I-MOS transistor with an elevated silicon-germanium impact-ionization region for bandgap engineering

Abstract

An impact-ionization MOS (I-MOS) transistor with an elevated impact-ionization region (I-region) and excellent subthreshold swing of 3.2 mV/dec at room temperature is demonstrated. An elevated Si 0.75Ge0.25 region is integrated and employed to engineer the bandgap and impact-ionization rate in the I-region. Compared to a device with a Si I-region, an I-MOS device with a Si0.75Ge0.25 I-region shows significantly enhanced performance due to the smaller bandgap of the I-region and the enhanced impact-ionization rate. For the I-MOS device with a Si0.75 Ge0.25 I-region, the breakdown voltage is also reduced, and a significant drive current enhancement is achieved at VG-VT=1 V and a gate length of 80 nm. © 2006 IEEE.