Fabrication and electrical characteristics of Schottky diode based on organic material

The current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of Al/Orange G/n-Si/AuSb structure were investigated at room temperature. A modified Norde’s function combined with conventional forward I-V method was used to extract the parameters including barrier height (BH) and the series resistance. The barrier height and series resistance obtained from Norde’s function was compared with those from Cheung functions, and it was seen that there was a good agreement between series resistances from both methods. The C-V characteristics were performed at 10 kHz and 500 kHz frequencies, and C-f characteristics were performed 0.0 V, +0.4 V and −0.4 V.     

Electrical and photovoltaic properties of a n-Si/chitosan/Ag photodiode

The electrical and photovoltaic properties of AuSb/n-Si/chitosan/Ag diode have been investigated. The ideality factor, barrier height and Richardson constant values of the diode at room temperature were found to be 1.91, 0.88 eV and 121.4 A/cm² K², respectively. The ideality factor of the diode is higher than unity, suggesting that the diode shows a non-ideal behaviour due to series resistance and barrier height inhomogeneities. The barrier height and ideality factor values of Ag/CHT/n-Si diode at room temperature are significantly larger than that of the conventional Ag/n-Si Schottky diode. The φ_B value obtained from C-V measurement is higher than that of φ_B value obtained from I-V measurement. The discrepancy between φ_B(C-V) and φ_B(I-V) barrier height values can be explained by Schottky barrier height inhomogeneities. AuSb/n-Si/chitosan/Ag diode indicates a photovoltaic behaviour with open circuit voltage (V_oc = 0.23 V) and short-circuit current density (J_sc = 0.10 μA/cm⁻²) values.     

The effects of the temperature and annealing on current-voltage characteristics of Ni/n-type 6H-SiC Schottky diode

The temperature dependence of current-voltage (I-V) characteristics of as-fabricated and annealed Ni/n-type 6H-SiC Schottky diode has been investigated in the temperature range of 100-500 K. The forward I-V characteristics have been analysed on the basis of standard thermionic emission theory. It has been shown that the ideality factor (n) decreases while the barrier height (Φ_b) increases with increasing temperature. The values of Φ_b and n are obtained between 0.65-1.25 eV and 1.70-1.16 for as-fabricated and 0.74-1.70 eV and 1.84-1.19 for annealed diode in the temperature range of 100-500 K, respectively. The I-V characteristics of the diode showed an increase in the Schottky barrier height, along with a reduction of the device leakage current by annealing the diode at 973 K for 2 min.     

Interface control of conventional n-type silicon/metal by n-channel organic semiconductor

The rectifying and interface state density properties of n-Si/violanthrone-79/Au metal-diode have been investigated by current-voltage and capacitance-conductance-frequency methods. The ideality factor, barrier height and average series resistance of the diode were found to be 2.07, 0.81 eV and 5.04 kΩ respectively. At higher voltages, the organic layer contributes to I-V characteristics of the diode due to space-charge injection into the organic semiconductor layer and the trapped-charge-limited current mechanism is dominant mechanism for the diode. The barrier height obtained from C-V measurement is lower than the barrier height obtained I-V measurement and the organic layer creates an excess physical barrier for the diode. The interface state density of the diode was found to be 1.70 × 10¹¹ eV⁻¹ cm⁻² at 0.2 V and 1.72 × 10¹¹ eV⁻¹ cm⁻² at 0.4 V.The obtained electronic parameters indicate that the organic layer provides the conventional n-type silicon/metal interface control option.     

Laterally inhomogeneous barrier analysis of identically prepared Cd/CdS/n-Si/Au-Sb structures by SILAR method

