The incorporation of Si1-xGex alloy heterostructures into conventional Si processes has been proposed as a means of improving the operating frequency and overall performance of Si field effect transistors. One parameter expected to benefit from this approach is the hole mobility, which would have important implications for high speed CMOS applications. Measured values of the hole mobility, however, have failed to live up to early expectations, and much ongoing research is directed at understanding whether this is an intrinsic limitation (e.g. due to alloy disorder scattering), or due to imperfections arising in the growth and fabrication process. In this thesis, a detailed theoretical study is presented of the hole mobility in single sub-band Si1-xGex heterostructures.

The increasing demand for high performance as well as low standby power devices has been the main reason for the aggressive scaling of conventional CMOS transistors. Current devices are at the 32nm technology node. However, due to physical limitations as well as increase in short-channel effects, leakage, power dissipation, this scaling trend cannot continue and will eventually hit a barrier. In order to overcome this, alternate device topologies have to be considered altogether. Extensive research on ultra thin body double gate FETs and gate all around nanowire FETs has shown a lot of promise. Under strong inversion, these devices have demonstrated increased performance over their bulk counterparts. This is mainly attributed to full carrier inversion in the body. However, these devices are still limited by lithographic and processing challenges making them unsuitable for commercial production. This thesis explores a unique device structure called the CFET (Cylindrical Field Effect Transistors) which also like the above, relies on complete inversion of carriers in the body/bulk. Using dual gates; an outer and an inner gate, full-volume inversion is possible with benefits such as enhanced drive currents, high Ion/Ioff ratios and reduced short channel effects.

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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