Effect of an organic compound (Methyl Red) interfacial layer on the calculation of characteristic parameters of an Al/Methyl Red/p-Si sandwich Schottky barrier diode

An Al/Methyl Red/p-Si sandwich Schottky barrier diode (SBD) has been fabricated by adding a solution of the organic compound Methyl Red in chloroform onto a p-Si substrate, and then evaporating the solvent. Current-voltage (I-V) measurements of the Al/Methyl Red/p-Si sandwich SBD have been carried out at room temperature and in the dark. The Al/Methyl Red/p-Si sandwich SBD demonstrated rectifying behavior. Barrier height (BH) and ideality factor values of 0.855 eV and 1.19, respectively, for this device have been determined from the forward-bias I-V characteristics. The Al/Methyl Red/p-Si sandwich SBD showed non-ideal I-V behavior with the value of ideality factor greater than unity. The energy distribution of the interface state density determined from I-V characteristics increases exponentially with bias from 3.68 × 10¹² cm^− 2 eV^− 1 at (0.81 − E_v) eV to 9.99 × 10¹³ cm^− 2 eV^− 1 at (0.69 − E_v) eV.     

Capacitance and conductance-frequency characteristics of Au-Sb/p-GaSe:Gd Schottky barrier diode

The Schottky barrier height (SBH) values have been obtained from the reverse bias capacitance-voltage (C-V) characteristics of Au-Sb/p-GaSe:Gd Schottky barrier diode (SBD) in the temperature range of 180-320 K. The forward bias capacitance-frequency (C-f) and conductance-frequency (G-f) measurements of Au-Sb/p-GaSe:Gd SBD have been carried out from 0 to 1.00 V with steps of 0.05 V, whereby the energy distribution of the interface states and their relaxation time have been determined from these characteristics. It has been seen that there is a good agreement between the experimental and theoretical C-f and G-f values. Also, the capacitance values obtained from C-f measurements have shown almost a plateau up to a certain value of frequency, then, have decreased. It has been seen that the interface state density has a very small density distribution range (6.02 × 10¹⁰-6.80 × 10¹⁰ cm⁻² eV⁻¹) in the energy range of (0.21−E_v)-(1.21−E_v) eV with bias from the midgap towards the top of the valence band. The interface state density values calculated for Au-Sb/p-GaSe:Gd SBD are rather low than those given in the literature.     

The determination of interface state energy distribution of the H-terminated Zn/p-type Si Schottky diodes with high series resistance by the admittance spectroscopy

Analysis of Zn/p-Si Schottky diodes (SDs) with high resistivity has been given by admittance spectroscopy. The importance of the series resistance in the determination of energy distribution of interface states and especially their relaxation time in the SDs with high resistivity has been considered. The effect of the series resistance on capacitance-conductance/frequency characteristics has been given by comparing experimental data with theoretical data. The interface state density N_ss from the admittance spectroscopy ranges from 1.0×10¹² cm⁻² eV⁻¹ in 0.720-E_v eV to 2.03×10¹² cm⁻² eV⁻¹ in 0.420-E_v eV. Furthermore, the relaxation time ranges from 4.20×10⁻⁵ s in (0.420-E_v) eV to 3.20×10⁻⁴ s in (0.720-E_v) eV. It has been seen that the interface state density has a very small distribution range (1.0-2.03×10¹² cm⁻² eV⁻¹) that is ascribed to the predominant termination with hydrogen of the silicon surface after HF treatment.     

