Browse Prior Art Database

Semiconductor Memory Device

IP.com Disclosure Number: IPCOM000062336D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Wordeman, MR: AUTHOR

Abstract

This article relates generally to storage devices and, more particularly, to cryogenic bistable devices. A bistable field-effect transistor memory element can have two stable states, one conductive and one resistive, when using the phenomenon of impurity freeze-out. The device state is altered electrically and read out non-destructively. Measurements of free carrier concentration as a function of temperature and doping have shown that activation energy for impurity ionization is reduced for high impurity concentrations. Lanyon [*] suggests that the effect may be due to the screening effects of donor- electron interactions.

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Semiconductor Memory Device

This article relates generally to storage devices and, more particularly, to cryogenic bistable devices. A bistable field-effect transistor memory element can have two stable states, one conductive and one resistive, when using the phenomenon of impurity freeze-out. The device state is altered electrically and read out non-destructively. Measurements of free carrier concentration as a function of temperature and doping have shown that activation energy for impurity ionization is reduced for high impurity concentrations. Lanyon [*] suggests that the effect may be due to the screening effects of donor- electron interactions. Bistability appears to result for activation energy dependent on carrier concentrations in semiconductor regions of moderately high impurity at other than zero net charge, such as in arsenic-doped samples of concentrations greater than 2x1018cm-3 at 77OEK. Fig. 1 depicts the fraction of arsenic impurities ionized as a function of electron concentration using the Lanyon model. The dashed line shows a constant charge density of 4E17 with a donor density of 4E18. Intersections show possible steady-state solutions. Although three intersections exist, the highest and lowest electron concentration solutions are stable, while the central point is unstable. This behavior occurs in finite regions of non-zero space charge and must be accompanied by an electric field at the region boundary. If a thin layer, doped as above, is p...