Fabrication methods by which the intrinsic noise is reduced in Si and CZT nuclear radiation detectors

Silicon PIN-type diodes with active areas of 1 cm 2 have been fabricated on n-type, high-resistivity (>10kΩ-cm), 550 µm thick 4″ Float-Zone (FZ) silicon substrates. In order to reduce the leakage-current density, optimized metal field-plate and multiple guard-ring structures were included in the electrode design. In addition, both phosphorus-doped polysilicon and amorphous silicon gettering resulted in n-type PIN diodes with room-temperaure leakage currents lower than 10 nA at −100V reverse bias voltage. Several gamma-ray spectra, from isotopic sources 133 Ba and 57 Co, were acquired when the PIN-type detector was connected to various preamplifiers from Ortec, Amptek and Endicott Interconnect Technologies, Inc. (EITI). The eV-5093 produced the best noise performance, yielding a full width at half maximum (FWHM) energy resolution of 4.7% at 122 keV and 1.88 % at 356 keV. Gettering methods by which the resolution is improved further are demonstrated.