Showing papers on "p–n junction published in 2015"
TL;DR: The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface, and direct growth favors the thermodynamically preferred TMDC alloys.
Abstract: Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface.
1,011 citations
TL;DR: A broadband photodetector using a layered black phosphorus transistor that is polarization-sensitive over a bandwidth from ∼400 nm to 3,750‽nm is demonstrated and might provide new functionalities in novel optical and optoelectronic device applications.
Abstract: The ability to detect light over a broad spectral range is central to practical optoelectronic applications and has been successfully demonstrated with photodetectors of two-dimensional layered crystals such as graphene and MoS2. However, polarization sensitivity within such a photodetector remains elusive. Here, we demonstrate a broadband photodetector using a layered black phosphorus transistor that is polarization-sensitive over a bandwidth from ∼400 nm to 3,750 nm. The polarization sensitivity is due to the strong intrinsic linear dichroism, which arises from the in-plane optical anisotropy of this material. In this transistor geometry, a perpendicular built-in electric field induced by gating can spatially separate the photogenerated electrons and holes in the channel, effectively reducing their recombination rate and thus enhancing the performance for linear dichroism photodetection. The use of anisotropic layered black phosphorus in polarization-sensitive photodetection might provide new functionalities in novel optical and optoelectronic device applications. The anisotropic optical properties of black phosphorus can be exploited to fabricate photodetectors with linear dichroism operating over a broad spectral range.
973 citations
TL;DR: In this paper, the authors used molybdenum disulfide in an ultra-thin p-n junction that demonstrated ambipolar carrier transport and current rectification, and demonstrated that molybenzdisulfide has properties that make it useful for compact electronic devices.
Abstract: Molybdenum disulfide is a two-dimensional semiconducting material that has properties that make it useful for compact electronic devices. Here, the authors use molybdenum disulfide in an ultra-thin p–n junction that demonstrate ambipolar carrier transport and current rectification.
288 citations
TL;DR: In this article, the Si-doping concentration of the top n-GaN drift layer adjacent to the p-n junction was reduced using well-controlled metal-organic vapor phase epitaxy systems.
Abstract: Vertical structured GaN power devices have recently been attracting a great interest because of their potential on extremely high-power conversion efficiency. This letter describes increased breakdown voltages in the vertical GaN p-n diodes fabricated on the free-standing GaN substrates. By applying multiple lightly Si doped n-GaN drift layers to the p-n diode, the record breakdown voltages ( $V_{B}$ ) of 4.7 kV combined with low specific differential ON-resistance ( $R_{\mathrm{\scriptscriptstyle ON}}$ ) of 1.7 $\text{m}\Omega $ cm2 were achieved. With reducing the Si-doping concentration of the top n-GaN drift layer adjacent to the p-n junction using well-controlled metal-organic vapor phase epitaxy systems, the peak electric field at the p-n junction could be suppressed under high negatively biased conditions. The second drift layer with a moderate doping concentration contributed to the low $R_{\mathrm{\scriptscriptstyle ON}}$ . A Baliga’s figure of merit ( $V_{B}^{2}/R_{\mathrm{\scriptscriptstyle ON}}$ ) was 13 GW/cm2. These are the best values ever reported among those achieved by GaN p-n junction diodes on the free-standing GaN substrates.
186 citations
TL;DR: An electrostatic gating method using a solid polymer electrolyte, poly(ethylene oxide) and CsClO4, on exfoliated, multilayer 2H-MoTe2 enables the device to be efficiently reconfigured between n- and p-channel operation with ON/OFF ratios of approximately 5 decades.
Abstract: Transition metal dichalcogenides are relevant for electronic devices owing to their sizable band gaps and absence of dangling bonds on their surfaces. For device development, a controllable method for doping these materials is essential. In this paper, we demonstrate an electrostatic gating method using a solid polymer electrolyte, poly(ethylene oxide) and CsClO4, on exfoliated, multilayer 2H-MoTe2. The electrolyte enables the device to be efficiently reconfigured between n- and p-channel operation with ON/OFF ratios of approximately 5 decades. Sheet carrier densities as high as 1.6 × 1013 cm–2 can be achieved because of a large electric double layer capacitance (measured as 4 μF/cm2). Further, we show that an in-plane electric field can be used to establish a cation/anion transition region between source and drain, forming a p–n junction in the 2H-MoTe2 channel. This junction is locked in place by decreasing the temperature of the device below the glass transition temperature of the electrolyte. The idea...
