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Semiconductor Window For Infrared Detector

IP.com Disclosure Number: IPCOM000098157D
Original Publication Date: 1960-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Lyons, VJ: AUTHOR [+3]

Abstract

This entrance window or filter for an infrared detection system comprises a semiconductor element exhibiting a flat, high transmission spectral response within the range 1.3 to 25 microns and having a usable transmission which approaches 35 microns. The window consists essentially of cadmium diarsenide (CdAs(2)) crystals having an impurity content of less than 10/16/ net carriers per cc.

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Semiconductor Window For Infrared Detector

This entrance window or filter for an infrared detection system comprises a semiconductor element exhibiting a flat, high transmission spectral response within the range 1.3 to 25 microns and having a usable transmission which approaches 35 microns. The window consists essentially of cadmium diarsenide (CdAs(2)) crystals having an impurity content of less than 10/16/ net carriers per cc.

Single crystals of CdAs(2) may be prepared by a pulling technique such as described in a paper by R. Gremmelmaier in Zeitsschrift fur Naturwissenschaften, 11a, 511 (1956), starting with high purity cadmium and arsenic.

Single crystals are pulled from the melt using a seed crystal of the same material cut parallel to the crystallographic C axis of the unit cell. Windows are then prepared by cutting the crystal into parallel plates. The window should be oriented such that the incident radiation is directed along the C axis of the crystal. However, excellent transmission may be obtained with the infrared energy directed along the A axis or along points between these axes.

The window thickness is not critical and transmission is governed by the equation. ***

(Image Omitted)

***

k = the absorption coefficient

x = the thickness of the window material

r = reflectivity

Reflection losses may be reduced by coating the surface of the crystal with so called blooming agents such as silver chloride, potassium chloride, potassium bromide and silicon mo...