Pn Junction Diode Research Articles

Seamless MoTe2 Homojunction PIN Diode toward 1300 nm Short‐Wave Infrared Detection

AbstractHomojunction PN and PIN diodes based on 2D transition metal dichalcogenide (TMD) MoTe2 are reported in this work. Up to date, for PN junction diodes, type II‐based heterojunction diodes are mainly seen in report, but homojunction PN diodes using 2D‐layered materials are still rare although they enable seamless integration. Recently, hydrogen (H)‐doped n‐type MoTe2, achieved via atomic layer deposition (ALD) on top of a p‐type MoTe2 surface, was reported. Consequently, a lateral homojunction PN diode was realized by H‐doping. In fact, MoTe2‐based devices with a thickness on the order of nanometers can be applied for short‐wave infrared (SWIR) detection in the range of ≈1300 nm, a wavelength that Si‐based devices cannot properly address. Here, a seamless MoTe2 homojunction PIN diode is demonstrated, achieving the detection of visible to 1300 nm SWIR photons. This thin MoTe2 initially forms a PN junction by selective H‐doping, but a PIN diode is even obtained using two split gates. Compared to the PN diode mode, the PIN mode greatly enhances the photoresponse in the visible to 1300 nm wavelength range because of the increased built‐in electric field. The Franz–Keldysh effect is regarded strongly responsible for the effective absorption of 1300 nm SWIR photons in MoTe2. It is anticipated that this development may support Si photodetectors for integration on Si devices.

Addressing the sneak-path problem in crossbar RRAM devices using memristor-based one Schottky diode-one resistor array

Abstract Resistive random access memories (RRAMs) are favorable contenders in the race towards future technologies. Moreover, the desirable properties of memristor-based RRAM devices make them very good competitors in this field. The sneak paths problem poses one of the main difficulties in the construction of crossbar memory devices. This problem can be effectively suppressed by applying the 1diode-1resistor (1D1R) design structure. The Schottky diode has many advantages compared to the PN junction diode. The low-power (∼1 µW) ZnO active-layered thin-film (60 nm thick) one Schottky diode-one memristor device fabricated in this study included a top Ag electrode and a bottom Al electrode. The material makeup of the device was confirmed via energy dispersive X-ray spectroscopy (EDAX). The memristive and Schottky diode characteristics of the Ag/ZnO/Al device were resolved by measuring the time-dependent voltage/current. The characteristic pinched hysteresis memristive loops were observed at the first quadrant of the current-voltage plane, whereas the diode curves were seen at the third quadrant. Using the current-voltage curves, the height of the Schottky barrier, ideality factor and threshold voltage of the Schottky diode were found to be 0.68 eV, 3.75 and 0.49 V, respectively. After physical implementation and characterization of the one diode-one memristor device, its anti-crosstalk characteristics were investigated. Taking into account the 10% read margin, the maximum crossbar size was found to be 87.

Ecofriendly Mg2Si-based photodiode for short-wavelength IR sensing

N-type Mg2Si single crystal ingot has been successfully grown by the Vertical Bridgman technique. The Hall Effect measurement at RT revealed a moderate Hall mobility (~ 446 cm2/Vs), electrical resistivity (~ 1.4 Ω. cm) and carrier density (~1016 cm−3) for the grown crystal. The J-V characteristics of the fabricated Au/n-Mg2Si Schottky junction and Au/Ag-doped-p-type-Mg2Si/n-type-Mg2Si/Ag pn-junction diode showed better diode behavior with higher rectifying ratio in comparison with the same reported junctions. Analysis of the experimental forward J-V characteristics of our fabricated diodes based on the thermionic emission (TE) model demonstrated that our Schottky and pn-junction Mg2Si diode exhibited much lower series resistance in comparison with the survey data, confirming that precise polishing of Mg2Si surfaces with an oil-based diamond greatly improved the contact with the evaporated metal, enabling lower interfacial resistance between the evaporated metal and Mg2Si wafer. In addition, the manufactured Mg2Si pn-junction photodiode showed a clear photoresponsivity in the wavelength range from 0.95 to 1.8 µm with a maximum zero-biased photoresponse of 14 mA/W at 1.4 µm and a photon energy threshold of approximately 0.66 eV. These results indicate that our diode is promising to detect the SWIR light in the wavelength range from 0.95 to 1.8 µm.

