Semiconductor Optoelectronic Devices Research Articles

Design and fabrication of photonic crystal structures by single pulse laser interference lithography

Photonic crystal (PhC) structures formed by periodic surface nanostructuring have emerged as pivotal elements for controlling light-matter interactions. One important application is reducing losses due to the high surface reflectivity of semiconductor optoelectronic devices, such as enhancing light absorption in photovoltaic cells or improving light extraction in light-emitting diodes (LEDs). Although various methods for fabricating such structures have been documented, the utilization of single pulse laser interference lithography (LIL) using commercial photoresist and its subsequent effective use as an etch mask has not been previously reported. Rapid exposure of photoresists with single nanosecond pulses offers benefits for high throughput patterning and reduces the requirement for a stable optical platform. We have successfully employed single pulse LIL to fabricate antireflective PhC structures on GaAs substrates using a commercial photoresist. Exposure is performed with single 7 ns 355 nm pulses of relatively low energy (<10 mJ). High-quality nanohole arrays of pitch of approximately 365 nm are fabricated and depths up to 400 nm have been etched using inductively coupled plasma (ICP) through the exposed photoresist mask. Reflectivity analyses confirmed that these structures reduce the average reflectance of the GaAs to below 5 % across the 450 nm to 700 nm visible wavelength range. The fabrication of PhC structures using this approach has potential for low-cost wafer-level patterning to provide improved light extraction in LEDs and enhanced light trapping in solar cells.

Self-biased photoelectrochemical photodetector based on liquid phase exfoliated SnSe nanosheets

The present article involves a liquid phase exfoliation technique to synthesize SnSe nanosheets. These nanosheets are deposited on an ITO glass substrate to make a thin film via an electrophoretic deposition (EPD) technique. Through the use of energy-dispersive X-ray analysis (EDAX), the cleanliness and chemical compositions of the film are examined. The surface topography of the deposited film is carried out by scanning electron microscopy (SEM). The orthorhombic crystal structure of SnSe thin film is verified by X-ray diffraction (XRD) analysis. The optical gap energy and absorbance profiles also exhibit a morphology-dependent response, as measured by ultraviolet–visible (UV–vis) spectroscopy. The Photoresponse performance of SnSe thin film-based PEC-type photodetector was carried out under illumination of poly and monochromatic wavelengths. SnSe nanosheet-based photodetector showed a maximum photocurrent of 14.50 μA under polychromatic light of intensity 100 mW/cm2, at zero bias. This study demonstrates how the Requirement for TMC semiconductors in optoelectronic devices increases due to their exceptional photoresponse performance.

Ultrafast Charge Transfer Cascade in a Mixed-Dimensionality Nanoscale Trilayer

Innovation in optoelectronic semiconductor devices is driven by a fundamental understanding of how to move charges and/or excitons (electron-hole pairs) in specified directions for doing useful work, e.g. for making fuels or electricity. The diverse and tunable electronic and optical properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) and one-dimensional (1D) semiconducting single-walled carbon nanotubes (s-SWCNTs) make them good quantum confined model systems for fundamental studies on charge and exciton transfer across heterointerfaces. In nature, the photosynthetic apparatus achieves long-lived charge separation through a charge transfer cascade that consists of a series of thermodynamically downhill charge transfer reactions. Inspired by photosynthesis we create a unique mixed-dimensionality 2D/1D/2D MoS2/SWCNT/WSe2 hetero-trilayer. Photoexcitation of this trilayer heterostructure allows us to overcome both intralayer and interlayer exciton binding energies, resulting in coulombically unbound charges with microsecond recombination lifetimes. In contrast to previously demonstrated 2D/2D/2D trilayers based solely on monolayer TMDC layers, the very large charge mobilities and extended electron network of the 1D semiconducting SWCNT layer helps charges delocalize and diffuse away from the interface at which each type of charge is generated. Interestingly, the hetero-trilayer also appears to enable efficient hole transfer from SWCNTs to WSe2, which is not observed in the identically prepared WSe2/SWCNT heterobilayer, suggesting that new dynamic pathways may be opened by increasing the complexity of nanoscale heterostructures. Our work suggests "mixed-dimensionality" TMDC/SWCNT based hetero-trilayers as both interesting model systems for mechanistic studies of carrier dynamics at nanoscale heterointerfaces, and for potential applications in advanced optoelectronic systems.

