A novel technology for fabrication of beam-leaded GaAs Schottky-barrier mixer diodes

The fabrication of mixer diodes for use at millimeter-wave frequencies requires the definition of extremely small area Schottky-barrier junctions. It is not a trivial matter to fabricate such devices at low cost which simultaneously are mechanically rugged, exhibit low parasitics, and present high figures of merit. This paper presents a novel technology for accomplishing these objectives. By incorporating "shadow masked" proton bombardment and metal evaporation, planar beam-leaded devices of low capacitance are realized in the absence of the critical processing steps which have traditionally resulted in low yields. GaAs devices having zero bias capacitance of 0.06 pF are obtained with a series resistance of less than 3 Ω giving a cutoff frequency in excess of 800 GHz. Initial RF tests have resulted in a noise figure and conversion loss of 5.8 and 3.8 dB, respectively, at 10.7 GHz. This technology should result in the availability of inexpensive GaAs mixer diodes suitable for use at millimeter-wave frequencies.     

Measurements on a 215-GHz subharmonically pumped waveguide mixerusing planar back-to-back air-bridge Schottky diodes

This paper presents design and performance data for a 215-GHz subharmonically pumped waveguide mixer using an antiparallel-pair of planar air-bridge-type GaAs Schottky-barrier diodes. The waveguide design is a prototype for a 640-GHz system and uses split-block rectangular waveguide with a 2:1 width-to-height ratio throughout. The measured mixer noise and conversion loss are below that of the best reported whisker contacted or planar-diode mixers using the subharmonic-pump configuration at this frequency. In addition, the required local oscillator power is as low as 3 mW for the unbiased diode pair, and greater than 34 dB of LO noise suppression is observed. Separate sideband calibration, using a Fabry-Perot filter, indicates that the mixer can be tuned for true double sideband response at an intermediate frequency of 1.5 GHz. Microwave scale model measurements of the waveguide mount impedances are combined with a mixer nonlinear analysis computer program to predict the mixer performance as a function of anode diameter, anode finger inductance, and pad-to-pad fringing capacitance. The computed results are in qualitative agreement with measurements, and indicate that careful optimization of all three diode parameters is necessary to significantly improve the mixer performance     

Design and performance of a planar star mixer

This paper describes the realization of a hybrid star mixer as a planar circuit. The mixer has a minimum conversion loss of 5 dB and, for a conversion loss of less than 9 dB, spans over 2.2 GHz in IF bandwidth and 8 GHz in RF/LO bandwidth. The mixer employs a novel, planar balun structure, similar to conductor-backed CPW, that is suitable for realization as a monolithic circuit     

A low-noise fixed-tuned 300-360-GHz sub-harmonic mixer using planar Schottky diodes

This letter presents the design and fabrication of a low-noise fixed-tuned 300-360-GHz sub-harmonic mixer, featuring an anti-parallel pair of planar Schottky diodes fabricated by the University of Virginia and flip-chipped onto a suspended quartz-based microstrip circuit. The mixer exhibits a double side band (DSB) equivalent noise temperature lower than 900K over 18% of bandwidth (300-360-GHz), with 2 to 4.5mW of local oscillator (LO) power. At room temperature, a minimum DSB mixer noise temperature of 700K and conversion losses of 6.3dB are measured at 330GHz.     

Analysis of diodes with a relatively low barrier in the microwave planar mixer

Diodes with a relatively low barrier are investigated in 1D mixer at frequencies of about 94 GHz at a low power of heterodyne. A planar antenna that contains diodes whose differential resistance ranges from 2 to 9 kΩ at zero bias is used for the frequency conversion. The optimal signal output at an intermediate frequency of 700 MHz is reached using transforming circuits that close the diode with respect to direct current and provide the matching of the signal source with an internal resistance of 1 or 2.2 kΩ and a transmission line with an impedance of 50 Ω. The minimum conversion loss (12.5–16 dB) corresponds to the heterodyne power 10–40 μW.     

Compact 28-GHz subharmonically pumped resistive mixer MMIC using a lumped-element high-pass/band-pass balun

This work reports a novel lump-element balun for use in a miniature monolithic subharmonically pumped resistive mixer (SPRM) microwave monolithic integrated circuit. The proposed balun is simply analogous to the traditional Marchand balun. The coupled transmission lines are replaced by lump elements, significantly reducing the size of the balun. This balun requires no complicated three-dimensional electromagnetic simulations, multilayers or suspended substrate techniques; therefore, the design parameters are easily calculated. A 2.4-GHz balun is demonstrated using printed circuit board technology. The measurements show that the outputs of balun with high-pass and band-pass responses, a 1-dB gain balance, and a 5/spl deg/ phase balance from 1.7 to 2.45 GHz. The balun was then applied in the design of a 28-GHz monolithic SPRM. The measured conversion loss of the mixer was less than 11dB at a radio frequency (RF) bandwidth of 27.5-28.5 GHz at a fixed 1 GHz IF, a local oscillator (LO)-RF isolation of over 35 dB, and a 1-dB compression point higher than 9 dBm. The chip area of the mixer is less than 2.0 mm/sup 2/.     

