on foreign materials. These problems could be alleviated if a true GaN substrate were to become available, allowing homoepitaxial growth. The preparation of 50 mm diameter boules of γ-LiAlO₂ from the melt will be discussed, including wafer preparation. Growth of thick (300-400um)GaN layers on the γ-LiAlO₂ wafers willbe presented. The GaN is deposited by the halide vapour phase epitaxy (HVPE) method. Characteristics of these 50 mm diameter wafers are explained in detail. Much progress has been made, but several problems remain to be overcome.