Classical infrared mixing with solid state diodes

It is shown that classical infrared diode mixing can compete with straight quantum detector diodes even if the available power gain of the diode mixer is as small as 10^?5–10^?6. To shed light on the diode mixer problem, the small signal diode detector problem is discussed, the effect of the series resistance r of the diode is dealt with and the time constants that may be operating in the device are evaluated. It is shown that Schottky barrier diodes operating in the diffusion mode are probably too slow, even though the response problem has not been solved exactly. Schottky barrier diodes operating in the thermionic mode are better; they can be understood in terms of a vacuum tube analogy, indicating that the characteristic time constant is the transit time of those electrons that just pass the barrier. Diodes operating in the tunneling mode have probably the fastest response, but an exact theory has not been developed. An interesting series resonance method is discussed that may lead to improved detector response near the resonance frequency.     

A computer-aided simulation model for the I–V characteristic of M-n-p silicon Schottky-barrier diodes produced by use of low-energy arsenic-ion implantation

Current-transport properties of Al-n-p silicon Schottky-barrier diodes have been studied both experimentally and theoretically. An analytical model for the I-V characteristic of a metal-n-p Schottky barrier diode has been developed by using an interfacial layer-thermionic-diffusion model. Assuming a Gaussian distribution for the implanted profile, the barrier-height enhancement and ideality factor have been derived analytically. Using low energy (25 KeV) arsenic implantation with the dose ranged form 8 × 10¹⁰/cm² to 10¹²/cm², Al-n-p silicon Schottky barrier diodes have been fabricated and characterized. Comparisons between the experimental measurements and the results of computer simulations have been performed and satisfactory agreements between these comparisons have been obtained. The reverse I–V characteristics of the fabricated Al-n-p silicon Schottky barrier diodes can also be well simulated by the developed model.     

Theoretical analysis of a novel MPN gallium arsenide Schottky barrier solar cell

Theoretical analysis for a novel Au-p-n GaAs Schottky barrier solar cell has been made in this note. It is shown that barrier height equal to the energy band gap of GaAs can be obtained in the proposed cell structure if the thickness and dopant density of the p-GaAs layer are properly chosen. Calculations of the barrier height as function of the thickness and dopant density of the p-layer have been carried out for a Au-p-n GaAs Schottky barrier cell. It is shown that AMO efficiency around 22% can be achieved in the proposed solar cell when N_D = 10¹⁶ cm^?3, N_A = 8 × 10¹⁸ cm^?3 and $\text{W}{}_{\mathrm{p}}\text{= 100}\text{A}\text{?}$ are chosen.     

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.     

Influence of Annealing on Electrical Properties of an Organic Thin Layer-Based n-Type InP Schottky Barrier Diode

The electrical properties of a fabricated Au/polymethylmethacrylate (PMMA)/n-InP Schottky barrier diode have been analyzed for different annealing temperatures using current–voltage (I–V) and capacitance–voltage (C–V) techniques. It is observed that the Au/PMMA/n-InP structure shows excellent rectifying behavior. The extracted barrier height and ideality factor of the as-deposited Au/PMMA/n-InP Schottky contact are 0.68 eV (J–V)/0.82 eV (C–V) and 1.57, respectively. However, the barrier height (BH) of the Au/PMMA/n-InP Schottky contact increases to 0.78 eV (J–V)/0.99 eV (C–V) when the contact is annealed at 150°C for 1 min in nitrogen atmosphere. Upon annealing at 200°C, the BH value decreases to 0.72 eV (J–V)/0.90 eV (C–V) and the ideality factor increases to 1.48. The PMMA layer increases the effective barrier height of the structure by creating a physical barrier between the Au metal and the n-InP. Cheung’s functions are also used to calculate the series resistance of the Au/PMMA/n-InP structure. The interface state density (N _ss) is found to be 6.380 × 10¹² cm^?2 eV^?1 and 1.916 × 10¹² cm^?2 eV^?1 for the as-deposited and 150°C-annealed Au/PMMA/n-InP Schottky contacts, respectively. These results indicate that the interface state density and series resistance have a significant effect on the electrical characteristics of Au/PMMA/n-InP Schottky barrier devices. Finally, it is noted that the diode parameters change with increasing annealing temperature.     

