Schottky-type Diodes Research Articles

Series resistance study of Schottky diodes developed on 4H-SiC wafers using a contact of titanium or molybdenum

We have studied and compared two types of Schottky diodes prepared by the evaporation of molybdenum (Mo) and titanium (Ti) on a 4H-SiC semiconductor. The electrical characteristics of these diodes are analyzed based on the standard thermionic emission model. The main electrical parameters including the series resistance Rs, the ideality factor n and the barrier height @FB are extracted from current-voltage-temperature (I-V-T) measurements. In the Ti/4H-SiC structure, the series resistance increases from [email protected]?cm^2 to [email protected]?cm^2 when the temperature is varied from 70K to 450K. In contrast, the series resistance does not exceed a [email protected]?cm^2 at 450K in the Mo/4H-SiC Schottky diode. We have decomposed the series resistance into three components. The deduced static and dynamic parameters were used to define an electrical model. The switching behavior of the equivalent circuit indicates a reverse recovery time (Trr) of 1.412ns for Ti/4H-SiC and 3.27ns for Mo/4H-SiC.

Optimization of Chemical Structure of Schottky-Type Selection Diode for Crossbar Resistive Memory

The electrical performances of Pt/TiO(2)/Ti/Pt stacked Schottky-type diode (SD) was systematically examined, and this performance is dependent on the chemical structures of the each layer and their interfaces. The Ti layers containing a tolerable amount of oxygen showed metallic electrical conduction characteristics, which was confirmed by sheet resistance measurement with elevating the temperature, transmission line measurement (TLM), and Auger electron spectroscopy (AES) analysis. However, the chemical structure of SD stack and resulting electrical properties were crucially affected by the dissolved oxygen concentration in the Ti layers. The lower oxidation potential of the Ti layer with initially higher oxygen concentration suppressed the oxygen deficiency of the overlying TiO(2) layer induced by consumption of the oxygen from TiO(2) layer. This structure results in the lower reverse current of SDs without significant degradation of forward-state current. Conductive atomic force microscopy (CAFM) analysis showed the current conduction through the local conduction paths in the presented SDs, which guarantees a sufficient forward-current density as a selection device for highly integrated crossbar array resistive memory.

Few-atomic-layer boron nitride sheets syntheses and applications for semiconductor diodes

We report the results on the direct synthesis of crystalline boron nitride nanosheets (BNNS) and its application for metal/doped BNNS semiconductor-based Schottky type diode devices. Scanning transmission electron microscopy images reveal that we have obtained few-atomic-layer hexagonal boron nitride sheets with well-shaped edge. The crystallographic structure, chemical composition, and bond structure of the few-atomic-layer BNNS were investigated using electron microscopy and Raman scattering spectroscopy. Typical non-linear current–voltage properties of BNNS semiconductor based diode are characterized.

ZnO-based one diode-one resistor device structure for crossbar memory applications

This letter reports the development of a ZnO-based one diode-one resistor (1D1R) device consisting of a Pt/ZnO:Al/ZnO/Pt Schottky-type diode and a Pt/ZnO/Pt memristor using a room-temperature sputtering process. The proposed 1D1R device exhibits stable switching for more than 103 cycles, good retention up to 104 s at 85 °C, and desirable anti-crosstalk characteristics. Thus, the proposed design shows potential for integration in a crossbar memory array.

Preparation and electrical characterization of Au/n-Si (1 1 0) structure with PVA–nickel acetate composite film interfacial layer

Two types of Schottky diodes, with and without PVA (Ni-doped) layer, were fabricated to investigate whether or not the PVA (Ni-doped) layer is effective on some electrical parameters such as ideality factor n, barrier height [Formula: see text] , series resistance Rs, and interface state density NSS. PVA (Ni-doped) microdrops film was deposited on n-type silicon substrate. SDs with and without PVA (Ni-doped) layer, namely MPS and MS diodes, respectively, were investigated by current–voltage ( I–V) measurements at room temperature. Also, series resistance calculations have been performed using Cheung method. The values of n and Rs obtained for MPS are found higher compared to those of MS. This is attributed to the particular distribution of NSS, and inhomogeneity of barrier height and interfacial layer at metal/semiconductor (M/S) interface. Au/PVA(Ni-doped)/n-Si diode (MPS) exhibits a photovoltaic behavior with an open circuit voltage Voc 0.42 V and short-circuit current ISC 33.2 µA under 100 mW/cm2 illumination intensity. The obtained photovoltaic results indicate that the MPS diode can be used as an efficient material for applications in optoelectronic applications such as solar cells and photodiode devices.

