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.
Optical and electrical current gain in an amorphous silicon bulk barrier phototransistor
An amorphous silicon (a-Si) bulk barrier phototransistor was successfully fabricated on a glass substrate. The measured optical gain G and electrical current gain HFEare 196 percent and 11.8, respectively. Estimation and measurement methods for G and HFEare discussed.