Abstract: A gamma radiation detector comprises a semiconductor body and two metal electrodes attached to two spaced surface zones of said semiconductor body, said detector being characterized by the combination of the following features: (a) The semiconductor body consists of a uniform semiconductor material of the same conductivity type; (b) Charge carriers of both types are mobile in the semiconductor material and the product of their mobility multipled by their free drift time (life) exceeds 10.sup..sup.-9 m.sup.2 V.sup..sup.-1 for each type of carrier; (c) An insulating layer which is thin in relation to the distance separating said two surface zones is interposed between at least one of said electrodes and the surface zone to which it is attached.