Showing papers in "Solid-state Electronics in 1966"

Field and thermionic-field emission in Schottky barriers

Abstract: Field emission and thermionic-field (T-F) emission are considered as the phenomena responsible for the excess currents observed both in the forward and reverse directions of Schottky barriers formed on highly doped semiconductors. Voltage-current characteristics are derived for field and thermionic-field emission in the forward and reverse regime. The temperatures and voltages where these phenomena are predominent for a given diode are discussed. Comparison with experimental results on GaAs and Si diodes shows good agreement between theory and experiments.

Current transport in metal-semiconductor barriers

Abstract: A theory for calculating the magnitude of majority carrier current flow in metal-semiconductor barriers is developed which incorporates Schottky's diffusion (D) theory and Bethe's thermionic emission (T) theory into a single T-D emission theory, and which includes the effects of the image force. A low electric field limit for application of this theory is estimated from consideration of phonon-induced backscattering near the potential energy maximum. A high electric field limit associated with the transition to T-F emission is estimated from calculations of the quantum-mechanical transmission of a Maxwellian distribution of electrons incident on the barrier. The theory predicts a wide range of electric field ≈ 2 × 10 2 to 4 × 10 5 V/cm over which the T-D theory may be applied to metal- n -type Si barriers at 300°K. The corresponding range for metal- n -type GaAs barriers is 9 × 10 3 to 8 × 10 4 V/ at 300°K. The decreased upper limit is due mainly to the smaller electron effective mass in GaAs, the increased lower limit to a small optical-phonon energy and a shorter electron-optical-phonon mean-free path. The theory predicts Richardson constants of 96 and 4.4 A/cm 2 /°K 2 for metal- n -type Si and metal- n -type GaAs barriers respectively. Experimental measurements on both metal-Si and metal-GaAs barriers are in general agreement with the theory. Values of the barrier n [( q / kT )(d V /d ln J )] appreciably greater than unity are predicted for the field-dependent barrier height which occurs when an interface layer of the order of atomic thickness exists between the metal and the semi-conductor. A field dependence of the barrier height is shown to have no first order effect on the derivative of the 1/ C 2 vs. V relationship for the barrier. The intercept of a 1/ C 2 vs. V plot is shown to yield the barrier height extrapolated linearly to zero field in the semiconductor. Experimental evidence for the existence of interface layers in near-ideal Schottky barriers is also presented.

Effects of diffusion current on characteristics of metal-oxide (insulator)-semiconductor transistors☆

Abstract: A qualitative discussion of the device operation is first given using three-dimensional energy band diagrams to show the significance of the diffusion current. The theoretical static I–V characteristics are the computed including both the diffusion and the drift currents, based on the one-dimensional and gradual channel model. Drain current saturation phenomena are evident in these exact solutions which are in good agreement with the calculations based on the bulk charge approximation and with the experimental data for the entire non-saturating and saturated ranges. The relative importance of the two current components along the length of the channel is illustrated. The effects of the diffusion current on the three more important low-frequency dynamic characteristics (the short-circuit gate capacitance, the transconductance, and the drain conductance) are discussed. The surface potential, the quasi-Fermi potential, the surface electric field and the surface carrier concentration along the channel are examined. The complete one-dimensional gradual channel model is inadequate to account for the large drain conductance observed in the saturation range, and it is shown that the electric field longitudinal to the channel current flow must be taken into account near the drain junction where it is larger than the transverse field due to the voltage applied to the gate electrode.

Surface effects on p-n junctions: Characteristics of surface space-charge regions under non-equilibrium conditions

Abstract: The nature of the surface space-charge region associated with a p-n junction is studied theoretically and experimentally. The theory of MOS structures is extended to the case where the surface space-charge region is not in equilibrium. The validity of this extension is demonstrated by capacitance and conductance measurements performed on gate-controlled planar silicon diodes of various geometries. The non-equilibrium MOS theory is then used as the basis for studying the recombination-generation process within the surface space-charge region of gate-controlled diodes. It is shown that the I–V characteristics of such diodes yield a measure of both the surface recombination-generation rate and the bulk recombination-generation rate within the surface depletion region. The surface recombination velocity in the thermally oxidized silicon structures studied is found to be of the order of 5 cm/sec.

Metal-semiconductor surface barriers

Abstract: The physical principles underlying the metal-semiconductor barrier are discussed in the light of recent experimental results. A semi-empirical approach for predicting the type of contact to be expected at an arbitrary metal-semiconductor interface is presented.

