A method for growing thick epitaxial layers of GaAs on orientation-patterned wafers by low-pressure hydride vapor phase epitaxy is described. For nonlinear optical applications, it is necessary to grow very thick gratings to accommodate the pump laser as it enters through the side and propagates across the patterned layer. The low-pressure method allows for rapid growth at rates well above 100 mu m/h on wafers with patterned stripes having 30-500 mu m widths. Parasitic deposition of GaAs on the reactor walls upstream of the sample can reduce the growth rate significantly after a few hours. Various techniques are described for eliminating the parasitic growth. Layers over 500 pm thick have been successfully produced during 8 h of growth. (c) 2005 Elsevier B.V. All rights reserved.