Showing papers on "Capacitance published in 1970"

Measurement of the ionization rates in diffused silicon p-n junctions

Abstract: An improved method is presented for calculating the ionization rates αn and αp from charge multiplication measurements on diffused silicon p-n junctions. The main features of this method are: The real impurity profile is approximated by an exponential function whose parameters are calculated from capacitance measurements; the ratio γ = αp/αn as a function of the electric field is calculated from multiplication measurements; the ionization rates are solved from the ionization integral for pure electron injection, taking the influence of the threshold energy into account. Measurements on narrow junctions agree with measurements on wide junctions by assuming a threshold energy of 1.8 eV for electrons, in agreement with the results of M oll and van O verstraeten .(1) The ionization rates differ from those of M oll and van O verstraeten (1) and of L ee , L ogan et al.(2) mainly because these authors neglect the influence of the threshold energy. The electron and hole data satisfy Chynoweth's law α(E) = α ∞ exp (−b/¦E¦), cm −1 with: for electrons α∞ = 7.03 × 105 cm−1 b = 1.231 × 106 V cm−1 for 1.75 × 105 ⩽ E ⩽ 6.0 × 105 V cm−1 for holes α∞ = 1.582 × 106 cm−1b = 2.036 × 106 V cm−1 for 1.75 × 105 ⩽ E ⩽ 4.0 × 105 V cm−1 and α∞ = 6.71 × 105 cm−1b = 1.693 × 106 V cm−1 for 4.0 × 105 ⩽ E ⩽ 6.0 × 105 V cm−1 Breakdown voltages are computed for high voltage p-n and p-i-n diodes. These are in good agreement with experiments, indicating the reliability of the ionization rates.

A quasi-static technique for MOS C-V and surface state measurements

Abstract: A quasi-static technique is discussed for obtaining the ‘low frequency’ thermal equilibrium MOS capacitance-voltage characteristics The method is based on a measurement of the MOS charging current in response to a linear voltage ramp, so that the charging current is directly proportional to the incremental MOS capacitance With this technique, surface potential and the surface state density can be obtained relatively simply and over a large part of the energy gap on a single sample, while also providing a direct test for the presence of gross nonuniformities in MOS structures This method has been used to determine the surface state distribution at the interface of a bias grown steam oxide and 10 ω-cm n -type silicon, and the results are compared with composite measurements using the conductance technique for a similar interface The sensitivity for surface state density measurements is estimated to be of the order of 10 10 states per cm 2 eV near mid-gap for 10 ω-cm silicon and improves with decreasing doping density Some applications and limitations are also briefly discussed

Thermal and optical emission and capture rates and cross sections of electrons and holes at imperfection centers in semiconductors from photo and dark junction current and capacitance experiments

Abstract: Photo and dark current and capacitance transient experiments are described which can provide highly accurate and unique data of the electronic properties of impurity centers in semiconductors such as energy level, multiplicity of charge state, thermal and optical emission rates, thermal capture rates, thermal and optical cross sections and the dependences of the rates and cross sections on sample temperature, static electric field and photon energy. These experiments are grouped into four categories in the discussion according to the temperature (below and above freeze-out or negligible and finite thermal rates) and presence or absence of optical excitation at the impurity center. Each category is subdivided into a number of cases according to the method used to set the initial charge state of the impurity center prior to the measurements. Methods of setting the initial state include electrical switching of the bias voltage and optical excitation using either interband or band to impurity monochromatic light. Experimental examples are given for many of the experiment methods discussed.

Interdigital Capacitors and Their Application to Lumped-Element Microwave Integrated Circuits

Abstract: An analysis of the frequency response of interdigital capacitors, which leads to an optimal design, is given along with an expression for their static gap capacitance. The capacitor Q is given in terms of its geometry which consists of a planar interdigital thin-filrn conductor deposited on the surface of a relatively high dielectric constant substrate. Capacitance values ranging from 0.1 to 10 pF at L band with measured Q's in excess of 400 are realizable using 2-mil line and space widths on a 99.5-percent alumina substrate with a dielectric constant of 10.3. Experimental results obtained with a lumped-constant nine-section S-band Chebyscheff low-pass filter realized using spiral inductors and optimal designed interdigital capacitors are shown to be in excellent agreement with theory. The filter had less than 0.8-dB insertion loss and greater than 25dB return loss in the passband. The filter occupies an area 6.50 by 200 roils on a 24-mil-thick substrate.