In this study, CdS thin films have been deposited on n-Si substrate using a successive ionic layer adsorption and reaction (SILAR) method at room temperature. Structural properties have been investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The XRD and SEM investigations show that films are covered well, polycrystalline structure and good crystallinity levels. The Cd/CdS/n-Si/Au-Sb structures (28 dots) have been identically prepared by the SILAR method. The effective barrier heights and ideality factors of these structures have been obtained from forward bias current-voltage (I-V) and reverse bias capacitance voltage (C-V) characteristics. The barrier height (BH) for the Cd/CdS/n-Si/Au-Sb structure calculated from the I-V characteristics have ranged from 0.664 eV to 0.710 eV, and the ideality factor from 1.190 to 1.400. Lateral homogeneous barrier height has been determined approximately 0.719 eV from the experimental linear relationship between BHs and ideality factors. The experimental BH and ideality factor distributions obtained from the I-V characteristics have been fitted by a Gaussian function, and their means of values have been found to be (0.683 ± 0.01) eV and (1.287 ± 0.05), respectively. The barrier height values obtained from the reverse bias C⁻²-V characteristics have ranged from 0.720 eV to 0.865 eV and statistical analysis yields the mean (0.759 ± 0.02) eV. Additionally, a doping concentration obtained from C⁻²-V characteristics has been calculated (8.55 ± 1.62) × 10¹⁴ cm⁻³.     

Electrical and interface state density properties of the 4H-nSiC/[6,6]-phenyl C61-butyric acid methyl ester/Au diode

The electrical and interface state density properties of the Ni/4H-nSiC/PCBM/Au diode have been investigated by current-voltage, capacitance-voltage and conductance-frequency methods. The ideality factor, barrier height and series resistance values of the diode were found to be 2.28, 1.10 eV and 3.76 × 10⁴ Ω, respectively. The diode shows a non-ideal I-V behaviour with an ideality factor greater than unity that could be ascribed to the interfacial layer, interface states and series resistance. The obtained barrier height (1.10 eV) of the Ni/4H-nSiC/PCBM/Au diode is lower than that of Ni/4H-nSiC diode (1.32 eV). This indicates that the PCBM organic layer induces a change of 160 meV in the barrier height of the Ni/4H-nSiC diode. The interface state density of the diode was determined from G_p/ω-f plots and was of order of 5.61 × 10¹² eV⁻¹ cm⁻².     

Effect of series resistance on the electrical characteristics and interface state energy distributions of Sn/p-Si (MS) Schottky diodes

In this study, electrical characteristics of the Sn/p-type Si (MS) Schottky diodes have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The barrier height obtained from C-V measurement is higher than obtained from I-V measurement and this discrepancy can be explained by introducing a spatial distribution of barrier heights due to barrier height inhomogeneities, which are available at the nanostructure Sn/p-Si interface. A modified Norde’s function combined with conventional forward I-V method was used to extract the parameters including barrier height (Φ_b) and the series resistance (R_S). The barrier height and series resistance obtained from Norde’s function was compared with those from Cheung functions. In addition, the interface-state density (N_SS) as a function of energy distribution (E_SS-E_V) was extracted from the forward-bias I-V measurements by taking into account the bias dependence of the effective barrier height (Φ_b) and series resistance (R_S) for the Schottky diodes. While the interface-state density (N_SS) calculated without taking into account series resistance (R_S) has increased exponentially with bias from 4.235 × 10¹² cm⁻²eV⁻¹ in (E_SS - 0.62) eV to 2.371 × 10¹³ cm⁻²eV⁻¹ in (E_SS - 0.39) eV of p-Si, the N_SS obtained taking into account the series resistance has increased exponentially with bias from of 4.235 × 10¹² to 1.671 × 10¹³ cm⁻²eV⁻¹ in the same interval. This behaviour is attributed to the passivation of the p-doped Si surface with the presence of thin interfacial insulator layer between the metal and semiconductor.     

Effect of 6 MeV electron irradiation on electrical characteristics of the Au/n-Si/Al Schottky diode

Electron irradiation of the Au/n-Si/Al Schottky diode was performed by using 6 MeV electrons and 3 × 10¹² e⁻/cm² fluency. The current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of the unirradiated and irradiated Schottky diode were analyzed. It was seen that the values of the barrier height, the series resistance, and the ideality factor increased after electron irradiation. However, there was a decrease in the leakage current with electron irradiation. The increase in the barrier height and in the series resistance values was attributed to the dopant deactivation in the near-interface region. The interface states, N_ss, have been decreased significantly after electron irradiation. This was attributed to the decrease in recombination centre and the existence of an interfacial layer. A decrease in the capacitance was observed after electron irradiation. This was attributed to decrease in the net ionized dopant concentration with electron irradiation.     

