High-quality lateral epitaxial overgrown GaN films on (00▪1) sapphire substrates were grown by a commercial MOCVD system. A study was made, of threading dislocations in the films, by wet etching, HCl vapor etching and scanning electron microscopy. Scanning electron microscopic images of films etched in HCl vapor and molten KOH gave appreciably different etch-pit densities in various regions of lateral epitaxial overgrown films. This confirmed that HCl vapor etching could reveal 3 kinds of threading dislocation, while molten KOH wet etching could reveal only pure screw threading dislocations. In regions above windows, the threading dislocation density was high (about 3 x 108/cm2) and edge threading dislocations were in the majority. Material was almost free of threading dislocations in the region above masks. Only in the middle region above mask were there some threading dislocations (including all 3 kinds), and edge threading dislocations were in the majority.

Etch-Pits and Threading Dislocations in Thick LEO GaN Films on Sapphire Grown by MOCVD. M.Lu, X.Chang, H.Z.Fang, Z.J.Yang, H.Yang, Z.L.Li, Q.Ren, G.Y.Zhang, B.Zhang: Physica Status Solidi C, 2004, 1[10], 2438-40