A Review on the Zone Refining Process Technology toward Ultra‐Purification of Gallium for GaAs/GaN‐based Optoelectronic Device Applications

AbstractUltrapure gallium up to 99.9999%/ 99.99999% (6N/7N) purity level is a highly demanding material needed for the growth of gallium‐based group III–V semiconductor compounds and optoelectronic devices. However, general extraction of gallium from Bayer liquor contains high impurity content and ultra‐purification of the same cannot be accomplished by a single step. Thus, the purpose of this review is to assess various purification processes for the production of ultra‐pure gallium and to critically examine its applications in the optoelectronics industry. Through this research survey, it is found that zone refining of the zone melting process stands tall over other methods in purifying materials even up to 13N. Hence, scientists are adopting detailed mathematical models and simulation tools for designing unique zone refining systems for material purification. Current‐day technology even adopts intelligence methods such as machine learning, which sheds light on the importance of different zone refining parameters that influence the purification process. Here, the practical aspects of zone refining and how the feedback from the theoretical models or performance prediction through intelligence methods can be effectively incorporated into practice have also been emphasized

Research progress on the application of two-dimensional layered semiconductors in optoelectronic devices

In recent years, traditional 2D layered materials such as graphene have been widely used in the photoelectric area. As the emerging research and development of 2D layered materials, there are more and more newly developed 2D layered semiconductors being applied to this field, such as MoS2, phosphorene, and other nanomaterials. 2D layered MoS2 can be utilized as sensitive elements to obtain high-performance photodetectors with high responsivity, high current response rate, and short recovery time. Moreover, because phosphorene has adjustable bandgap width and strong light absorption, it has more potential in aspects of other semiconductors, and application in photoelectric devices. This article introduced the structures of some common 2D layered semiconductors, discussed their applications in photoelectric fields, and pointed out their limitations. For example, transition metal dichalcogenide (TMDC) materials generally have low carrier mobility, and black phosphorus is prone to adsorb water molecules from the air, leading to changes in its physical and chemical properties. Finally, improvement methods of applications and prospects for future development were provided.

Structural, Optical, and Electronic Properties of Epitaxial β‐(AlxGa1‐x)2O3 Films for Optoelectronic Devices

AbstractBandgap engineering in monoclinic gallium oxide (β‐Ga2O3) is a powerful strategy for designing semiconductor optoelectronic devices with specific functionalities. In this work, aluminum doping is utilized to modulate the bandgap of Ga2O3. By growing epitaxial β‐(AlxGa1‐x)2O3 (0≤ x≤ 0.84) films on c‐plane sapphire substrates using RF magnetron sputtering, it allowed to tune the energy bandgap, achieving values as high as 6.10 eV. The increased luminescence intensity is attributed to the recombination between donor and acceptor transitions induced by Al doping, resulting in more defects. Additionally, the luminescent band experienced blueshifts due to the enhanced bandgaps. Moreover, density of functional theory (DFT) simulations confirmed the sensitivity of the bandgap to Al content, distinguishing between Ga‐dominated (x &lt; 0.5) and Al‐dominated (x &gt; 0.5) β‐(AlxGa1‐x)2O3. Notably, the bandgap increased more rapidly in Ga‐dominated structures compared to Al‐dominated ones. The electronic structure analysis revealed a redistribution of Ga d states from valence to conduction bands, attributed to the introduction of numerous Al p states. These combined experimental and detailed electronic structure investigations proved crucial insights for designing the structure and exploring potential applications of β‐(AlxGa1‐x)2O3 in photonic devices.

Ultrafast Charge Transfer Cascade in a Mixed-Dimensionality Nanoscale Trilayer.

Innovation in optoelectronic semiconductor devices is driven by a fundamental understanding of how to move charges and/or excitons (electron-hole pairs) in specified directions for doing useful work, e.g., for making fuels or electricity. The diverse and tunable electronic and optical properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) and one-dimensional (1D) semiconducting single-walled carbon nanotubes (s-SWCNTs) make them good quantum confined model systems for fundamental studies of charge and exciton transfer across heterointerfaces. Here we demonstrate a mixed-dimensionality 2D/1D/2D MoS2/SWCNT/WSe2 heterotrilayer that enables ultrafast photoinduced exciton dissociation, followed by charge diffusion and slow recombination. Importantly, the heterotrilayer serves to double charge carrier yield relative to a MoS2/SWCNT heterobilayer and also demonstrates the ability of the separated charges to overcome interlayer exciton binding energies to diffuse from one TMDC/SWCNT interface to the other 2D/1D interface, resulting in Coulombically unbound charges. Interestingly, the heterotrilayer also appears to enable efficient hole transfer from SWCNTs to WSe2, which is not observed in the identically prepared WSe2/SWCNT heterobilayer, suggesting that increasing the complexity of nanoscale trilayers may modify dynamic pathways. Our work suggests "mixed-dimensionality" TMDC/SWCNT based heterotrilayers as both interesting model systems for mechanistic studies of carrier dynamics at nanoscale heterointerfaces and for potential applications in advanced optoelectronic systems.

