Photoconductive detection of vibronic states at semiconductor interfaces and thin films

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Local vibrational mode (LVM) spectroscopy is a tool that supplies a wealth of information about the microscopic structure of impurities and defects embedded in host semiconductors. At present, IR absorption is an experimental technique of choice providing important insight into vibrational states of defect complexes. Unfortunately, its use is severely restricted to those impurities whose vibrational frequencies are decoupled from other elementary excitations in solids. Another drawback of the IR absorption is a relatively low sensitivity, which hinders its application on thin films and semiconductor interfaces. In this project we will develop photoconductive approach to investigate vibrational motion of impurities and defects in semiconductors which occur in the highly absorbing spectral regions inaccessible for IR absorption and/or positioned at semiconductor interfaces and thin films. This technique will be applied to probe LVMs of those defects which were predicted by theory or are suggested by experiment but where the chemical composition, microscopic structure, and/or electrical activity remain unknown.