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Edge Supported Ge Thin Films

IP.com Disclosure Number: IPCOM000096564D
Original Publication Date: 1963-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Marinace, JC: AUTHOR

Abstract

Films of Ge can be epitaxially vapor-grown on a GaAs substrate to practically any thickness desired. A layer of etch resist such as Apiezon W can then be applied to the GaAs surface leaving blank areas in the Apiezon W layer where it is desired to have thin film regions of Ge. This is shown in the upper drawing.

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Edge Supported Ge Thin Films

Films of Ge can be epitaxially vapor-grown on a GaAs substrate to practically any thickness desired. A layer of etch resist such as Apiezon W can then be applied to the GaAs surface leaving blank areas in the Apiezon W layer where it is desired to have thin film regions of Ge. This is shown in the upper drawing.

Next, the assembly is placed in an etch that attacks GaAs relatively rapidly and is relatively ineffective against Ge. One such etch is composed of equal parts of NaOH or KOH aqueous solution and 30% H(2)O(2). Some mechanical agitation keeps bubbles from collecting on the etching surfaces. The orientation of the GaAs controls to some extent the shape of the hole to be etched. For example, the slower the etch rate in the direction toward the Ge, the more bulbous the etched hole in the GaAs is. Generally, however, the structure is as shown in the lower left drawing. Hence, the thickness control is maintained simply by controlling the amount of Ge deposited. Moreover, because of the wide difference between the etch rates of GaAs and Ge, it is easier to achieve desired configurations. This method is applicable to any two materials which are epitaxially compatible and which have widely different etch rates in some particular etch.

The lower right drawing shows a high speed transistor structure fabricated by this method. On a substrate of high resistivity (>10/5/ ohm-cm) GaAs, a thin layer of Ge ( approximately 0. 001'' thick) is ep...