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Zr/p-Si Schottky diode was fabricated by DC magnetic sputtering of Zr on p-Si. Zr rectifying contact gave a zero bias barrier height of 0.73 eV and an ideality factor of 1.33 by current–voltage measurement. The experimental zero bias barrier height was higher than the value predicted by metal-induced gap states (MIGSs) and electronegativity theory. The forward bias current was limited by high series resistance. The series resistance value of 9840 $\mathrm{\Omega }$ was determined from Cheung functions. High value of the series resistance was ascribed to low quality ohmic contact. In addition to Cheung functions, important contact parameters such as barrier height and series resistance were calculated by using modified Norde method. Re-evaluation of modified Norde functions was realized in the direction of the method proposed by Lien et al. [IEEE Trans. Electron Devices 31 (1984) 1502]. From the method, the series resistance and ideality factor values were found to be as 41.49 $\mathrm{\Omega }$ and 2.08, respectively. The capacitance–voltage characteristics of the diode were measured as a function of frequency. For a wide range of applied frequency, the contact parameters calculated from $C^{-2}$–$V$ curves did not exhibit frequency dependence. The barrier height value of 0.71 eV which was in close agreement with the value of zero bias barrier height was calculated from $C^{-2}$–$V$ plot at 1 MHz. The values of acceptor concentration obtained from $C^{-2}$–$V$ curves showed consistency with actual acceptor concentration of p-Si.

Power semiconductor devices are important for numerous applications with power conversion being an important one. Wide energy gap semiconductors SiC and GaN have properties that make them attractive for such applications. Among these properties are high thermal conductivity, high breakdown electric field, wide energy gap, low intrinsic carrier concentration, high thermal stability, high saturation velocity and chemical inertness. These lead to low on-resistance, high breakdown voltage, high frequencies, small volume, and small passive inductors and capacitors. These desirable properties are offset by the higher material costs and higher defect densities. Although wide energy gap devices have been in development for many years, only recently have they become available commercially. Their main competition is silicon power devices with breakdown voltages up to 8000 V and very high surge current capacity. However, silicon power devices are approaching their material limits and wide energy gap devices are beginning to have an impact in the power electronics space. SiC has the advantage of substrates with diameters approaching 150 mm and the ability to grow thermal SiO₂. GaN has the heterojunction advantage, but no viable substrate technology. In fact, a large portion of SiC production is used for GaN substrates. GaN material development has also benefited significantly from the development of optical devices, e.g., light-emitting diodes and lasers.

The lifetime of battery-operated sensor platforms (i.e., sensor nodes) is a critical issue. The replacement of their batteries is quite a challenging task if these platforms are deployed for detecting events in inaccessible geographical areas (e.g., forest). This paper describes an optimized RF energy harvester/scavenger (consisting of an antenna, impedance matching circuit and rectifier) for energizing low-power sensor platforms (electronic systems). Few nonmatched rectifiers (using HSMS-285X Schottky diodes) are fabricated to characterize the input impedance for different sets of parameters. After characterization a proper impedance matching circuit is integrated for the maximum power transfer from antenna to rectifier. It is shown that a single stage of RF rectifier is enough to produce output voltage of 1.8V. Very few realizations of RF energy harvester are reported in the literature under 2.4GHz ISM band category. Furthermore, high-gain microstrip patch array antennas are fabricated to capture the maximum power from the surroundings. The maximum harvesting range of 0.92m is obtained at 27dBm transmitting power level.

We have fabricated the Ti/$n$-type GaAs Schottky diodes (SDs) by the DC magnetron deposition and thermal evaporation, cut from the same GaAs substrates, and we have made a comparative study of the current–voltage ($I$–$V$) measurements of both SDs in the measurement temperature range of 160–300K with steps of 10K. The barrier height (BH) values of about 0.82 and 0.76eV at 300K have been obtained for the sputtered and evaporated SDs, respectively. It has been seen that the apparent BH value for the diodes has decreased with decreasing temperature obeying the single-Gaussian distribution (GD) for the evaporated diode and the double-GD for the sputtered diode over the whole measurement temperature range. The increment in BH and observed discrepancies in the sputtered diode have been attributed to the reduction in the native oxide layer present on the substrate surface by the high energy of the sputtered atoms and to sputtering-induced defects present in the near-surface region. We conclude that the thermal evaporation technique yields better quality Schottky contacts for use in electronic devices compared to the DC magnetron deposition technique.

