Chushiro Kusano

Single-Tube Color Imager Using Hydrogenated Amorphous Silicon

Reactively sputtered hydrogenated amorphous silicon film is used as the photoconductive target of a vidicon type image pickup tube. It is indicated that hydrogen partial pressure in the discharge gas has to be 40% or more in order to attain suitable image pickup tube characteristics. Photo-electric properties and lag-characteristics are enormously improved by lightly doping boron into amorphous silicon film, and a blocking type target structure is effective for suppressing dark current of the pickup tube. Using doped amorphous silicon film with a color-filter-integrated face plate, a single-tube color imager is fabricated.

Amorphous Silicon Image Pickup Devices

Reactively sputtered amorphous silicon film is used as a photoconductive target of the vidicon type image pickup tube. Variation of tube characteristics with the hydrogen partial pressure in the discharge gas during sputtering are investigated. The results indicate that hydrogenated amorphous silicon films prepared in hydrogen partial pressures of 1~2×10-3 Torr are suitable for image pickup tubes. This amorphous silicon vidicon has several excellent characteristics: better sensitivity of about twice that of the conventional tubes, high resolution, little after-image, and no blooming.

Simulation of the Effect of Emitter Doping on the Delay Time in AlGaAs/GaAs Heterojunction Bipolar Transistors

The influence of the emitter doping level (5×1017-5×1018 cm-3) on the delay time in AlGaAs/GaAs heterojunction bipolar transistors is investigated using numerical simulation based on a drift-diffusion model. The results reveal that the emitter delay time (τE) decreases with higher emitter doping (5×1018 cm-3), allowing a very short delay time ( 104 A/cm2).