Influence of substrate polarity on the low-temperature (LT)-GaN buffer layer growth on GaAs (111)A and (111)B surfaces was investigated for the two-step growth of GaN on GaAs (111) substrates. Two growth methods were studied: metalorganic hydrogen chloride vapor phase epitaxy (MOHVPE) using gallium chloride (GaCl) as the gallium (Ga) source and conventional metalorganic vapor phase epitaxy (MOVPE) using trimethylgallium (TMG) as the Ga source. A 50-nm-thick LT-GaN buffer layer grown on a GaAs (111)A surface consisted of an amorphous-like matrix including oriented crystallites in it, whereas that grown on a GaAs (111)B surface mainly consisted of oriented crystallites. After heating process up to 1000degreesC in the presence of NH3, the GaAs (111)B surface covered with the LT-GaN buffer layer seriously deteriorated due to etching of GaN during the heating process. On the contrary, the LT-GaN buffer layer on GaAs (111)A surface crystallized to highly oriented GaN grains during the heating, and no deterioration of GaAs substrate occurred. These results are attributed to the difference in etching rate of GaN related to the lattice polarity of GaN on GaAs substrate. Same results were obtained for both MOHVPE and MOVPE. (C) 2002 Elsevier Science B.V. All rights reserved.