Fast response hydrogen sensors based on palladium and platinum/porous 3C-SiC Schottky diodes

Porous 3C-SiC (pSiC) samples with an average pore diameter of 30 nm were prepared by electrochemical anodization. Planar type Schottky diodes were fabricated using 1-mm diameter Au contact metal where the Au dot was chemically modified via the sputtering of Pd and Pt for use as a hydrogen catalyst. Changes in the current were monitored with respect to hydrogen concentration in the range of 10–40 ppm with a 3.7 V forward bias. The variations in current in the presence of hydrogen demonstrated that Pd and Pt/Au/pSiC samples have the ability to detect hydrogen. In the case of Pd, the response and recovery time at room temperature were 2.3 and 1.5 s, respectively. A large change in current was observed with the Pd catalyst, and the hydrogen sensing performance improved at high temperatures.

Understanding the Role of Process Parameters on the Characteristics of Transition Metal Oxide RRAM/Memristor Devices

ABSTRACTIn this report, we studied the role of the oxygen concentration in TiOx layer of Ni/TiOx/TiO2/Ni stack based 2-terminal resistive random access memory (RRAM) devices. The sample with oxygen deficient TiOx layer showed Schottky diode type J-V characteristics in the as-fabricated state while the sample with higher oxygen content in TiOx demonstrated MIM or back-to-back connected diode behavior. The Capacitance-Voltage (C-V) profiling was performed and doping density vs. depletion width characteristic was obtained. The conductance technique was implemented to study the interface state density. The RRAM type switching behavior of these samples was studied. The sample with high oxygen in TiOx showed filament based switching after electroforming while the sample with low oxygen in TiOx showed switching governed by the charge trapping.

Diode-Like Properties of As-Grown Chemical Vapor Deposited Single-Walled Carbon Nanotubes

Current rectification property of as-grown single-walled carbon nanotubes (SWNTs) is investigated. The SWNTs are grown by chemical vapor deposition (CVD) process. The process allowed to grow long strands of SWNT bundles, which are then used to fabricate multiple arrays of switching devices with the channel length of 3, 5, 7 and 10 microm on a 15 mm x 15 mm SiO2 on Si substrate. Regardless of the channel length, a majority of the fabricated devices show current rectification characteristics, with high throughput of current (I) in the forward bias (V) giving the forward and reverse current ratio (Ifor/Irev) of approximately 10(6). Atomic force microscopic (AFM) analysis of the device structure and surface topology of SWNT suggest the observed rectification of current to possibly result from (a) cross-tube junctions, (b) a mixture of metallic and semiconducting tubes in the SWNT bundles, and/or (c) chirality change along a single tube. The exact mechanism underlying the observed rectification could not be conclusively established. However, the analyses of the experimental results strongly suggest the observed rectification to result from Schottky-type diode properties of SWNTs with mixed chirality along the tube.

Neutron irradiation effects on I–V characteristics of Au/n-GaAs Schottky diodes

Diodes are one of the most important and widely used components of electronic circuits. These devices can be damaged especially when they are used in radiation fields whose effects depend on radiation type and energy. To investigate these effects, the Au/n-GaAs type Schottky diodes have been irradiated by neutrons emitted from a 252 Cf source which provides neutrons at an average energy of 2.14 MeV. The diode parameters barrier height (Φ b 0 ), ideality factor ( n ) and series resistance ( R s ) have been obtained from forward current–voltage ( I–V ) characteristics before and after irradiation and the results are discussed.

