A silicon based detector for low energy gamma-ray detection is used in various fields such as nuclear medicine, gravitational wave research and detecting underground nuclear test due to its advantage of good intrinsic energy resolution, small active volume and fast response time. We manufactured silicon PIN diode and photodiode sensors which have an advantage in terms of low manufacturing cost and detection efficiency due to its thick depletion depth. We used 1x1 cm2 silicon sensors, 400, 650 μm thick with a light entrance window and 500 μm thick without a light entrance window. In electrical properties of the silicon sensor, the leakage current per unit area for the 400, 500, 650 μm thick sensor were measured to be 12.1, 4.1, 10.7 nA/cm2 and the capacitance per unit area were measured to be 156.8, 158.8, 159.9 pF/cm2. We studied the performance of the sensor in terms of gamma-ray energies between 14.4 and 136.5 keV from 241-Am, 133-Ba and 57-Co radioactive sources. The signal height of the gamma-ray energy shows good linearity for all of fabricated sensors. The energy resolutions as a function of gamma-ray energy show signal fluctuation and electronic noise. The noise contributions were obtained to be 2.9, 1.8, 2.0 keV for 400, 500, 650 μm thick sensors, respectively. We confirm that the electronic noise is an important factor in the low energy region. The dependence on the sensor thickness is studied with 136.5 keV gamma-ray from 57-Co radioactive source which has the best SNR and it is confirmed that the detection efficiency gets better as the sensor thickness increases.
Thesis Advisor: Prof. Hwanbae Park