Calculation of Coefficients of Capacitance of Multiconductor Transmission Lines in the Presence of a Dielectric Interface

Abstract: A method is given for the numerical determination of the coefficients of capacitance for a class of multiconductor transmission-line systems. This class includes systems without ground planes, or with one or two ground planes, with the lines embedded in one or two layers of dielectrics. The conductors can be of any cross section that can be approximated adequately by polygons. The method is a refinement of the subareas method in which the assumption of a "staircase function" surface charge density, that is, constant charge density over each subarea, is replaced by the assumption of a piecewise linear charge density over the conductor surfaces, and the charge density parameters are determined by making a least-squares fit to the potential to the boundary conditions of the problem.

Transient Analysis of Lossless Coupled Transmission Lines in a Non-Homogeneous Dielectric Medium

Abstract: This paper presents an effective method for computing the transient response of an n-conductor, coupled transmission-line system, which is characterized by multiple propagation modes of unequal phase velocities. To derive the computational algorithm, an equivalent circuit consisting of n decoupled transmission lines in conjunction with two congruence transformers was constructed and converted into two disjointed resistive n-ports. It is shown that the electrical behavior of the coupled transmission lines can be completely described by the static capacitance matrices of the conductor system. The experimental result obtained on a three-conductor, microstrip printed circuit was found to be in excellent agreement with the computed result.

Alternating Current Electrical Properties of Highly Doped Insulating Films

Abstract: Metal‐insulator‐metal systems are discussed in which the insulator is highly doped and in which Schottky barriers exist at the metal‐insulator interface. An equivalent circuit for the system is proposed and the ac electrical characteristics derived. It is shown that the capacitance is extremely temperature and frequency dependent. At high frequencies or low temperatures the capacitance is thickness dependent and equal to the geometric capacitance. At low frequencies and high temperatures it is thickness independent and equal to the Schottky barrier capacitance, which is determined by the doping density. Several methods of determining the activation energy of the donor centers from experimental capacitance versus frequency and temperature curves are suggested. The parallel equivalent conductance is also shown to be extremely frequency and temperature sensitive. It is found to have a pronounced maximum in both cases, which increases in magnitude and occurs at higher temperatures the thicker the insulator.

Electrical Properties of Evaporated Molybdenum Oxide Films

Abstract: Thin film capacitors of MoO3 are found to be extremely temperature and frequency dependent Changes in capacitance are reported as high as 60:1 over a temperature range of 100°C (at constant frequency) and over a two‐decade frequency range (at constant temperature) At lower temperatures and higher frequencies the capacitance corresponds to the geometric capacitance, but at higher temperatures and lower frequencies the capacitance is independent of the film thickness Conductance and quality factor of the films are also observed to be extremely frequency and temperature sensitive The results are explained in terms of Schottky barriers existing at the metal‐insulator interfaces, which arise due to the autodoping of the insulator, occurring during deposition of the films, by excess molybdenum Excellent agreement is found to exist between the experimental data and the theory developed in the previous paper, and this correlation permits determination of the doping density (≃1018 cm−3), the donor depth (≃02

Capacitance and Field Distributions for Interdigital Surface-Wave Transducers

Abstract: : A boundary-shift technique used in conjunction with relaxation solutions of Laplace's equation allows the convenient numerical evaluation of the potential in the neighborhood of interdigital comb structures. With this method, the area of computation in the unbounded problem can be restricted to the region of interest near the electrode and interface surfaces. Because of the point-by-point nature of the calculation, a wide range of geometries can be studied with the inclusion of the effects of finger thickness and shape, and of any layers present. Capacitance values for many single interface and layered configurations of surface-wave transducers are presented along with a few representative examples of potential and field maps. (Author)

Photovoltaic Properties of Cu2S–CdS Heterojunctions

Abstract: Heat treatment and photovoltaic properties of copper disulfide-cadmium sulfide heterojunctions, measuring I-V characteristics, capacitance and spectral response

Direct‐Current Polarization During Field‐Assisted Glass‐Metal Sealing

Abstract: Thin plates of borosilicate glass were polarized near the annealing point with a dc voltage of typically 600 V. From the measurements of capacitance and current, the width of the polarized region and the electric field within the region were deduced. The results indicate that the glass layer adjacent the anode becomes depleted of positive sodium ions and of compensating negative charge. As a result, the electric field in the layer acquires a maximum value of the order of 106 V/cm. Some implications of the process with regard to field-assisted glass-metal sealing are discussed.