Analysis of interface states and series resistance of Ag/SiO2/n-Si MIS Schottky diode using current-voltage and impedance spectroscopy methods

The electrical characteristics and interface state density properties of Ag/SiO₂/n-Si metal-insulator-semiconductor diode have been analyzed by current-voltage and impedance spectroscopy techniques. The electronic parameters such as barrier height, ideality factor and average series resistance were determined and were found to be 0.62 eV, 1.91 and 975.8 Ω, respectively. The calculated ideality factor shows that Ag/SiO₂/n-Si structure obeys a metal-interfacial layer-semiconductor configuration rather than ideal Schottky barrier diode. The interface state density of the diode is of order of ∼10¹¹ eV⁻¹ cm⁻². The dielectrical relaxation mechanism of the diode is analyzed by Cole-Cole plots, indicating the presence of single relaxation mechanism. It is evaluated that the interfacial oxide layer modifies electrical parameters such as interface state density, series resistance and barrier height of Ag/SiO₂/n-Si diode.     

Interface control and photovoltaic properties of n-type silicon/metal junction by organic dye

The electronic parameters and photovoltaic properties of the Au/methylene blue/n-Si diodes were investigated by current-voltage and capacitance-conductance-frequency techniques. The diode exhibits a non-ideal behavior due the series resistance, organic layer and oxide layer. The barrier height (1.04 eV) of the Au/methylene blue/n-Si is higher than that of Au/n-Si Schottky diode (0.83 eV) due to an excess barrier formed by organic layer. The interface state density of the diode was determined using a conductance technique and was found to be 3.25 × 10¹² eV⁻¹ cm⁻². The diode shows a photovoltaic behavior with a maximum open circuit voltage V_oc of 0.23 V and short-circuit current I_sc of 20.8 μA under 100 mW/cm². It is evaluated that Au/methylene blue/n-Si is an organic-on-inorganic photodiode with the obtained electronic parameters and methylene blue organic dye controls the interface and electrical properties of conventional metal/n-type silicon junction.     

Numerical simulation of the inhomogeneous barrier height of an Au/n-InP Schottky diodeKamel Zeghdar1, Lakhdar Dehimi1, 2, Achour Saadoune1, Nouredine Sengouga1,*

We report the current-voltage(I-V) characteristics of the Schottky diode(Au/n-InP) as a function of temperature. The SILVACO-TCAD numerical simulator is used to calculate the I-V characteristic in the temperature range of 280-400 K. This is to study the effect of temperature on the I-V curves and assess the main parameters that characterize the Schottky diode such as the ideality factor, the height of the barrier and the series resistance. The I-V characteristics are analyzed on the basis of standard thermionic emission(TE) theory and the inhomogeneous barrier heights(BHs) assuming a Gaussian distribution. It is shown that the ideality factor decreases while the barrier height increases with increasing temperature, on the basis of TE theory. Furthermore, the homogeneous BH value of approximately 0.524 eV for the device has been obtained from the linear relationship between the temperature-dependent experimentally effective BHs and ideality factors. The modified Richardson plot, according to the inhomogeneity of the BHs, has a good linearity over the temperature range. The evaluated Richardson constant A^* was 10.32 A·cm^-2·K^-2, which is close to the theoretical value of 9.4 A·cm^-2·K^-2 for n-InP. The temperature dependence of the I-V characteristics of the Au/n-InP Schottky diode have been successfully explained on the basis of the thermionic emission(TE) mechanism with a Gaussian distribution of the Schottky barrier heights(SBHs). Simulated I-V characteristics are in good agreement with the measurements[Korucu D, Mammadov T S. J Optoelectronics Advanced Materials, 2012, 14:41]. The barrier height obtained using Gaussian Schottky barrier distribution is 0.52 eV, which is about half the band gap of InP.     