Sustained robust exciton emission in suspended monolayer WSe2 within the low carrier density regime for quantum emitter applications

The development of semiconductor optoelectronic devices is moving toward low power consumption and miniaturization, especially for high-efficiency quantum emitters. However, most of these quantum sources work at low carrier density regions, where the Shockley–Read–Hall (SRH) recombination may be dominant and seriously reduce the emission efficiency. In order to reduce the effect of carrier trapping and sustain a strong photoluminescence (PL) emission under low power pumping conditions, we investigated the influence of “suspending” a monolayer of tungsten diselenide (WSe2), a novel two-dimensional quantum material. Not only the PL intensity but also the fundamental photoluminescence quantum yield (PLQY) has exhibited a huge, order-scale enhancement through suspending; even surprisingly, we found the PLQY improvement to be far significant under small pumping powers and observed an exponential increase in tendency toward an even lower carrier density region. With its strong excitonic effect, suspended WSe2 offers a solution to reduce carrier trapping and participate in non-radiative processes. Moreover, in the low-power range, where SRH recombination dominates, suspended WSe2 exhibited a remarkably higher percentage of excitonic radiation compared to contacted WSe2. Herein, we quantitatively demonstrate the significance of the suspended WSe2 monolayer in a low carrier density region, highlighting its potential for developing compact, low-power quantum emitters in the future.

Band alignment engineering at ultra-wide bandgap GeO2/SiO2 heterointerfaces

Owing to the tremendous contribution for the carrier transport across the interface, the band alignment engineering in oxide semiconductor heterojunctions (OSHs) is of vital importance for developing oxide semiconductor optoelectronic devices. Here, we have deposited a series of ultra-wide bandgap GeO2 thin films on quartz substrates by the direct-current reactive magnetron sputtering method to construct the OSHs and described the effect of the flow rate ratios of O2 and Ar (O2:Ar) and substrate temperatures on the bandgap energies of GeO2 films and band alignments at the interface of OSHs. Based on the energy loss spectra of O 1 s peaks, the tunable bandgap energies ranging from 4.37 to 5.37 eV have been achieved for GeO2 films. An obvious variation of band alignments has been found in the OSHs, suggesting the dramatically influence of deposition conditions. The valence band offsets are determined to be ranging from 1.85 to 1.96 eV (from 1.88 to 1.95 eV) and the conduction band offsets are calculated to be ranging from 1.88 to 2.78 eV (from 1.74 to 2.19 eV) for the GeO2 films grown at different O2:Ar (substrate temperatures), respectively, due to the nonlocalization of the oxygen vacancies in valence band and the formation of single hexagonal phase in the GeO2 film. Our findings on the band alignment engineering in the GeO2/SiO2 heterointerfaces will open the way for developing GeO2-based optoelectronic devices.

Photoelectric properties of two-dimensional electron gas at the (Ga0.5Al0.5)2O3/SrTiO3 heterointerfaces

We report a two-dimensional electron gas created at the (Ga0.5Al0.5)2O3/SrTiO3 heterointerfaces with different deposition temperatures and thicknesses by a pulsed laser deposition method. It is found that the critical deposition temperature for the metal-to-insulator transition is about 400 °C with a thickness of 43.2 nm. The carrier density and mobility of sample at the deposition temperature of 300 °C are 1012 cm−2 and 67.2 cm2 V−1 s−1 at 50 K, respectively. The thickness of the conductive layer is ∼4.0 nm estimated from the anisotropic magnetoresistance. The bandgaps of films deposited at different temperatures are in the range of 5.6–5.9 eV. Furthermore, the heterointerfaces have a strong response to 360 nm light with a relative resistance change of ∼70%. Our results are related to the charge transfer due to the oxygen defect at the interfaces, which provides a way for the development of third-generation semiconductor optoelectronic devices.