121 citations
TL;DR: The authors' calculations show that h-BP is a mechanically stable 2D material with a direct band gap of 0.9 eV at the K-point, promising for both electronic and optoelectronic applications.
Abstract: Two-dimensional (2D) materials have attracted growing interest due to their potential use in the next generation of nanoelectronic and optoelectronic applications. On the basis of first-principles calculations based on density functional theory, we first investigate the electronic and mechanical properties of single layer boron phosphide (h-BP). Our calculations show that h-BP is a mechanically stable 2D material with a direct band gap of 0.9 eV at the K-point, promising for both electronic and optoelectronic applications. We next investigate the electron transport properties of a p–n junction constructed from single layer boron phosphide (h-BP) using the non-equilibrium Green's function formalism. The n- and p-type doping of BP are achieved by substitutional doping of B with C and P with Si, respectively. C(Si) substitutional doping creates donor (acceptor) states close to the conduction (valence) band edge of BP, which are essential to construct an efficient p–n junction. By modifying the structure and doping concentration, it is possible to tune the electronic and transport properties of the p–n junction which exhibits not only diode characteristics with a large current rectification but also negative differential resistance (NDR). The degree of NDR can be easily tuned via device engineering.
113 citations
TL;DR: Differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor and is capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions.
Abstract: Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.
105 citations
TL;DR: In this article, non-conventional p-n junctions were investigated using organic rubrene single crystal and 2D MoS2 as the p-and n-type semiconducting materials, respectively.
Abstract: Organic–inorganic heterostructures are an emerging topic that is very interesting for optoelectronics. Here, non-conventional p–n junctions are investigated using organic rubrene single crystal and 2D MoS2 as the p- and n-type semiconducting materials, respectively. The current-rectifying behavior is clearly observed in the junction device. The rectification ratio can be electrically tuned by the gate voltage due to the 2D nature of the heterostructure. The devices also show good photoresponse properties with a photoresponsivity of ≈500 mA W−1 and a fast response time. These findings suggest a new route to facilitate the design of nanoelectronic and optoelectronic devices based on layered inorganics and organics.
94 citations
TL;DR: Using cross-sectional electron-beam-induced current (EBIC) measurements, an increase in carrier diffusion length is found in MAPbBr3(Cl)-based solar cells upon low intensity blue laser illumination and the EBIC cross section profile indicates a p-n structure between the n-FTO/TiO2 and p-perovskite, rather than the p-i-n structures reported for the iodide derivative.
Abstract: High band gap, high open-circuit voltage solar cells with methylammonium lead tribromide (MAPbBr3) perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite-based devices remains only partially understood. Using cross-sectional electron-beam-induced current (EBIC) measurements, we find an increase in carrier diffusion length in MAPbBr3(Cl)-based solar cells upon low intensity (a few percent of 1 sun intensity) blue laser illumination. Comparing dark and illuminated conditions, the minority carrier (electron) diffusion length increases about 3.5 times from Ln = 100 ± 50 nm to 360 ± 22 nm. The EBIC cross section profile indicates a p–n structure between the n-FTO/TiO2 and p-perovskite, rather than the p–i–n structure, reported for the iodide derivative. On the basis of the variation in space-charge region width with varying bias, measured ...
88 citations
TL;DR: In this paper, an organic 2D layered material (MoS2) hybrid p-n junction with both gate-tunable diode characteristics and photovoltaic effect is presented.
