Temperature Current-voltage Characteristics Research Articles

Temperature Effects on GaN/AlN Heterojunction in a Piezomagnetic and Piezoelectric Semiconductor Composite Fiber

In this article, considering the thermal effects, a PN GaN/AlN heterojunction in a piezomagnetic and piezoelectric semiconductor composite fiber driven by dynamic magnetic loads is studied. The true nonlinear constitutive equations of the electric current density for the composite heterojunction are employed. Thus, a nonlinear finite‐element method (FEM) is adopted to obtain dynamic responses of the composite heterojunction, including the mechanical displacement, electric potential, and electron and hole concentrations. By comparing dynamic responses with those derived by COMSOL Multiphysics, the nonlinear FEM is verified. Based on numerical results, regulation effects of the temperature on distributions of the mechanical displacement, electron and hole concentrations, and temperature–current–voltage characteristics are discussed.

Effect of titanium-dioxide nanoparticle on Richardson constant and barrier height of tartrazine dye based Schottky device

Recently Fruit Dyes have achieved a significant interest as organic devices because of they are widely available, customizable and biodegradable. But low conductivity is one of the major limitations. Low conductivity is due to low charge injection from the electrodes to the organic layer and the charge injection process is strongly dependent on the injection barrier height at the metal-dye interface. Higher barrier height causes low charge injection. A detailed analysis is needed to reduce the interfacial barrier to get better conductivity. In this work, we have estimated the interfacial barrier height of Indium tin oxide coated glass/Tartrazine dye/Copper based device with and without titanium dioxide nanoparticles. The devices have been prepared with dye and dye-nanoparticles blends by using the spin coating technique. We have measured the steady state dark current–voltage–temperature characteristics in the range of 288 K to 333 K to estimate the Richardson constant and interfacial barrier height. The Richardson constant was found to be modified from 44.35 × 10–3 to 07.34 × 10–3 Am−2 K−2. We also have found that interfacial barrier height is reduced from 0.71 eV to 0.64 eV in the presence of nanoparticles at room temperature. As the temperature increased, the interfacial barrier height increased to 0.72 eV from 0.71 eV and to 0.68 eV from 0.62 eV for dye based device with and without nanoparticles, respectively. Reduction of the interfacial barrier height indicates an increase in the charge injection through the interface. This work will be informative to improve the charge flow at the metal–fruit dye interface.

Improved-Performance Diamond Schottky Barrier Diode With Tin Oxide Interlayer

A SnO2 thin layer was deposited between the diamond and Schottky electrode to fabricate the metal–insulator–semiconductor Schottky barrier diode (MIS-SBD). The current–voltage and current–voltage–temperature characteristics in the range from 25 °C to 150 °C of diamond SBD were investigated. The Schottky barrier height of MIS-SBD is 1.84 eV. Compared with metal–semiconductor (MS) SBD, the diamond MIS-SBD shows more stable values of barrier height and ideality factor as temperature increased. The difference in interface states density between MIS-SBD and MS-SBD is almost 2 orders of magnitude, and the breakdown voltage was increased from 102 to 123 V after introducing SnO2 layer. These results indicate that the MIS-SBD with SnO2 insulating layer shows a better performance.

Improving the accuracy of temperature coefficient measurement of a PV module by accounting for the transient temperature difference between cell and backsheet

Accurate measurement of cell temperature inside a PV module is critical for the accurate measurement of Temperature Coefficients (TC) and Current-Voltage (I-V) characteristics corrected to Standard Test Conditions (STC). Estimating the cell temperature from the backsheet temperature while the module is heating or cooling is non-trivial because of the time-varying temperature difference between the cell and the backsheet. In this study, transient temperatures (for cell, EVA, front glass and backsheet) during heating and cooling are experimentally recorded for an inhouse laminated 4 cell multi c-Si PV coupon by inserting thermocouples during lamination. A One-Dimensional (1-D) transient simulation model using Finite Difference (FD) method is developed to observe the temperature profile along the thickness of the PV coupon. It is also used to obtain the temperature profiles for various layers for a full size 72-cell PV module as well as a glass-glass module with otherwise similar Bills of Materials. The maximum temperature difference observed between cell and backsheet was ∼ 2.35 ℃ for a glass-backsheet module and ∼ 5.3 ℃ for a glass-glass module which are heated to 75 ℃. Also, the transient temperature difference (TTD) showed an exponential decay profile after reaching the peak. The observed transient temperature difference led to ∼+7% error in the measurement of all the temperature coefficients of PV coupon or module if the backsheet temperature is used as a proxy for module / cell temperature. Accounting for this observed transient temperature difference between cell to backsheet leads to an improved accuracy of temperature coefficient measurements.

