First Principles Studies on Oxide Semiconductors for Back-end-ofline Transistor Applications

The development of high-performance p-type and n-type oxides with good carrier mobilities and wide band gaps is critical for the applications of metal oxide (MO) semiconductors in back-endof-line (BEOL) CMOS devices. [S. Salahuddin et al. Nat Electron. 1, 442 (2018)] Currently available oxide semiconductors are limited to n-type conduction, and p-type oxides have inferior performance due to carrier mobilities and dopability which are significantly lower than that of their n-type counterparts. This thesis devotes to studying and identifying novel high mobility p-type oxide candidates with wide band gaps and robust phase stabilities. Using first principles studies, we have identified several promising candidates including Rb2Sn2O3, TiSnO3, Ta2SnO6, and Sn5(PO5)2 that would be of interest as high-mobility p-type oxides. An engineering method is also developed to enhance the bandgap and hole mobility in widely investigated p-type oxide SnO. Amorphous phase engineering is revealed effectively improving the hole dopability and hole transport. Electron transport study on n-type oxides sheds light on the defect controlling and film density engineering in improving the n-type BEOL device performances. Our results provide fundamental materials insights into rational design of high mobility oxides semiconductors and serve as a guide for experimental realization of oxide semiconductors based BEOL transistors.