Linear Electrical Properties of the Transverse Tubules and Surface Membrane of Skeletal Muscle Fibers

Abstract: With the use of two intracellular microelectrodes and a circuit designed to compensate for the effects of stray capacitances around the electrodes, transfer impedance measurements were made at frequencies from 05 to 1000 c/s on frog sartorius muscle fibers bathed in 75 mM K Ringer solution Complete AC cable analyses performed at 46, 100, 215, 464, and 1000 c/s showed that the fibers behaved as ideal one-dimensional cables having purely resistive internal impedances (Ri = 102 ± 11 Ω cm) Two circuits were considered for fiber inside-outside impedance, a four lumped parameter circuit and a parallel resistance and capacitance shunted by the input impedance of a lattice model for the T-system Least squares fits to fiber input impedance phase angles were better with the latter circuit than with the former With the use of the lattice model the specific capacitance of both the surface and transverse tubule membranes was found to be 1 µF/cm2 and the internal resistivity of the tubules to be about 300 Ω cm

Shielded capacitance pressure sensor

Abstract: A capacitance-type pressure sensor having a reference capacitor plate and embodying a shield surrounding the lead wire and reference plate support assembly and maintained at substantially the same potential as the lead wire and reference plate. The shield extends substantially coplanar with the reference capacitor plate so that errors due to shunt capacitances are eliminated.

Double layer capacitance and relaxation in electrolytes and solids

Abstract: After a review of the idealizations usually made in theories of space-charge polarization in liquids and solids, published theoretical and experimental work dealing with the a.c. response of two-electrode systems is discussed and various corrections pointed out. A calculation of the equilibrium space charge capacitance of two blocking electrodes separated by material containing mobile positive and negative charge of arbitrary valences is presented for the limit of vanishingly small applied static potential. The result of this calculation may be used to obtain the frequency dependence of diffuse layer parallel capacitance and conductance in the Debye dispersion frequency range, where the motion of charges in space charge regions leads to an admittance involving only a single time constant. Expression given previously by Baker and Buckle for this time constant and for the low-frequency limiting capacitance are corrected, along with their conditions for the extent of the Debye dispersion range. The relaxation time constant is G∞(r–1)τD/G0, where G0 and G∞ are the low-and high-frequency limiting values of the series conductance, τD is the dielectric relaxation time of the material containing mobile charges, rM cotanh M, and M is the ratio of the separation between electrodes to twice the Debye length. Finally, deviations from Debye dispersion behaviour for various 1 : 1 valence theories are calculated and compared; for the two-blocking-electrodes situation, Debye behaviour and a simple equivalent circuit of frequency-independent elements extend up to nearly ωτD∼1. Beyond this range, the parallel space-charge capacitance shows ω– limiting behaviour, similar to that previously found only with partly blocking electrodes, and the equivalent series space-charge capacitance eventually decreases as ω–½.

Differential capacitance circuitry for differential pressure measuring instruments

Abstract: Capacitance measuring circuitry is disclosed which includes a source of alternating current and a first capacitor having two plates connected on one plate to a first terminal of the alternating current source. A second capacitor is connected on one plate to the same terminal of the alternating current source. A first diode is connected at its anode to the second plate of the first capacitor and a second diode is connected at its cathode to the second plate of the first capacitor. A filter network is connected to the cathode of the first diode and the anode of the second diode with the anode of the second diode being connected to a second terminal of the alternating current source. A third diode is connected at its cathode to the second plate of the second capacitor and a fourth diode is connected at its anode to the second plate of the second capacitor. The anode of the third diode and the cathode of the fourth diode are connected to the filter network and the anode of the third diode is connected to the second terminal of the alternating current source. The circuitry enables precise comparison and measurement of small capacitances such as those encountered with differential pressure measurement instruments.

Dependence of Schottky Barrier Height on Donor Concentration

Abstract: Schottky barrier heights of Au contacts to n‐type Si with either etch‐polished or vacuum‐cleaved interfaces are independent of donor concentration within an experimental uncertainty of about ±0.05 eV for 1014 cm−3≤ND≤1019 cm−3. Within the same uncertainty and over the same doping range, barrier heights determined from capacitance using the standard formula are equal to those determined from photoemission thresholds. A theory for deducing barrier heights from photoemission thresholds that includes the effects of tunneling and image force is presented. The results are interpreted in terms of a simple model for the interface, which is characterized by the thickness d and dielectric constant κ′ of the interfacial film and the density nss of interface states. The insensitivity of the barrier height to the quantity of space charge leads to the following limit on the interfacial parameters: (k′/d)+1.8×10−6nss≥3.8×108 cm−1 for d in cm, and nss in cm−2 eV−1.

Properties of Si diodes prepared by alloying Al into n-type Si with heat pulses from a Nd:YAG laser

Abstract: p − n junctions have been prepared by locally alloying a vacuum-evaporated Al film into n -type Si with a focused heat pulse derived form a Nd:YAG laser. The preparation and the gross features of such junctions are described and electrical measurements of the forward bias and reverse bias current, reverse bias capacitance and transient response are given for room temperature. The forward and reverse bias current measurement show that charge recombination and generation within the depletion region controls the flow of current as would be expected for a Si junction. The reverse bias capacitance shows that the change in the doping profile in these junctions is abrupt. From the transient response the reverse recovery time is typically 0.5 × 10 −9 sec.

