Abstract: A method for making a free-standing, single crystal, aluminum gallium nitride (AlGaN) wafer includes forming a single crystal AlGaN layer directly on a single crystal LiAlO2 substrate using an aluminum halide reactant gas, a gallium halide reactant gas, and removing the single crystal LiAlO2 substrate from the single crystal AlGaN layer to make the free-standing, single crystal AlGaN wafer. Forming the single crystal AlGaN layer may comprise depositing AlGaN by vapor phase epitaxy (VPE) using aluminum and gallium halide reactant gases and a nitrogen-containing reactant gas. The growth of the AlGaN layer using VPE provides commercially acceptable rapid growth rates. In addition, the AlGaN layer can be devoid of carbon throughout. Because the AlGaN layer produced is high quality single crystal, it may have a defect density of less than about 107cm?2.