A high-performance AlGaN/GaN-based ultraviolet photodetector with a field-enhanced mechanism for photocurrent collection is designed and fabricated in this work. In addition to the inherent polarization field, two additional sets of collection fields are formed from a 2DEG layer to a ITO thin film and from the 2DEG layer to a cathode electrode sinker. The effectiveness in the collection of photogenerated carriers is remarkably enhanced, which leads to a photocurrent of 6.6 mA/mm under the illumination of 365 nm-centered ultraviolet light at an intensity of 1.8 mW/cm2. With an in-built shallow isolation trench, the dark current is suppressed below 40 pA/mm under a device bias of 5.0 V. A photo-to-dark current ratio as high as 1.7 × 108, a record high photo-responsivity over 4.3 × 106 A/W, and a high gain of 1.46 × 107 under 365-nm light are demonstrated by the fabricated prototype, showing great competitiveness in state-of-the-art AlGaN/GaN-based ultraviolet photodetectors.
This study presents an AlGaN/GaN ultraviolet (UV) photodetector proven to be highly effective when working under an ultra-low bias voltage. The proposed photodetector is based on an innovative configuration consisting of repetitive AlGaN/GaN fin-shaped capacitor units, which make use of the two-dimensional electron gas (2DEG) layer as the positive field plates and the sidewall tungsten Schottky metal as the ground plates to surround the bulk of photocarrier generation space. Furthermore, a unique partial sidewall oxide structure is fabricated to partition the 2DEG field plates from the ground plates and to enable proper depletion field formation. With the special structure design, the symmetrical three-dimensional depletion fields are formed within each fin-shaped capacitor unit to spatially pinch off the entire bulk region at an ultra-low bias voltage. Effective photocarrier collection can then be achieved by such an extensive field coverage. When biased at 100 mV, intriguing performances in response to 365 nm UV were demonstrated by the fabricated prototype, such as a photocurrent-to-dark-current-ratio of 7.0 × 104, a peak responsivity of 1.1 × 103 A/W, as well as a large detectivity of 1.1 × 1016 Jones. Good transient performance was also observed under 365 nm UV pulses of 0.7 mW/cm2 in intensity with an operating frequency of up to 1 kHz. This work embodies an ultra-low voltage UV photodetector on the AlGaN/GaN epitaxy heterojunction platform with concise and complementary metal-oxide-semiconductor (CMOS)-compatible fabrication procedures, opening up an appealing potential in ultra-low-power optoelectronic integrated circuits for future Internet of Things and edge computing applications.
To achieve higher energy density in safer energy storage systems, a transition to ceramic all‐solid‐state batteries is widely expected. Their performance and cycle‐life is largely controlled by processes at buried interfaces. While experimental operando probing of interfacial processes is under development, first‐principle computational methods are challenged by the complexity of the multiphase models and long simulation periods required to capture slow degradation processes. Thus, simpler empirical reactive forcefields have the potential to substantially accelerate the design and optimization of all‐solid‐state batteries, provided that parameters are available for a wide range of relevant atom types. The energy‐scaled bond valence‐based softBV forcefield has successfully enabled the design of new solid electrolytes or insertion‐type electrode materials and analyses of ion transport processes therein. As a two‐body forcefield, it enables fast simulations for complex structures over long periods, but inevitably shares the tendency of two‐body forcefields to maximize coordination numbers if free volume facilitates a reorganization of the atoms, which makes them less suitable for studying interfacial processes. Herein, this vulnerability of two‐body forcefields is overcome in a computationally efficient way by introducing an embedded‐atom‐method‐inspired bond‐valence‐sum‐based new class of transferable forcefields and its effective use for modeling of surfaces and interfaces is demonstrated.
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