InAlGaN/AlN/GaN high electron mobility transistors (HEMTs) on a silicon substrate with high electron mobility is demonstrated for the first time. The InAlGaN/AlN/GaN heterostructures has a high electron mobility of 1540 cm(2) V-1 s(-1) and low sheet resistance of 228.2 omega sq(-1) by inserting a thin GaN interlayer (IL) between InAlGaN and AlN layers. The experimental results demonstrate that an optimized GaN IL contributes to a better atomic arrangement of the InAlGaN barrier layer in the InAlGaN/GaN HEMTs and results in better electron transport properties for the device. The InAlGaN/GaN device with 170 nm gate and 2 mu m source-to-drain distance shows a high maximum current density (I-max) of 1490 mA mm(-1) and high transconductance (g(m)) of 401 mS mm(-1). Such results demonstrate the potential of adopting InAlGaN/GaN heterostructure on silicon for low cost mm-wave applications in the future.