A Pt/TiO2/Ti Schottky-type selection diode for alleviating the sneak current in resistance switchingmemory arrays

This study examined the properties of Schottky-type diodes composed ofPt/TiO2/Ti, wherethe Pt/TiO2 and TiO2/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection devicefor a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of ∼ 109 was achieved at1 V when the TiO2 filmthickness was 19 nm. TiO2 film was grown by atomic layer deposition at a substrate temperature of250 °C. Conductive atomic force microscopy revealed that the forward currentflew locally, which limits the maximum forward current density to < 10 A cm − 2 for a large electrode(an area of ∼ 60 000 µm2). However, the local current measurement showed a local forward current density as high as ∼ 105 A cm − 2. Therefore, it is expected that this type of Schottky diode effectively suppresses the sneakcurrent without adverse interference effects in a nano-scale resistive switching cross-bararray with high block density.

Structural, electrical and magnetic characterizations of Ni/Cu/p-Si Schottky diodes prepared by liquid phase epitaxy

In this paper, we have investigated the structural, electrical and magnetic characterizations of Ni/Cu/p-Si Schottky diode prepared by liquid phase epitaxy (LPE). Current density–voltage ( J– V), capacitance–voltage ( C– V) and capacitance–frequency ( C– f) measurements were performed to determine the conduction mechanisms as well as extracting the important diode parameters. Rectifying properties were obtained, which definitely of the Schottky diode type. At low voltages, (0 < V ⩽ 0.4 V), current density in the forward direction was found to obey the diode equation, while for higher voltages, (0.5 < V ⩽ 1.5 V), conduction was dominated by a space-charge-limited conduction (SCLC) mechanism. Analysis of the experimental data under reverse bias suggests a transition from electrode-limited to a bulk-limited conduction process for lower and higher applied voltages, respectively. Diode parameters such as, the built-in potential, V b, the carrier concentration, N, the width of the depletion layer, W, of the Ni/Cu/p-Si Schottky diode were obtained from the C– V measurements at high frequency (1 MHz). The capacitance–frequency measurements showed that the values of capacitance were highly frequency dependent at low frequency region but independent at high frequencies. The Ni/Cu/p-Si Schottky diode showed magnetic properties due to the effect of Ni in the heterostructure.

Investigation of the electrical properties of a surface-type Al/NiPc/Ag Schottky diode using I– V and C– V characteristics

Electrical properties of Al/NiPc/Ag surface type Schottky diode fabricated by vacuum thermal evaporation have been investigated. The current–voltage ( I– V) and capacitance–voltage ( C– V) characteristics are measured at room temperature in dark. The electronic parameters such as ideality factor, barrier height, series resistance and shunt resistance of the Schottky diode are calculated from the current–voltage and capacitance–voltage characteristics. The charge carrier concentration and built in potential values of 9.1×10 15 cm −3 and 1.6 V, respectively, are obtained from the C– V plot. The value of conductivity and mobility has also been calculated. In addition, the values of ideality factor and series resistance are also verified by using Cheung's function. Frequency-dependent measurements on this Schottky barrier diode show that the capacitance is reduced at high frequency.

Capabilities of CdZnTe‐based Schottky diodes for detection of optical and X/γ‐ray radiation

AbstractThe electrical and photoelectric properties of Schottky diodes based on low‐resistivity (ρ = 103‐104 Ω·cm) and semi‐insulating (ρ ≈ 107 Ω·cm) Cd1‐xZnxTe (x = 0‐0.2) single crystals are investigated and use of the diodes as detectors, respectively, for optical and X‐ and γ‐ray radiation is analyzed. The charge transport properties of both types of Schottky diodes are shown to be governed by generation‐recombination in the space‐charge region in the frame of the Sah‐Noyce‐Shockley theory. The detection spectrum of Cd1–x Znx Te‐bassed X/γ‐ray detectors with Schottky diodes is studied. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Modulation of rectifying behaviour by oxygen contents in La0.5Sr0.5CoO3−δ/0.7 wt% Nb-doped SrTiO3 heterojunctions

Heterojunctions composed of La0.5Sr0.5CoO3−δ and 0.7 wt% Nb-doped SrTiO3 were deposited at different oxygen partial pressures and display opposite rectifying shapes: the junctions fabricated at a lower oxygen pressure show a backward shape and they gradually display a forward shape by tuning up the oxygen partial pressures. The former tends to form degenerate p–n junctions due to oxygen deficiency, which is responsible for the backward rectifying shape. The latter, however, can be viewed as a Schottky-type diode. The oxygen contents for the junctions can be estimated from their x-ray diffraction patterns, and are also confirmed from their resistance and magnetization measurements.

