InGaN/GaN based blue LEDs with 2-μm-thick crack-free GaN buffer layers were successfully grown and fabricated on patterned Si (1 1 1) substrates. The patterns on the substrates include 340 μm×340 μm square islands, separated by 3-μm deep and 20 μm wide trenches, along the 〈 1 over(l, -) 0 〉 and 〈 1 1 over(2, -) 〉 crystalline orientations. In addition to using the patterned growth technique, thin AlN and SiN interlayers grown at high temperatures were also employed to partially release the residual stress and to further improve the crystalline quality. Blue LEDs of 300×300 μm fabricated on the islands, without thinning and packaging, exhibited a high output power of around 0.7 mW at a drive current of 20 mA. Compared to III-nitride LEDs grown on sapphire substrates, the same LED structures grown on patterned Si substrates showed a few nm of red shift in emitting wavelength, suggesting some residual stress of GaN on patterned Si. © 2006 Elsevier B.V. All rights reserved.