As modern computer technologies continue to shrink in size, the role of atomic scale defects becomes increasingly important. In addition, the use of novel materials and processing techniques is becoming a necessity. In this spirit, we investigate the impact of defects in novel complementary metal-oxide-semiconductor (CMOS) devices as well as for quantum computing applications.

Silicon CMOS technology has been tremendously successful, due to the high quality Si/SiO₂ interface. However, shrinking device dimensions require dielectrics with higher electrical permittivity to maintain small gate leakage. In 45 nm gate length devices and beyond, HfO₂ has already been integrated into the CMOS infrastructure. The introduction of novel gate dielectrics has spurred the semiconductor industry to also consider novel channel materials with high carrier mobilities. We will discuss potential materials for consideration, focusing specifically on germanium and III-V metal-oxide-semiconductor (MOS) devices.

Using first-principles calculations, we investigate the role of defects in such devices. In germanium, we analyze the role of both interfacial dangling-bond defects and vacancies. For III-V MOS structures, we discuss the potential for Al₂O₃ as a gate dielectric, and characterize the behavior of certain defects as potential sources of fixed charge and border traps. We also determine the effectiveness of hydrogen passivation on various defects in germanium and Al₂O₃, and examine the origins of Fermi-level pinning at InAs surfaces.

Finally, we also consider the role of defects in quantum computers, particularly, how defects themselves can be used as qubits. Recently, a nitrogen-vacancy defect complex (NV^-1) in diamond has generated much interest, since its quantum state can be initialized, manipulated, and measured with high fidelity, all at room temperature. We describe how to systematically identify other defects with similar properties. We present a list of physical criteria that these defects and their hosts should meet and explain how these requirements can be used in conjunction with first-principles calculations to intelligently sort through candidate defect systems. To illustrate these points in detail, we compare calculations of the NV^-1 defect in diamond with those of several deep centers in silicon carbide. We then discuss the proposed criteria for similar defects in other tetrahedrally coordinated semiconductors.