A field-shaping multi-well avalanche detector for direct conversion amorphous selenium

Abstract

Purpose: A practical detector structure is proposed to achieve stable avalanche multiplication gain in direct-conversion amorphous selenium radiation detectors. Methods: The detector structure is referred to as a field-shaping multi-well avalanche detector. Stable avalanche multiplication gain is achieved by eliminating field hot spots using high-density avalanche wells with insulated walls and field-shaping inside each well. Results: The authors demonstrate the impact of high-density insulated wells and field-shaping to eliminate the formation of both field hot spots in the avalanche region and high fields at the metal-semiconductor interface. Results show a semi-Gaussian field distribution inside each well using the field-shaping electrodes, and the electric field at the metal-semiconductor interface can be one order-of-magnitude lower than the peak value where avalanche occurs. Conclusions: This is the first attempt to design a practical direct-conversion amorphous selenium detector with avalanche gain. © 2013 American Association of Physicists in Medicine.