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The field in the i-layer of an amorphous-silicon solar cell may be assumed as uniform. We formulate the respective cell model without further approximations in terms of a “regional method”. The i-layer is subdivided for that purpose in many regions, and the regional solutions are chained together. Some exemplary simulations are presented. The model is in particular suited to demonstrate snake-like low-forward-voltage photocharacteristics, to be induced by near-surface excess carrier generation, as with blue illumination. Observed and simulated “blue-snake” characteristics are compared with each other. A snake indicates the transition from a bulk-recombination to a surface-recombination limited current regime.

Semiconductor devices are to be explained by the semiconductor equations and boundary conditions. A device simulation requires the solution of the respective boundary-value problem. Numerical methods have to be applied in general. Solutions over a discretization lattice are conventional. Besides the standard lattice methods an alternative continuum method may be used. A formulation of the continuum method will be presented for the stationary and one-dimensional case. The “local solution” of the linearized equations through the interstitial regions between neighboring lattice sites have to be found first. The external boundary conditions then impose the “global solution”. Iterations overcome the nonlinearities. The numerical continuum description of a device and simple analytical models are formally similar. This feature distinguishes the continuum method from the lattice methods.

The assumption of a uniform field through the i-layer absorber of an a-Si:H pin solar cell seems to be hardly realistic. The analytical models based on this assumption have been nevertheless rather successful. A few calculations will demonstrate this. In connection with suitable experiments the roles of bulk and surface recombination become distinguishable. Spectral response measurements in particular reveal a strong influence of surface recombination, while the reverse dark currents stem from bulk recombination.

We measured the spectral photoconductance of slightly boron doped amorphous germanium (a-Ge:H) films through the wavelength interval from 450 to 950 nm, and determined the products ( μτ ) n of electrons and ( μτ ) p of holes by means of an own two-carrier photoconductance model. The doping was achieved by adding diborane (B 2 H 6 ) to the germane (GeH 4 ) gas in the deposition chamber, in concentrations up to 0.3%. In nominally undoped films the product ( μτ ) n exceeds the product ( μτ ) p by two orders of magnitude. A 150 ppm admixture of diborane yields “compensation”, i.e. adjusts the equation ( μτ ) n = ( μτ ) p = 5*10 −8 cm 2 /V. A pin solar cell with compensated i-layer is more red efficient than a cell with undoped i-layer.

The reversal of the electric field in the i-layer of a pin cell under forward voltage stimulates surface recombination. Reversed fields and surface recombination together yield secondary photocurrents and limit the AM1 open-circuit voltage.

The authors prepared a-Ge:H films with different thicknesses and measured their spectral photoconductivity, which was found to increase with both film thickness and light wavelength. As an explanation, reduced photoconductivity under the illuminated surface is assumed. The eta mu tau -product of a film is given by its photoconductivity measured between ohmic contacts and represents a property of the photoelectrons. A two-layer model ascribes different eta mu tau -products to a front layer of the film and to the rest of it, called the bulk layer. By fitting the two-layer model to the present experiments the authors find a front-layer thickness of 55 nm, a surface eta mu tau -product of 1*10/sup -8/ cm/sup 2//V, and a bulk-layer eta mu tau -product of 5*10/sup -7/ cm/sup 2//V. The effective eta mu tau -product, determined under the assumption of a homogeneous film, approaches the bulk value when both film thickness and light wavelength reach a value of 1 mu m. No light degradation of the a-Ge:H films is found. >

The change of the spectral photocurrent characteristics of amorphous silicon pin solar cells with light induced degradation is compared with the effect of slightly doping the ‘‘i‐layer’’. Both treatments yield similar results. Light stress lets the primary photocurrent, measured with blue light, decrease and the secondary photocurrent, measured with red light, increased. The similar change occurs when a slight n‐doping of the ‘‘i‐layer’’ is replaced by a slight p‐doping. A simple interpretation in terms of unfirom fields and preponderant surface recombination is possible and will be outlined.We additionally resort to numerical similations. Degradation is to be simulated by the introduction of stronger recombination. The crombination rate will be distributed in space. We indeed find that enhanced surface recombination plays the key role in guiding the simulation towards our experiment.

Numerical simulations of dark and AM1 characteristics are discussed. A field reversal supports the photocurrent reversal. The principal source of reversed (secondary) photocurrents is surface recombination, transmitting an electron current to a hole current and vice versa.

