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.     

Characterization of current-voltage (I-V) and capacitance-voltage-frequency (C-V-f) features of Al/SiO2/p-Si (MIS) Schottky diodes

The current-voltage (I-V) characteristics of metal-insulator-semiconductor Al/SiO₂/p-Si (MIS) Schottky diodes were measured at room temperature (300 K). In addition, capacitance-voltage-frequency (C-V-f) characteristics are investigated by considering the interface states (N_ss) at frequency range 100 kHz to 1 MHz. The MIS Schottky diode having interfacial insulator layer thickness of 33 Å, calculated from the measurement of the insulator capacitance in the strong accumulation region. At each frequency, the measured capacitance decreases with increasing frequency due to a continuous distribution of the interface states. From the I-V characteristics of the MIS Schottky diode, ideality factor (n) and barrier height (Φ_b) values of 1.766 and 0.786 eV, respectively, were obtained from a forward bias I-V plot. In addition, the interface states distribution profile as a function of (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_e) for the Schottky diode. The diode shows non-ideal I-V behaviour with ideality factor greater than unity. This behaviour is attributed to the interfacial insulator layer, the interface states and barrier inhomogeneity of the device. As expected, the C-V curves gave a barrier height value higher than those obtained from I-V measurements. This discrepancy is due to the different nature of the I-V and C-V measurement techniques.     

Pentacene/n-Si heterojunction diodes and photovoltaic devices investigated by I-V and C-V measurements

The forward and reverse current density-voltage (J-V) and capacitance-voltage (C-V) characteristics of pentacene/n⁻-silicon heterojunction diodes were investigated to clarify the carrier conduction mechanism at the organic/inorganic heterojunction. Current rectification characteristics of the pentacene/n⁻-Si junctions can be explained by a Schottky diode model with an interfacial layer. The diode parameters such as Schottky barrier height and ideality factor were estimated to be 0.79-1.0 eV and 2.4-2.7, respectively. The C-V analysis suggests that the depletion layer appears selectively in the n⁻-Si layer with a thickness of 1.47 μm from the junction with zero bias and the diffusion potential was estimated at 0.30 eV at the open-circuit condition. The present heterojunction allows the photovoltaic operation with power conversion efficiencies up to 0.044% with a simulated solar light exposure of 100 mW/cm².     

Annealing temperature effect on electrical and structural properties of Cu/Au Schottky contacts to n-type GaN

Schottky contacts were fabricated on n-type GaN using a Cu/Au metallization scheme, and the electrical and structural properties have been investigated as a function of annealing temperature by current-voltage (I-V), capacitance-voltage (C-V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements. The extracted Schottky barrier height of the as-deposited contact was found to be 0.69 eV (I-V) and 0.77 eV (C-V), respectively. However, the Schottky barrier height of the Cu/Au contact slightly increases to 0.77 eV (I-V) and 1.18 eV (C-V) when the contact was annealed at 300 °C for 1 min. It is shown that the Schottky barrier height decreases to 0.73 eV (I-V) and 0.99 eV (C-V), 0.56 eV (I-V) and 0.87 eV (C-V) after annealing at 400 °C and 500 °C for 1 min in N₂ atmosphere. Norde method was also used to extract the barrier height of Cu/Au contacts and the values are 0.69 eV for the as-deposited, 0.76 eV at 300 °C, 0.71 eV at 400 °C and 0.56 eV at 500 °C which are in good agreement with those obtained by the I-V method. Based on Auger electron spectroscopy and X-ray diffraction results, the formation of nitride phases at the Cu/Au/n-GaN interface could be the reason for the degradation of Schottky barrier height upon annealing at 500 °C.     

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.     

