Forward Bias Research Articles

26‐3: Room Temperature Bias‐Selectable, Dual‐Band Ultraviolet/Infrared Detectors Based on PTAA/MAPbCl3 Single Crystal film Heterojunction

A single photodetector capable of switching its peak spectral photoresponse between two wavelength bands is highly useful, particularly for the ultraviolet‐infrared bands in applications such as remote sensing, object identification, and chemical sensing. However, it is difficult to realize dual‐frequency ultraviolet/infrared detection with the existing technology. In this study, we leverage the advantages of perovskites materials to demonstrate a bias‐selectable ultraviolet/infrared dual‐band detector that operates at room temperature by using CH3NH3PbCl3 (MAPbCl3) single ctystal film and poly(triaryl amine). By switching between zero and forward bias, this detectors switch peak photosensitive ranges between the ultraviolet and infrared bands with room temperature detectivities of 4.5 × 1012 and 1.65 × 10 9 cm Hz 1/2 W −1, respectively. Unlike conventional bias‐selectable detectors, which utilize a set of back‐to‐back photodiodes, we demonstrate that under zero/forward bias conditions the device's operation mode instead changes between photovoltaic effect and photoconductive effect / the radiant thermal effect, allowing additional functionalities that the conventional structure cannot provide.

Heteroepitaxially grown homojunction gallium oxide PN diodes using ion implantation technologies

Although advancements in n- and p-doping of gallium oxide (Ga2O3) are underway, the realization of functional pn diodes remains elusive. Here, we present the successful fabrication of a Ga2O3 pn diode utilizing ion implantation technology. The Ga2O3 epilayers were grown on c-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD). P-type conductivity Ga2O3 epilayer, confirmed by Hall effect analysis, was achieved by phosphorus (P) ion implantation followed with a rapid thermal annealing (RTA) process. This p-Ga2O3 epilayer reveals a significant reduction in resistivity (<106) compared to undoped Ga2O3, demonstrating the successful inclusion and activation of P within the crystal lattice. X-ray diffraction analysis shows that the Ga2O3 epilayers were grown in high crystal quality. Although the crystallinity of Ga2O3 was slightly degraded after P ion implantation, the structure was recovered to high-quality crystal after RTA treatment. For the device structure, p-type Ga2O3 was formed first, followed n-type Ga2O3 regrowth to create a pn junction diode. The obtained results demonstrate a built-in voltage of 4.8 V, 4.2 V, and 4.308 V from simulation, fabricated pn diodes measured by I–V and C–V, respectively. A high breakdown voltage of 900 V was also obtained for the lateral pn diode grown on sapphire substrate. As concerning temperature stability, I–V curves of Ga2O3 pn diode were measured from 25oC to 150oC in steps of 25 °C. At elevated temperatures, for both forward and reverse biases, consecutive increasing currents were measured. These could be resulted from dominant diffusion and drift currents over recombination current at a given bias. In addition, the reverse current saturated (@V > 3kT/q) and remained very low at 2✕10−8 A, as the diode operated at 150oC. The behavior could be due to Ga2O3 being a wide bandgap material.

Field emission characteristics of AlGaN/GaN nanoscale lateral vacuum diodes

We report the design, fabrication, and measurement of the field emission (FE) characteristics of AlGaN/GaN nanoscale lateral vacuum diodes with triangular cathodes and cathode to anode spacings from 50 to 600 nm. The FE characteristics of the AlGaN/GaN diodes with metallic or AlGaN/GaN anodes show successful rectification with forward bias FE current in the range of microamperes or milliamperes, respectively, when biased within a maximum range varying from 10 to 30 V. In the forward bias mode, the measured current Im vs applied anode to cathode bias Vm are well fitted to Murphy–Good profiles associated with FE at higher biases, and an Ohmic leakage profile below the threshold for FE. Our results are the first successful demonstration of FE of electrons between the two two-dimensional electron gases (2DEGs) present on both sides of a nanogap formed by electron lithography through an AlGaN/GaN heterojunction. A qualitative explanation of the loop-type FE characteristics of both AlGaN/GaN vacuum diodes, with either metallic or AlGaN/GaN anodes, is presented.