The analysis of the current–voltage characteristics of the high barrier Au/Anthracene/n-Si MIS devices at low temperatures

The Au/Anthracene/n-Si/Al MIS device was fabricated on the basis of anthracene film covalently bonded to a Si substrate. The MIS device showed Schottky behavior with barrier heights of 0.85 eV and ideality factors of 1.88 at 300 K. The barrier height of the Au/n-Si has increased after deposition of the anthracene layer onto Si. Temperature dependent current–voltage (I–V) measurements were performed on the Au/Anthracene/n-Si/Al MIS diodes in the range 140–300 K. From the temperature dependence of forward bias I–V, the barrier height was observed to increase with temperature. However, the ideality factor decreased with increasing temperature. The values of activation energy (E_a) and Richardson constant (A*) were determined as 0.24 eV and 7.57 × 10⁻⁶ A cm⁻² K⁻² from the slope and the intercept at ordinate of the linear region of Richardson plot, respectively. The increase of the series resistance R_s with the fall of temperature was attributed to lack of free carrier concentration at low temperatures.     

Characterization of electron irradiated GaN n-p diode

Electron-beam irradiated GaN n⁺-p diodes were characterized by deep level transient spectroscopy (DLTS) and optical responsivity measurements. The GaN n⁺-p diode structures were grown by metal organic chemical vapor deposition technique, and the electron irradiation was done by the energies of 1 MeV and 2 MeV with dose of 1 × 10¹⁶ cm^− 2. In DLTS measurement, the defect states of E_c − 0.36 eV and E_c − 0.44 eV in the electron irradiated diodes appeared newly. The optical responsivity of GaN n⁺-p diode was characterized in ultra-violet region, and then the maximum optical responsivity at 350 nm was decreased after electron-beam irradiation.     

Analysis of surface states and series resistance in Au/n-Si Schottky diodes with insulator layer using current-voltage and admittance-voltage characteristics

In order to good interpret the experimentally observed Au/n-Si (metal-semiconductor) Schottky diodes with thin insulator layer (18 Å) parameters such as the zero-bias barrier height (Φ_bo), ideality factor (n), series resistance (R_s) and surface states have been investigated using current-voltage (I-V), capacitance-frequency (C-f) and conductance-frequency (G-f) techniques. The forward and reverse bias I-V characteristics of Au/n-Si (MS) Schottky diode were measured at room temperature. In addition, C-f and G-f characteristics were measured in the frequency range of 1 kHz-1 MHz. The higher values of C and G at low frequencies were attributed to the insulator layer and surface states. Under intermediate forward bias, the semi-logarithmic Ln (I)-V plot shows a good linear region. From this region, the slope and the intercept of this plot on the current axis allow to determine the ideality factor (n), the zero-barrier height (Φ_bo) and the saturation current (I_S) evaluated to 2.878, 0.652 and 3.61 × 10⁻⁷ A, respectively. The diode shows non-ideal I-V behavior with ideality factor greater than unity. This behavior can be attributed to the interfacial insulator layer, the surface states, series resistance and the formation barrier inhomogeneity at metal-semiconductor interface. From the C-f and G-f characteristics, the energy distribution of surface states (N_ss) and their relaxation time (τ) have been determined in the energy range of (E_c − 0.493E_v)-(E_c − 0.610) eV taking into account the forward bias I-V data. The values of N_ss and τ change from 9.35 × 10¹³ eV⁻¹ cm⁻² to 2.73 × 10¹³ eV⁻¹ cm⁻² and 1.75 × 10⁻⁵ s to 4.50 × 10⁻⁴ s, respectively.     

Rectifying pyronine-B/p-type silicon junctions formed by sublimation of pyronine-B

The rectifying junction characteristics of the organic compound pyronine-B film on a p-type Si substrate have been studied. The pyronine-B has been sublimed onto the top of p-Si surface. The barrier height and ideality factor values of 0.79 eV and 1.125 for this structure have been obtained from the forward-bias current–voltage characteristics. The density distribution of the interface states in the inorganic semiconductor bandgap and their relaxation time have been determined from the low-capacitance–frequency characteristics by the Schottky capacitance spectroscopy method. The measurement frequency varies from 90 Hz to 10 MHz. The interface state density N_ss ranges from 2.10×10¹⁰ cm^–2 eV^–1 in (0.79–E_v) eV to 1.16×10¹² cm^–2 eV^–1 in (0.53–E_v) eV. Furthermore, the relaxation time ranges from 1.38×10^–3 s in (0.53–F_V) eV to 7.50×10^–3 s in (0.79–E_V) eV.     

