AuSiC Schottky barrier diodes

Results of the experimental study of Au n-type SiC Schottky barrier diodes at room temperature are presented. The diodes are fabricated by vacuum-evaporating gold on chemically etched n-type hexagonal (6H) SiC surfaces and exhibit excellent forward current vs voltage characteristics with the exponential factor n of about 1·07±0·02 for voltages between 0·35 and 0·85 V. The linear part of the characteristic, in a semi-logarithmic plot, extends over seven orders of magnitude in current. The forward current-voltage characteristics are found to agree quantitatively with the theory based on thermionic emission with the barrier height modified by image force lowering. The Schottky barrier height is determined from three independent techniques: differential capacitance vs voltage, photoresponse, and forward current vs voltage methods. The barrier height deduced from the three methods is about 1·40±0·05 V.     

Impedance and barrier capacitance of silicon diodes implanted with high-energy Xe ions

Characteristics of Si p⁺n diodes with non-uniformly distributed compensating defects, which were introduced by implantation with Xe²³⁺ ions, have been studied. The layer with the maximum concentration of the compensating defects was located in the vicinity of the metallurgical p-n junction. It is found that the presence of the defect layer results in non-monotonic dependences of the imaginary part of impedance (−Z″) and differential conductance (G = −dI/dU) of the implanted diodes on reverse bias voltage U. An equivalent circuit of the irradiated diode is proposed, which allows us to approximate the measured frequency dependences of capacitance and conductance of the irradiated diodes and to determine values of diode barrier capacitance C_pn at different reverse bias voltages.     

Breakdown and capacitance properties of hyperabrupt epitaxial Schottky barrier diodes

An analysis of the breakdown and capacitance properties of punch-through hyperabrupt epitaxial Schottky barrier diodes has been carried out. Results are given for the dependence of breakdown voltage of such a device on surface concentration and epitaxial layer thickness. Design curves are given for epitaxial hyperabrupt schottky varactor diodes. The design procedure yields an optimal impurity profile in which just-punch-through occurs at the highest voltage of operation. This gives a maximum dynamic range of operation still keeping the series resistance to a minimum. A corrected boundary condition to determine the profile constants associated with an n/n⁺ (high/low) junction is also given.     

The source of negative capacitance and anomalous peak in the forward bias capacitance-voltage in Cr/p-si Schottky barrier diodes (SBDs)

The frequency and voltage dependence of capacitance–voltage (C–V) and conductance-voltage (G/ω−V) characteristics of the Cr/p-Si metal semiconductor (MS) Schottky barrier diodes (SBDs) were investigated in the frequency and applied bias voltage ranges of 10 kHz to 5 MHz and (−4 V)−(+4 V), respectively, at room temperature. The effects of series resistance (R_s) and density distribution of interface states (N_ss), both on C–V and G/ω−V characteristics were examined in detail. It was found that capacitance and conductance, both, are strong functions of frequency and applied bias voltage. In addition, both a strong negative capacitance (NC) and an anomalous peak behavior were observed in the forward bias C–V plots for each frequency. Contrary to the behavior of capacitance, conductance increased with the increasing applied bias voltage and there happened a rapid increase in conductance in the accumulation region for each frequency. The extra-large NC in SBD is a result of the existence of R_s, N_ss and interfacial layer (native or deposited). In addition, to explain the NC behavior in the forward bias region, we drew the C–I and G/ω−I plots for various frequencies at the same bias voltage. The values of C decrease with increasing frequency at forward bias voltages and this decrease in the NC corresponds to an increase in conductance. The values of N_ss were obtained using a Hill–Coleman method for each frequency and it exhibited a peak behavior at about 30 kHz. The voltage dependent profile of R_s was also obtained using a Nicollian and Brews methods.     

面向太赫兹应用的InP基肖特基二极管

Based on characteristics such as low barrier and high electron mobility of lattice matched In_0.53Ga_0.47 As layer,InP-based Schottky barrier diodes（SBDs） exhibit the superiorities in achieving a lower turn-on voltage and series resistance in comparison with GaAs ones.Planar InP-based SBDs have been developed in this paper.Measurements show that a low forward turn-on voltage of less than 0.2 V and a cutoff frequency of up to 3.4 THz have been achieved.The key factors of the diode such as series resistance and the zero-biased junction capacitance are measured to be 3.32Ωand 9.1 fF,respectively.They are highly consistent with the calculated values.The performances of the InP-based SBDs in this work,such as low noise and low loss,are promising for applications in the terahertz mixer,multiplier and detector circuits.     

