Nature of gap states in chalcogenide semiconductors Ge_xSe_1-x is studied by combining X-ray photoelectron (XPS) and absorption (NEXAFS) spectroscopy with photoconductivity (PC) and internal photoemission (IPE) measurements at the semiconductor/insulator interface. It is shown that studied Ge_xSe_1-x layers are heterogeneous composite-like matrices and the gap states determining electron transport originate from formation of homopolar Ge-Ge bonds. Nanoscale phase separation effect is revealed manifesting in redistribution of GeSe₂ and GeSe networks, respectively, with increase of Ge content with predominant contribution of GeSe.