An operational amplifier with a settling time nearly independent of the signal amplitude and the capacitive load has been realised in CMOS technology. It uses an additional circuit to inject an extra bias current into the bias circuit of the operational amplifier. This measure substantially increases the slew rate of an operational amplifier for a given quiescent current. It is useful for programmable high-frequency switched-capacitor circuits, because it always yields an optimum performance without any tailoring.

Crystalline silicon (c-Si) and amorphous silicon (a-Si) solar cells represent complementary cell types. The generation of photocarriers takes place in the semiconductor bulk (c-Si cell) or is confined to the barrier layer (a-Si cell). Carrier collection hence relies on diffusion (c-Si cell) or drift (a-Si cell). We explain the different behavior of the two cell types by measuring photocurrent-voltage characteristics. The photocurrent of the a-Si barrier cell changes its sign at a certain transition voltage U T . We find that U T depends slightly on the light wavelength λ but remains invariant with respect to alterations in the light intensity. It is possible to interpret both features in terms of a suitable uniform-field picture for a-Si p-i-n cells. The field through the i layer reverses its sign at the flat-band voltage U F . A vanishing field reveals the small contribution of diffusion to the photocarrier transport. The function U T (λ) stems therefore from diffusion.

At small-area solar cells of amorphous silicon having the structure glass/ SnO2/p(C)in/Ag and containing various doping profiles within the i-layer we measured the spectral response in an annealed state and in a light soaked state. A phosphorus profile shifts the spectral response towards the blue region, causes a weak decrease in efficiency and improves the stability.

An anomalous turn-on behaviour typical for intrinsic magnetodiodes is described. Calculations are made for a Si diode. The Lorentz force pushes the injected carriers towards a sample surface. The increasing surface recombination counteracts injection. Thus the turn-on current initially overshoots. The conditions necessary to observe the effect are discussed. Ein anomales Einschaltverhalten wird beschrieben, das fur eigenleitende Magnetdioden typisch sein sollte. Fur eine Si-Diode werden Rechnungen angestellt. Die Lorentzkraft schiebt die injizierten Trager gegen eine Probenoberflache. Die zunehmende Oberflachenrekombination wirkt der Injektion entgegen. Deshalb steigt der Strom anfanglich uber seinen Endwert hinaus an. Die fur das Zustandekommen des Effekts notwendigen Bedingungen werden diskutiert.

Standard a-Si pin-solar cells were modified by incorporating small amounts of boron or phosphorous into the “i-layer”, thus producing various psn-diodes. The photocurrent Ip of these diodes decreases with increasing voltage U and vanishes at the transition voltage UT, separating primary and secondary photocurrents. The s-layer fine doping amplifies the dispersion UT(λ) and leads to very strong secondary photocurrents. After a degradation procedure under AM1-light the photocurrent behavior is characterized by a decrease in primary photocurrent and transition voltage but an increase in secondary photocurrent.

Double injection of holes and electrons into an ESFI® SOS film is observed. As is common with magnetodiodes the application of transverse magnetic inductions influences the current–voltage characteristics due to the lifetime profile of the charge carriers across the film. From the dependence of the current on the magnetic induction it is possible to deduce the average bulk lifetime and the surface recombination velocity at the silicon–substrate interface as functions of the voltage. The lifetime is found to increase with voltage, while the surface recombination velocity decreases. These deductions reflect the additional increase in double injection over a certain voltage range and the appearance of magnetoconductance versus voltage extrema. Thus by means of the magnetodiode effect the recombination properties of an ESFI® SOS film may be checked. Doppelinjektion von Lochern und Elektronen in eine ESFI®–SOS-Schicht wird beobachtet. Wie bei Magnetdioden ublich beeinflust das Anlegen einer transversalen magnetischen Induktion die Strom-Spannungs-Kennlinien infolge des Lebensdauerprofils der Ladungstrager quer zur Schicht. Aus der Abhangigkeit des Stroms von der magnetischen Induktion lassen sich die mittlere Volumenlebensdauer und die Oberflachenrekombinationsgeschwindigkeit an der Silizium–Substrat-Grenzflache als Funktionen der Spannung entnehmen. Wie sich zeigt nimmt die Lebensdauer mit der Spannung zu, die Oberflachenrekombinationsgeschwindigkeit dagegen ab. Dieser Befund gibt den zusatzlichen Anstieg der Doppelinjektion in einem gewissen Spannungsbereich und das Auftreten von Extrema in den Magnetokonduktanz–Spannungs-Kurven wieder. Demnach kann der Magnetdiodeneffekt als Mittel zur Kontrolle der Rekombinationseigenschaften einer ESFI®–SOS-Schicht dienen.

