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Silicon carbide (SiC) unipolar devices have much higher breakdown voltages than silicon (Si) unipolar devices because of the ten times greater electric field strength of SiC compared with Si. 4H-SiC unipolar devices have higher switching speeds due to the higher bulk mobility of 4H-SiC compared to other polytypes. In this paper, four commercially available SiC Schottky diodes with different voltage and current ratings, VJFET, and MOSFET samples have been tested to characterize their performance at different temperatures ranging from -50°C to 175°C. Their forward characteristics and switching characteristics in this temperature range are presented. The characteristics of the SiC Schottky diodes are compared with those of a Si pn diode with comparable ratings.

We report the first experimental results for noise-equivalent power (NEP) and noise-equivalent temperature difference (NETD) of single-crystal ErAs:InAlGaAs, zero-bias rectifier diodes coupled to free space quasi-optically in the THz region. At a frequency of 639 GHz, an optical NEP of 4.0×10⁻¹²W/Hz^1/2 is measured with the rectifier coupled to a quasi-plane-wave coherent source through a single-turn square spiral antenna. With a broadband thermal (hot water) source, an NETD of 120 mK is measured from the same device. Antenna radiation patterns at 100 GHz and 639 GHz are also presented.

The feasibility of CMOS circuits operating at frequencies in the upper millimeter wave and low sub-millimeter frequency regions has been demonstrated. A 140-GHz fundamental mode VCO in 90-nm CMOS, a 410-GHz push-push VCO in 45-nm CMOS, and a 180-GHz detector circuit in 130-nm CMOS have been demonstrated. With the continued scaling of MOS transistors, 1-THz CMOS circuits will be possible. Though these results are significant, output power of signal generators must be increased and acceptable noise performance of detectors must be achieved in order to demonstrate the applicability of CMOS for implementing practical terahertz systems.

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.

Gallium nitride (GaN) is a highly promising wide band gap semiconductor with applications in high power electronic and optoelectronic devices. Thin films of GaN are most commonly grown in the hexagonal wurtzite structure on sapphire substrates. Growth of GaN onto silicon substrates offers a very attractive opportunity to incorporate GaN devices onto silicon-based integrated circuits. Although direct epitaxial growth of GaN films on Si substrates is a difficult task (mainly due to the 17% lattice mismatch present), substantial progress in the crystal quality can be achieved using a buffer layer. A full characterization of the quality of the material needs to be assessed by a combination of different techniques.

In this work, a thin AlN cap layer of 50 nm was incorporated in GaN Schottky diode to enhance the effective Schottky barrier height and reduces the dark current. A barrier height of 0.52 eV for normal GaN Schottky diode was increased to the effective barrier height of 0.63 eV. The resulting Schottky diodes show a dark current of as low as 6.3×10^-5 A at 5 V bias, which is about two orders of magnitude lower than that of normal GaN (5.2×10^-3 A at 5 V bias) Schottky diode.

We present the results of cumulant analysis for detection of random process using a Schottky diode with δ-doping. The statistical characteristics of the output process of the detector, based on a Schottky diode with δ-doping, are investigated. We discuss noninertial and inertial detection mode. It was shown that at a relatively large dispersion of the input noise a noninertial detection mode occurs.

A carbon nanotube (CNT) Schottky diode based on coaxial geometry is presented. We show that coaxially gated CNT field effect transistors (FETs) with a p-type semiconducting single-walled carbon nanotube (s-SWNT) and asymmetric contacts can provide good diode characteristics. The effect of different physical and electrical parameters such as gate bias voltage, gate insulator thickness, and CNT diameter on the rectification current–voltage characteristics is investigated. We demonstrate that it is possible to tune the rectification characteristic, threshold voltage, reverse saturation current, and reverse turn-on voltage by using these parameters.

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.

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.

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.

We fabricated 25 Au/$n$-GaP/Al Schottky devices and investigated the influence of high electron irradiation, which has 12MeV on the devices, at room temperature. The X-ray diffraction patterns, scanning electron microscopic images and Raman spectra of a gallium phosphide (GaP) semiconductor before and after electron irradiation have been analyzed. Furthermore, some electrical measurements of the devices were carried out through the current–voltage ($I$–$V$) and capacitance–voltage ($C$–$V$) measurements. From the $I$–$V$ characteristics, experimental ideality factor $n$ and barrier height $\mathrm{\Phi }$ values of these Schottky diodes have been determined before and after irradiation, respectively. The results have also been analyzed statically, and a gauss distribution has been obtained. The built-in potential $V_{\mathrm{\text{bi}}}$, barrier height $\mathrm{\Phi }$, Fermi level $E_F$ and donor concentration $N_d$ values have been determined from the reverse bias $C$–$V$ and $C^{-2}-V$ curves of Au/$n$-GaP/Al Schottky barrier diodes at 100kHz before and after 12MeV electron irradiation. Furthermore, we obtained the series resistance values of Au/$n$-GaP/Al Schottky barrier diodes with the help of different methods. Experimental results confirmed that the electrical characterization of the device changed with the electron irradiation.

