Temperature dependent current–voltage (I–V) characteristics of Au/n-Si (1 1 1) Schottky barrier diodes with PVA(Ni,Zn-doped) interfacial layer

Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (Φ_B0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of Φ_B0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw Φ_B0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ₀) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A^?) as 0.966 eV and 118.75 A/cm²K², respectively, without using the temperature coefficient of the BH. This value of A^* 118.75 A/cm²K² is very close to the theoretical value of 120 A/cm²K² for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface.     

Barrier height and ideality factor dependency on identically produced small Au/p-Si Schottky barrier diodes

Small high-quality Au/P-Si Schottky barrier diodes (SBDs) with extremely low reverse leakage current using wet lithography were produced. Their effective barrier heights (BHs) and ideality factors from current–voltage (I-V) characteristics were measured by a conducting probe atomic force microscope (C-AFM). In spite of identical preparation of the diodes there was a diode-to-diode variation in ideality factor and barrier height Parameters. By extrapolating of the plots the built in potential of the Au /p-Si contact was obtained as Vbi=0.5425 V and the barrier height value (ФB(C-V)) was calculated to be ФB(C-V)=0.7145 V for Au/p-Si. It is found that for the diodes with diameters smaller than 100 µm the diode barrier height and ideality factor dependency to their diameters and correlation between the diode barrier height and its ideality factor are nonlinear, where similar to the earlier reported different metal semiconductor diodes in the literature, these parameters for the here manufactured diodes with diameters more than 100 µm are also linear. Based on the very obvious sub-nanometer C-AFM produced pictures the scientific evidence behind this controversy is also explained.     

Barrier height and ideality factor dependency on identically produced small Au/p-Si Schottky barrier diodes

Small high-quality Au/P-Si Schottky barrier diodes (SBDs) with an extremely low reverse leakage current using wet lithography were produced. Their effective barrier heights (BHs) and ideality factors from current-voltage (Ⅰ-Ⅴ) characteristics were measured by a conducting probe atomic force microscope (C-AFM). In spite of the identical preparation of the diodes there was a diode-to-diode variation in ideality factor and barrier height parameters. By ex-trapolating the plots the built in potential of the Au/p-Si contact was obtained as Vbi = 0.5425 V and the barrier height value φB(C-V) was calculated to be φB(C-V) = 0.7145 V for Au/p-Si. It is found that for the diodes with diameters smaller than 100 μm, the diode barrier height and ideality factor dependency to their diameters and correlation between the diode barrier height and its ideality factor are nonlinear, where similar to the earlier reported different metal semi-conductor diodes in the literature, these parameters for the here manufactured diodes with diameters more than 100μm are also linear. Based on the very obvious sub-nanometer C-AFM produced pictures the scientific evidence behind this controversy is also explained.     

Electrical and interfacial properties of Au/P3HT:PCBM/n-Si Schottky barrier diodes at room temperature

In this study, a 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 diode (SBD) was fabricated. To accomplish this, a spin-coating system and a thermal evaporation were used for preparation of a P3HT/PCBM layer system and for deposition of metal contacts, respectively. The forward- and reverse-bias current–voltage (I–V) characteristics of the MPS SBD at room temperature were studied to investigate its main electrical parameters such as ideality factor (n), barrier height (Φ_B), series resistance (R_s), shunt resistance (R_sh), and density of interface states (N_ss). The I–V characteristics have nonlinear behavior due to the effect of R_s, resulting in an n value (3.09) larger than unity. Additionally, it was found that n, Φ_B, R_s, R_sh, and N_ss have strong correlation with the applied bias. All results suggest that the P3HT/PCBM interfacial organic layer affects the Au/P3HT:PCBM/n-Si MPS SBD, and that R_s and N_ss are the main electrical parameters that affect the Au/P3HT:PCBM/n-Si MPS SBD. Furthermore, a lower N_ss compared with that of other types of MPS SBDs in the literature was achieved by using the P3HT/PCBM layer. This lowering shows that high-quality electronic and optoelectronic devices may be fabricated by using the Au/P3HT:PCBM/n-Si MPS SBD.     

Thermally annealed Ni/n-GaAs(Si)/In Schottky barrier diodes

We have identically prepared as many as eight Ni/n-GaAs/In Schottky barrier diodes (SBDs) using an n-type GaAs substrate with a doping density of about 7.3 × 10¹⁵ cm⁻³. The thermal stability of the Ni/n-GaAs/In Schottky diodes has been investigated by means of current-voltage (I-V) techniques after annealed for 1 min in N₂ atmosphere from 200 to 700 °C. For Ni/n-GaAs/In SBDs, the Schottky barrier height Φ_b and ideality factor n values range from 0.853 ± 0.012 eV and 1.061 ± 0.007 (for as-deposited sample) to 0.785 ± 0.002 eV and 1.209 ± 0.005 (for 600 °C annealing). The ideality factor values remained about unchanged up to 400 °C annealing. The I-V characteristics of the devices deteriorated at 700 °C annealing.     

