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The proposal, processing and performance of n þ GaN/InGaN/AlGaN/GaN normally-off metal-oxide-semiconductor (MOS) HEMTs with a recessed 2-mm long gate/8-mm source-drain distance are presented. It is shown that by using a negative polarization charge at the InGaN/AlGaN interface together with 10-nm thick Al 2 O 3 gate insulation, a threshold voltage V T increases by 3.6 V reaching a value of $1.6 V. Moreover, the combination of the gate recessing through the n þ GaN cap and gate insulation lead to an invariant maximal drain current of about 0.25 A mm À1 , as well as decreased gate leakage current in the order of $10 À9 A mm À1 . Analytical equations explain the predictive setting of V T up to 7 V with the oxide thickness t ox increase, if holes compensate the negative polarization charge. By applying t ox ¼ 30 nm a V T $ 3 V was obtained; p-doping of the cap/barrier layers is suggested to reach the theoretically predicted scalability.