A voltage-driven dual-mode MoSe2 photodetector with graphene as van der Waals contact

Two-dimensional (2D) molybdenum selenide (MoSe2) is promising for use in the development of photodetectors for the harvesting of light from the ultraviolet to the near-infrared band, while high responsivity and fast response speed are difficult to simultaneously realize. Herein, we present a dual-mode MoSe2 photodetector with asymmetric electrodes, in which graphene and Cr metal are utilized as ohmic and Schottky contacts, respectively. The photodiode possesses fabulous Schottky characteristics, with a rectification ratio of ∼250 and a low dark current of ∼40 pA at −1 V. Under forward bias voltage of 1 V, the photodetector works in photoconductive mode with a slow response speed (decay time: ∼5 min) but high responsivity (632 mA W−1). However, at reverse bias voltage, the photodetector acts as a photovoltaic-type device due to the Schottky barrier between Cr and MoSe2. Because of the reinforced built-in electric field, the photodetector driven at −5 V shows much faster response speeds (rise time: 1.96 ms; decay time: 755 µs). This study provides a deep understanding of asymmetric structure MoSe2 photodetectors operated in two modes, which promotes a forward step toward 2D material optoelectronics.

Suppression of current-induced membrane discharge of bipolar membranes by regulating ion crossover transport

Bipolar membranes (BPMs) exhibit the unique capability to regulate the operating environment of electrochemical system through the water dissociation-combination processes. However, the industrial utilization of BPMs is limited by instability and serious energy consumption. The current-induced membrane discharge (CIMD) at high-current conditions has a negative influence on the performance of anion-exchange membranes, but the underlying ion transport mechanisms in the BPMs remain unclear. Here, the CIMD-coupled Poisson-Nernst-Planck (PNP) equations are used to explore the ion transport mechanisms in the BPMs for both reverse bias and forward bias at neutral and acid-base conditions. It is demonstrated that the CIMD effect in the reverse-bias mode can be suppressed by enhancing the diffusive transport of salt counter-ions (Na+ and Cl−) into the BPMs, and that in the forward-bias mode with acid-base electrolytes can be suppressed by matching the transport rate of water counter-ions (H3O+ and OH−). Suppressing the CIMD can promote the water dissociation in the reverse-bias mode, as well as overcome the plateau of limiting current density and reduce the interfacial blockage of salt co-ions (Cl−) in the anion-exchange layer in the forward-bias mode with acid-base electrolytes. Our work highlights the importance of regulating ion crossover transport on improving the performance of BPMs.

Emotional anticipation for dynamic emotional faces is not modulated by schizotypal traits: A Representational Momentum study.

Schizotypy, a personality structure that resembles schizophrenia symptoms, is often associated with abnormal facial emotion perception. Based on the prevailing sense of threat in psychotic experiences, and the immediate perceptual history of seeing others' facial expressions, individuals with high schizotypal traits may exhibit a heightened tendency to anticipate anger. To test this, we used insights from Representational Momentum (RM), a perceptual phenomenon in which the endpoint of a dynamic event is systematically displaced forward, into the immediate future. Angry-to-ambiguous and happy-to-ambiguous avatar faces were presented, each followed by a probe with the same (ambiguous) expression as the endpoint, or one slightly changed to express greater happiness/anger. Participants judged if the probe was "equal" to the endpoint and rated how confident they were. The sample was divided into high (N = 46) and low (N = 49) schizotypal traits using the Schizotypal Personality Questionnaire (SPQ). First, a forward bias was found in happy-to-ambiguous faces, suggesting emotional anticipation solely for dynamic faces changing towards a potential threat (anger). This may reflect an adaptative mechanism, as it is safer to anticipate any hostility from a conspecific than the opposite. Second, contrary to our hypothesis, high schizotypal traits did not heighten RM for happy-to-ambiguous faces, nor did they lead to overconfidence in biased judgements. This may suggest a typical pattern of emotional anticipation in non-clinical schizotypy, but caution is needed due to the use of self-report questionnaires, university students, and a modest sample size. Future studies should also investigate if the same holds for clinical manifestations of schizophrenia.

Bias‐Switchable Dual‐Mode Organic Photodiodes Enabled by Manipulation of Interface Layers

AbstractBias‐switchable dual‐mode organic photodiodes (OPDs) that integrate photovoltaic and photomultiplication modes are recently developed and shown prospects in complex light‐intensity applications. Yet, the device physics that focuses on carrier dynamics is still a challenge and needs to be further explored. Herein, dual‐mode OPDs are developed through interface layer manipulation, that is, introducing cathode interface layers (typically, ZnxO:D149) with deep energy levels and abundant bulk defects and an anode interface layer of thermally‐evaporated ZnO (e‐ZnO) with a wide bandgap. Under reverse bias, ZnxO:D149 forms a barrier wall to effectively block external holes and maintain the photovoltaic mode of the OPDs. Under forward bias, the capturing effect of ZnxO:D149 and blocking effect of e‐ZnO help to reduce the dark current; when under illumination, defect traps capture photo‐generated holes, eliminating the barrier traps and promoting unobstructed injection of external carriers to achieve photomultiplication effect. The typical device delivers high specific detectivity (&gt;1012 Jones) and fast response (&lt;40 µs), and exhibits disparate external quantum efficiency in two operating modes, showing promise for simultaneously detecting faint and strong light. This general strategy for preparing dual‐mode OPDs is compatible with CMOS processing technology and meets the miniaturization and integration requirements of next‐generation detection systems.

