Showing papers on "p–n junction published in 2022"

1.2 kV/25 A Normally off P-N Junction/AlGaN/GaN HEMTs With Nanosecond Switching Characteristics and Robust Overvoltage Capability

Abstract: With a reverse p-n junction in the gate stack design, this work demonstrates a 1.2 kV/25 A normally off p-n junction/AlGaN/GaN high-electron mobility transistor (PNJ-HEMT). Benefiting from the robust gate terminal, the PNJ-HEMT exhibits a large gate breakdown voltage of 18.2 V and a positive threshold voltage of 1.7 V, enabling a wide gate-bias window. Thereafter, with an applicable V GS of 10 V, the transient switching characteristics in nanosecond timescale (11.7-ns rise time and 10.5-ns fall time) and notable immunity to dynamic R on degradation, as well as record-high dynamic breakdown voltage (1.62 kV) under transient overvoltage have been demonstrated. In particular, rugged reliability is validated after over 1-million times dynamic breakdown with a 1.5-kV peak overvoltage. To the best of our knowledge, this is the first demonstration of high- V GS (10 V) GaN HEMT's circuit-level operating capability with considerable reliability, and has well exceeded the V GS limit of 5–7 V in conventional p -GaN gate-terminal devices, thus possessing great potentials in high-power, high-frequency, and high-reliability applications.

Spray pyrolysis synthesis of a semi-transparent p-CuCrO2/n-ZnO heterojunction: Structural, optical, and electrical properties

Abstract: A CuCrO2/ZnO heterojunction diode was successfully fabricated by ultrasonic spray pyrolysis. The high quality of the layers constituting the diode was determined by XRD, SEM, Ellipsometry, I–V and Impedance spectroscopy measurements, as well as by their optical properties. Backscattered electron microscopy allowed to resolve each layer of the junction. The high density of the films was inferred through the refractive index of the films: 2.02 and 1.97 for the ZnO and the CuCrO2 layers, respectively. I–V measurements showed the characteristic rectification of the diodes, approaching a figure of 107 @ ± 4.5 V. Impedance spectroscopy results showed four different activation energies attributed to the bulk conductivities of CuCrO2 and ZnO, and to the CuCrO2–ZnO and Au–CuCrO2 junctions. The %T of the diode varied from 20% at 400 nm up to 70% at 700 nm, leading to a device that can be classified and used as a semi-transparent diode.

Homogeneous Palladium Diselenide pn‐Junction Diodes for Reconfigurable Circuit Applications

Abstract: Layered 2D materials, owing to their unique physical and electrical properties, have significant potential for use in future nanomaterial‐based electronic devices. Among these, palladium diselenide (PdSe2) has recently emerged as a distinct 2D material with air stability and strong ambipolar property. In this study, the versatility of a PdSe2‐based split‐gate field‐effect transistor (SG‐FET) using its stable ambipolar nature is demonstrated. By applying sequentially polarized SG biases, the PdSe2 SG‐FET could be operated as a homogeneous and reconfigurable pn‐junction diode. The optimized h‐BN/PdSe2/h‐BN sandwich SG‐FET exhibits almost symmetric behaviors in the n‐ and p‐channel regions, enabling a reconfigurable single‐inversion AND (SAND) logic gate function, which can be used as a phase difference‐detection circuit composed only of a single component. It is believed that this approach to the reconfigurable diode and its circuit application paves the way for future 2D material‐based electronics.

Overview and loss analysis of III–V single-junction and multi-junction solar cells

Abstract: The development of high-performance solar cells offers a promising pathway toward achieving high power per unit cost for many applications. Because state-of-the-art efficiencies of single-junction solar cells are approaching the Shockley-Queisser limit, the multi-junction (MJ) solar cells are very attractive for high-efficiency solar cells. This paper reviews progress in III–V compound single-junction and MJ solar cells. In addition, analytical results for efficiency potential and non-radiative recombination and resistance losses in III–V compound single-junction and MJ solar cells are presented for further understanding and decreasing major losses in III–V compound materials and MJ solar cells. GaAs single-junction, III–V 2-junction and III–V 3-junction solar cells are shown to have potential efficiencies of 30%, 37% and 47%, respectively. Although in initial stage of developments, GaAs single-junction and III–V MJ solar cells have shown low ERE values, ERE values have been improved as a result of several technology development such as device structure and material quality developments. In the case of III–V MJ solar cells, improvements in ERE of sub-cells are shown to be necessary for further improvements in efficiencies of MJ solar cells.