Realization of highly rectifying Schottky barrier diodes and pn heterojunctions on κ-Ga2O3 by overcoming the conductivity anisotropy

Novel devices based on orthorhombic κ-Ga2O3 could enable solar blind infrared detection or high-electron mobility transistors with large two-dimensional electron gas densities. Here, we report on the current transport parallel to the growth direction of κ-Ga2O3 layers grown by pulsed-laser deposition on highly conductive Al-doped ZnO back contact layers. Besides ohmic Ti/Al/Au contact layer stacks, vertical Pt/PtOx/κ-Ga2O3 and Pd/PdOx/κ-Ga2O3 Schottky barrier diodes and NiO/κ-Ga2O3 and ZnCo2O4/κ-Ga2O3 pn-heterodiodes are investigated by current–voltage measurements. While a lateral current transport is severely suppressed to less than 10−9Acm−2 due to rotational domains, we record a significant current flow through the ohmic contacts in the vertical direction of >0.1Acm−2. The Schottky barrier diodes and the pn-heterojunctions exhibit rectification ratios of up to seven orders of magnitude. Room temperature current–voltage characteristics of diode ensembles as well as temperature-dependent measurements for selected Pt-based diodes reveal a mean barrier height of ϕBm≈2.1eV and ideality factors down to η≈1.3.

DSSC using Wrightia tinctoria (Roxb.) R Br.: A trail

This paper focuses on the structure of Dye Sensitized Solar Cell (DSSC) engineered using Titanium dioxide (TiO2) nano-particles sensitized by extract from leaves of Wrightia tinctoria (Roxb.) R. Br. TiO2 thin films are screen printed over flexible Cu foil which serves as the back contact for the device structure. Fluorine doped Tin Oxide (FTO) grown over glass substrate using chemical spray pyrolysis technique is used as the front electrode with KOH as the electrolyte. The optical characterization of the dye is conducted using optical absorption and emission spectroscopic studies. A DSSC of the configuration (Cu|TiO2|Dye(danthapala)|KOH(Electrolyte)|FTO) was engineered. The electrical parameters of the engineered Dye Sensitized Solar Cells were characterized. The two-diode model was used to extract the series and shunt resistance, saturation current and diode ideality factor for the device from the room temperature current–voltage characteristics.

Spin-flip scattering in magnetic tunnel junctions: From current-voltage characteristics to spin-transfer torque

We examine room temperature current-voltage (IV) characteristics of $\mathrm{CoFeB}\phantom{\rule{0.16em}{0ex}}|\phantom{\rule{0.16em}{0ex}}\mathrm{MgO}\phantom{\rule{0.16em}{0ex}}|\phantom{\rule{0.16em}{0ex}}\mathrm{CoFeB}$ type of perpendicularly magnetized tunnel junctions developed for memory applications. From their nonlinear bias voltage dependence, a conductance ``cross-scaling'' is seen that is consistent with the involvement of inelastic spin-flip scattering in electrodes. A phenomenological model is constructed that connects the parameters of spin-flip scatter-related inelastic events with both magnetoresistance and spin-transfer torque. The model provides measurable, electrode-specific properties such as interface exchange stiffness as it affects spin-torque performance.

Demonstration of highly repeatable room temperature negative differential resistance in large area AlN/GaN double-barrier resonant tunneling diodes

