Simulations of electric potential and field profiles in Si microstrip detectors using the guard-strip concept

Two-dimensional (2-D) simulations of the electrical properties of Si microstrip detectors with various strip width/pitch configurations have been systematically performed using a processing and device simulation tool. It has been found that the detector full depletion voltage (V_fd) depends greatly on the ratios of strip width (W) to pitch (P) and pitch to detector thickness (d). V_fd increases with the decreasing ratio of W/P:V_fd for W/P=0.1(P=100 μm) and is almost twice that of a bulk detector (W/P=1) for different bulk resistivities (simulation of before and after radiation). The increasing rate of V_fd with decreasing W/P is much higher when W/P<0.3. It has also been found that, for a given strip width, the strip pitch should be kept smaller than the sum of detector thickness and strip width, i.e., P<d+W or P<d (if W≪d). Otherwise, the value of V_fd will be affected significantly (much larger than that of a bulk detector), It is clearly shown through the simulation that this increase of V_fd is due to the lateral depletion from the strip edge. A new width/pitch configuration with guard strips is proposed, which has shown great promise to push the W/P ratio down to 0.1 without greatly affecting the detector full depletion voltage