Photovoltaic effect in thin Bi12GeO20 films

Experimental results from a study of the photovoltaic properties of thin film Bi12GeO20 produced by reactive sputtering of a composite Bi-Ge target in a chamber with a planar magnetron are presented. The specimens were examined as examples of crystals with a sillenite structure used in electrooptic devices. Textured films manufactured at temperatures of 600 C were studied on a sapphire substrate. Films 1.5-2 microns thick were illuminated with laser light at 441.6 nm. Determinations were made of the photovoltaic current dependence on the angle between the light polarization plane and the plane direction. A pulsed laser was used to predict the lifetime of the current in the cells, which reached 1/1,000,000 sec, compared to single crystal lifetimes of 1 /10,000-1/100,000. The polarization dependence of the photocurrent is concluded to be a good method of assessing the orientation of the crystallographic axes.