Here, we present a systematical investigation of AlN/GaN double-barrier resonant tunneling diodes (RTDs) grown by plasma-assisted molecular beam epitaxy on metal-organic chemical vapor deposition GaN-on-sapphire templates. The processed devices featured an active region composed of 2.5 nm GaN quantum well sandwiched by two 1.5 nm AlN barriers and RTD mesa diameter ranging from 1 to 20 μm. Room temperature current–voltage characteristics exhibited a repeatable negative differential resistance (NDR) free of degradation and hysteresis after 1000 times subsequently up-to-down voltage sweeps across different sizes. High peak-to-valley current ratios of 1.93 and 1.58 were obtained at room temperature for 1 and 12 μm diameter devices, respectively, along with peak current densities of 48 and 36 kA/cm2 corresponding to peak voltages of 4.65 and 5.9 V. The peak current density decreased quickly initially and then was less susceptible to this averaging effect with increasing the device diameter. Temperature-dependent measurements revealed that the valley current density displayed a positive relationship to the temperature, and an abruptly increasement was observed for the devices with a diameter of 20 μm when the temperature rose over 230 K. We attributed this abnormal phenomenon to the increased contribution from acoustic and longitudinal optical (LO) phonon scattering, especially for the LO phonon scattering. The area dependence of electrical performance suggested that the leakage pathway through dislocations played a vital role for charge transport and there existed a threshold of dislocation density for NDR characteristics. These results promote further study for future implementation of III-nitride-based RTD oscillators into high-frequency and high-power terahertz radiation.

Compositional tuning of negative differential resistance in a bulk silver iodide memristor

Silver iodide a negative differential resistance (NDR) memristor

Simulation and analysis of the forward bias current–voltage–temperature characteristics of W/4H-SiC Schottky barrier diodes for temperature-sensing applications

The current-voltage (ID-VD) characteristics of W/4H-SiC Schottky barrier diodes (SBDs) are investigated in the 303–448 K temperature range by means of a numerical simulation study. Results showed a good agreement with measurements for a bias current ranging from 100 nA up to 10 mA. The main device parameters, such as the barrier height and ideality factor are found strongly temperature-dependent. The observed behaviours are interpreted by using the thermionic emission (TE) theory with a single Gaussian distribution of the barrier height (BH). The corresponding Richardson constant is A* = 148.8 Acm−2K−2. This value is close to the theoretical one of 146 Acm−2K−2 for n-type 4H-SiC.

Fabrication of interdigitated electrode (IDE) based ZnO sensors for room temperature ammonia detection

Interdigitated electrode (IDE) sensor has been successfully fabricated, characterised and successfully used for ammonia sensing. Silver (Ag) is used as IDE which is fabricated by using DC magnetron sputtering while ZnO sensing layer with three different dopants (Cd, Mg and Y) have been deposited over the Ag sputtered IDE by RF magnetron sputtering. The deposited sensing layer has been characterised by X-ray diffraction (XRD), Photoluminescence (PL) and Hall effect which reveal that typical ZnO characteristics. The room temperature current-voltage characteristics of the fabricated device show the ohmic behaviour for sensors SD1 (10 mol% Cd doped ZnO) and SD2 (10 mol% Mg doped ZnO) while Schottky behaviour for the sensor SD3 (2 mol% Y doped ZnO). The fabricated IDE sensors were exposed to the various concentration of ammonia, and the enhanced ammonia response has been observed compared to thin film sensors. The sensors SD1 and SD2 show higher ammonia response than SD3. However, fast response and speed recovery time were realised for device SD3 compared to SD1 and SD2. Among the three sensors, SD1 shows the maximum ammonia response. The enhanced ammonia sensing of fabricated sensors explained by band bending mechanism in detail.

Tuning the charge transport and photo-physical behavior in hybrid poly(3-hexylthiophene) and silver sulfide quantum dot based nanocomposite devices

Abstract The charge transport properties are studied in hybrid thin films composed of poly (3-hexylthiophene) polymer (P3HT) and silver sulfide (Ag2S) quantum dots (QDs) by temperature and photo-dependent current-voltage (J–V) characteristics. A complete reversal in J-V characteristics is observed in ITO/Nanocomposite/Au devices as the QDs’ concentration in the polymer matrix reaches to 50 wt percentage (wt. %). A detailed study of charge injection through ITO exhibits a transition in transport mechanism from direct tunnelling to thermionic emission with increasing QDs up to 20 wt % and further governed by space charge limited conduction for 50 and 80 wt % devices. Charge injection through Au shows the transition from Poole-Frenkel to thermionic emission as the QDs surpasses 10 wt % in polymer matrix. The effect of injection barrier and charge transfer phenomena on the transport properties are discussed in details by photoluminescence and photocurrent measurements.