High frequency characteristics of tin oxide thin films on Si

High frequency characteristics of tin oxide (SnO₂) thin films were studied. SnO₂ thin films have been successfully grown on n-type Si (111) substrates by using a spray deposition technique. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of the metal-oxide-semiconductor (Au/SnO₂/n-Si) Schottky diodes were investigated in the high frequency range from 300 kHz to 5 MHz. It has been shown that the interface state density, D_it, ranges from 2.44 × 10¹³ cm⁻² eV⁻¹ at 300 kHz to 0.57 × 10¹³ cm⁻² eV⁻¹ at 5 MHz and exponentially decreases with increasing frequency. The C-V and G/ω-V characteristics confirm that the interface state density and series resistance of the diode are important parameters that strongly influence the electrical parameters exhibited by the metal-oxide-semiconductor structure.     

Electrical characteristics of an organic thin copolymer/p-Si Schottky barrier diode

We have fabricated a poly(aniline-3-methyl thiophene) organic thin material on p-Si substrate by placing a solution of copolymer in acetonitrile on top of a p-Si substrate and then evaporating the solvent. The electrical and interface state density properties of the poly(aniline-3-methyl thiophene) copolymer/p-Si/Al diode have been investigated through methods using current-voltage (I-V), Cheung's, and a modified Norde's function. Good agreement was observed with the values of barrier height as obtained from all of these methods. The diode shows a non-ideal I-V behavior with an ideality factor greater than unity, which could be ascribed to the interfacial layer, interface states and series resistance. The interface state density of diode was determined using the forward-bias I-V characteristic technique at room temperature, and it decreases exponentially with bias from 1.39 × 10¹⁶ cm⁻² eV⁻¹ in (0.06 − E_v) eV to 4.86 × 10¹⁵ cm⁻² eV⁻¹ in (0.51 − E_v) eV.     

Effect of annealing temperature on electrical properties of Au/polyvinyl alcohol/n-InP Schottky barrier structure

In the present work, thin film of polyvinyl alcohol (PVA) is fabricated on n-type InP substrate as an interfacial layer for electronic modification of Au/n-InP Schottky contact. The electrical characteristics of Au/PVA/n-InP Schottky diode are determined at annealing temperature in the range of 100-300 °C by current-voltage (I-V) and capacitance-voltage (C-V) methods. The Schottky barrier height and ideality factor (n) values of the as-deposited Au/PVA/n-InP diode are obtained at room temperature as 0.66 eV (I-V), 0.82 eV (C-V) and 1.32, respectively. Upon annealing at 200 °C in nitrogen atmosphere for 1 min, the barrier height value increases to 0.81 eV (I-V), 0.99 eV (C-V) and ideality factor decreases to 1.18. When the contact is annealed at 300 °C, the barrier height value decreases to 0.77 eV (I-V), 0.96 eV (C-V) and ideality factor increases to 1.22. It is observed that the interfacial layer of PVA increases the barrier height by the influence of the space charge region of the Au/n-InP Schottky junction. The discrepancy between Schottky barrier heights calculated from I-V and C-V measurements is also explained. Further, Cheung's functions are used to extract the series resistance of Au/PVA/n-InP Schottky diode. The interface state density as determined by Terman's method is found to be 1.04 × 10¹² and 0.59 × 10¹² cm^− 2 eV^− 1 for the as-deposited and 200 °C annealed Au/PVA/n-InP Schottky diodes. Finally, it is seen that the Schottky diode parameters changed with increase in the annealing temperature.     

