Millimeter-wave point-contact and junction diodes

Millimeter-wave "point-contact" diodes are classed as conventional point-contact diodes (and modifications on them), which depend primarily upon a point-contact metal-semiconductor junction for their rectification properties; or as junction diodes with point-contact geometry, which are small-area millimeter-wave adaptations of the p-n junction diodes, normally made for use at lower frequencies by alloying, diffusion and other techniques. In a general way, techniques used in the fabrication of these various diodes are described; then the uses to which they have been put is detailed, and the best reported performance characteristics in various millimeter-wave applications are compared. Emphasis is put on demonstrated performance, but highly experimental and tentative laboratory results are freely quoted. Included are discussions of 1) conventional point-contact diodes of various semiconductors; 2) diodes having point-contact geometry but exhibiting electrical properties approximating those of alloyed and diffused p-n junctions, diodes made by planar techniques, a "thermoelectric effect hot carrier" diode, point-contact photodetectors and photoemitters; and 3) a millimeter-wave avalanche transit-time oscillator diode. The use of these diodes as millimeter-wave detectors, amplifiers, oscillators, harmonic generators, and modulators is considered.     

High field emission in germanium point-contact diodes

The effects have been examined of small changes of barrier height on the reverse current of high inverse voltage germanium point-contact diodes. The barrier height was varied by changing the ambient gas. The experimental results are given quantitative interpretation by a field emission theory in the region from about 10 volts to about 150 volts, where other effects become important. Examination of some 50 diodes has shown that diodes which draw low reverse currents behave according to this theory.     

Local doping of silicon by a point-contact microwave applicator

The feasibility of local doping in silicon by an open-end coaxial applicator with a tip made of the doping material, e.g. aluminum or silver, is studied in this paper. In these experiments, localized microwave power of 100-350 W at 2.45 GHz was applied for ∼1 min to obtain doped regions of ∼1-mm width and ∼0.3-μm depth. Independent measurements of secondary ion mass spectroscopy (SIMS) and junction built-in potential measured by atomic-force microscopy (AFM) were used to estimate the activated doping concentrations in the order of 10¹⁹ and 10²² cm⁻³ for aluminum and silver doping, respectively. Potential barriers (pn junctions) of 0.5-0.7 V were measured across the aluminum-doped regions, and I-V characteristics were observed. The doping experiments were conducted in air atmosphere, hence oxidation effects were observed as well. The localized-microwave doping concept presented here could be useful in small-scale semiconductor processes, integrated optics, and MEMS applications.     

High-temperature point-contact transistors and Schottky diodes formed on synthetic boron-doped diamond

Point-contact transistors and Schottky diodes have been formed on synthetic boron-doped diamond. This is the first report of diamond transistors that have power gain. Further, the transistors exhibited power gain at 510°C and the Schottky diodes were operational at 700°C.     

Characteristics of metal-insulator-metal point-contact diodes used for two-laser mixing and direct frequency measurements

The frequency response characteristics of metal-insulator-metal (MIM) diodes used for direct-frequency measurements in the submillimeter and infrared spectral region have been determined and it is found that these may be described by a simple model based on aerial impedance and barrier shunt capacitance. In addition, an MIM diode has been used to detect visible radiation from an argon ion laser.     

Thermal design of microwave PIN diodes

Design of microwave PIN diodes suitable for phased array antennas is considered from the point of view of specific power handling capability. Analysis of the thermal parameters of the diode by previous authors is briefly reviewed. Outline of a complete design procedure is given from the point of view of thermal management and microwave performance. Computed values of design parameters are given.     

Capacitance-voltage characteristics of microwave Schottky diodes

Based on an analytical solution of Poisson's equation, the authors calculate/capacitances of metal circular dots and metal stripes on the surface of a doped semiconductor material. When the dimensions of the dot or stripe are much larger than the depletion region, the results are reduced to the conventional formula for a parallel-plate capacitor. In the opposite limit, the overall capacitance is determined by the edge effect. This edge capacitance is proportional to the device periphery, with the coefficient of proportionality dependent on the shape of the metal. The parallel-plate component of the device capacitance is modulated by the applied voltage; the edge component is nearly independent of the applied voltage. Hence, the largest capacitance modulation is achieved in devices with the smallest ratio of the device periphery over the device area, which has the smallest edge effect. The measured capacitances of small round GaAs Schottky barrier diodes are in reasonable agreement with calculated results     

Radiation effects in transit-time microwave diodes

There has been considerable progress in the direct generation of microwave power using two-terminal semiconductor devices during the last decade. Permanent and transient radiation effects on bulk (Gunn and LSA) and junction (IMPATT, TRAPATT, and BARITT) transit-time microwave diodes are reviewed. Emphasis is placed upon relating the primary effects of radiation to the physics of device operation. The principal permanent damage is attributed to carrier removal effects, impairing the RF performance of bulk diodes below 10¹⁴neutrons/cm²and junction transit-time diodes at fluences near 10¹⁵neutrons/cm². The principal transient effect is the generation of free carriers by ionizing radiation, affecting the RF performance of bulk diodes above 10⁹rad/s and junction transit-time diodes at dose rates near 10⁸rad/s.     