The distribution of barrier heights in MIS type Schottky diodes from current–voltage–temperature ( I– V– T) measurements

The forward bias current–voltage–temperature ( I– V– T) characteristics of the Au/SiO 2/n-Si (MIS) type Schottky diodes (SDs) have been investigated in the temperature range of 300–400 K. The estimated zero-bias barrier height ( Φ B0) and the ideality factor ( n) assuming thermionic emission (TE) theory show strong temperature dependence. An abnormal decrease in the Φ B0 and an increase in the n with decreasing temperature have been explained on the basis of the TE theory with a Gaussian distribution (GD) of the barrier heights (BHs) due to BH inhomogeneities. The conventional Richardson plot should be a straight line especially at intermediate temperatures ( T ≤ 325). The values of activation energy ( E a) and Richardson constant ( A *) were determined as 0.167 eV and 1.385 × 10 −6 A cm −2 K −2 from the slope and the intercept at ordinate of the linear region of this plot, respectively. Also, we attempted to draw a Φ B0 versus q/2 kT plot in order to obtain evidence of the GD of BHs, and the values of Φ ¯ B0 = 1.301 eV and σ s = 0.187 V for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively; then, a modified ln ( I 0 / T 2 ) − q 2 σ s 2 / 2 k 2 T 2 versus q/ kT plot gives Φ ¯ B0 and A * as 1.298 eV and 109.481 A cm −2 K −2, respectively. This value of the A * (=109.481 A cm −2 K −2) is very close to the theoretical value of 112 A cm −2 K −2 for n-type Si. Therefore, it has been concluded that the temperature dependence of the forward bias I– V characteristics of the MIS type Schottky diodes can be successfully explained on the basis of TE mechanism with a GD of the BHs.

Gaussian distribution of inhomogeneous barrier height in Al/SiO2/p-Si Schottky diodes

The forward and reverse bias current-voltage (I-V) characteristics of Al/SiO2/p-Si (metal-insulator-semiconductor) type Schottky diodes (SDs) were measured in the temperature range of 200–400 K. Evaluation of the experimental I-V data reveals a decrease in ΦB0 and Rs but an increase in n, with a decrease in temperature. To explain this behavior of ΦB0 with temperature, we have reported a modification which included n and the tunneling parameter αχ1/2δ in the expression of reverse saturation current I0. Thus, a corrected effective barrier height ΦB eff(I-V) vs T has a negative temperature coefficient (α≈−5×10−4 eV/K), and it is in good agreement with α=−4.73×10−4 eV/K of Si band gap. Such behavior of Rs estimated from Cheung’s method could be expected for semiconductors in the temperature region, where there is no carrier freezing out, which is non-negligible at low temperatures. Also, there is a linear correlation between ΦB0(I-V) and n due to the inhomogeneities of the barrier heights (BHs). The conventional activation energy (Ea) plot exhibits nonlinearity below 320 K with the linear portion corresponding to Ea of 0.275 eV. An A∗ value of 1.45×10−5 A cm−2 K−2,which is much lower than the known value of 32 A cm−2 K−2 for p-type Si, is determined from the intercept at the ordinate of this experimental plot. Such behavior is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution (GD) of BHs due to BH inhomogeneities that prevail at the interface. We attempted to draw a ΦB0 vs q/2kT plot to obtain evidence of a GD of the BHs, and the values of Φ¯B0=1.136 eV and σ0=0.159 V for the mean BH and standard deviation at zero bias have been obtained from this plot. Therefore, the modified ln (I0/T2)−q2σ02/2k2T2 vs q/kT plot gives Φ¯B0 and A∗ values of 1.138 eV and 37.23 A cm−2 K−2, respectively, without using the temperature coefficient of the BH. This A∗ value of 37.23 A cm−2 K−2 is very close to the theoretical value of 32 A K−2 cm−2 for p-type Si. Therefore, it has been concluded that the temperature dependence of the forward bias I-V characteristics of the Al/SiO2/p-Si SDs can be successfully explained based on the thermionic emission mechanism with a GD of the BHs.

