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High Speed Planar Junction Transistors

IP.com Disclosure Number: IPCOM000094359D
Original Publication Date: 1966-Sep-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Kennedy, DP: AUTHOR

Abstract

Mobile charge storage, holes and electrons, is of fundamental importance to both the switching and the high-frequency operation of a junction transistor. Devices containing a large quantity of stored charge exhibit a relatively slow switching speed. For a conventional planar transistor as shown in drawing A, it is known mathematically that a large storage charge exists near its emitter junction periphery at region A-A'. Under the diffusion mask opening, the emitter and collector junction are separated by the transistor base width. For this reason a relatively small number of charge carriers is stored within the base region of this conventional planar transistor. I contrast, at the emitter periphery A-A', the distribution of charge carriers is governed by basically its minority carrier diffusion length.

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High Speed Planar Junction Transistors

Mobile charge storage, holes and electrons, is of fundamental importance to both the switching and the high-frequency operation of a junction transistor. Devices containing a large quantity of stored charge exhibit a relatively slow switching speed. For a conventional planar transistor as shown in drawing A, it is known mathematically that a large storage charge exists near its emitter junction periphery at region A-A'. Under the diffusion mask opening, the emitter and collector junction are separated by the transistor base width. For this reason a relatively small number of charge carriers is stored within the base region of this conventional planar transistor. I contrast, at the emitter periphery A-A', the distribution of charge carriers is governed by basically its minority carrier diffusion length. An analysis of this peripheral emitter region shows it to contribute a stored charge per unit area of one to two orders greater than the region directly under the diffusion mask opening.

Higher speed operation results from any geometrical modification that either reduces or eliminates stored charge at the emitter junction periphery. Drawings B and C show two of the several ways in which this result can be accomplished. Drawing B illustrates a structure in which almost the entire emitter junction is enclosed by the collector junction. The close proximity of the collector junction substantially reduces the stored charge near the...