Low-Power, Full-Color Display Panels Based on Thin-Film Electroluminescent Devices and Porous Polysilicon Light Emitters

Spire proposes to demonstrate visible electroluminescent (EL) devices fabricated on porous polysilicon thin films on glass substrates which can operate at an applied bias of only a few volts. In Phase II, a working matrix of red, green, and blue (RGB) EL devices for a full-color display panel will be developed. Spire recently fabricated the first Si-based light-emitting diodes configured as heterojunctions between an electrochemically-processed p-type porous Si and an n-type transparent semiconductor (indium-tin-oxide). Quantum confinement in Si nanostructures is the key to the luminescence of these devices. These LEDs emit yellow, orange, and red light: The fabrication of a porous Si-based blue LED is presently being investigated at Spire with government funding. Although most previous work on porous silicon devices has employed bulk Si materials rather than Si thin films, Spire has shown that bright visible light can be obtained from porous structures formed on polycrystalline silicon thin films deposited on quartz substrates. Spire now proposes to extend this development to create a novel thin film electroluminescent (TFEL) technology based on porous polysilicon films. Such a technology would be not only more economical and practical than conventional practice, but could also offer the monolithic integration of display elements with the thin film transistor (TFT) chip-on-glass driver circuits.