Barrier Diodes Research Articles

Investigating the Role of Band Offset on the Property and Operation of the Potential Well Barrier Diodes

The impact of grading the GaAs/AlGaAs interface on carrier dynamics in a potential well barrier (PWB) diode has been explored and demonstrated in this paper. Three heterostructures in the GaAs/AlGaAs system namely GaAs/Al0.2Ga0.8As, GaAs/Al0.3Ga0.7As, and GaAs/Al0.4Ga0.6As with corresponding band offsets of 0.10, 0.25, and 0.30 eV, respectively, are investigated using the drift‐diffusion (DD) and Monte Carlo (MC) models. The behavior of the diodes with different band offsets are compared in terms of mean electron velocity, mean electron energy, and density of charge along the intrinsic regions and in the potential well. The MC simulation model enables the effects of space‐charge injection and carrier heating, which are not included in previous study of these structures, be treated quantitatively. Significant differences exist in the behavior of the three heterojunctions as this impacts the curvature coefficient and ideality factor of the diode. Both the ideality factor and curvature coefficient reflect the magnitude of band offset of the heterojunctions (interface).

Детекторы на основе низкобарьерных диодов Мотта и их характеристики в диапазоне 150-250 GHz

AbstractThe characteristics of millimeter-wavelength detectors based on planar Mott diodes with near-surface δ-doping operating without a constant bias are discussed. These detectors have a volt–watt sensitivity of ~1000 V/W with NEP ~ 10 pW/Hz^1/2 in the 150–250 GHz range. The obtained estimates reveal the possibility of an additional order-of-magnitude enhancement of the performance characteristics of detectors with smaller areas of the diode barrier contact.

Synthesis and characterization of ruthenium-doped CdO nanoparticle and its n-RuCdO/p-Si junction diode application

In the present work, Ru doped CdO nanoparticles were prepared with different doping concentrations by microwave irradiation technique for P-N junction diode application. The effect of doping agent on the CdO nanoparticles were investigated via various techniques such as XRD, FT-IR, SEM, EDS, TEM, UV-DRS, and XPS techniques. The XRD results confirmed that the prepared nanoparticles have cubic structure with preferred orientation along (111) direction and this plane crystallite size is in the range 18.7 to 16.8 nm. SEM and TEM morphologies reveal the CdO nanoparticles are strongly influenced by the doping of Ru and grain size reduces with increasing Ru doping levels. UV–vis DRS results depict the optical band gap value decreases with increase of Ru content. FTIR, EDS and XPS results are good evidence for formation of pure and Ru doped CdO. The DC electrical conductivity result shows that the 5 wt% Ru doping level have a maximum conductivity compared to pure CdO. The n-RuCdO/p-Si diode parameters (ideality factor (n) and barrier height (Фb)) were studied using J-V method. The photocurrent and dark current behaviors of the fabricated n-RuCdO/p-Si diode show good photoconducting response.

Impact of Ce content on cubic phase cerium–cadmium oxide (Ce–CdO) nanoparticles and its n-CeCdO/p-Si junction diodes

Microwave irradiation method was adopted to synthesize Ce doped CdO nanoparticles. The n-CeCdO/p-Si junction diode was fabricated and it’s parameters have been studied at different doping concentrations (0, 5, 10, and 15 wt%) of Ce. The Ce doping effect was analyzed by various characterization techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photo electron spectroscopy (XPS), ultra violet–visible spectroscopy (UV–Vis) and DC conductivity (I–V) studies. From XRD analysis, the Ce–CdO nanoparticles depicted a crystalline nature and showed the cubic phase. The crystallite size of the samples varied from 18.72 to 14.68 nm. TEM images reveal that the Ce–CdO nanoparticles have nail-like structure. The presence of the elements Ce, Cd and O were confirmed by EDX and XPS studies. The optical bandgap value decreases with the increasing doping concentration and the minimum band gap energy of 2.70 eV is obtained for 15 wt% Ce–CdO sample. I–V curve represents the semiconducting behavior of Ce–CdO nanoparticles. Variation of current in Ce doped CdO nanoparticles exhibits linear response to applied voltage. The diode behavior was studied under darkness and illumination environment. The major diode parameters, ideality factor and barrier height of n-CeCdO/p-Si junction diode were examined using J–V method.

