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Multiple Reflective Laser Detector Diode

IP.com Disclosure Number: IPCOM000093499D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Lanza, C: AUTHOR

Abstract

Photodiode 1 comprises N-type germanium body 3, which is oriented to expose a (111) face. P-type region 5 is formed in body 3, e.g., by diffusion, epitaxial growth, etc., to define PN junction 7. Ohmic contacts 9 and 11 are connected to body 3 at surfaces 13 and 15.

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Multiple Reflective Laser Detector Diode

Photodiode 1 comprises N-type germanium body 3, which is oriented to expose a (111) face. P-type region 5 is formed in body 3, e.g., by diffusion, epitaxial growth, etc., to define PN junction 7. Ohmic contacts 9 and 11 are connected to body 3 at surfaces 13 and 15.

The surface 15 is exposed to an appropriate etchant, e.g., 4HF: 2HNO(3) : 4H(2)O + A(9)NO(3), to form etch pits 17. The latter are of pyramidal shape and are defined by three (111) planes. Each face forms an angle of 19 degrees 28' with surface 15, which angle exceeds the critical angle for the incident light in germanium.

Since the faces of etch pits 17 are formed from crystal planes, they are highly polished and form excellent reflectors. Thus, light directed into body 3, as indicated by the arrows, is totally reflected from the faces of etch pits 17 and the surface 13 in random fashion to make multiple passes across PN junction 7. Due to the random arrangements of the reflected surfaces of etched pits 11, the optical path length is extended and light, absorbed within a diffusion distance of the PN junction, is materially increased so that the efficiency of photodiode 1 is improved for long wavelength response.

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