Bulk electromigration and contact interface electromigration and conditions for eliminating both mechanisms in SiO2-covered aluminum lines

Electromigration tests were performed at 200°C with SiO₂-covered, large-grained, narrow Al interconnect lines ending on semiconductor contacts, which were marked by different barrier layers. An overlapping Mo barrier layer produced premature contact failures by interface electromigration. The interface threshold value (jl)_th,i had been reduced by the covering oxide to about 400 A/cm. For Al current densities of 8 × 10⁵A/cm² interface mass flow was avoided by using a short silicide-like barrier layer, which was restricted to the contact area only. The remaining mass flow mechanism was bulk electromigration, resulting in contact openings after extremely long stress periods. Bulk electromigration can be eliminated in oxide covered Al lines, if the positive biased ends are completely covered. The reason is a threshold value for bulk electromigration, which is increased considerably by the covering oxide to a time-dependent value of about 8 × 10⁷Ah/cm at 200°C.     

Laser formation of Pt-Si Schottky barriers on silicon

135 nsec pulses ofλ = 1.06μm light from a Nd: YAG laser have been used to form Schottky barriers by irradiation of a 500Å thick metal film on n-type silicon. Large area barriers were fabricated by over-lapping individual 30μ diameter laser pulses of from 4 to 12 J/cm². The barrier height was 0.73 ± 0.03 V, independent of the laser power. The barrier quality, as assessed by measurement of the forward current characteristic, decreased with laser power to a value of n = 1.5 at 12 J/cm².     

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.     

Laterally inhomogeneous barrier analysis of identically prepared Cd/CdS/n-Si/Au-Sb structures by SILAR method

In this study, CdS thin films have been deposited on n-Si substrate using a successive ionic layer adsorption and reaction (SILAR) method at room temperature. Structural properties have been investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The XRD and SEM investigations show that films are covered well, polycrystalline structure and good crystallinity levels. The Cd/CdS/n-Si/Au-Sb structures (28 dots) have been identically prepared by the SILAR method. The effective barrier heights and ideality factors of these structures have been obtained from forward bias current-voltage (I-V) and reverse bias capacitance voltage (C-V) characteristics. The barrier height (BH) for the Cd/CdS/n-Si/Au-Sb structure calculated from the I-V characteristics have ranged from 0.664 eV to 0.710 eV, and the ideality factor from 1.190 to 1.400. Lateral homogeneous barrier height has been determined approximately 0.719 eV from the experimental linear relationship between BHs and ideality factors. The experimental BH and ideality factor distributions obtained from the I-V characteristics have been fitted by a Gaussian function, and their means of values have been found to be (0.683 ± 0.01) eV and (1.287 ± 0.05), respectively. The barrier height values obtained from the reverse bias C⁻²-V characteristics have ranged from 0.720 eV to 0.865 eV and statistical analysis yields the mean (0.759 ± 0.02) eV. Additionally, a doping concentration obtained from C⁻²-V characteristics has been calculated (8.55 ± 1.62) × 10¹⁴ cm⁻³.     

Radiation effects and interphase interactions in ohmic and barrier contacts to indium phosphide as induced by rapid thermal annealing and irradiation with γ-ray 60Co photons