Design of a 6 kV Beta-Ga2O3 PN Heterojunction Diode with Etched Double-Layered NiO with a Figure of Merit of 10 GW/cm2

Abstract: This study proposes a NiO/β-Ga2O3 etched heterojunction extension termination design for NiO/β-Ga2O3 PN diode to fulfill the application of 6 kV high-voltage with a considerably outstanding power figure of merit 10 GW/cm2, validated and optimized by sentaurus TCAD software. The results indicated the optimum termination parameters L=20mm and DJET=2.3×1013cm-2 for the single junction termination extension structure with 4000V breakdown voltage, and L1=L2=20mm, DJET1=4×1013cm-2 and DJET2=2.3×1013cm-2 for the double junction termination extension structure with 6000V. Moreover, to evaluate the power figure of merit of the optimized devices, the specific resistances were extracted from the forward characterizations with setting appropriate electron and hole mobility from experiment results, which exhibited a power figure of merit of 4.7 GW/cm2 for the single junction termination extension and 10 GW/cm2 for double junction termination extension. Meanwhile, utilizing the Poisson equation calculated the ideal one-dimension electric field at NiO/Ga2O3 interface in Ga2O3 for the optimized devices, the single junction termination extension with 5.3MV/cm at reverse 4000V, and 7.3MV/cm of the double junction termination extension incredibly approached Ga2O3 critical breakdown electric field of 8MV/cm at reverse 6000V, demonstrating our designed device structures possess immense potential for high-voltage power application.

Construction a novel Co 2 P/TiO 2 Z‐scheme junction for efficient solar‐driven photocatalytic H 2 evolution

Abstract: Photocatalytic hydrogen production is a sustainable method to alleviate the energy crisis. Herein, the Co2P/TiO2 Z-scheme junction photocatalysts without noble metal are synthesized by a simple hydrothermal method. Compared to pure TiO2 simple, the Co2P/TiO2 Z-scheme junction photocatalysts exhibit much more excellent photocatalytic H2-evolution activity, which suggests the Z-scheme junction has a positive influence on the photocatalytic hydrogen production. Particularly, the optimal 3 wt% Co2P/TiO2 displays the most outstanding photocatalytic activity with the hydrogen evolution rate of 409.5 μmol h−1 g−1, which exceeds that of pure TiO2 by almost 17 times (23.6 μmol h−1 g−1). The function of Z-scheme junction in Co2P/TiO2 hybrid that enhances the separation of electron–hole pairs is confirmed by the photoluminescence spectra, electrochemical impedance spectroscopy, and transient photocurrent responses. It is also suggested in these results that the Co2P is a cocatalyst in Co2P/TiO2 system. And, the process of electron transfer is investigated by the Kelvin probe instrument. It is clearly demonstrated that the Z-scheme junction plays a significant role in the effective charge separations of holes and electrons. Herein, a new method of synthesizing TiO2-based photocatalysts with high photocatalytic performance is offered.

