Barrier Inhomogeneities Research Articles

Study on the effect of singlewalled carbon nanotubes on junction properties of Safranin –T dye-based organic device

In this work, junction properties of metal-organic dye contact have been studied and alteration of these properties in presence of single walled carbon nanotubes has been observed. Junction properties of metal-organic interface significantly influence the device performance. Present work studies barrier potential and trap energy under the influence of single walled carbon nanotubes. Barrier inhomogeneity and the effect of image charge on lowering of barrier potential have also been studied. Formation of the organic device has been done by sandwiching Safranin - T dye in between two electrodes which are Indium Tin Oxide coated glass substrate and Aluminium respectively. Charge flow at the metal–organic layer interface has been analyzed by Richardson –Schottky thermionic emission theory. Both barrier potential and trap energy have been estimated from the steady-state current-voltage characteristics of the device. The incorporation of single walled carbon nanotubes lowers both of these parameters results in improvement of current flow at the metal-organic contact.

Detailed experimental and theoretical analysis of the high-temperature current conduction properties of Er-doped TiO2 thin film based diodes

The high-temperature (303 K to 413 K) current conduction properties of Au/TiO2/p-Si (undoped) and Au/Er:TiO2/p-Si (doped) Schottky barrier diodes (SBDs) were analyzed. The barrier height (Фb0) increased, whereas the ideality factor (n) and series resistance (RS) decreased for these devices with increasing temperature. The activation energy as well as Richardson constant (A*) were determined from the temperature-dependent Richardson plot (R-plot). The calculated values of A* are much lower than the reported value. This behavior was clarified by assuming the barrier inhomogeneities and considering a Gaussian distribution (GD) of barrier height (BH). GD analysis modified the R-plots. The estimated standard deviation (σ0) value decreased from 0.18 (for undoped) to 0.17 (for the doped device), which indicates the reduction in barrier inhomogeneity. Also, the calculated mean values of Фb0 and A* are 1.41 eV and 871 A/(cm2K2) for undoped, 1.46 eV and 402 A/(cm2K2) for the doped device, respectively. The values of A* are much closer to the reported value of 671 A/(cm2K2) for TiO2. Therefore, it is evident that this analysis using the thermionic emission (TE) theory and considering a GD of BH elucidated the I–V characteristics of the SBDs. Other device parameters like bandgap variation with temperature, carrier concentration, Fermi energy, and RC constant were theoretically determined. Further, a unique technique has been developed to calculate the interface trap density profiles using the I–V characteristics of the devices. Hence, it is manifested that the temperature-dependent I–V characteristic can be used as a robust tool to analyze all possible vital parameters of the device.

Barrier height nature and photovoltaic properties of (2-(2-(2-nitrophenyl)diazenyl)malononitrile)/p-Si heterojunction

Small molecule, (2-(2-(2-nitrophenyl)diazenyl)malononitrile) (NPDAM), is synthesized and its chemical structure is characterized by different analyses. NPDAM powder is identified as polycrystalline monoclinic structure, whereas the thermally deposited films have nanostructure character with average particle size of 39 nm. NPDAM films are utilized for manufacturing hybrid solar cells in the structure of Au/NPDAM/p-Si/Al. The dark current-voltage (I-V) curves of the diode are measured in the temperature range 303-383 K and the thermionic emission theory is employed to extract the ideality factor, n, and potential barrier height, ∅ at forward applied voltages of V≤0.20 volt. The n value increases, whereas the ∅ value decreases with decreasing temperature. This behavior is analyzed in terms of the lateral inhomogeneous barrier following Gaussian distribution at the NPDAM/p-Si interface. Cheung and Cheung functions are used for extracting the values of series resistance, Rs, n and ∅. The behavior of these parameters as a function of temperature is discussed. At forward applied voltages 0.20<V≤2, the I-V relation reveals crossover from thermionic emission to square power law. This behavior is discussed by means of the space charge limited current. Under illumination, the device exhibits a response to light exposure with a photoelectrical conversion efficiency of 2.91 %.

