The growing demand for scalable solar‐blind image sensors with remarkable photosensitive properties has stimulated the research on more advanced solar‐blind photodetector (SBPD) arrays. In this work, ...the authors demonstrate ultrahigh‐performance metal‐semiconductor‐metal (MSM) SBPDs based on amorphous (a‐) Ga2O3 via a post‐annealing process. The post‐annealed MSM a‐Ga2O3 SBPDs exhibit superhigh sensitivity of 733 A/W and high response speed of 18 ms, giving a high gain‐bandwidth product over 104 at 5 V. The SBPDs also show ultrahigh photo‐to‐dark current ratio of 3.9 × 107. Additionally, the PDs demonstrate super‐high specific detectivity of 3.9 × 1016 Jones owing to the extremely low noise down to 3.5 fW Hz−1/2, suggesting high signal‐to‐noise ratio. Underlying mechanism for such superior photoelectric properties is revealed by Kelvin probe force microscopy and first principles calculation. Furthermore, for the first time, a large‐scale, high‐uniformity 32 × 32 image sensor array based on the post‐annealed a‐Ga2O3 SBPDs is fabricated. Clear image of target object with high contrast can be obtained thanks to the high sensitivity and uniformity of the array. These results demonstrate the feasibility and practicality of the Ga2O3 PDs for applications in solar‐blind imaging, environmental monitoring, artificial intelligence and machine vision.
Ultraviolet imaging technology is widely used in meteorology, medical science, and military science. For the first time, a high‐uniformity 32 × 32 solar‐blind image sensor array with outstanding imaging capability is demonstrated based on high‐performance Ga2O3 photodetectors. Schottky barrier lowering effect is experimentally revealed to attribute to the internal gain mechanism.
Abstract
III–V semiconductor nanowires are indispensable building blocks for nanoscale electronic and optoelectronic devices. However, solely relying on their intrinsic physical and material ...properties sometimes limits device functionalities to meet the increasing demands in versatile and complex electronic world. By leveraging the distinctive nature of the one-dimensional geometry and large surface-to-volume ratio of the nanowires, new properties can be attained through monolithic integration of conventional nanowires with other easy-synthesized functional materials. Herein, we combine high-crystal-quality III-nitride nanowires with amorphous molybdenum sulfides (a-MoS
x
) to construct III-nitride/a-MoS
x
core-shell nanostructures. Upon light illumination, such nanostructures exhibit striking spectrally distinctive photodetection characteristic in photoelectrochemical environment, demonstrating a negative photoresponsivity of −100.42 mA W
−1
under 254 nm illumination, and a positive photoresponsivity of 29.5 mA W
−1
under 365 nm illumination. Density functional theory calculations reveal that the successful surface modification of the nanowires via a-MoS
x
decoration accelerates the reaction process at the electrolyte/nanowire interface, leading to the generation of opposite photocurrent signals under different photon illumination. Most importantly, such polarity-switchable photoconductivity can be further tuned for multiple wavelength bands photodetection by simply adjusting the surrounding environment and/or tailoring the nanowire composition, showing great promise to build light-wavelength controllable sensing devices in the future.
The set voltage distribution of Pt/HfO 2 /Pt resistive switching memory is shown to fit well a Weibull model with Weibull slope and scale factor increasing logarithmically with the resistance ...measured at the set point. Gaining inspiration from the percolation model of oxide breakdown, a physics-based model for the V set statistics is proposed. The results of the model are completely consistent with the experimental results and demonstrate the need of a strong reset to get large Weibull slope that provides some relief to the strong requirements imposed by the set speed-read disturb dilemma.
The sneak path problem is one of the major hindrances to the application of high-density crossbar resistive random access memory; however, complementary resistive switching (CRS) is an effective ...solution to this problem. The co-existence of resistive switching (RS) and CRS is possible within the same device. Therefore, a precise control is highly required for the successful utilization of different modes. In this study, we have demonstrated an effective way to control both switching modes in a simple HfO2-based crossbar device. The interchange between RS and CRS modes is possible, based on the intrinsic anionic rearrangement by controlling the extrinsic stimulation, either in the form of voltage or in the form of current. In particular, a highly nonlinear CRS mode is reported, in which the nonlinearity is almost 100 times greater than in the RS mode, which is achieved at a high temperature of 150 °C. The procedure reported in this study may be useful for the other resistive memory systems.
