovered in heavily boron-doped diamond (BDD)/SnO2 p+-n heterojunctions. This phenomenon can be modulated by varying the bias voltage, changing the thickness of the SnO2 film, and adjusting the power density of incident UV light. The near-broken-gap band alignment of the BDD/SnO2 heterojunction and the existence of electrons in degenerate states in the valence band of BDD are the key to achieving BTBT. Moreover, BDD/SnO2 p+-n heterojunction UV photodetectors (PDs) prepared by radio-frequency magnetron sputtering exhibit a binary photoresponse, large open-circuit voltage (Voc-l), and high photo/dark current ratio (Ip/Id). Those behaviors can be produced through periodic on/off UV light irradiation and by changing tunneling, drift, and thermionic emission currents. Our work, which is the first to achieve a binary photoresponse by modulating BTBT in BDD/SnO2 heterojunctions, demonstrates the feasibility of extending BTBT theory to logical optoelectronic devices.