Forward Bias Current-voltage Characteristics Research Articles

Vertical GaN Schottky barrier diodes with area-selectively deposited p-NiO guard ring termination structure

In this study, the effect of p-NiO guard ring length on the properties of vertical GaN Schottky barrier diode was investigated extensively. The forward biased current-voltage characteristics of all diodes with different guard ring length follow the thermionic emission theory, showing nearly the same ideality factor and Schottky barrier height value. While the series resistance increases by nearly two times with the increasing guard ring lengths because the increasing depletion region at the p-NiO/n-GaN junction compresses the conduction path. Under reverse bias, the breakdown voltage of the SBD without any termination is relatively low due to the electric field crowding. The p-NiO guard ring is effective to enhance the breakdown voltage although the leakage current is comparable. However, the breakdown voltage decreases with the increasing guard ring length, which may be ascribed to the tunneling leakage caused by the imperfect p-NiO/n-GaN interface.

The effect of temperature on the forward bias electrical characteristics of both pure Ni and oxidized Ni/Au Schottky contacts on n-type GaN: A case study

The forward bias current-voltage (I-V) characteristics of both oxidized Ni/Au and pure Ni metal Schottky contacts on n-type GaN have been investigated in the temperature range 160–400 K. The I-V curves were fitted using thermionic emission (TE) theory. It was found that the zero-bias barrier height (ϕb0) decreases while the ideality factor (η) increases with decreasing temperature (i.e. To effect). As a result, various transport models are considered in the analysis of the I-V experimental data in order to explain the observed anomaly in η and ϕb0. The deviation from linearity in the To effect plot for oxidized Ni/Au can be explained in terms of Schottky barrier height (SBH) inhomogeneity. As a result, a linear correlation between the zero-bias barrier height and ideality factor at different temperatures was found using Tung’s theoretical approach in order to extrapolate the homogenous barrier height (ϕhom). For oxidized Ni/Au, it was found that there are two distinct ϕhom values with one representing the low temperature range (ϕhom_1 = 1.02 eV) and another representing the high temperature range (ϕhom_2 = 1.23 eV). However, for pure Ni, there is no inhomogeneity in the barrier height (i.e. ϕhom = 0.87 eV). Furthermore, the ϕb0-ap vs. q/(2kT) plot also shows evidence of a Gaussian distribution of barrier heights for both oxidezed Ni/Au (ϕb0-mean = 1.45 eV and σs = 141 mV) and pure Ni (ϕb0-mean = 0.92 eV and σs = 69.3 mV). The 1/η vs. 1000/T plot is constructed to investigate the different current transport mechanisms in both oxidized Ni/Au and pure Ni. These various current transport mechanisms at different temperatures can be attributed to the barrier inhomogeneity at the metal–semiconductor interface.

Comparison of electrical properties of CuO/n-Si contacts with Cu/n-Si

Abstract In this study, CuO/n-Si/Al heterojunction contacts were fabricated by thermal evaporation technique. Electrical characteristics of the samples were investigated with the current-voltage (I-V), capacitance-voltage/frequency (C-V/f), and conductancevoltage (G/V) measurements at room temperature. Also, Cu/n-Si/Al Schottky contact was produced as a reference sample to investigate the electrical properties of the samples. The values of ideality factor (n), barrier height ( Φb) and series resistance (Rs) of the samples were calculated from the forward bias current-voltage (I-V) and reverse bias capacitance-voltage (C-V) characteristics. Also, for checking the consistency of the results, Cheung and Norde functions were used. The experimental result values of CuO/n-Si contact were compared with the values of the reference Cu/n-Si Schottky diode. It was observed that the values of the ideality factor and barrier height of the CuO/n-Si heterojunction were higher than those of the Cu/n-Si Schottky contact, while the series resistance was lower. Also, it has been observed that the value of capacitance decreased with increasing frequency and after a certain value of frequency it was almost constant. The ideality factor of CuO/n-Si/Al heterostructure is about 2.40 and so, it is not close to the ideal behavior.