Research results on a mainly digitally working autofocus system using an optical module without moving parts are presented. The chip was fabricated in a well-established NMOS technology. It contains two linear arrays of 52 photodiodes each and parts of the signal processing necessary to evaluate the appropriate distance zone. Fifteen zones can be resolved between infinity and 1 m. Minimum scene brightness is about 1...4 cd/m/SUP 2/ for daylight type illumination. The total measuring time comprising integration of optically generated charge carriers and signal processing does not exceed 25 ms. These features make the system attractive for low-cost lens shutter cameras.

Starting with a double terminated Chebyshev LC ladder filter, a CCD wave filter has been implemented by using CCD resonators and charge amplifiers as basic building blocks. The bandpass filter which was realized on a test chip has a center frequency of 50 kHz, together with a relative Chebyshev bandwidth of 2.6 percent, 5 dB insertion loss, and more than 60 dB stopband attenuation. Compared to known SC filters, the advantages of the new approach are in extremely low sensitivity of the center frequency which is controlled by an external clock frequency, and a relative bandwidth which does not depend on the center frequency, but is controlled by capacitance ratios. Filter design, some aspects related to implementation, and experimental results are described.

An SCCD has been built in p - epitaxial layer on a p + substrate. Experimental data showed an improvement of more than 10 dB in linearity of the output stage compared with conventional SCCDs. In contrast to an output stage with a charge sensitive amplifier the solution presented does not need more area and is not restricted to a low frequency range.

A hole–electron plasma within a semiconductor layer submitted to crossed electric and magnetic fields is shifted in the direction of the Lorentz force. Lifetime and mobility gradients in this direction then lead to respective variations of average carrier concentration and average mobility. Both the variations change sign with the Lorentz force and induce positive and negative magnetoresistance. The described processes are active in SOS double injection diodes. Ein Loch–Elektron-Plasma in einer Halbleiterschicht, das gekreuzten elektrischen und magnetischen Feldern ausgesetzt ist, wird in Richtung der Lorentzkraft verschoben. Gradienten von Lebensdauer und Beweglichkeit in dieser Richtung fuhren dabei zu Veranderungen der mittleren Tragerkonzentration bzw. der mittleren Beweglichkeit. Beide Veranderungen wechseln ihr Vorzeichen mit der Lorentzkraft und rufen positiven und negativen Magnetowiderstand hervor. Die beschriebenen Vorgange spielen sich in SOS-Doppelinjektionsdioden ab.

The characteristics of a-Si:H nin diodes exhibit space-charge-limited currents (SCLC). A numerical model for these characteristics will be outlined. It expresses the interaction of space charge, drift and diffusion of electrons injected into the i-region and allows to check the often-used drift approximation.

The i-region of pin solar cells on the basis of amorphous silicon provides the carrier collection. The density of (localized) states (DOS) in this region diminishes the electric field, favors recombination and limits the collection efficiency. The low-frequency capacitance of pin diodes is indicative for the DOS. The small-signal capacitance of a pin solar cell is measured in the frequency range 0.1 to 103 Hz for temperatures between 30 and 100 °C at zero de bias. A simple diode model is suggested. It involves the assumption of constant DOS values in the p-, i-, and n-regions. These values are determined by fitting. It is shown that low-level doping of the i-region and illumination stress significantly raise the capacitance and the DOS. Das i-Gebiet von pin-Sonnenzellen aus amorphem Silizium besorgt die Sammlung der Ladungstrager. Die Dichte der (lokalisierten) Zustande (DOS) in diesem Gebiet vermindert das elektrische Feld, begunstigt Rekombination und begrenzt den Sammelwirkungsgrad. Die Niederfrequenz-Kapazitat von pin-Dioden zeigt die DOS an. Die Kleinsignal-Kapazitat einer pin-Sonnenzelle wird im Frequenzbereich 0,1 bis 103 Hz fur Temperaturen zwischen 30 und 100 °C ohne uberlagerte Gleichspannung gemessen. Ein einfaches Diodenmodell wird vorgeschlagen. Es beruht auf der Annahme konstanter DOS-Werte in den p-, i- und n-Gebieten. Diese Werte werden durch Anpassung bestimmt. Es wird gezeigt, das schwache Dotierung des i-Gebiets und Dauerbeleuchtung Kapazitat und DOS deutlich erhohen.

