  The structure of (GeS$_2$)$_{0.75}$(Ga$_2$S$_3$)$_{0.25}$ and
(GeS$_2$)$_{0.83}$(Ga$_2$S$_3$)$_{0.17}$ glasses was investigated by Raman
scattering, high energy X-ray diffraction and extended X-ray absorption fine
structure (EXAFS) measurements at the Ga and Ge K-edges. The reverse Monte
Carlo simulation technique (RMC) was used to obtain structural models
compatible with diffraction and EXAFS datasets. It was found that the
coordination number of Ga is close to four. While Ge atoms have only S
neighbors, Ga binds to S as well as to Ga atoms showing a violation of chemical
ordering in GeS$_2$-Ga$_2$S$_3$ glasses. Analysis of the corner- and
edge-sharing between [GeS$_{4/2}$] units revealed that about 30% of germanium
atoms participate in the edge-shared tetrahedra.