Planar n-GaAs/N-GaAlAs microwave diodes

Planar microwave diodes have been fabricated from n-GaAs/N-(GaAl)As heterojunction layers grown on semi-insulating substrates by l.p.e. The diodes have successfully been used for detection and, for the first time, for down-conversion of X- and Ku-band signals, indicating that this type of diode is an attractive substitute for the Schottky-barrier diode.     

High-power microwave amplifier using IMPATT diodes

A single multichip IMPATT diode, operating in the unconditional amplifying mode, has been used as a reflection amplifier in the 6?8 GHz range. C.W. power-output levels of 4.0 W have been achieved with a stable reflection-amplifier circuit, using two multichip diodes in separate cavities coupled to a single circulator through an airstrip hybrid. The gain of the amplifier is 6 dB, with 250 MHz (?1 dB) bandwidth.     

Experimental study of microwave transmission in snowpack

Microwave transmission loss in a natural snowpack was measured to provide fundamental data for snow subsurface radar. The snowpack consisted of many horizontal stratified layers of relatively large density and water inclusion. Field strength measurements were carried out in the vertical direction across horizontal snow layers in the frequency range 0.6-7.0 GHz. The transmission loss and the extinction coefficients were obtained as a function of frequency     

Skin effect in microwave semiconductor diodes

It is commonly assumed that the skin effect is the cause of an increase in the series resistance of a semiconductor diode at microwave frequencies. This letter presents some simple theoretical calculations which show that the validity of such an assumption is highly doubtful.     

Experimental nonlinearity coefficients for the tungsten- nickel point-contact diode

Current-voltage characteristic curves of W-Ni diode contacts were determined experimentally, and are represented by the coefficients of polynomials of the fifth order fitted to the curves. Estimates of the accuracy of the coefficients are given, and main features of the curves and of the coefficients are discussed. It is observed that details of the characteristics only up to the second order are modeled fairly well by the WKB tunneling theory with trapezoidal potential barrier.     

High-efficiency microwave oscillations from Si avalanche diodes

High-efficiency microwave oscillations have been observed in Si p?n and p?n?n+ diodes under pulsed conditions. At about 25 mA reverse-bias current, a sudden decrease in voltage across the diode and an increase in bias current are observed, giving peak output power of 10?20 W and efficiency up to 30% between 1 and 3 GHz.     

Application of Si MBE to microwave hyperabrupt diodes

Hyperabrupt impurity profiles were formed by the Si molecular beam epitaxy (MBE) technique. Thin Sb-doped n-type epitaxial layers grown on n⁺substrates were used to successfully fabricate hyperabrupt varactor diodes. The characteristics of microwave diodes containing hyperabrupt profiles produced by a conventional ion-implantation and drive-in technique were compared with those having profiles "grown-in" by the MBE technique. The diodes made from Si-MBE films exhibited superior RF performance.     

Signal-compression performance of Schottky-barrier diodes in microwave mixers

Signal compression experiments on planar Schottky-barrier mixer diodes working at L and Xbands are described. The application of high local-oscillator drive powers enables signals as high as 1 mW to be down-converted to intermediate frequency with 0.02dB power compression, yet retaining noise factors of less than 7.0dB.     

Amplitude modulation of microwave signals using transferred-electron diodes

Described here is a microwave amplitude modulator that uses two GaAs0.85P0.15transferred electron diodes. The modulator remains matched for all depth of modulation, and requires a control voltage of only 0 to 4 volts.     

Thermoelectric detection of 10 µm energy using point-contact Schottky-barrier diodes operating at zero bias

Zero-biased-point contact Schottky-barrier diodes operating as detectors of 10 µm radiation are analyzed. It is found that a themioelectric process is responsible for the detected voltage observed experimentally. This process dominates all other detection mechanisms due to the high thermoelectric power coefficient of semiconductors. The time constants associated with the process are of the order of 0.4 µs.