Device structures and design structures for a silicon controlled rectifier, as well as methods for fabricating a silicon controlled rectifier. The device structure includes first and second layers of different materials disposed on a top surface of a device region containing first and second p-n junctions of the silicon controlled rectifier. The first layer is laterally positioned on the top surface in vertical alignment with the first p-n junction. The second layer is laterally positioned on the top surface of the device region in vertical alignment with the second p-n junction. The material comprising the second layer has a higher electrical resistivity than the material comprising the first layer.