Photosensitive properties of Schottky type photodiodes prepared by spin coating of isoniazid Schiff base thin film on p-Si

In this study, a layer of isonicotinohydrazide and pyrene-based Schiff base (PyMIs) was formed on the front side of a p-Si semiconductor using the spin coating method, and an Al/PyMIs/p-Si/Al diode was fabricated. The I-V characteristics of the fabricated diode were measured under dark and from 20 to 100 mW/cm2 illumination intensities for both forward and reverse bias. Diode parameters, including saturation current (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${I}_{0}$$\\end{document}), ideality factor (n), and barrier height (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\varphi }_{b}$$\\end{document}) were investigated for all measurements based on thermionic emission theory. The values n changed from 2.51 to 2.05, and the \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\varphi }_{b}$$\\end{document} changed from 0.77 eV to 0.86 eV as light intensity increased from dark to 100 mW/cm2. The series resistance (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}_{s}$$\\end{document}) values of the diode were investigated using the modified Norde’s function and Cheung’s functions. An analysis of the forward \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$log\\left( I \\right) - log\\left( V \\right)$$\\end{document} plot of Al/PyMIs/p-Si (MOmS)-type diode specified the carrier transport domination by ohmic conduction in the lower bias regions, by the space-charge-limited current (SCLC) at medium bias regions and the trap-charge limit current (TCLC) transport mechanism at higher bias regions. The fabricated diode exhibited typical photodiode behavior with reverse current values increasing from 9.13 × 10− 6 A to 1.05 × 10− 4 A, respectively. Furthermore, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$I-V$$\\end{document} characteristics illuminated from 20 to 100 mW/cm2 were also studied, and they indicated that the Al/PyMIs/p-Si diode could operate in a photovoltaic regime.

Investigate the Electrical and Structural Characteristics of the Si-ZnO Diode

Silicon-zinc oxide (Si-ZnO) junction has been prepared using the chemical bath technique. The zinc oxide layer was examined using different techniques, including X-ray spectroscopy and a UV-visible spectrophotometer. The ZnO film images show that the films are homogeneous with an average grain size of 70 nm, while the X-ray spectrum shows that the layers are amorphous with some crystalline phase peaks appearing between 2θ=20° and 35°, which belong to ZnO. Transmittance, absorbance and extinction coefficient were varied over the visible light wavelength range, and the energy gap of the films was about 2.6 eV. In both forward and reverse bias, the junction revealed diode characteristics. The influence of light on the current intensity was evident and reached about 240 mA compared to the current intensity in the dark state. Also, the current intensity of the diode increased at each applied voltage with the increase in the intensity of the light shining on it.

Effect of annealing temperature for structural, electrical, and ammonia sensing properties of pristine ZnO and ZnO/SiO2 nanoparticles

The main objective of this research was to study the electrical and gas-sensing properties of Zinc oxide (ZnO) nanoparticles. The samples were divided into two conditions in the preparation process. In the first condition, ZnO powder was annealed at temperatures of 650, 700, and 750 ๐C for 2 h, while the second condition involved mixing ZnO powder with SiO2 powder and annealing at temperatures of 650, 700 and 750 ๐C for 2 h. The characteristics of the prepared samples were studied by scanning electron microscopy (SEM) and the X-ray diffraction technique (XRD). The SEM images showed the agglomeration of the particles with micron-sized diameters. In addition, the XRD patterns of all samples exhibited the hexagonal structure of ZnO. Assessment of the electrical properties of the samples was carried out by forward bias from 0 – 15 V and reverse bias from 0 V to -15 V. The I – V characteristic curves showed diode-like rectifying behavior.The gas-sensing property of the samples was investigated by using ammonia gas, and ZnO nanoparticles annealed at 750 ºC for 2 h were found to have the highest sensitivity.

