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AlGaAs-GaAs HETEROJUNCTION MESFET WITH SELF-ALIGNED GATE

IP.com Disclosure Number: IPCOM000060527D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Codella, CF: AUTHOR

Abstract

In semiconductor manufacturing technology, the heterojunction, modulation-doped AlGaAs-GaAs MESFET (metallized semiconductor field-effect transistor) shows promise as high speed logic devices because of the very high electron mobility in the channel. There have been high series resistance effects associated with these which degrade performance. This article proposes a way to alleviate this problem by obtaining a self-aligned gate requiring no implant/anneal. Fig. 1 illustrates the device with the layers being a semi-insulating substrate 6, an undoped GaAs 9, an undoped AlGaAs 8 and an N+ AlGaAs 7. A persistent drawback has been the high series resistance 3 associated with the source/drain regions and ohmic contact 2. The contact resistance is at 4, the heterojunction at 5, and the metal gate is shown as 1.

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AlGaAs-GaAs HETEROJUNCTION MESFET WITH SELF-ALIGNED GATE

In semiconductor manufacturing technology, the heterojunction, modulation- doped AlGaAs-GaAs MESFET (metallized semiconductor field-effect transistor) shows promise as high speed logic devices because of the very high electron mobility in the channel. There have been high series resistance effects associated with these which degrade performance. This article proposes a way to alleviate this problem by obtaining a self-aligned gate requiring no implant/anneal. Fig. 1 illustrates the device with the layers being a semi- insulating substrate 6, an undoped GaAs 9, an undoped AlGaAs 8 and an N+ AlGaAs 7. A persistent drawback has been the high series resistance 3 associated with the source/drain regions and ohmic contact 2. The contact resistance is at 4, the heterojunction at 5, and the metal gate is shown as 1. One approach to the problem has been to use the metal gate to block an N+ source/drain implant 10 forming a self-aligned gate and channel 11 flanked by N+ source/drain regions (Fig. 2). This greatly reduces both the ohmic contact resistance and the source/drain series resistances. However, these devices have extremely sharp heterojunctions formed by MBE (molecular beam epitaxy) which must retain their abruptness for the device to function properly. This makes the implanted source/drain impractical since the required post-implant anneal would destroy the heterojunction. The invention proposes using selec...