Electrical transport properties of thermally stable n-ZnO/AlN/p-Si diode grown using RF sputtering

The temperature dependent electrical transport properties of n-ZnO/AlN/p-Si heterojunction diode fabricated by RF sputtering system have been investigated over a wide temperature range of 303 K–413 K. The AlN buffer layer in-between ZnO and Si lowers the mismatch in thermal expansion coefficient/lattice constant for improved electrical and structural characteristics. XRD pattern and FESEM confirm the crystalline nature and good quality of ZnO thin film with uniform grain size and crack free structure respectively. As measured from the temperature dependent I–V curve, the apparent barrier height reduces as Ideality factor rises which shows good thermal stability within the temperature range studied here. The mean value of barrier height as well as the Richardson constant have been evaluated. Additionally, by taking into account the Gaussian distribution of inhomogeneous barrier heights, the modified Richardson constant has been estimated.

Effect of Temperature on the Electrical and Current Transport Properties of Au/Nd2O3/n-GaN Metal/Interlayer/Semiconductor (MIS) Junction

The Au/Nd2O3/n-type GaN metal/interlayer/semiconductor (MIS) junctions were fabricated with high-k rare-earth oxide interlayer and explored its electrical properties in the wide temperature range of 150–400 K. An anomalous decrease in barrier height and an increase in the ideality factor with a decrease in the temperature were observed. The anomalous barrier height and ideality factor are ascribed to a role of barrier inhomogeneities at the interface of MIS junction assuming a double Gaussian distribution of barrier heights in the temperature ranges of 150–225 K and 225–400 K. Double Gaussian distribution giving mean barrier heights of 0.84 eV and 1.23 eV and standard deviations of 0.0085 V and 0.0187 V for the two temperature regions. A modified conventional energy plot gives mean barrier height $$\left( {\overline{\Phi }_{bo} } \right)$$ and Richardson constant (A*) as 0. eV and 13.44 Acm−2 K−2 (150–225 K) and 1.23 eV and 22.85 Acm−2 K−2 (250–400 K), respectively. The estimated A* value in the temperature range of 250–400 K was closely matched with the theoretical value of n-type GaN. Moreover, results express that the obtained interface state density of the MIS junction decreases with increasing temperature. Results explained that the reverse current conduction governed by Poole–Frenkel emission at the temperature range of 150–225 K and Schottky emission at 250–400 K, respectively.

Impact of doping on the performance of p-type Be-doped Al0.29 Ga0.71As Schottky diodes

The effects of changing the acceptors concentration on the electrical characteristics of Au/Ti on Be-doped Al0.29Ga0.71As Schottky contact have been investigated in the temperature range of 100—400 K. Using three devices with three different doping levels, the barrier height (ΦB), ideality factor (n) and series resistance (RS) for each diode were evaluated using both thermionic emission (TE) theory and Cheung's method. Our experimental results showed that the sample with a moderate doping concentration of 3 · 1016 cm-3 has the best performance, including ideality factor of 1.25 and rectification ratio of 2.24 · 103 at room temperature. All samples showed an abnormal behavior of reducing ΦB and increasing n with increase of temperature. This behavior was attributed, in case of low concentration samples, to barrier inhomogeneity and was explained by assuming a Gaussian distribution of barrier heights at the interface. While for the heavily doped sample, such non-ideal manner was ascribed with tunneling through the field emission (FE) mechanism.