The analysis of I-V characteristics of Schottky diodes by thermionic emission with a Gaussian distribution of barrier height

The current-voltage (I-V) characteristics of Al/p-Si Schottky barrier diode (SBD) with native insulator layer were measured in the temperature range of 178-440 K. The estimated zero-bias barrier height Φ_B0 and the ideality factor n assuming thermionic emission (TE) theory have shown strong temperature dependence. Evaluation of the forward I-V data have revealed an increase of zero-bias barrier height Φ_B0 but the decrease of ideality factor n with the increase in temperature. The experimental and theoretical results of the tunneling current parameter E_o against kT/q were plotted to determine predominant current-transport mechanism. But the experimental results were found to be disagreement with the theoretical results of the pure TE, the thermionic-field emission (TFE) and the field emission (FE) theories. The conventional Richardson plot has exhibited non-linearity below 240 K with the linear portion corresponding to the activation energy of 0.085 eV and Richardson constant (A^*) value of 2.48 × 10⁻⁹ A cm⁻² K⁻² which is much lower than the known value of 32 A cm⁻² K⁻² for holes in p-type Si. Such behaviours were attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Thus, the modified ln(I_o/T²) − q2σo2/2k²T² vs q/kT has plotted. Then A^* was calculated as 38.79 A cm⁻² K⁻² without using the temperature coefficient of the barrier height. This value of the Richardson constant 38.79 A cm⁻² K⁻² is very close to the theoretical value of 32 A K⁻² cm⁻² for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/p-Si Schottky barrier diodes with native insulator layer can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights.     

Effects of temperature on series resistance determination of electrodeposited Cr/n-Si/Au-Sb Schottky structures

Temperature dependences of the series resistance in the Cr/n-Si/Au-Sb Schottky structures prepared by electrodeposition method have been studied using current-voltage (I-V) characteristics in the 80-320 K temperature range by steps of 20 K. However, the values of series resistance obtained from Cheung functions were compared with each other, and it was seen that there is a good agreement between the values of the series resistance. A modified Norde’s function combined with conventional forward I-V method was used to extract the parameters including barrier height and the series resistance. The barrier height and series resistance obtained from Norde’s function were compared with those from Cheung functions. The values of barrier height and series resistance have very different especially towards to the lower temperatures. This is attributed to non-ideal I-V characteristics of the Cr/n-Si/Au-Sb Schottky structure and non-pure thermionic emission theory due to the low temperature effects.     

Dynamic I-V characteristics of ion currents in SiO2 films at low concentrations of mobile charges: Measurements of low concentrations of mobile ions

Factors that affect the accuracy and sensitivity of the method of dynamic I-V characteristics for ion currents of metal/oxide/semiconductor structures with a low (N _S ～ 10⁹–10¹⁰ cm^?2) concentration of mobile ions in the oxide are analyzed comprehensively. Simultaneous measurements of the dynamic I-V and low-frequency C-V characteristics show that the measurement error is about 10% for concentrations of no less than 10⁹ cm^?2.     

Fabrication and electrical characterization of Al/p-ZnIn2Se4 thin film Schottky diode structure

Polycrystalline thin films of ternary ZnIn₂Se₄ compound with p-type conductivity were deposited on a pre-deposited aluminium (Al) film by a flash evaporation technique. A Schottky diode comprising of Al/p-ZnIn₂Se₄ structure was fabricated and characterized in the temperature range 303–323 K in dark condition. The Schottky diode was subjected to current (I)-voltage (V) and capacitance (C)-voltage (V) characterization. The Al/p-ZnIn₂Se₄ Schottky diode showed behaviour typical of a p-n junction diode. The devices showed very good diode behaviour with the rectification ratio of about 10⁵ at 1.0 V in dark. The Schottky diode ideality factor, barrier height, carrier concentration, etc. were derived from I-V and C-V measurements. At lower applied voltages (V≤0.5 V), the electrical conduction was found to take place by thermionic emission (TE) whereas at higher voltages (V>0.5 V), a space charge limited conduction mechanism (SCLC) was observed. An energy band diagram was constructed for fabricated Al/p-ZnIn₂Se₄ Schottky diode.     