The radiation resistance of Au-Pd-Ti-Pd-n ⁺⁺-InP ohmic contacts and Au-TiB _x -n-n ⁺-n ⁺⁺-InP barrier contacts—both initial and subjected to a rapid thermal annealing and irradiated with ⁶⁰Co γ-ray photons with doses as high as 10⁹ R—has been studied. Before and after external effects, the electrical characteristics of the barrier and ohmic contacts, distribution profiles for components, and phase composition in the metallization layers have been measured. In ohmic Pd-Ti-Pd-Au contacts subjected to rapid thermal annealing and irradiation, a significant distortion of the layered structure of metallization occurs; this distortion is caused by the thermal and irradiation-stimulated transport of Pd over the grain boundaries in polycrystalline Ti and Au films. However, the specific contact resistance ρ _c does not change appreciably, which is related to a comparatively unvaried composition of the contact-forming layer at the Pd-n ⁺-InP interface. In the initial sample and the sample subjected to the rapid thermal annealing at T = 400°C with the Au-TiB _x -n-n ⁺-n ⁺⁺-InP barrier contacts and irradiated with the dose as high as 2 × 10⁸ R, a layered structure of metallization is retained. After irradiation with the dose as high as 10⁹ R, in the samples subjected to a rapid thermal annealing at T = 400°C, the layered structure of metallization becomes completely distorted; however, this structure is retained in the initial sample. The electrical properties of the contact structure appreciably degrade only after irradiation of the sample preliminarily subjected to a rapid thermal annealing at T = 400°C.     

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.     

Analysis of characteristics of photodetectors based on InGaAs heteroepitaxial structures for 3D imaging

The 320 × 256 focal plane arrays based on р ⁺ -B–n-N ⁺ tetralayer heterostructures with a wide-gap barrier layer have been investigated. The heterostructures with a narrow-gap n-InGaAs absorbing layer were grown by means of metalorganic vapor phase epitaxy on InP substrates. The band discontinuity between the In_0.53Ga_0.47As absorbing layer and the In_0.52Al_0.48As barrier layer is removed by growing a thin four-component n-AlInGaAs layer with the bandgap gradient variation. Delta-doped layers included into the heterostructures make it possible to lower the barrier in the valence band and eliminate the nonmonotonicity of energy levels. The experimental study of the dark current has been performed. It has been revealed that the average value of the dark current does not exceed 10 fA for the photodiode arrays with a pitch of 30 μm.     

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.     

Barrier characteristics of gold Schottky contacts on moderately doped n-InP based on temperature dependent I-V and C-V measurements

The temperature dependences of current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the gold Schottky contacts on moderately doped n-InP (Au/MD n-InP) Schottky barrier diodes (SBDs) have been systematically investigated in the temperature range of 60-300 K. The main diode parameters, ideality factor (n) and zero-bias barrier height (apparent barrier height) were found to be strongly temperature dependent and while the decreases, the n and the increase with decreasing temperature. According to Thermionic Emission (TE) theory, the slope of the conventional Richardson plot [In(J₀/T²) vs. 1000/T] should give the barrier height. However, the experimental data obtained do not correlate well with a straight line below 160 K. This behaviour has been interpreted on the basis of standard TE theory and the assumption of a Gaussian distribution of the barrier heights due to barrier inhomogeneities that persist at the metal-semiconductor interface. The linearity of the apparent barrier height vs. 1/(2kT) plot that yields a mean barrier height of 0.526 eV and a standard deviation (σ_s0) of 0.06 eV, was interpreted as an evidence to apply the Gaussian distribution of the barrier height. Furthermore, modified Richardson plot [ vs. 1/T] has a good linearity over the investigated temperature range and gives the and the Richardson constant (A^∗) values as 0.532 eV and 15.90 AK⁻²cm⁻², respectively. The mean barrier heights obtained from both plots are appropriate with each other and the value of A^∗ obtained from the modified Richardson plot is close to the theoretical value of 9.4 AK⁻²cm⁻² for n-InP. From the C-V characteristics, measured at 1 MHz, the capacitance was determined to increase with increasing temperature. C-V measurements have resulted in higher barrier heights than those obtained from I-V measurements. The discrepancy between Schottky barrier heights(SBHs) obtained from I-V and C-V measurements was also interpreted. As a result, it can be concluded that the temperature dependent characteristic parameters for Au/MD n-InP SBDs can be successfully explained on the basis of TE mechanism with Gaussian distribution of the barrier heights.     

