3D simulations of 3D silicon radiation detector structures

The simulations carried out in three dimensions (3D) are becoming important as more and more detector structures are fabricated beyond the traditional planar ones. A rectangular 3D detector structure is simulated using a finite-element (FE) simulation software ISE-TCAD. The basic characteristics of the detector structure simulated in two dimensions (2D) and 3D are compared in order to determine whether there are differences between the two approaches. Effects of the surface charge and surface recombination to the electrostatic potential, electric field, leakage current and capacitance are studied in detail. The 2D and 3D simulations give similar results on IV and CV characteristics when the surface effects are not included in the simulations. The presence of the surface charge at the silicon–oxide interface increases the leakage current while protecting the detector from the surface currents. It is shown that the vertical spacing of the grid below the surface is playing a critical role in the current results.