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Browse Prior Art Database

GaAs Integrated Circuit Substrates

IP.com Disclosure Number: IPCOM000050757D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Hovel, HJ: AUTHOR [+2]

Abstract

GaAs layers intended for integrated circuits can be improved with an intermediate layer between the integrated circuit device layer and the substrate that accommodates lattice matching and inhibits the effect of a low resistivity substrate adjacent to the device layer.

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GaAs Integrated Circuit Substrates

GaAs layers intended for integrated circuits can be improved with an intermediate layer between the integrated circuit device layer and the substrate that accommodates lattice matching and inhibits the effect of a low resistivity substrate adjacent to the device layer.

Two substrate materials useful for GaAs integrated circuit device layers are semi-insulating GaAs and Ge which have lattice characteristics that are satisfactory. In semi-insulating GaAs, there are impurities, usually Cr, that can diffuse into the device layer. If the GaAs is conducting, the impurity problem is avoided, but both conducting GaAs and Ge are more highly conductive than is desirable for device layer purposes.

Where the substrate is Ge, an intermediate layer involving AlAs, as shown in Figs. 1 and 2, is employed.

In the first, Ge is covered with a thin (0.02-5 Mu) GaAs layer, followed by an insulating AlAs layer, and an upper active GaAs layer.

In the second, the upper GaAs layer may contain a buffer region (low doped) as well as an active region (approx. 10/17/ doped). The AlAs layer thickness is made sufficient to provide the desired insulating effect. The relation between the thickness, resistivity, and resistance is given by R=e/t/ divided by A.

For a device of 100 square microns, a thickness of 1 Mum would be sufficient to provide 10/9/ ohms isolation from the substrate for 10/7/ ohm-cm material. Any energy barriers between the various Dayers prov...