Correlation between barrier heights and ideality factors of Cd/n-Si and Cd/p-Si Schottky barrier diodes

Our goal is to experimentally investigate whether or not the effective Schottky barrier heights (SBHs) and ideality factors obtained from the current-voltage (I-V) and capacitance-voltage (C-V) characteristics differ from diode to diode even if the samples were identically prepared. For this purpose, we prepared Cd/n-Si (33 dots) and Cd/p-Si (15 dots) diodes. The SBH for the Cd/n-Si diodes ranged from 0.701 to 0.605 eV, and ideality factor n from 1.913 to 1.213. Φ_b value for the Cd/p-Si diodes ranged from 0.688 to 0.730 eV, and ideality factor n value from 1.473 to 1.040. The experimental SBH distributions obtained from the C⁻²-V and I-V characteristics were fitted by a Gaussian function and their mean SBH values were calculated. Furthermore, the laterally homogeneous barrier heights were also computed from the extrapolation of the linear plot of experimental barrier heights versus ideality factors.     

Temperature-Dependent Current–Voltage (I–V) and Capacitance–Voltage (C–V) Characteristics of Ni/Cu/n-InP Schottky Barrier Diodes

The current-voltage (I–V) and capacitance-voltage (C–V) characteristics of Ni/Cu/n-InP Schottky barrier diodes are studied over a wide temperature range, from 210 K to 420 K. The I–V characteristics display anomalous thermal behavior. The apparent barrier height decays, and the ideality factor grows at low temperatures, and the series resistances resulting from Cheung’s and Norde’s procedures are markedly temperature dependent. The nonlinearity of the Richardson plot and the strong temperature dependence of the Schottky-barrier parameters indicate that the interface is spatially inhomogeneous. Plots of the zero-bias barrier height as a function of 1/(2kT) points to a Gaussian distribution of barrier heights with 0.90 eV mean height and 0.014 eV standard deviation. When this distribution is accounted for, a Richardson of 6.5 A/(cm K)² results, relatively close to the 9.4/(cm K)² predicted by theory. We conclude that, combined with a Gaussian distribution of barrier heights, the thermionic-emission mechanism explains the temperature-dependent I–V and C–V characteristics of the studied Schottky-barrier diodes.     

Barrier height inhomogeneities in InN/GaN heterostructure based Schottky junctions

The electrical transport properties of InN/GaN heterostructure based Schottky junctions were studied over a wide temperature range of 200-500 K. The barrier height and the ideality factor were calculated from current-voltage (I-V) characteristics based on thermionic emission (TE), and found to be temperature dependent. The barrier height was found to increase and the ideality factor to decrease with increasing temperature. The observed temperature dependence of the barrier height indicates that the Schottky barrier height is inhomogeneous in nature at the heterostructure interface. Such inhomogeneous behavior was modeled by assuming the existence of a Gaussian distribution of barrier heights at the heterostructure interface.     

Comparison of electrical parameters of Zn/p-Si and Sn/p-Si Schottky barrier diodes

In this study, current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-semiconductor (MS) Zn/p-Si and Sn/p-Si Schottky diodes, with high resistivity silicon structures, are investigated. The parameters of series resistance (R_S), the ideality factor (n) and the barrier height (Φ_b) are determined by performing different plots from the forward bias current-voltage (I-V) and reverse bias capacitance-voltage (C-V) characteristics. Thus, the barrier heights (Φ_b) for the Si Schottky diodes obtained between 0.725 and 1.051 eV, the ideality factor (n) between 1.043 and 1.309, and the series resistance (R_S) between 12.594 and 12.950 kΩ. The energy distribution of interface states density was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. It was concluded that the density of interface states in the considered energy range are in close agreement with each other values obtained for Zn/p-Si and Sn/p-Si Schottky diodes.     

Influence of surface cleaning effects on properties of Schottky diodes on 4H-SiC

Ir/4H-SiC and IrO₂/4H-SiC Schottky diodes are reported in terms of different methods of surface pretreatment before contact deposition. In order to find the effect of surface preparation processes on Schottky characteristics the SiC wafers were respectively cleaned using the following processes: (1) RCA method followed by buffered HF dip. Next, the surface was oxidized (5.5 nm oxide) using a rapid thermal processing reactor chamber and circular geometry windows were opened in the oxide layer before metallization deposition; (2) the same as sequence (1) but with an additional in situ sputter etching step before metallization deposition; (3) cleaning in organic solvents followed by buffered HF dip. The I-V characteristics of Schottky diodes were analyzed to find a correlation between extracted parameters and surface treatment. The best results were obtained for the sequence (1) taking into account theoretical value of Schottky barrier height. The contacts showed excellent Schottky behavior with ideality factors below 1.08 and barrier heights of 1.46 eV and 1.64 eV for Ir and IrO₂, respectively. Very promising results were obtained for samples prepared using the sequence (2) taking into account the total static power losses because the modified surface preparation results in a decrease in the forward voltage drop and reverse leakage current simultaneously. The contacts with ideality factor below 1.09 and barrier height of 1.02 eV were fabricated for Ir/4H-SiC diodes in sequence (2).     