Calculation from the current-voltage and capacitance-voltage measurements of characteristics parameters of Cd/CdS/n-Si/Au-Sb structure with CdS interface layer grown on n-Si substrate by SILAR method

The CdS thin film has been directly formed on n-type Si substrate to form an interfacial layer between cadmium (Cd) and n-type Si with Successive Ionic Layer Adsorption and Reaction (SILAR) method. An Au-Sb electrode has been used as an ohmic contact. The Cd/CdS/n-Si/Au-Sb structure has demonstrated clearly rectifying behaviour by the current-voltage (I-V) curves studied at room temperature. The characteristics parameters such as barrier height, ideality factor and series resistance of Cd/CdS/n-Si/Au-Sb structure have been calculated from the forward bias I-V and reverse bias C⁻²-V characteristics. The diode ideality factor and the barrier height have been calculated as n = 2.06 and Φ_b = 0.92 eV by applying a thermionic emission theory, respectively. The diode shows non-ideal I-V behaviour with an ideality factor greater than unity that can be ascribed to the interfacial layer, the interface states and the series resistance. At high current densities in the forward direction, the series resistance (R_s) effect has been observed. The values of R_s obtained from dV/d(lnI)-I and H(I)-I plots are near to each others (R_s = 182.24 Ω and R_s = 186.04 Ω, respectively). This case shows the consistency of the Cheung′s approach. In the same way, the barrier height calculated from C⁻² -V characteristics varied from 0.698 to 0.743 eV. Furthermore, the density distribution of interface states (N_ss) of the device has been obtained from the forward bias I-V characteristics. It has been seen that, the N_ss has almost an exponential rise with bias from the mid gap toward the bottom of conduction band.     

Water-soluble poly(3,4-ethylenedioxythiophene)/nano-crystalline TiO2 heterojunction solar cells

Nanocrystalline titanium dioxide (TiO₂) thin films were prepared by the sol-gel method and were then used to fabricate an indium-tin oxide (ITO)/nano-crystalline TiO₂/poly(3,4-ethylenedioxythiophene) (PEDOT)/Au device. The junction thus obtained shows a rectifying behavior. Their current-voltage (I-V) characteristics in dark indicate that a heterojunction at the nano-crystalline TiO₂/PEDOT interface has been created. The measured open-circuit voltage (V_oc) and short-circuit current (I_sc) for the device under illumination with 50 mW/cm² light intensity under AM 1.5 conditions (device dimension was 1 cm²) are V_oc=0.39 V, I_sc=54.9 μA/cm², the filling factor (FF)=0.429 and the energy conversion efficiency (η)=0.03%.     

Analysis of electronic parameters and interface states of boron dispersed triethanolamine/p-Si structure by AFM, I-V, C-V-f and G/ω-V-f techniques

The electronic parameters and interface state properties of boron dispersed triethanolamine/p-Si structure have been investigated by atomic force microscopy, I-V, C-V-f and G/ω-V-f techniques. The surface topography and phase image of the TEA-B film deposited onto p-Si substrate were analyzed by atomic force microscopy. The atomic force microscopy results show a homogenous distribution of boron particles in triethanolamine film. The electronic parameters (barrier height, ideality factor and average series resistance) obtained from I-V characteristics of the diode are 0.81 eV, 2.07 and 5.04 kΩ, respectively. The interface state density of the diode was found to be 2.54 × 10¹⁰ eV⁻ cm⁻² under V_g = 0. The obtained D_it values obtained from C-V and G/ω measurements are in agreement with each other. The profile of series resistance dependent on voltage and frequency confirms the presence of interface states in boron dispersed triethanolamine/p-Si structure. It is evaluated that the boron dispersed triethanolamine controls the electronic parameters and interface properties of conventional Al/p-Si diode.     

The effects of 12 MeV electron irradiation on the electrical characteristics of the Au/Aniline blue/p-Si/Al device

An Au/Aniline blue (AB)/p-Si/Al structure has been fabricated and then the effect of electron irradiation (12 MeV electron energy and 5 × 10¹² e⁻ cm⁻² fluence) on the contact parameters of the device has been analysed by using the current-voltage (I-V), capacitance-voltage (C-V), and conductance-voltage (G/w-V) measurements, at room temperature. Since the organic layer creates a physical barrier between the metal and the semiconductor, it has been seen that the AB layer causes an increase in the effective barrier height of the device. Cheung functions, Norde model and conductance method have been used in order to determine the diode parameters. The values of the ideality factor, barrier height and series resistance increased after the electron irradiation. This has been attributed to a decrease in the net ionized dopant concentration that occurred as a result of electron irradiation.