Electronic transport in epitaxial 4H–SiC based Schottky diodes modified selectively by swift heavy ions

Modifications in the defects and electronic transport properties of epitaxial 4H-nSiC(0001) Schottky barrier diodes have been carried out by selective 200 MeV Ag+14 ions irradiation, i.e., ions projected only on the Schottky contact area of the diode using a mask. Forward bias current-voltage (I–V) characteristics are measured in temperature (T) range from 273 K to 473 K. Interestingly, the barrier height found increased from 1.20 eV to 1.35 eV at 273 K and from 1.24 eV to 1.42 eV at 348 K after selective ion irradiation. At T ≥ 373 K, double barrier height features have seen in the I–V-T plots. The reverse bias I–V characteristics are measured up to −200 V, and in T range from 298 K to 473 K. The leakage current density found decreased from 9.57 × 10-9 A/cm2 to 2.98 × 10-10 A/cm2 at 298 K and from 5.53 × 10-8 A/cm2 to 4.17 × 10-8 A/cm2 at 373 K after selective irradiation, and deteriorated after that. The defects in pristine SiC with activation energy (ΔEA) of 0.29 eV and 0.13 eV are removed and a single defect with ΔEA of 0.38 eV observed after selective ion irradiation. Moreover, asymmetries are observed in capacitance-voltage characteristics of selectively irradiated devices. Role of electronic and nuclear energy loss mechanisms have been discussed to rationalize the performance of diodes. The proposed technique may be applicable in addressing the issues related to interface and bulk level defects in advance semiconducting materials, without using high temperatures.

A comparative study on theoretical and experimental methods using basic electrical parameters of Au/CNTs/lnP/Au–Ge diodes

In this study, we have reported experiments on interlayer performance of single and multi walled carbon nanotubes (SWCNTs and MWCNTs) for fabrication of n-InP substrates based diode applications and characterized with various methods to obtain ideal parameters. Structural and morphological properties of the nanotubes have been investigated by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) measurements, respectively. The Au/SWCNTs/n-InP and Au/MWCNTs/n-InP diodes have been prepared at the same conditions and electrically analyzed in the temperature range of 80–320 K by steps of 20 K, using forward bias current-voltage (I–V) characteristics. In characterization stage, various methods such as standard, analytical, evolutionary algorithm and numerical methods have been used to determine the ideality factor, barrier height and series resistance values of the diodes. The performance of the methods was compared in their classes and it was tried to find solutions more easily than the others.

High-Performance Temperature Sensors Based on Dual 4H-SiC JBS and SBD Devices.

Schottky diode-based temperature sensors are the most common commercially available temperature sensors, and they are attracting increasing interest owing to their higher Schottky barrier height compared to their silicon counterparts. Therefore, this paper presents a comparison of the thermal sensitivity variation trend in temperature sensors, based on dual 4H-SiC junction barrier Schottky (JBS) diodes and Schottky barrier diodes (SBDs). The forward bias current–voltage characteristics were acquired by sweeping the DC bias voltage from 0 to 3 V. The dual JBS sensor exhibited a higher peak sensitivity (4.32 mV/K) than the sensitivity exhibited by the SBD sensor (2.85 mV/K), at temperatures ranging from 298 to 573 K. The JBS sensor exhibited a higher ideality factor and barrier height owing to the p–n junction in JBS devices. The developed sensor showed good repeatability, maintaining a stable output over several cycles of measurements on different days. It is worth noting that the ideality factor and barrier height influenced the forward biased voltage, leading to a higher sensitivity for the JBS device compared to the SBD device. This allows the JBS device to be suitably integrated with SiC power management and control circuitry to create a sensing module capable of working at high temperatures.

