Characterization of spin-coated gallium oxide films and application as surface passivation layer on silicon

Gallium oxide films have shown a great potential as passivation layers on silicon solar cells. In this work, we employed the spin-coating method to form gallium oxide films on p-type silicon substrate as a surface passivation layer. The dependences of the structure and the surface passivation effect of the gallium oxide films on the annealing temperatures were investigated. Both Ga 3d and 2p 3/2 regions were also measured by X-ray photoelectron spectroscopy analysis to obtain the complementary information on the composition of the Ga2O3 films (versus depth). In addition, the Q(eff) polarity change and a C-V clockwise hysteresis of Ga2O3 passivated samples were also discussed in this study. The gallium oxide films underwent an amorphous-to-crystalline phase transformations as the annealing temperature was increased above 550 degrees C. With an annealing temperature increased from 450 to 850 degrees C, the thickness of an interfacial silicon oxide layer increased from 2 to 7.4 nm; the interface state density, D-it, decreased from 4.21 x 10(11) to 1.53 x 10(11) eV(-1) cm(-2) and the effective oxide charge density, Q(eff), changed from -3.7 x 10(10) to 1.1 x 10(11) cm(-2) respectively. The D-it dominated the films passivation effect of the gallium oxide films with increasing annealing temperatures. The residual gallium hydroxide can act as a hydrogen reservoir for hydrogen diffusion and the interface hydrogenation play an important role in the D-it decrease. (C) 2016 Elsevier B.V. All rights reserved.