The design and development of a 140GHz beam-lead diode subharmonically pumped mixer

The possibility of using beam-lead diodes in the design of a 140GHz subharmonically pumped mixer was investigated. An easily assembled, rugged mixer structure was developed which avoids the problems associated with present production techniques and reduces costs. The construction of the circuit developed makes it ideally suited to space and other environmentally demanding application. Computer analysis techniques were used to predict millimetre-wave performance and a large-scale low-frequency model was used to optimize the circuit. The millimetre-wave mixer was constructed using a circuit implemented on suspended substrate stripline. Results of millimetre-wave performance are presented.     

An analysis of the photoinduced current from a finely focused light beam in planar p-n junctions and Schottky-barrier diodes

We present analytic expressions for the photocurrent generated by a highly convergent light beam from a microscope objective lens incident on both planar p-n junctions and Schottky-barrier diodes. The variation of the current as a function of surface recombination velocity, depletion region width, diffusion length, and objective lens numerical aperture are all discussed. We also consider the application of the technique as a method of measuring minority-carrier diffusion lengths, which is independent of variations in surface reflectivity.     

High-performance millimetre-wave mixer diodes fabricated using a deep mesa etch approach

Schottky-barrier junction mixer diodes compatible with monolithic integration have been fabricated on semi-insulating GaAs substrates using buried VPE n+ layers and deep mesa etch processing. A 590 GHz cutoff frequency was determined using modified DeLoach analysis and fin-line chip mounting. A 5.3 dB (SSB) noise figure and a 4.8 dB conversion loss were obtained at 35 GHz for a pair of chips in a balanced microstrip mixer.     

A subharmonic mixer using a planar doped barrier diode with symmetric conductance

Planar doped barrier (PDB) diodes with symmetric IV characteristics have been successfully used in a subharmonically-pumped coplanar stripline mixer circuit. A conversion loss around 6 dB has been measured using a 1.2 GHz local oscillator at a pump power of 7 dBm and a 2 GHz signal frequency for large area, 100 µm diameter PDB mesa diodes. The particular advantages of this device structure are that a single PDB replaces two critically matched Schottky barrier diodes in conventionally balanced mixers, and the PDB's designable barrier height reduces the local oscillator power requirement.     

Characteristics of a Schottky-barrier diode mixer with conical horn antenna for submillimeter wavelengths

Antenna characteristics and noise performance of an improved quasi-optical Schottky-barrier diode mixer have been investigated at 800 GHz. We present both calculated and measured antenna patterns. Numerical values are given for the powers radiated in two orthogonal polarizations and for the main beam efficiencies. Measurements indicate that system noise can be reduced by about 25% by adding a conical-horn structure to a corner-cube mixer.     

Current-gain characteristics of Schottky-barrier and p-n junction electron-beam semiconductor diodes

Measured and calculated current gains are presented for silicon, gallium-arsenide, and gallium-arsenide-phosphide electron-beam-semiconductor Schottky-barrier diodes. Silicon and gallium-arsenide-phosphide (GaAs0.7P0.3) diodes, having comparable critical voltages, provided current gains of 1400 and 960, respectively, at the beam voltage of 9 kV. A gallium-arsenide diode had a gain of 2100 at 12.7 kV. It is shown that Schottky-barrier diodes provide a good diagnostic tool for measurement of energy per electron-hole pair in semiconductors. The average pair energies for silicon, gallium arsenide, and gallium arsenide phosphide, determined by use of these diodes, were 3.6, 4.6, and 5.2 eV, respectively. Expressions for static and time-dependent current gains are derived for abrupt p-n-junction EBS diodes based on measured and simplified (constant) lineal densities of secondary-electron generation. It is shown that the current gain of p-n junctions is generally lower than that of Schottky-barrier diodes and decreases with increasing density of the semiconductor. For shallow (<0.2 µmr) silicon junctions, the calculated current gain is only slightly smalle. (<8 percent) than that of comparable Schottky-barrier diodes Measurements performed on a relatively deep (0.8 µm) silicon p-n junction, which provided a current gain of 2500 at the beam voltage of 13.6 kV, are in good agreement with the theory. The gain of this junction was typically 40 percent lower than that of a comparable Schottky-barrier diode. This difference was significantly greater for gallium arsenide as a result of its higher density. Approximate expressions and calculations are presented for estimating frequency limitations of p-n-junction EBS targets.     