The effect of Mo-doped PVC+TCNQ interfacial layer on the electrical properties of Au/PVC+TCNQ/p-Si structures at room temperature

The effect of Mo-doped and undoped PVC+TCNQ interfacial layer on electrical characteristics of a Au/PVC+TCNQ/p-Si structure was investigated using current–voltage (I–V), capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements at room temperature. The energy dependent interface states density (N_ss) was obtained from the forward bias I–V data by taking into account voltage dependent effective barrier height (Φ_e) for two diodes, i.e. with and without Mo doping. The voltage dependent resistance (R_i) of structures was also obtained using Ohm׳s law and the method of Nicollian and Brews for the diodes. In order to eliminate the effect of series resistance (R_s), C and G/ω at high frequency values were corrected. N_ss and R_s values were compared between the diodes and experimental results showed that N_ss and R_s values of the Mo-doped PVC+TCNQ structure are considerably lower than those of the undoped PVC+TCNQ structure. The other important parameters such as ideality factor (n), reverse saturation current (I_s), zero-bias barrier heights (Φ_Bo) and R_s were obtained from forward bias I–V data by using I–V, Cheung and Norde methods. Experimental results confirmed that the Mo-doped (PVC+TCNQ) layer considerably improved the performance of the Au/PVC+TCNQ/p-Si structure.     

Capacitance–conductance–current–voltage characteristics of atomic layer deposited Au/Ti/Al2O3/n-GaAs MIS structures

We have studied the admittance and current–voltage characteristics of the Au/Ti/Al₂O₃/n-GaAs structure. The Al₂O₃ layer of about 5 nm was formed on the n-GaAs by atomic layer deposition. The barrier height (BH) and ideality factor values of 1.18 eV and 2.45 were obtained from the forward-bias ln I vs V plot at 300 K. The BH value of 1.18 eV is larger than the values reported for conventional Ti/n-GaAs or Au/Ti/n-GaAs diodes. The barrier modification is very important in metal semiconductor devices. The use of an increased barrier diode as the gate can provide an adequate barrier height for FET operation while the decreased barrier diodes also show promise as small signal zero-bias rectifiers and microwave. The experimental capacitance and conductance characteristics were corrected by taking into account the device series resistance R_s. It has been seen that the non-correction characteristics cause a serious error in the extraction of the interfacial properties. Furthermore, the device behaved more capacitive at the reverse bias voltage range rather than the forward bias voltage range because the phase angle in the reverse bias has remained unchanged as 90° independent of the measurement frequency.     

Effect of annealing temperature on the electrical characteristics of Platinum/4H-SiC Schottky barrier diodes

Pt/4H-SiC Schottky barrier diodes have been fabricated to investigate the effect of annealing on the electrical characteristics of the fabricated devices. The parameters such as barrier height, ideality factor and donor concentration were deduced from the current–voltage (I–V) and the capacitance–voltage (C–V) measurements at room temperature. Diodes showed non-ideal behaviour like high value of ideality factor and lower value of barrier height. A barrier height of 1.82?eV was obtained from C–V measurements and it was 1.07?eV when obtained from the I–V measurements with ideality factor 1.71 for as-deposited diodes at room temperature. The diodes, therefore, were annealed in the temperature range from 25°C to 400°C to observe the effect of annealing temperature on these parameters. Schottky barrier height and ideality factors were found to be temperature-dependent. After rapid thermal annealing upto 400°C, a barrier height of 1.59?eV from C–V measurements and the value of 1.40?eV from I–V measurements with ideality factor 1.12 were obtained. Barrier heights deduced from C–V measurements were consistently larger than those obtained from I–V measurements. To come to terms with this discrepancy, we re-examined our results by including the effect of ideality factor in the expression of the barrier height. This inclusion of ideality factor results in reasonably good agreement between the values of barrier height deduced by the above two methods. We believe that these improvements in the electrical parameters result from the improvement in the quality of interfacial layer.     

Electrical characteristics of Pd Schottky contacts on ZnO films

The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φ_b) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements.     

Determination of the laterally homogeneous barrier height of palladium Schottky barrier diodes on n-Ge (1 1 1)

We have studied the experimental linear relationship between barrier heights and ideality factors for palladium (Pd) on bulk-grown (1 1 1) Sb-doped n-type germanium (Ge) metal-semiconductor structures with a doping density of about 2.5×10¹⁵ cm^?3. The Pd Schottky contacts were fabricated by vacuum resistive evaporation. The electrical analysis of the contacts was investigated by means of current–voltage (I–V) and capacitance–voltage (C–V) measurements at a temperature of 296 K. The effective barrier heights from I–V characteristics varied from 0.492 to 0.550 eV, the ideality factor n varied from 1.140 to 1.950, and from reverse bias capacitance–voltage (C^?2–V) characteristics the barrier height varied from 0.427 to 0.509 eV. The lateral homogenous barrier height value of 0.558 eV for the contacts was obtained from the linear relationship between experimental barrier heights and ideality factors. Furthermore the experimental barrier height distribution obtained from I–V and (C^?2?V) characteristics were fitted by Gaussian distribution function, and their mean values were found to be 0.529 and 0.463 eV, respectively.     

