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Gain and response speed are two key performance parameters for high sensitivity photodetectors (PDs). However, the effect of incident light intensity on gain and transient response properties of AlGaN/GaN hetero-junction based PDs are still not fully understood. Here, we design and fabricate an AlGaN/GaN hetero-junction based ultraviolet (UV) PD with interdigitated electrodes formed by a conductive two-dimensional electron gas (2DEG) channel, which exhibits a low dark current of 2.92 × 10−11 A and a high responsivity of 3060 A/W at 10 V bias. The high-gain AlGaN/GaN 2DEG PD has a similar working mechanism to those of traditional phototransistors, but its device architecture is evidently simplified. By investigating the variation of gain and transient response characteristics of the 2DEG PD as a function of incident UV light intensity, it has been concluded that the gain of the PD in a low-light intensity region is dominated by hole accumulation-induced electron escape from the 2DEG, while in a high-light intensity region, the gain is dominated by photoconductivity effect and limited by carrier recombination. This study provides guidance for future practical applications of AlGaN/GaN-based PDs in complex UV illumination environments. [ABSTRACT FROM AUTHOR]

High-responsivity and energy-saving ultraviolet photodetectors become crucial components for modern optoelectronic information sensing and communication systems. This study presents an advanced self-powered MXene/GaN Schottky ultraviolet photodetector that features a high-quality van der Waals interface to enhance photoresponsivity. The photodetector exhibits a high responsivity of 681.6 mA W−1 and a significant detectivity of 7.65 × 1013 Jones at zero bias. In a self-powered mode, the detector can operate robustly even under dim illumination (0.15 μW cm−2) due to the excellent Schottky contact and low amount of defect states at the MXene/GaN interface, which presents a strong intrinsic electric field. The photodetector has a high ultraviolet/visible rejection ratio (R360 nm/R400 nm) of 3.9 × 103 and a signal to noise ratio (SNR) of 2.4 × 105, which enable discrimination against visible light interference in real-world scenarios. We also demonstrated that the photodetectors worked well as ultraviolet signal receivers in an optical information communication system to accurately recognize pulsed signals transmitted from an ultraviolet light-emitting diode. These findings imply the great potential of van der Waals Schottky junctions between 2D MXenes and III-nitrides for high-performance photodetection and sensing in many integrated optoelectronic platforms. [ABSTRACT FROM AUTHOR]

Compared with long-term and continuous application of large amounts of chemical fertilizers, fertilizers with microbial organic nutrient sources can improve soil environment, increase soil fertility and increase crop yield. In view of the current low soil fertility and poor soil environment leading to low crop yield and instability in the arid regions of northwest China, the effects of organic fertilizer with microbial nutrient sources on soil nutrients and pumpkin yield were studied in 2022 and 2023 in this region. The fertilizer application level was used as control factor, with four treatments of low level (L), medium level (M), high level (H), and a conventional fertilizer control (CK). The results showed that the high application level of organic fertilizer was more beneficial to the growth of pumpkin, and the stem diameter, vine length, and leaf area of pumpkin under H treatment were the highest from 2022 to 2023. Compared to CK, the average soil bulk density was significantly decreased by 8.27–18.51% (P< 0.05); the soil organic carbon, available phosphorus, available potassium, and nitrate nitrogen under H treatment were increased by an average of 32.37%, 21.85%, 18.70%, and 36.97%, respectively. Under different organic fertilizer treatments, the pumpkin yield under M treatment was the highest, reaching 30926.18 kg·ha-1, followed by H treatment. compared to CK, M and H treatments increased the yield by 25.26% and 7.01%, respectively, and improved water use efficiency by 14.18% and 2.21%, respectively. Redundancy analysis (RDA) of soil nutrients, pumpkin growth dynamics and yield in 2022 and 2023 showed that soil organic carbon, available phosphorus, available potassium, nitrate nitrogen, and water use efficiency were significantly positively correlated with pumpkin yield (P<0.01). In conclusion, H and M treatments can improve soil fertility promote pumpkin growth and development, and ultimately increase pumpkin yield. In summary, medium organic fertilizer level (M=5700 kg·ha-1) is recommended as the fertilization scheme for local pumpkin cultivation. [ABSTRACT FROM AUTHOR]