Abstract: The semiconducting p–n junction is a simple device structure with great relevance for electronic and optoelectronic applications. The successful integration of low-dimensional materials in electronic circuits has opened the way forward for producing gate-tunable p–n junctions. In that context, we present here an organic (Cu-phthalocyanine)–2D layered material (MoS2) hybrid p–n junction with both gate-tunable diode characteristics and photovoltaic effect. Our proof-of-principle devices show multifunctional properties with diode rectifying factors of up to 104, while under light exposure they exhibit photoresponse with a measured external quantum efficiency of ∼11%. As for their photovoltaic properties, we found open circuit voltages of up to 0.6 V and optical-to-electrical power conversion efficiency of 0.7%. The extended catalogue of known organic semiconductors and two-dimensional materials offer the prospect for tailoring the properties and the performance of the resulting devices, making organic–2D p–n junctions promising candidates for future technological applications.
81 citations
TL;DR: In this paper, a CAVET with buried, conductive p-GaN layers as the current blocking layer is reported, with high ON current (10.9 kA/cm2) and low ON-resistance (0.4 mΩ cm2).
Abstract: The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9 kA/cm2) and low ON-resistance (0.4 mΩ cm2) are demonstrated. Non-planar selective area regrowth is identified as the limiting factor to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown vol...
TL;DR: The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.
Abstract: Graphene has been considered as an attractive material for optoelectronic applications such as photodetectors owing to its extraordinary properties, e.g. broadband absorption and ultrahigh mobility. However, challenges still remain in fundamental and practical aspects of the conventional graphene photodetectors which normally rely on the photoconductive mode of operation which has the drawback of e.g. high dark current. Here, we demonstrated the photovoltaic mode operation in graphene p-n junctions fabricated by a simple but effective electron irradiation method that induces n-type doping in intrinsic p-type graphene. The physical mechanism of the junction formation is owing to the substrate gating effect caused by electron irradiation. Photoresponse was obtained for this type of photodetector because the photoexcited electron-hole pairs can be separated in the graphene p-n junction by the built-in potential. The fabricated graphene p-n junction photodetectors exhibit a high detectivity up to ~3 × 1010 Jones (cm Hz1/2 W−1) at room temperature, which is on a par with that of the traditional III–V photodetectors. The demonstrated novel and simple scheme for obtaining graphene p-n junctions can be used for other optoelectronic devices such as solar cells and be applied to other two dimensional materials based devices.
TL;DR: In this paper, NiO-ZnO heterojunction is used for piezoelectric performance enhancement via both suppressing the screening effect in the ZnO film and forming a reliable p-n junction at the interfaces instead of the Schottky barriers.
TL;DR: In this paper, a new sandwich-like architecture using CdS nanorods embedded in a p-n junction of MoS2/N-RGO was designed to promote overall water splitting in natural water.
Abstract: Overall solar water splitting into H2 and O2 using visible light responsive photocatalyst has been considered as a clean, green, and renewable system. CdS with a suitable bandgap (2.25 eV) and band position was for a long time not considered as a promising candidate for overall solar water splitting because of its serious photo-corrosion and rapid charge recombination, although it has considerable photocatalytic activity for H2 generation in a sacrificial agent containing electrolyte. Here, we design a new sandwich-like architecture using CdS nanorods embedded in a p–n junction of MoS2/N-RGO which serves as a novel photocatalytic system that could promote overall water splitting in natural water. It was found that the p–n junction of MoS2/N-RGO not only works as the HER and OER electrocatalyst for H2 and O2 generation respectively, but also facilitates charge separation by its inner electric field. Compared to well-defined thermodynamically favored charge transport, the new charge transfer route in MoS2/CdS/N-RGO splits natural water, resulting in an essential change of the carrier separation mechanism and high anti-corrosion.
TL;DR: In this article, a few-layer C8-BTBTBT molecular crystals can be grown on monolayer MoS2 by vdW epitaxy, with pristine interface and controllable thickness down to monoline.
