Defects and dopants in semiconductors are important to solid-state technology and condensed matter physics. The ability to manipulate the conductivity of semiconductor materials through controlled doping has made them indispensable. This book provides a synthesis of the theory, experimental methods, and identification of impurities and intrinsic defects in semiconductors. It first presents introductory concepts and then focuses on electrical, optical, vibrational, and thermodynamic properties. The final section of the book covers characterization approaches, from measurement of electrical properties and optical spectroscopy to particle beam methods.