Recently high and persistent spontaneous buildup of a surface potential (SP) upon vacuum deposition of tris (8-hydroxyquinolinato) aluminum (III) (Alq(3)) which is widely used for organic light emitting devices, on a gold substrate under dark condition (28 V for 560-nm-thick Alq(3) film) has been reported. The removal of the giant surface potential by visible light irradiation has also been reported. These properties of Alq(3) film suggest potential applications to various organic devices such as memory. In this study, we investigated the retention time of the giant potential and the mechanism of the light-induced depolarization in order to discuss the feasibility of the device applications. The observed decay rate of the surface potential in vacuum condition was roughly 10% loss in 10 years, which is enough for memory devices. As to the decay rate by light-irradiation, the observed rate was successfully reproduced by a theoretical simulation based on the photo-induced randomization of oriented Alq(3) molecules. (C) 2004 Published by Elsevier B.V.