Current transport mechanisms and deep level transient spectroscopy of Au/n-Si Schottky barrier diodes

The temperature-dependent electrical characteristics of the Au/n-Si Schottky diodes have been studied in the temperature range of 40-300 K. Current density-voltage (J-V) characteristics of these diodes have been analyzed on the basis of thermionic emission theory with Gaussian distribution model of barrier height. The basic diode parameters such as rectification ratio, ideality factor and barrier height were extracted. Under a reverse bias, the conduction process at low voltage is determined by Schottky emission over a potential barrier but at higher voltage the Poole Frenkel effect is observed. The capacitance-voltage (C-V) features of the Au/n-Si Schottky diodes were characterized in the high frequency of 1 MHz. The barrier heights values obtained from the J-V and C-V characteristics have been compared. It has been seen that the barrier height value obtained from the C-V measurements is higher than that obtained from the J-V measurements at various temperatures. Possible explanations for this discrepancy are presented. Deep level transient spectroscopy (DLTS) has been used to investigate deep levels in Au/n-Si. Three electron trap centers, having different emission rates and activation energies, have been observed. It is argued that the origin of these defects is of intrinsic nature. A correlation between C-V and DLTS measurements is investigated.     

Thermally annealed Ni/n-GaAs(Si)/In Schottky barrier diodes

We have identically prepared as many as eight Ni/n-GaAs/In Schottky barrier diodes (SBDs) using an n-type GaAs substrate with a doping density of about 7.3 × 10¹⁵ cm⁻³. The thermal stability of the Ni/n-GaAs/In Schottky diodes has been investigated by means of current-voltage (I-V) techniques after annealed for 1 min in N₂ atmosphere from 200 to 700 °C. For Ni/n-GaAs/In SBDs, the Schottky barrier height Φ_b and ideality factor n values range from 0.853 ± 0.012 eV and 1.061 ± 0.007 (for as-deposited sample) to 0.785 ± 0.002 eV and 1.209 ± 0.005 (for 600 °C annealing). The ideality factor values remained about unchanged up to 400 °C annealing. The I-V characteristics of the devices deteriorated at 700 °C annealing.     

The current-voltage-temperature characteristics of Al/NPB/p-Si contact

The current-voltage (I-V) characteristics of the Al/NPB/p-Si contact shows rectifying behavior with a potential barrier formed at the contact interface. The barrier height and ideality factor values of 0.65 eV and 1.33 are measured at the forward bias of the diode. The barrier height of the Al/NPB/p-Si diode at room temperature is larger that (∼0.58 eV) of conventional Al/p-Si diode. It reveals the NPB organic film control the carrier transport of the diode at the contact interface. The temperature effect on the I-V measurement is also performed to reveal the junction characteristics. The ideality factor of the Al/NPB/p-Si contact increases with decreasing temperature. And the barrier height decreases with decreasing temperature. The effects are due to the existence of the interface states and the inhomogeneous of the barrier at the junction.     

Electrical analysis of organic dye-based MIS Schottky contacts

In this work, we prepared metal/interlayer/semiconductor (MIS) diodes by coating of an organic film on p-Si substrate. Metal(Al)/interlayer(Orange GOG)/semiconductor(p-Si) MIS structure had a good rectifying behavior. By using the forward-bias I-V characteristics, the values of ideality factor (n) and barrier height (BH) for the Al/OG/p-Si MIS diode were obtained as 1.73 and 0.77 eV, respectively. It was seen that the BH value of 0.77 eV calculated for the Al/OG/p-Si MIS diode was significantly larger than the value of 0.50 eV of conventional Al/p-Si Schottky diodes. Modification of the potential barrier of Al/p-Si diode was achieved by using thin interlayer of the OG organic material. This was attributed to the fact that the OG organic interlayer increased the effective barrier height by influencing the space charge region of Si. The interface-state density of the MIS diode was found to vary from 2.79 × 10¹³ to 5.80 × 10¹² eV⁻¹ cm⁻².     

