Point-contact Diodes Research Articles

Indium Arsenide-Based Spontaneous Emission Sources (Review: a Decade Later)

The results of investigations of light-emitting diodes based on heterostructures with an InAs active region grown by liquid phase and metalorganic vapor-phase epitaxy over the last decade are reviewed. The near-field pattern, L–I and I–V characteristics, and quantum efficiency of point-contact and flip-chip light-emitting diodes are analyzed in a wide temperature range.

Источники спонтанного излучения на основе арсенида индия (обзор: десять лет спустя)

AbstractThe results of investigations of light-emitting diodes based on heterostructures with an InAs active region grown by liquid phase and metalorganic vapor-phase epitaxy over the last decade are reviewed. The near-field pattern, L – I and I – V characteristics, and quantum efficiency of point-contact and flip-chip light-emitting diodes are analyzed in a wide temperature range.

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies.

The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and Terahertz imaging. For about 45 years, the generation of coherent, far-infrared radiation has been accomplished using the optically pumped molecular laser. Once far-infrared laser radiation is detected, the frequencies of these laser emissions are measured using a three-laser heterodyne technique. With this technique, the unknown frequency from the optically pumped molecular laser is mixed with the difference frequency between two stabilized, infrared reference frequencies. These reference frequencies are generated by independent carbon dioxide lasers, each stabilized using the fluorescence signal from an external, low pressure reference cell. The resulting beat between the known and unknown laser frequencies is monitored by a metal-insulator-metal point contact diode detector whose output is observed on a spectrum analyzer. The beat frequency between these laser emissions is subsequently measured and combined with the known reference frequencies to extrapolate the unknown far-infrared laser frequency. The resulting one-sigma fractional uncertainty for laser frequencies measured with this technique is ± 5 parts in 10(7). Accurately determining the frequency of far-infrared laser emissions is critical as they are often used as a reference for other measurements, as in the high-resolution spectroscopic investigations of free radicals using laser magnetic resonance. As part of this investigation, difluoromethane, CH2F2, was used as the far-infrared laser medium. In all, eight far-infrared laser frequencies were measured for the first time with frequencies ranging from 0.359 to 1.273 THz. Three of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO2 pump laser, and strength.

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies

The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and Terahertz imaging. For about 45 years, the generation of coherent, far-infrared radiation has been accomplished using the optically pumped molecular laser. Once far-infrared laser radiation is detected, the frequencies of these laser emissions are measured using a three-laser heterodyne technique. With this technique, the unknown frequency from the optically pumped molecular laser is mixed with the difference frequency between two stabilized, infrared reference frequencies. These reference frequencies are generated by independent carbon dioxide lasers, each stabilized using the fluorescence signal from an external, low pressure reference cell. The resulting beat between the known and unknown laser frequencies is monitored by a metal-insulator-metal point contact diode detector whose output is observed on a spectrum analyzer. The beat frequency between these laser emissions is subsequently measured and combined with the known reference frequencies to extrapolate the unknown far-infrared laser frequency. The resulting one-sigma fractional uncertainty for laser frequencies measured with this technique is ± 5 parts in 107. Accurately determining the frequency of far-infrared laser emissions is critical as they are often used as a reference for other measurements, as in the high-resolution spectroscopic investigations of free radicals using laser magnetic resonance. As part of this investigation, difluoromethane, CH2F2, was used as the far-infrared laser medium. In all, eight far-infrared laser frequencies were measured for the first time with frequencies ranging from 0.359 to 1.273 THz. Three of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO2 pump laser, and strength.