Simulation and analysis of the current–voltage–temperature characteristics of Al/Ti/4H-SiC Schottky barrier diodes

The current–voltage characteristics of Al/Ti/4H-SiC Schottky barrier diodes have been investigated in the 85–445 K temperature range by means of a combined numerical and analytical simulation study. Simulation results showed a good agreement with measurements in the whole explored current range from 10 μA to 10 mA. The main device electrical parameters, namely the barrier height (BH) and ideality factor, were found to be strongly temperature-dependent. In particular, the ideality factor decreases while the BH increases with increasing temperature. The observed behaviours have been successfully interpreted by using the thermionic emission theory with a triple Gaussian distribution of the BH in three different temperature ranges, i.e. 85 ≤ ΔT1 ≤ 135 K, 180 ≤ ΔT2 ≤ 270 K, and 315 ≤ ΔT3 ≤ 445 K. The corresponding Richardson constants are A1* = 149.26 A cm−2 K−2, A2* = 138.19 A cm−2 K−2, and A3* = 173.21 A cm−2 K−2, respectively. These values are close to the theoretical result of 146 A cm−2 K−2 expected for n-type 4H-SiC. Finally, it has been highlighted that the current flowing through the Schottky junction is also determined by the thermionic-field emission mechanism.

Effectuality of Barrier Height Inhomogeneity on the Current–Voltage–Temperature Characteristics of Metal Semiconductor Structures with CdZnO Interlayer

Current-conduction/transport mechanisms (CCMs or CTMs) through barrier and barrier height (BH) formation in the Al/(CdZnO)/p-Si/Al diodes, which were prepared by the sol–gel method, were examined in the range of 110–380 K. The decrease of zero-bias BH (ΦBo) and increase of ideality factor (n) with decreasing temperature were observed. The classic Richardson plot indicated two distinct linear regions that correspond to low and high temperature range (LTR and HTR), respectively. Contrary to this, the acquired Richardson constant value (A*) was much lower than its theoretical value (32 A cm−2 K−2). Such abnormal behavior of the ΦBo, n and A* was attributed to the evidence of the barrier inhomogeneities, especially at low temperature. Therefore, the ΦBo−n, ΦBo and (n−1 − n) versus q/2kT plots were sketched to acquire significant clues for the Gaussian distribution (GD) of the BHs at rectifier contact area with the mean BH ( $$ \bar{\Phi }_{\rm{Bo}} $$ ) and standard deviation (σso), which also have two linear parts with distinct slopes. $$ \bar{\Phi } $$ and σso were calculated from the slope and intercept of ΦBo versus q/2kT plot as 0.802 eV and 0.066 V for LTR, 1.043 eV and 0.106 V for HTR, respectively. The $$ \bar{\Phi }_{\rm{Bo}} $$ and A* were acquired by utilizing the σso values and using the Richardson plot as 0.626 eV and 14.26 A cm−2 K−2 for LTR and 1.021 eV and 32.53 A cm−2 K−2 for HTR, respectively. Thus, the I–V–T characteristics of the Al/(CdZnO)/p-Si/Al diodes at forward biases were successfully elucidated by the double-GD of BHs with mean BHs of 0.626 eV and 1.021 eV, respectively.

Room temperature microwave oscillations in GaN/AlN resonant tunneling diodes with peak current densities up to 220 kA/cm2

We report the generation of room temperature microwave oscillations from GaN/AlN resonant tunneling diodes, which exhibit record-high peak current densities. The tunneling heterostructure grown by molecular beam epitaxy on freestanding GaN substrates comprises a thin GaN quantum well embedded between two AlN tunneling barriers. The room temperature current-voltage characteristics exhibit a record-high maximum peak current density of ∼220 kA/cm2. When biased within the negative differential conductance region, microwave oscillations are measured with a fundamental frequency of ∼0.94 GHz, generating an output power of ∼3.0 μW. Both the fundamental frequency and the output power of the oscillator are limited by the external biasing circuit. Using a small-signal equivalent circuit model, the maximum intrinsic frequency of oscillation for these diodes is predicted to be ∼200 GHz. This work represents a significant step towards microwave power generation enabled by resonant tunneling transport, an ultra-fast process that goes beyond the limitations of current III-Nitride high electron mobility transistors.

