The Development of Avalanche Amplifying pnCCDs: A Status Report

Abstract

Imaging detectors with high quantum efficiency over a wide spectral range, low noise, and fast readout will prove to be very useful in many applications in astronomy and other fields. In 2005 we have started to develop pnCCDs with high quantum efficiency for fast imaging of single optical photons in the wavelength range ∽350–1100 nm. The concept is based on fully depleted, back-illuminated pnCCDs with a sensitive thickness of 450 μmum which were originally developed for fast single photon X-ray imaging and spectroscopy. The pnCCD with column parallel readout shall be modified such that the on-chip JFET amplifiers are replaced by avalanche amplifier (AA) cells operated in the linear regime with a gain up to a few thousand. An additional on-chip n-channel MOSFET manages the suitable change of impedance such that the resulting signal can be handled by the following CAMEX readout ASICs. The amplification of the avalanche process must be sufficiently low to prevent optical crosstalk between the detector channels. The anticipated format in the imaging area will be of the order of 256× 256 pixels with a size of ∽50 μmum. The frame rate should be as high as 1000 frames per second.