PureB single-photon avalanche diodes for low-energy electron detection down to 200 eV.

Single-photon avalanche diodes (SPADs) have been fabricated on Si using PureB (Pure Boron) chemical-vapor deposition (CVD) to create both a nanometer-thin anode junction and a robust front-entrance window. The device shows high sensitivity to low radiation levels of electrons with energies down to 200 eV when measurements are performed at room temperature where the dark count rate can be as low as 10 Hz. An implicit guard ring, using an n-enhancement implantation in the central region of the diode, is applied, and this gives a very uniform sensitivity across the whole front-entrance window.