Atomic Layer Deposition of ZnO for Modulation of Electrical Properties in n-GaN Schottky Contacts

ZnO films (5 nm and 20 nm) have been grown on GaN single-crystal substrates by thermal atomic layer deposition (ALD) and the electrical properties of n-GaN Schottky contacts modified by such ultrathin ZnO films have been characterized. Compared with 5-nm-thick ZnO, 20-nm-thick ZnO exhibited a better rectifying nature. The average barrier height and ideality factor at room temperature were extracted to be 0.64 eV and 2.33 eV, and 1.01 eV and 1.16 eV, for 5-nm- and 20-nm-thick ZnO, respectively. These results indicate that both the barrier height and ideality factor were altered effectively by changing the ZnO thickness. The temperature-dependent reverse current–voltage (I–V) characteristics revealed that tunneling was dominant for the 5-nm-thick ZnO. A laterally inhomogeneous barrier was appropriate to explain the forward I–V characteristics for both samples. Based on the parallel conductance method and forward I–V data, a lower interface state density was observed for 20-nm-thick ZnO, implying improved interface quality. These results suggest that the electrical properties of n-GaN Schottky contacts could be easily modulated by changing the ZnO thickness.

Multiple machine learning approach to characterize two-dimensional nanoelectronic devices via featurization of charge fluctuation

Two-dimensional (2D) layered materials such as graphene, molybdenum disulfide (MoS2), tungsten disulfide (WSe2), and black phosphorus (BP) provide unique opportunities to identify the origin of current fluctuation, mainly arising from their large surface areas compared with those of their bulk counterparts. Among numerous material characterization techniques, nondestructive low-frequency (LF) noise measurement has received significant attention as an ideal tool to identify a dominant scattering origin such as imperfect crystallinity, phonon vibration, interlayer resistance, the Schottky barrier inhomogeneity, and traps and/or defects inside the materials and dielectrics. Despite the benefits of LF noise analysis, however, the large amount of time-resolved current data and the subsequent data fitting process required generally cause difficulty in interpreting LF noise data, thereby limiting its availability and feasibility, particularly for 2D layered van der Waals hetero-structures. Here, we present several model algorithms, which enables the classification of important device information such as the type of channel materials, gate dielectrics, contact metals, and the presence of chemical and electron beam doping using more than 100 LF noise data sets under 32 conditions. Furthermore, we provide insights about the device performance by quantifying the interface trap density and Coulomb scattering parameters. Consequently, the pre-processed 2D array of Mel-frequency cepstral coefficients, converted from the LF noise data of devices undergoing the test, leads to superior efficiency and accuracy compared with that of previous approaches.

Memristiv effect on W/Ti/p-Si structure: Aging phenomena and one of the origin of barrier inhomogeneity

Memristor as claimed to be fourth two terminal passive devices in electronics. Experimental realization memristor by HP research group is getting much more attention due to its potential applications. However, in reality this device with its unique properties always exist in MOS, MIS or even MS junctions. But its visibility has a dependence to oxide or interface thickness with mobile ions. As reported in this study, current–voltage (I-V) relation of W/Ti/p-Si continuously modified by the forward bias current. Departure form linear relation between ln(I)-V commonly analyzed with barrier inhomogeneity assumption. The appearance of barrier inhomogeneity for MS junction reported to be one of the reasons for non-ideal ln(I)-V relation. Investigation in this study shows that total charge Q(t) controlled by voltage sweep rate effecting forward ln(I)-V relation. If this situation exists, calculated barrier heights and ideality factors are not true and a pure barrier inhomogeneity approximation may not be applicable. However, under the reverse bias condition, the total charge during entire measurement is so small which it’s effect negligible over I-V relation as observed. The one of the solution is the use Missous-Rhoderick method for finding Schottky diode parameters or creating current stress over MS junction which saturates mobile ion drift. Voltage sweep rate during I-V measurement and hence total charge, affecting current transport and in parallel appearance of hysteresis loop indicate interface layer which behave as a memristor.

