Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)




Silicon is the heart of modern semiconductor devices. The dominance of Si in semiconductor technology depends on the superior quality and properties of thermally grown SiO(,2) compared with the oxide that can be placed on any other semiconductor. For this reason, Si-SiO(,2) interface has been an interesting and important research subject for many years.;The well established quasistatic and conductance methods used in the study of the Si-SiO(,2) interface are improved by using (i) an effectively thin composite insulator, (ii) low carrier concentration substrates, and most importantly (iii) low-level illumination at a wavelength that creates electron-hole pairs. Accurate measurements of both the total density of interface states and its major components as a function of energy in the forbidden gap have been made over four decades (10('10) - 10('14) states/eV-cm('2)) due to items (i) and (ii). Item (iii) decreases the response time of the slow states (those in the lower half of the band gap for n-type samples), so the quasistatic condition is well satisfied and the conductance method can be used to study the interface states throughout the band gap on a single sample. Without illumination, the quasistatic condition is not satisfied even for ramp rates on the lower side of those used previously and complementary n- and p-type samples are needed for the conductance method.;The samples investigated have a thermally grown oxide prepared in dry oxygen. They were never exposed to H(,2) or H(,2)O at an elevated temperature. We speculate that this processing provides an abrupt Si-SiO(,2) interface. The composite gate insulator was completed by having an e-gun deposited 250(ANGSTROM) layer on LaF(,3). The resulting interface, subjected to the improved experimental method, yields a wealth of distinctive structure rather than the often-reported featureless U-shaped interface-state density.



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