Electromechanical tuning of nanoscale MIM diodes by nanoindentation

Abstract

English

Ion beam processing of materials in general and semiconductors in particular, started with ion implantation in semiconductors; first used by Ohl at Bell Labs in 1952 toimprove the electrical characteristics of silicon point contact diodes by implanting H, He, N and Ar ions.The improvement was obvious but it was caused by surface damage and notthe ion implantation. However, in the process, ion implantation had an entry and slowly it became popular among the scientists and the technocrats. Thus, over the last six decades, demands continued for new and improved materials and devices that has pushed ion implanter to expand to ion beam technology. In the semiconductor industry alone, the processes have evolved so much so that in today’s world, there are morethan 4000 ion implanters in the IC fab lines apart from otherion beam-assisted processing machines. Ion beam deposition techniques, ion beam lithography, ion beam etching, ion beammilling are all ion beam beam-assisted techniques that arebeing extensively used in semiconductor industries. In this backdrop, it was thought that a compilation of uses of allthese techniques together with relevant tools of analysis toserve as a guide to the semiconductor scientists and technologists for a glimpse of the ongoing efforts being madein this direction. Fortunately enough, Indian research is not lagging in use of all these modern day technologies that will be evident as the reader will go from one article to the other of this special volume. Defence Science Journal, 2009, 59(4), pp.328-328 , DOI:http://dx.doi.org/10.14429/dsj.59.1530

A Schottky-Diode Model of the Nonlinear Insulation Resistance Effects in SPRTs—Part 1: Theory

The decreasing insulation resistance of standard platinum resistance thermometers (SPRT) above about 850 °C makes a major contribution to uncertainties in measured temperatures. In principle, the insulation breakdown ought to be easily modeled as a temperature-dependent shunt resistance depending principally on the insulator materials and dimensions. However, the phenomenon exhibits a complex nonlinear behavior that, to date, has defied explanation. The lack of an explanation is a major obstacle to improvements in SPRT design and to assessments of uncertainty caused by the insulation breakdown. This article suggests that the nonlinear effects are due to metal–semiconductor diodes, also known as Schottky-barrier or point-contact diodes, formed at the points of contact between the fused-silica insulators and the platinum of the SPRT sensing element and lead wires. The article presents an overview of the theory underlying Schottky diodes, shows that this model qualitatively explains the observations, and suggests practical experiments to verify the model.

A Schottky-Diode Model of the Nonlinear Insulation Resistance in HTSPRTs—Part II: Detailed Two- and Three-Wire Measurements

Electrical leakage is a significant factor in the uncertainty of temperature measurements employing high-temperature standard platinum-resistance thermometers, with effects as large as several millikelvin at the freezing point of silver (962°C). The insulation resistance also exhibits complex behavior that includes non-linearities, sensitivity to the electrical environment, and the generation of spurious voltages and currents. In an earlier article, it was suggested that the behavior is consistent with the existence of metal–semiconductor diodes, also known as Schottky-barrier or point-contact diodes, formed at the points of contact between platinum wire and fused-silica insulators supporting the platinum. In this article, we describe detailed measurements of the non-linear resistance of a fused-silica insulator supported by platinum wires. The discussion includes a detailed description of the measurement system, and the results of two experiments that show many of the features suggested by the metal–semiconductor-diode model. Observed features in the current–voltage measurements include an S-shaped feature characteristic of back-to-back diodes, temperature dependence of saturation currents consistent with thermionic emission, and a diode polarity consistent with silica being a p-type semiconductor. Some impacts of the model on thermometry practice are also noted.

Measurements of Near-Infrared Frequency Mixing by Metal–Semiconductor Point-Contact Diodes

The performances of metal-semiconductor point-contact diodes as mixers in the near-infrared region were tested. Preliminary experiments were performed in order to phase-lock two diode lasers at 850 nm a few hundred gigahertz apart. GaSb, InAs, and InSb as semiconductor layers were used. The frequency bridge between the two lasers was covered by a Gunn diode frequency locked to a 1-GHz oscillator. A novel phase-lock circuit was tested on two diode lasers 72 GHz apart.

Imaging with THz quantum cascade lasers using a Schottky diode mixer

An imaging system in reflection geometry based on a multimode 2.9 THz quantum cascade laser as radiation source is reported. The beating between neighbouring longitudinal modes is detected using a room temperature point-contact Schottky diode as mixing element. We show that the technique can, in principle, give a dynamic range of 60 dB with a time constant of ~ 10 mus.

Heterodyne mixing of two far-infrared quantum cascade lasers by use of a point-contact Schottky diode.