Thermal activation of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height

This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I--V--T curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage V_j, excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, V_j needs to be smaller than the barrier height Ф. With proper scheme of series resistance connection where the condition of V_j > Ф is guaranteed, I--V--T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I--V--T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I--V--T curves only for small barrier height inhomogeneity.     

Schottky barrier and pn-junctionI/V plots — Small signal evaluation

This paper proposes and examines three different plots for the determination of the saturation current, the ideality factor, and the series resistance of Schottky diodes and solar cells from the measurement of a single current (I)/voltage(V) curve. All three plots utilize the small signal conductance and avoid the traditional Norde plot completely. A test reveals that the series resistance and the barrier height of a test diode can be determined with an accuracy of better than 1%. Finally it is shown that a numerical agreement between measured and fittedI/V curves is generally insufficient to prove the physical validity of current transport models.     

Determination of the laterally homogeneous barrier height of thermally annealed and unannealed Au/p-InP/Zn-Au Schottky barrier diodes

We have identically prepared Au/p-InP Schottky barrier diodes (SBDs). The diodes were annealed up to 400 °C thermally. The barrier height (BH) for the as-deposited Au/p-InP/Zn-Au SBDs from the current-voltage characteristics have varied from 0.58 to 0.72 eV, and ideality factor n from 1.14 to 1.47. The BH for the annealed SBDs from the current-voltage characteristics have varied from 0.76 to 0.82 eV, and ideality factor n from 1.17 to 1.39. As a result of the thermal annealing, it has been seen that the BH values of the annealed SBDs are larger than those of the as-deposited SBDs. We have determined a lateral homogeneous BH value of 0.72 eV for the as-deposited Au/p-InP SBD from the experimental linear relationship between barrier heights and ideality factors, and a value of 0.85 eV for the annealed Au/p-InP SBD. The increase of 0.13 eV in the BH value by means of 400 °C annealing has been ascribed to the formation of the excess charges that electrically actives on the semiconductor surface.     

Current transport mechanism in Al/Si3N4/p-Si (MIS) Schottky barrier diodes at low temperatures

The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of metal-insulator-semiconductor (Al/Si₃N₄/p-Si) Schottky barrier diodes (SBDs) were measured in the temperature range of 80-300 K. By using the thermionic emission (TE) theory, the zero-bias barrier height Φ_B0 calculated from I-V characteristics was found to increase with increasing temperature. Such temperature dependence is an obvious disagreement with the negative temperature coefficient of the barrier height calculated from C-V characteristics. Also, the ideality factor decreases with increasing temperature, and especially the activation energy plot is nonlinear at low temperatures. Such behaviour is attributed to Schottky barrier inhomogeneties by assuming a Gaussian distribution of barrier heights (BHs) at interface. We attempted to draw a Φ_B0 versus q/2kT plot to obtain evidence of a Gaussian distribution of the BHs, and the values of Φ_Bo = 0.826 eV and α_o = 0.091 V for the mean barrier height and standard deviation at zero-bias, respectively, have been obtained from this plot. Thus, a modified ln(I_o/T²) − q²σ_o²/2(kT)² versus q/kT plot gives Φ_B0 and Richardson constant A^* as 0.820 eV and 30.273 A/cm² K², respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 30.273 A/cm² K² is very close to the theoretical value of 32 A/cm² K² for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/Si₃N₄/p-Si Schottky barrier diodes can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights. In addition, the temperature dependence of energy distribution of interface state density (N_SS) profiles was determined from the forward I-V measurements by taking into account the bias dependence of the effective barrier height and ideality factor.     

Carrier recombination and high-barrier Schottky diodes on silicon

Small-area high-barrier Schottky diodes have a very high dynamic resistance. Consequently, special care is needed when measuring the current-voltage characteristic of such diodes. The reported observation of carrier recombination in the depletion layer of high-barrier IrSi/Si Schottky diodes at room temperature is shown to be due to instrumental loading of the diodes. Careful measurements show that carrier recombination is observed only below 200 K and is dependent on the dimension of the diode.     

The effect of series resistance on capacitance-voltage characteristics of Schottky barrier diodes

The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the Ti/p-Si Schottky barrier diodes (SBDs) have been investigated taking into account the effect of the interface states and series resistance of the device. The forward C-V measurements have been carried out in the range frequency of 0.3-2 MHz (at six different frequencies). It is seen that the forward C-V plots exhibit anomalous peaks in the presence of a series resistance. It has been experimentally determined that the peak positions in the C-V plot shift towards lower voltages and the peak value of the capacitance decreases with increasing frequency. In addition to, the effect of series resistance on the capacitance is found appreciable at higher frequencies due to the capacitance decreases with increasing frequency.     