A REVIEW OF EPOXY-NANOCOMPOSITE PROPERTIES

Epoxy resins have been the subject of many studies as a consequence of their extensive usage in recent years. The brittleness and low resistance to propagation and crack initiation of epoxy resins are well-recognized characteristics. Therefore, in recent years, experts have concentrated on increasing epoxy resin's fracture resistance. Adding inorganic nanoparticles like titanium dioxide (TiO2) TiO2, silica (SiO2), carbon black, alumina (Al2O3), and others to the polymer matrix is one of the most investigated techniques in polymer science. Despite having a modest nanofiller content, the resulting nanocomposites may enhance their thermal, mechanical, rheological, electrical, and optical characteristics. These nanocomposites are an alternative to metal-based materials. They have great promise as multifunctional materials in a range of applications, including optoelectronic devices, semiconductor devices, civil engineering, automotive, and aerospace. To show potential future directions and market prospects for polymer nanocomposites reinforced with TiO2 nanoparticles, current results, and trends have been examined and highlighted. In addition, the current review surveys many studies that highlighted using nanoparticles as reinforcement, their different structure, the interface, and the geometry and structure of the resulting nano-materials reinforced resin.

Photo-emission electron gun and electron optical simulation for ultrafast scanning electron microscope

Ultrafast scanning electron microscope (USEM) integrates pump-probe technique with microscopic imaging, enabling the visualizing of photon-induced surface charge dynamics with high spatial and temporal resolution. This capability is crucial for high-resolution detection of semiconductor surface states and optoelectronic devices. This work discusses the parametric design of a thermionic emission electron gun that has been modified into a photoemission electron gun, based on a home-built ultrafast scanning electron microscope. Given that the dose of the photoemitting electron beam is usually much lower than that of thermionic emission, the transition to photoemission requires the removal of the self-bias voltage function of the original electron microscope power supply to ensure the normal operation of the Wehnelt electrode. We quantitatively analyze the dependence of bias voltage, cathode, Wehnelt electrode, and anode on the position, size and divergence angle of crossover, which helps to improve the parameter adjustment of the modified electron gun. The analysis results indicate that if the distance between the Wehnelt electrode and the anode is adjusted from 8 to 23 mm, the distance between the filament and wehnelt can be changes from 0.65 to 0.45 mm to cooperate with the bias adjustment, so that the normal use of high-resolution thermionic emission mode, low voltage mode and photoemission mode can be realized. Subsequently, the effect of the mirror’s position on the electron optical path is analyzed. It is found that when the anode is raised 1.4 mm above the mirror, the influence on the electron optical path can be ignored. Additionally, the zero-of-time and temporal broadening of the photo-electron pulse are further simulated. The results indicate that with the increase of bias voltage, the time zero of photoemission will be delayed and the temporal broadening will become larger. This study lays a foundation for the future development of ultrafast electron microscope and the design of photoemission electron sources.

AlN interlayer-induced reduction of dislocation density in the AlGaN epilayer

The ultrawide-bandgap AlGaN alloy system shows great potential for advancing the next generation of UV optoelectronic devices.

Synthesis and Some Electrochemical Properties of Carbazole Derivative Monomers for Optoelectronic Device Design

Low-cost instruments are used to achieve high sensitivity, accuracy and precision with electrochemical techniques, making them the most suitable analytical methods used to investigate the electrochemical properties of a new molecule. Among these techniques, cyclic voltammetry, which is widely employed, allows for the determination of electronic characteristics such as molecular energy levels and orbital structure, redox properties, sensor capabilities, surface activity, and more. The carbazole molecule can undergo derivatization from various positions, allowing for alterations in its electrical and optical properties. These compounds serve as heterocyclic building blocks that can be utilized as materials for organic sensitizers and semiconductors in optoelectronic devices. Due to the presence of a hydrogen atom in the nitrogen-hydrogen (N-H) bond within the carbazole structure, which can be replaced with different functional groups, carbazole is highly suitable for nitrogen-based derivatization studies. In this study, two different carbazole monomers (IIa and IIIa), which could be potential optoelectronic, were synthesized using the Ullman and Suzuki-Miyaura reaction and characterized using 1H NMR, 13C NMR, UV-Vis, and Flouresence spectroscopy techniques. The cyclic voltammetry experiments were performed using three different working electrodes (Au, Gc, Pt disk electrodes) for each compound. Since the optimum oxidation of the compounds was obtained from the voltammograms on the gold disk electrode, this electrode was used in the calculation of energy levels. HOMO and Eg values of the compounds were deduced from cyclic voltammetry experiments and the optical absorption bands, respectively.