( In , Sn ) 2 O 3 ∕ Ti O 2 ∕ Pt Schottky-type diode switch for the TiO2 resistive switching memory array

A Schottky-type diode switch consisting of a Pt∕(In,Sn)2O3∕TiO2∕Pt stack was fabricated for applications to cross-bar type resistive-switching memory arrays. The high (0.55eV) and low potential barrier at the TiO2∕Pt and TiO2∕(In,Sn)2O3 junctions, respectively, constitute the rectifying properties of the stacked structure. The forward/reverse current ratio was as high as ∼1.6×104 at an applied voltage of ∼1V. When Pt∕TiO2∕Pt memory was connected to this diode in series, there was an insignificant interference on the memory function from the diode under the forward bias and virtually no resistive switching under a reverse bias.

Dielectric properties and ac electrical conductivity studies of MIS type Schottky diodes at high temperatures

Dielectric properties and ac electrical conductivity of the Al/SiO 2/p-Si (MIS) Schottky diodes were studied in the frequency and temperature range of 10 kHz–1 MHz and 300–400 K, respectively. Experimental results show that the dielectric constant ( ε′), dielectric loss ( ε″), loss tangent (tan δ), ac electrical conductivity ( σ ac) and the electric modulus were found a strong function of frequency and temperature. The values of the ε′, ε″ and tan δ decrease with increasing frequencies due to the interface states capacitance and a decrease in conductance with increasing frequency. Also, these values increase with increasing temperature. The σ ac is found to increase with increasing frequency and increasing temperature. The variation of conductivity as a function of temperature and frequency reveals non-adiabatic hopping of charge carriers between impurities localized states. In addition, the experimental dielectric data have been analyzed by considering electric modulus formalism.

Electrical characterization of 4H–SiC Schottky diodes with a RuO2 and a RuWO x Schottky contacts

Two types of Schottky diodes were prepared on n-type silicon carbide (4H–SiC) substrates by deposition of ruthenium oxide (RuO2) Schottky contacts or ruthenium tungsten oxide (RuWO x ) Schottky contacts. The RuO2/4H–SiC and RuWO x /4H–SiC Schottky barrier diodes were examined first by current–voltage (I-V) measurements, which confirmed symmetry of the I-V characteristics. The ideality factor (n) is rather high (∼1.28/∼1.15) at the temperature 300 K, the current of saturation is I S ∼10 pA/∼7 pA and the Schottky barrier height is ∼1.13 eV/∼1.11 eV. After this diagnostic step, the samples were analysed by C-V and standard DLTS methods in the temperature range from 83 K to 450 K. In measured DLTS spectra were identified five deep levels ET1–ET5 (0.27, 0.45, 0.56, 0.58 and 0.85 eV) in RuO2/4H–SiC Schottky barrier diodes and three deep levels E1–E3 (0.36, 0.38 and 0.69 eV) in RuWO x /4H–SiC Schottky barrier diodes.

The effect of series resistance and oxide layer formed by thermal oxidation on some electrical parameters of Al/SiO 2/p-Si Schottky diodes

Two types of Schottky diodes with and without thermal-growth oxide layer, were fabricated to investigate whether or not the thermal-growth oxide layer is effective on some electrical parameters such as ideality factor n, barrier height Φ B, series resistance R s and interface state density N ss. The current–voltage ( I– V) characteristics were measured for these two diodes at 150 K and room temperature (300 K). Electrical parameters of these two diodes were calculated and compared at two temperatures. At the temperatures of 150 and 300 K, Φ B, n, and R s for diode without oxide layer ranged from 0.50 to 0.81 eV, 4.12 to 1.54, and 481 to 156 Ω respectively. The Φ B, n, and R s for diode with thermal-growth oxide layer have ranged from 0.54 to 0.87 eV, 6.83 to 1.66, and 503 to 281 Ω, respectively. For two diodes, the temperature dependence energy density distribution profiles of interface state were obtained from forward bias I– V measurements by taking into account the bias dependence of effective barrier height Φ e and R s of the devices and the value of N ss in diode without oxide layer is almost one order of magnitude larger than the diode with oxide layer.