Determining the potential barrier presented by the interfacial layer from the temperature induced I–V characteristics in Al/p-Si Structure with native oxide layer

The temperature induced current-voltage (I–V-T) characteristics of the Al/SiO2/p-Si diodes with the interfacial native oxide layer were experimentally investigated in present our study. The values of 24.35 and 1.02 eV for the tunneling factor (aδχ) and the potential barrier presented by the interfacial layer (χ) were determined for the Al/SiO2/p-Si metal-insulator-semiconductor (MIS) diode. The χ value obtained from the forward bias I–V-T characteristics of the SiO2/p-Si diode is a crucial result according to those from only room temperature I–V curves in literature studies. Furthermore, the temperature dependence of the apparent barrier heights of the forward bias I–V-T characteristics displayed a Gaussian distribution (GD) of inhomogeneous barrier heights (BHs). Thus, the standard deviation values of σ1s0=147.65 mV for high temperature range and σ2s0=83.66 mV for low temperature range were obtained from the GD plot of the BHs (the apparent BH versus (2kT)−1 plot). Again, for the mean barrier height Φ‾b0 from the GD plot of the BHs, the values of 1.16 eV and 0.70 eV were obtained from the high temperature region and low temperature region, respectively. Furthermore, the Richardson constant values of 54.66 and 58.42 A/K2cm2 from these temperature regions are approximately 1.70 times higher than the theoretical value of 32 A/K2cm2 of the p-type Si semiconductor.

Direct metal contacts printing on 4H-SiC for alpha detectors and inhomogeneous Schottky barriers

Electrical characterization of several 4H-SiC Schottky diodes with Aerosol-Jet printed gold (Au), silver (Ag), and platinum (Pt) contacts was performed using forward and reverse current–voltage (IV) measurements. From these measurements, device parameters such as Schottky barrier height and ideality factor were determined; however, many of the devices exhibited nonideal behavior and inferior performance characterized by ideality factors significantly greater than one, disproportionate low voltage leakage current and low barrier heights. Forward current–voltage (FIV) characteristics were fitted to an inhomogeneous barrier height theory to explain the abnormal behavior exhibited by the printed devices. Transmission electron microscopy (TEM) of the device cross-sections was performed to investigate the printed metal and semiconductor epitaxial layer interface, which revealed the imperfections in the metal–semiconductor contact. Despite these irregularities, alpha radiation detection capability of these devices was still achieved with an energy resolution of 1.89% at 5.486 MeV, and the best achievable resolution at 0.51% with no energy degradation of 5.486 MeV.

Temperature dependence of conduction and low frequency noise characteristics in GaN Schottky barrier diodes

In this paper, the forward bias conduction and low frequency noise (LFN) characteristics of GaN Schottky barrier diodes (SBDs) have been measured and studied in the temperature range from 300 K to 450 K. Based on I–V measured results, the temperature dependence of ideality factor and zero bias Schottky barrier height reveals the inhomogeneities of Schottky barriers at the metal-semiconductor (MS) interface. Further study of the LFN measured results shows that the flicker noise ([Formula: see text] noise) is the main component of LFN in GaN SBDs. The current dependence of LFN indicates the influences of the Schottky barrier and the series resistance on [Formula: see text] noise, and the temperature dependence of LFN is analyzed according to Luo’s model and the barrier inhomogeneities model.

The effect of temperature on the forward bias electrical characteristics of both pure Ni and oxidized Ni/Au Schottky contacts on n-type GaN: A case study

The forward bias current-voltage (I-V) characteristics of both oxidized Ni/Au and pure Ni metal Schottky contacts on n-type GaN have been investigated in the temperature range 160–400 K. The I-V curves were fitted using thermionic emission (TE) theory. It was found that the zero-bias barrier height (ϕb0) decreases while the ideality factor (η) increases with decreasing temperature (i.e. To effect). As a result, various transport models are considered in the analysis of the I-V experimental data in order to explain the observed anomaly in η and ϕb0. The deviation from linearity in the To effect plot for oxidized Ni/Au can be explained in terms of Schottky barrier height (SBH) inhomogeneity. As a result, a linear correlation between the zero-bias barrier height and ideality factor at different temperatures was found using Tung’s theoretical approach in order to extrapolate the homogenous barrier height (ϕhom). For oxidized Ni/Au, it was found that there are two distinct ϕhom values with one representing the low temperature range (ϕhom_1 = 1.02 eV) and another representing the high temperature range (ϕhom_2 = 1.23 eV). However, for pure Ni, there is no inhomogeneity in the barrier height (i.e. ϕhom = 0.87 eV). Furthermore, the ϕb0-ap vs. q/(2kT) plot also shows evidence of a Gaussian distribution of barrier heights for both oxidezed Ni/Au (ϕb0-mean = 1.45 eV and σs = 141 mV) and pure Ni (ϕb0-mean = 0.92 eV and σs = 69.3 mV). The 1/η vs. 1000/T plot is constructed to investigate the different current transport mechanisms in both oxidized Ni/Au and pure Ni. These various current transport mechanisms at different temperatures can be attributed to the barrier inhomogeneity at the metal–semiconductor interface.

