PERSISTENT PHOTOCONDUCTIVITY IN SIMOX FILM STRUCTURES

Photoinduced transient spectroscopy (PITS) was used to measure the persistent photoconductive (PPC) response in n-type separation by implanted oxygen (SIMOX) film resistors. A broadband, single-shot, flashlamp-pumped dye laser pulse was used to photoexcite interband electrons in the film, and the excess carrier population decay was measured at temperatures in the 60-220-K range. The PPC signals exhibit nonexponential character and the conductivity transients are recorded as a function of temperature for variable periods up to 30 s. The photoconductive data are analyzed by using the Queisser and Theodorou potential barrier model, and a logarithmic time-decay dependence is confirmed for the first time in SIMOX material. The hole-trap density at the conductive-film-buried-silica interface is calculated to be in the high 10 15 cm-3 to low 1016 cm-3 range. The sensitivity of PITS is demonstrated to be appropriate for characterization of the SIMOX interface structure and for material qualification.