The passive CCD resonator is a recursive CCD building block which is well suited for the realization of high Q bandpass filters. Its realization is compatible with the standard double-poly NMOS technology. Advantages of the new approach are an extremely low sensitivity of the center frequency which is determined by an external clock frequency, a relative bandwidth which does not depend on the center frequency but is controlled by a capacitance ratio, and signal frequencies at least up to some hundred kHz. The analysis, design considerations, and performance results are presented. A loaded Q factor of 30, a maximum stopband attenuation of 26 dB, and a negligible insertion loss in the passband are typical for a single CCD resonator. The maximum overall center frequency deviation /spl Delta/f/f due to fabrication tolerances is proportional to the transfer inefficiency of the CCD and has the value of about 2/spl times/10/SUP -4/.

Experiments and a model calculation of the stationary photoluminescence (PL) in hydrogenated amorphous silicon are presented. The model is based on the concept of geminate recombination and considers the tunneling of the photogenerated carriers from shallow to deep localized states as a process competitive with the radiative recombination. The activation energy of the temperature-dependent PL quantum efficiency is the sum of the electron–hole binding energy and of the trapping energy of one of both the charge carriers. This model allows a complete interpretation of the decrease of PL quantum efficiency, the shift of the PL spectrum towards lower photon energies, and of the increase in the FWHM with rising temperature. The long-wavelength PL (0.8 eV ≦ ħωPL ≦ 1.0 eV) is found to be characteristic of the density of localized midgap states. Experimente und eine Modellrechnung zur stationaren Photolumineszenz (PL) in wasserstoffhaltigem amorphem Silizium werden vorgestellt. Das Modell basiert auf dem Konzept der Paarrekombination und betrachtet das Tunneln der Phototrager aus flachen in tiefe lokalisierte Zustande als Konkurrenzprozes zur strahlenden Rekombination. Die Aktivierungsenergie der temperaturabhangigen PL-Quantenausbeute ist die Summe aus der Elektron–Loch-Bindungsenergie und der Trapenergie von einem der beiden Ladungstrager. Dieses Modell ermoglicht eine vollstandige Interpretation der Abnahme der PL-Quantenausbeute, der Verschiebung des PL-Spektrums zu kleineren Photonenenergien und der Zunahme der Halbwertsbreite mit zunehmender Temperatur. Es wird gezeigt, das die langwellige PL (0,8 eV ≦ ħωPL ≦ 1,0 eV) charakteristisch fur die Dichte der lokalisierten Zustande in Gapmitte ist.

Amorphous‐silicon (a‐Si:H) solar cells have the structure of short p‐i‐n diodes, with an electric field extending through the i layer. The photocurrent is voltage dependent. Primary and secondary photocurrents occur. We modify the diode structure by low‐level doping of the i layer in order to obtain p‐s‐n diodes. The s layer has the type ν or π, i.e., is slightly n or p doped. The transition p‐i‐n→p‐s‐n deforms the associated spectral photocurrent‐voltage characteristics. Certain asymmetries build up. A type transfer of π→ν inverts the symmetry pattern. The reversal of the illumination direction has almost the same effect. Electrons and holes therefore play equivalent roles in p‐s‐n diodes and p‐i‐n solar cells. An elementary photocarrier‐collection model provides a basic understanding of all the observed phenomena.

Effect of amelioration doses of rock powder and rock sand on growth of agricultural plants and on physical characteristics of sandy and clay soil The effect of rock powder to increase the water holding capacity and adsorption degree of sandy soil and the influence of rock sand to augment the aeration and improve the workability of clay soil were tested in pot experiments. Additions of different rock powders (Basalt, Grauwacke, Kuselit, Muschelkalk and Porphyr) from 5 to 20 weight percent to sandy soil increased the field capacity; the increase in values ranged from 12 to 23% as compared to control. An 11% increase in coarse pore volume (< pF 1.8) of clay soil was noticed when 10 weight percent rock sand was mixed in it. The shear strength of clay soil was hardly decreased. In short time tests five different plants reacted mostly positive to rock powders in sandy soil, the degree of reaction being different depending on rock type and amount used whereas in clay soil the reaction was slightly negative. Ten percent weight additions were better than 20 percent. Up to 67% increase in spring barley grain yield was registered in sandy soil with addition of 10 weight percent of different rock powders both at about 40 and 80% field capacity water levels. High N-application i.e., 1600 mg N/7 kg soil caused a depression in yield at control whereas it increased the dry matter yield in treated pots. In clay soil at 80% field capacity an increase in grain yield was registered only in Grauwacke and Basalt treatments, which was off set at high N-level. Porphyr and Kuselit treatments produced yield depressions. Addition of 10 weight percent of rock powders in sandy soil in the first year of experiment reduced the amount of leachate and nitrate leached between 8 to 29% in fallow treatments, but in planted treatments these were dependant on plant type and rock type even showing an increase in one case.