Properties of a facile growth of spray pyrolysis-based rGO films and device performance for Au/rGO/n-InP Schottky diodes

In this study, the reduced graphene oxide (rGO) was synthesized from graphene oxide (GO) by using chemical reduction method. The spray pyrolysis technique was used to deposit rGO film on n-InP substrate. The structural, morphological, and optical properties of rGO film were investigated by XRD, SEM, and UV–Vis spectroscopies. Au/rGO/n-InP device was fabricated and the current–voltage characteristics were examined in the temperature range of 60–300 K. The device parameters of barrier height (BH) and ideality factor are found to be strong functions of temperature due to the barrier inhomogeneities at metal–semiconductor interface. The temperature dependency of the electrical characteristics of the Au/rGO/n-InP SBD was explained by the thermionic field emission (TFE) theory with Gaussian distribution (GD) of the BH values. The BH has a GD with a mean barrier height of $$\overline{\Phi }_{bo}$$ = 0.93 eV between 120 and 300 K temperatures and $$\overline{\Phi }_{bo}$$ = 0.62 eV between 60 and 120 K temperatures. It was seen that the existing current mechanism is predominantly controlled by space-charge-limited current (SCLC) at large forward bias according to the sample temperature. The rGO interface plays also an important role in the conduction mechanism and electronic properties of the device.

Seismic velocity structure at the southern termination of the 2016 Kumamoto Earthquake rupture, Japan

The earthquake rupture termination mechanism and size of the ruptured area are crucial parameters for earthquake magnitude estimations and seismic hazard assessments. The 2016 Mw 7.0 Kumamoto Earthquake, central Kyushu, Japan, ruptured a 34-km-long area along previously recognized active faults, eastern part of the Futagawa fault zone and northernmost part of the Hinagu fault zone. Many researchers have suggested that a magma chamber under Aso Volcano terminated the eastward rupture. However, the termination mechanism of the southward rupture has remained unclear. Here, we conduct a local seismic tomographic inversion using a dense temporary seismic network to detail the seismic velocity structure around the southern termination of the rupture. The compressional-wave velocity (Vp) results and compressional- to shear-wave velocity (Vp/Vs) structure indicate several E–W- and ENE–WSW-trending zonal anomalies in the upper to middle crust. These zonal anomalies may reflect regional geological structures that follow the same trends as the Oita–Kumamoto Tectonic Line and Usuki–Yatsushiro Tectonic Line. While the 2016 Kumamoto Earthquake rupture mainly propagated through a low-Vp/Vs area (1.62–1.74) along the Hinagu fault zone, the southern termination of the earthquake at the focal depth of the mainshock is adjacent to a 3-km-diameter high-Vp/Vs body. There is a rapid 5-km step in the depth of the seismogenic layer across the E–W-trending velocity boundary between the low- and high-Vp/Vs areas that corresponds well with the Rokkoku Tectonic Line; this geological boundary is the likely cause of the dislocation of the seismogenic layer because it is intruded by serpentinite veins. A possible factor in the southern rupture termination of the 2016 Kumamoto Earthquake is the existence of a high-Vp/Vs body in the direction of southern rupture propagation. The provided details of this inhomogeneous barrier, which are inferred from the seismic velocity structures, may improve future seismic hazard assessments for a complex fault system composed of multiple segments.

