U.S. Philips Corporation

Koninklijke Philips Corporation N.V.

St-ericsson Sa

Koninklijke Phillips Electronics N.v.

John M Shannon

Alan G Knapp

Stanley D Brotherton

Steven Charles Deane

Nigel David Young

David Andrew Fish

Neil C Bird

Ian D French

Stephen J Battersby

Jeremy N Sandoe

Julian Robert Beale

John Ernest Ralph

Martin John Edwards

Karel E Kuijk

Gerardus G Van Gorkom

Arthur M Hoeberechts

Jason Roderick Hector

Cornelis Van Berkel

David J Coe

John A Slatter

Carl Glasse

Pieter Schagen

Jeffrey J Harris

Oliver S Davies

Alexander D Annis

Michael Colin Hemings

Darren T Murley

Sembukuttiarachilage R Silva

Edmund G Gerstner

Marek Szubert

Stephen J Mundy

John M Woodcock

A transistor control circuit () comprises a source-gated thin film transistor (), an input for receiving a drive voltage representing a desired control of the source-gated transistor and a current source () for causing a known current to pass through the source-gated transistor (). A first capacitor () stores a resulting gate-source voltage of the source-gated transistor when the known current is passed through the source-gated transistor. The drive voltage is modified using the resulting gate-source voltage, and the modified voltage is used in the control of the source-gated transistor. This control can provide a translational shift in the operating characteristics of the transistor, and it has been found that this can compensate for ageing of the transistor, for non-uniformity between different devices, and for temperature variations.

Transistor control circuits and control methods, and active matrix display devices using the same

A photo transistor has an active region spaced from a source by barrier. A drain is laterally spaced from the active region. Light incident on the active region creates electron-hole pairs. Holes accumulate at the barrier and modulate the effective barrier height to electrons. A gate reset voltage then is applied to gate which lower the barrier allowing the holes to escape.

Phototransistor with source layer between barrier layer and photosensitive semiconductor layer

A transistor has a source electrode () on the opposite side of a semiconductor body layer () to a gate electrode () insulated from the body layer () by gate insulator (). The source electrode () has a potential barrier to the semiconductor body layer (), for example a Schottky barrier. At least one drain electrode () is also connected to the semiconductor body layer (). A suitable source-drain voltage and gate voltage depletes the region of the semiconductor body layer adjacent to the source electrode (), and then source-drain current is controlled by the gate voltage.

Field effect transistor

Phototransistor with source layer between barrier layer and photosensitive semiconductor layer and a gate layer for controlling the barrier height of the barrier layer

A method of making a source-gated transistor is described, in which a gate () is provided on substrate () followed by gate insulator () and semiconductor layer (). The layer is patterned to align the source with the gate () using photoresist () and back illumination through the substrate () with the gate () acting as a mask. The distance between source and drain may also be self-aligned using a spacer technique.

Transistor manufacture

In an active matrix display, each pixel has a storage capacitor for storing a voltage to be used for addressing a drive transistor. A discharge transistor is provided for discharging the storage capacitor thereby to switch off the drive transistor. The timing of this is controlled by a light-dependent device which is illuminated by the display element. The drive transistor is controlled to provide a constant light output from the display element, and the duration is controlled in dependence on the data voltage. Optical feedback is used to alter further the timing of operation of the discharge transistor to provide ageing compensation of the display element and compensation for changes in the drive transistor.

Light emissive active matrix display devices with optical feedback effective on the timing, to counteract ageing

A color display device based on dielectrophoresis is described. The device includes a dielectrophoretic mixture comprising semi-insulating particles of each of the subtractive primary colors cyan (), magenta () and yellow () in a semi-insulating liquid (). The dielectrophoretic frequency characteristics of the particles are the same or similar for particles of the same color but different between the three colors. In particular, the transition frequency (f) is different for each color, or two colors may have the same transition frequency (f) if one has a reversed sense dielectrophoretic frequency characteristic. Also the speeds of the particles are the same for particles of the same color but different between the three colors. The pixels are driven with alternating voltages of different frequencies (f, f, f, f) and duration determined such that different proportions of the different colors of particles are moved, dependent upon their transition frequencies and speeds. A reflective, saturated full color display device may thereby be provided.

