Single Schottky Diode Research Articles

A Self-Matching Rectifier Based on an Artificial Transmission Line for Enhanced Dynamic Range

In this paper, self-matching rectifiers for enhanced input dynamic range are demonstrated. The method is based on an artificial transmission line, which consists of a stepped-impedance transmission line loaded with shunt varactors. The output DC voltage of the rectifier is fed back to the varactors to control the effective electrical length and characteristic impedance of the line. Because this bias voltage changes as the power input to the rectifier changes, a matching network that maintains impedance matching regardless of the input power can be developed without additional circuits, thus substantially improving the input dynamic range. The experimental results for prototype rectifiers show a dynamic range as wide as 25 dB with only a single Schottky diode, an improvement of 11 dB over the rectifier with a conventional matching scheme, in which the conversion efficiency remains above 50%. The effectiveness of the proposed method is also verified with the experimental results for rectennas based on the demonstrated rectifiers.

Wideband Predistortion Technique With Dual-Parallel Schottky Diodes for Low Power RoF Systems

Radio-over-fiber (RoF)-based front haul architecture has attracted considerable attention for fifth-generation (5G) cellular systems because of its cost effectiveness, however, it is susceptible to harmonic frequency distortion and intermodulation products (IMs) arising from the nonlinearity of the laser diode. To overcome this limitation, an asymmetric electrical predistortion method, using a single Schottky diode with nonlinear characteristics similar to those of a laser diode, was previously proposed. However, its asymmetric structure causes a phase mismatch, which limits the system bandwidth. In this study, we propose an enhanced electrical predistortion technique using dual-parallel Schottky diode blocks. The proposed technique was validated by experiments involving an IM3 drop of approximately 27 dB, and by using identical dual Schottky diode blocks, the phase mismatch in the previously proposed method is completely eliminated. Thus, the applicable bandwidth is extended to 1.8 GHz. This technique can be used to improve the linearity and increase the bandwidth of RoF systems. Additionally, the simple structure is attractive for low-power applications.

Design and Development of High Efficiency Rectenna for RF Harvesting

In this paper, we propose a compact and highly efficient Rectenna design (rectifying antenna), operating on ISM band with the center frequency of 2.4 GHz. A RF to DC conversion through Schottky diode (HSMS2860) is used to generate the dc voltage to operate a battery-less Sensor for RF power harvesting using the designed Rectenna. We have achieved more than 80% efficiency through Advanced Design System (ADS-2016) simulation software at different power densities. Further a rectenna circuit is designed using RF to DC Schottky detector diode and a microstrip patch antenna. The rectenna circuit design is simulated through ADS 2016 simulation software. The Battery less sensor requires 1.8V- 2.5V dc voltage to perform an optimum performance. As per simulation and theoretical/practical modeling we have achieved more than 80% efficiency at single Schottky diode and its operating from 915 MHz to 5.8 GHz. Rectenna operates at lower power densities start from 0.4uW/cm. The proposed rectenna design is a possible candidate to be used for mobile/sensor application without Battery

Characteristics of the Schottky barriers of two-terminal thin-film Al/nano-Si film/ITO structures

The temperature dependence of the Schottky-barrier height and series resistance of two-terminal thin-film Al/nano-Si film/ITO structures are determined from the current—voltage (I–V) characteristics in the temperature range of 20–150°C. It is found that the form of the I–V characteristic at all investigated temperatures can be described by a model of two Schottky diodes connected back-to-back. For these diodes, the general formula is obtained, which allows the construction of functions approximating experimental curves with high accuracy. Based on this formula, a computational model is built, which generalizes the theoretical data obtained by S.K. Cheung and N.W. Cheung widely used for analyzing the I–V characteristics of single Schottky diodes. A technique is developed for calculating the Schottky-barrier heights in a system of two Schottky diodes connected back-to-back, their ideality factors, and the series resistance of the system. It is established that the barrier heights in the investigated temperature range are ~1 eV. According to the temperature dependence of the barrier height, such large values result from the presence of a SiO x (0 ≤ x ≤ 2) oxide layer at the nanoparticle boundaries. Charge carriers can overcome this layer by means of thermal excitation or tunneling. It is established that the intrinsic Schottky-barrier height of the Al/nc-Si film and nc-Si film/ITO junctions is ~0.1 eV. The activation dependences of the series resistance of the Al/nc-Si film/ITO structures and impedance spectra show that combined electric-charge transport related to ionic and electronic conductivity takes place in the structures under study. It is shown that the contribution of the electronic conductivity to the total transport process increases as the sample temperature is raised.

Back‐to‐back connected asymmetric Schottky diodes with series resistance as a single diode

We have studied current–voltage characteristics of two back‐to‐back connected Schottky diodes. In many semiconductor devices, we need to prepare one Schottky contact and the second contact should be ohmic. We show that even in the case when the second contact is also of Schottky type but with different barrier height, current–voltage characteristic remains very similar as that of single Schottky diode. The existence of the second Schottky diode with lower‐barrier height may not be detectable by inspecting I–V curves of such structure. The analysis and Schottky diode parameter extraction also may not be able to disclose existence of two Schottky contacts in the studied structure. The structure behaves as it would be one single Schottky contact. This knowledge may be used in technology where in many cases the ohmic contact may be substituted by another Schottky contact with lower‐barrier height.

