Utilization of Web Silicon for Position-Sensitive Detectors

Position-sensitive surface-barrier detectors have been made with web silicon, a hyper-pure silicon in ribbon form. Several characteristics of this material are especially suited for position detectors, i.e., long lengths, flexibility and high surface lifetimes. In addition, the structural stability, thickness uniformity, and thin cross sections make this material attractive for standard or position sensitive dE/dx detectors. Counters with active areas of 2-3.5 cm × 2-4 mm have been tested with 5.5-MeV alpha particles yielding spectra sensitive in position to less than 1%. A region of twin planes is exhibited within the material by changes in the slope of the plots of detector capacitance and leakage current as functions of reverse bias. The effect of the twin planes on the carrier collection efficiency has been investigated with several samples and found to be significant in certain cases. These results are discussed in terms of carrier lifetimes.