Undoped 28 nm AlGaN on 1 mum GaN was grown by MOVPE for high power microwave HFETs. Non-destructive methods for rapid characterisation of the layers are described. Double contact mercury probe capacitance voltage measurements gave valuable information on AlGaN layer leakage, thickness and quality, but only gave an estimate of the carrier concentration and pinch-off voltage due to the absence of an ohmic contact to the 2DEG layer. A noncontact resistivity mapping system gave accurate average sheet resistance, but underestimated the cross-wafer variation. Crown Copyright