The intrinsic scaling-down ability, simple metal-insulator-metal (MIM) sandwich structure, excellent performances, and complementary metal-oxide-semiconductor (CMOS) technology-compatible fabrication ...processes make resistive random access memory (RRAM) one of the most promising candidates for the next-generation memory. The RRAM device also exhibits rich electrical, thermal, magnetic, and optical effects, in close correlation with the abundant resistive switching (RS) materials, metal-oxide interface, and multiple RS mechanisms including the formation/rupture of nanoscale to atomic-sized conductive filament (CF) incorporated in RS layer. Conductance quantization effect has been observed in the atomic-sized CF in RRAM, which provides a good opportunity to deeply investigate the RS mechanism in mesoscopic dimension. In this review paper, the operating principles of RRAM are introduced first, followed by the summarization of the basic conductance quantization phenomenon in RRAM and the related RS mechanisms, device structures, and material system. Then, we discuss the theory and modeling of quantum transport in RRAM. Finally, we present the opportunities and challenges in quantized RRAM devices and our views on the future prospects.
For the first time, a core drain current model based on surface potential without any implicit functions is developed for beta-phase gallium oxide (β-Ga2O3) power metal-oxide-semiconductor ...field-effect transistors (MOSFETs). The surface potential solution is analytically deduced by solving the Poisson equation with appropriate simplification assumptions in accumulation, partial-depletion, and full-depletion modes. Then, the drain current expression is analytically derived from the Pao–Sah integral as a function of the mobile charge density obtained from the surface potential at the source and drain terminals. In addition, nonlinear resistors in the source/drain access region are considered. It continuously predicts the characteristics of β-Ga2O3 power MOSFETs in all operation modes, including accumulation mode, partial-depletion mode, and full-depletion mode. Furthermore, the validity of the model is verified by comparing the results of the model with the numerical simulations carried out with the technology computer-aided design (TCAD) tool ATLAS Device Simulator from Silvaco. Good agreement between the proposed model and TCAD simulations is shown for β-Ga2O3 power MOSFETs with different intrinsic channel lengths, channel doping concentrations, and channel thicknesses. Ultimately, the Gummel symmetry test and the harmonic balance simulation test are performed to validate the model’s robustness and convergence.
Highlights
Fully inkjet-printed transparent high-performance thin-film transistors (TFTs) with ultrathin indium tin oxide (ITO) as semiconducting channels were achieved.
The energy band alignment at ...ITO/Al
2
O
3
channel/dielectric interface was investigated by in-depth spectroscopy analysis.
Fully printed n-type metal–oxide–semiconductor inverters based on ITO TFTs exhibited extremely high gain of 181 at a low-supply voltage of 3 V, promising for applications in advanced electronic devices and circuits.
Metal oxide thin-films transistors (TFTs) produced from solution-based printing techniques can lead to large-area electronics with low cost. However, the performance of current printed devices is inferior to those from vacuum-based methods due to poor film uniformity induced by the “coffee-ring” effect. Here, we report a novel approach to print high-performance indium tin oxide (ITO)-based TFTs and logic inverters by taking advantage of such notorious effect. ITO has high electrical conductivity and is generally used as an electrode material. However, by reducing the film thickness down to nanometers scale, the carrier concentration of ITO can be effectively reduced to enable new applications as active channels in transistors. The ultrathin (~10-nm-thick) ITO film in the center of the coffee-ring worked as semiconducting channels, while the thick ITO ridges (>18-nm-thick) served as the contact electrodes. The fully inkjet-printed ITO TFTs exhibited a high saturation mobility of 34.9 cm
2
V
−1
s
−1
and a low subthreshold swing of 105 mV dec
−1
. In addition, the devices exhibited excellent electrical stability under positive bias illumination stress (PBIS, Δ
V
th
= 0.31 V) and negative bias illuminaiton stress (NBIS, Δ
V
th
= −0.29 V) after 10,000 s voltage bias tests. More remarkably, fully printed n-type metal–oxide–semiconductor (NMOS) inverter based on ITO TFTs exhibited an extremely high gain of 181 at a low-supply voltage of 3 V, promising for advanced electronics applications.
PDF
