Defect studies with isotopically designed semiconductors

Most semiconductors consist of elements which are made up of a number of stable isotopes. Access to highly enriched isotopes in macroscopic quantities opens up new and unique possibilities for semiconductor defect research. The use of isotope mass sensitive effects including the frequencies of local vibrational modes, nuclear spin, as well as nuclear cross sections for thermal neutron capture for the study of native and impurity defects will be reviewed and illustrated with relevant examples. First, the extreme simplification of the local vibrational mode (LVM) spectrum of oxygen in Ge obtained through isotopic control of the Ge host lattice will be reviewed with emphasis on the spectral features which became accessible through this simplification. Second, self and impurity diffusion studies with isotopically designed multilayer structures will be discussed. Third, the authors will discuss defect and dopant investigations based on the neutron transmutation doping (NTD) technique