(US6249033-B1)      An apparatus for detecting energy and point of incidence of an ionizing event comprises a semiconductor layer with a first type of conductivity, with at least one first doped region having a first type of conductivity, and several corresponding second doped regions with a second type of conductivity associated to the first doped region, are formed on a first surface of the layer. The first doped region and the corresponding second doped regions define a respective drift path for charge carriers with the first type of conductivity. At least one third doped region with the second type of conductivity is formed on a second surface of the layer, with a device for biasing the second doped regions and the third doped region which is capable of reversely biasing the junctions between the third doped region and the semiconductor layer so as to deplete the semiconductor layer. Characteristically, the biasing device is capable of providing two different operating conditions of the detection apparatus, the first condition providing the formation of several potential energy wells for the charge carriers in the semiconductor layer at predetermined distances along the drift path from the first doped region, the 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 itself, and the second operating condition providing the removal of the potential energy wells so as to cause the charge carriers to drift towards the first doped region along the drift path, and keeping the charge carriers confined to directions which are perpendicular to the drift path.    USE -   For detecting energy and point of incidence of electromagnetic radiations, particularly but not exclusively x-rays or ionizing particles.    ADVANTAGE -   Has two different operating modes, the integration mode and the readout mode, it is only in the latter mode that the apparatus generally operates as a conventional silicon drift detector; the electric fields of the detection apparatus are different but nevertheless static in either operating condition.