Simulation of charge carrier transport in pixelated micro-structured semiconductor neutron detectors

Micro-structured Semiconductor Neutron Detectors (MSNDs) offer greater neutron sensing efficiency than thin-film coated diode devices and have been demonstrated as monolithic detectors. Here, a neutron imaging device is proposed, consisting of an MSND integrated with the Timepix read-out chip. The device serves as a combined neutron and photon imager, with particle discrimination accomplished via cluster morphology and total energy deposition. In this work, signal formation in the sensor is modeled and simulated. COMSOL Multiphysics is used to model the semiconductor physics of the three-dimensional device structures, obtaining electric field, weighting field, and charge carrier concentrations. Geant4 is used to simulate radiation transport and energetic particle ionization events, and Allpix
²
is employed to simulate mobile charge carrier transport and signal charge induction at the pixel electrodes. Results of this simulation work include a pixel charge map generated for a Gaussian 0.025 eV neutron beam incident on the sensor.