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.     

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.     

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.     

Schottky barrier height modification in Au/n-type 6H-SiC structures by PbS interfacial layer

We have prepared the Au/PbS/n-6H-SiC Schottky diodes with interface layer and the reference Au/n-6H-SiC/Ni Schottky diodes without interface layer to realize Schottky barrier height (SBH) modification in the Au/SiC Schottky diodes. The BH reduction has been succeeded by the PbS interlayer to modify the effective BH by influencing the space charge region of the SiC. The PbS thin layer on the SiC was formed by the vacuum evaporation. The SBH values of 0.97 and 0.89 eV for the samples with and without the interfacial PbS layer were obtained from the forward bias current-voltage (I-V) characteristics. X-ray diffraction (XRD) study was carried out to determine the structural formation of the PbS on SiC. The reduction of the BH in the Au/PbS/n-6H-SiC Schottky diodes has been attributed to the fact that the interface states have a net positive interface charge in metal/n-type semiconductor contact, and thus the positive space charge Q_sc in the Au/PbS/n-6H-SiC Schottky diodes becomes smaller than if the interface state charges Q_ss were absent. The experimental carrier concentration value of 4.73 × 10¹⁷ cm⁻³ obtained from the forward and reverse bias capacitance-voltage characteristics for the Au/PbS/n-6H-SiC contacts is lower than the value of 5.52 × 10¹⁷ cm⁻³ obtained for the reference diode, and this is an evidence of the reduction of the BH by the modification of the space charge density of the SiC.     

Ballistic electron emission microscopy studies of the temperature dependence of Schottky barrier height distribution in CoSi2/n-Si(1 0 0) diodes formed by solid phase reaction

Ballistic electron emission microscopy (BEEM) and ballistic electron emission spectroscopy have been performed on polycrystalline and epitaxial CoSi₂/n-Si(1 0 0) contacts at temperatures ranging from −144°C to −20°C. The ultra-thin CoSi₂ films (10 nm) were fabricated by solid state reaction of a single layer of Co (3 nm) or a multilayer of Ti (1 nm)/Co (3 nm)/amorphous-Si(1 nm)/Ti (1 nm) with a Si substrate, respectively. The spatial distribution of barrier height over the contact area obeys a Gaussian function at each temperature. The mean barrier height increases almost linearly with decreasing temperature with a coefficient of −0.23±0.02 meV/K for polycrystalline CoSi₂/Si diodes and −0.13±0.03 meV/K for epitaxial diodes. This is approximately equal to one or one-half of the temperature coefficient of the indirect energy gap in Si, respectively. It suggests that the Fermi level is pinned to different band positions of Si. The width of the Gaussian distribution is about 30–40 meV, without clear dependence on the temperature. The results obtained from conventional current–voltage and capacitance–voltage (I–V/C–V) measurements are compared to BEEM results.     

Analysis of interface states and series resistance of MIS Schottky diodes using the current-voltage (I-V) characteristics

The purpose of this paper is to analyze interface states in Al/SiO₂/p-Si (MIS) Schottky diodes and determine the effect of SiO₂ surface preparation on the interface state energy distribution. The current-voltage (I-V) characteristics of MIS Schottky diodes were measured at room temperature. From the I-V characteristics of the MIS Schottky diode, ideality factor (n) and barrier height (Φ_B) values of 1.537 and 0.763 eV, respectively, were obtained from a forward bias I-V plot. In addition, the density of interface states (N_ss) as a function of (E_ss-E_v) was extracted from the forward bias I-V measurements by taking into account both the bias dependence of the effective barrier height (Φ_e), n and R_s for the MIS Schottky diode. The diode shows non-ideal I-V behaviour with ideality factor greater than unity. In addition, the values of series resistance (R_s) were determined using Cheung’s method. 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 MIS Schottky diodes.     

一种制备Au/n-Al0.3Ga0.7N横向肖特基二极管的方法

用MOCVD生长未掺杂n-Al0.3Ga0.7N制备了MSM结构紫外探测器,并通过电击穿MSM右边肖特基势垒而制成了横向肖特基二极管.器件在零偏电压处的背景光电流为87.3 pA.从器件的室温I-V特性曲线计算出理想因子n、零偏势垒高度B0和串联电阻RS分别为1.99、0.788 eV和10.2 kΩ.器件在305 nm波长处有陡峭的截止边,300 nm峰值波长处电流响应率为0.034 A/W.     

