Short-channel effects in Si/Si1-xGex retrograde double quantum well p-MOSFETs

Analytical investigation of short-channel effects in retrograde double quan tum well Si1-xGex-channel p-MOSFETs with effective channel lengths in the d eep-submicron regime is addressed. The short-channel effects are accounted for by treating the short-channel device as a long-channel one with an appa rently-reduced doping density which depends on the channel length and the g ate/drain bias. The analysis focuses on the threshold voltage reduction, th e gate voltage window, and the hole densities in the quantum wells. The mod el predicts significant differences in the threshold voltage reduction in t he different channels of the device. The reduction is negligible in the sur face parasitic channel, fairly small in the second quantum well (channel 2) below the surface channel, and relatively pronounced in the first quantum well closer to the depletion region (channel 1). Accordingly, the gate volt age window increases significantly. The hole density in the different chann els has also been found to be appreciably influenced by decreasing channel length. The validity of the model is confirmed by comparing analytical calc ulations with available experimental and numerical results. These investiga tions can be used as guidelines for scaling Si/Si1-xGex devices as they ill ustrate the degrees of freedom available to the Si/Si1-xGex MOSFET designer . (C) 1999 Elsevier Science Ltd. All rights reserved.