A method of manufacturing a radiation detector having a plurality of conductive contacts on a surface of a cadmium-based semiconductor substrate, in which each of the conductive contacts is located at a respective contact position and is suitable for joining with a bump bond, the method including the steps of: forming a layer of photoresistive material on said substrate surface; removing said photoresistive material from areas corresponding to said contact positions to expose said semiconductor substrate surface; forming a plurality of contiguous layers (8,9; 36, 38;45...48) of conductive material on remaining photoresistive material and on said exposed semiconductor substrate surface, each of the plurality of contiguous layers comprising one of platinum, nickel, gold, indium, titanium, tungsten, a nickel/gold alloy and a titanium/tungsten alloy, the plurality of layers including first and second layers, wherein the first layer is formed adjacent to the substrate, and the second layer comprises gold; removing conductive material overlying said remaining photoresistive material by removing said remaining photoresistive material so as to form, from remaining conductive material, said conductive contacts on the substrate surface, the conductive contacts defining one or more radiation detector cells in the semiconductor substrate; applying a layer of aluminium nitride passivation material on said second, gold, layer of the conductive contacts and the regions between said contacts; forming a further layer of photoresistive material over said passivation layer; removing portions of the further photoresistive layer to expose portions of the passivation material overlying said conductive contacts; removing, using a passivation etchant, portions of said passivation material overlying the conductive contacts to expose the conductive contacts, such that passivation material remains in the regions between said contacts, wherein the portions of passivation material are removed from areas smaller in size than the size of said conductive contacts such that the remaining passivation material overlaps the second, gold, layer of the conductive contacts; and removing remaining further photoresistive material. forming a layer of photoresistive material on said substrate surface; removing said photoresistive material from areas corresponding to said contact positions to expose said semiconductor substrate surface; forming a plurality of contiguous layers (8,9; 36, 38;45...48) of conductive material on remaining photoresistive material and on said exposed semiconductor substrate surface, each of the plurality of contiguous layers comprising one of platinum, nickel, gold, indium, titanium, tungsten, a nickel/gold alloy and a titanium/tungsten alloy, the plurality of layers including first and second layers, wherein the first layer is formed adjacent to the substrate, and the second layer comprises gold; removing conductive material overlying said remaining photoresistive material by removing said remaining photoresistive material so as to form, from remaining conductive material, said conductive contacts on the substrate surface, the conductive contacts defining one or more radiation detector cells in the semiconductor substrate; applying a layer of aluminium nitride passivation material on said second, gold, layer of the conductive contacts and the regions between said contacts; forming a further layer of photoresistive material over said passivation layer; removing portions of the further photoresistive layer to expose portions of the passivation material overlying said conductive contacts; removing, using a passivation etchant, portions of said passivation material overlying the conductive contacts to expose the conductive contacts, such that passivation material remains in the regions between said contacts, wherein the portions of passivation material are removed from areas smaller in size than the size of said conductive contacts such that the remaining passivation material overlaps the second, gold, layer of the conductive contacts; and removing remaining further photoresistive material.