Normally-off and normally-on AlGaAs/GaAs heterojunction gate GaAs FETs (HJFETs) for high-speed logic applications have been fabricated with molecular beam epitaxy (MBE) and organometallic vapour phase epitaxy (OM-VPE). The best normally-off devices used MBE n-GaAs active layers and OM-VPE gate layers of p+-AlGaAs and p+-GaAs. Saturation currents followed a square law and current scaling constants were the highest on record for HJFETs, greater than 50 μA/μm-V2.