Illumination dependent electrical, photosensitivity and photodetectivity properties of Au/SiO2/n-Si structures: optoelectronic situations

Abstract This study aims to examine the electrical, photosensitivity (S), photo-response (R), and photo-detectivity (D*) properties of Au/SiO2/n-type Si structures under different illumination intensities. The illumination-dependent properties of the Au/SiO2/n-type Si structure with SiO2 interlayer were obtained using current–voltage (I-V) characteristics. The ideality factors (n) and barrier heights (Φbo) values of Au/SiO2/n-type Si structures were obtained and compared from forward and reverse bias current–voltage (I-V) measurements at room temperature. Also, barrier heights (Φbo) and series resistance (R S ) values obtained from Norde method were compared with the values obtained from TE theory. It was observed that ideality factor and barrier height values obtained from forward bias region are higher than the values reverse bias. This means that the linearity or rectification feature in the reverse bias region is better than the forward bias region. Furthermore, photodiode values such as photo response (R), photosensitivity (S) and photodetectivity (D*) of Au/SiO2/n type Si structures were also examined depending on the light intensity. Consequently, the experimental results showed that the increase in reverse current with increasing light indicates that the Au/SiO2/n-type Si structures can be used in semiconductor technology as a photodiode, detector or sensor.

Electrical, structural and photovoltaic properties of acceptor dye modified Au/n-Ge heterostructure

n-Ge heterostructure is fabricated using organic dye interlayers such as sulforhodamine-G (SRG) using low-cost spin coating technique and explored its electrical and structural features. The I–V measurements of the Au/SRG/n-Ge heterostructure (HJ) show good rectification behavior. It has been noticed that the barrier height (0.73 eV) of the Au/SRG/n-Ge heterojunction was significantly higher than the Au/n-Ge Schottky diode (SD) (0.63 eV). Cheung's function and the Norde method has been utilized to evaluate the various barrier parameters to understand the non-ideal behavior of the contacts at higher bias region. The low value of the series resistance for HJ (53 Ω) is observed than compared to the SD without organic dye (2974 Ω). Barrier parameters evaluated from the Norde method were compared with those from the Cheung method and found that they confirmed the consistency of Schottky barrier parameters obtained from both techniques. The transport properties of the HJ and SD in the forward bias region are evaluated using the log (I) vs. log (V) plot. At larger forward bias voltages, a change in the drift of current conduction is observed from Ohmic current conduction to traps-assisted SCLC conduction. This may be ascribed to the presence of defects or traps at the n-Ge and SRG interface possibly associated with the organic dye. Also, the photovoltaic properties of the SRG/n-Ge heterostructures were evaluated at 100 mW/cm2 showing significant photoresponse indicates the usage of SRG dyes in photosensitive applications.

Electrical and dielectric behaviors of Al/SiO2-surfactant/n-Si schottky structure in wide range of voltage and frequency

SiO2 surfactant insulator into Al/n-Si metal-semiconductor (MS) structure was fabricated into Al/SiO2-surfactant/n-Si metal–insulator–semiconductor (MIS) structure and its effect on the electrical properties of the final structure was investigated. The SiO2-surfactant layer is coated on the n-Si wafer by the spin coating technique. The I-V data is used to calculate the fundamental electrical parameters of this MIS structure. The density distribution of the surface states (Nss) is computed depending on the energy at forward potential. The current conduction mechanisms (CCMs) in the MIS structure are examined at the reverse and forward biases applied. To get more accurate and reliable results, the profiles of I-V and C/(G/ω)-V are measured at a wide range of bias voltage (0.25V-4V) and frequency (1kHz-1MHz), respectively. The performance of the MIS is significant due to the basic values of electrical parameters (n, I0, Rs, Rsh, Nss, ΦB0, and Rectifying Ration (RR)) and dielectric parameters (ε′, ε″, tan δ, M′, M″, Rs, and σ) compared with the MS structure. The other electrical parameters (ND, WD, Em, ΦΒ) are extracted from the slope and intercept of the reverse bias C−2-V plot as a function of frequency. Furthermore, the profile of voltage-dependent Rs and Nss was determined using different methods from I-V and C/G-V data and examined comparatively with each other. The changes in impedance properties with frequency and voltage of the MIS are discussed in detail.