Characterization of TlInS1.8Se0.2 as advanced functional crystals

In this work, selenium doped TlInS1.8Se0.2 crystals are used to fabricate multifunctional devices that can handle more than one duty at a time. After revealing the morphological, compositional, structural and optical properties of the doped crystal, it is sandwiched between Ag and carbon metals. The crystals are characterized by means of ultraviolet-visible light spectrophotometry, impedance spectroscopy and illumination dependent current-voltage characteristics techniques. While the optical spectroscopy allowed determining the energy band gap of the crystals as well as the optical conductivity in the terahertz frequency domain, the impedance spectroscopy allowed identifying the conductance and reflectance spectra in the gigahertz frequency domain. The two techniques reveal promising characteristics presented by optical switching at 2.20 eV and band pass filtering properties in mega/gigahertz frequency domains. On the other hand, the analysis of the current (I)- voltage (V) characteristics which are recorded in the dark and under photoexcitation of unfiltered tungsten light in the light power range of 25–130 mW, revealed light intensity dependent rectifying properties. Particularly, the modeling of the experimental I-V curves in accordance with the Richardson Schottky and Chueng's theoretical approaches have shown that the Schottky diode ideality factor, series resistance and barrier height decreases with increasing light power. Such behavior indicates wide tunability of the device when used as photosensors. With the features presented by small size, photosensitivity, gigahertz/terahertz spectral responses, the device can be promising element for use in visible light and microwave communications.

Effect of seed layer thickness on optoelectronic properties of ZnO-NRs/p-Si photodiodes

In this work, the effect of seed layer thickness on the optical and electrical properties of a photodiode based on zinc oxide nanorods (ZnO-NRs)/p-Si was studied. ZnO thin films of different thicknesses were deposited on a p-type single crystalline silicon substrate by the spin-coating method, and then well-aligned ZnO-NRs were grown on a seed layer by the hydrothermal method. The seed layer thickness increment enhanced the NR lengths and improved their crystallinity. Longer NRs showed lower reflectance and band gap measurements were carried out using the reflectance spectrum. The current-voltage (I–V) measurements were performed under dark and UV illumination to study the photo-detection properties of the ZnO-NRs/p-Si photodiode with different seed layer thicknesses. The diode ideality factor, barrier height, saturation current and series, and shunt resistance were determined by the dark current-voltage measurements. The dark current-voltage characteristics demonstrated an excellent rectifying behavior, and the seed layer thickness increment decreased the diode ideality factor. It was shown that the current-voltage characteristics of the fabricated devices with different seed thicknesses under UV light illumination had good sensitivities.

Compact modeling of SiC Schottky barrier diode and its extension to junction barrier Schottky diode

A compact model applicable for both Schottky barrier diode (SBD) and junction barrier Schottky diode (JBS) structures is developed. The SBD model considers the current due to thermionic emission in the metal/semiconductor junction together with the resistance of the lightly doped drift layer. Extension of the SBD model to JBS is accomplished by modeling the distributed resistance induced by the p+ implant developed for minimizing the leakage current at reverse bias. Only the geometrical features of the p+ implant are necessary to model the distributed resistance. Reproduction of 4H-SiC SBD and JBS current–voltage characteristics with the developed compact model are validated against two-dimensional (2D) device-simulation results as well as measurements at different temperatures.