We demonstrate heterodyne mixing of two free-running, multimode, 3.3-THz quantum cascade lasers by use of a point-contact Schottky diode. By temperature tuning the emission wavelength of one laser, a difference frequency signal spanning the 2-4-GHz range is obtained, with a signal-to-noise ratio of 30 dB. The frequency of the heterodyne signal is subject to random fluctuations of a few megahertz, principally from instabilities in the temperatures of the devices. From single-shot measurements we derive an instantaneous linewidth for a single Fabry-Perot mode of 20 kHz, corresponding to an integration time of 3.6 ms.

GaSb and InAs: New Materials for Metal-Semiconductor Point-Contact Diodes

Metal-semiconductor point contact diodes have proved to be good detectors and mixers for radiation from the far-infrared to visible. Until now GaAs, InSb and InP are the most studied and used semiconductor materials for these devices. In this work we present the performance in the visible and infrared region for metal-semiconductor point-contact diodes with GaSb or InAs as the semiconductor layers. These two new materials have shown good characteristics.

X-Ray Absorption Fine Structure Measurement Using a Scanning Capacitance Microscope: Trial for Selective Observation of Trap Centers in the ∼nm Region

For site-selective analysis of trap centers in a single nano-structure of a semiconductor, a new X-ray absorption spectroscopy technique using scanning probe detection of capacitance (scanning capacitance microscope-X-ray absorption fine structure; SCM-XAFS method) is proposed. Since capacitance is sensitive to localized electrons, X-ray induced photoionization of a trap center can be detected by capacitance change of the diode structure. The X-ray photon energy dependence of the capacitance involved in a point contact diode of a GaAs sample and Au-coated Si tip of SCM indicates XAFS spectra of the trap centers in the local region. Several resonant X-ray absorption peaks with different sample bias voltage dependences are found. The correspondence of the Fermi level to the specific trap level enhances the SCM-XAFS signal from the trap center, indicating that the site-selective observation of the trap center can be realized by bias control.

Studies on Surface and Interface with X-ray Absorption Fine Structure (XAFS). Microspectroscopy of Semiconductor Surfaces by SCM-XAFS Method.

For a site-selective analysis of trap centers on semiconductor surfaces, a new X-ray absorption spectroscopy using scanning probe detection of capacitance (Scanning capacitance microscope - X-ray absorption fine structure; SCM-XAFS method) is proposed. Since capacitance is sensitive to localized electron, X-ray induced photoionization of trap center can be detected in terms of capacitance change of diode structure. The X-ray photon energy dependence of the capacitance involved in a point contact diode of GaAs sample and Au-coated Si tip of SCM indicates XAFS spectra of the trap centers in the local region. The correspondence of the Fermi level to the specific trap level enhances the SCM-XAFS signal from the trap center, resulting that the site-selective observation of the trap center can be realized by bias control. The double resonance of the surface site selection (Fermi energy resonance) and the resonant X-ray absorption of the selected site (photon energy resonance) enhances the capacitance signal, indicating that the resonant X-ray absorption peaks can be assigned to the surface sites.

Performance of W-InSb Metal-Semiconductor Point-Contact Diodes as Detectors and Mixers in the Near Infrared

Metal-Insulator-Metal (MIM) and Schottky-barrier diodes have been used extensively in the past years as harmonic generators and mixers for frequency measurements in the spectral range from the far-infrared to the visible. MIM diodes present a very low fabrication cost and are easy to handle, while Schottky diodes are mechanically more stable and long-lived. In the present work we discuss the performance of a metal-semiconductor point-contact diode for the radiation around 1 μm. This device, which may be viewed as a hybrid between a MIM and a Schottky diode, combines the simplicity and easiness of fabrication of the MIM diode with the stability and the long contact life typical of the Schottky diode. It proved to be very efficient even for visible light.

