Temperature dependence of the reverse current in Schottky barrier diodes

The temperature dependences of the current I in reverse-biased Al/SiO₂/n-Si, Al/SiO₂/n-GaAs and Al/n-GaAs (with the native oxide) structures are measured. It is established that these dependences all have the property that the thermal activation energy decreases with increasing applied voltage and that at higher voltages the plots of ln I versus 1/T deviate from straight lines. The results can be explained on the basis of the fact that the current through the barrier is due to electron tunneling from surface states into the conduction band of the semiconductor. The field intensity in the Schottky barrier and the density of surface electron states in the interfacial layer of the semiconductor are estimated by comparing the experimental results with a tunneling theory that takes into account the effect of the semiconductor lattice phonons on the tunneling probability. Fiz. Tekh. Poluprovodn. 32, 882–885 (July 1998)     

Investigations on the annealing behavior of high-energy carbon irradiated Au/n-GaAs Schottky barrier diodes

Au Schottky barrier diodes (SBDs) have been irradiated using high-energy carbon ion fluences of 1×10¹¹, 1×10¹² and 1×10¹³ cm⁻². Current–voltage characteristics of unirradiated and irradiated diodes have been analyzed. The change in reverse leakage current increases with increasing ion fluence due to the irradiation-induced defects at the interface. The diodes were annealed at 523 and 623 K to study the effect of annealing. The rectifying behavior of the irradiated SBDs improves at 523 K. But at 623 K, the diode behavior deteriorates irrespective of the fluences. Better enhancement in the barrier height and also improvement in the ideality factor of the diodes has been observed at the annealing temperature of 523 K. Scanning Electron Microscopic analysis was carried out on the irradiated samples to delineate the projected range of the defects by high-energy carbon ion irradiation.     

Current transport and formation of energy structures in narrow Au/n-GaAs Schottky diodes

The current transport and formations of potential barrier height in narrow Au/n-GaAs Schottky diodes (SD) with a contact surface in length of 200 μm, width of 1 and 4 μm have been investigated.It was determined that features of current transport are in good agreements with the thermionic emission theory in the forward bias as like high-quality conventional (flat) SD. Features of current transport in the reverse bias also is well described by thermionic emission theory, but it has specific features unlike I–V characteristics flat SD.Forward bias of narrow SD current–voltage (I–U) characteristics are represented by straight lines in semi-logarithmic scale in a wide range, nearly nine order of current up to 0.7 V with near unit ideality factor. In the beginning of the reverse voltage, the current practically was extremely low, by increasing in voltage the current jump in steps approximately for 3–4 order in voltage of 3–4 V, then current increases linear for 3–5 order in semi-logarithmic scale by increasing in voltage up to nearly 7 V.Numerical values of parameters such as the saturation currents, the operating barrier height, ideality factor, dimensionless factor are obtained. The correlations between ideality factor and dimensionless factor were meaningful.The energy diagrams of narrow SD have been drawn in absence and presence of forward and reverse voltage. It is found that electronic processes in narrow SD are well described by energy model of real narrow metal–semiconductor contacts. The additional electric field arising in near contact area of the semiconductor because of creating contact potential difference between contact surface and to it adjoining free surfaces of the metal and semiconductor.     

Investigation of GaAs Schottky barrier diodes in the THz range

The properties of GaAs Schottky barrier diodes as video detectors and mixing elements were investigated in the frequency range from 0.8–2.5 THz. For the most sensitive diode, the video responsivity and system noise temperature were measured as a function of incident laser power. The highest video responsivity was 2,000 V/W at 214μm and 60 V/W at 118μm. For five diodes differing in doping, capacitance, series resistance and anode diameter, the system noise temperature was measured at 214μm and 118μm. The best single sideband (SSB) values are 12,300 K and 24,200 K at 214μm and 118μm, respectively. The system noise temperature versus frequency is given over the range from 0.5–3 THz for two specific diodes demonstrating that the sharpness of the I–V characteristics is only of secondary importance for mixer perfomance at such high frequencies.     

