Sputter deposition of low‐resistivity (0.02 &OHgr; cm) layers of SnO2‐doped In2O3onto AlxGa1−xAs results in heterojunction barriers to eithern‐ orp‐type material. Low‐loss AlxGa1−xAs waveguides with SnO2‐In2O3cladding have been fabricated. Their propagation properties can be efficiently modulated by means of the linear electro‐optic effect. Phase shifts for TE modes of 160 deg/V cm were measured at a wavelength &lgr;=0.9 &mgr;m.