Embodiments of the invention are concerned with semiconductor circuit substrates for use in a radiation detection device, said radiation detection device comprising a detector substrate having a plurality of detector cells arranged to generate charge in response to incident radiation, each of said detector cells including at least one detector cell contact for coupling charge from said detector cell to said semiconductor circuit substrate. More particularly, in embodiments of the invention the semiconductor circuit substrate comprises: a plurality of cell circuit contacts, each of which is configured to receive charge from a corresponding detector cell contact, cell circuitry associated with said plurality of cell circuit contacts; one or more conductive pathways arranged to carry at least one of control, readout and power supply signals to and/or from said cell circuitry; and one or more signal pathways extending through said semiconductor circuit substrate, said one or more signal pathways being electrically coupled to said conductive pathways so as to provide an external signal interface for said cell circuitry. Embodiments in accordance with the present invention thus provide a means of routing signals through the semiconductor circuit substrate to an electrical contact on a surface of the semiconductor circuit substrate. The electrical contact on the surface of the circuit substrate can then be directly coupled to a corresponding electrical contact on a mount.