The electrical properties and the degradation behavior of hydrogenated amorphous silicon alloys (a-Si1−x A x : H, with A=C, Ge, B, P) in designs of pin, pip, nin, and MOS structures are investigated by measuring the dark and light I(V) characteristics and the spectral response as well as the space-charge-limited current (SCLC), the time of flight (TOF) of carriers and the field effect (FE). These investigations give an overview of our recent work combined with new results emphasizing the physics of the a-Si:H pin solar cells. We discuss the stabilizing influence on the degradation behavior achieved by profiling the i layers of the pin solar cells with P and B. Two kinds of pin solar cells, namely glass/SnO2/p(C)in/metal and glass/metal/pin/ITO, are investigated and an explanation of their different spectral response behavior is given. SCLC measurements lead to the conclusion that trapping is also involved in the degradation mechanism, as is recombination. TOF experiments on a-Si1−x Ge x : H pin diodes indicate that the incorporation of Ge widens the tail-state distribution below the conduction band. FE measurements showed densities of gap states of about 5×l016cm−3eV−1.

Fraktionierungsversuche ergeben, das Polymethakrylsauremethylester, gelost in Chloroform, beim Abbau mit Ultraschall polymereinheitlicher wird. Dies wird als Beweis fur die mechanische Natur Des Abbaus angesehen. Die Verstarkung des Abbaus durch Kavitation wird als Resonatorwirkung der schwingenden Kavitationsblaschen aufgefast. Die Grunde fur die Anschauung eines hydrodynamischen Zerreibens der Makromolekeln durch Ultraschall werden kurz dargelegt.

Es werden die Eigenschaften dieser Pigmente, die vom hellen Orange bis zum dunkelsten Marron hergestellt werden konnen, besprochen. An Hand von Rontgenaufnahmen wird die wahrscheinliche Struktur diskutiert. Cadmium-Vermilion, a New Class of Pigments Properties of these pigments, varying from light orange till darkest marron, are described. In the light of radiograms, the most probable structure is discussed.

Ein allgemeines Losungsverfahren fur die Boltzmanngleichung wird beschrieben. Bandform und Ubergangswahrscheinlichkeit sind keinen einschrankenden Bedingungen unterworfen. Der Einflus hoherer Potenzen der auseren Krafte wird iterativ berucksichtigt. Die Eigenfunktionen des linearisierten Stosoperators geben eine Darstellung, welche die Behandlung beliebiger Zeiteffekte moglich macht.

Die Spannungen und Verzerrungen der Schrauben- und der geraden Stufenversetzung werden unter Einschlus des Kernbereichs in zweiter elastischer Naherung berechnet. Bei der Thomas-Fermi-Methode wirkt die Grose ΔΘ (Θ Dilatation) als Quellfunktion fur elektrische Raumladungen in Metallen. ΔΘ nimmt nur in der Nahe von Versetzungslinien erhebliche Werte an. Die Schraubenversetzung ist dementsprechend ein elektrischer Linienpol (zweite elastische Naherung) und die Stufenversetzung ein Liniendipol (erste Naherung), dem sich ein Linienpol und ein Linienquadrupol uberlagern (zweite Naherung). Stresses and strains of screw and straight edge dislocations, are calculated in second elastic approximation including the core region. The Thomas-Fermi method yields ΔΘ (Θ = dilatation) as source function for electrical space charges in metals. ΔΘ attains considerable values only in the neighbourhood of dislocation lines. The screw dislocation correspondingly represents an electrical line pole (second elastic approximation), and the edge dislocation a line dipole (first approximation) which is superposed by a line pole and a line quadrupole (second approximation).

A cathode plate with outgrowing spikes may serve as a field emission source for electrons. An estimation is presented for the field concentration according to a regular array of spikes. Spike cathodes have been produced from a semiconductor matrix containing needle-like metallic inclusions by etching-off a matrix layer. The investigation of these cathodes reveals an irregular emission patteren corresponding to the imperfect cathode structure. Nevertheless, the performed experiments together with the theoretical considerations demonstrate the feasibility of spike cathodes. Eine Kathodenplatte mit nadelartigen Auswuchsen kommt als Feldemissionsquelle von Elektronen in Betracht. Die Spitzenwirkung einer regelmasigen Nadelanordnung wird abgeschatzt. Ausgehend von einer Halbleitermatrix mit nadelformigen Metalleinschlussen wurden Nadelgitterkathoden hergestellt, und zwar durch Abatzen einer Matrixschicht. Die Untersuchung dieser Kathoden lies unregelmasiges Emissionsverhalten erkennen, das mit der unvollkommenen Kathodenstruktur zusammenhangt. Trotzdem zeigen die angestellten Experimente zusammen mit den theoretischen Betrachtungen die grundsatzliche Brauchbarkeit von Nadelgitterkathoden.

