Layers of a high quality GaN and AlGaN/GaN heterostructure were grown on (111)-oriented silicon substrate by inserting several thin InN interlayers during the transition-layer growth, which turned out to be very effective in decreasing the dislocation density in the grown GaN films. The full width at half-maximum of (002) and (102) X-ray rocking curves and photoluminescence bandedge emission peak for the undoped GaN layer grown with an InN interlayer were greatly improved to 673 and 1132 arc sec and 15 meV compared to the values of 1732 and 3441 arc sec and 22 meV for those grown without an InN interlayer, respectively. The two-dimensional electron gas mobility and the carrier density for the AlGaN/GaN heterostructure were increased from 330 cm(2)/V s and 2.2x10(11)/cm(2) to 1050 cm(2)/V s and 1.5x10(13)/cm(2), respectively.