Accurate Determination of the Dielectric Constant by the Method of Substitution

Abstract: A substitution method for highly accurate determination of the static dielectric constant of solids is presented along with techniques for refining capacitance measurements. The results for some alkaline earth fluorides are CaF2, 6.799; SrF2, 6.466; and BaF2, 7.359; and an alkali halide KCl is 4.818.

Electronically tunable matching circuit for circulators

Abstract: A novel matching circuit for a circulator of the type requiring a resistance and capacitance for tuning and matching the circulator. The matching circuit includes an electronically variable resistance and capacitance means for enabling optimum performance of the circulator over the range of its operating frequencies.

Quantitative analysis of the effects of steady-state illumination on the MOS-capacitor—I. Theory

Abstract: A detailed theoretical investigation is made into the effects of steady state illumination on the MOS-capacitor characteristics. Solutions are given for the C–V characteristics in the low and high frequency limits, and a general solution for the total admittance is developed in terms of a simple lumped circuit model, which is approximately valid for all gate voltages and for test frequencies below the majority carrier relaxation frequency. Suggested techniques for determining the lumped circuit elements are noted and a scheme for evaluating the light perturbed carrier concentration directly from capacitance data is outlined. The band to band communication, which is enhanced by illumination, is studied assuming a single level recombination center, and the effect of the center's parameters and the light intensity on the recombination resistance is deduced. Finally, the expected dependence of the perturbed carrier concentrations on the light intensity, light wavelength, and incident light orientation is derived.

Miniature feed-through wide band bypass capacitor assembly

Abstract: A miniature capacitor assembly comprises a plurality of capacitors each having laterally spaced plates embedded in a ceramic block with alternate plates terminating in contact members at opposite ends of the block. The capacitors are disposed in circumferentially spaced radial array inside a conductive ring with a conductive member at the center of the ring. The contact members contact the ring and conductive member respectively so that the capacitors are effectively in parallel with each other. The capacitors have different capacitance values whereby the assembly has an overall attenuation-frequency characteristic which is substantially flat over a range as high as 14 gigahertz.

Device for measuring permittivity of materials

Abstract: A device for measuring permittivity of materials on the basis of at least two different capacitance values of a measuring capacitor connected to the material being tested and to a measuring oscillator the output of which is coupled to one input of a mixer whose other input is coupled to a reference oscillator and whose output is coupled through a frequency meter to a resetting unit, characterized in that the measuring capacitor has at least two main electrodes permanently connected to the input of the measuring electrodes permanently connected to the input of the measuring oscillator, and one additional electrode alternately connected by a switch to one of the main electrodes in the course of measurement, while said resetting unit is connected to a pulse counter of the frequency meter through a switch actuated synchronously with said switch of the measuring capacitor electrodes so that in one position of this switch the frequency of the measuring oscillator is above, and in the other position of the switch, below the frequency of the reference oscillator.

Integrated circuit process utilizing orientation dependent silicon etch

Abstract: Orientation-dependent etching is employed in the fabrication of a monolithic semiconductor circuit network to provide electrical isolation and increased packing density, while minimizing collector series resistance and output capacitance. Collector contact to a transistor component is made by the direct metallization of a buried low-resistivity substrate region exposed by the preferential etching operation.

Overload Recovery Circuit for Charge Amplifiers

Abstract: In this paper the operation of low noise charge preamplifiers under high instantaneous pulse rates - "bursts" - is considered. An overload recovery circuit employing a field-effect transistor as the switch for the recovery current is described. The overload charge generated in the detector by the radiation burst in a time short compared to the small signal resolving time of the spectrometer may be 105 or more times larger than the charge due to a single particle to be measured between the bursts. The recovery time of the charge amplifier with the recovery circuit is less than 10 ?sec. With a conventional amplifier-filter, the recovery time of the system to within the noise level is 50 to 100 ?sec. The increase in noise due to the recovery circuit corresponds to an increase in the input capacitance of the charge amplifier of 2 pF.

Efficient low voltage piezoelectric power supply

Abstract: An electric device for efficient transfer of power from a piezoelectric crystal source to a capacitor. The piezoelectric crystal is coupled to a transformer, the secondary of which is shunted by a series combination of a rectifying device and a storage capacitor, all in such manner that energy is transferred from the piezoelectric crystal, essentially a first capacitance device, to the storage capacitor, a second capacitance device, with a new order of efficiency. In a specific embodiment of the invention the piezoelectric crystal and two capacitances are associated with biasing networks and a transistorized switching circuit and a firing circuit in such manner that the energy transferred into the storage capacitor is utilized to fire a squib.