Preparation and some properties of Mg2Si0.53Ge0.47 single crystal and Mg2Si0.53Ge0.47 pn-junction diode

This paper reports the results on fabrication methodology and photoresponse characteristics of Mg2Si0.53Ge0.47 pn-junction photodiode. At first, we have grown a Mg2Si0.53Ge0.47 single crystal with the Vertical Bridgman growth process. The grown crystal was characterized structurally and electrically by XRD, Laue, and Hall Effect measurements. XRD revealed the single-phase composition, Mg2Si0.53Ge0.47, of the grown crystal ingot. The clear Laue symmetrical diffraction pattern showed the single crystalline nature of the grown crystal. The Hall Effect measurement revealed the n-type conduction and the moderate Hall mobility (258 cm2/Vs), electrical resistivity (6.03E-02 Ω. cm), and carrier density (4.02E+17 cm-3) of the grown crystal. Such carrier density is low enough to allow depletion region formation in case of pn-junction diodes. In that sense, we have made up for the first time Mg2Si0.53Ge0.47 pn-junction photodiode by thermal diffusion of a thin Ag layer into n-Mg2Si0.53Ge0.47 substrate. The fabricated diode had an obvious rectification behavior and demonstrated a clear zero-biased photoresponse in the wavelength range from 0.95 to 1.85 μm, indicating its prominence for IR sensation in that wavelength domain.

All carbon materials pn diode

Semiconductor pn junctions are elementary building blocks of many electronic devices such as transistors, solar cells, photodetectors, and integrated circuits. Due to the absence of an energy bandgap and massless Dirac-like behaviour of charge carriers, graphene pn junction with electrical current rectification characteristics is hardly achieved. Here we show a graphene pn junction diode can be made exclusively from carbon materials by laminating two layers of positively and negatively charged graphene oxides. As the interdiffusion of oppositely charged mobile counterions, a built-in potential is created to rectify the current by changing the tunnelling probability of electrons across the junction. This graphene diode is semi-transparent, can perform simple logic operations, and since it has carbon nanotubes electrodes, we demonstrate an all carbon materials pn diode. We expect this graphene diode will expand material choices and provide functionalities (e.g. grafting recognition units on graphene oxides) beyond that of traditional semiconductor pn junctions.

Electrically controllable position-controlled color centers created in SiC pn junction diode by proton beam writing

Abstract

Voltage oscillations during surge pulses induced by self-extinguishing non-destructive second breakdown in pn-junction diodes

PN-junction diodes with different breakdown voltages have been subjected to surge pulses per the standard IEC 61000-4-5 and their transient behaviour has been studied. For medium breakdown voltages (20–40 V) at high surge currents large transient oscillations in the voltage drop across the diodes are observed. After such an event, the devices are still operational. 3D electro-thermal TCAD simulations have been done to understand the phenomenon. A comparison between measurement and simulation reveals that the periodic voltage drop is caused by non-destructive second breakdown.

Transient model for electrical activation of aluminium and phosphorus-implanted silicon carbide

The development of novel electron devices requires a continuous support by process and device simulations in order to improve electrical properties and reduce production costs. However, an accurate description of the electrical properties of impurities in silicon carbide – a key wide bandgap semiconductor for power devices – is currently not available, which significantly limits the predictability of critical fabrication processes. Here, we introduce a transient model for electrical activation of implanted aluminium and phosphorus in silicon carbide to fill this gap. Our results suggest differences between acceptor- and donor-type dopants including activation speed, saturation limit, and activation regions. We predict acceptor and donor concentrations according to the various annealing times, temperatures, and doping concentrations. The results are used for the fabrication of PN-junction diodes, which are characterized and compared with the experimental findings. Finally, we predict improvements of various annealing steps, i.e., increased active concentration, increased carrier concentration, and decreased sheet resistance, and perform a comprehensive comparison with experimental data to evaluate the proposed model.

