Backward Diodes Research Articles

COLLISIONAL BROADENING AND SHIFT OF LINES IN THE 2 ν1+2 ν2+ ν3 BAND OF CO 2

Using a distributed feed back diode laser, pressure induced self-broadening and shift have been measured for several transitions in the 2 ν 1+2 ν 2+ ν 3 band of CO 2, centered at 1.573 μm. Foreign broadening and shift, with N 2 and O 2 as perturbing gas, have been measured for the most intense lines. The results for broadening have been compared with the data given by HITRAN molecular database and some discrepancies have been found, specially for air broadening derived from N 2 and O 2 broadening.

Characterization of a novel piezo-tunneling strain sensor

In this paper we characterize a novel silicon piezo-tunneling strain sensor having a very low temperature dependence of the sensitivity. The sensor is based on a shallow lateral backward diode with a prevailing band-to-band tunneling current in its reverse-bias characteristic. At the operating reverse bias, a gage factor K= 20 has been measured. The temperature dependence of the tunneling current is found to be small and of opposite sign to that of conventional piezoresistors. Furthermore, the change of the gage factor due to temperature is about one order of magnitude smaller than that of piezoresistors.

“Backward Diode” Characteristics of p-Type Diamond/n-Type Silicon Heterojunction Diodes

Rectification characteristics obtained for p-type diamond/n-type silicon heterojunctions have been studied. The current–voltage (I–V) characteristics of p-n heterojunctions show the same manner of rectification as in a backward diode. Forward current depends on both the concentration of boron atoms in polycrystalline diamond and the ambient temperature. The temperature dependence of I–V characteristics indicated that forward and reverse currents are mainly ascribed to diffusion and tunnelling currents, respectively. This current flow mechanism is peculiar to a backward diode. A simplified energy band model was proposed to explain the current transport mechanism in these heterojunctions. The experimental results can be explained with the aid of the proposed energy band model.

Study of ZnTe:Cu Back Contacts on CdTe/CdS Thin Film Solar Cells

AbstractVacuum-evaporated Cu-doped ZnTe films have been studied as the intermediate layer between CdTe and metal contacts in CdTe/CdS thin-film solar cells for the formation of low resistance back contacts. Different metals (Au, Ni, Co) have been investigated as the contact material to the ZnTe layer. The effects of Cu concentration, ZnTe:Cu layer thickness, and ZnTe post-deposition annealing temperature on the cell performances have been investigated. We found that different metal contacts on the ZnTe layer lead to different doping densities in the CdTe layer and different open-circuit photovoltages of the solar cells. The possible formation of a back contact diode at the CdTe/ZnTe interface was explored, based on capacitance-voltage analysis. The series resistance of the CdTe/CdS cells was reduced significantly by the introduction of the ZnTe layer. Fill factors greater than 0.76 and an energy conversion efficiency of 12.9% have been achieved using ZnTe back contacts on electrodeposited CdTe.

A novel /spl beta/-SiC/Si heterojunction backward diode

In this letter, a novel /spl beta/-SiC/Si heterojunction backward diode has been developed successfully. The developed new backward diode is somewhat different from a conventional one. The /spl beta/-SiC thin film was grown by a low pressure rapid thermal chemical vapor deposition (LP-RTCVD) using a SiH/sub 4/-C/sub 3/H/sub 8/-H/sub 2/ gas system. Its current-voltage characteristics under different operation temperatures (25-200/spl deg/C) have been measured. In addition, the curvature coefficient /spl gamma/ has also been calculated and it is found to be insensitive to temperature variation up to 180/spl deg/C. The operation temperature is the highest reported thus far, to our knowledge. >

Temperature dependence of schottky versus backward diodes for radiometry applications

AbstractIn this article the temperature behavior of Schottky and backward diodes operating as square‐law detectors at microwave frequencies is presented. To make a quantitative comparison between both diodes possible, the most important diode parameters are discussed. The criteria for comparison are the voltage sensitivity and the video resistance. © 1992 John Wiley & Sons, Inc.

