H. De Smet

A versatile micropower high-voltage flat-panel display driver in a 100-V 0.7-/spl mu/m CMOS intelligent interface technology

A versatile architecture for monolithic low-power high-voltage flat-panel display drivers is presented. A prototype of such a driver chip was designed and fabricated in the 100-V 0.7-/spl mu/m CMOS intelligent interface technology (I/sup 2/T) of Alcatel MicroElectronics. It features 100-V output driving capability, while the operation of the entire driver chip is controlled by means of 3- to 5-V digital signals. Special high-voltage level-shifter circuits, based on the dynamic charge control concept, were developed to reduce the internal power consumption of the driver chip to extremely low values of 1 to 2 /spl mu/W per driver output. A powerful on-chip control unit supports numerous display addressing schemes and very complex multilevel output waveforms can be synthesized. These attractive electrical characteristics, together with the pronounced flexibility and multifunctionality, make this driver architecture ideally suited for a variety of flat-panel displays, especially in battery-powered applications.

2-MHz clocked LCD drivers on glass

A poly-CdSe thin-film transistor (TFT) liquid crystal display (LCD) driver circuit which is integrated on the display itself, reducing the interconnections to the display, is described. The circuit can be used to drive the rows as well as the columns of active and passive matrix LCDs. Drivers made in a 25- mu m technology operate at frequencies up to 2 MHz. Simulations indicate a maximum operating frequency of 8 MHz for a 12.5- mu m technology. By using a time-multiplexing addressing scheme, gray scales can be obtained. In order to address high-resolution displays with gray scales, parallel operating drivers can be used, requiring only one extra connection per parallel driver. >

Design and Wrinkling Behavior of a Contact Lens With an Integrated Liquid Crystal Light Modulator

A new design of a spherically molded liquid crystal cell intended for embedding in a contact lens is proposed. Wrinkle formation in these cells was investigated and a correlation was found between the total thickness of the cell and its smoothness. Smooth cells with minimal thickness were obtained by using an asymmetric configuration with a thin layer at the convex side and a thicker but threshold dependent layer at the concave side. Active liquid crystal cells filled with a guest-host liquid crystal mixture exhibited uniform light modulation along their surface, paving the way towards a modulation-based contact lens display.

Low-power high-voltage CMOS level-shifters for liquid crystal display drivers

An original CMOS level-shifter architecture with high-voltage driving capability and extremely low power consumption is presented. Simulations indicate that an adequate dynamic control of the charge on the gate electrodes of the high-voltage output transistors allows reliable level-shifter operation, even at very low data refresh rates, without the continuous power dissipation found in conventional CMOS level-shifter architectures. Therefore, the CMOS level-shifters presented in this paper are perfectly suited for the monolithic integration of high-voltage display driver circuits in battery-powered applications.

Evaluation of a 64 x 64 CdSe TFT addressed ACTFEL display demonstrator

An operating ACTFEL (AC thin-film electroluminescent display), addressed with TFTs, has been demonstrated. To achieve this, the authors used self-healing electrodes, limited the power supplied to the display, and used a stepped annealing cycle for the TFTs. The display could be driven with 10-V external drivers at a frame rate of 50 Hz and an EL driving frequency of 100 Hz.<<ETX>>

VAN LCOS Microdisplays: A Decade of Technological Evolution

Microdisplays of the liquid crystals on silicon (LCOS) type have gone through a rapid evolution during the last decade. We present an overview of how vertically aligned nematic (VAN) LCOS have evolved from an attractive, but notoriously difficult and even infamous technology, to the mainstream microdisplay technology that it is today. At the same time, we highlight a number of remaining issues and concerns, and present some ideas of how to remedy them.

CdSe-based thin-film integrated optical sensors

Abstract A fabrication method for photoconductive CdSe films, together with a photolithographic process is presented. Two types of films were realized. The first type has a low resistivity (102 Ω cm), a moderate sensitivity and is semi-transparent. The second type of film has a high resistivity (108 Ω cm) and is very sensitive. It is shown that the films meet the requirements of two applications: a luminance sensor and a linear image sensor.

High-voltage CdSe-Ge TFT driver circuits for passive AC-TFEL displays

Since an electroluminescent display (ELD) is a capacitive display driven at high voltage, it is necessary to fabricate high-voltage, large-current drivers. It is shown that a 20-/spl mu/m complementary CdSe-Ge thin-film transistor technology can be used to integrate the high-voltage section of the drive circuits on the substrate of an ELD. The realized column driver levels a 15 V CMOS signal up to a modulation voltage of 50 V. A novel tristate row driver circuit, which is based on the symmetric character of the thin-film transistor, handles row selecting voltages of about 200 V together with current pulses of approximately 100 mA. In this paper, the design, simulation, and measurement of these circuits are described. Technology problems due to high voltages were solved.

Thin Film Cadmium Selenide Technology in Large Area Active Matrix High Resolution Displays

This paper considers the acceptability of an active matrix technology based on thin film polycrystalline CdSe for the industrial manufacture of large area high pixel density active matrix flat panel displays.

The influence of low copper doping concentrations on the recrystallization process in and the electrical properties of germanium in Ge:Cu thin film transistors

Abstract The electrical properties of copper-doped germanium (Ge:Cu) thin films were investigated as a function of the copper concentration and the annealing temperature. Measurements of the sheet resistance indicated that copper concentrations as low as 0.1 at.% still have a significant influence on the recrystallization process in germanium. This was also demonstrated by experimental data on the effective field effect hole mobility. These results are explained on the basis of a “grain path model”. From measurements of the threshold voltage of Ge:Cu thin film transistors, we found that oxygen, incorporated in the grain boundaries of the recrystallized Ge:Cu thin films, has a pronounced impact on the field effect in these films. An accurate control of the oxygen content in the Ge:Cu films even allows us to optimize the electrical parameters of our Ge:Cu thin film transistors.