Investigation of electrical properties of $$\hbox {In/ZnIn}_{2} \hbox {Te}_{4}/\hbox {n-Si/Ag}~\hbox {diode}$$ In/ZnIn 2 Te 4 / n-Si/Ag diode

\(\hbox {In/ZnIn}_{2}\hbox {Te}_{4}/\hbox {n-Si/Ag}\) diode structure was fabricated by the thermal deposition of a \(\hbox {ZnIn}_{2}\hbox {Te}_{4}\) thin film on n-Si wafer substrate with Ag metal back contact. The structural characteristics of the film were investigated in terms of composition, X-ray diffraction and topographic measurements. The diode structure was completed by evaporating In metal on the film surface as a top contact. The diode parameters as saturation current, barrier height, ideality factor and series resistance values were determined from the semi-logarithmic forward bias current–voltage characteristics of the diode. According to the assumption of the thermionic emission model, the ideality factor was found higher than unity and it was also observed that the barrier height and ideality factor showed a temperature-dependent profile resulting from the non-ideality in the current–voltage behaviour of the diode. As a result, the model was modified by considering inhomogeneous barrier formation and Gaussian distribution was expected to be dominant on 1.37 eV mean barrier height with a deviation of 0.18. In addition, the voltage dependence of these Gaussian diode parameters was investigated. The forward and reverse bias capacitance and conductance measurements showed that there was a slight change in capacitance values with frequency whereas the conductance values decreased with increase in frequency. In addition to the current–voltage analysis, the distribution of density of interface states and the values of series resistance were evaluated as a function of bias voltage and frequency.

Comparative study of I–V methods to extract Au/FePc/p-Si Schottky barrier diode parameters

So far, various methods have been proposed to extract the Schottky diode parameters from measured current–voltage characteristics. In this work, Schottky barrier diode with structure of Au/2(3),9(10),16(17),23(24)-tetra(4-(4-methoxyphenyl)-8-methylcoumarin-7 oxy) phthalocyaninatoiron(II) (FePc)/p-Si was fabricated and current–voltage measurements were carried out on it. In addition, current–voltage measurements were also performed on Au/p-Si structure, without FePc, to clarify the influence of the presence of an interface layer on the device performance. The measured current–voltage characteristics indicate that the interface properties of a Schottky barrier diode can be controlled by the presence of an organic interface layer. It is found that the room temperature barrier height of Au/FePc/p-Si structure is larger than that of the Au/p-Si structure. The obtained forward bias current–voltage characteristics of the Au/FePc/p-Si device was analysed by five different analytical methods. It is found that the extracted values of SBD parameters strongly depends on the method used.

An analysis of PN junctions in piezoelectric semiconductors

We present a theoretical study on the equilibrium state of a PN junction, which is created by two piezoelectric semiconductor half spaces doped oppositely, based on the equations of linear piezoelectricity and the conservation of charge for holes and electrons. The nonlinearity associated with the drift currents of electrons and holes, which appears as products of the unknown carrier concentrations and the unknown electric field, is linearized for small carrier concentration perturbations. An analytical solution is rigorously derived, which is able to show the shaping of the PN junction near the interface. The electromechanical fields and concentrations of electrons and holes near the interface of the PN junction, and the forward-bias current-voltage characteristics of the PN junction under different applied stresses, are calculated and discussed. The effects of a few physical parameters on the properties of the PN junction are investigated as well.

Organic–inorganic Au/PVP/ZnO/Si/Al semiconductor heterojunction characteristics

The paper reports the fabrication and characterization of a novel Au/PVP/ZnO/Si/Al semiconductor heterojunction (HJ) diode. Both inorganic n type ZnO and organic polyvinyl pyrrolidone (PVP) layers have grown by sol–gel spin-coating route at 2000 rpm. The front and back metallic contacts are thermally evaporated in a vacuum at pressure of 10-6 Torr having a diameter of 1.5 mm and a thickness of 250 nm. The detailed analysis of the forward and reverse bias current-voltage characteristics has been provided. Consequently, many electronic parameters, such as ideality factor, rectification coefficient, carrier concentration, series resistance, are then extracted. Based upon our results a non-ideal diode behavior is revealed and ideality factor exceeds the unity (n > 4). A high rectifying (~4.6 × 10 4) device is demonstrated. According to Cheung-Cheung and Norde calculation models, the barrier height and series resitance are respectively of 0.57 eV and 30 kΩ. Ohmic and space charge limited current (SCLC) conduction mechanisms are demonstrated. Such devices will find applications as solar cell, photodiode and photoconductor.

