High-Sensitivity Infrared Photoelectric Detection Based on WS2 /Si Structure Tuned by Ferroelectrics.

As one of the typical transition-metal dichalcogenides with distinct optical and electrical properties, WS2 exhibits tremendous potential for optoelectronic devices. However, its inherent band gap range limits the application in the infrared region. To overcome this draw-back and improve the sensitivity, P(VDF-CTFE) is used as a ferroelectric gate to control the states of WS2 /Si junctions and achieve an enhanced infrared photodetection. The polarization electric field not only broadens the range of absorption wavelength (405-1550 nm) but also greatly promotes the sensitivity of lateral photovoltaic effect (LPE) (from 198.6 to 503.2 mV mm-1 ). This phenomenon is attributed to the reduction of WS2 band gap and the change of potential barrier at the interface of the junction. Meanwhile, the response speed is improved significantly due to the increase of carrier initial kinetic energy. This new scheme for ferroelectric tuned LPE opens up a way to realize high-sensitivity, ultrafast, and stable infrared photodetection.

Localized Surface Plasmon Induced Position-Sensitive Photodetection in Silicon-Nanowire-Modified Ag/Si.

Surface plasmon-based approaches are widely applied to improve the efficiency of photoelectric devices such as photosensors and photocells. In order to promote the light absorption and electron-hole pair generation in devices, metallodielectric nanostructures are used to boost the growth of surface plasmons. Here, silicon nanowires (SiNWs) are used to modify a metal-semiconductor structure; thus, Ag/SiNWs/Si is manufactured. In this system, a large increased lateral photovoltaic effect (LPE) is detected with a maximum positional sensitivity of 65.35 mV mm-1 , which is ≈53-fold and 1000-fold compared to the conventional Ag/Si (1.24 mV mm-1 ) and SiNWs/Si (0.06 mV mm-1 ), respectively. It is demonstrated that localized surface plasmons (LSPs) contribute a lot to the increment of LPE. Furthermore, through the surface-enhanced Raman scattering spectra of rhodamine-6G and finite-difference time-domain simulation, it is illustrated that silver-coated SiNWs support strong LSPs. The results propose an enhancement mechanism based on LSPs to facilitate the photoelectric conversion in LPE and offer an effective way to improve the sensitivity of photodetectors.

Ultrafast Multifunctional Photodetector Based on the NiAl2O4/4H-SiC Heterojunction.

Solar-blind photodetectors based on wide bandgap semiconductors have recently attracted a lot of interest. Nickel-containing spinel phase oxides, such as NiAl2O4, are stable p-type semiconductors. This paper describes a multifunctional solar-blind photodetector based on a NiAl2O4/4H-SiC heterojunction that utilizes photovoltaic effects. The position sensitivity reaches a value of 1589.7 mV/mm under 405 nm laser illumination, while the relaxation times of vertical photovoltaic (VPV) effect and lateral photovoltaic (LPV) effect under 266 nm laser illumination are only 0.32 and 0.42 µs, respectively. This junction was used to create a space optical communication system with sunlight having little effect on its optoelectronic properties. The ultrafast photovoltaic relaxation time makes NiAl2O4/4H-SiC a promising candidate for self-powered high-performance solar-blind detectors.

Self-Powered Bi2Se3/Si Position-Sensitive Detector and Its Performance Enhancement by Introducing a Si Nanopyramid Structure.

