Characterisation of electrically active impurities using DLTS and related techniques

Measurements which examine the emission and capture of carriers from impurities and structural defects in semiconductors form an important class of analysis techniques the best known of which is deep level transient spectroscopy, (DLTS). This review discusses the fundamental difference between methods which measure the chemical properties of an impurity and techniques like DLTS which are sensitive to the lattice siting of the impurity and whether it is complexed with other species of defect. Interesting features of DLTS-related techniques are their high sensitivity and ability to provide quantitative information particularly in terms of absolute values of concentration. The broad spectral features obtained from deep level measurements do not on their own allow definitive identification of the defect species involved but the unique strength of the method in being able to assess the significance of a detected defect in terms of its consequence in devices is discussed. In particular, the assessment of nonradiative recombination and the relevant defect parameters are considered in terms of what the measured values really tell us.