Technological Causes of p-n-Junction Break-down of Silicon p-i-n Photodiodes

Abstract: During the manufacture of coordinate quadrant p-i-n photodiodes with a high reverse bias voltage Ubias≥200 V, it was observed the presence of a systematic lack of products at the level of the dark current of one (rarely several) photosensitive element. After measuring the volt-ampere characteristics, it was seen that the cause of this is a breakdown of the p-n junction. Effective methods of increasing the breakdown voltage are reducing the specific resistance of the silicon used, increasing the thickness of the substrate and the depth of the p-n junctions, reducing the concentration of alloying impurities, but these methods should be used in cases that allow the degradation of the relevant parameters to be neglected. In particular, it is necessary to provide a level of technology that reduces the probability of a breakdown. A number of technological factors that can be the reasons for reducing the breakdown voltage of the p-n junction have been established and investigated. Strong influence on the breakdown voltage. have crystallographic defects, in particular dislocations falling into the region of the p-n junction. By reducing the concentration of alloying impurities, it is possible to significantly reduce the density of dislocations with a small increase in the levels of dark currents. This helps to eliminate the probability of a breakdown. After operations of sprinkling chrome-gold on the reverse side of such a substrate, the appearance of breakdowns was detected. The cause of which are defects formed as a result of local melting of silicon when gold "droplets" with a temperature higher than the melting temperature of silicon fall on it, as a result of boiling in the evaporator. Іt is possible to reduce the probability of the appearance of these defects by spraying from closed evaporators or by increasing the etchability of spraying on the damper. During photolithography, in particular, when etching windows in the oxide, etching wedges are formed, which direct the output of the p-n junction to the surface at an acute angle. These areas are places with an increased level of electric field intensity, respectively, places of probable localization of the breakdown. This can be avoided by using photoresists that provide minimal etching wedges. Irregularities between the oxide windows can also lead to a decrease in the probo voltage, the probability of this can be reduced by careful control of the development and exposure operations and the use of defect-free templates. Another reason for a breakdown can be a violation of the p-n junction due to welding of the contact terminals. In this case, it is a thermal breakdown. This can be avoided by increasing the size of the contact pads with their expansion on silicon oxide, accordingly, welding on the surface of the oxide reduces the probability of a hole. Another method is a local increase in the depth of the p-n junction, but in this case additional technological operations must be carried out.

Integration of photovoltaic and photogating effects in a WSe2/WS2/p-Si dual junction photodetector featuring high-sensitivity and fast-response

Abstract: Two-dimensional (2D) material-based van der Waals (vdW) heterostructures with exotic semiconducting properties have shown tremendous potential in next-generation photovoltaic photodetectors. Nevertheless, these vdW heterostructure devices inevitably suffer from a compromise between high sensitivity and fast response. Herein, an ingenious photovoltaic photodetector based on a WSe2/WS2/p-Si dual-vdW heterojunction is demonstrated. First-principles calculations and energy band profiles consolidate that the photogating effect originating from the bottom vdW heterojunction not only strengthens the photovoltaic effect of the top vdW heterojunction, but also suppresses the recombination of photogenerated carriers. As a consequence, the separation of photogenerated carriers is facilitated and their lifetimes are extended, resulting in higher photoconductive gain. Coupled with these synergistic effects, this WSe2/WS2/p-Si device exhibits both high sensitivity (responsivity of 340 mA W−1, a light on/off ratio greater than 2500, and a detectivity of 3.34 × 1011 Jones) and fast response time (rise/decay time of 657/671 μs) under 405 nm light illumination in self-powered mode. Finally, high-resolution visible-light and near-infrared imaging capabilities are demonstrated by adopting this dual-heterojunction device as a single pixel, indicating its great application prospects in future optoelectronic systems.

Optimization design of 4H–SiC-based betavoltaic battery using 3H source

Abstract: This paper describes the theoretical calculation and optimization design of the PN junction betavoltaic batteries with 4H–SiC-based energy converter and titanium tritide source. The self-absorption of radioactive isotope sources and the energy deposition distribution in the semiconductor converter are simulated using the Monte Carlo method. The relationship between doping concentrations and basic factors such as minority carrier diffusion lengths and the width of the depletion region are analyzed via the calculation formulas. Then the maximum output power density and energy conversion efficiency are calculated. The optimal thickness of the titanium tritide film is about 0.7 μm, the doping concentrations are 2.5 × 1016 cm−3, and the junction depth of PN junction is 0.1 μm. The surface recombination velocities of electron and hole are 1 × 106 cm/s, respectively. The maximum output power density and energy conversion efficiency are 0.22 μW/cm2 and 2.37%, respectively.

Mixed-Dimensional WS2/GaSb Heterojunction for High-performance p-n Diode and Junction Field-Effect Transistor

Abstract: GaSb nanowires integrated on a silicon-based substrate are of great significance for p-type field-effect transistors. In particular, due to the continued miniaturization of circuits, such as avoiding complex dielectric engineering,...