Influence of rapid thermal annealing effect on electrical and structural properties of Pd/Ru Schottky contacts to n-type GaN

Pd/Ru metallization scheme is fabricated on n-GaN as a Schottky contact, and the electrical and structural properties have been investigated as a function of annealing temperature by current–voltage (I–V), capacitance–voltage (C–V), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. As-deposited Ru/Pd/n-GaN contact yielded Schottky barrier height (SBH) of 0.67 eV (I–V) and 0.79 eV (C–V), respectively. Further, it is observed that the Schottky barrier height increases to 0.80 eV (I–V) and 0.96 eV (C–V) for the contact annealed at 300 °C. However, both I–V and C–V measurements indicate that the barrier height slightly decreased when the contacts are annealed at 400 °C and 500 °C. From the above observations, the optimum annealing temperature for Pd/Ru Schottky contact is 300 °C. Norde method is also employed to extract the barrier height of Pd/Ru Schottky contacts which are in good agreement with those obtained by the I–V technique. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 300 °C compared to the as-deposited contact. Based on the XPS and XRD results, the reason for the increase in SBH upon annealing at 300 °C could be attributed to the formation of gallide phases at the Ru/Pd/n-GaN interface vicinity. The AFM results showed that the overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. The above observations reveal that the Pd/Ru Schottky contact is attractive for high-temperature device applications.     

Physical,photoelectrochemical properties of CuIn3Se5 and relevance for hydrogen production

CuIn₃Se₅, prepared by the fusion technique crystallizes in the P-chalcopyrite structure and exhibits n-type conduction ascribed to indium excess. The electrical conductivity follows an Arrhenius-type law with activation energy of 0.35 eV and an electron mobility of 10⁻⁴ cm² V⁻¹ s⁻¹ in conformity with small polaron hopping. The optical gap (1.19 eV), determined from the diffuse reflectance spectrum, is properly matched to the sun spectrum. CuIn₃Se₅ is chemically stable and a corrosion rate of only 1.2 μmol year⁻¹ is found at neutral pH. The slope and the intercept to C⁻² = 0 of the Mott Schottky plot gives respectively an electron density of 3.75 × 10¹⁶ cm⁻³ and a flat band potential of −0.22 V_SCE. The conduction band (−0.74 V_SCE) therefore lies below the potential of H₂O/H₂ couple and as application, H₂ photo-production is successfully achieved over CuIn₃Se₅. The best performance is obtained in S₂O₃²⁻ solution (10⁻² M, pH ∼ 7) with an evolution rate of 0.54 mL g⁻¹ min⁻¹. The conversion efficiency (0.13%) is due to the formation of small depletion width (230 nm) and a large diffusion length compared to a very large penetration depth (∼1 μm). Attempts have been made to improve the photoactivity and the hetero-system CuIn₃Se₅/WO₃ is compared favorably with respect to CuIn₃Se₅. The photoactivity is ascribed to electrons transfer from the sensitizer CuIn₃Se₅-conduction band (CB), acting as electrons pump, to WO₃-CB (−0.4 V_SCE) resulting in the enhanced water reduction.     

Photovoltaic and interface state density properties of the Au/n-GaAs Schottky barrier solar cell

The electrical and photovoltaic properties of the Au/n-GaAs Schottky barrier diode have been investigated. From the current-voltage characteristics, the electrical parameters such as, ideality factor and barrier height of the Au/n-GaAs diode were obtained to be 1.95 and 0.86 eV, respectively. The interface state distribution profile of the diode as a function of the bias voltage was extracted from the capacitance-voltage measurements. The interface state density D_it of the diode was found to vary from 3.0 × 10¹¹ eV⁻¹ cm⁻² at 0 V to 4.26 × 10¹⁰ eV⁻¹cm⁻² at 0.5 V. The diode shows a non-ideal current-voltage behavior with the ideality factor higher than unity due to the interfacial insulator layer and interface states. The diode under light illumination exhibits a good photovoltaic behavior. This behavior was explained in terms of minority carrier injection phenomenon. The photovoltaic parameters, such as open circuit voltage and short circuit current density were obtained to be 362 mV and J_sc = 28.3 μA/cm² under AM1, respectively.     

