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In this paper, we explored the resistivity behavior of Sb7Se3 thin films on flexible mica. The films maintained their resistance characteristics through various thicknesses and bending cycles. With increasing bends, resistivity and phase transition temperature of both amorphous and crystalline states rose, while the resistance drift coefficient gradually increased. Raman and near infrared experiments confirmed the internal structural changes and bandgap enhancement after bending. Transmission electron microscopy showed enhanced crystallization and uniform element distribution after annealing. Atomic force microscopy observed cracks, explaining the property changes. Additionally, we developed a flexible Sb7Se3 thin-film resistive device with swift reversibility (∼10 ns) regardless of bending, opening new avenues for flexible information storage. [ABSTRACT FROM AUTHOR]

Normally off AlGaN/GaN high electron mobility transistors (HEMTs) with p-type gates are attracting increasing attention due to their high safety and low power loss in the field of power switching. In this work, to solve the Mg difficult activating problem of the conventional p-GaN gate AlGaN/GaN HEMTs, we propose an advanced design for the normally off AlGaN/GaN HEMT with a p-type hexagonal boron nitride (h-BN) gate cap layer to effectively manipulate the channel transport of the device. The simulation results demonstrate that the p-hBN gate cap HEMTs yield superior performance over conventional p-GaN gate HEMTs in terms of output current and breakdown voltage, which can be attributed to the deeper potential well formation at the AlGaN/GaN interface and more accumulation of holes located at the p-hBN/AlGaN interface. Moreover, we investigate the effect of bandgap variation on device performance, taking into account that the exact bandgap of h-BN remains under debate. Herein, valuable insights into h-BN cap-gate E-mode AlGaN/GaN HEMT devices are provided, which could serve as a useful reference for the future development of robust III-nitride material power electronic devices. [ABSTRACT FROM AUTHOR]

Thermal droop, i.e., the loss of emission efficiency over a certain temperature range, is an important performance bottleneck for the successful commercial application of deep-ultraviolet light emitting diodes. In this study, we examined the mechanism of two thermal droop processes of 255 nm AlGaN quantum well light emitting diodes under temperature stresses in order to obtain steady optical output in a broad temperature range. We discovered that the increase in leakage current in the low forward bias region is accompanied by a decrease in apparent carrier concentration of quantum wells near the p side during the thermal droop process at high temperature (>300 K), indicating that the activation of thermal defects enhances the trap assisted tunneling effect and causes the optical power to decrease more significantly at low current. Compared with normal temperature, the low emission power at low temperatures is attributed to the minority trap H1, which has an activation energy of 0.527 eV at 190 K, according to deep level transient spectrum analysis. At low temperatures above 175 K, the optical power increases as the temperature rises due to enhanced hole injection. By analyzing the droop characteristics, we concluded that the activation of thermal defects is the most probable cause of high temperature thermal droop in 255 nm AlGaN quantum well light emitting diodes, whereas hole trap H1, which is linked to gallium vacancy complexes related defects, is most likely the source of low temperature thermal droop. [ABSTRACT FROM AUTHOR]

The metal-semiconductor direct current triboelectric nanogenerator (MSDC-TENG) has attracted increasing attention due to its power density, which is 102−103 times higher than traditional generators. A P-type GaN based MSDC-TENG with a tin electrode is reported in this paper. By adjusting the Mg2+ doping concentration of the P-GaN, it can achieve an open circuit voltage (Voc) of 14.2 V and a short circuit current (Isc) density of ∼25.5 A/m2. This Isc is about 50 times higher than the performance of the Cu/GaN Triboelectric Nanogenerator, and the power density increases by more than 120 times. Under the experimental loading conditions, we also obtained the maximum load current density and the maximum load power of 12.8 and 102.4 W/m2, respectively. This power density is sufficient to drive small electronic circuits. Our results also provide useful insights into the carrier concentration-Isc relation in the Cu/GaN triboelectric nanogenerator. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the degradation of 280 nm ultraviolet light emitting diodes (UV-LEDs) using both optical and electrical characterization methods. By capacitance–voltage methods, we were able to reveal that carriers in the quantum wells closer to the sapphire substrate would redistribute with aging time and stress currents. We compared these distributions with simulations and found that both the polarization charges at the AlGaN/AlGaN heterostructure interface and the quantum well doping were significantly affected by the stress. These results indicated that the migration and diffusion of donor impurities/dislocations under the current flow could lead to the deterioration of the quantum well crystal quality and contribute to the attenuation of optical power. Our study suggests a novel mechanism for degradation of UV-LEDs, and the developed techniques provide a new approach for future reliability analysis. [ABSTRACT FROM AUTHOR]

