Simulations of electric potential and field profiles in Si microstrip detectors with various strip widths/pitch configurations: introduction of guard strip concept for better field distribution

Two-dimensional simulations of the electrical properties of Si microstrip detectors 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). The value of V_fd increases with the decreasing ratio of W/P: V_fd for W/P=0.1 (P=100 m) is almost twice of 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<9.3. 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 a great promise to push the W/P ratio down to 0.1 without greatly affecting the detector full depletion voltage