Comparative Study of Heterostructure Barrier Diodes in the GaAs/AlGaAs System

A comparative study of the electron transport property and operation of the Potential Well Barrier (PWB) diode and Planar-doped Potential-well Barrier (PPB) diode has been carried out in this study. Both diodes are heterostructures in GaAs/AlGaAs system with similarities in layer design though, with a sheet charge inserted close to the well of the PPB diode. A drift-diffusion and Monte Carlo simulation models were used throughout the study to examine the behavior of electrons in terms of the electric field distribution across the diodes, electron velocities, electron energy and densities. Results of simulation has shown how the electric field varies in the left and right intrinsic regions of the device and the effect of the field on velocity. The I-V characteristics of the experimental and simulation results have shown a good agreement in the two diodes though, with little adjustment of about ± 2.5% to design parameters in order to obtain a good fit with experimental results. The I-V characteristics of the diodes reveal that the PPB diode turns on at a higher voltage than the PWB diode though, with a better asymmetry in the reverse bias operation. This is because the sheet charge in the PPB diode produces additional charge and together with the charge in the well, presents a higher potential barrier than the PWB diode whose barrier is determined by the charge in the well only. The diodes demonstrate promising RF behavior with voltage responsivity of 10900V/W and 6400V/W at 10GH for the PPB and PWB diodes respectively.

Effects induced by high and low intensity laser plasma on SiC Schottky detectors

Silicon-Carbide detectors are extensively employed as diagnostic devices in laser-generated plasma, allowing the simultaneous detection of photons, electrons and ions, when used in time-of-flight configuration. The plasma generated by high intensity laser (1016 W/cm2) producing high energy ions was characterized by SiC detector with a continuous front-electrode, and a very thick active depth, while SiC detector with an Interdigit front-electrode was used to measure the low energy ions of plasma generated by low intensity laser (1010 W/cm2). Information about ion energy, number of charge states, plasma temperature can be accurately obtained. However, laser exposure induces the formation of surface and bulk defects whose concentration increases with increasing the time to plasma exposure. The surface defects consist of clusters with a main size of the order of some microns and they modify the diode barrier height and the efficiency of the detector as checked by alpha spectrometry. The bulk defects, due to the energy loss of detected ions, strongly affect the electrical properties of the device, inducing a relevant increase of the leakage (reverse) current and decrease the forward current related to a deactivation of the dopant in the active detector region.

Simulation study of high‐reverse blocking AlGaN/GaN power rectifier with an integrated lateral composite buffer diode

In this study, a novel AlGaN/GaN power rectifier with an integrated lateral composite buffer diode (IBD-Rectifier) for reverse blocking capability improvement is proposed and investigated by Sentaurus simulations (this paper includes only simulated data and no real experimental result). AlGaN buffer layer under the anode is adopted to realise great high reverse blocking capability. A minimum turn-on voltage of 0.6 V and a maximum breakdown voltage (BV) >1.3 kV are simultaneously obtained in the IBD-Rectifier, resulting in a high Baliga's figure of merits BV 2/R on,sp (R on,sp is specific-on resistance) of ∼3000 MW/cm2. In comparison with MIS-gated hybrid anode diode and conventional schottky barrier diode, the IBD-Rectifier delivers an excellent theoretical method to achieve superior performances in high-efficiency GaN power applications.

GaAs/AlGaAs potential well barrier diodes: Novel diode for detector and mixer applications

Heterostructure potential well barrier (PWB) diodes in GaAs/AlGaAs system operating in a similar way to Planar Doped Barrier (PDB) diodes, though exploiting a potential well to trap charge, rather than a fixed doping spike have recently been realized and reported in the literature. This paper analyses the complex operation of these devices and determines the sensitivity of the current–voltage (I–V) characteristics to various design parameters. The PWB diode displays a significant temperature sensitivity, opposite in nature to PDB temperature dependence, and this suggests the possibility of temperature stabilised hybrid designs. The active bias dependence nature of charge within the well is found to have a significant effect on the device and impacts the ideality factor, which is more bias dependent than other comparable devices such as PDBs. However, the same mechanism offers the prospect of improvement in the current asymmetry and this effect can be greatly improved upon by changing the design and shape of the potential well.