Abstract: van der Waals (vdW) heterojunctions formed by two-dimensional (2D) materials have attracted tremendous attention due to their excellent electrical/optical properties and device applications. However, current 2D heterojunctions are largely limited to atomic crystals, and hybrid organic/inorganic structures are rarely explored. Here, we fabricate the hybrid 2D heterostructures with p-type dioctylbenzothienobenzothiophene (C8-BTBT) and n-type MoS2. We find that few-layer C8-BTBT molecular crystals can be grown on monolayer MoS2 by vdW epitaxy, with pristine interface and controllable thickness down to monolayer. The operation of the C8-BTBT/MoS2 vertical heterojunction devices is highly tunable by bias and gate voltages between three different regimes: interfacial recombination, tunneling, and blocking. The pn junction shows diode-like behavior with rectifying ratio up to 105 at the room temperature. Our devices also exhibit photovoltaic responses with a power conversion efficiency of 0.31% and a photoresponsivity of 22 mA/W. With wide material combinations, such hybrid 2D structures will offer possibilities for opto-electronic devices that are not possible from individual constituents.
15 Dec 2015-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: P-type conversion of n−-GaN by Mg-ion implantation was successfully performed using high quality GaN epitaxial layers grown on free-standing low-dislocation-density GaN substrates as mentioned in this paper.
Abstract: P-type conversion of n−-GaN by Mg-ion implantation was successfully performed using high quality GaN epitaxial layers grown on free-standing low-dislocation-density GaN substrates. These samples showed low-temperature PL spectra quite similar to those observed from Mg-doped MOVPE-grown p-type GaN, consisting of Mg related donor–acceptor pair (DAP) and acceptor bound exciton (ABE) emission. P–n diodes fabricated by the Mg-ion implantation showed clear rectifying I–V characteristics and UV and blue light emissions were observed at forward biased conditions for the first time.
TL;DR: In this paper, a nanostructured chromium(III) oxide/tungsten(VI) oxide (Cr2O3/WO3) p-n junction photoanode is established.
Abstract: A nanostructured chromium(III) oxide/tungsten(VI) oxide (Cr2O3/WO3) p–n junction photoanode is established here. It is prepared by depositing Cr2O3 nanoparticles onto WO3 nanosheet arrays. The formation of a p–n junction is confirmed by the Mott–Schottky plot and photocurrent measurements. Electrochemical and spectroscopic methods indicate that the recombination rate of photogenerated charges becomes lower in this photoanode. Consequently, its onset potential shifts negatively by about 0.1 V and photocurrent density increases from 0.7 to 1.8 mA cm−2 at 1.8 V vs. RHE. The incident photon-to-current efficiency (IPCE) also shows a one-fold improvement. In addition, the construction of the p–n junction leads to an increase of faradaic efficiency (holes to oxygen) from 73.9% to 92.0%, which is attributed to the suppression of side reactions in water oxidation. This work will provide new inspiration for improving the performance of WO3 and other photoanodes.
TL;DR: In this paper, a Si/TiO2/Pt p-n junction semiconductor was designed for high porosity and uniformity of both TiO2 and Pt deposits.
TL;DR: In this article, the electrical properties of the p-type Si p-n junction were investigated and the typical oscillating modes of E 1 2g and A 1g were shown in the Raman spectrum of the MoS 2 film.
TL;DR: This paper demonstrates simple solution-processed, low cost, band tunable photodiodes with excellent figures of merit operated under low bias.
Abstract: Solution-processed p–n heterojunction photodiodes have been fabricated based on transition-metal oxides in which NiO and ternary Zn1–xMgxO (x = 0–0.1) have been employed as p-type and n-type semiconductors, respectively. Composition-related structural, electrical, and optical properties are also investigated for all the films. It has been observed that the bandgap of Zn1–xMgxO films can be tuned between 3.24 and 3.49 eV by increasing Mg content. The fabricated highly visible-blind p–n junction photodiodes show an excellent rectification ratio along with good photoresponse and quantum efficiency under ultraviolet (UV) illumination. With an applied reverse bias of 1 V and depending on the value of x, the maximum responsivity of the devices varies between 0.22 and 0.4 A/W and the detectivity varies between 0.17 × 1012 and 2.2 × 1012 cm (Hz)1/2/W. The photodetectors show an excellent UV-to-visible rejection ratio. Compositional nonuniformity has been observed locally in the alloyed films with x = 0.1, which i...
