Separate absorption and detection diode for two-color operation

US7608830B1 · kind B1 · utility

Assignee

• DRS Sensors & Targeting Systems, Inc. · US

Inventor

• Michael A. Kinch · Dallas, US

Key dates

• Filing date: Oct 13, 2005
• Grant date: Oct 27, 2009
• Expiry date: Feb 21, 2027

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10F30/222

Abstract

A photodiode for detection of preferably infrared radiation capable of detecting two different wavelengths wherein photons are absorbed in one region and detected in another. In one example embodiment, an absorbing P region is abutted with an N region of lower doping such that the depletion region is substantially (preferably completely) confined to the N region. The N region is also chosen with a larger bandgap than the P region, with compositional grading of a region of the N region near the P region. This compositional grading mitigates the potential barrier between the respective bandgaps. Under first voltage conditions a potential barrier prevents minority carriers from moving from the P region to the N region, but photons of energy large enough to generate minority carriers within the N region are detected. Under reverse bias, the barrier is substantially reduced or disappears, allowing charge carriers to move from the absorbing P region into the N region (and beyond) where they are detected. Thus, under reverse bias, both wavelengths of energy can be detected, and separated by differencing the output.