Deposition of CZTSe thin films and illumination effects on the device properties of Ag/n-Si/p-CZTSe/In heterostructure

Abstract Characterization of Cu 2 ZnSnSe 4 (CZTSe) thin films deposited by thermal evaporation sequentially from the pure elemental sources and in-situ post annealing was carried out at 400 C under Se evaporation atmosphere. Another annealing process was applied in nitrogen atmosphere at 450 °C to get polycrystalline monophase CZTSe film structure. XRD analysis together with Raman spectroscopy was used to determine the structural properties. Spectral optical absorption coefficient evaluated from transmission data showed the band gap value of 1.49 eV for annealed film. Electrical measurements indicated that CZTSe thin films have p-type semiconductor behavior with the carrier density and mobility values of 10 −19 cm −3 and 0.70 cm 2 /(V.s). Illumination effects on the device properties of Ag/n-Si/p-CZTSe/In heterostructure were investigated by analyzing current-voltage(I-V) and frequency dependent capacitance-voltage(C-V) data. Under the illumination, Ag/n-Si/p-CZTSe/In heterostructure showed photodiode behavior having V oc value of 100 mV and I sc value of 27.5 μA. With the illumination, series resistances (R s ), diode ideality factor (n) and barrier height (Φ b ) decreased and shunt resistance (R sh ) increased. Capacitance value at lower frequency decreased due to the illumination effect.

Epitaxial Fe on free-standing GaAs nanowires

Epitaxial Fe contacts have been fabricated onto the top half of free-standing, Te-doped GaAs nanowires (NWs) via electrodeposition. Electrical isolation from the substrate via a polymeric layer enabled the measurement of electrical transport through individual wires. Using a fixed probe within a scanning electron microscope, an average metal-semiconductor diode barrier height of 0.69 ± 0.03 eV (ideality factor 1.48 ± 0.02) was found.

Fabrication and electrical characterization of p-ZnIn2Se4/n-Si heterojunction diode structure

Semiconducting thin films of p-ZnIn2Se4 were deposited on a crystalline n-silicon (Si) substrate by a flash evaporation technique. A heterojunction diode comprising of Au/p-ZnIn2Se4/n-Si/Al structure was fabricated. The heterojunction was subjected to current (I)–voltage (V) and capacitance (C)–voltage (V) characterization. The p-ZnIn2Se4/n-Si heterojunction showed behaviour typical of a p-n junction diode. The heterojunction diode ideality factor, rectification ratio, barrier height and carrier concentration were determined from the I–V and C–V measurements. At lower applied voltages, the electrical conduction was found to take place by thermionic emission whereas at higher voltages, a space charge-limited conduction mechanism was observed. A theoretical energy band diagram was constructed for the fabricated p-ZnIn2Se4/n-Si heterojunction on the basis of Anderson’s model. The photovoltaic behaviour of the fabricated heterojunction was also investigated and the results were reported.

Surface coating of ZnO nanoparticles onto 6H-SiC(0001): Temperature-dependent rectifying behavior

This work reports on the detailed analysis of the temperature-dependent electrical parameters of the ZnO/6H-SiC barrier diodes. The effect of light on the diode current was also examined. It was found that the diode showed low sensitivity to light. No remarkable change in diode characteristics were observed at room temperature. The structure has a high rectification ratio of 1.096×104 at ±2V with ideality factor of 2.46 at room temperature. The rectification ratio (RR) decreases with increasing temperature, as agree to other heterojunction structures. Some diode parameters such as zero-bias barrier height and ideality factor as temperature-dependent were calculated on the basis of the thermionic emission (TE) theory, by considering a Gaussian distribution (GD).

Cu2ZnSnS4 Films Grown on Flexible Substrates by Dip Coating Using a Methanol-Based Solution: Electronic Properties and Devices

The deposition of device quality Cu2ZnSnS4 (CZTS) films on flexible substrates by simple and cost-effective techniques is of great interest for solar cell applications. In this work, CZTS films were deposited on lightweight flexible substrates by successive dip coating using a nontoxic, methanol-based precursor solution. The films were characterized by x-ray diffraction, energy dispersive x-ray analysis, scanning electron microscopy, atomic force microscopy, optical transmission spectroscopy, photocurrent spectroscopy and admittance spectroscopy. The films prepared by this technique have direct band gaps of 1.5–1.6 eV, a p-type resistivity of ~1 Ω cm, an acceptor concentration of ~1017 cm−3 and structural and morphological properties that are suitable for device applications. Four defect levels with activation energies of 5.4 meV, 18.8 meV, 70 meV, and 221 meV were detected in the films. All but the shallowest defect level were attributed to the native VCu, CuZn, and VSn acceptor-type defects. For further assessment of the films, Schottky barrier and heterojunction diodes were fabricated and characterized. The results signified that the device quality CZTS films can be synthesized by the dip-coating method used in this study.