On the current-voltage characteristics of epitaxial Schottky barrier diodes

The J-V characteristics of epitaxial Schottky barrier diodes are analyzed. Based on the assumption of negligible recombination in the epitaxial layer, formal solution from which the J-V characteristics can be calculated is derived. The solution is valid for all injection levels and reduces to the form I = I_s[exp (q(V?IR)/kT) ? 1], where R is the series resistance of the epitaxial layer, under C12 C12V low-injection conditions. The analysis is justified by very close correspondence with exact numerical calculations using the Finite Element Device Analysis Program (FIELDAY) in which thermionic emission boundary conditions are implemented for both electrons and holes. It is shown that for low barrier Schottky diodes the minority carrier injection is negligible and the expression I = I_s[exp (q(V?IR)/kT) ? 1] describes the I-V characteristics over large bias range. For high barrier C12 C12 V Schottky diodes the exact solution must be used as minority carriers are injected and the series resistance is decreased due to conductivity modulation effect.     

A revised boundary condition for the numerical analysis of Schottky barrier diodes

A new boundary condition for the computer simulation of Schottky barrier diodes is proposed. In this model the electron transport analysis can be extended to higher bias voltages by utilizing a current-dependent surface recombination velocity which is based on a drifted Maxwellian distribution of carrier velocities. Calculations based on this revised boundary condition predict a depletion of electrons at the Schottky boundary compared with an accumulation predicted in previously published calculations.     

Evaluation of lateral barrier height of inhomogeneous photolithography-fabricated Au/n-GaAs Schottky barrier diodes from 80 K to 320 K

In order to evaluate current conduction mechanism in the Au/n-GaAs Schottky barrier diode (SBD) some electrical parameters such as the zero-bias barrier height (BH) Φ_bo(I–V) and ideality factor (n) were obtained from the forward bias current–voltage (I–V) characteristics in wide temperature range of 80–320 K by steps of 10 K. By using the thermionic emission (TE) theory, the Φ_bo(I–V) and n were found to depend strongly on temperature, and the n decreases with increasing temperature while the Φ_bo(I–V) increases. The values of Φ_bo and n ranged from 0.600 eV and 1.51(80 K) to 0.816 eV and 1.087 (320 K), respectively. Such behavior of Φ_bo and n is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution (GD) of BHs at Au/n-GaAs interface. In the calculations, the electrical parameters of the experimental forward bias I–V characteristics of the Au/n-GaAs SBD with the homogeneity in the 80–320 K range have been explained by means of the TE, considering GD of BH with linear bias dependence.     

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.     

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.     

A method for measuring the shot noise in Schottky diodes with reduced barrier height

A method for measuring the spectral density of shot noise of one-port networks, in particular, semiconductor diodes, is described. The method is applicable at frequencies of up to 200 MHz. Expressions are obtained that relate the spectral density of the diode’s current noise to the measured noise factor and power gain of the diode fixture with the diode mounted in it. With this method, the dependence of the Fano factor of a GaAs Schottky diode with reduced barrier height on the diode current is determined.     

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.     

Demonstration of the first 10-kV 4H-SiC Schottky barrier diodes

This letter reports the demonstration of the first 4H-SiC Schottky barrier diode (SBD) blocking over 10 kV based on 115-/spl mu/m n-type epilayers doped to 5.6 /spl times/ 10/sup 14/ cm/sup -3/ through the use of a multistep junction termination extension. The blocking voltage substantially surpasses the former 4H-SiC SBD record of 4.9 kV. A current density of 48 A/cm/sup 2/ is achieved with a forward voltage drop of 6 V. The Schottky barrier height, ideality factor, and electron mobility for this very thick epilayer are reported. The SBD's specific-on resistance is also reported.     