Properties of gold in silicon

Abstract: The electrical properties, solubility and diffusion characteristics of gold in silicon are reviewed. It is observed that theoretical calculations and experimental measurements of the effect of added gold on the resistivity of silicon are not in agreement and that while some of the discrepancies, particularly those occurring in n -type silicon can be explained, those appearing in the p -type case cannot be resolved at the present time. The diffusion characteristics have been shown by many workers to be strongly structure sensitive. More work is required to establish firmly the values of the effective diffusion coefficients and the conditions under which various diffusion mechanisms are dominant. Enhancement of the apparent gold solubility has been observed in heavily phosphorus doped silicon. It is shown that this may be a real increase in solubility resulting from the effect of the position of the Fermi level in n + -regions. On the other hand, the increased gold concentration observed may result from the interaction of gold and phosphorus to form ion pairs or compounds. The effect of diffusion in junction regions containing large electric fields has not been studied explicitly. Published evidence indicates that in lightly doped material, gold does not precipitate significantly at dislocations during normal cooling from diffusion temperatures but redistribution can occur during prolonged treatment at intermediate temperatures. The increased solubility of interstitial gold in p + -silicon may make precipitation possible in this case but such studies have not been reported. In addition, when ion-pairing or compound formation occurs, the concentration of the electrically active substitutional gold is likely to be significantly less than the total gold concentration. Gold has been shown to be more efficiently gettered by a phosphorus glaze than by a boron glaze.

Zur berechnung des tunnelstroms durch eine trapezförmige potentialstufe

Abstract: Zusammenfassung Fur eine trapezformige Potentialstufe werden Durchlassigkeit D und elektrischer Tunnelstrom I als Funktion der Spannung V berechnet. In fruheren Arbeiten wurde hierzu die WKB-Naherung verwendet und daher auch nur die Potentialschwelle zwischen den klassischen Umkehrpunkten berucksichtigt. Nach der WKB-Naherung steigt die Durchlassigkeit einer trapezformigen Potentialschwelle monoton mit der angelegten Spannung an. In dieser Arbeit wird in einer genauen Rechnung die Wirkung der gesamten Potentialstufe erfasst. Dabei stellt sich heraus, dass der mit V ansteigenden Durchlassigkeit D(V) eine erhebliche periodische Schwankung uberlagert sein kann. Sie entsteht durch Interferenz von Elektronen-Wellen in dem Bereich der Potentialstufe, in dem die kinetische Energie der durchlaufenden Elektronen grosser als die potentielle Energie der Schwelle ist. Diese periodische Schwankung von D(V) bewirkt, dass auch der Tunnelstrom-Charakteristik I(V) eine merkliche periodische Schwankung uberlagert sein kann. Voraussetzung fur die Beobachtbarkeit solcher Tunnelstrom-Kennlinien in Sandwich-Schichten aus Metall-Dielektrikum-Metall ist eine genugend grosse freie Weglange (vermutliche einige hundert AE) der Elektronen im Dielektrikum und ordentliche Reflektion (z.B. ohne Streuung) der Elektronen an der Grenze Metall-Dielektrikum.

Effect of junction curvature on breakdown voltage in semiconductors

Abstract: The effect of the radius of curvature of the metallurgical junction (or junction curvature) on avalanche breakdown voltage is herein computed numerically for spherical and cylindrical p-n junctions in Ge, Si, GaAs and GaP. Three types of impurity distribution have been considered: abrupt, linearly graded and composite. For the composite distribution the space charge terminates in a graded region on one side of the junction and in a uniformly doped region on the other side. The results, which are presented graphically, show that for abrupt junctions the breakdown voltage, VB, decreases with decreasing radius of curvature, rj, the effect being larger for spherical junction than for cylindrical junction. Typically, for Si abrupt junctions with a background doping of 1015 cm−3, VB is 330 V for a plane junction, 80 V for a cylindrical junction with rj = 1 μ, and 39 V for a spherical junction with the same junction radius. For linearly graded junctions however, VB is essentially independent of rj. For composite junctions, at small impurity gradient VB is nearly equal to that of linearly graded junctions; at large impurity gradient, however, VB is determined by rj and the background doping. The results presented here can be applied to junctions formed by planar technology where the edge of the junction has cylindrical and/or spherical geometry with radius of curvature approximately equal to the junction depth. It is further suggested that the radius of curvature is an important design parameter in high power and higher frequency semiconductor devices as well as in integrated circuits.