Orientation-dependent substrates provide effective platforms for achieving α-Ga2O3 with low dislocation densities, whereas the associated strain and dislocation dynamics have not been fully explored. Herein, we investigated the evolution of growth mode, interfacial strain, and dislocation propagation in the α-Ga2O3 epitaxial layer with various orientations, grown by the halide vapor-phase epitaxy. Strain tensor theory and geometric phase analysis indicate that the m-plane α-Ga2O3 epitaxial layer exhibits the lowest misfit tensile strain, measured at εxx = 1.46% and εyy = 1.81%, resulting in the lowest edge dislocation density. The m-plane lattice exhibits an inclination of 33.60°, while the c-plane lattice is horizontally aligned and the a-plane lattice oriented perpendicularly. The orientation-dependent growth significantly influences stress relaxation through the generation of misfit dislocations, originating from either basal or prismatic slip. Edge dislocations, induced by misfit dislocations, favor the c-axis, remaining well confined within the in-plane interfacial layer of the m-plane α-Ga2O3, leading to reduced low edge dislocation density in the subsequent thick epitaxial layer. These findings shed light on the epitaxial dynamics of α-Ga2O3 heteroepitaxy, paving the way for the development of high-performance power devices. [ABSTRACT FROM AUTHOR]

In order to compare the effects of different types of quenching circuits on the detection performance of 4H-SiC avalanche photodiodes (APD), single-photon detection experiments were conducted on two types of SiC ultraviolet APD by using passive quenching circuits (PQC) and active quenching circuits (AQC). It was found that during a long dead time in PQC, post pulse phenomena occur frequently, resulting in a higher dark counting rate (DCR) of APD, thereby reducing the signal-to-noise ratio of the device. A study was conducted on the time distribution of pulse probability after APD, and further analysis was conducted on the problems encountered by AQC in single-photon detection under higher device bias. A circuit improvement plan was proposed. The research results indicate that by adjusting the dead time of AQC to 45 ns, the device DCR can be reduced to 1/4 of the original level under the same single-photon detection efficiency. By effectively suppressing post pulse and accelerating APD recovery speed, AQC can enable the device to exhibit superior detection performance. This study provides a certain reference for the application of SiC APD in single-photon detection. [ABSTRACT FROM AUTHOR]

Aims Volatile organic compounds (VOCs) have an important function in plant growth-promoting rhizobacteria (PGPR) development and plant growth. This study aimed to identify VOCs of the PGPR strain, Stutzerimonas stutzeri NRCB010, and investigate their effects on NRCB010 biofilm formation, swarming motility, colonization, and tomato seedling growth. Methods and results Solid-phase microextraction and gas chromatography-mass spectrometry were performed to identify the VOCs produced during NRCB010 fermentation. A total of 28 VOCs were identified. Among them, seven (e.g. γ-valerolactone, 3-octanone, mandelic acid, 2-heptanone, methyl palmitate, S-methyl thioacetate, and 2,3-heptanedione), which smell well, are beneficial for plant, or as food additives, and without serious toxicities were selected to evaluate their effects on NRCB010 and tomato seedling growth. It was found that most of these VOCs positively influenced NRCB010 swarming motility, biofilm formation, and colonization, and the tomato seedling growth. Notably, γ-valerolactone and S-methyl thioacetate exhibited the most positive performances. Conclusion The seven NRCB010 VOCs, essential for PGPR and crop growth, are potential bioactive ingredients within microbial fertilizer formulations. Nevertheless, the long-term sustainability and replicability of the positive effects of these compounds across different soil and crop types, particularly under field conditions, require further investigation. [ABSTRACT FROM AUTHOR]

Power Schottky barrier diodes (SBDs) face an inherent trade-off between forward conduction loss and reverse blocking capability. This limitation becomes more severe for ultra-wide bandgap (UWBG) SBDs due to the large junction field. A high Schottky barrier is usually required to suppress the reverse leakage current at the price of an increased forward voltage drop (VF). This work demonstrates a Ga2O3 junction barrier Schottky (JBS) diode that employs the embedded p-type NiO grids to move the peak electric field away from the Schottky junction, thereby allowing for the use of an ultra-low barrier TiN Schottky contact. This JBS diode concurrently realizes a low VF of 0.91 V (at forward current of 100 A/cm2) and a high breakdown voltage over 1 kV, with the VF being the lowest in all the reported vertical UWBG power diodes. Based on the device characteristics measured up to 200 °C, we further analyze the power loss of this JBS diode across a wide range of operational duty cycles and temperatures, which is found to outperform the TiN/Ga2O3 SBDs or NiO/Ga2O3 PN diodes. These findings underscore the potential of low-barrier UWBG JBS diodes for high-frequency, high-temperature power electronics applications. [ABSTRACT FROM AUTHOR]