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High Speed Non-volatile Memory Element

IP.com Disclosure Number: IPCOM000050405D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Heiblum, M: AUTHOR [+2]

Abstract

A high speed non-volatile memory element is constructed of semiconductor regions that permit quantum mechanical tunneling into a storage region during writing. The structure is as shown in Fig. 1, wherein the symbol E is used for the emitter and B is used for the base. The GaAs layers are doped, and the AlGaAs layers are undoped.

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High Speed Non-volatile Memory Element

A high speed non-volatile memory element is constructed of semiconductor regions that permit quantum mechanical tunneling into a storage region during writing. The structure is as shown in Fig. 1, wherein the symbol E is used for the emitter and B is used for the base. The GaAs layers are doped, and the AlGaAs layers are undoped.

When the base is biased positively with respect to the emitter, eV(BE)> Phi, electrons will tunnel through the AlGaAs, from the emitter to the base, create a space charge in the base, and diffuse into a base contact. The doping in the emitter is chosen high enough for high current injection, and in the base the doping is low enough to create a space charge, but the doping will still not be too low to enable the forming of an ohmic contact to the base.

When the bias is suddenly removed, the accumulated electrons in the base will stay "without any place to go", except to tunnel through or thermally surmount the barrier Phi, back to the emitter. The backward tunneling probability, however, is greatly reduced, without the application of a negative bias. An estimate of the number of charges which are involved in this process is as follows. The tunneling current can be estimated via (see original) where F=V(BE) /d(BE) is the electric field. If V(BE)=1V, then J approximately equal to
1.3x10/6/a/sq cm. An electron in the base with approximately 1 eV excess energy will have an average velocity (see original) upon entering the base and before encountering a collision. This velocity may be limited by the band structure of GaAs at 1 eV above the conduction band minimum, and the density is expressed as n=J/e v approximately equal to 4.3x10/16/ per cu cm where m*=0.1 m(o) is assu...