Optical modulation spectroscopy of dangling bonds in a-Si: H

Abstract
Optical modulation spectroscopy in a-Si:H at room temperature has been studied for six samples, deposited at different substrate temperatures T s and hence containing different amounts of hydrogen. The experimental results can be described with one photoinduced absorption and one photoinduced bleaching term. The transition energies are independent of T s so that it may be concluded that mainly dangling bonds and the conduction band are involved. The negatively charged dangling bond D- is situated 0·85 eV below the conduction-band edge. The neutral D° lies 1·25 eV below that edge. It can be argued that these values are not necessarily in conflict with the experimental value (0·75 eV) for the dark-current activation energy.