The barrier height change and current transport phenomena with the presence of interfacial layer in MIS Schottky barrier solar cells

In this comprehensive study, several interesting results which are different from those previous are reported. We find the barrier height decreases for n-type and increases for p-type when positive ions are introduced into the insulating layer. The increase of open circuit voltage can be traced to the suppression of the dark saturation current by the depletion field induced by the positive charge, and to the diminution of the majority tunneling current by the oxide potential barrier. The tunneling probabilities for majority and minority carriers are different; there are only a finite amount of majority carriers with thermionic energy greater than q(V_bi ? V_s) which can surmount the depletion potential and tunnel into the metal, whereas the photogenerated minority carriers derive kinetic energy in the depletion layer making tunneling easier. Transport coefficients for electrons to transmit from metal to semiconductor and from semiconductor to metal are different for the departure of built in potentials during illumination.     

A DLTS analysis of electron and hole traps in VPE grown n-GaAs using schottky barrier diodes

Capacitance lock-in amplifier deep level transient spectroscopy (DLTS) using Schottky barrier diodes (SBD’s) was used to characterize the electron and hole traps in VPEn-GaAs (N_D - N_A = 1 - 2 x 10¹⁵/cm³) layers grown on n⁺ (10¹⁸/cm³) GaAs substrates. The main electron traps observed were the EL2 atE _c - 0.81 eV and a level atE _c - 0.48 eV. The use of large forward bias electrical injection pulses (and no optical excitation) facilitated the detection of hole traps, of which the defect with an energy level atE _v + 0.42 eV, speculated to be Cu-related, was present in the highest concentration.     

Study of the relaxation of the excess current in silicon Schottky diodes

This study is devoted to investigation of the relaxation of excess current in silicon α-NiTi-n-Si Schottky diodes subjected to either γ-ray radiation or local disturbance of the interface structure using a diamond indenter. A decrease in the excess diode current is attained using both thermal annealing and ultra-sound irradiation. Simultaneously, the parameters of solar cells manufactured from the above-mentioned Schottky diodes subjected to irradiation with γ-ray photons and to single or double irradiation with ultra-sound are studied. It is shown that, after the effect of the diamond indenter, the excess current decreases as a result of thermal annealing; however, a decrease in the excess current to the initial value is not attained. The photoelectric parameters of the studied solar cells before irradiation and after irradiation with γ-ray photons and after single or double irradiation with ultrasound show that ultrasonic treatment is more efficient than thermal annealing.     

Enhancement in electrical properties of Au/n-GaAs Schottky diodes exposed to 60Co gamma rays

The effect of γ-ray exposure on the electrical characteristics of Au/n-GaAs Schottky barrier diodes has been investigated using current–voltage and capacitance–voltage techniques. The results indicate that irradiation with a cumulative dose of 10 Mrad (Si) improves the electrical characteristics of the diode. The parameters like ideality factor, series resistance and reverse leakage current determined from the current–voltage data decreases, whereas the barrier height and rectification ratio increases upon irradiation. The effective barrier height deduced from the capacitance–voltage technique has also increased with irradiation. The irradiated diode shows a higher carrier concentration compared to the virgin diode. The observed overall improvement in the diode quality is attributed to the annealing effect of γ-rays.     

Charge transport mechanisms in Schottky diodes based on low-resistance CdTe:Mn

CdTe:Mn crystals with a resistivity of ～1 Ω cm at 300 K and Schottky diodes based on them are investigated. The electrical conductivity of the material and its temperature variations are explained in terms of the statistics of electrons and holes in semiconductors with allowance for the compensation processes. The ionization energy and the degree of compensation of the donors responsible for the conductivity are determined. It is shown that, in the case of forward connection and low reverse biases, the currents in Au/CdTe:Mn Schottky diode are determined by generation-recombination processes in the space-charge region. At higher reverse biases (above 1.5–2 V) the excess current is caused by electron tunneling from the metal to the semiconductor, and at even higher voltages (>6–7 V) an additional increase in the reverse current due to avalanche processes is observed.     

A new approach to the optimization of resistive frequency converters based on Schottky barrier diodes

A new approach to the optimization of the transfer characteristics of resistive frequency converters is studied. In this approach, with allowance for the requirement of practicality, the required power of a local oscillator is determined for the assigned conductance of a signal generator. As has been demonstrated, this is also the necessary condition that ensures the zero sensitivity of conversion loss to small fluctuations in the power of a local oscillator. The formulas required for calculations have been obtained.