Indium wafer substrate

A practical unit of detector is composed of a silicon wafer, an indium foil of 0.5 mm thick and a substrate of machinable glass. The indium foil makes electric contact with the aluminum layer on the wafer. The dimensions of the wafers and the substrates are as follows ... 

Consider the polymer-on-metal interface, which might be prepared by coating a thin metal film with polymer in a polymer-based LED. The case of the counter electrode, formed by vapor-deposition, is discussed subsequently. First, assume that the substrates have clean surfaces hydrocarbon and oxide free, or naturally oxidized but still hydrocarbon free (pointed out as necessary). Typically, in connection with polymer-based LEDs, the metallic substrate could be gold, ITO (indium tin oxide) coated glass, the clean natural oxide of aluminum ( 20 A in thickness), the natural oxide which forms upon freshly etched Si( 110) wafers ( 10 A), or possibly even a polyaniline film. Dirt , which may be either a problem or an advantage, will not be taken up here. Discussions will alternate between coated polymer films and condensed model molecular solid films, as necessary to illustrate points. 

Tlie detector consists of a 256 X 256 array of indium antimonide mesa photodiodes. These detectors are made by diffusing a sheet junction into a wafer of indium antimonide material. Afterwards, the diodes are delineated with a deep mesa trench, and then passivated. The wafer is attadied to a substrate and thinned to the correct thickness. The individual diodes receive a contact metallization, followed by an indium bump deposition. The die are then sawn from the wafer, screened, and are then ready to be naated to multiplexers. 

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