Investigation of optical and device parameters of colloidal copper tungsten selenide ternary nanosheets

Hot injection synthesis route has been successfully applied for the preparation of high quality Cu2WSe4 (CWSe) nanosheets in order to determine their optical characterization and device parameters. Several techniques including XRD, SEM, TEM and SAED were used to characterize these nanosheets. These techniques confirmed that Cu2WSe4 nanosheets crystal shapes of synthesized are rectangular and square sheet and the average crystal size is between 20 and 40 nm. The spin coating technique was successfully used to deposit uniform of Cu2WSe4 thin film. Cu2WSe4 thin film has directly transition with a band gap of 1.64 eV. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple–Didomenico (WD) model. The single oscillator energy $$\left( {{E_0}} \right)$$ and the dispersion energy $$\left( {{E_d}} \right)$$ were estimated. Au/Cu2WSe4/n-Si structures was fabricated and its main electrical characteristics described by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of Au/Cu2WSe4/n-Si at room temperature were studied to investigate its basic electrical parameters [i.e. saturation current ( $${I_0}$$ ), ideality factor ( $$n$$ ), barrier height ( $${\Phi _B}$$ ), series ( $${R_s}$$ )]. Structural and optical mechanisms were discussed for future applications in optoelectronic devices.

Effects of interface modification on electrical and optoelectronic properties of p-type CuAlO2/n-type Si heterojunction devices

The effect of interface modification on the electrical properties of heterojunction diodes based on the p-type CuAlO2 and n-type Si is investigated. Compared with the CuAlO2/Si device without H2O2 treatment, the CuAlO2/Si device with H2O2 treatment exhibits a better rectification behavior. The forward-bias current–voltage characteristics can be explained on the basis of the space charge limited current theory for CuAlO2/Si device without H2O2 treatment. However, the thermionic emission model is the dominant process in this fabricated CuAlO2/Si device with H2O2 treatment. The enhanced device performance is mainly the result of the formation of Si–O bonds that serves to reduce the number of interface states. The effect of H2O2 treatment on the sensitivity to solar irradiation and the response time for CuAlO2/Si devices is also studied. An increase in the values of photocurrent and photosensitivity is attributed to the rectification performance improvement that results from interface passivation.

Electrical characteristics of Au/n-Si (MS) Schottky Diodes (SDs) with and without different rates (graphene + Ca1.9Pr0.1Co4Ox-doped poly(vinyl alcohol)) interfacial layer

In order to see effects of interfacial (with and without different graphene (GP) + Ca1.9Pr0.1Co4Ox-doped PVA) layer on the electrical characteristics of conventional Au/n-Si (MS) contacts. Therefore, Au/(GP + Ca1.9Pr0.1Co4Ox-doped PVA)/n-Si (MPS) structures were fabricated with different rates of (%3 GP, %7 GP) PVA and were fabricated on same n-Si wafer. Au/n-Si (MS), Au/PVA/n-Si, Au/%3GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si and Au/%7GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si structures were fabricated and their main electrical characteristics compared each other by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of with and without GP + Ca1.9Pr0.1Co4Ox-doped PVA/n-Si at room temperature were studied to investigate its main electrical parameters. The energy density distribution profile of the interface states (Nss) was obtained from the forward bias I–V data by taking into account voltage dependent ideality factor (n(v)) and effective barrier height (Φe) and they increase from at about mid-gap energy of Si to bottom of conductance band edge. In addition, voltage dependent profile of resistivity of the structure was obtained from I–V data for four different structures. The analysis of experimental results reveals that the existence of GP + Ca1.9Pr0.1Co4Ox-doped PVA interfacial layer improves the performance of MS structure. In order to determine the dominant current-transport mechanism (CTM) in the whole forward bias region of these structures, the double logarithmic forward bias I–V plots were also drawn. These plots exhibit two distinct linear region with different slopes which are corresponding to intermediate and high forward bias voltages. The slope of these plots show that in the region 1 (low biases) the dominant CTM is trap-charge-limited current (TCLC), whereas in the region 2 (high biases) is space-charge-limited current (SCLC) for four diodes.

