P-i-n CdTe 128-pixel detector for gamma-ray imaging fabricated by excimer laser processing

A 128-pixel gamma-ray imaging detector unit, which has high-energy resolution with room temperature operation, was fabricated by using diode-type CdTe detector. The diode structure was prepared by indium-doped n-type CdTe thin layer formed by excimer laser doping on one-side of high resistivity p-like single crystal CdTe wafer, and gold electrode as a Shottkey electrode evaporated on opposite side of the wafer. This diode-detectors showed good diode I-V characteristics with low leakage current. This CdTe detectors were pixelized in the 2mm x 2mm, and the 128 chips (32 x 4 chips) were mounted, on the ceramic printed circuit boards at 3mm interval with 1mm gap. The printed circuit boards are directly connected with the MCSA-EX1 ASIC chip and 128 ch radiation spectrum analyzer systems. When using the Am-241 and the Co-57 as radioisotopes, the spectral response from all pixels had within 4.4 keV of FWHM at 122 keV peak of Co-57 for radiation performed at room temperature. The intensities of the peak from pixels were also uniform.