Influence of inhomogeneous contact in electrical properties of 4H–SiC based Schottky diode

Schottky diodes realized on 4H–SiC n-type wafers with an epitaxial layer and a metal-oxide overlap for electric field termination were studied. The oxide was grown by plasma enhanced chemical vapor deposition (PECVD) and the Schottky barriers were formed by thermal evaporation of titanium or nickel. Diodes, with voltage breakdown as high as 700 V and ideality factor as low as 1.05, were obtained and characterized after packaging in standard commercial package (TO220).The electrical properties such as ideality factor, hight barrier, the series resistance R_s were deduced by current/voltage (I–V) analysis using the least mean square (LMS) method. The temperature effect on break voltage, R_s and saturation current was studied. A model based on two parallel Schottky diodes with two barrier heights is presented for some devices having an inhomogeneous contact. It is shown that the excess current at low voltage can be explained by a lowering of the Schottky barrier in localized regions. We use the two series RC components electrical model in order to study the dynamic behaviour of the Schottky diode in low frequency and to improve the effect of barrier inhomogeneities in electrical properties.     

Comparison of electrical characteristics between AlGaN/GaN and lattice-matched InAlN/GaN heterostructure Schottky barrier diodes

Lattice-matched Pt/Au–In_0.17Al_0.83N/GaN hetreojunction Schottky barrier diodes (SBDs) with circular planar structure have been fabricated. The electrical characteristics of InAlN/GaN SBD, such as two-dimensional electron gas (2DEG) density, turn-on voltage, Schottky barrier height, reverse breakdown voltage and the forward current-transport mechanisms, are investigated and compared with those of a conventional AlGaN/GaN SBD. The results show that, despite the higher Schottky barrier height, more dislocations in InAlN layer causes a larger leakage current and lower reverse breakdown voltage than the AlGaN/GaN SBD. The emission microscopy images of past-breakdown device suggest that a horizontal premature breakdown behavior attributed to the large leakage current happens in the InAlN/GaN SBD, differing from the vertical breakdown in the AlGaN/GaN SBD.     

Graphite/<Emphasis Type="Italic">p</Emphasis>-SiC Schottky Diodes Prepared by Transferring Drawn Graphite Films onto SiC

Graphite/p-SiC Schottky diodes are fabricated using the recently suggested technique of transferring drawn graphite films onto p-SiC single-crystal substrates. The current–voltage and capacitance–voltage characteristics are measured at different temperatures and at different frequencies of a small-signal AC signal, respectively. The temperature dependences of the potential-barrier height and of the series resistance of the graphite/p-SiC junctions are measured and analyzed. The dominant mechanisms of the charge–carrier transport through the diodes are determined. It is shown that the dominant mechanisms of the transport of charge carriers through the graphite/p-Si Schottky diodes at a forward bias are multi-step tunneling recombination and tunneling described by the Newman formula (at high bias voltages). At reverse biases, the dominant mechanisms of charge transport are the Frenkel–Poole emission and tunneling. It is shown that the graphite/p-SiC Schottky diodes can be used as detectors of ultraviolet radiation since they have the open-circuit voltage V_oc = 1.84 V and the short-circuit current density I_sc = 2.9 mA/cm² under illumination from a DRL 250-3 mercury–quartz lamp located 3 cm from the sample.     

Defect analysis of n-type silicon strained layers

The structural and electrical properties of n-type silicon strained layers, sandwiched between Si_1−xGe_x layers, with x=0.15, 0.20 and 0.30 have been investigated using a combination of analytical techniques. Here, the focus is on the application of deep level transient spectroscopy (DLTS) on p–n junction structures, to assess non-radiative generation-recombination centres. It will be demonstrated that successful analysis can only be applied if the edges of the devices are chemically passivated. Finally, it is shown that for low-leakage diodes, the quantum-well properties can, in principle, be extracted from the combined DLTS and capacitance–voltage/capacitance–temperature characteristics.     

Electrical characterization and DLTS analysis of a gold/n-type gallium nitride Schottky diode

This work describes a comparison of current density–voltage (J–V) and capacitance–voltage (C–V) properties measured as a function of temperature; deep trap properties are measured by deep level transient spectroscopy (DLTS) of Schottky diodes fabricated on n-type gallium nitride (GaN grown by metal organic vapor phase epitaxy (MOVPE). Unexpected behavior in the standard Richardson plot was observed in the temperature range 165–480 K, reflecting a range of Schottky barrier heights and a variation of ideality factor. This was explained by applying a Gaussian spatial distribution of barrier heights across the Schottky diode. C–V measurements were carried out in the temperature range 165–480 K to compare the temperature dependence of the barrier height with those obtained by the Gaussian distribution method. DLTS and high-resolution Laplace DLTS (LDLTS) show a majority carrier peak centered at 450 K.     

