This research involves the application of nuclear magnetic resonance (NMR) to the study of specific classes of defects in semiconducting materials. Studies of hydrogen complexed with dopants will be carried out in collaboration with industrial partners concerned about the effects of hydrogen introduced into semiconductors during processing and device fabrication. The program will focus on three specific goals: The location and dynamics of hydrogen complexed with dopants in gallium arsenide and silicon semiconductors will be determined using double resonance techniques to selectively probe the complex. The identification and characterization of thermally generated paramagnetic defects in gallium arsenide and related materials will be undertaken using in situ high temperature NMR techniques. The sites occupied by indium impurities and characterization of vacancy-impurity complexes in II-VI materials, including correlation of the results with concurrent studies of these defects using perturbed angular correlation techniques, will be studied. %%% The performance of semiconducting materials used in electronic devices is dominated by the effects of impurities and crystalline defects. These effects can be constructive, as in the case of "doping," where specific impurities can be used to obtain desired electrical properties. On the other hand, the incidental introduction of hydrogen into semiconductors from organic materials used during material processing can be highly deleterious. Hydrogen can "passivate," or neutralize dopant impurities, rendering them electrically inactive. Undesired and poorly characterized defects in semiconducting materials lead to poor yields and device failures. Exploitation of well-understood defects holds the potential for development of advanced semiconducting materials with improved characteristics. Nuclear magnetic resonance (NMR) will be used to characterize the location and motional properties of defects on the atomic scale in various materials of technological importance including silicon, gallium arsenide, and cadmium telluride. This technique is highly selective and is capable of probing individual chemical species in specific locations in a crystalline semiconductor. Recent improvements in NMR techniques and the use of high field superconducting magnets make it possible to investigate certain defect species at concentrations as low as a few tens of parts per million.