Color display device

A matrix display has pixels each including a programmable memory element arranged in parallel across capacitance . The voltage on the capacitance controls a display element . The arrangement can be run in a normal mode, with all of the memory elements in a high resistance state so that the matrix display can be driven dynamically. Alternatively, in a static (low power) mode of operation, the memory elements are programmed with a static image which may be displayed without driving the data lines

Matrix display

A matrix array display device has an array of pixels on a substrate which each have a display element, such as an electroluminescent display element. An associated control circuit including a storage capacitor and a light sensing element are connected thereto for regulating charge stored on the capacitor and responsive, for example, to light emitted from the display element so as to regulate operation of the display element. The light sensing elements include thin film semiconductor devices each having a strip of semiconductor material with laterally-spaced, doped, contact regions and the associated storage capacitor is formed by a conductive layer extending substantially transversely of the strip over one contact region with intervening dielectric material. A predetermined relationship between the storage capacitor and photosensitive device characteristics is then ensured even though dimensional variations in component layers may occur due to manufacturing tolerances. Alternatively, the conductive layer may be provided at the side of the strip opposite the gate and used also as a shield for ambient light.

Matrix array display devices with light sensing elements and associated storage capacitors

An active matrix electroluminescent display device in which the drive current through an electroluminescent display element ( ) in each pixel ( ) in a drive period is controlled by a driving device ( ) based on a drive signal applied during a preceding address period and stored as a voltage on an associated storage capacitor ( ). In order to counteract the effects of display element ageing, through which the light output for a given drive signal level diminishes over time, the pixel includes electro-optic discharging means ( ) coupled to the storage capacitor and responsive to the display element's light output to leak stored charge and to control the integrated light output of the display element in the drive period. For improved control, the discharging means is arranged to rapidly discharge the capacitor at a controlled point in the drive period, upon the drive of the display element falling to a low level. A photoresponsive transistor can conveniently be utilised for this purpose.

Active matrix electroluminescent display device

A display device has an array of pixels comprising light emitting display elements, for example EL elements, carried on a substrate and associated light sensing elements responsive to light emitted by the display elements. The light sensing elements each comprise a gated photosensitive thin film device such as a TFT structure or a lateral gated pin device having a semiconductor layer with contact regions laterally spaced on the substrate and separated by a gate controlled region. A part of the associated display element extends over the gate controlled region with an electrode of the display element serving as the gate of the photosensitive device thereby ensuring good optical coupling between the display element and the photosensitive device and enabling the gate to be appropriately biased. Such an arrangement enables, for example, the provision of electro-optic feedback control in the pixel in comparatively simple manner.

Light-emitting matrix array display devices with light sensing elements

A thin film capacitor is provided with a thin film protection element to protect the capacitor from damage that can result due to the occurrence of an electrostatic discharge event. The thin film capacitor includes two conductive film portions forming capacitor plates and a dielectric film forming the capacitor dielectric. The protection element may take the form of a thin film diode or a series of thin film diodes connected electrically in parallel with the thin film capacitor. The whole device can be fabricated using a stoichiometric silicon nitride layer to produce the capacitor dielectric and a non-stoichiometric silicon rich silicon nitride layer to provide the diode semiconductor material. One diode is formed by one capacitor plate, the semiconductor layer and an upper diode contact. In an alternative construction the protection element takes the form of a narrow gap defined by one conductive film portion electrically connected to one capacitor plate and another conductive film portion electrically connected to the other capacitor plate. During an electrostatic discharge event charge is able to cross the narrow gap rather than pass through the capacitor dielectric material.

Thin film capacitor element

A semiconductor memory device using silicon-rich amorphous silicon alloy material memory elements that are electrically programmable by means of current induced conductivity comprises a layer (,) of the alloy material on opposing sides of which sets of input and output contacts (,) are provided, and discrete conductive elements (,) within the layer which serve as nodes and define programmable conductive paths between input and output contacts to create a three dimensional memory network. The conductive elements can be arranged at one or more levels within the thickness of the alloy layer and preferably are of defined shape forming a predetermined 2D array at each level.

Multiple memory element semiconductor memory devices

A thin film transistor (10) in an electronic device such as an active matrix display panel having an intrinsic amorphous silicon semiconductor layer (22) providing a channel region (23) between source and drain electrodes (14, 16) includes directly adjacent to the side of the semiconductor layer (22) remote from the gate electrode (25) at the channel region (23) a layer (20) of amorphous semiconductor material which has a high defect density and low conductivity that serves to provide recombination centres for photogenerated carriers. Leakage problems due to the photoconductive properties of the intrinsic semiconductor material are then reduced. Conveniently, an hydrogenated silicon rich amorphous silicon alloy (e.g. nitride etc) can be used for the recombination centre layer (20).

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John M Shannon