Spin-coated films are usually polycrystalline or amorphous, while some special materials such as lead iodide (PbI2) and inorganic perovskite could be deposited onto a variety of single-crystal substrates by spin coating obtaining highly oriented films. Herein, we report an effective method for depositing highly textured PbI2 and CsPbI2Br films—via spin coating. An unexpected high-quality PbI2 film with uniform out-plane orientation of the {001} plane was deposited on the gallium nitride substrate, which was benefited from heterogeneous nucleation measured by high-resolution x-ray diffraction (XRD) and Raman mapping. Furthermore, the α-phase CsPbI2Br highly oriented film was deposited on single-crystal (100) silicon with only the (200) plane for the first time. Compressive stress was found both in PbI2 film and in CsPbI2Br film via XRD, Raman spectra, and photoluminescence spectroscopy. Density functional theory calculations were performed to confirm that CsPbI2Br had a tetragonal structure rather than an orthogonal structure. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of Fe1-xGd(Tb)x films prepared by sputtering have been investigated using x-ray diffraction, vibrating sample magnetometer, and ferromagnetic resonance. Magnetic measurements show that the saturation magnetization decreases as the increase of Gd(Tb) content, which agrees with that Gd(Tb) atomic moments align antiparallel with Fe moments. Theoretical fittings of the angular dependence of ferromagnetic resonance field yield the second- and forth-order perpendicular anisotropy constants K⊥1 and K⊥2, which show a spin reorientation with increasing Gd(Tb) doping. The intrinsic contribution of ferromagnetic resonance linewidth as a result of Gilbert damping is separated from the extrinsic contribution because of the inhomogeneity of the films. It is found that the additions of Gd additives do not significantly improve the damping constant, whereas the Tb dopants increase the damping constant from 0.04 without Tb to 0.11 with 19% Tb, thus a remarkable enhancement of 175%. [ABSTRACT FROM AUTHOR]

The metal-semiconductor direct current triboelectric nanogenerator (MSDC-TENG) has attracted increasing attention due to its power density, which is 102−103 times higher than traditional generators. A P-type GaN based MSDC-TENG with a tin electrode is reported in this paper. By adjusting the Mg2+ doping concentration of the P-GaN, it can achieve an open circuit voltage (Voc) of 14.2 V and a short circuit current (Isc) density of ∼25.5 A/m2. This Isc is about 50 times higher than the performance of the Cu/GaN Triboelectric Nanogenerator, and the power density increases by more than 120 times. Under the experimental loading conditions, we also obtained the maximum load current density and the maximum load power of 12.8 and 102.4 W/m2, respectively. This power density is sufficient to drive small electronic circuits. Our results also provide useful insights into the carrier concentration-Isc relation in the Cu/GaN triboelectric nanogenerator. [ABSTRACT FROM AUTHOR]

In this paper, we explored the resistivity behavior of Sb7Se3 thin films on flexible mica. The films maintained their resistance characteristics through various thicknesses and bending cycles. With increasing bends, resistivity and phase transition temperature of both amorphous and crystalline states rose, while the resistance drift coefficient gradually increased. Raman and near infrared experiments confirmed the internal structural changes and bandgap enhancement after bending. Transmission electron microscopy showed enhanced crystallization and uniform element distribution after annealing. Atomic force microscopy observed cracks, explaining the property changes. Additionally, we developed a flexible Sb7Se3 thin-film resistive device with swift reversibility (∼10 ns) regardless of bending, opening new avenues for flexible information storage., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)