Electrical characteristics and inhomogeneous barrier analysis of Au-Be/p-InSe:Cd Schottky barrier diodes

We have identically prepared Au-Be/p-InSe:Cd Schottky barrier diodes (SBDs) (21 dots) on the InSe:Cd substrate. The electrical analysis of Au-Be/p-InSe:Cd structure has been investigated by means of current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements at 296 K temperature in dark conditions. The effective barrier heights and ideality factors of identically fabricated Au-Be/p-InSe:Cd SBDs have been calculated from their experimental forward bias current-voltage (I-V) characteristics by applying a thermionic emission theory. The BH values obtained from the I-V characteristics have varied between 0.74 eV and 0.82 eV with values of ideality factors ranging between 1.49 and 1.11 for the Au-Be/p-InSe:Cd SBDs. It has been determined a lateral homogeneous barrier height value of approximately 0.82 eV for these structures from the experimental linear relationship between barrier heights and ideality factors. The Schottky barrier height (SBH) value has been obtained from the reverse-bias C-V characteristics of Au-Be/p-InSe:Cd SBD for only one diode. At high currents in the forward direction, the series resistance effect has been observed. The value of series resistance has been determined from I-V measurements using Cheung’s and Norde’s methods.     

Structural, electrical and magnetic characterizations of Ni/Cu/p-Si Schottky diodes prepared by liquid phase epitaxy

In this paper, we have investigated the structural, electrical and magnetic characterizations of Ni/Cu/p-Si Schottky diode prepared by liquid phase epitaxy (LPE). Current density-voltage (J-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements were performed to determine the conduction mechanisms as well as extracting the important diode parameters. Rectifying properties were obtained, which definitely of the Schottky diode type. At low voltages, (0 < V ? 0.4 V), current density in the forward direction was found to obey the diode equation, while for higher voltages, (0.5 < V ? 1.5 V), conduction was dominated by a space-charge-limited conduction (SCLC) mechanism. Analysis of the experimental data under reverse bias suggests a transition from electrode-limited to a bulk-limited conduction process for lower and higher applied voltages, respectively. Diode parameters such as, the built-in potential, V_b, the carrier concentration, N, the width of the depletion layer, W, of the Ni/Cu/p-Si Schottky diode were obtained from the C-V measurements at high frequency (1 MHz). The capacitance-frequency measurements showed that the values of capacitance were highly frequency dependent at low frequency region but independent at high frequencies. The Ni/Cu/p-Si Schottky diode showed magnetic properties due to the effect of Ni in the heterostructure.     

Schottky barrier height modification in Au/n-type 6H-SiC structures by PbS interfacial layer

We have prepared the Au/PbS/n-6H-SiC Schottky diodes with interface layer and the reference Au/n-6H-SiC/Ni Schottky diodes without interface layer to realize Schottky barrier height (SBH) modification in the Au/SiC Schottky diodes. The BH reduction has been succeeded by the PbS interlayer to modify the effective BH by influencing the space charge region of the SiC. The PbS thin layer on the SiC was formed by the vacuum evaporation. The SBH values of 0.97 and 0.89 eV for the samples with and without the interfacial PbS layer were obtained from the forward bias current-voltage (I-V) characteristics. X-ray diffraction (XRD) study was carried out to determine the structural formation of the PbS on SiC. The reduction of the BH in the Au/PbS/n-6H-SiC Schottky diodes has been attributed to the fact that the interface states have a net positive interface charge in metal/n-type semiconductor contact, and thus the positive space charge Q_sc in the Au/PbS/n-6H-SiC Schottky diodes becomes smaller than if the interface state charges Q_ss were absent. The experimental carrier concentration value of 4.73 × 10¹⁷ cm⁻³ obtained from the forward and reverse bias capacitance-voltage characteristics for the Au/PbS/n-6H-SiC contacts is lower than the value of 5.52 × 10¹⁷ cm⁻³ obtained for the reference diode, and this is an evidence of the reduction of the BH by the modification of the space charge density of the SiC.     