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.     

Gaussian distribution of inhomogeneous barrier height in tungsten/4H-SiC (000-1) Schottky diodes

The Gaussian distribution model have been used to analyze the anomalies observed in tungsten (W)/4H-SiC current voltage characteristics due to the barrier inhomogeneities that prevail at the metal-semiconductor interface. From the analysis of the forward I-V characteristics measured at elevated temperatures within the range of 303-448 K and by the assumption of a Gaussian distribution (GD) of barrier heights (BHs), a mean barrier height of 1.277 eV, a zero-bias standard deviation σ₀ = 0.092 V and a factor T₀ of 21.69 K have been obtained. Furthermore the modified Richardson plot according to the Gaussian distribution model resulted in a mean barrier height and a Richardson constant (A^∗) of 1.276 eV and 145 A/cm² K², respectively. The A^∗ value obtained from this plot is in very close agreement with the theoretical value of 146 A/cm² K² for n-type 4H-SiC. Therefore, it has been concluded that the temperature dependence of the forward I-V characteristics of the W/4H-SiC contacts can be successfully explained on the basis of a thermionic emission conduction mechanism with Gaussian distributed barriers. In addition, a comparison is made between the present results and those obtained previously assuming the pinch-off model.     

Electrical and photovoltaic properties of an organic-inorganic heterojunction based on a BODIPY dye

An organic-inorganic heterojunction based on a BODIPY dyes has been produced by forming dye thin film on n-Si. The electrical parameters of the structure have been investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The ideality factor, the barrier height and the series resistance values of the diode have been calculated as 2.43, 0.84 eV, and about 1.3 kΩ, respectively. The diode behaves as a non-ideal diode because of the series resistance and interface layer. The barrier height value obtained from I-V measurement has been compared with one from C-V measurement. Moreover, it has been seen that the diode is highly sensitive to the light and the reverse bias current increases about 1 × 10⁴ times at −1 V under 100 mW/cm² and AM1.5 illumination condition. The short photocurrent density (J_sc) and the open circuit voltage (V_oc), the fill factor (FF) and power conversion efficiency (η) have been determined as 3.78 mA/cm², 327 mV, 0.28 and 0.48 %, respectively.     

Hafnium-ntype silicon Schottky barriers

This paper describes the electrical properties of hafnium-/n-type/silicon contacts. These contacts were found to be Schottky barriers with a low barrier height. Polished and chemically cleaned 〈111〉 silicon wafers with a donor concentration N_d = 7 × 10²² m^?3 were used to fabricate experimental Schottky barrier structures. For the Schottky barrier height φ_bn and the ideality factor n values were found of 0.47 V and 1.07–1.11, respectively. It is concluded that due to their low forward voltage drop and good rectifying properties, Hf-nSi contacts can be applied in microwave Schottky barrier diodes.     

Schottky barrier height variation with metallurgical reactions in aluminum-titanium-gallium arsenide contacts

The behaviour of A1/Ti/n-GaAs Schottky contacts under heat treatment at around 400°C have been studied for their application to GaAs MESFETs. Barrier heights have been determined using both I-V and C-V measurements as a function of heat treatment time. Reaction products due to heat treatment have been studied by X-ray diffraction and Auger electron spectroscopy. The A1/Ti/n-GaAs Schottky contacts barrier height shows an $\text{“N”-}\text{shaped}$ variation in response to heat treatment time. A marked reduction in barrier height follows a slight increase at the initial annealing stage. The barrier height then takes a minimum value. The slight increase in barrier height at the initial stage in the heat treatment is brought about by a Ti and GaAs reaction. The marked barrier height reduction is closely correlated to formation of the compound Al₃Ti. The increase in barrier height observed after the reduction can be explained in terms of GaAlAs formation at the metal-semiconductor interface. This seems to indicate that heat treatment is essential for application of Al/Tin-GaAs Schottky contacts to practical devices.     

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.