Accession Number:

AD0720796

Title:

The Graded-Gap Semiconductor Photoemitter

Descriptive Note:

Technical note

Corporate Author:

MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s):

Report Date:

1971-01-22

Pagination or Media Count:

32.0

Abstract:

A new scheme is proposed for achieving photoemission from semiconductors at infrared wavelengths from about 1 micrometers to well beyong 10 micrometers. The device consists of a graded-energy-gap p-type semiconductor with a low work function coating on the wide-gap side. Electrons, which are photoexcited from the valence to the conduction band by long wavelength radiation in the narrow-gap region are drifted by an applied electric field into the wide-gap region from where they are emitted into vacuum. Graded-gap Hgx-1 CdxTe is considered for a photoemitter covering wavelengths to about 12 micrometers and both Ga1-xInxAs and InAsxP1-x are proposed as possible alloys for 3 micrometers photoemission. For the simplest case of a linearly graded gap and a constant conductance, expressions are derived for the length of the graded region required to minimize power dissipation and for the speed of response. A calculation is also made of the dark current which results from thermal generation in the narrow-gap region in order to determine the operating temperature required for achieving a desired noise-equivalent power at any wavelength.

Subject Categories:

  • Electrical and Electronic Equipment
  • Infrared Detection and Detectors
  • Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE