Speaker
Mr
Ryan Dowdy
(UIUC)
Description
GaAs has long been used as a photocathode material for its good quantum efficiency in the near infrared (IR) spectral range. Its narrow band gap, the direct transition, the availability of high quality substrates and growth methods has made GaAs cathodes the golden standard in night-vision applications and other important IR-detection systems.
We focus our interest to tune the wavelength response of this classical IR-cathode to the optical and UV range, especially the wavelength range around 400nm. The specifics of GaAs band structure result in strong optical absorption in the frequency range of interest. Nevertheless, standard GaAs photocathodes perform poorly in the sub-400nm wavelength range. These limitations can be overcome by a two-step approach: 1.) Creating a photocathode thin enough for photo-generated carriers to be emitted before recombination and 2.) Implementing a tiered doping profile to create a strong built-in field to guide carriers to the surface.
We will present our program which is based on the rational design of the device structure, state-of-the-art growth techniques, and the corresponding materials-, especially surface-science program which allows cross correlation between functionality and microscopic structure. The talk will address the specific problems correlated with the transfer and bonding of ultra-thin GaAs layers onto glass substrates and the optimization of the negative electron affinity of the cathode ,e.g. the surface modifications including the activation process.
Author
Mr
Ryan Dowdy
(UIUC)
Co-authors
Dr
Klaus Attenkofer
(ANL)
Dr
Seon Woo Lee
(ANL)