An n–n type heterojunction enabling highly efficient carrier separation in inorganic solar cells

Abstract: Carrier separation in a solar cell usually relies on the p–n junction. Here we show that an n–n type inorganic semiconductor heterojunction is also able to separate the exciton for efficient solar cell applications. The n–n type heterojunction was formed by hydrothermal deposition of Sb2(S,Se)3 and thermal evaporation of Sb2Se3. We found that the n–n junction is able to enhance the carrier separation by the formation of an electric field, reduce the interfacial recombination and generate optimized band alignment. The device based on this n–n junction shows 2.89% net efficiency improvement to 7.75% when compared with the device consisted of semiconductor absorber–metal contact. The study in the n–n type solar cell is expected to bring about more versatile materials utility, new interfacial engineering strategy and fundamental findings in the photovoltaic energy conversion process.

Modeling and optimization of GaN-based betavoltaic batteries: Comparison of p–n and p–i–n junctions

Abstract: Nuclear battery is a promising long-life power source. Selecting semiconductors with high limit efficiency and appropriate device structures effectively improves their output performance. In this work, a GaN-based (hexagonal) betavoltaic battery with [Formula: see text] source was simulated by Monte Carlo codes and COMSOL Multiphysics, and the energy converters, including p–n junction and p–i–n junction, were compared and optimized. We analyzed the effects of thickness and doping concentration of each region on the battery performances. The p-region and n-region thickness and doping concentration of the p–n junction-based battery are 0.5, 9.5 µm, 1017 cm−3, and N d = 1016 cm−3, which can achieve 3.77% conversion efficiency, and the short-circuit current density, open-circuit voltage, and maximum output power density are 0.074 µA/cm2, 2.01 V, and 0.125 µW/cm2, respectively. For the p–i–n junction-based battery, when the thickness and the doping concentration of p-region, i-region, and n-region are 0.5, 3, 6.5 µm, 1017, 1014, and 1016 cm−3, respectively, the conversion efficiency, short-circuit current density, open-circuit voltage, and maximum output power density are 5.03%, 0.099 µA/cm2, 2.0 V, and 0.167 µW/cm2, respectively. By comparing the output parameters of the two types of batteries, the results indicate that the p–i–n junction has a wider depletion region and better output performance compared with the p–n junction.

Enhanced photocatalytic activity of nZnO/n+Al:ZnO homojunction with an overlayer of Al2O3 nanoballs

Abstract: This paper reports improvement in the degradation efficiency of ZnO for the organic dye methylene blue by constructing a homojunction of nZnO and n+Al doped ZnO with an overlayer of alumina nanoballs. The thin film junction is fabricated by the simple, cost-effective two stage electrochemical method of anodization followed by electrochemical doping at room temperature. Structural, optical, morphological and electrical analyses are done to elucidate the corresponding properties of each layer as well as of the junction. The compositional depth profile is obtained by the Rutherford backscattering technique. Valence band x-ray photoelectron spectroscopy in conjunction with optical data is used for designing the schematic of the junction formation. The rectification ratio of the thin film junction is determined to be ∼102 from voltage–current data.

A highly tunable photoelectric response of graphene field-effect transistor with lateral P–N junction in channel

Abstract: This paper reports a highly tunable photoelectric response of graphene field-effect transistor (GFET) with lateral P–N junction in channel. The poly(sulfobetaine methacrylate) (PSBMA) provides strong N-type doping on graphene due to the dipole moment of pendent groups after ultraviolet annealing in high vacuum. A lateral P–N junction is introduced into the channel of the GFET by partially covering the graphene channel with PSBMA. With such P–N junction in the channel, the GFET exhibits a highly tunable photoelectric response over a wide range of exciting photon wavelength. With a lateral P–N junction in the channel, the polarity of photocurrent (I ph) of the GFET switches three times as the back-gate voltage (V BG) scan over two Dirac-point voltages. The underlying physical mechanism of photoelectric response is attributed to photovoltaic and photo-induced bolometric effect, which compete to dominating I ph at various V BG. This provides a possible strategy for designing new phototransistors or optoelectronic device in the future.