Investigation of carrier transport and recombination at type-II band aligned p-NiO/AlGaN interface in p-NiO gate AlGaN/GaN HEMTs under forward bias

In this work, fine carrier transport and recombination processes in p-NiO gate AlGaN/GaN high electron mobility transistors were investigated by analyzing their electroluminescence under forward gate bias, with photoluminescence spectrum as a reference. Red luminescence with a peak of 1.9 eV was captured when the gate bias voltage exceeded 4 V, which was verified to originate from the tunneling enhanced interface recombination of injected holes from the gate metal and spilled electrons from the 2DEG channel at the type-II band aligned p-NiO/AlGaN heterostructure interface. Under higher gate bias voltage, holes were further injected into the GaN buffer layer, producing ultraviolet luminescence and yellow luminescence, corresponding respectively to the band edge emission and defect-assisted radiative recombination of GaN. Threshold voltage shift measurements under forward gate bias were conducted to further investigate the carrier transport and recombination processes.

Planarization of p-GaN surfaces on MOCVD grown V-defect engineered GaN-based LEDs

The large polarization barriers between the quantum wells and quantum barriers in long-wavelength GaN-based light-emitting diodes (LEDs) inhibit their performance by requiring excess driving voltages to reach standard operating current densities. Lateral injection of carriers directly into quantum wells is required to circumvent this issue. V-defects are naturally occurring inverted hexagonal defects with semipolar 101¯1-plane sidewalls generated on surface depressions from threading dislocations. LEDs engineered to intentionally generate V-defects below the active region of the LED can achieve lateral carrier injection through the V-defect sidewalls and have already been able to demonstrate world record wall-plug efficiencies for LEDs in the green-red wavelengths. V-defects can be enlarged during kinetically limited growth where the growth rate of the c-plane GaN is faster than that of their sidewalls, leaving them unfilled. We report on the metal organic chemical vapor deposition growth conditions required to fill in V-defects with p-GaN during epitaxial growth of the LED post the active region. Circular transmission length measurements of Pd/Au contacts processed on p-GaN surfaces with various amounts of unfilled V-defects showed no significant difference in their sheet resistance and specific contact resistance. J–V measurements of LEDs grown with varying unfilled V-defect densities showed no significant difference in the forward bias regime. However, in the reverse bias regime, catastrophic breakdown occurred at markedly lower voltages for samples with larger unfilled V-defect densities. This suggests that unfilled V-defects may act as hotspots for device failure, and planarizing LED surfaces may help prevent early degradation of LED devices.

On the Impact of Bimolecular Recombination on Time‐Delayed Collection Field Measurements and How to Minimize Its Effect

The time‐delayed collection field (TDCF) technique is a popular method to quantify the field and temperature dependences of free charge generation in organic solar cells. Because the method relies on the extraction of photogenerated charge carriers, bimolecular recombination not only between the photogenerated carriers but also between the photogenerated and dark‐injected carriers affects its accuracy, particularly at forward bias. In this work, drift–diffusion simulations are employed to quantify the recombination losses in conventional and modified TDCF measurements, where the latter technique intends to reduce the impact of dark injection. It is shown that parameters such as the generation profile, carrier mobilities, and effective density of states affect the recombination losses in both measurements. Importantly, modified TDCF enables to reduce the recombination losses at forward bias, especially beyond the open‐circuit voltage. However, conventional TDCF is preferable for studies at reverse bias due to a better depletion of the active layer prior to the emergence of the photogenerated carriers. Measurements on a ZR1:Y6 blend with fast recombination are in good agreement with the simulation results. This work shows that artifacts in TDCF measurements related to non‐geminate recombination can be accounted for and minimized through an informed choice of the experimental conditions.

Analysis of photodiode and barrier properties of CoPc/n-Ge heterojunction under various illumination wavelengths

The present investigation reports the analysis of barrier parameters of the CoPc/n-Ge heterojunction photodiode under varied illumination wavelengths from 500 nm to 1200 nm in steps of 25 nm. The efficiency of this photodiode was also summarized using responsivity, detectivity and quantum efficiency for different illumination wavelengths. The photocurrent seems to be maximum for 850 nm and 1175 nm and shows higher responsivity of 1.72 A/W and 2.38 A/W at 775 nm and 1125 nm wavelength respectively. The quantum efficiency of the photodiode was found to be 275 % at illumination wavelength of 775 nm and 263 % at 1125 nm. For the selective illumination wavelengths (775 nm, 850 nm, 1125 nm and 1175 nm), the electrical properties of the CoPc/n-Ge photodiode were studied. Noticeable variation in the barrier parameters of the photodiode is observed with illumination than compared to dark. Significantly, the series resistance was found to be decreased and shunt resistance is increased with illumination wavelength than compared to dark. Current conduction mechanisms were also investigated in both the forward and reverse bias of the photodiode. The forward current transport processes show that at moderately high bias the current conduction might be associated with TCLC. It is also evidenced from the reverse conduction mechanism that at low reverse voltages PFE is found to be dominant whereas SE is dominant at high reverse voltages. The reduced interface state densities at the CoPc/n-Ge interface were observed under illumination than compared to dark.

