Device structures, fabrication methods, operating methods, and design structures for a silicon controlled rectifier. The method includes applying a mechanical stress to a region of a silicon controlled rectifier (SCR) at a level sufficient to modulate a trigger current of the SCR. The device and design structures include a SCR with an anode, a cathode, a first region, and a second region of opposite conductivity type to the first region. The first and second regions of the SCR are disposed in a current-carrying path between the anode and cathode of the SCR. A layer is positioned on a top surface of a semiconductor substrate relative to the first region and configured to cause a mechanical stress in the first region of the SCR at a level sufficient to modulate a trigger current of the SCR.