Electrical and structural characterization of AlGaN/GaN field-effect transistors with recessed gate

Performance of AlGaN/GaN heterostructure field-effect transistors (HFETs) with recessed gate was investigated and compared with non-recessed counterparts. Optimal dry etch conditions by plasma assisted Ar sputtering were found for ∼6 nm gate recess of a 20 nm thick AlGaN barrier layer. A decrease of the residual strain after the gate recessing (from −0.9 GPa to −0.68 GPa) was evaluated from the photoluminescence measurement. The saturation drain current at the gate voltage V_G = 1 V decreased from 1.05 A/mm to 0.85 A/mm after the recessing. The gate voltage for a maximal transconductance (240−250 mS/mm) has shifted from −3 V for non-recessed HFETs to −0.2 V for recessed counterparts. Similarly, the threshold voltage increased after the gate recessing. A decrease of the sheet charge density from 1 × 10¹³ cm⁻² to 4 × 10¹² cm⁻² at V_G = 0 V has been evaluated from the capacitance measurements. The RF measurements yielded a slight increase of the cut-off frequencies after the gate recessing. All these indicate that the gate recessing is a useful tool to optimize the AlGaN/GaN HFET performance for high-frequency applications as well as for the preparation of normally-off devices.     

Temperature-dependent properties of Pd/GaN Schottky type hydrogen sensors with Cl2 plasma surface treatments

Temperature-dependent hydrogen sensing properties of Pd/GaN Schottky type sensors with different Cl₂ plasma surface treated times are studied and demonstrated. The sensing behaviors are studied in terms of Schottky barrier height variation Δφ_B, sensing response S_r, and transient-state response times. The highest sensing response (S_r) values of 7.1 × 10⁴ and 2.12 × 10⁵ are obtained in forward- and reverse-bias voltages, respectively, upon exposure to a 10,000 ppm H₂/air gas at 30 °C. In addition, a correspondingly large Schottky barrier height variation Δφ_B of 0.38 eV is found. This could be attributed to the effective dissociation of hydrogen molecules due to a rougher Pd surface and lower baseline current. Moreover, the studied devices with Cl₂ plasma surface treatment have a stable and widespread reverse voltage operation regime. From transient-state behaviors measurement, the studied device with a 30 s plasma surface treatment shows the overshooting phenomenon and fast response (recovery) time of 4 (5) s.     

Fabrication of p-type ZnO nanowires based heterojunction diode

Vertically aligned p-type ZnO (Li–N co-doped) nanowires have been synthesized by hydrothermal method on n-type Si substrate. X-ray diffraction pattern indicated a strong peak from (0 0 0 2) planes of ZnO. The appearance of a strong peak at 437 cm⁻¹ in Raman spectra was attributed to E₂ mode of ZnO. Fourier transformed infrared studies indicated the presence of a distinct characteristic absorption peaks at 490 cm⁻¹ for ZnO stretching mode. Compositional studies revealed the formation of Li–N co-doped ZnO, where Li was bonded with both O and N. The junction properties of p-type ZnO nanowires/n-Si heterojunction diodes were evaluated by measuring I–V and C–V characteristics. I–V characteristics exhibited the rectifying behavior of a typical p–n junction diode.     

Deep level centers in InGaN/GaN heterostructure grown on sapphire and free-standing GaN

Deep level transient spectroscopy has been used to characterize the deep levels in InGaN/GaN grown on sapphire substrate as well as on free-standing GaN. The deep levels at E_c − E_t ∼ 0.17-0.23 eV and E_c − E_t ∼ 0.58-0.62 eV have been detected in our samples which are present in GaN samples reported by others. These two deep levels have been attributed by us to threading dislocations as they exhibit logarithmic capture kinetic behavior and are found to be substantially reduced in its trap concentration (∼ from 10¹⁴ to 10¹² cm^− 2) in GaN grown on free-standing GaN template. Other than the two deep levels, an additional level at E_c − E_t ∼ 0.40-0.42 eV has been identified in both samples, which is believed to be related to In segregation. AFM image shows region of pits formation in InGaN epilayer for sample grown on u-GaN using sapphire substrate while the latter gives a much smoother morphology. From the X-ray diffraction space mapping, the mosaicity of the sample structure for both samples were studied. Dislocations do not play a significant role in the structural properties of InGaN grown on free-standing GaN since the FWHM based on the Δ ω is relatively small (± 0.15°) in the case of InGaN/GaN on free-standing GaN substrate as compared to that on sapphire (± 0.35°). The wider spread in Δω-2θ value for InGaN layer on free-standing GaN also suggested the effect of compositional pulling with increasing InGaN layer thickness.     

