Effects of the Resistivity and Crystal Orientation of the Silicon PIN Detector on the Dark Current and Radiation Response Characteristics

The effects of the resistivity and crystal orientation on the leakage current and radiation response characteristics have been studied. The detector with (111) oriented substrate shows higher leakage current than (100) orientation due to the higher interface trap density at the Si/SiO₂ interface. And high resistive substrate shows larger leakage current than low resistive one because of its wider depletion width at the same bias voltage. However, in case of (100) oriented substrate, the leakage current of low resistive substrate is larger than high resistive substrate at high reverse bias. It seems that thermionic field emission (TFE) current for low resistive substrate increased at high reverse bias. To compare the charge generation and collection for the radiation, we irradiated an X-ray beam to each detector and read the output current. The detector with (111) oriented substrate shows 20% higher output current than (100) orientation and it is independent on the resistivity of the substrates. The most influential factor on the output current is the thickness of the wafer. From the results we can suggest a high resistive, (100) oriented and thick wafer for direct type radiation detector, and a low resistive and thin wafer for in-direct type detector. Finally, we assembled our detector with read-out integrated circuit for the application of gamma ray dosimeter and our detector is very sensitive to Cs₁₃₇ natural gamma ray.