Edge emission of n-type conducting ZnO and CdS

Abstract: Edge emission luminescence of ZnO and CdS appears in useful intensity at room temperature if the materials are n-type doped and prepared under reducing conditions. The emission spectra consist each of a structureless band near to the optical absorption edge. The luminescences are extremely fast, the time constants of their probably exponential decay are at most 10−9 sec. The emissions are assumed to be due to electron transitions from shallow states below the conduction band.

Appraisal of semiconductor-metal-semiconductor transistor

Abstract: This paper considers the basic limitations of a semiconductor-metal-semiconductor transistor (SMST) and evaluates its performance in practical microwave circuits. The low frequency common-base current gain α0 for SiAuGe and SiAgGe transistors is about 0.3. Discussion is presented suggesting that it is unlikely that materials combinations exist capable of substantially higher α0. Thus the transistor shows current loss and can attain power gain only by means of impedance gain. In coaxial-line and waveguide structures both high and low impedance levels require very small mechanical dimensions and tolerances. With present technology, attainable impedance ratios appear to be limited to about 100. The technological problems associated with the fabrication of the SMST are discussed. The greatest obstacle is the deposition of device-quality semiconductor material on thin metal films. For a SiAuGe structure with a collector epitaxial layer 1 μ thick, base-metal thickness of 100 A, emitter stripe width of 1 μ, and at a current density of 3000 A/cm2, the calculated values at 10 GHz are: 26 db for the unilateral gain, 29 db for the maximum stable gain with a resistance ratio of 104 and about 10 db for the transducer gain with a stripe length of 1000 μ and a resistance ratio of 100, where no parasitic losses were included in the above figures and optimum adjustments were assumed for reactive components of generator and load immitances. For an α0 of 0.3 the minimum noise figure in an SMST is 7.9 db.

A Metal-Oxide-Semiconductor (MOS) Hall element

Abstract: A new type of Hall element is described which is fully compatible with monolithic integrated circuit technology. By combining the Hall effect, normally a bulk phenomena of the material, with the MOS transistor structure, useful Hall voltages may be obtained in silicon. Further, the MOS Hall element can be totally isolated from other components in the monolithic die. A brief review of the MOS transistor fabrication and characteristics is given as a pertinent introduction to the MOS Hall element. The experimental results are confined to the d.c. static characteristics of p -channel MOS Hall elements and include: the Hall voltage as a function of the device drain-source current, the gate-source voltage, the magnetic field strength and the geometric length to width ratio of the inversion layer. The mobility of both n - and p -type MOS devices is discussed and some suggestions for improving the output Hall voltage are given. The conflicting design criteria for MOS transistors and Hall elements is considered, as well as the possibility of fabricating Hall elements with MOS transistors, bipolar transistors, resistors, etc. on the same silicon substrate.

Diffusion of nitrogen into silicon carbide single crystals doped with aluminum

Abstract: Single crystals of silicon carbide with bulk aluminum concentrations of 1017 to 1·5 × 1019/cm3 have been diffused with nitrogen at temperatures from 2000 to 2550°C. Transport and decomposition effects were minimized by diffusing under almost uniform temperature conditions in the central zone of a growth furnace. Nitrogen partial pressures from 0·1 to 1 atm were used. Diffusion times up to 268 hr produced diffusion depths between 0·3 and 5 μ. Diffusion was measured by observing junction depths when exposed by etching, secondary-emission electron microscopy and “cold” thermal probing. The diffusion depth varies as the square root of time suggesting that Fick's law is obeyed. The activation energy for nitrogen diffusion is found to be between 7·6 and 9·3 eV and D0 lies between 4·3 cm2/sec and 8·7 × 104 cm2/sec. These values are considerably higher than those reported for the diffusion of aluminum in silicon carbide.

Influence of non-uniform thickness of dielectric layers on capacitance and tunnel currents

Abstract: The paper deals with the influence of non-uniform thickness of dielectric films both on capacitance and tunnel currents of thin film elements with a MIM structure. For the dielectric film thickness the relation s = nq is assumed, where q is a constant and n is an integer with Poisson distribution. It is shown that a systematic difference s −s c ≈ q exists between the thickness s c determined from the capacitance measurement, and the mean thickness s . Furthermore, the paper studies in some details the influence of non-uniform thickness on the tunnel current and points out that especially under favourable conditions the ratio ( s T s ) vs. s may be constant ( s T is the thickness determined from the tunnel current). It may be shown as well that under quite reasonable assumptions for q , in the case of AlAl 2 O 3 Al sandwiches, s T ≈ 1 2 s c , as has been found experimentally. Some proofs of important relations, needed for the understanding of the behaviour of capacitance in systems with non-uniform thickness, are given in the Appendix.