Modeling and Simulation of Electrical Activation of Acceptor-Type Dopants in Silicon Carbide

We propose an empirical model to predict electrical activation ratios of aluminium- and boron-implanted silicon carbide with respect to various annealing temperatures. The obtained parameters and model extensions are implemented into Silvaco’s Victory Process simulator to enable accurate predictions of post-implantation process steps. The thus augmented simulator is used for numerous simulations to evaluate the activation behavior of p-type dopants as well as for the full process simulation of a pn-junction SiC diode to extract the carrier and acceptor depth profiles and compare the results with experimental findings.

Hybrid PN Diode and CMOS Inverters Composed of MoTe2 Nanosheet-Amorphous in-Ga-Zn-O Thin Film

We report a hybrid material system which couples a dry-transfer-processed p-type MoTe2 nanosheet and a conventional photolithography-patterned n-type amorphous InGaZnO (IGZO) thin-film. The PN junction diode shows a good ideality factor of 1.57 and a high ON/OFF rectification ratio of ∼3 × 104. Under illumination, our PN diode shows somewhat stable only responding to high-energy photons of blue and ultraviolet. Our CMOS inverter composed of p-MoTe2 bottom-gate field-effect transistor and n-IGZO top-gate field-effect transistors. Our 2D nanosheet – oxide thin film CMOS inverter shows high voltage gains as high as ~40 at 5 V, low power consumption less than ~ a few nW at 1 V, and ~200 μs switching speed. Both hybrid PN junction diode and complementary (CMOS) inverters are realized by such novel hybrid material system that now opens any further possibilities toward practical applications of 2D nanosheets combined with existing technologies. Figure 1

(Invited) Mechanistic Details of Protonic Solar Cells Formed Via Covalent Modification of Passive Ion-Exchange Membranes with Photoacid Dye Molecules

Many electrochemical technologies require ion-conducting polymer electrolytes. These polymers are passive in that electric bias across them drives ion migration in the thermodynamically favored direction.1 Recently, my group engineered two important features into ion-selective polymer membranes to introduce the active function of photovoltaic action and demonstration of an ionic solar cell. These features were covalent bonding of photoacid dyes to the polymers such that absorption of visible light liberated protons, and polymers with charge-selective contacts to facilitate separation and collection of H+ and OH–.2,3 The most effective designs join a monopolar cation-selective polymer to a monopolar anion-selective polymer to form a bipolar membrane whose electrostatics and thermodynamics mimic those of a rectifying semiconductor pn-junction diode. Illumination from either side of a photoacid-modified bipolar membrane resulted in photoinduced deprotonation of photoacids followed by charge separation in a direction dictated by the built-in electrostatic asymmetry in the polymers. Performance optimization is underway to increase the state-of-the-art voltage to beyond 120 mV and state-of-the-art current to beyond 100 μA/cm2. The aim of these efforts is to gain a strong fundamental understanding of dye and material function using a variety of techniques. These include electrochemical impedance spectroscopy to quantify properties of capacitive space-charge regions; pulsed-laser spectroscopy to elucidate light-driven mechanisms of ion transfer and transport; finite-element numerical modeling to understand photoacid dye kinetics and drift–diffusion generation–recombination membrane physics; and optical, electron, and ion microscopies to elucidate materials morphology and function. Collectively, these photo-responsive polymers represent a new class of materials that use light to trigger changes in local pH and/or electrostatic potential. These local changes can be used to affect macroscopic processes such as direct solar desalination of salt water or triggering redox chemistry or chemical catalysis. Acknowledgment: This work is supported by a Moore Inventor Fellowship from the Gordon & Betty Moore Foundation, under Grant #5641.

Fundamental Limitations of Wide-Bandgap Semiconductors for Light-Emitting Diodes

Fundamental limitations of wide-bandgap semiconductor devices are caused by systematic trends of the electron and hole effective mass, dopant ionization energy, and carrier drift mobility as the semiconductor’s bandgap energy increases. We show that when transitioning from narrow-bandgap to wide-bandgap semiconductors the transport properties of charge carriers in pn junctions become increasingly asymmetric and characterized by poor p-type transport. As a result, the demonstration of viable devices based on bipolar carrier transport, such as pn junction diodes, bipolar transistors, light-emitting diodes (LEDs), and lasers, becomes increasingly difficult or even impossible as the bandgap energy increases. A systematic analysis of the efficiency droop in LEDs is conducted for room temperature and cryogenic temperature and for emission wavelengths ranging from the infrared, through the visible (red and blue), to the deep-ultraviolet part of the spectrum. We find that the efficiency droop generally increases ...

