Semiconductor radiation detector with enhanced charge collection

A radiation detector for detecting ionizing radiation, comprising:

• (a) a semiconductor responsive to ionizing radiation having a plurality of sides;
• (b) a cathode formed on a first side of the semiconductor, the cathode having a cathode surface area and wherein the cathode is coupled to a cathode voltage source, the cathode having a cathode voltage, V.sub.b ;
• (c) an anode formed on a second side of the semiconductor, the second side opposing the first side and having a center, the anode comprising a contact located near the center of the second side and having a substantially smaller surface area than the cathode surface area, wherein the anode is coupled to an anode voltage source, the anode having an anode voltage, V.sub.a ;
• and
• (d) a control electrode formed on the second side of the semiconductor, the control electrode forming a single ring surrounding the anode, wherein the control electrode is coupled to a control voltage source, the control electrode having a control voltage, V.sub.c, such that V.sub.c <V.sub.a.

A method for detecting an ionizing radiation emanating from a source using a radiation detector, the radiation detector comprising a semiconductor having a plurality of sides, the semiconductor including a control electrode, a cathode side and an anode side, the cathode side having a cathode and the anode side having an anode, the method comprising the steps of:

• (a) placing the radiation detector in a path of the radiation emanating from the source;
• (b) generating an electric field internal to the semiconductor via voltages applied on the cathode and anode;
• (c) creating an electron charge cloud and an associated hole cloud within the semiconductor by the ionizing radiation;
• (d) guiding the electron-charge cloud toward the anode by the electric field;
• (c) sharing, between the anode and the control electrode, charge induced by the charge clouds when they are located a relatively significant distance from the anode, such that the charge induced on the anode is very small compared with the charge induced on the control electrode;
• and
• (f) decreasing toward zero the induced charge on the control electrode by the electron-charge cloud and increasing the induced charge on the anode to the full value of the electron-charge cloud that arrives at the anode.

A system for detecting an ionizing radiation, comprising:

• (a) a radiation detector, including:
• (1) a semiconductor having a plurality of sides,
• (2) a cathode formed on a cathode side of the semiconductor,
• (3) an anode formed on at least one side of the semiconductor different from the cathode side,
• (4) a control electrode formed on at least one side of the semiconductor different from the cathode side;
• and
• (b) means for forming an electric field internal to the semiconductor;
• wherein, when the ionizing radiation is absorbed in the radiation detector, a movable charge cloud is generated within the semiconductor as a result of the ionizing radiation;
• wherein the electric field guides the electron-charge cloud toward the anode;
• wherein the anode and the control electrode share a charge induced by the charge cloud when the charge cloud is located a relatively significant distance away from the anode, such that the charge on the anode is small;
• and
• wherein the charge induced by the electron-charge cloud on the anode increases as the electron-charge cloud becomes close to the anode.

A radiation detector array, comprising:

• (a) a semiconductor having a plurality of sides and a thickness of at least about 0.5 mm;
• (b) a cathode formed on at least one side of the semiconductor;
• (c) an array of anodes formed on at least one side of the semiconductor;
• and
• (d) a control electrode pattern, formed on at least one side of the semiconductor, for directing charge clouds resulting from ionizing events in the semiconductor toward a respective anode and for substantially reducing the effect on the array of anodes of hole trapping in the semiconductor, the control electrode pattern being formed such that it affects each of the anodes in the array of anodes,
• wherein the radiation detector is capable of detecting energies greater than about 20 KeV.