Bi2Se3, as a novel 3D topological insulator (TI), is expected to be a strong candidate for next-generation optoelectronic devices due to its intriguing optical and electrical properties. In this study, a series of Bi2Se3 films with different thicknesses of 5-40 nm were successfully prepared on planar-Si substrates and developed as self-powered light position-sensitive detectors (PSDs) by introducing lateral photovoltaic effect (LPE). It is demonstrated that the Bi2Se3/planar-Si heterojunction shows a broad-band response range of 450-1064 nm, and the LPE response is strongly dependent on the Bi2Se3 layer thickness, which can be mainly attributed to the thickness-modulated longitudinal carrier separation and transport. The 15 nm thick PSD shows the best performance with a position sensitivity of up to 89.7 mV/mm, a nonlinearity of lower than 7%, and response time as fast as 62.6/49.4 µs. Moreover, to further enhance the LPE response, a novel Bi2Se3/pyramid-Si heterojunction is built by constructing a nanopyramid structure for the Si substrate. Owing to the improvement of the light absorption capability in the heterojunction, the position sensitivity is largely boosted up to 178.9 mV/mm, which gets an increment of 199% as compared with that of the Bi2Se3/planar-Si heterojunction device. At the same time, the nonlinearity is still kept within 10% as well due to the excellent conduction property of the Bi2Se3 film. In addition, an ultrafast response speed of 173/97.4 µs is also achieved in the newly proposed PSD with excellent stability and reproducibility. This result not only demonstrates the great potential of TIs in PSD but also provides a promising approach for tuning its performance.

High-Performance Self-Powered Photodetector Based on the Lateral Photovoltaic Effect of All-Inorganic Perovskite CsPbBr3 Heterojunctions.

CsPbBr3, an inorganic halide perovskite, has attracted great interest in recent years due to its excellent photoelectric properties. In this paper, we report a high-performance position-sensitive detector and laser communication sensor based on a CsPbBr3/4H-SiC heterojunction that effectively exploits the lateral photovoltaic (LPV) effect. The X-ray diffraction, X-ray photoelectron spectra, and photoluminescence data indicate that a high-quality CsPbBr3 film has been successfully obtained using pulsed laser deposition. The thickness of the CsPbBr3 film is shown to play a key role in the open-circuit voltage and linear LPV. A large position sensitivity (up to 827 mV/mm) of the LPV with a fast relaxation time is observed. Moreover, the shortest relaxation time of only 0.34 µs for 532 nm laser irradiation among counterparts is achieved in the detector under consideration. Furthermore, the position sensitivity and relaxation time of the LPV in the CsPbBr3/4H-SiC heterojunction show a weak dependence on the laser wavelength from 266 to 532 nm. The robust characteristics of fast relaxation time and high position sensitivity of the LPV make the CsPbBr3 junction a promising candidate for both laser communication sensors and self-powered high-performance position-sensitive detectors.

Enhanced Lateral Photovoltaic Effects in n-Si/SiO2/PEDOT:PSS Structures.

Organic/silicon hybrid structures have been extensively studied for the application of solar cells due to their high photoelectric conversion efficiency and simple fabrication process. However, studies of lateral photovoltaic effects (LPEs) in the devices are still scarce. Herein, the Si/SiO2/PEDOT:PSS devices were prepared by spin-coating, and showing the lateral photovoltage (LPV) sensitivity of 14.0 mV/mm at room temperature, which is higher than the control samples of Si/SiO2 (0.1 mV/mm) and Si/PEDOT:PSS (9.0 mV/mm) structures. With the decrease in temperature, the lateral photovoltage increases initially, and reaches a peak at around 210 K, then drops accordingly. The enhancement of LPE can be mainly ascribed to the formation of the p-n junction and the native oxide layer at the organic/inorganic interface.

Light-Harvesting Self-Powered Monolithic-Structure Temperature Sensing Based on 3C-SiC/Si Heterostructure.

Utilizing harvesting energy to power sensors has been becoming more critical in the current age of the Internet of Things. In this paper, we propose a novel technology using a monolithic 3C-SiC/Si heterostructure to harvest photon energy to power itself and simultaneously sense the surrounding temperature. The 3C-SiC/Si heterostructure converts photon energy into electrical energy, which is manifested as a lateral photovoltage across the top material layer of the heterostructure. Simultaneously, the lateral photovoltage varies with the surrounding temperature, and this photovoltage variation with temperature is used to monitor the temperature. We characterized the thermoresistive properties of the 3C-SiC/Si heterostructure, evaluated its energy conversion, and investigated its performance as a light-harvesting self-powered temperature sensor. The resistance of the heterostructure gradually drops with increasing temperature with a temperature coefficient of resistance (TCR) ranging from more than -3500 to approximately -8200 ppm/K. The generated lateral photovoltage is as high as 58.8 mV under 12 700 lx light illumination at 25 °C. The sensitivity of the sensor in the self-power mode is as high as 360 µV·K-1 and 330 µV·K-1 under illumination of 12 700 lx and 7400 lx lights, respectively. The sensor harvests photon energy to power itself and measure temperatures as high as 300 °C, which is impressive for semiconductor-based sensor. The proposed technology opens new avenues for energy harvesting self-powered temperature sensors.