Studies of anomalous diffusion of impurities in silicon

Abstract: In this paper a study of anomalous diffusion of some group III and group V impurities in silicon is described. Three sets of conditions under which boron and phosphorus diffused anomalously fast were studied. They were ( a ) fast diffusion at high concentration of impurity, ( b ) fast diffusion in a mechanically polished slice and ( c ) the push out effect. These were studied under different conditions of oxidation and the evidence suggests that oxidation causes relief of strain which in turn causes fast diffusion. A further experiment giving direct evidence of fast diffusion during relief of strain in a crystal is described.

Carrier concentration and minority carrier lifetime measurement in semiconductor epitaxial layers by the mos capacitance method

Abstract: A method to determine the carrier concentration and the minority carrier lifetime in semiconductor epitaxial layers is described. This method implies the use of a MOS capacitance realised on the epitaxial layer. The carrier concentration is reached by measurements of maximum and limit values of the capacitance with bias voltage. The minority carrier lifetime is obtained by time constant measurement of the limit capacitance response to a voltage step.

The Hall effect and related phenomena

Abstract: A review is presented of the theory of the Hall effect and related phenomena in solids. Basic principles are illustrated by application of the Lorentz force to moving charges in a free-electron system. Application to a real solid is indicated through a consideration of the effects of band structure and charge-carrier scattering mechanisms. Association is also made with the off-diagonal elements of the conductivity tensor, and the influence of certain symmetries in the medium is discussed. Special mention is made of specific parameters useful in characterizing a material for Hall-effect applications, including the dependence of the parameters on temperature and impurity content. The question of the variation of Hall coefficient with magnetic field is examined in some detail, with particular attention to band structure and crystal anisotropy, scattering, inhomogeneities and multi-band effects. Differentiation is made between isothermal and adiabatic phenomena, and the importance of various thermomagnetic contributions is pointed out. Related galvanomagnetic phenomena which are discussed include magnetoresistance effect and also the magnetic-field dependence of the skin depth in the case of the transmission of a.c. fields through a disk.

Breakdown voltage of planar silicon junctions

Abstract: It is shown that the breakdown voltage of silicon diodes fabricated by the “planar” process is lower than that of corresponding geometrically plane diodes because of the increased electric field intensity in the curved portion of “planar” junctions. Measured breakdown voltages of “planar” silicon diodes are shown to follow Armstrong's theory for cylindrical step p-n junctions over a wide range of variables indicating the absence of significant surface effects on breakdown voltages.

Theory of insulated-gate field-effect transistors near and beyond pinch-off

Abstract: A theoretical analysis is given of the static characteristics of an insulated-gate field-effect transistor comprising two gate electrodes symmetrically located at both sides of a semiconducting channel. Space-charge-limited currents are included in the analysis. The channel is described by means of a single equation which serves as a boundary condition for the electric potential in the insulator region. The characteristics calculated show a finite saturation resistance depending in dimensionless form upon the value of h/L , the ratio of the insulator thickness to the channel length. In the limit of h/L tending to zero the theory yields results already known from a gradual approximation. It is shown how the results obtained can be applied to transistors having only one gate electrode.

Effect of ferroelectric polarization on insulated-gate thin-film transistor parameters

Abstract: The properties of a thin-film transistor deposited upon an oriented, ferroelectric triglycine sulfate (TGS) crystal have been evaluated in terms of the interaction between the remanent spontaneous polarization of the ferroelectric element and the space charge in the semiconductor layer. Experimental data suggests that this interaction results in changing the threshold voltage V0 for the onset of drain current.

Chemically sprayed thin film photovoltaic converters

Abstract: Thin film photovoltaic cells have been prepared using a chemical spray technique for the deposition of the active layers. CdSCu2−xS cells with an active film thickness of 1μ have given efficiencies as high as 4 per cent in areas of 1 cm2. These cells have been produced by the chemical spray deposition of two distinct layers. The first layer is n-type cadmium sulfide and the second layer is p-type copper sulfide of the diginite form. The photovoltaic operation of this type cell is attributed to the formation of a distinct heterojunction between the cadmium sulfide and the copper sulfide. Recently, cadmium sulfide thin film cells have been made with an open circuit voltage as high as 1·04 V with 2 mA/cm2 current density, when illuminated with 100 mW/cm2 of water filtered tungsten light.

