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 γ ray dosimeter and our detector is very
sensitive to Cs137 natural γ ray.