Dynamic strain-sensitive characteristics of the Schottky-barrier diodes under a pulsed uniform pressure

Dynamic strain-gage characteristics of Schottky-barrier diodes of the Au-Si:Ni-Sb type subjected to pulsed uniform pressure in the range of P=(0?5)×10⁸ Pa at a temperature of T=300 K were studied. Studies of I-V characteristics of the diodes showed that, due to an additional temperature effect induced by the pulsed pressure, the dynamic parameters of the stress-sensitivity effect in these diodes were 20–30% larger than the corresponding static parameters.     

Relationship between junction radius and reverse leakage of silicide Schottky-barrier diodes

Unguarded Schottky-barrier diodes exhibit excessive leakage current in the reverse-current direction. A portion of this excess current has always been attributed to sharp-edge effects. In this paper, the sharp-edge-related excess reverse current is attributed to the additional barrier lowering that is due to the electric-field enhancement present near the diode edges. Mathematical relationships describing the effect of the edge radius on the I-V characteristics of unguarded diodes are developed. These relationships are then used to model an unguarded Schottky-barrier diode. The correlation between the junction radius and the diode characteristics was found to be strong in the reverse-current direction. In the foward direction, the diode characteristics were not greatly affected, and thus the large diode-quality factors of unguarded diodes cannot be attributed to the sharp-edge effect. A comparison is made between the experimental characteristics of Pd2Si/ nSi and VSi2/nSi diodes and those obtained from modeling.     

Design of novel balanced high-order subharmonic self-oscillating mixer

The design of RF and millimetre-wave receivers demands low-cost features and compact architecture. Self-oscillating mixers (SOMs) are excellent choices for such a design as both the oscillating source and the mixer are combined in one single device. Moreover, subharmonic operation reduces LO frequency requirements and therefore opens up interesting perspectives for high-end millimetre-wave systems. A fully-balanced third-harmonic SOM structure is presented, operating at 5.8 GHz with high measured conversion gain (max. 8.75 dB) that is used as a frequency-scaled prototype for future millimetre-wave circuits. To the authors' knowledge, this is the first presentation of such a circuit structure     

Gain and power parameter measurements using planar near-fieldtechniques

Equations are derived and measurement techniques described for obtaining gain, effective radiated power, and saturating flux density using planar near-field measurements. These are compared with conventional far-field techniques, and a number of parallels are evident. These give insight to the theory and help to identify the critical measurement parameters. Application of the techniques to the Intelsat VI satellite is described     

Design and performance of a noncontacting probe for measurements onhigh-frequency planar circuits

Optimal design of a noncontacting magnetic probe for measurements on the interior of planar high-frequency circuits has been studied, and performance of the probe has been determined. The design was studied using enlarged models tested at frequencies 100 times lower than those of the actual intended use. The nature of its errors has been investigated, and some techniques for error reduction have been found. The accuracy of measurements on circuits with SWR <3.0 is typically 0.8 dB in magnitude and 7° in phase. S-parameter measurements on general two-ports can also be made by using the probe at several different positions on the associated transmission lines. The technique effectively eliminates the problem of de-embedding that arises in other kinds of S-parameter measurements. Examples of measurements with the large model probe are presented and compared with theory. Performance appears to be acceptable for the intended applications     

Efficiencies of Schottky-barrier GaAs and both complementary structures of Si IMPATT diodes

Computer simulation results show that optimum dc to RF conversion efficiency is in descending order for Schottky-barrier GaAs, p⁺-n Si, and n⁺-p Si IMPATT diodes.     

Design and simulation of a nanoelectronic single electron 2-4 decoder using a novel simulator

The design and simulation of a single-electron 2-4 decoder using a novel single electron circuit simulation tool named single-electron circuit simulator (SECS), is presented in this paper. In single electron circuits bits of information are represented by the presence or absence of single electrons at conducting or semiconducting islands. SECS utilizes the Monte Carlo method and the change in free-energy of the whole circuit determines the tunnel rates of possible tunnel events, providing thus a real time simulation of any arbitrary single-electron circuit. Furthermore, SECS is using the SPICE interface for schematic capture. SPICE models of single-electron circuit structures have been developed and, therefore, SECS can also be used for the design and simulation of hybrid microelectronic—single-electron circuits.