Defect creation by 10-keV electron irradiation in phosphorous-doped a -Si:H

Changes in gap state distribution due to defects induced by different doses of 10-keV electrons in phosphorous-doped a-Si:H are reported. These defects have been observed qualitatively by electron beam writing. Patterns thus generated were read by electron beam induced current (EBIC). The increased local recombination in the area results in the decrease of EBIC current due to the increased defect density. Shift in the Fermi level position after electron irradiation was observed from the measurement of conductivity with temperature. Deep level transient spectroscopy (DLTS) was used to study the changes in gap states for the different electron dose. It was observed that irradiation causes the generation of additional defects which alter the gap state distribution in the n-type material over a broad range of energies. Creation of defects having activation energies around 0.55 eV below the conduction band was prominent although the formation of dangling bonds which results in increase in states around 0.7 eV is observed. These defects act as nonradiative recombination centers as suggested from the photoluminescence results which show a decrease in the 0.85 photoluminescence peak intensity. The contrast produced in the electron beam writing could be annealed out at 150 °C, indicating the metastability of the defects, which was also confirmed by the DLTS, photoluminescence, and dark conductivity measurements.