Effects of chemical treatment on barrier height and ideality factors of Au/GaN Schottky diodes

We have studied Au/n-GaN Schottky barrier diodes. GaN surfaces have been prepared by cleaning in HCl and (NH₄)₂S prior to metal deposition. The zero-biased barrier heights and ideality factors obtained from the current-voltage characteristics differ from diode to diode, although all the samples were prepared identically. The statistical analysis for the reverse bias C-V data yielded mean value of (1.35±0.04) eV for Schottky barrier height of HCl treated sample and (1.20±0.03) eV for (NH₄)₂S sample, where 9 dots were considered from each cleaning method. It was found that the barrier height values obtained from the C⁻²-V (1.43 eV) and I-V characteristics (0.89 eV) are different from each other by 0.54 eV. The inhomogeneous barrier heights were found to be related to the effect of the high series resistance on diode parameters (Akkiliç et al., 2004) [1].     

The barrier height inhomogeneity in Al/p-Si Schottky barrier diodes with native insulator layer

The current-voltage (I-V) characteristics of Al/p-Si Schottky barrier diodes (SBDs) with native insulator layer were measured in the temperature range of 150-375 K. The estimated zero-bias barrier height Φ_B0 and the ideality factor n assuming thermionic emission (TE) theory show strong temperature dependence. Evaluation of the forward I-V data reveals an increase of zero-bias barrier height Φ_B0 but decrease of ideality factor n with increase in temperature. The conventional Richardson plot exhibits non-linearity below 250 K with the linear portion corresponding to activation energy of 0.41 eV and Richardson constant (A^*) value of 1.3 × 10⁻⁴ A cm⁻² K⁻² is determined from intercept at the ordinate of this experimental plot, which is much lower than the known value of 32 A cm² K² for holes in p-type Si. Such behavior is attributed to Schottky barrier inhomogene ties by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Also, Φ_B0 versus q/2kT plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Φ_B0 = 1.055 eV and σ₀ = 0.13 V for the mean BH and zero-bias standard deviation have been obtained from this plot, respectively. Thus, the modified versus q/kT plot gives Φ_B0 and A^* as 1.050 eV and 40.08 A cm⁻² K⁻², respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 40.03 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.     

镍的锗化物与锗肖特基接触的工艺与特性

本文利用在n型Ge衬底上溅射金属Ni，然后在不同温度下氮气中退火的方法制备了Ni的锗化物肖特基二极管。X射线衍射（XRD）分析表明在Ge衬底上形成了一层Ni的锗化物。研究了退火温度对Ni的锗化物肖特基二极管电学特性的影响。实验结果表明具有典型I-V整流特性的肖特基二极管被获得，在300oC中退火的肖特基二极管的开关比最高。通过C-V方法提取了肖特基二极管的肖特基势垒高度。     

Current transport in Pd2Si/n-Si(100) Schottky barrier diodes at low temperatures

The forward current-voltage (I–V) characteristics of Pd₂Si/n-Si(100) Schottky barrier diodes are shown to follow the Thermionic Emission-Diffusion (TED) mechanism in the temperature range of 52-295 K. The evaluation of the experimentalI–V data reveals a decrease of the zero-bias barrier height ( _b0) and an increase of the ideality factor () with decreasing temperature. Further, the changes in _b0 and become quite significant below 148 K. It is demonstrated that the findings cannot be explained on the basis of tunneling, generation-recombination and/or image force lowering. Also, the concepts of flat band barrier height and T ₀-effect fail to account for the temperature dependence of the barrier parameters. The 1n(I _s /T ²) vs 1/T plot exhibits nonlinearity below 185 K with the linear portion corresponding to an activat ion energy of 0.64 eV, a value smaller than the zero-bias barrier height energy (0.735 eV) of Pd₂Si/n-Si Schottky diodes. Similarly, the value of the effective Richardson constant A** turns out to be 1.17 × 10⁴ A m^–2 K^–2 against the theoretical value of 1.12 × 10⁶ A m^–2 K^–2. Finally, it is demonstrated that the observed trends result due to barrier height inhomogeneities prevailing at the interface which, in turn, cause extra current such that theI–V characteristics continue to remain consistent with the TED process even at low temperatures. The inhomogeneities are believed to have a Gaussian distribution with a mean barrier height of 0.80 V and a standard deviation of 0.05 V at zero-bias. Also, the effect of bias is shown to homogenize barrier heights at a slightly higher mean value.     