Electrical characterisation of stearic acid/calix[4]amine Langmuir–Blodgett thin film

Within this work we deposited 16 monolayers of stearic acid alternated with 15 monolayers of calix[4]amine to form a non-centrosymmetric Langmuir–Blodgett (LB) thin film onto an aluminized (50 nm coated) glass microscopic slide. Dielectric constant and dielectric loss for the film were determined using C-f and tan (δ-f) measurements. The value of the pyroelectric figure of merit was determined as 1.73 μC m⁻² K⁻¹. To elucidate the conduction mechanism of stearic acid/calix[4]amine LB film, DC current–voltage measurements between −4 and +4 V were carried out. The I(V) behaviour shows a symmetrical and highly non-linear behaviour. Analysis of this behaviour of the stearic acid/calix[4]amine LB film showed a conductivity value of 1.12 × 10⁻¹³ S m⁻¹ for ohmic region. The exponential part of I(V) dependence obeyed the Schottky conduction mechanism with a barrier height of 1.67 eV. This LB film structure shows a typical insulating behaviour for low voltage values and the Schottky effect becomes dominant when the voltage increases. The frequency dependence of conductivity shows a power law relationship between conductance and frequency.     

Electrical characteristics of Au/n-GaAs Schottky barrier diodes with and without SiO2 insulator layer at room temperature

In this study, our main goal is fabricated with and without insulator layer Au/n-GaAs Schottky barrier diodes (SBDs) to explain whether or not the insulator layer is effective on some electric parameters such as Φ_B, n, N_ss, and R_s. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-semiconductor (Au/n-GaAs) are investigated and compared with metal-insulator-semiconductor (Au/SiO₂/n-GaAs) Schottky diodes. From the room temperature I-V characteristics of these devices, the main electrical parameters such as, ideality factor (n) and zero bias barrier height (Φ_bo) values of 1.25 and 0.73 eV for Au/n-GaAs, and 1.51 and 0.75 eV for Au/SiO₂/n-GaAs, were obtained. The interface distribution profile (N_ss) as a function of (E_c − E_ss) was extracted from the forward-bias I-V measurements by taking into account the bias dependence of the effective barrier height (Φ_e) and series resistance (R_s) for the Schottky diodes. The N_ss values obtained taking into account the series resistance values are lower than those obtained without considering the series resistance. The diodes show non-ideal I-V behavior with ideality factor greater than unity. This behavior is attributed to the interfacial insulator layer and the interface states. 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 metal-semiconductor and metal-insulator-semiconductor Schottky diodes.     

Electrical transport characteristics of Au/n-GaN Schottky diodes

The current–voltage measurements were performed in the temperature range (80–300 K) on Au/ n-GaN Schottky barrier type diodes. The Schottky diode shows non-ideal I(V_G) behaviour with ideality factors n equals to 1.18 and 1.81 at 300 K and 80 K, respectively, and are thought to have a metal-interface layer-semiconductor configuration. Under forward bias and for T ≥ 200 K, the electrical current transport was controlled by the thermionic emission (TE) process. However, for T ≤ 200 K, The current was controlled by the thermionic field emission (TFE). The characteristic energy E₀₀ = 3.48 meV was obtained from the I(V_G, T) measurements and agreed very well with the value of E₀₀ = 3.62 meV calculated theoretically. The zero-bias barrier height ϕ_B0 determined from the I(V_G) measurements was 0.84 eV at 300 K and decreases to 0.49 eV at 80 K.