Hysteresis-free DC conduction in zinc oxide films with a conducting polymer counter electrode

A conducting polymer, namely poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been employed as an alternative metal counter electrode to study steady state charge conduction through a spin-coated 5.2 µm thick ZnO film in a sandwich structure on a fluorine doped tin oxide coated glass substrate. The room temperature current–voltage characteristics exhibit rectifying behaviour without hysteresis as the bias voltage is cycled between ± 10V for varying voltage sweep rate from 100 to 1000 mV/s. Thermionic emission is believed to be the dominant conduction mechanism at forward bias voltage V ≤ 2.5 V whereas the space charge limited current conduction becomes effective in a higher voltage region V > 2.5 V. The barrier height (φb), ideality factor (n) and series resistance (Rs) are found to be strongly temperature dependent parameters showing the increase of {phi _b} and simultaneous decreases of n and Rs within the range of 218–298 K. The behaviour of the temperature dependent charge carrier mobility in the higher voltage region has also been discussed. The use of PEDOT:PSS is quite promising as an alternative to metal electrodes in semiconductor devices.

Negative differential resistance in n-type noncompensated silicon at low temperature

We present the results on low temperature current-voltage characteristics of noncompensated Si doped by Sb. In the temperature range 1.9–2.25 K and at electrical fields smaller than 1 V/cm, the negative differential resistance (NDR) was observed. The external magnetic field enhances the region of the NDR. We attribute this effect to the delocalization of the D− states in the upper Hubbard band due to the accumulation of the charge injected by current.

Shading-induced failure in thin-film photovoltaic modules: Electrothermal simulation with nonuniformities

Finite element electrothermal modeling is employed to study shading-induced failure in monolithically integrated thin-film photovoltaic modules. A key element is spatial nonuniformity in current-voltage characteristics, which causes inhomogeneous current flow when part of a module is under reverse bias due to shading. Time-dependent calculations show that spots with lower reverse breakdown voltage experience greater current density and localized thermal runaway that can cause permanent damage, resulting in ohmic shunts. Such failure events lead to performance loss, especially when the module is in normal operating conditions and shunted currents lead to abnormally high module temperatures. Our simulations of temperature distributions, current-voltage characteristics, and electroluminescence are compared to data from the literature for copper indium gallium diselenide devices.

Current–voltage–temperature characteristics of PEDOT:PSS/ZnO thin film-based Schottky barrier diodes

In this work, we report the temperature dependence of the electrical parameters of PEDOT:PSS/ZnO Schottky barrier diodes (SBDs) grown on glass substrates. To understand the current conduction mechanism, the current–voltage–temperature characteristics of PEDOT:PSS/ZnO thin film SBDs were studied. The electrical parameters were extracted with both thermionic emission and Cheung models. The obtained Richardson constant and effective barrier height were 5 A cm−2 °K−2 and 0.74 eV, respectively. The diode ideality factor was 1.5 and the series resistance was 36 Ω. All these electrical parameters turned out to be temperature independent which was associated with the dominant transport mechanisms of thermionic emission. The Richardson constant slightly deviates from theoretical values due to the presence of interfacial defects created by the preparation and deposition of PEDOT:PSS and the ZnO film crystallinity. The conductive polymer PEDOT:PSS, as a Schottky contact to ZnO, arises as an alternative to the expensive noble metals: Pt, Pd, Ag and metal oxides: IrOx, PdOx, PtOx.

Irreversibility in room temperature current–voltage characteristics of NiFe2O4 nanoparticles: A signature of electrical memory effect

Room temperature I–V characteristics study, both in presence and absence of magnetic field (1800Oe), has been performed on NiFe2O4 nanoparticles, having different particle size (Ф~14, 21 and 31nm). Our experiments on these nanoparticles provide evidences for: (1) electrical irreversibility or hysteretic behaviour; (2) positive magnetoresistance and (3) magnetic field dependent electrical irreversibility or hysteresis in the sample. “Hysteretic” nature of I–V curve reveals the existence of electrical memory effect in the sample. Significantly, such hysteresis has been found to be tuned by magnetic field. In order to explain the observed electrical irreversibility, we have proposed a phenomenological model on the light of induced polarization in the sample. Both the positive magnetoresistance and the observed magnetic field dependence of electrical irreversibility have been explained through magnetostriction phenomenon. Interestingly, such effects are found to get reduced with increasing particle size. For NiFe2O4 nanoparticles having Ф=31nm, we did not observe any irreversibility effect. This feature has been attributed to the enhanced grain surface effect that in turn gives rise to the residual polarization and hence electrical memory effect in NiFe2O4 nanoparticles, having small nanoscopic particle size.