Spectral characterisation of a blue-enhanced silicon photodetector

In this work we report on spectral response data and gamma ray spectroscopy measurements using two newly developed silicon photodetectors that are designed to have enhanced sensitivity in the blue spectral region. The enhanced sensitivity is a result of our newly developed ion implantation profile used to create the active area of the photodetector. The quantum efficiency of the new photodetectors (without any optimised antireflective coating) has been measured to be ~40% at a wavelength of 420 nm. Gamma ray spectroscopy experiments have been performed using a CsI(Tl) and a LSO crystal excited by a ¹³⁷Cs or ²²Na source and read out by the new photodetectors. We have measured an energy resolution of 7.7% and 22.7% FWHM for the 662 keV gamma rays from a ¹³⁷Cs for the CsI(Tl) and LSO scintillator crystal respectively. We intend to use the photodetectors, in the form of a detector array optically coupled to CsI(Tl) or LSO, in the development of a new scintillator detector module for use in positron emission tomography