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Improvement of Low Temperature Si Transistor Performance

IP.com Disclosure Number: IPCOM000090204D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 16K

Publishing Venue

IBM

Related People

Dumke, WP: AUTHOR

Abstract

In silicon transistors of the NPN type, as the temperature is decreased there is a significant degradation in the high-frequency current gain cutoff and in the DC current gain. This results from the presence of donors in the P-type base region of the transistor acting as minority carrier traps. A donor concentration of between 10/16/cm/-3/ and 10/17/cm/-3/ is sufficient to produce the degradation. The traps are not significant at room temperature. The problem is alleviated by preparing the transistors in such a way to minimize the number of minority carriers in the base. The emitter diffusion is as steep as possible to avoid excessive penetration of minority carriers into the base region. The collector region is prepared using a shorter and steeper out-diffusion of donors from the collector toward the base.

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Improvement of Low Temperature Si Transistor Performance

In silicon transistors of the NPN type, as the temperature is decreased there is a significant degradation in the high-frequency current gain cutoff and in the DC current gain. This results from the presence of donors in the P-type base region of the transistor acting as minority carrier traps. A donor concentration of between 10/16/cm/-3/ and 10/17/cm/-3/ is sufficient to produce the degradation. The traps are not significant at room temperature. The problem is alleviated by preparing the transistors in such a way to minimize the number of minority carriers in the base. The emitter diffusion is as steep as possible to avoid excessive penetration of minority carriers into the base region. The collector region is prepared using a shorter and steeper out-diffusion of donors from the collector toward the base. Where the region to form the base is epitaxially grown, care is taken to obtain pure material having a minimum number of donors.

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