Evidence for impact-ionized electron injection in substrate of n-channel MOS structures

Impact-ionization current during saturation mode operation is widely known in MOS devices. Although not noted in previous work, minority carriers also may be observed in the substrate, together with hole current. These minority carriers can degrade the MOS depletion layer lifetime, thus limiting the performance of MOS dynamic devices. A series of experiments utilizing the C-t method, the MOS capacitor surface potential measurement, and the charge-coupled device (CCD) is described, which provides evidence for electrically generated electrons in the substrate of n-channel MOS structures.