An AlGaN based high electron mobility transistor (HEMT) structure was grown on 200 mm diameter (111) silicon by metal organic chemical vapour deposition (MOCVD). The growth was initiated by an AlN layer directly on Si. A level wafer temperature profile (±5 °C) was achieved throughout the process by use of a variable concentric heater profile. This was realised by monitoring the wafer temperature profile of the entire wafer in-situ using pyrometry. Excellent uniformity, σ ∼ 1%, of each component layer was achieved across the wafer which was crack and slipline free material except for the outer 2 mm. This demonstrates the potential for growth of GaN based devices on 200 mm. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)