Silicon drift detectors with spiraling electron transport and reduced lateral broadening

A new drift detector has been designed, fabricated, and tested in which the external applied field has radial symmetry but the electron cloud, generated by ionizing radiation, follows a spiral-shaped path toward one central collecting electrode. Regions of deep p- and n-implants are used to generate the spiraling drift channel for the electrons close to the implanted side of the detector wafer and to suppress broadening in the direction transverse to the drift. A detailed study of the new detector (design, simulation, and experimental measurements) is presented that shows the combined effect of the deep implants and of the external applied field on the electron transport. Applications of this technique will be discussed, e,g., two-dimensional position-sensing drift detectors with single output channel, compact delay lines in the microsecond range, and study of long-term electron drift.