Fabrication and electrical characterization of nickel/p-Si Schottky diode at low temperature

In this study the current–voltage and capacitance–voltage characteristics of metal semiconductor Ni/p-Si(100) based Schottky diode on p- type silicon measured over a wide temperature range (60–300 K) have been studied on the basis of thermionic emission diffusion mechanism and the assumption of a Gaussian distribution of barrier heights. The parameters ideality factor, barrier height and series resistance are determined from the forward bias current–voltage characteristics. The barrier height for Ni/p-Si(100) Schottky diode found to vary between 0.513 eV and 0.205 eV, and the ideality factor between 2.34 and 8.88 on decreasing temperature 300–60 K. A plot involving the use of ϕb versus 1/T data is used to gather evidence for the occurrence of a Gaussian distribution of barrier height and obtain the value of standard deviation. The observed temperature dependences of barrier height and ideality factor and non-linear activation energy plot are attributed to the Gaussian distribution of barrier heights at the metal-semiconductor contact. The barrier height of Ni/p-Si(100) Schottky diode was also measured over wide temperature from the capacitance-voltage study.

The Effect of Interface States Density Distribution and Series Resistance on Electrical Behaviour of Schottky Diode

The forward and reverse bias current-voltage characteristics of the In/p-Si Schottky barrier diode (SBD) have been investigated in the temperature range of 360K to 120K. The current-voltage measurements have been used to extract the electrical parameters such as series resistance, barrier height, ideality factor and interface states density distribution. The higher values of series resistance, ideality factor and interface states energy distribution at low temperature was attributed to the presence of an interfacial insulated layer, popularly known as metal-insulator-semiconductor (MIS) devices. The temperature dependence energy distribution profile of interface states was obtained from the forward bias I-V-T measurements by taking into account the bias dependence of the effective barrier height and ideality factor. The interface states density (NSS) decreased with increasing temperature was explained by the result of atomic restructuring and reordering at the metal semiconductor interface.

Improved performance of AlGaN-based deep ultraviolet light-emitting diodes with n-AlGaN underlayers

We demonstrate notable performance improvement of 270 nm deep ultraviolet light-emitting diodes (DUV-LEDs) by inserting an n-AlGaN underlayer (UL), which was directly beneath an AlGaN multiple quantum well (MQW) active region. This DUV-LED exhibited significantly improved forward and reverse bias current-voltage characteristics, and spectral properties. As a result, the turn-on voltage was decreased from 7 to 4.6 V by introducing the n-AlGaN UL, and the maximum light output power and external quantum efficiency of DUV-LEDs with the n-AlGaN UL, obtained via on-wafer measurement, were increased by factors of 3.6 and 2.2, respectively. Further enhancements can be realized by using high-quality AlN/sapphire templates together with the n-AlGaN UL. These improvements were considered to be attributed to the introduction of the n-AlGaN UL which improved electron injection and reduced the quantum confined stark effect in the AlGaN MQWs.

Electron Transport Mechanisms in Ag Schottky Contacts Fabricated on O-polar and Nonpolar m-plane Bulk ZnO

We prepared silver Schottky contacts to O-polar and nonpolar m-plane bulk ZnO wafers. Then, by considering various transport models, we performed a comparative analysis of the current transport properties of Ag/bulk ZnO Schottky diodes, which were measured at 300, 200, and 100 K. The fitting of the forward bias current-voltage (I-V) characteristics revealed that the tunneling current is dominant as the transport component in both the samples. Compared to thermionic emission (TE), a stronger contribution of tunneling current was observed at low temperature. The reverse bias I-V characteristics were well fitted with the thermionic field emission (TFE) in both the samples. The presence of acceptor-like adsorbates, such as O₂ and H₂O, modulated the surface conductive state of ZnO, thereby affecting the tunneling effect. The degree of activation/passivation of acceptor-like adsorbates might be different in both the samples owing to their different surface morphologies and surface defects (e.g., oxygen vacancies).