Interface‐Engineering Induced Swift and Controllable Solar‐Blind Photoresponse in Ga2O3/SiC Heterojunction Based on Unconventional Rectification Characteristics

AbstractGa2O3 photodetectors with demonstrated high sensitivity provide a potential subversive scheme for solar‐blind photodetection. However, the planar structure and the relatively slow response speed of the device have restricted the integration and application of Ga2O3 photodetectors. Herein, a narrow SiO2 barrier layer is introduced on the commercial SiC substrate, and a vertical photodetector is realized based on β‐Ga2O3/SiO2/SiC heterostructure with controllable tunneling effect by tailoring the band structure at the interface. The developed device exhibits unconventional rectification characteristics and photoresponse performance in different biasing modes owing to the controllable tunneling effect at the interface. In particular, the photodetector achieves a high responsivity (186.8 A W−1) under solar‐blind illumination at reverse bias, while exhibiting obvious advantages in dark current (3 pA), photo‐to‐dark current ratio (8.8 × 106), linear dynamic range (138.8 dB), and specific detectivity (1.4 × 1015 Jones) at forward bias. The photodetector also demonstrates excellent photoresponse stability after 6 months in air without encapsulation. In addition, an alternating biasing strategy, inspired by its bidirectional operability, is proposed to suppress the persistent photoconductivity effect and increase the decay speed by 1.23 × 105 times. This work provides a referable strategy for the further development of high‐performance Ga2O3‐based photoelectronics.

Structural, chemical states, electrical properties and forward transport phenomena of Ti/MnO2/p-InP heterostructure with a transition metal oxide MnO2 interlayer

The study examines the surface topology, optical, structural and electrical characteristics of e-beam evaporated manganese dioxide (MnO2) films on p-InP using AFM, FESEM, UV–Vis, XRD, XPS and I–V procedures. The surface roughness of the MnO2 was smooth from AFM and FESEM analysis. The optical bandgap of MnO2 film was extracted from Tauc's plot. The outcomes endorse that the MnO2 layer deposited on InP. Then, the Ti/MnO2/p-InP heterostructure (HS) was created with an MnO2 interlayer to check the consequence of MnO2 on the electrical features of the Ti/p-InP Schottky diode (SD). The I–V results demonstrated that the higher Φb is acquired for the HS (0.90 eV) than the SD (0.84 eV), implying the MnO2 layer alters the Фb. Also, the Фb, ‘n’ and RS of the SD and HS can be determined by utilizing Cheung's and Norde's functions. The estimated Фb was almost similar, indicating the methodologies applied here are sturdy and effective. The determined NSS of the HS is lesser than the SD, implying that the MnO2 interlayer has a significant role in the decrease in NSS. The forward bias log (I)-log(V) plot of the SD and HS indicates that the ohmic behavior and space charge limited the conduction process at lower-bias and higher-bias segments, respectively. The study outcomes suggested that the transition metal oxide MnO2 layer would be favourable for creating MIS devices.

2D Memory Selectors with Giant Nonlinearity Enabled by Van der Waals Heterostructures.

The integration of one-selector-one-resistor crossbar arrays requires the selectors featured with high nonlinearity and bipolarity to prevent leakage currents and any crosstalk among distinct cells. However, a selector with sufficient nonlinearity especially in the frame of device miniaturization remains scarce, restricting the advance of high-density storage devices. Herein, a high-performance memory selector is reported by constructing a graphene/hBN/WSe2 heterostructure. Within the temperature range of 300-80K, the nonlinearity of this selector varies from ≈103-≈104 under forward bias, and increases from ≈300-≈105 under reverse bias, the highest reported nonlinearity among 2D selectors. This improvement is ascribed to direct tunneling at low bias and Fowler-Nordheim tunneling at high bias. The tunneling current versus voltage curves exhibit excellent bipolarity behavior because of the comparable hole and electron tunneling barriers, and the charge transport polarity can be effectively tuned from N-type or P-type to bipolar by simply changing source-drain bias. In addition, the conceptual memory selector exhibits no sign of deterioration after 70000 switching cycles, paving the way for assembling 2D selectors into modern memory devices.