DEFECTS IN SEMICONDUCTORS - SOME FATAL, SOME VITAL

The role of defects as essential entities in semiconductor materials i s reviewed. Early experiments with semiconductors were hampered by the extreme sensitivity of the, electronic properties to minute concentra tions of impurities. Semiconductors were viewed as a family of solids with irreproducible properties. Scientific efforts overcame this idios yncrasy and turned the art of impurity doping into today's exceedingly useful and reproducible technology that is used to control precisely electrical conductivity, composition, and minority carrier lifetimes o ver wide ranges. Native defects such as vacancies and self-interstitia ls control basic processes, foremost self- and dopant diffusion. The s tructural properties of dislocations and higher dimensional defects ha ve been studied with atomic resolution, but a thorough theoretical und erstanding of their electronic properties is incomplete. Reactions bet ween defects within the host Lattices are increasingly better understo od and are used for gettering and electrical passivation of unwanted i mpurities. Metastable defects such as DX centers and the EL2-related a rsenic antisite are briefly discussed. The recent development of isoto pically controlled semiconductors has created new research opportuniti es in this field.