High injection theories of the p- n junction in the charge neutrality approximation

Abstract: A survey is presented of the basic equations underlying the transport in p−n junctions and transistors, with particular emphasis on the restrictions under which various approximate relations are valid. The ambipolar aspect of the equations for all injection levels is stressed. The most general recombination processes have been considered and are incorporated in the analysis. Boundary conditions have been derived in terms of the junction voltage and in terms of the externally applied voltage, accounting for the voltage drops in the bulk region. It is shown that the “p−n product method” as applied in the usual way, in which the difference of the quasi-Fermi levels is equated to the junction voltage, is incorrect, and violates normal semiconductor relationships. To derive variational boundary conditions valid for a.c. applications, the complete d.c. expressions as given by F letcher must be considered. The d.c. problem is solved for all injection levels taking into account the decrease in emitter efficiency with applied voltage, the voltage drop in the bulk regions and more rigorous boundary conditions than employed hitherto. The problems associated with an analytic solution to the a.c. admittance of a p−n junction operating under moderately high injection levels are discussed and the impossibility of a solution in terms of known functions is indicated. For high injection, frequency dependent boundary conditions in terms of the applied voltage are derived and a closed form solution for the high frequency admittance is established.

Galvanomagnetic properties of recrystallized dendritic InSb films

Abstract: The galvanomagnetic properties of monophase, dendritic, preferentially oriented InSb films grown from a non-stoichiometric melt containing an excess of Sb, are described. Such films are n-type and have the following properties: a Hall coefficient of the same order of magnitude as that of bulk polycrystalline InSb, an electron mobility which is thickness dependent reaching a value μ e = 4 × 10 4 cm 2 /V-sec in films 3 μm thick, a magnetoresistance which is quadratic in H for μH H for μH > 1, inhomogeneity fluctuations and resistivity striations which lead to geometrical effects larger than those associated with macroscopic length to width ratios of rectangular specimens. The charge carrier density in these films is between 5 × 10 16 electrons/cm 3 and 2 × 10 16 electrons/cm 3 near 300°K. Experimental data suggests that lattice scattering, in combination with dislocation scattering in accordance with the Dexter-Seitz model, accounts for the temperature dependence of the electron mobility above 200°K. Calculated dislocation densities in films are of the order of 10 9 . It is suggested that dislocation scattering represents a significant mobility limiting process in evaporated or recrystallized InSb films.

Photoluminescence and solution growth of gallium arsenide

Abstract: Single crystalline layers of GaAs with thicknesses of the order of 1 mm have been grown on GaAs seed crystals under near equilibrium conditions from a gallium-rich solution at about 800°C with a radial temperature gradient. The photoluminescence spectrum of this material at 77°K differs greatly from that of GaAs grown by other methods. Essentially, no radiative transitions involving deep recombination centres are seen, and the photoluminescence efficiency near the band gap energy is more than twenty-fold that of comparably doped Bridgman or floating-zone crystals.

The photovoltaic response of nGe-nSi heterodiodes☆

Abstract: : The photovoltaic response of the nGe-n Si diodes are in agreement with the I-V characteristics and the band diagram postulated by Oldham and Milnes. (Author)

Preparation of high mobility InSb thin films

Abstract: High mobility thin films of InSb have been prepared by flash evaporation of elemental In and Sb in vacuum and oxidation of the film surface prior to recrystallization in an inert atmosphere. Room temperature mobilities of 50,000 cm2/V-sec. have been achieved using this method.

Exakte lösungen von potentialproblemen beim Halleffekt durch konforme abbildung

Abstract: Zusammenfassung Fur sieben Zwei-, Drei- und Vierpole werden in diesem Aufsatz die Elemente der Widerstandsmatrix als Funktionen geometrischer Parameter und des Hallwinkels exakt bestimmt. Dabei handelt es sich um alle Moglichkeiten, die sich aus der exakt beherrschten Vierecksabbildung nach dem Schwarz-Christoffelschen Abbildungsintegral ergeben.

Electrical properties of BaPbO3 ceramics

Abstract: A new type semiconductor of perovskite structure, BaPbO 3 , was studied. The electrical conduction of BaPbO 3 is metallic and the carrier concentration is ∼ 2 × 10 20 electrons/cm 3 . The type of charge carrier was determined from the sign of the Hall field and thermoelectromotive force. The ESR was observed below solid nitrogen temperature. A broad and asymmetric differential curve appeared clearly at liquid helium temperature. The g -value was 2.057 ± 0.005 and its line width was 141.5 ± 10 G. The electrical properies are compared with those of oxygen-deficient BaTiO 3 semiconductor.