Anomalous dependences of the diode barrier capacitance on bias voltage and temperature

Capacitances of a Schottky barrier and p ⁺-n junction whose n-type regions contain shallow donors and deep acceptors with levels in the upper part of the energy gap have been calculated. The capacitance was represented as two series capacitances of the near-contact region containing only donor impurity ions and of the intermediate layer at the interface between the space-charge region and the diode base, with account of the free-carrier concentration and its dependence on the potential. It was found that the capacitance of the intermediate layer heavily depends on temperature and may increase with the bias voltage. The calculated capacitancevoltage characteristics of the barrier capacitance are in agreement with experimental data and even describe the nonmonotonic dependences of the capacitance on the bias voltage.     

Behavior of various silicon Schottky barrier diodes under heat treatment

Variations of Schottky forward voltage with heat treatment have been observed for AlPd₂Si Si and Si-doped AlPd₂Si Si Schottky barrier diodes. These variations have been reduced to a minimum by the use of a barrier metal such as TiW between Al and the silicided contacts.     

Frequency and voltage dependency of interface states and series resistance in Al/SiO2/p-Si MOS structure

The capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics of Al/SiO₂/p-Si metal-oxide-semiconductor (MOS) Schottky diodes have been measured in the voltage range from ?3 to +3 V and frequency range from 5 KHz to 1 MHz at room temperature. It is found that both C and G/ω of the MOS capacitor are very sensitive to frequency. The fairly large frequency dispersion of C–V and G/ω–V characteristics can be interpreted in terms of the particular distribution of interface states at SiO₂/Si interface and the effect of series resistance. At relatively low frequencies, the interface states can follow an alternating current (AC) signal that contributes to excess capacitance and conductance. This leads to an anomalous peak of C–V curve in the depletion and accumulation regions. In addition, a peak at approximately ?0.2 V appears in the R_s–V profiles at low frequency. The peak values of the capacitance and conductance decrease with increasing frequency. The density distribution profile of interface state density (N_ss) obtained from C_HF–C_LF capacitance measurement also shows a peak in the depletion region.     

Origin of forward bias capacitance peak and intersection behavior of C and G/w of Ag/p-InP Schottky barrier diodes

Frequency-dependent electrical characteristics of Ag/p-InP diodes have been determined using impedance spectroscopy at room temperature. Series resistance (R_s) and interface state(s) (N_ss) values were extracted from capacitance (C) and conductance (G/w) data using the Nicollian and Goetzberger and Hill–Coleman methods, respectively. C and G/w data were also corrected in the whole measured bias voltage range to obtain real diode capacitance C_c and conductance G_c values in order to see the effects of R_s. Both the C–V and R_s–V plots showed anomalous peak in depletion region especially at low frequencies due to the existence of N_ss. C–V and G/w–V plots crossed at a certain bias voltage and this point shifted toward negative bias voltages with increasing frequency and then disappeared at 3 MHz. Also, decrease in C values corresponds to an increase in G/w values in the same bias voltages.     

Effects of PCBM concentration on the electrical properties of the Au/P3HT:PCBM/n-Si (MPS) Schottky barrier diodes

In this study, the gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/n-type silicon (Au/P3HT:PCBM/n-Si) metal–polymer–semiconductor (MPS) Schottky barrier diodes (SBDs) were investigated in terms of the effects of PCBM concentration on the electrical parameters. The forward and reverse bias current–voltage (I–V) characteristics of the Au/P3HT:PCBM/n-Si MPS SBDs fabricated by using the different P3HT:PCBM mass ratios were studied in the dark, at room temperature. The main electrical parameters, such as ideality factor (n), barrier height (Φ_B0), series resistance (R_s), shunt resistance (R_sh), and density of interface states (N_ss) were determined from I–V characteristics for the different P3HT:PCBM mass ratios (2:1, 6:1 and 10:1) used diodes. The values of n, R_s, Φ_B0, and N_ss were reduced, while the carrier mobility and current were increased, by increasing the PCBM concentration in the P3HT:PCBM organic blend layer. The ideal values of electrical parameters were obtained for 2:1 P3HT:PCBM mass ratio used diode. This shows that the electrical properties of MPS diodes strongly depend on the PCBM concentration of the P3HT:PCBM organic layer. Moreover, increasing the PCBM concentration in P3HT:PCBM organic blend layer improves the quality of the Au/P3HT:PCBM/n-Si (MPS) SBDs which enables the fabrication of high-quality electronic and optoelectronic devices.