Generation of a Charge Carrier Gradient in a 3C-SiC/Si Heterojunction with Asymmetric Configuration.

It is critical to investigate the charge carrier gradient generation in semiconductor junctions with an asymmetric configuration, which can open a new platform for developing lateral photovoltaic and self-powered devices. This paper reports the generation of a charge carrier gradient in a 3C-SiC/Si heterojunction with an asymmetric electrode configuration. 3C-SiC/Si heterojunction devices with different electrode widths were illuminated by laser beams (wavelengths of 405, 521, and 637 nm) and a halogen bulb. The charge carrier distribution along the heterojunction was investigated by measuring the lateral photovoltage generated when the laser spot scans across the 3C-SiC surface between the two electrodes. The highest lateral photovoltage generated is 130.58 mV, measured in the device with an electrode width ratio of 5 and under 637 nm wavelength and 1000 µW illumination. Interestingly, the lateral photovoltage was generated even under uniform illumination at zero bias, which is unusual for the lateral photovoltage, as it can only be generated when unevenly distributed photogenerated charge carriers exist. In addition, the working mechanism and uncovered behavior of the lateral photovoltaic effect are explained based on the generation and separation of electron-hole pairs under light illumination and charge carrier diffusion theory. The finding further elaborates the underlying physics of the lateral photovoltaic effect in nano-heterojunctions and explores its potential in developing optoelectronic sensors.

Lattice-Mismatched PbTe/ZnTe Heterostructure with High-Speed Midinfrared Photoresponses.

In this work, a novel heterostructure consisting of different lattice structures with zincblende ZnTe and rock-salt PbTe is proposed. The PbTe/ZnTe heterostructures are grown by molecular beam epitaxy. Type-I band alignment at the PbTe/ZnTe heterointerface is revealed by X-ray photoelectron spectroscopy. The interface of the heterostructure exhibits exotic electrical properties. The novel heterostructure is then implemented to develop high-performance mid-infrared photodetectors which demonstrate pronounced responsivity, swift response speed, and high detectivity. The new photodetectors utilize the lateral photovoltaic effect which facilitates the understanding of the novel PbTe/ZnTe heterostructures.

3C-SiC/Si Heterostructure: An Excellent Platform for Position-Sensitive Detectors Based on Photovoltaic Effect.

Single-crystalline silicon carbide (3C-SiC) on the Si substrate has drawn significant attention in recent years due to its low wafer cost and excellent mechanical, chemical, and optoelectronic properties. However, the applications of the structure have primarily been focused on piezoresistive and pressure sensors, bio-microelectromechanical system, and photonics. Herein, we report another promising application of the heterostructure as a laser spot position-sensitive detector (PSD) based on the lateral photovoltaic effect (LPE) under nonuniform optical illuminations at zero-bias conditions. The LPE shows a linear dependence on spot positions, and the sensitivity is found to be as high as 33 mV/mm under an illumination of 2.8 W/cm2 (635 nm). The structure also exhibits a linear dependence of the LPE over a large distance (7 mm) between two electrodes, which is crucial for PSDs as the region with a linear dependence of LPE is only usable for PSDs. The LPE at different spot positions and under different illumination conditions have been investigated and explained based on the energy-band analysis. The temperature dependence of the LPE and position sensitivity is also investigated. Furthermore, the two-dimensional mapping of the lateral photovoltages reveals the potential for utilizing the 3C-SiC/Si heterostructure to detect the laser spot position precisely on a plane.