On the Multi-parallel Diodes Model in Au/PVA/n-GaAs Schottky Diodes and Investigation of Conduction Mechanisms (CMs) in a Temperature Range of 80–360 K

Au/PVA/n-GaAs (MPS) type Schottky diodes (SDs) were fabricated and investigated in a temperature range of 80–360 K to explain their possible conduction mechanisms (CMs). Three distinct linear regions with different slopes were observed in ln(I)–V plots. The first region (R1), is within the range of 0.22–0.60 V, the second region (R2), is within the range of 0.64–0.90 V, and the third region (R3), is within the range of 1.1–1.5 V. It was shown that both ideality factor (n) and zero-bias barrier height (ΦBo) are strong functions of temperature for all three regions. It was noticed that n values decreased and ΦBo values increased with increasing temperature. In order to ascertain the possible CMs, ΦBo − n, − ΦBo − q/2kT, and (n−1 − 1) − q/2kT plots were also examined. In each of these plots, two linear regions were obtained within each of the three regions. The region from 80–180 K is called the low-temperature range (LTR), and the region from 200–360 K is called the high-temperature range (HTR). It has been revealed that the reason for the deviation from the classical thermionic emission (TE) theory cannot be explained only by the existence of the interface layer, interface states (NSS) or quantum mechanical tunneling mechanisms, which can be also explained by the double Gaussian distribution (DGD) due to barrier inhomogeneity. Finally, the experimental Richardson constants (A*) were calculated from the interception point of the modified Richardson curve in LTR and HTR for all three regions. It was calculated as 6.22 and 8.13 A/cm2K2 for RI, 7.77 and 8.14 A/cm2K2 at R2, and 7.07 and 8.13 A/cm2K2 at R3 for low- and high-temperature ranges, respectively. It is clear that especially HTR results are quite close to the known theoretical A* value of 8.16 A/cm2K2 for n-GaAs.

The determination of the temperature and voltage dependence of the main device parameters of Au/7%Gr-doped PVA/n-GaAs-type Schottky Diode (SD)

There are several methods used to obtain the basic diode parameters that affect the diode quality of Schottky diodes (SD) such as ideality factor (n), barrier height (ΦBo), and series resistance (Rs). In this study, it is aimed to compare the results using Ohm’s law, Thermionic Emission theory (TE), Norde and Cheung-Cheung functions. The I–V measurement of the Au/7%Gr-doped PVA/n-GaAs type SD was taken in the range of 80–360 K in 20 K steps. Considering that each method is effective in the different voltage region of the I–V curve and the parameters are strongly voltage-dependent, the results are compatible with each other. Also, the interface states (Nss) were calculated with and without Rs for each temperature value, and it was attained that the effect of Rs reduced Nss values by almost 1 degree. This result reveals the importance of the Rs parameter for SDs. As a result, it is plainly represented that the basic diode parameters n, Rs and ΦBo values are strongly dependent on temperature and voltage, and affected by barrier inhomogeneity and surface states.

Electrical characteristics of organic heterojunction with an alternating benzotriazole and fluorene containing copolymer

The current–voltage ( $$I-V$$ ) and capacitance–voltage ( $$C-V$$ ) characteristics of the organic heterojunction diode were investigated in a wide temperature range from 80 to 320 K and frequency range from 10 kHz to 1 MHz, respectively. Alternative to the copolymer partner poly(3-hexylthiophene) (P3HT) to [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl)2-dodecyl-benzo[1,2,3]triazole)) (named as copolymer in this work) was adapted to the bulk-heterojunction layer in the organic diode. Together with the use of Lif/Al bilayer electrode, the diode was fabricated as in the form of Al/LiF/copolymer:PCBM/PEDOT:PSS/ITO/glass. Under the applied bias voltage, this organic-based diode shows two-orders of magnitude rectifying behavior. According to thermionic emission (TE) model, the diode parameters such as saturation current, barrier height and ideality factor were determined and parasitic resistances were also extracted from the conventional ohmic relation. As to the temperature dependency of the diode parameters and their response to the temperature variation, barrier inhomogeneity, surface state and series resistance effects were found in dominant behavior on the current flow. The conduction mechanism was modeled by assuming low-barrier patches around the main barrier that supports TE at low temperatures and their distribution was expressed by a Gaussian function. In addition, series resistance values were detailed depending on temperature using Cheung’s model. $$C-V$$ analysis was performed to evaluate the distribution of surface states at the interface as a function of frequency. Based on the $$C-V$$ plots, the effects of charges at these traps were observed especially at low frequencies. Additionally, from these results, Fermi level, surface potential and donor concentration values were evaluated in a wide frequency range.