Flexible silicon-based alpha-particle detector

The detection of alpha particles in the field can be challenging due to their short range in air of often only a few centimeters or less. This short range is a particular issue for measuring radiation inside contaminated pipework in the nuclear industry, for which there is currently no simple method available without cutting the pipes open. Here, we propose an approach for low cost, rapid, and safe identification of internally contaminated pipework based on a flexible 30 × 10 mm2 sheet of 50 μm thin crystalline silicon. Following established fabrication steps of pn-junction diodes, we have constructed a device with a signal-to-noise ratio of >20 in response to 5.5 MeV alpha-particles using a bespoke amplifier circuit. As flexible detectors may readily conform to a curved surface and are able to adapt to the curvature of a given pipeline, our prototype device stands out as a viable solution for nuclear decommissioning and related applications.

P-NiO/n+-Si single heterostructure for one diode-one resistor memory applications

One diode-one resistor (1D1R) memory is one of effective architectures to suppress the crosstalk interference of crossbar network. The conventional 1D1R device usually consists of a stack of sandwich-structure memory and pn junction diode. Herein, we demonstrated a 1D1R device based on a single-stacked p-NiO/n+-Si heterostructure, and its structure and fabrication process are greatly simplified compared with those of multilayer 1D1R devices. Studies on electrical transport properties reveal that the p-type NiO film not only serves as a resistive-switching layer, but also combines with n-type Si to form a pn heterojunction diode. Due to the existence of the built-in electric field, it can neutralize the applied external electric field and the nanoscale conducting filaments (CFs) are only confined to the outside of depletion region of NiO/Si pn junction. Thus, the formation of CFs does not degrade the diode quality, which allows the coexistence of resistive-switching and rectifying behaviors.

Coupling Two-Dimensional MoTe2 and InGaZnO Thin-Film Materials for Hybrid PN Junction and CMOS Inverters.

We report the fabrication of hybrid PN junction diode and complementary (CMOS) inverters, where 2D p-type MoTe2 and n-type thin film InGaZnO (IGZO) are coupled for each device process. IGZO thin film was initially patterned by conventional photolithography either for n-type material in a PN diode or for n-channel of top-gate field-effect transistors (FET) in CMOS inverter. The hybrid PN junction diode shows a good ideality factor of 1.57 and quite a high ON/OFF rectification ratio of ∼3 × 104. Under photons, our hybrid PN diode appeared somewhat stable only responding to high-energy photons of blue and ultraviolet. Our 2D nanosheet-oxide film hybrid CMOS inverter exhibits voltage gains as high as ∼40 at 5 V, low power consumption less than around a few nW at 1 V, and ∼200 μs switching dynamics.

Designing an efficient rectifying cut-wire metasurface for electromagnetic energy harvesting

Electromagnetic energy harvesting, i.e., capturing energy from ambient microwave signals, may become an essential part in extending the battery lifetime of wearable devices. Here, we present a design of a microwave energy harvester based on a cut-wire metasurface with an integrated PN junction diode. The cut wire with a quasistatic electric-dipole moment is designed to have a resonance at 6.75 GHz, leading to a substantial cross-section for absorption. The external microwaves create a unidirectional current through the rectifying action of the integrated diode. Using an electrical-circuit model, we design the operating frequency and the resistive load of the cut wire. Subsequently, by optimizing our design using full-wave numerical simulations, we obtain an energy harvesting efficiency of 50% for incident power densities in agreement with the typical power density of WiFi signals. Finally, we study the effect of connecting adjacent unit cells of the metasurface in parallel by a thin highly inductive wire and we demonstrate that this allows for the collection of current from all individual cells, while the microwave resonance of the unit cell is not significantly altered, thus solving the wiring problem that arises in many nonlinear metamaterials.