Electrical characteristics of high performance Au/n-GaN schottky diodes

Au/n-GaN Schottky diodes with the Au electrode deposited at low temperature (LT=77K) have been studied. In comparison, the same chip of GaN epitaxial layer was also used for room temperature Schottky diodes. The low temperature Schottky diodes exhibit excellent performance. Leakage current density as low as 2.55×10⁻¹¹ A·cm⁻² at −2.5 V was obtained in the LT Schottky diodes. The linear region in the current-voltage curve at forward bias extends more than eight orders in current magnitude. Current-voltage-temperature measurements were carried out to study the characteristics of the LT Schottky diodes. A typical barrier height of about 1.32 eV for the LT diode, which is the highest value ever reported, was obtained. The obvious enhancement in electrical performance makes the LT processing a very promising technique for GaN device application although the detailed mechanisms for the LT Au/n-GaN Schottky diodes are still under investigation.     

Unterminated 4H-SiC Schottky barrier diodes with novel HfNxBy electrodes

4H-SiC Schottky barrier diodes (SBDs) were fabricated and characterized from room temperature to 573 K using HfN_xB_y as Schottky electrodes. The results are compared to SBDs fabricated using other electrodes that include Ni, Pt, Ti and Au. The Schottky barrier height Φ_b for as-deposited HfN_xB_y/n−/n+ diodes, determined from room temperature current-voltage characteristics, is 0.887 eV. This is lower than those of SBDs fabricated using other metals such as Au, where Φ_b is 1.79 eV. The HfN_xB_y/n−/n+ diodes studied have a much higher on-resistance R_on of around 38.24 mΩ-cm², which is about four times that of Au/n−/n+ diodes, due to the higher sheet resistance of the sputtered HfN_xB_y electrode layer. The barrier height Φ_b and ideality factor η of the HfN_xB_y/n−/n+ diodes remain almost unchanged after 400 and 750 °C anneal in N₂. This suggests excellent thermal and chemical stability of HfN_xB_y in contact with 4H-SiC.     

The formation of elevated barrier height Schottky diodes to inp and In0.53Ga0.47as using thin,excimer laser-deposited Cd interlayers

Much recent attention has been paid to elevating the barrier height of contacts to InP and In_0.53Ga_{0. 47}As via the formation of a thin, intermediate layer between the semicon-ductor and a conventionally deposited, highly conductive contact layer. Here, we report on the use of thin (～200Å) excimer laser photodeposited Cd as an interlayer between these semiconductors and Au overlayers in order to raise the barrier height of the re-sulting diodes. Current-voltage measurements of ideal Schottky diodes fabricated using this process yield barrier heights of 0.70 eV and 0.55 eV to InP and In_0.53Ga_{0. 47}As, re-spectively. The photodeposition process has been integrated with conventional clean room processing resulting in Au/Cd/In_0.53Ga_{0. 47}As transistors with high transconductances (～200 mS/mm) and operating frequencies (f _max ～ 30 GHz). X-ray photoelectron spec-troscopy of thin Cd photodeposits on InP shows that the process produces an interfacial (～10Å thick) Cd-InP reaction zone covered by metallic Cd.     

The influence of high energy electron irradiation on the Schottky barrier height and the Richardson constant of Ni/4H-SiC Schottky diodes

The influence of high energy electron (HEE) irradiation from a Sr-90 radio-nuclide on n-type Ni/4H–SiC samples of doping density 7.1×10¹⁵ cm⁻³ has been investigated over the temperature range 40–300 K. Current–voltage (I–V), capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS) were used to characterize the devices before and after irradiation at a fluence of 6×10¹⁴ electrons-cm⁻². For both devices, the I–V characteristics were well described by thermionic emission (TE) in the temperature range 120–300 K, but deviated from TE theory at temperature below 120 K. The current flowing through the interface at a bias of 2.0 V from pure thermionic emission to thermionic field emission within the depletion region with the free carrier concentrations of the devices decreased from 7.8×10¹⁵ to 6.8×10¹⁵ cm⁻³ after HEE irradiation. The modified Richardson constants were determined from the Gaussian distribution of the barrier height across the contact and found to be 133 and 163 A cm⁻² K⁻² for as-deposited and irradiated diodes, respectively. Three new defects with energies 0.22, 0.40 and 0.71 eV appeared after HEE irradiation. Richardson constants were significantly less than the theoretical value which was ascribed to a small active device area.     

碲化镉肖特基势垒的温度依赖关系

本文通过对Au/n-CdTe肖特基二极管I-V-T测量得出:在室温附近,势垒高度随温度升高而线性增加,增加速率约为 9 ×10~(-4)eV/K.这一结果与 Hattori 等对InP的研究结果一致,     

两种不同结构n型GaN基肖特基二极管电学特性

实验研究了两种由ICP刻蚀不同结构的n型GaN材料与金属接触形成的肖特基二极管的I-V特性,分析计算了GaN基肖特基二极管的势垒高度和理想因子。研究发现n型GaN半导体材料表面费米能级钉扎,且费米能级的钉扎对n型GaN材料表面的金半接触所形成的肖特基势垒高度起决定性作用;结果表明表面经过ICP刻蚀后,n型GaN表面的氧化层消除,价带中态密度增多,有利于载流子的遂道效应与金属较易形成欧姆接触。