Accelerated Aging Stability of β-Ga2O3-Titanium/Gold Ohmic Interfaces.

Stable ohmic contacts are critical to enable efficient operation of high-voltage electronic devices using ultrawide bandgap semiconductors. Here we perform, for the first time, thermally accelerated aging of Ti/Au ohmic interfaces to (010) β-Ga2O3. We find that a heavily doped semiconductor, doped n-type by Si-ion implantation, treated with reactive ion etch (RIE), results in a low specific contact resistance of ∼10-5 Ω cm2 that is stable upon accelerated thermal aging at 300 °C for 108 h. The low resistance interface is due to thermionic field emission of electrons over an inhomogeneous barrier. Scanning/transmission electron microscopy indicates that the multi-layered structure and elemental distribution across the contact interface, formed during a 1 min 470 °C post-metallization anneal, do not change noticeably over the aging period. A ∼1 nm interfacial layer is observed by high-resolution microscopy at the Ti-TiOx/Ga2O3 interface on all samples exposed to RIE, which may contribute to their excellent stability. In addition, longer-range facet-like interfacial features are observed, which may contribute to the inhomogeneous barrier. In contrast, Ti/Au junctions to moderately doped (010) Ga2O3 made with no RIE treatment exhibit a high contact resistance that increases upon accelerated aging, along with a partially lattice-matched interface. The methods used here to understand the process, structure, and electrical property relationships for Ti/Au contact interfaces to β-Ga2O3 can be applied to assess and tune the stability of a variety of other oxide-semiconductor interfaces.

Temperature dependent Schottky barrier characteristics of Al/n-type Si Schottky barrier diode with Au–Cu phthalocyanine interlayer

The Al/n-type Si Schottky barrier diodes (SBDs) were prepared with Au-Cu phthalocyanine (Au-CuPc) interlayers with different Au and CuPc compositional ratios, probed their temperature dependent current-voltage (I–V) and low frequency noise properties. The Schottky barrier properties like barrier height and the ideality factor are strongly temperature dependent, implying the existence of Schottky barrier inhomogeneities. The barrier inhomogeneities was elucidated using thermionic emission theory based on the assumption of Gaussian distribution of the barrier heights. Further, a divergence in the barrier heights evaluated from the I–V characteristics and Norde's method indicates a deviation of the Al/Au–CuPc/n-type Si SBDs behavior from thermionic emission. The Richardson plot evaluated with the Gaussian distribution of barrier heights method yielded Richardson constant values close to theoretical Richardson constant of n-type Si. The room temperature current noise power spectral density (SI) of the Al/Au–CuPc/n-type Si SBDs having various Au and CuPc concentrations showed a reciprocal of frequency (1/f)γ behavior having γ values near to unity. The decrease in SI and γ with increasing Au concentration in Au-CuPc interlayers was indicative of lessening barrier inhomogeneity. This was also correlated with the decrease in the value of standard deviation derived using temperature dependent I–V characteristics. Further investigations revealed that origins of 1/f noise could be associated with the fluctuations of barrier height and carrier mobility for Al/Au–CuPc/n-type Si SBDs with lower and higher Au compositions in Au-CuPc interlayers, respectively.