The electrical characteristics of Al/p-InP Schottky contacts

In this study, it has been investigated the electrical characteristics of identically prepared Al/p-InP Schottky diodes. The barrier heights (BHs) and ideality factors of all devices have been calculated from the electrical characteristics. Although the diodes were all identically prepared, there was a diode-to-diode variation: the effective barrier heights ranged from 0.83 ± 0.01 to 0.87 ± 0.01 eV, and the ideality factors ranged from 1.13 ± 0.02 to 1.21 ± 0.02. The barrier height vs. ideality factor plot has been plotted for the devices. Lateral homogeneous BH was calculated as a value of 0.86 eV from the observed linear correlation between BH and ideality factor, which can be explained by laterally inhomogeneities of BHs. The values of barrier height and free carrier concentration yielded from the reverse bias capacitance-voltage (C-V) measurements ranged from 0.86 ± 0.04 to 1.00 ± 0.04 eV and from (3.47 ± 0.39) × 10¹⁷ to (4.90 ± 0.39) × 10¹⁷ cm⁻³, respectively. The mean barrier height and mean acceptor doping concentration from C-V characteristics have been calculated as 0.91 eV and 3.99 × 10¹⁷ cm⁻³, respectively.     

Al contacts to nanoroughened p-GaN

Nanoroughening of a p-GaN surface using nanoscale Ni islands as an etch mask was utilized to investigate the feasibility for the flip-chip configuration light-emitting diodes (LEDs) using an Al-based reflector. Improved ohmic characteristics were found for the nanoroughened sample. A specific contact resistivity of 8.9×10⁻² Ω cm² and a reflectance of 82% at 460 nm were measured for the nanoroughened Al contact. The Schottky barrier heights were decreased from 0.81 eV (I-V) and 0.84 eV (Norde) for the Al contact to 0.70 eV (I-V) and 0.69 eV (Norde) for the nanoroughened Al contact. The barrier height reduction may be attributed to enhanced tunneling and the increased contact area due to the nanoroughening. This work suggests that the ohmic contact characteristics and the light extraction efficiency may be improved further with a well-defined nanopatterned p-GaN layer.     

Ta/Si Schottky diodes fabricated by magnetron sputtering technique

Electrical properties of Ta/n-Si and Ta/p-Si Schottky barrier diodes obtained by sputtering of tantalum (Ta) metal on semiconductors have been investigated. The characteristic parameters of these contacts like barrier height, ideality factor and series resistance have been calculated using current voltage (I-V) measurements. It has seen that the diodes have ideality factors more than unity and the sum of their barrier heights is 1.21 eV which is higher than the band gap of the silicon (1.12 eV). The results have been attributed the effects of inhomogeneities at the interface of the devices and native oxide layer. In addition, the barrier height values determined using capacitance-voltage (C-V) measurements have been compared the ones obtained from I-V measurements. It has seen that the interface states have strong effects on electrical properties of the diodes such as C-V and R_s-V measurements.     

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.     

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.     

Analysis of interface states and series resistance of MIS Schottky diodes using the current-voltage (I-V) characteristics

The purpose of this paper is to analyze interface states in Al/SiO₂/p-Si (MIS) Schottky diodes and determine the effect of SiO₂ surface preparation on the interface state energy distribution. The current-voltage (I-V) characteristics of MIS Schottky diodes were measured at room temperature. From the I-V characteristics of the MIS Schottky diode, ideality factor (n) and barrier height (Φ_B) values of 1.537 and 0.763 eV, respectively, were obtained from a forward bias I-V plot. In addition, the density of interface states (N_ss) as a function of (E_ss-E_v) was extracted from the forward bias I-V measurements by taking into account both the bias dependence of the effective barrier height (Φ_e), n and R_s for the MIS Schottky diode. The diode shows non-ideal I-V behaviour with ideality factor greater than unity. In addition, the values of series resistance (R_s) were determined using Cheung’s method. The I-V characteristics confirmed that the distribution of N_ss, R_s and interfacial insulator layer are important parameters that influence the electrical characteristics of MIS Schottky diodes.     

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.