I-V Characteristics and Interface Properties of Al-Si(P) Contacts by the Krf Excimer Laser Induced Recrystallization

ABSTRACTAl was deposited on the both sides of p-type Si by the sputtering, and the pulsed KrF excimer laser was irradiated on the one side and both sides of Al dot contacts. Due to the thin-high doping recrystallized layer, the transitions from the Schottky diodes to the ohmic contacts via backward diodes were observed in I-V measurement. Good N-shape negative resistances and notches were observed in the diodes, and ohmic contacts. Possible interpretations of the orgin of these phenomena are discussed. And, the simple model of the effective barrier height reduction under the thermionic field emission was developed using WKB approximation, and tunneling theory. By the depth Auger analysis, Al, and Si profiles near Al-Si interface after the laser irradiation were observed.

Modified SAW diode convolver

A modified SAW diode convolver is presented which works with backward biased diodes, so that no bias resistor is needed and taps are isolated from one another. The new distribution of taps makes it possible for the convolver to operate at lower frequencies and enables a relatively wide bandwidth. The experimental results of a device with 28 taps have been given.

Tunnel diode with asymmetric spacer layers for use as microwave detector

A novel single-barrier, intraband tunnel diodes with asymmetric spacer layers has been designed and fabricated. The structural asymmetry leads to asymmetric current-voltage characteristics and makes the diodes suitable for use as zero-bias microwave detectors. The voltage sensitivity as 9.375 GHz shows a weak temperature dependence (typically less than 1 dB variation over − 40° –+ 80°C, compared with 3 dB for a zero-bias Schottky diode). The maximum microwave power handling is also superior to a germanium back diode (1 dB rolloff typically at + 10 dBm compared with –10 dBm for the Ge back diode) and similar to a zero-bias Schottky diode.

Infrared photoresponse of carbon films prepared by plasma decomposition of propylene

The photoconductive effect of carbon films prepared by plasma decomposition of propylene was investigated for infrared radiation between 520 and 4200 cm−1. The carbon films deposited on glass substrates and on n-type silicon substrates showed an increase in electric current, i.e., photocurrent, on infrared irradiation. The increase in current by irradiation depended on the wave numbers of the light: the current was greater for lower wave numbers, and this spectral response suggested that the increase in the current was caused by an absorption of photons and not by the thermal effect of radiation. The dark current-applied voltage characteristics of the junctions between carbon films and n-Si varied with their preparation temperature (TP ) from rectifying behavior through backward diode behavior to ohmic behavior. The increments in current upon the infrared radiation of all films strongly depended on the applied voltage. The constituent that contributes to the photocarrier generation was estimated to be the poorly stacked condensed aromatic portions in the carbon films, using an infrared absorption parameter proposed by us, which represents the density of states of the π electrons in carbons.

Surface-field-induced transverse and vertical tunnel junctions

We report on tunneling between a 2D electronic system at the semiconductor/insulator interface influenced by an electric surface field and a 3D counterelectrode with tunneling directions parallel and perpendicular to the surface. Junctions of Yb and Au to electron and hole inversion layers, respectively, show thermally activated tunneling where the tunneling probability is controlled by the electric surface field. Vertical junctions consist of an Yb/oxide/semiconductor tunnel junction on a degenerate p-type Si, InAs, and InSb substrate. The low work function leads to a high electric field that inverts the semiconductor surface and forms a Zener tunnel junction between the electron layer and the bulk valence states. Current-voltage characteristics of junctions on Si are similar to backward diodes with phonon-induced structures at low temperatures. InAs junctions show room-temperature negative differential conductance with peak-to-valley ratios up to 2.7 increasing up to 15 at low temperatures. InSb junctions, which are nearly ohmic at room temperature, yield typical current ratios of 11. Junctions on high-quality InAs substrates exhibit a resonance-like characteristic which is explained in terms of wave vector conservation law.

Proposing a new backward solar cell

The object of the letter is to propose a new backward solar cell. The reason for calling it backward is because under dark conditions it behaves as a backward diode. The main advantage of this solar cell is the higher open-circuit voltage compared to the currently used p-n solar cell.

Properties of p+-n+ AlGaAs diodes

AlxGa1−xAs p+-n+ diodes have been studied in the direct band-gap range. Tunnel diodes were achieved in alloys with band gaps up to about 1.85 eV. For these devices the I-V characteristics show a second hump, which is believed to be due to tunneling from the conduction band on the n side of the junction to an impurity band on the p side of the junction. The location of this band was found to be independent of the band gap. In alloys with band gaps in the range 1.85–1.95 eV, backward diodes were obtained.

