Controlled-Drift Apparatus for detecting energy and point of incidence of electromagnetic radiation or ionizing particles

An apparatus for detecting energy and point of incidence of an ionizing event comprising a semiconductor layer with a first type of conductivity, in which at least one first doped region with the first type of conductivity and a corresponding plurality of second doped regions with a second type of conductivity associated to said at least one first doped region are formed on a first surface of said layer, said at least first doped region and said corresponding plurality of second doped regions defining a respective drift path for charge carriers with the first type of conductivity, and at least one third doped region with the second type of conductivity is formed on a second surface of said layer, and means for biasing said second doped regions and said third doped region which is capable of reversely biasing the junctions between the second doped regions and the semiconductor layer and between the third doped region and the semiconductor layer so as to deplete the semiconductor layer. Said biasing means is capable of providing two different operating conditions of the detection apparatus, the first operating condition providing the formation of a plurality of potential energy wells for said charge carriers in the semiconductor layer at predetermined distances along said drift path from said first doped region, said wells being able to confine all of the charge carriers generated by an ionizing event essentially to the points of incidence of the ionizing event, the second operating condition providing the removal of said potential energy wells so as to cause the charge carriers to drift towards said at least one first doped region along said drift path and keeping the charge carriers confined to directions which are perpendicular to the drift path. The electric fields in the apparatus are different, although static in the two different operating conditions.