Au/n-Si (MS) and Au/Poly (linolenic acid)-g-poly (caprolactone)-g-poly (t-butyl acrylate) (PLilPCLPtBA)/n-Si (MPS) diodes were fabricated to investigate the electrical and responsivity effects of interfacial layer on the diodes under ultra violet (UV) illumination. Electrospinning method was used for coating of the PLilPCLPtBA polymer layer on n-Si single crystal as nanofibers. Surface formation and nanofiber characteristics of the polymer layer were investigated by an electron microscope. The current-voltage ($I\text{–}V$) measurements of the MS and MPS diodes were carried out in dark and under UV (365 nm) illumination conditions at room temperature. Basic electrical parameters of the diodes; such as reverse bias saturation current ($I_0$), zero bias barrier height $({\mathrm{\Phi }}_{B0})$, ideality factor ($n$), series resistance ($R_s$) and interface state density ($N_{\mathrm{\text{ss}}}$) were extracted from the experimental $I\text{–}V$ measurements by thermionic emission and Norde equations. Also, power law of the photocurrents ($I_{\text{pc}}$) and responsivity ($R$) behavior were obtained and given comparatively.

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.

Fluctuations of Schottky diode parameters in a structure of the mixer are investigated. We have used our original measurement data of $1/f$ noise in the diode at forward current, which were reported somewhat earlier. These fluctuations are manifested in two ways. At the first, they lead to fluctuations in the transfer factor that is lead to the amplitude fluctuations in the signal at intermediate frequency. The estimation of spectrum of relative fluctuations in the transfer factor of the mixer is executed. Dependences of both the spectrum of these fluctuations on the current through the diode and on the amplitude of the heterodyne signal are investigated. At the second, fluctuations in parameters of the diode lead to occurrence of $1/f$ noise in the output voltage. This noise limits the sensitivity of the mixer to the received signal.

Ordered ZnO arrays with a peculiar nanostructure were synthesized by a multistep synthesis process. The first step was the preparation of ZnO seed to induce the formation of ZnO array via potentiostatic electrodeposition method using a typical three electrode set-up. The second step was fabricating ZnO array along seed by Chemical Bath Deposition. Structural analysis of ZnO was carried out with X-ray diffraction (XRD), which showed a hexagonal wurtzite structure, and the selected area electron diffraction (SAED) patterns indicated that nanocrystalline is a part of monocrystal. The scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to study the microstructure, and showed a pagoda-like microstructure with a tiny top and large bottom, which had an average top diameter of exceeding 800nm at seed-depositing time of 60s, and then growth mechanisms are subsequently given a further explanation, viewed from kinetics and thermodynamics. In addition, the current–voltage curves of schottky diode devices with ZnO nanopagoda arrays revealed that ZnO films arrays along grown ZnO seed had a higher reverse saturation current than ZnO films grown without seed, which are $1.48\times 10^{-6}$ A and $1.32\times 10^{-8}$ A, respectively. The minimum turn-on voltage of the diode with ZnO seed deposited 60s is 0.18V, without seed is 0.52V.

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.

We report the first experimental results for noise-equivalent power (NEP) and noise-equivalent temperature difference (NETD) of single-crystal ErAs:InAlGaAs, zero-bias rectifier diodes coupled to free space quasi-optically in the THz region. At a frequency of 639 GHz, an optical NEP of 4.0×10⁻¹²W/Hz^1/2 is measured with the rectifier coupled to a quasi-plane-wave coherent source through a single-turn square spiral antenna. With a broadband thermal (hot water) source, an NETD of 120 mK is measured from the same device. Antenna radiation patterns at 100 GHz and 639 GHz are also presented.

Silicon carbide (SiC) unipolar devices have much higher breakdown voltages than silicon (Si) unipolar devices because of the ten times greater electric field strength of SiC compared with Si. 4H-SiC unipolar devices have higher switching speeds due to the higher bulk mobility of 4H-SiC compared to other polytypes. In this paper, four commercially available SiC Schottky diodes with different voltage and current ratings, VJFET, and MOSFET samples have been tested to characterize their performance at different temperatures ranging from -50°C to 175°C. Their forward characteristics and switching characteristics in this temperature range are presented. The characteristics of the SiC Schottky diodes are compared with those of a Si pn diode with comparable ratings.