TL;DR: In this article, a large number of nano p-n junction heterostructures assembled by p-type Ag2O nanoparticles formed on the surface of BiVO4 nanocrystals.
TL;DR: In this paper, a layer-by-layer growth of wafer-scale GaTe with a high hole mobility of 28.4 cm2/(V·s) by molecular beam epitaxy was reported.
Abstract: Two-dimensional (2D) materials have attracted substantial attention in electronic and optoelectronic applications with the superior advantages of being flexible, transparent, and highly tunable. Gapless graphene exhibits ultra-broadband and fast photoresponse while the 2D semiconducting MoS2 and GaTe exhibit high sensitivity and tunable responsivity to visible light. However, the device yield and repeatability call for further improvement to achieve large-scale uniformity. Here, we report a layer-by-layer growth of wafer-scale GaTe with a high hole mobility of 28.4 cm2/(V·s) by molecular beam epitaxy. The arrayed p-n junctions were developed by growing few-layer GaTe directly on three-inch Si wafers. The resultant diodes reveal good rectifying characteristics and a high photovoltaic external quantum efficiency up to 62% at 4.8 µW under zero bias. The photocurrent reaches saturation fast enough to capture a time constant of 22 µs and shows no sign of device degradation after 1.37 million cycles of operation. Most strikingly, such high performance has been achieved across the entire wafer, making the volume production of devices accessible. Finally, several photoimages were acquired by the GaTe/Si photodiodes with reasonable contrast and spatial resolution, demonstrating the potential of integrating the 2D materials with silicon technology for novel optoelectronic devices.
TL;DR: In this paper, a detailed study of p-n junction CuO/TiO2-zeolite impacting on the photodecoloration of a MB solution showed that the composite was highly reusable and stable for long-running photocatalytic application.
Abstract: Highly efficient and visible-light-responsive p–n junction CuO/TiO2-zeolite heterogeneous nanostructures had been successfully synthesized by a standard impregnation method. A detailed study of p–n junction CuO/TiO2-zeolite impacting on the photodecoloration of a MB solution showed that the composite was highly reusable and stable for long-running photocatalytic application. The apparent rate constant of the CuO/TiO2-zeolite was calculated to be 0.0704 min−1, which is 1.4 times higher than that of TiO2-zeolite (k = 0.048 min−1) and 1.9 times higher than that of zeolite (k = 0.0368 min−1). The experimental results indicated that the composites had a superior photocatalytic activity for the decoloration of dye wastewater under visible light irradiation because the p–n junction was formed between CuO and TiO2. The assembly of p-type CuO produces a large number of p–n junction heterostructures on the surface of TiO2, where CuO and TiO2 form p- and n-type semiconductors, respectively. The p–n junction could efficiently suppress charge recombination, improve interfacial charge transfer, enhance visible-light adsorption and provide plentiful photocatalytic reaction active sites. This new p–n junction heteronanostructure is expected to show considerable potential application in solar-driven wastewater treatment.
TL;DR: Doping of the colloidal PbSe nanowires is compatible with device fabrication on flexible plastic substrates, promising a low-cost, solution-based route to high-performance nanowire devices.
Abstract: We report the controlled and selective doping of colloidal PbSe nanowire arrays to define pn junctions for electronic and optoelectronic applications. The nanowires are remotely doped through their surface, p-type by exposure to oxygen and n-type by introducing a stoichiometric imbalance in favor of excess lead. By employing a patternable poly(methyl)methacrylate blocking layer, we define pn junctions in the nanowires along their length. We demonstrate integrated complementary metal-oxide semiconductor inverters in axially doped nanowires that have gains of 15 and a near full signal swing. We also show that these pn junction PbSe nanowire arrays form fast switching photodiodes with photocurrents that can be optimized in a gated-diode structure. Doping of the colloidal nanowires is compatible with device fabrication on flexible plastic substrates, promising a low-cost, solution-based route to high-performance nanowire devices.
TL;DR: In this article, the critical length of a radial p-n junction SiNW solar cell was estimated to obtain optimal cell performance with minimum carrier loss in a simple radial pn junction solar cell.
