Enhancement mechanisms for leakage current in silicon devices

The generation of dark or leakage current in silicon devices is treated by the Shockley-Read-Hall equation. This involves a deep level in the silicon band gap, the excitation of an electron from the valence band to the deep level, and then from the deep level to the conduction band. The generation rate is increased by electric fields, stress, and heavy doping. The Poole-Frenkel effect describes the first and acts to increase the apparent cross section of the deep level, and, hence, the leakage current. Enhancements of more than an order of magnitude occur when the electric field exceeds 100,000 V/cm. Stress and heavy doping increase the leakage current through a narrowing of the band gap and a growth in the effective intrinsic carrier concentration. The presentation will show the qualitative dependence of the leakage current on these effects and possible ways to confirm their contribution to measured leakage currents.