Schottky metal library for ZNO-based UV photodiode fabricated by the combinatorial ion beam-assisted deposition

A binary alloy Schottky barrier diode on zinc oxide (ZnO) was developed using the combinatorial ion beam-assisted deposition system. The compositional fraction of the binary alloy was continuously varied using the composition-spread technique, to control the Schottky barrier height. After metal deposition, patterned Schottky diodes were fabricated on a ZnO single-crystal substrate. Pt-Ru alloy was selected from the work function viewpoint. Our experiments showed that the compositional fraction of the Schottky binary alloys changed continuously as designed and the Schottky barrier heights measured by current-voltage (I-V) measurements increased with increasing Pt content. Maximum barrier height difference for ZnO was 137 meV. Using ion beam deposition in parallel with the combinatorial system showed that the Schottky barrier heights for ZnO can be controlled by binary metal alloying.     

Investigation of electrical and ammonia sensing characteristics of Schottky barrier diode based on a single ultra-long ZnO nanorod

Novel ultra-long ZnO nanorods, with lengths about 0.5-1.5 mm and diameters ranging from 100 to 1000 nm, in mass production have been synthesized via the vapor-phase transport method with CuO catalyst at 900 °C. Rectifying Schottky barrier diodes have been fabricated by aligning a single ultra-long ZnO nanorod across paired Ag electrodes. The resulting current-voltage (I-V) characteristics of the SBD exhibit a clear rectifying behavior. The ideality factor of the diode is about 4.6, and the threshold voltage is about 0.54 V at room temperature (300 K). At the same time the detailed I-V characteristics have been investigated in the temperature range 423-523 K. In addition, after exposure of the Schottky diodes to NH₃, the forward and reverse currents increase rapidly, indicating a high sensitivity to NH₃ gas.     

Influence of the interface structure on the barrier height of homogeneous Schottky contacts

Unreconstructed interfaces may be prepared by evaporation of thick Pb films onto surfaces at room temperature. Current-voltage and capacitance-voltage characteristics of such Schottky contacts were measured in the temperature range between 140 and 300 K. The experimental data are analyzed by applying the thermionic-emission theory of inhomogeneous metal-semiconductor contacts as well as the “standard” thermionic-emission theory. From both methods the Schottky barrier height of laterally homogeneous contacts results as 0.724 eV. This value is by 74 meV larger than the previously observed barrier heights of laterally homogeneous interfaces. Similar differences were reported for unreconstructed and reconstructed Al- and contacts. The reduced barrier heights of all these interfaces are explained by the electric dipole associated with the stacking faults of reconstructions at surfaces and interfaces. Received: 14 May 1998 /Revised and Accepted: 7 September 1998     

Simulation studies of current transport in metal–insulator–semiconductor Schottky barrier diodes

The current–voltage characteristics of Schottky diodes with an interfacial insulator layer are analysed by numerical simulation. The current–voltage data of the metal–insulator–semiconductor Schottky diode are simulated using thermionic emission diffusion (TED) equation taking into account an interfacial layer parameter. The calculated current–voltage data are fitted into ideal TED equation to see the apparent effect of interfacial layer parameters on current transport. Results obtained from the simulation studies shows that with mere presence of an interfacial layer at the metal–semiconductor interface the Schottky contact behave as an ideal diode of apparently high barrier height (BH), but with same ideality factor and series resistance as considered for a pure Schottky contact without an interfacial layer. This apparent BH decreases linearly with decreasing temperature. The effects giving rise to high ideality factor in metal–insulator–semiconductor diode are analysed. Reasons for observed temperature dependence of ideality factor in experimentally fabricated metal–insulator–semiconductor diodes are analysed and possible mechanisms are discussed.     

Current-voltage characteristics of Au/GaN/GaAs structure

Au/GaN/n-GaAs structure has been fabricated by the electrochemically anodic nitridation method for providing an evidence of achievement of stable electronic passivation of n-doped GaAs surface. The change of the electronic properties of the GaAs surface induced by the nitridation process has been studied by means of current-voltage (I-V) characterizations on Schottky barrier diodes (SBDs) shaped on gallium nitride/gallium arsenide structure. Au/GaN/n-GaAs Schottky diode that showed rectifying behavior with an ideality factor value of 2.06 and barrier height value of 0.73 eV obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of GaN at the Au/GaAs interfacial layer. The formation of the GaN interfacial layer for the stable passivation of gallium arsenide surface is investigated through calculation of the interface state density N_ss with and without taking into account the series resistance R_s. While the interface state density calculated without taking into account R_s has increased exponentially with bias from 2.2×10¹² cm⁻² eV⁻¹ in (E_c−0.48) eV to 3.85×10¹² cm⁻² eV⁻¹ in (E_c−0.32) eV of n-GaAs, the N_ss obtained taking into account the series resistance has remained constant with a value of 2.2×10¹² cm⁻² eV⁻¹ in the same interval. This has been attributed to the passivation of the n-doped GaAs surface with the formation of the GaN interfacial layer.