The hetrojunction amorphous n+(a-Si)/n-i-p(a-SiC)/i-n+(a-Si) phototransistor with high gain (&#8764;40) and high speed (&#8764;10&#181;s)
In this report, a hetrojunction amorphous Si-SiC barrier transistor (a-HJBT) was successfully fabricated which revealed high gain (∼40) and high speed (∼10µs). The homojunction amorphous silicon bulk barrier phototransistor has been reported to be a high gain (∼12) and high speed (∼30µs) photosensing device. In this report, a significant improvement has been achieved by making a hetrojunction structure between the emitter and the base by a structure of n<sup>+</sup>(Si)/n-i-δp<sup>+</sup>(SiC) which is in contact with the i-n<sup>+</sup>(Si) collector layers. The structure was successfully made by plasma enhanced chemical vapor deposition (PECVD) on a glass substrate.
Amorphous Si/SiC phototransistors and avalanche photodiodes
The device structures, operation principles, optoelectronic characteristics, performance comparisons, and possible applications for various a-Si:H/a-SiC:H phototransistors and avalanche photodiodes are reviewed. Although these devices are made of amorphous semiconductors, its majority-carrier transport properties can tactfully avoid gap-state and defect related minority-carrier transport problems, and obtain good performances. Also, each of these devices has the distinct advantage of meeting the requirements of different practical applications. The unique and distinct advantages of these a-Si:H/a-SiC:H devices are first, a variety of peak response wavelengths are achievable by changing the composition or the well-to-barrier widths of the superlattice, secondly, a large-area-detector image sensor can be made on a glass substrate; and thirdly, the low-temperature of the amorphous films (~250°C) possesses a very abrupt composition change and a doping profile, which are impossible in the single-crystalline semiconductors.
Influence of electric fields on friction electrification between metals and borosilicate glass
Abstract In a cylindrical geometry, electric fields were applied through the entire contact area between the sliding metal and the glass surface. The maximum electric charges developed on the metal were measured and plotted against the applied voltage producing the field. The metals were high-purity nickel and gold. The borosilicate glass was Pyrex, brand 7740. The experiments with nickel, which has a work function greater than that of the glass, were performed in 10 −7 mm Hg vacuum. The experiments with gold, with a work function smaller than that of glass, were carried out in air at atmospheric pressure. The results show that: 1. 1) There is both asymmetry and a reversed slope portion in the charge vs. voltage plot. 2. 2) For a certain range of reversing fields, the electric charge developed on the nickel is always negative and the charge on gold is always positive.