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Forming of Low Resistance Ohmic Contacts to III-V Semiconductors

IP.com Disclosure Number: IPCOM000037270D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Sadana, DK: AUTHOR

Abstract

A technique is described whereby low resistance ohmic contacts are formed for III-V semiconductor devices. Described is the deposition of an elemental semiconductor over a III-V substrate, followed by ion implantation and annealing, to attain the low resistance ohmic contacts.

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Forming of Low Resistance Ohmic Contacts to III-V Semiconductors

A technique is described whereby low resistance ohmic contacts are formed for III-V semiconductor devices. Described is the deposition of an elemental semiconductor over a III-V substrate, followed by ion implantation and annealing, to attain the low resistance ohmic contacts.

The choice of the elemental semiconductor is crucial. The lattice parameter and crystal structure of the deposited element must be compatible with those deposited elements of the III-V. For example, for a GaAs substrate, Ge is an ideal choice, whereas Si is an ideal choice for a GaP substrate. Both Ge and Si have a diamond cubic structure and their lattice parameters match closely with those of GaAs and GaP, respectively.

The deposition of Ge or Si can either be achieved by vacuum evaporation or sputtering, or epitaxially by MBE or MOCVD etc. To make contacts on n-type substrates, a Vth group element, such as As+, is implanted through Ge into GaAs. A part of the As distribution is contained within the Ge layer, whereas the remaining part extends into the III-V substrate. Therefore, Ge can be recoiled by As into the substrate, as shown in Fig. 1a.

This technique allows simultaneous n-type doping of Ge as well as the III-V substrate. Furthermore, if Ge becomes amorphous due to a high dose (>1e15 cm-2) As+ implantation, it can be converted back to a single crystal by means of solid phase epitaxy on GaAs upon subsequent annealing....