Synthesis and investigation of the structure, thermal, optical, and electrical properties of poly (indol-thiazolo-thiadiazole) derivatives at room temperature

This research work is intended for the novel synthesis and study of structural, thermal, optical, electrical, and dielectric properties of semiconductor poly (2-amino-5-(1H-indolyl)-5H-thiazolo[4,3-b]-1,3,4-thiadiazole) (PAITTD) and its N-substituted indole derivatives with a side chain containing chlorobenzoyl (PACBITTD) and bromobenzene sulphonyl (PABBSITTD). The characterization techniques such as H1NMR, FTIR, SEM, and TGA/DSC ensured the structural and thermal properties of the as-synthesized polymers. In addition, the molecular weight of the PAITTD, PACBITTID, and PABBSITTD was calculated via H1NMR technique. The optical band gap as obtained from the absorbance study was found to be in the range of 1.5 eV to 2.58 Ev. Moreover, the ground-state geometries and the absorption wavelengths for the studied compounds were investigated by DFT and TD-DFT, where the theoretical results show coincidence with these of the experimental where the calculated (λmax) values are approximately near to the experimental (λmax) values for the PAITTD, PACBITTID, and PABBSITTD. The impedance ac conductivity and dielectric properties of the PAITTD, PACBITTID, and PABBSITTD were performed in the frequency ranges from 20 Hz to 10 MHz at room temperature, where their values were 3.0 × 10−7, 8.7 × 10−7, and 2.6 × 10−6, respectively. The Nyquist plot confirmed the presence of both grain and grain boundary effects for conducting PAITTD, PACBITTID, and PABBSITTD, and Double relaxation behavior was also observed. The variation of ac conductivity with frequency obeys the modification of Jonscher’s universal power law (JUPL). Based on the optical and electrical properties, synthetic PAITTD, PACBITTID, and PABBSITTD are promising materials in the design of optoelectronic semiconductor devices.

Photon recycling in organic semiconductor films using plasmonic metasurfaces

Photon recycling (PR) is a type of iterative self-absorption and re-emission by semiconductors. It plays an important but often-overlooked role in the performance of semiconductor optoelectronic devices. Additionally, it has not previously been investigated in the case of organic semiconductors, despite their propensity to exhibit for self-absorption. In this work, we study PR in thin films of three different organic semiconducting polymers on a variety of different surfaces to investigate the role of PR on the emission from the films. We show that PR is strongly affected by the substrate surface type and the morphology of the semiconductor. Silver grating-based metasurfaces and symmetric dielectric waveguides increase PR by up to a factor of 1.72 in all organic thin films compared to those on planar silver surfaces. However, polymer films with significant surface roughness do not show strong PR effects due to reduced guiding of emission in the plane of the film. Additionally, the luminescence quantum yield of all polymers is enhanced by both silver nanoparticle- and grating-based metasurfaces (by up to factors of 1.7 and 1.5, respectively) compared to the planar silver surfaces. This is attributed to the Purcell effect and improved extraction of emission coupled to surface plasmon polariton (SPP) modes. This study demonstrates that PR can be achieved in organic semiconductors, and it is strongest for surfaces and structures that promote both high quantum yield and in-plane waveguiding at the semiconductor emission wavelength.

Strain and interface engineering of MoS2 nanosheets decorated with Ag nanoparticles and its light-matter coupling in photoexcitation

The interfacial stress and electron transfer of metal decorates transition metal dichalcogenides (TMDs) are very important for the novel two-dimensional (2D) semiconductor optoelectronic device technology in the future. Herein, strain and interface engineering of molybdenum disulfide (MoS2) nanosheets decorated with Ag nanoparticles (Ag/MoS2) for controlled charge transfer and electron excitation-relaxation is presented. The effect of strong random scattering on the transport and electron localization phenomena of MoS2 is experimentally investigated. Exploring the charge fast transfer channel constructed by the plasma structure and the separated excited states of Ag, as well as explains the regulating mechanism of the optical absorption for TMDs in time domain. The finite-difference time-domain near-light field is used to simulate the effect of Ag content on the electromagnetic field distribution of MoS2, and then the modification of MoS2 is determined by controlling Ag content. Whilst, we can reveal the excellent light material interaction effect and ultrafast electron transfer mechanism of heterojunction surface contact sites. The E12g peak undergoes splitting, which originates from the lattice mismatch between Ag particles with plasma structure and MoS2, confirming the strong interfacial stress effect between them. On the basis of interfacial stress as well as the effective charge transfer, the Ag/MoS2 composites exhibit excellent excitation and emission behaviors. The local surface plasmon resonance effect of Ag nanoparticles is expected to adjust of nonlinear optical for TMDs. Specifically, we will regulate the ultrafast laser photon induced nonlinear absorption behavior by adjusting the Ag content and contact mode. The local strain generation on the Ag/TMDs boundary provides a new method for the design of new heterogeneous materials, and will be of great significance to investigate the contact physical behavior and application between metals decorates two-dimensional semiconductors.