Pushing limits of photovoltaics and photodetection using radial junction nanowire devices

Abstract: Nanowire devices have long been proposed as an efficient alternative to their planar counterparts for different optoelectronic applications. Unfortunately, challenges related to the growth and characterization of doping and p-n junction formation in nanowire devices (along axial or radial axis) have significantly impeded their development. The problems are further amplified if a p-n junction has to be implemented radially. Therefore, even though radial junction devices are expected to be on par with their axial junction counterparts, there are minimal reports on high-performance radial junction nanowire optoelectronic devices. This paper summarizes our recent results on the simulation and fabrication of radial junction nanowire solar cells and photodetectors, which have shown unprecedented performance and clearly demonstrate the importance of radial junction for optoelectronic applications. Our simulation results show that the proposed radial junction device is both optically and electrically optimal for solar cell and photodetector applications, especially if the absorber quality is extremely low. The radial junction nanowire solar cells could achieve a 17.2% efficiency, whereas the unbiased radial junction photodetector could show sensitivity down to a single photon level using an absorber with a lifetime of less than 50 ps. In comparison, the axial junction planar device made using same substrate as absorber showed less than 1 % solar cell efficiency and almost no photodetection at 0 V. This study is conclusive experimental proof of the superiority of radial junction nanowire devices over their thin film or axial junction counterparts, especially when absorber lifetime is extremely low. The proposed device holds huge promise for III-V based photovoltaics and photodetectors.

Homogeneous Palladium Diselenide pn‐Junction Diodes for Reconfigurable Circuit Applications (Adv. Electron. Mater. 10/2022)

Abstract: Reconfigurable Diode Circuit Applications Palladium diselenide (PdSe2) has recently emerged as a 2D material that has strong ambipolar property and air stability for use in future nano-electronic devices. Ambipolar semiconductor could easily accumulate the electron or hole carriers at the channel material by gate field modulation. Kimoon Lee, Young Tack Lee, and co-workers in article number 2101282 present the PdSe2-based split-gate field-effect transistor which can be formed as a switchable diode (like a one way road) and single-inversion AND (SAND) logic gate as well.

Numerical Investigation on Hole-Injection Characteristics of NiO/SiC Heterojunction

Abstract: Numerical investigation on hole-injection characteristics of NiO/SiC heterojunction is carried out in this paper. Theory analysis and numerical simulation both indicate the excellent hole-injection characteristic of p-NiO/n-SiC heterojunction. The pn junction diode and pnp phototransistor are constructed and simulated to evaluate hole-injection characteristics p-NiO/n-SiC heterojunction. The results indicate that the p-NiO/n-SiC heterojunction shows great potential advantage in enhancing current gain of pnp phototransistor. By using NiO/SiC heterojunction as the emitter junction, the current gain of SiC based pnp phototransistor can be increased by about 96.3 times.

Simulation of Silicon Surface Barrier Detector with PN Junction Guard Rings to Improve the Breakdown Voltage

Abstract: Silicon surface barrier detectors (SSBDs) are normally used to detect high-energy particles due to their excellent properties. For better charge collection efficiency (CCE), the SSBD device should be operated at higher reverse voltages, but this can lead to device breakdown. Therefore, we used a PN junction as a guard ring to increase the breakdown voltage of the SSBD. The structures of two SSBD devices are drawn and simulated in this work. Compared with a conventional SSBD (c-SSBD), the use of a PN junction as a guard ring for an SSBD (Hybrid-SSBD) achieves higher breakdown voltages, of over 1500 V under reverse bias. This means that Hybrid-SSBD devices can operate at higher reverse voltages for better charge collection efficiency (CCE) to detect high-energy particles. Then, we simulated the different structure parameters of the Hybrid-SSBD guard rings. Among them, the doping depth and gap width of the guard ring (between the innermost guard ring and the active area) have a greater impact on the breakdown voltage. Finally, for Hybrid-SSBD devices, the optimal characteristics of the guard ring were 1 × 1019 cm−3 doping concentration, 1 μm doping depth, and innermost guard ring width and gap width of 5 μm and 3 μm, respectively.