TL;DR: In this paper, the p-n junction with g-C3N4 NS can enhance the separation efficiency of photogenerated carriers and light absorption ability of β-Bi2O3 particles obtained by characterization of fluorescence spectra and diffuse reflectance spectra.
Abstract: β-Bi2O3/g-C3N4 nanosheet (NS) p–n junction of g-C3N4 NS-wrapped β-Bi2O3 was fabricated via self-assembly process by electrostatic force By the analyses of scanning electron microscopy images and Fourier transform infrared spectra, the g-C3N4 NS has been wrapped on the spherical β-Bi2O3 particles Constructing p–n junction with g-C3N4 NS can enhance the separation efficiency of photogenerated carriers and light absorption ability of β-Bi2O3 particles obtained by the characterization of fluorescence spectra and diffuse reflectance spectra The photocatalytic removal rate of RhB is largely enhanced by construction of β-Bi2O3/g-C3N4 NS p–n junctions The photocatalytic ability of β-Bi2O3/g-C3N4 NS p–n junctions can be adjusted by tuning the loading amount of g-C3N4 NS The enhanced photocatalytic performance is firstly attributed to the p–n junction effect of efficient separation of photogenerated charge carriers Furthermore, the increased light absorbance of the composites also contributes to the enhanced photocatalytic ability
TL;DR: These results illustrate how the determination of reliable potential distributions from phase images of electrically biased devices requires electrostatic fringing fields, surface charges, specimen preparation damage and the effects of limited spatial resolution to be taken into account.
TL;DR: In this article, the authors demonstrate optoelectronic devices implemented on suspended p-n junction InGaN/GaN multiple quantum wells (MQWs) for the further monolithic integration of an optical source, a waveguide, and a photodetector on the same GaN-on-silicon wafer.
Abstract: We demonstrate optoelectronic devices implemented on suspended p–n junction InGaN/GaN multiple quantum wells (MQWs) for the further monolithic integration of an optical source, a waveguide, and a photodetector on the same GaN-on-silicon wafer. The fabricated suspended membrane device exhibits selectable functionalities either for efficient light-emitting diodes (LEDs) or sensitive photodetectors. Typical current–voltage (I-V) characteristics are obtained for the device operated under the LED mode, and the emitted light intensity is effectively modulated by the applied voltage. Lateral in-plane propagation of emitted light in a suspended membrane is experimentally presented. The simulation results show that the thickness-dependent optical performance can be tuned by back wafer thinning for epitaxial films. The device operated under the photodetector mode exhibits a static photocurrent on–off ratio $\eta_{s}$ of $2.25\times 10^{5}$ at a 1-V bias voltage with the illumination power of 690 $\mu\mbox{W}$ and the wavelength of 450 nm. The photocurrent also shows a rectangular pulse response of the same duration as a 1-s rectangular illumination pulse at a 0-V bias voltage with the illumination power of 1 mW. The temporal photocurrent on–off ratio $\eta_{t}$ is around $1.01\times 10^{5}$ . This paper opens a promising way to realize the monolithic integration of a LED, a waveguide, and a photodetector on a GaN-on-silicon platform.
TL;DR: In this paper, a nanoscale Co3O4-WO3 p-n junction sensor was established by using a two-step procedure (hydrothermal reaction/calcination) to decorate the surface of n-type WO3 nanorods (NRs).
Abstract: A nanoscale Co3O4–WO3 p–n junction sensor was established here. Via a two-step procedure (hydrothermal reaction/calcination), p-type Co3O4 nanoparticles were decorated on the surface of n-type WO3 nanorods (NRs). Characterization by SEM, TEM and XRD showed they contact intimately with each other. Via gas sensing test, the Co3O4–WO3 sensor displayed two times of response (Ra/Rg) than that of pure WO3 NRs sensor (toward 100 ppm acetone, 280 °C). Moreover, it also had a better selectivity towards acetone than that of pure WO3 NRs sensor. The mechanism analysis showed that its enhanced sensing performance was due to the extension of depletion layer in the p–n junction.