Forward-bias diode parameters, electronic noise, and photoresponse of graphene/silicon Schottky junctions with an interfacial native oxide layer

Metal-semiconductor Schottky junction devices composed of chemical vapor deposition grown monolayer graphene on p-type silicon substrates are fabricated and characterized. Important diode parameters, such as the Schottky barrier height, ideality factor, and series resistance, are extracted from forward bias current-voltage characteristics using a previously established method modified to take into account the interfacial native oxide layer present at the graphene/silicon junction. It is found that the ideality factor can be substantially increased by the presence of the interfacial oxide layer. Furthermore, low frequency noise of graphene/silicon Schottky junctions under both forward and reverse bias is characterized. The noise is found to be 1/f dominated and the shot noise contribution is found to be negligible. The dependence of the 1/f noise on the forward and reverse current is also investigated. Finally, the photoresponse of graphene/silicon Schottky junctions is studied. The devices exhibit a peak responsivity of around 0.13 A/W and an external quantum efficiency higher than 25%. From the photoresponse and noise measurements, the bandwidth is extracted to be ∼1 kHz and the normalized detectivity is calculated to be 1.2×109 cm Hz1/2 W−1. These results provide important insights for the future integration of graphene with silicon device technology.

Esaki Diodes in van der Waals Heterojunctions with Broken-Gap Energy Band Alignment.

van der Waals (vdW) heterojunctions composed of two-dimensional (2D) layered materials are emerging as a solid-state materials family that exhibits novel physics phenomena that can power a range of electronic and photonic applications. Here, we present the first demonstration of an important building block in vdW solids: room temperature Esaki tunnel diodes. The Esaki diodes were realized in vdW heterostructures made of black phosphorus (BP) and tin diselenide (SnSe2), two layered semiconductors that possess a broken-gap energy band offset. The presence of a thin insulating barrier between BP and SnSe2 enabled the observation of a prominent negative differential resistance (NDR) region in the forward-bias current-voltage characteristics, with a peak to valley ratio of 1.8 at 300 K and 2.8 at 80 K. A weak temperature dependence of the NDR indicates electron tunneling being the dominant transport mechanism, and a theoretical model shows excellent agreement with the experimental results. Furthermore, the broken-gap band alignment is confirmed by the junction photoresponse, and the phosphorus double planes in a single layer of BP are resolved in transmission electron microscopy (TEM) for the first time. Our results represent a significant advance in the fundamental understanding of vdW heterojunctions and broaden the potential applications of 2D layered materials.

On double exponential forward bias current-voltage (I–V) characteristics of Au/Ca3Co4Ga0.001Ox/n-Si/Au (MIS) type structures in temperature range of 80–340 K

Current transport mechanisms (CTMs) of Au/Ca3Co4Ga0.001Ox/n-Si/Au (MIS) type structures were investigated using current–voltage (I–V) characteristics in the temperature range of 80–340 K. Semilogarithmic I–V plots show two linear regions corresponding to low (0.075–0.250 V) and moderate (0.27–0.70 V) biases, respectively. Zero-bias barrier height (ΦB0) was observed to increase with increase in the temperature, whereas opposite behaviour was observed for ideality factor (n). ΦB0 and (n−1–1) vesus q/2kT and ΦB0 versus n plots were drawn to get an evidence of Gaussian distribution (GD) of the barrier heights. These plots, too, show two linear regions corresponding to low (80–160 K) and high (200–340 K) temperature ranges (LTR and HTR), respectively. Mean value of barrier height (B0) and standard deviation (σs) were extracted from the intercept and slope of ΦB0 versus q/2kT plots for two linear regions as 0.382 eV, 0.0060 V for LTR and 0.850 eV, 0.135 V for HTR at low biases and 0.364 eV, 0.0059 V for LTR and 0.806 eV, 0.132 V for HTR at high biases, respectively. B0 and Richardson constant (A*) values were also obtained from the intercept and slope of the modified Richardson (Ln(Io/T2)−(q2σs2/2k2T2) versus q/kT) plots as 131.81 Acm−2 K−2, 0.381 eV for LTR and 129.35 Acm−2 K−2, 0. 854 eV for HTR at low biases and 148.01 Acm−2 K−2, 0.377 eV for LTR and 143.77 Acm−2 K−2, 0.812 eV for HTR at high biases, respectively. In conclusion, CTM in the structure can be successfully explained in terms of thermionic emission theory with the double GD of barrier heights.