A W–InSb point contact diode for harmonic generation and mixing in the visible

Metal–oxide–metal (MIM) and Schottky barrier diodes are widely used as harmonic generators and mixers and for frequency measurements from far infrared to visible. MIM diodes have a low cost of fabrication and are very easy to handle, while Schottky diodes are mechanically more stable and long lived. In this article we present the performance of a W–InSb point contact diode for radiation at visible wavelength; the device is very simple, easy to fabricate and costless, has the advantages of MIM as well as of Schottky diodes, and has proved to be very effective as both detector and mixer.

Modeling of ultrashallow spreading resistance probe calibration curves

Accurate determination of resistivity and carrier density from spreading resistance (SR) data depends heavily on the quality of the SR probes. This quality can be assessed by the shape of the calibration curve, which primarily depends on the properties and behavior of the point contact diodes. In this article, we demonstrate that the SR calibration curve can be simulated using an accurate representation of the SR equivalent circuit. This simulation includes physical models for the point contact diodes, the traditional geometric spreading resistance, and all parasitic resistances. Modeling of the point contact diode is emphasized based on measurements and analysis of the full current/voltage relationships for bulk p-type material.

Detection and Mixing Properties of an InSb Metal-Semiconductor Point Contact Diode

We present preliminary data on the performance of a new fast photodetector based on a W–InSb metal-insulator-semiconductor point contact diode operating at room temperature and with no bias voltage. The device can work either as a video detector or as harmonic mixer for radiation from far–infrared (FIR) to visible. In the FIR region, for wavelengths from 200 to 400 μm, the W–InSb point contact diode showed a sensitivity comparable to that of Golay cells. In the visible region the device showed a video and heterodyne detection responsivity much higher with respect to standard M.I.M. point contact diodes. Owing to its ruggedness, low cost and wide band of operation, the W–InSb point contact diode may be very attractive as a general purpose optical sensor.

Transistor Celebrates Half Century Mark

Although the invention of the transistor was not made public until 1948, the device in its earliest point contact form was demonstrated to Bell Labs management by it’s inventors John Bardeen and Walter Brattain in December 1947. As we reach the 50th anniversary of this landmark discovery we pause to reflect upon the momentous develclpments that stem from this “primitive” device. The first working transistor was primitive in construction, but sophisticated in terms of the research that had gone into the preparation and study of the, synthetic semiconductor material it embodied (n-type germanium). This primordial device was constructed by wrapping gold foil around a plastic “knife edge,” slitting the foil along this edge with a razor blade, and pressing the two closely spaced foil edges against a small germanium block having a large area metallic contact on its reverse side. The latter contact formed the tramistor “base,” while the foil edges operated interchangeably as “emitter” or “collector.” A power gain of 50 was achieved by this transistor, so here began some real competition for the wel:l established vacuum tube in it’s crucial role as signal amplifil-r. Later versions of the transistor were truly “point contact” in that a pair of fine pointed wires spaced about ,002’’ apart were spring loaded against the germanium block to form the emitter and collector contacts. It is worth noting that naturally occurring and relatively impure synthetic semiconductor materials in contact with metallic “cat whiskers” had been in use as radio frequency (RF) detectors for many years pri’or to the transistor’s advent. WWII research led to purer materials and the “doping” of silicon with Boron as a beneficial “impurity” for use in point contact diodes. This type of diode was resistant to “burnout” and vital to the success of microwave radars used in that conflict.

CW submillimeter laser action in ethyl chloride

We present ten new far-infrared (FIR) laser lines obtained by optically pumping ethyl chloride by means of a CW waveguide CO/sub 2/ laser with a tunability range of 300 MHz. By means of a heterodyne technique and using, as mixing element, a metal-insulator-metal (MIM) point contact diode or a new home built metal-semiconductor diode, we measured the frequency of all these new lines, as well as that of another line, previously reported in literature. With our new lines, the total number of FIR laser lines emitted by ethyl chloride rises to 14; for each of them we give the offset relative to the center frequency of the pumping radiation, the polarization relative to that of the pumping CO/sub 2/ laser, the relative intensity, and the optimum operation pressure. Seven of the new lines have frequencies in the 300-512-GHz range and four of them are strong enough to be used in high-field EPR spectroscopy.