Photocathode for the 8500 angstrom through 9000 angstrom range, improving efficiency by an order of magnitude, is achieved with a gallium arsenide cesium oxide photocathode. Protection of the GaAs surface from contamination during bake-out is another important function

Sonnenberg, H.

Taynal, J. D.

English

NASA Technical Reports Server

1972	 B72-10152 
NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Advanced Infrared Photomultiplier 
The problem: 
Present photocathodes used in the range from 8500 A 
to 9000 X are extremely inefficient. 
The solution:	 0 
A photocathode for the 8500 A through 9000 A 
range which improves efficiency by an order of magni-
tude is achieved with a gallium arsenide cesium oxide 
(GaAs-Cs2 0) photocathode. 
How it's done: 
The GaAs emitter is composed of conventionally 
grown epitaxial layers doped with Mn (Manganese) at a 
3.8 x 10 18 /cm 3 acceptor concentration density. The 
substrate temperature when the polycystalline material 
is formed is 600°C; at 700°C, the layer appears to be 
single-crystal. Infrared photosurfaces inherently require 
atomically clean surfaces since contaminants greatly 
alter the low-energy threshold for photoemission. This 
is achieved and maintained with an ultra high vacuum. 
The surface is chemically cleaned, and a thin protective 
coating is formed over the crystal. This coating is stable 
to about 500°C, at which temperature it leaves the sur-
face completely. This results in a clean surface. Another 
important function of the coating is to protect the GaAs 
surface from contamination during bake-out. The high-
speed, crossed-field photomultiplier and image intensifier 
were then constructed in a conventional manner. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A & TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10152 
Patent status: 
No patent action is contemplated by NASA. 
Source: H. Sonnenberg and J. D. Taynal of 
Sylvania Electronics Western Division
under contract to

Marshall Space Flight Center
(MFS-20941) 
Category 03 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000152 2020-03-17T03:31:56+00:00Z


Advanced infrared photomultiplier

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