Physics with Chemically and Isotopically Pure Semiconductors

Chemically and isotopically pure semiconductors offer a wealth of interesting physics. We review a number of impurity complexes which were discovered in ultra-pure germanium. They have led the way to the widely pursued studies of hydrogen in numerous semiconductors. Isotope related effects and processes include neutron transmutation doping, a technique used for a number of silicon and germanium devices: isotopically pure and deliberately mixed crystals of germanium have been grown recently and have been used to study the dependence of the indirect bandgap and phonon properties on the mass and mass disorder of the nuclei. The large number of stable isotopes of the various semiconductors present a great potential for basic and applied studies. Semiconductor isotope engineering may become a reality because of the new economic and political world order.