Ultralarge capacitance-voltage hysteresis and charge retention characteristics in metal oxide semiconductor structure containing nanocrystals deposited by ion-beam-assisted electron beam deposition
Y. Kim et al., Ultralarge capacitance-voltage hysteresis and charge retention characteristics in metal oxide semiconductor structure containing nanocrystals deposited by ion-beam-assisted electron beam deposition, APPL PHYS L, 78(7), 2001, pp. 934-936
Amorphous silicon films are deposited by ion-beam-assisted electron beam de
position and subsequently oxidized by a rapid thermal oxidation process. Th
e oxidized film contains a large density of nanocrystals specifically local
ized at a certain depth from the Si/SiOx interface, whereas no evidence of
nanocrystals is found for oxidized films deposited without ion beam assista
nce. Such a marked contrast resulted from the enhancement of nucleation rat
e by ion beam irradiation. The metal-oxide-semiconductor structure utilizin
g the film shows an ultralarge capacitance-voltage hysteresis whose width i
s over 20 V. In addition capacitance-time measurement shows a characteristi
c capacitance transient indicating nondispersive carrier relaxation. The re
tention time shows a dependence on applied bias and the maximum time of sim
ilar to 70 s is obtained near midgap voltage. The retention time dependence
on applied bias and large capacitance-voltage hysteresis are attributed to
direct tunneling of trapped charges in the deep traps of nanocrystals to t
he interface states. (C) 2001 American Institute of Physics.