A new type photodiode: p-Si/GaN pn junction in series with GaN/Ag Schottky diode

Large quantities of gallium nitride (GaN) nanoparticles were successfully synthesized via a facile sol-gel approach. X-ray diffraction analysis confirms the polycrystalline nature of the GaN with hexagonal wurtzite structure and lattice constants a = 0.3189 nm and c = 0.5185 nm. The morphology of the GaN film was investigated by field emission scanning electron microscopy. The obtained results indicate that the synthesized GaN nanorods have an average length of around 60 nm and an average diameter of 23 nm. The optical band gap of the GaN film was obtained to be 3.4 eV. The gallium nitride/p-Si Schottky diode was fabricated by thermal evaporation technique on p-silicon. The current–voltage (I–V) characteristics of the fabricated diode was tested under dark and various light intensities. T The diode ideality factor and barrier height were computed using forward bias I–V characteristics of the diode and are found to be 1.66 and 0.53 eV, respectively. The obtained results suggest that the film preparation by sol gel method is fast and simple to prepare GaN based photodiode by according to metal organic deposition methods.

Measuring size dependent electrical properties from nanoneedle structures: Pt/ZnO Schottky diodes

This work reports the fabrication and testing of nanoneedle devices with well-defined interfaces that are amenable to a variety of structural and electrical characterization, including transmission electron microscopy. Single Pt/ZnO nanoneedle Schottky diodes were fabricated by a top down method using a combination of electro-polishing, sputtering, and focused ion beam milling. The resulting structures contained nanoscale planar heterojunctions with low ideality factors, the dimensions of which were tuned to study size-dependent electrical properties. The diameter dependence of the Pt/ZnO diode barrier height is explained by a joule heating effect and/or electronic inhomogeneity in the Pt/ZnO contact area.

Low temperature dependent ferroelectric resistive switching in epitaxial BiFeO3 films

The ferroelectric switchable diode induced resistive switching behavior at low temperature has been investigated in the epitaxial BiFeO3 (BFO) thin films. The switchable diode can be tuned using a higher voltage at low temperatures. The diode barrier is determined to be ∼0.55 eV at the interface between BFO and electrode. The resistive switchable barrier with respect to the ferroelectric domain switching has been systematically characterized at various low temperatures. The temperature dependent conduction and leakage mechanisms have also been identified. These results can advance our understanding of resistive switching based on ferroelectric switchable diode at low working temperatures and potentially extend the applications of memristor to a larger temperature scale.

Barrier height estimation of asymmetric metal-insulator-metal tunneling diodes

A method is developed to estimate barrier heights of an asymmetric metal-insulator-metal (MIM) diode exhibiting Fowler-Nordheim tunneling. The method requires determination of slopes and intercepts of a log(|I(V+Δϕ)2|) versus 1V+Δϕ plot rather than a log(|I(V)2|) versus 1V plot (i.e., a conventional Fowler-Nordheim plot), where I, V, and Δϕ refer to tunneling current, applied voltage, and the difference in barrier heights, respectively. As the value of Δϕ directly impacts the applied electric field magnitude, it is a critical component in barrier height determination from a current-voltage measurement. Conventional Fowler-Nordheim plot analysis does not employ Δϕ, which compromises the accuracy of barrier height estimation when Δϕ≠0. Using the described method, the barrier heights of a ZrCuNiAl/Al2O3/Al MIM diode are estimated to be 1.75 V and 1.07 V, respectively, and the Al2O3 tunneling effective mass is estimated to be 0.47. Additional MIM diodes are analyzed to show that the accuracy of MIM diode barrier height and effective mass estimates is highly sensitive to contamination and/or energy imparted during the deposition of the upper electrode.