Optical modulation of continuous terahertz waves towards cost-effective reconfigurable quasi-optical terahertz components

We report optical modulation of continuous terahertz (THz) wave in the frequency range of 570-600 GHz using photo-induced reconfigurable patterns on a silicon wafer. The patterns were implemented using programmable illumination from a commercially-available digital light processing (DLP) projector. A modulation depth of 20 dB at 585 GHz has been demonstrated. Modulation speed measurement shows a 3-dB bandwidth of ~1.3 kHz which is primarily limited by the DLP system. A photo-induced polarizer with tunable polarization angle has been demonstrated, showing a 3-dB extinction ratio. Reconfigurable aperture-arrays (4 x 4 pixels) have been attempted for room-temperature coded-aperture imaging using a single Schottky diode detector at 585 GHz. We envision that this technique will provide a simple but powerful means to realize a variety of cost-effective reconfigurable quasi-optical THz circuits and components.

Transport properties in C60 field-effect transistor with a single Schottky barrier

C 60 field-effect transistor (FET) has been fabricated with a single Schottky barrier formed by an insertion of 1-dodecanethiol at the interface between the active layer and the gate dielectric. The suppression of drain current is observed at low drain-source voltage, showing a formation of the carrier injection barrier. Furthermore, a clear difference between forward and reverse drain currents is observed in the FET in a high temperature region, showing that this FET device is close to an ideal single Schottky diode. The quantitative analysis for carrier injection barrier has been achieved with thermionic emission model for a single Schottky barrier.

On the effect of IF power nulls in Schottky diode harmonic mixers

Experimental results reveal the existence of a null in the IF output power for certain bias voltage levels in single Schottky diode harmonic mixers at terahertz frequencies. This dramatic loss of IF power is due to a drastic increase of conversion loss and is governed by intrinsic diode parameters, as well as external parameters. For a second harmonic mixer, this is due to a competition of two mixing paths; one is the mixing of the RF with the doubled local oscillator (LO) frequency and the other a mixing of the RF with the LO to an LO sideband followed by a second mixing with the LO, both leading to the IF. In this paper, we present a systematic investigation of and some basic relations between these parameters and the depth and voltage levels where the conversion loss increases. Good agreement is obtained between a simple analysis and the experimental data on second and fourth harmonic mixers.

Effects of barrier height distribution on the behavior of a Schottky diode

The current–voltage characteristics of a Schottky diode are simulated numerically using the thermionic emission-diffusion mechanism and considering a Gaussian distribution of barrier heights, with a linear bias dependence of both the mean and standard deviation. The resulting data are analyzed to get insight into the effects of distribution parameters on the barrier height, activation energy plots and the ideality factor over a temperature range 50–300 K. It is shown that with a Gaussian distribution of the barrier heights the system continues to behave like a single Schottky diode of apparently low zero-bias barrier height and a high ideality factor. Its barrier height decreases, activation energy plot becomes non-linear and ideality factor increases with a decrease in temperature. While the distribution parameters are responsible for the abnormal decrease of barrier height, their bias dependences account for the higher ideality factor at low temperatures. Also, the pivotal role played by series resistance in influencing the linearity of the ln(I)–V plots of Schottky diodes with a Gaussian distribution of barrier heights is discussed.

Development of a low-cost 35 GHz radar sensor

Two different 35 GHz low-cost rf front-end Doppler units suited for automotive applications have been constructed. The homodyne unit consists of both receiving and transmitting corporate-fed microstrip patch array antennas, a microstrip directional coupler, a monolithic GaAs fected oscillator and an integrated single Schottky diode mixer. The autodyne configuration uses only one antenna and the fected as a self-oscillating mixer. Inexpensive microstrip technology has been used which yields a good compromise between cost factor and technical performance.

Characteristics of Schottky diodes with microcluster interface

We present experimental evidence that a single Schottky diode on GaAs is an agglomorate of paralleled microjunctions with different barrier heights and saturation currents. The current-voltage characteristic of the cluster breaks up into sections of exponentials with different slopes as one cools the diode from 300 to 10 K. Noise measurements performed on cooled diodes at 4 GHz also confirm that a single device is a cluster of paralleled diodes.

A 230-GHz Radiometer System Employing a Second-Harmonic Mixer (Short Papers)

A radiometer system for use in the lambda ~ 1.3 mm (v ~ 230 GHz) region has been constructed and used for radio astronomical observations. A second-harmonic mixer employing a single Schottky diode downconverts the incident power to an IF frequency of -1400 MHz. The measured double-sideband system noise temperature is 6000 K (noise figure = 13 dB) and the double-sideband mixer conversion loss is calculated to be 10 dB. The mixer is tunable over a range of at least 15 GHz.