Electronic structure of semiconductor oxides: ${\mathrm{InPO}}_4$, In(${\mathrm{PO}}_3$${)}_3$, ${\mathrm{P}}_2$${\mathrm{O}}_5$, ${\mathrm{SiO}}_2$, ${\mathrm{AlPO}}_4$, and Al(${\mathrm{PO}}_3$${)}_3$

The electronic structure of InP oxides, AlP oxides, and ${\mathrm{SiO}}_2$ is investigated both experimentally and theoretically. X-ray-photoemission valence-band spectra are compared with tight-binding calculations in order to analyze the different contributions to each spectrum. Oxygen-oxygen interactions must be included to explain the experimental features. A systematic analysis of the ${\mathrm{SiO}}_2$-${\mathrm{AlPO}}_4$-${\mathrm{InPO}}_4$ and ${\mathrm{InPO}}_4$-In(${\mathrm{PO}}_3$ ${)}_3$-${\mathrm{P}}_2$ ${\mathrm{O}}_5$ family evolution is made. The nature of the atomic states participating in the valence-band spectra is identified. The role of In and Al atoms in the valence band is analyzed, and we conclude that their influence is not negligible in the cases of ${\mathrm{InPO}}_4$ and ${\mathrm{AlPO}}_4$. We can distinguish two types of oxygen atoms in some oxides: ${\mathrm{O}}_{\mathrm{b}}$ bridging different ${\mathrm{PO}}_4$ tetrahedra, and ${\mathrm{O}}_{\mathrm{nb}}$ only linked to one P atom. We conclude that the presence or absence of ${\mathrm{O}}_{\mathrm{b}}$ has observable consequences in the XPS valence-band spectra.