| 摘要 |
1501962 Photosensitive semi - conductor devices INTERNATIONAL BUSINESS MACHINES CORP 5 May 1975 [24 June 1974] 18673/75 Heading H1K A space-charge-limited phototransistor structure comprises lateral emitter, base and collector regions 8, 6, 5 at the surface of a semi-conductor substrate 2 of resistivity at least 10,000 ohm-cm. beneath which, along line B, a space-charge limited current flows between the emitter and collector when the surface base area receives incident radiant energy. More electron-hole separation occurs in region B than in the base region 6, the depth of the base region being less than the reciprocal of the absorption coefficient of the radiant energy. In the integrated circuit shown, adjacent transistors are isolated by a region of opposite type to that of the substrate reverse biased with respect to the collector regions. The base region is at floating potential and when the base surface is illuminated, the collector, which is reverse biased, collects electrons from the pairs generated in both the P base and lower N regions. The remaining holes tend to forward-bias the emitter-base junctions along lines A and B to initiate phototransistor action. Metal shields (40) (Fig. 4, not shown) may be placed over the isolation region and the effective base area may be increased, whilst maintaining the required base width, by extending the collectorbase junction along certain portions only (Figs. 2, 3, not shown). An array of such phototransistors (Fig. 5, not shown) may be used in a document reading scanner.
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