83 Displays 83.1 Light-Emitting Diodes Semiconductor Device Principles. Semiconductor 83.2 Liquid-Crystal Displays Principle of Operation. Interfacing James E Morris 83. 3 The Cathode Ray Tube tate University of New York Monochrome crts· Color Crts· Contrast and Brightness. Measurements on CRTs. Projection Screen Andre martin 83.4 Color Plasma Displays Hughes Display Products troduction. Color Plasma Display Markets.Color Plasma Display Attributes.Gas Discharge Physics. Current Limiting Larry F. Weber Plasma Displays ac Plasma Displays. Color Plasma Display Plasmaco, subsidiary of matsushita Devices.Gray Scale 83.1 Light-Emitting Diodes James e. Morris The light-emitting diode(LED) has found a multitude of roles as the field of optoelectronics has bloomed. Infrared devices are used in conjunction with spectrally matched phototransistors in optoisolation couplers hand-held remote controllers, interruptive, reflective and fiber-optic sensing techniques, etc. Visible spectrum pplications include simple status indicators and dynamic power level bar graphs on a stereo or tape deck. This section will concentrate on digital display applications of visible output devices. Semiconductor Device Principles The operation of an LED is based on the recombination of electrons and holes in a semiconductor. As an electron carrier in the conduction band recombines with a hole in the valence band, it loses energy AE equal to the bandgap E, with the emission of a photon of frequency c/=△E/h (83.1) where n is the radiation wavelength and h is Plancks constant. The incidence of recombination under equilibrium conditions is insufficient for practical applications bu an be enhanced by increasing the minority carrier density. In an LED, this is accomplished by forward biasing the diode, the injected minority carriers recombining with the majority carriers within a few diffusion lengths of the junction edge Figure 83.1 illustrates the process. The potential barrier eV, is reduced by forward bias ev, leading to net forward current and the minority carrier distributions shown on either side of the depletion yer. As the carriers diffuse away from the junction edges, these distributions decay exponentially because of ecombination with the majority carriers. Each recombination event shown on either side of the junction gives off a photon. This process is called injection electroluminescence. c 2000 by CRC Press LLC© 2000 by CRC Press LLC 83 Displays 83.1 Light-Emitting Diodes Semiconductor Device Principles • Semiconductor Materials • Device Efficiency • Interfacing 83.2 Liquid-Crystal Displays Principle of Operation • Interfacing 83.3 The Cathode Ray Tube Monochrome CRTs • Color CRTs • Contrast and Brightness • Measurements on CRTs • Projection Screen 83.4 Color Plasma Displays Introduction • Color Plasma Display Markets • Color Plasma Display Attributes • Gas Discharge Physics • Current Limiting for Plasma Displays • ac Plasma Displays • Color Plasma Display Devices • Gray Scale 83.1 Light-Emitting Diodes James E. Morris The light-emitting diode (LED) has found a multitude of roles as the field of optoelectronics has bloomed. Infrared devices are used in conjunction with spectrally matched phototransistors in optoisolation couplers, hand-held remote controllers, interruptive, reflective and fiber-optic sensing techniques, etc. Visible spectrum applications include simple status indicators and dynamic power level bar graphs on a stereo or tape deck. This section will concentrate on digital display applications of visible output devices. Semiconductor Device Principles The operation of an LED is based on the recombination of electrons and holes in a semiconductor. As an electron carrier in the conduction band recombines with a hole in the valence band, it loses energy DE equal to the bandgap Eg with the emission of a photon of frequency u = c/l = DE/h (83.1) where l is the radiation wavelength and h is Planck’s constant. The incidence of recombination under equilibrium conditions is insufficient for practical applications but can be enhanced by increasing the minority carrier density. In an LED, this is accomplished by forward biasing the diode, the injected minority carriers recombining with the majority carriers within a few diffusion lengths of the junction edge. Figure 83.1 illustrates the process. The potential barrier eVo is reduced by forward bias eV, leading to net forward current and the minority carrier distributions shown on either side of the depletion layer. As the carriers diffuse away from the junction edges, these distributions decay exponentially because of recombination with the majority carriers. Each recombination event shown on either side of the junction gives off a photon. This process is called injection electroluminescence. James E. Morris State University of New York at Binghamton André Martin Hughes Display Products Larry F. Weber Plasmaco, subsidiary of Matsushita