Back diode amplifiers for use at low temperature

The design of two amplifiers using negative resistance diodes is discussed. Measurements of the diode characteristics, voltage and power gain, and frequency response at ⋍ 1 K are presented.

Avalanche noise in GaAs m.e.s.f.e.t.s

Instabilities in the d.c. characteristics of GaAs m.e.s.f.e.t.s for drain to source voltages greater than 4 V. believed to be due to reloading of traps in the interface between active layer and bulk material, or gunn-domain formation, seem to have their origin in avalanche breakdown of the back diode under the drain contact. Microplasma switching, vertical to the active layer, strongly modulates the drain current producing large broadband noise power.

Sensitivity and Dynamic Range Considerations for Homodyne Detection Systems

The effects of modulation frequency, RF reference power, and external bias upon the sensitivity and dynamic range of microwave homodyne detection systems was measured for point contact diodes and low l/f noise Schottky and backward diodes. The measurements were made at 4.89 GHz using a signal to noise ratio of 3 dB and a detection system bandwidth of 10 Hz. Maximum sensitivities of -135, -150, and -145 dBm, and dynamic ranges of 92, 110, and 124 dB were measured for the point contact, Schottky, and backward diodes at modulation frequencies of 30, 30, and 3 kHz, respectively. It was found that the level of RF reference signal needed to obtain the maximum sensitivity was equal to or somewhat above the point where the diode changes from square law to linear detection. The results are significant in that previously reported homodyne sensitivities (not necessarily maximum) were on the order of -90 to -130 dBm for point contact diodes and no data are available for Schottky and backward diodes. Significantly improved stability, sensitivity, and dynamic range can be achieved using these low 1/f noise devices, the correct external bias, and the optimum RF reference power.

Backward Diodes as Sensitive Detectors for Microwave Spectroscopy

Signal-to-noise ratios for a backward and a point contact diode were investigated as a function of incident amplitude modulated microwave power. Measurements were made for a 30 kHz modulated carrier at 10 GHz. Comparison of the results reveals a gain of at least 10 dB in ultimate sensitivity for the backward diode over the point contact diode. In addition, the beneficial effect of an external dc bias could be substantiated.

Noise Spectrum Measurements from 10 Hz to 1 MHz Using a Tunable Switching Radiometer. II. Application to EPR

The 1/f noise spectra and conversion gain of 10 GHz point-contact, Schottky barrier and backward microwave diodes are compared with the object of determining the relative merit of their application in electron paramagnetic resonance (EPR) spectrometers. These measurements were made absolutely using the tunable switching radiometer described by BRI and relatively by determining the EPR microwave sample cavity power required to produce unity signal-to-noise ratio (SNR) as a function of the demodulation frequency.

Microwave backward diodes in InAs

The many advantages of backward diodes for microwave mixing and detecting—zero bias, low local oscillator power, low 1/ƒ noise, and environmental insensitivity—are significantly offset by the high capacitance associated with a narrow tunneling junction. This either severely limits high-frequency operation or requires small-area junctions which are fragile and susceptible to burnout at low power levels. This limitation can be reduced considerably by selection of a semiconductor with small band-gap and low carrier effective mass, with consequent high tunneling probability and reduced capacitance per unit area. Thus, a device of given size permits higher frequency operation, or equivalent electrical performance with larger area, leading to improved ruggedness and resistance to burnout. Computer-aided studies of the characteristics of tunneling junctions have confirmed the initial estimate that, among elemental and III–V semiconductors, InAs offers improved detector performance. Such devices have been fabricated, and microwave characterization of InAs backward diodes has been carried out. Measurements at 9 GHz on relatively large-area diodes show tangential sensitivity comparable to commercial (small-area) germanium backward diodes, with improved ruggedness and burnout resistance. Extension of this work to mixed compound semiconductors is suggested as a means of circumventing ambient temperature limitations of InAs.

Tunnel diode transient analysis with a nonlinear load

Analytic closed-form expressions for the switching time of a tunnel diode trigger are obtained with backward diode as a nonlinear load. For given operating points the nonlinear load increases the stability and the sensitivity of the trigger, maintaining almost the same order of switching speed as for a linear load.