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

Abstract

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 Qeff 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 °C. With an annealing temperature increased from 450 to 850 °C, the thickness of an interfacial silicon oxide layer increased from 2 to 7.4 nm; the interface state density, Dit, decreased from 4.21 × 1011 to 1.53 × 1011 eV−1 cm−2 and the effective oxide charge density, Qeff, changed from −3.7 × 1010 to 1.1 × 1011 cm−2 respectively. The Dit 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 Dit decrease.