Goldsman and colleagues awarded US Patent for SiC-integrated circuit active photodetector

ISR-affiliated Professor Neil Goldsman (ECE) and his colleagues were issued U.S. Patent No. 10,446,592 on Oct. 15, 2019 for “silicon carbide integrated circuit active photodetector,” a device that provides accurate, reliable measurement of ultraviolet (UV) radiation.

Co-inventors on the patent are Akin Akturk, Zeynep Dilli, Brendan Cusack and Michael Gross. The patent is assigned to CoolCAD Electronics, LLC, a College Park company founded by Goldsman and Akturk for CAD and custom electronics design. The company carries out R&D projects on a wide cross-section of electronics, including semiconductor device modeling and design, integrated circuit modeling and design, and printed circuit board or full electronic system modeling and design.

About the invention
Accurate, reliable measurement of ultraviolet (UV) radiation is needed in a range of applications. Current UV measurement techniques include silicon (Si) based detectors, which can include Si based UV sensitive photodiodes, combined with Si based amplifiers and optical filters to remove non-UV wavelengths to which Si based UV sensitive photodiodes can also be sensitive.

UV detectors using Si-based UV sensitive photodiodes, though, can have shortcomings. For example, as stated above, Si based UV sensitive photodiodes can be sensitive to non-UV wavelengths, such as infrared (IR) and certain visible wavelengths. Optical filter devices may therefore be required to avoid the Si device being degraded or blinded by the non-UV wavelengths.

Present Si-based photodetector techniques also have the shortcoming of exhibiting insufficient, or less than desired, responsivity in the spectral region neighboring, for example, 270 nm. This region can be important for various applications pertaining to the UV-C part of the optical spectrum. Another shortcoming of Si based UV detectors can be leakage current, which can in turn decrease UV sensitivity and increase noise.

This invention is an integrated ultraviolet (UV) detector that includes a silicon carbide (SiC) substrate, supporting metal oxide field effect transistors (MOSFETs), Schottky photodiodes, and PN Junction photodiodes. The MOSFET includes a first drain/source implant in the SiC substrate and a second drain/source implant in the SiC substrate. The Schottky photodiodes include another implant in the SiC substrate and a surface metal area configured to pass UV light.

Published October 28, 2019