In this work, we report theoretical and experimental study of Pd/ZnO nanorod (NR) Schottky diodes-based ultraviolet photodetector (UV-PD). The ZnO-NRs are deposited on indium tin oxide (ITO) coated glass substrates by using a low-temperature hydrothermal method. The surface morphology of the ZnO-NRs film is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SEM image shows vertically grown NRs with uniformity, and XRD shows the preferred (002) orientation of ZnO-NR films. The current–voltage characteristics of Pd/ZnO-NR Schottky diodes are studied under dark and UV light. A voltage bias from $-$1V to $+$1V is applied and the ratio of photocurrent to dark current was ($\sim 0.17\times 10^2$ at $V=0.5$V) calculated from the $I$–$V$ curve. The value of responsivity was found to be 0.111A/W at $\lambda =365$nm and at $\mathrm{\text{bias}}=0.50$V. An approximated UV-PD structure has also been numerically simulated using three-dimensional (3D) device simulator from Visual TCAD of Cogenda International. The simulated $I$–$V$ characteristics have also been plotted under both dark and light conditions. The simulated results are found to be following the nature of experimental results.

Having long been the realm of molecular chemistry, astronomy, and plasma diagnostics, the upper millimeter-wave band (∼100 to 300 GHz) and the THz region above it have recently become the subject of heightened activity in the engineering community because of exciting new technology (e.g., sub-picosecond optoelectronics) and promising new “terrestrial” applications (e.g., counter-terrorism and medical imaging). The most challenging of these applications are arguably those that demand remote sensing at a stand-off of roughly 10 m or more between the target and the sensor system. As in any other spectral region, remote sensing in the THz region brings up the complex issues of sensor modality and architecture, free-space electromagnetic effects and components, transmit and receive electronics, signal processing, and atmospheric propagation. Unlike other spectral regions, there is not much literature that addresses these issues from a conceptual or system-engineering viewpoint. So a key theme of this chapter is to review or derive the essential engineering concepts in a comprehensive fashion, starting with fundamental principles of electromagnetics, quantum mechanics, and signal processing, and building up to trade-off formulations using system-level metrics such as noiseequivalent power and receiver operating characteristics. A secondary theme is to elucidate aspects of the THz region and its incumbent technology that are unique, whether advantageous or disadvantageous, relative to other spectral regions. The end goal is to provide a useful tutorial for graduate students or practicing engineers considering the upper mm-wave or THz regions for system research or development.

We have fabricated SnO₂/p-Si and SnO₂/p-PoSi heterojunction diodes by spray pyrolysis method. To prepare porous Si substrates, the etching time was varied from 10 to 20 and 30 mins. In these samples, the SEM micrographs showed a distributed pore areas surrounded by columnar walls with various height. The data analysis of the rectified I–V characteristic, using thermionic emission Schottky diode theory, showed that although the barrier height is about 0.5–0.6 eV in all samples other two important diode parameters, i.e. the ideality factor n and the series resistance r_s, are strongly etching time-dependant and are increased with increasing the etching time.

A model of Schottky diode with δ-doping is suggested. The aim is the determination of technological areas of the diode, which are responsible for the 1/f noise. Series resistance of base and contacts, and the possible leakage are taken into account. Equivalent parameters of the diode are defined from the analysis of the current–voltage characteristic. The model of fluctuations in the charge of non-compensated donors in δ-layer of Schottky junction (ΔN_s – model) and model of 1/f noise in leakage current are suggested for an explanation of experimental data. Our study show that, in the investigated diodes, in a million atomic impurities, there are about 1–10 special impurity atoms with stochastically modulated ionization energy.

We have studied the forward current–voltage (I–V) characteristics of Ti–Au/n-type GaAs Schottky barrier diodes. However, we found some anomalies in I–V characteristics. Hence, we have considered a model that incorporates thermionic emission, thermionic-field emission and leakage components. Leakage component is linear and visible at rather small currents. The anomalies observed in the diode parameters were effectively construed in terms of the contribution of these multiple charge transport mechanisms across the interface of the diodes. It is shown that thermionic-field emission and leakage are the sources of low-frequency (1/f) noise in such type of diodes. Various Schottky diode parameters were also extracted from the I–V characteristics and current dependence of spectrum of 1/f voltage noise.

Power semiconductor devices are important for numerous applications with power conversion being an important one. Wide energy gap semiconductors SiC and GaN have properties that make them attractive for such applications. Among these properties are high thermal conductivity, high breakdown electric field, wide energy gap, low intrinsic carrier concentration, high thermal stability, high saturation velocity and chemical inertness. These lead to low on-resistance, high breakdown voltage, high frequencies, small volume, and small passive inductors and capacitors. These desirable properties are offset by the higher material costs and higher defect densities. Although wide energy gap devices have been in development for many years, only recently have they become available commercially. Their main competition is silicon power devices with breakdown voltages up to 8000 V and very high surge current capacity. However, silicon power devices are approaching their material limits and wide energy gap devices are beginning to have an impact in the power electronics space. SiC has the advantage of substrates with diameters approaching 150 mm and the ability to grow thermal SiO₂. GaN has the heterojunction advantage, but no viable substrate technology. In fact, a large portion of SiC production is used for GaN substrates. GaN material development has also benefited significantly from the development of optical devices, e.g., light-emitting diodes and lasers.