Semiconductor radiation detector with enhanced charge collection

Abstract

A radiation detector for detecting ionizing radiation. The detector includes a semiconductor having at least two sides. A bias electrode is formed on one side of the semiconductor. A signal electrode is formed on a side of the semiconductor and is used to detect the energy level of the ionizing radiation. A third electrode (the control electrode) is also formed on the semiconductor. The control electrode shares charges induced by the ionizing radiation with the signal electrode, shielding the signal electrode until the charge clouds are close to the signal electrode. The control electrode also alters the electric field within the semiconductor, such that the field guides the charge clouds toward the signal electrode when the clouds closely approach the signal electrode. As a result, signal loss due to trapped charge carriers (i.e., electrons or holes) is minimized, and low-energy tailing is virtually eliminated. A fourth electrode can be added to separate the charge-shielding and field shaping functions of the control electrode. More electrodes can be added to further enhance both functions. The invention can be used in several cross-strip detector configurations, in a side-entry radiation detector, and with liquid/gas ionization detectors.

What is claimed is:  
     
         1 . A radiation detector, comprising: 
 (a) a semiconductor having a plurality of sides and a thickness of at least about 0.5 mm;    (b) at least one bias electrode formed on at least one side of the semiconductor;    (c) at least one signal electrode formed on at least one side of the semiconductor; and    (d) at least one control electrode, formed on at least one side of the semiconductor, configured so as to form an electric field pattern within the semiconductor that directs charge clouds resulting from ionizing events in the semiconductor to the signal electrodes;    wherein the radiation detector is capable of detecting energies greater than about 20 KeV.