First-principles study of metals, metalloids and halogens doped monolayer MoSe2 to tune its electronic properties

Owing to their small band-gap characteristics, two-dimensional transition metal dichalcogenides (TMDCs) have garnered a lot of attention. Herein, we studied the electronic as well as structural properties of doped monolayered MoSe2 with different dopants at the selenium (Se) site employing the density functional theory (DFT) using generalized gradient approximation (GGA). To ascertain bonding nature electron localization function (ELF) was used and Phonon spectra computations were done for dynamical stability tests. We systematically explored the electronic properties of monolayer MoSe2 doped with X-atoms (X comprises of metals Li, Be, Al; metalloids B, Si; non-metals (NMs) C, N, P, O and the NM atoms belonging to halogen group (F, Cl). We compared our outcomes with available experimental and other calculated results in the literature. The appearance of impurity lines in the energy gap causes to diminish the band gaps of doped MoSe2. The change in doping site and dopant element results in a significant reduction in the bandgap of doped MoSe2. To gain more insight into the electronic properties of X-doped MoSe2 monolayer, the partial density of states (PDOS) of the dopants and neighbour Mo atoms are attached to the band structures. Our results give pleasing data regarding the optimization of bandgap which shows that halogen dopant provided n-type doping while the rest of the elements provided p-type doping in MoSe2, which helps to understand the electrical conductivity in addition to their utilization in semiconductor and other optoelectronic devices. We are optimistic that the findings in this work will help experimentalists to carry out their research on a real-world application, which will also widen the investigation of transition-metal dichalcogenides (TMDs) in other sectors.

Ultraviolet photodetectors based on ZnO nanowires with SiO2/ZnO multilayers

Ultraviolet photodetectors (UV PDs) have been a frequently studied focus of optoelectronic semiconductor devices because of their large range of applications. As one of the most famous materials in third-generation semiconductors, ZnO-based UV PDs have received a great deal of attention in various research areas. Due to the carrier transport channel and higher exciton bond energy, ZnO nanowires (NWs) have better photoelectron sensitivity under UV light than ZnO films. Here, well-organized ZnO NWs were fabricated on ZnO-seeded substrates via a hydrothermal method. Multilayers of double SiO2/ZnO(S/Z) layers were designed on the NWs, and the Schottky barrier was introduced by the close contact of the ZnO NWs and gold electrodes to improve the performance of ZnO UV PDs. Characteristics of the dark current, photocurrent, rise time, decay time, photo-to-current ratio (S), and responsivity values (Rs) of the PDs were studied. Furthermore, multilayer UV PDs were achieved on both Si and quartz substrates. S of the ZnO S/Z-based UV PDs fabricated on a silica substrate can reach 55.57, which is better than the values of ZnO UV PDs reported previously. Compared with silica-based UV PDs with S/Z layers, quartz-based UV PDs with S/Z layers show a higher performance of Rs, which reach 12.62 A/W. ZnO NWs with multilayers and the Schottky contact between ZnO NWs and Au are promising candidates in high-sensitivity UV PDs.

Photoelectric properties and persistent photoconductivity of GaN-based ultraviolet photodetectors

Persistent photoconductivity deeply affects the performance of the photodetector, and has been studied in a variety of semiconductor optoelectronic devices. In this work, AlGaN/GaN metal-heterojunction-metal (MHM) ultraviolet (UV) detectors and GaN metal-semiconductor-metal (MSM) ultraviolet detectors were prepared using transverse Schottky contacts, and characterized at different temperatures, light intensity and bias voltage. The two-dimensional electron gas (2-DEG) at the Schottky heterojunction of AlGaN and GaN is used to generate high-speed electron mobility, which significantly improves the response speed and responsivity of photogenerated carriers. Under the illumination of 365 nm center ultraviolet light with an intensity of 4.4 mW/cm2, the photocurrent can reach 434 μA-MHM and 38 μA-MSM (25 °C), and the attenuation rate increase by 2.8 times, 5 times and 3.7 times with temperature (25 °C-250 °C), bias voltage (5/10/15 V), and light intensity (0.33/1.1/4.4 mW/cm2), respectively, and the attenuation rate reaches 50∼80 times.