Observation of pn-junction depth in Mg<sub>2</sub>Si diodes fabricated by short period thermal annealing

We have fabricated Mg2Si pn-junction diodes by short-period (30 s and 1 min) annealing between 400 and 480 °C and evaluated the pn-junction depth by EBIC and VC observations. The pn-junction depth of approximately 6 and 30 µm was formed for the annealing conditions of 400 °C, 30 s and 480 °C, 1 min, respectively. By comparing the Ag depth profiles determined by SIMS, we estimated the activation ratio at the pn-junction of approximately 8 and 10% for annealing at 450 and 480 °C, respectively. All diodes showed clear rectifying behavior in J–V characteristic and the spectral photosensitivity below approximately 1.8 µm under zero bias condition.

Increased doping depth of Al in wet-chemical laser doping of 4H-SiC by expanding laser pulse

Al is doped into 4H-SiC by irradiating pulsed KrF excimer laser to 4H-SiC immersed in AlCl3 aqueous solution. Impact on doping depth of the use of expanded laser-pulse width is investigated. Expanded laser pulse is produced by splitting and recombining the laser beam with mirrors. The laser pulse width was expanded from its original width of 55–100ns, while the peak power of the expanded pulse is as half as that of the original pulse under the same laser fluence. Multiple shots of the expanded laser pulses increased the doping depth at the Al concentration of 1×1016 /cm3 to 100nm from 30nm of the single shot of the original short, high-peak power laser. The increased doping depth could be due to enhanced diffusion by extra vacancies generated by the repeated laser irradiations. Due to the smaller laser peak power, the expanded pulse laser can suppress damage generation under multiple laser shots and, as a result, leakage current of the pn junction diode is kept low.

Current-controlled unidirectional edge-meron motion

In order to address many of the challenges and bottlenecks currently experienced by traditional charge-based technologies, various alternatives are being actively explored to provide potential solutions of device miniaturization and scaling in the post-Moore's-law era. Amongst these alternatives, spintronic physics and devices have recently attracted rapidly increasing interest by exploiting the additional degree of electrons-spin. For example, magnetic domain-wall racetrack-memory and logic devices have been realized via manipulating domain-wall motion. As compared to domain-wall-based devices, magnetic skyrmions have the advantages of ultrasmall size (typically 5–100 nm in diameter), facile current-driven motion, topological stability, and peculiar emergent electrodynamics, promising for next-generation electronics applications in the post-Moore's-law regime. Here, a magnetic meron device, which behaves similarly to a PN-junction diode, is demonstrated for the first time, by tailoring the current-controlled unidirectional motion of edge-merons (i.e., fractional skyrmions) in a nanotrack with interfacial Dzyaloshinskii-Moriya interaction. The working principles of the meron device, theoretically predicted from the Thiele equation for topological magnetic objects, are further verified using micromagnetic simulations. The present study has revealed the topology-independent transport property of different magnetic objects and is expected to open the vista toward integrated composite circuitry (with unified data storage and processing) based on a single magnetic chip, as the meron device can be used, either as a building block to develop complex logic components or as a signal controller to interconnect skyrmion, domain-wall, and even spin-wave devices.

A Framework to Simulate Semiconductor Devices Using Parallel Computer Architecture

Device simulations have become an integral part of semiconductor technology to address many issues (short channel effects, narrow width effects, hot-electron effect) as it goes into nano regime, helping us to continue further with the Moore's Law. TCAD provides a simulation environment to design and develop novel devices, thus a leap forward to study their electrical behaviour in advance. In this paper, a parallel 2D simulator for semiconductor devices using Discontinuous Galerkin Finite Element Method (DG-FEM) is presented. Discontinuous Galerkin (DG) method is used to discretize essential device equations and later these equations are analyzed by using a suitable methodology to find the solution. DG method is characterized to provide more accurate solution as it efficiently conserve the flux and easily handles complex geometries. OpenMP is used to parallelize solution of device equations on manycore processors and a speed of 1.4x is achieved during assembly process of discretization. This study is important for more accurate analysis of novel devices (such as FinFET, GAAFET etc.) on a parallel computing platform and will help us to develop a parallel device simulator which will be able to address this issue efficiently. A case study of PN junction diode is presented to show the effectiveness of proposed approach.