AES Semigas


9 September 2020

SMI to co-develop III-N photocathodes with Cornell and SUNY Albany

Structured Materials Industries Inc (SMI) of Piscataway, NJ, USA – which provides chemical vapor deposition (CVD) systems, components, materials and process development services – has been awarded a US Department of Energy (DOE) Phase I Small Business Innovation Research (SBIR) contract for a nine month project – in partnership with Cornell University (CU) and the State University of New York (SUNY) Polytechnic Institute-Albany – to grow III-N structures using metal-organic chemical vapor deposition (MOCVD) and to fabricate high-brightness photocathodes (PCaths).

The high-brightness PCaths are needed for DOE facilities and laboratories employing electron accelerators and are used for free-electron lasers (FEL), ultrafast electron microscopy, and diffraction, among other applications.

The primary material of focus is III-N layers with high chemical electro-negative surfaces that may yield the highest-brightness low mean transverse energy (MTE) electrons, and sufficiently high quantum efficiency for electron accelerator and electron diffraction microscopy applications.

“The III-N material system is familiar for its applications in LEDs and high-power, high-frequency devices; but it has also been identified to exhibit negative electron affinity (NEA) in properly designed structures with proper surface treatment,” notes principal investigator and SMI research scientist Dr Arul Arjunan. “When properly tuned, these properties lead to high-brightness emission of electrons when illuminated with a light which has a wavelength less than the bandgap,” he adds. “These materials hold great promise to perform better than conventional alkali-antimonide, alkali-telluride, gallium arsenide (GaAs) or metal PCaths that are highly reactive and rapidly degrade over hours to at most months due to chemical poisoning or loss of alkali metals even in isolated ultra-high-vacuum (UHV) enclosures. The III-N based photocathodes to be developed in this project will represent a new advancement in photocathode stability.”

“This is an exciting area of fundamental high-energy physics research,” says SMI’s president & CEO Dr Gary S. Tompa. “This work is a nice connection to my early work in forming negative electron affinity surfaces for generating negative hydrogen ion beams, and this work may be able to contribute in that area as well,” he adds.

In the past, SMI has worked on several different III-N funded research programs and has built tools for R&D of III-nitrides, including bulk material growth tools.

Tags: SMI