Short-circuiting of the Dember voltage affects the PEM effect. This is shown by simple phenomenological considerations. Under certain conditions, especially when the recombination due to the contact surfaces is not too strong, the application of Dember short circuits may increase the PEM effect. This is demonstrated by calculated values for intrinsic samples of InSb at room temperature. Kurzschliesen der Demberspannung beeinflust den PEM-Effect. Das zeigen einfache phanomenologische Uberlegungen. Unter bestimmten Bedingungen, insbesondere wenn sich die rekombinierende Wirkung der Kontaktstellen nicht zu sehr bemerkbar macht, kann der Einbau von Demberkurzschlussen den PEM-Effekt vergrosern. Das wird an Hand von Rechenwerten fur eigenleitende InSb-Proben bei Raumtemperatur gezeigt.

Im kubisch flachenzentrierten Gitter gibt es 7 atomare Kopplungsparameter 3. Ordnung, wenn die entsprechende Wechselwirkung nur zwischen nachsten Nachbarn angenommen wird. Der Zusammenhang zwischen diesen Parametern und den 6 elastischen Konstanten 3. Ordnung wird angegeben. Assuming only nearest neighbour interaction in face-centered cubic lattices seven atomic force constants of third order have to be taken into account. An expression is derived for the relation between these force constants and the six elastic constants of third order.

Die Kontinuumstheorie der Versetzungen gibt ein Modell fur den Versetzungskern. Die zugehorigen Spannungen der Schrauben- und der geraden Stufenversetzung werden berechnet. Nach der Thomas-Fermi-Naherung fur Metalle ruft die elastische Inkompatibilitat im Stufenversetzungskern dort eine unabgeschirmte dipolformige elektrische Raumladung hervor. Die Auswirkung der Potentialverhaltnisse im Kernbereich auf den elektrischen Widerstand der Stufenversetzung in Kupfer wird untersucht. The continuum theory of dislocations gives a model for the dislocations core. Expressions are derived for the stresses of screw dislocations and straight-lined edge dislocations. The elastic incompatibility in the of edge dislocations produces there an unshielded dipole-like electrical space charge. This result is obtained from the Thomas-Fermi-approximation for metals. The electrical resistance of the edge dislocation is investigated for copper with respect to the potential distribution in the core.

Taking into account the thermally generated minority carriers to determine the background charge level along a SCCD, a measurement technique is described to obtain an effective fast interface state density N/SUB SSeff/. Compared to other SCCD specific methods the authors achieve better accuracy. The measurement technique is simple to apply and is useful to determine very small values of N/SUB SSeff/.

The results of measurements performed on an amorphous-silicon thin-film transistor structure are presented and interpreted. The device characteristics show a continuous alternation between n-channel and p-channel operation, an “ambipolar” effect that is made possible by the provision of ohmic source and drain contacts.

Diodes with an nin structure consisting of hydrogenated amorphous silicon ( a -Si:H) exhibit space-charge-limited currents. We subjected some diodes to both illumination and voltage stresses. Only the illumination treatment led to a degradation of the I(U) -characteristics. The degradation is reversible by annealing. We deduce from these findings that metastable traps are created by recombining photocarriers rather than by single-carrier trapping. The reversible diode degradation is consistent with the Staebler-Wronski effect.

An ambipolar FET can be operated alternatively in n-channel and p-channel modes. A simple conceptual model is proposed. It considers ohmic source and drain contacts, a gradual channel, and the depletion approximation.

The impurity profiles obtained by ion implantation may be seriously affected by simultaneous sputtering. Saturation conditions are easily achievable in the case of sufficient sputtering yield. A numerical study is made on the basis of a previous model using a simple penetration distribution function. The accordance with experimental results is promising. (auth)

A monolithic Chebyshev CCD wave filter with a center frequency of f o = 50kHz and a relative bandwidth of 4.2%, 5dB insertion loss and 60dB stopband attentuation will be described.