In this article we investigate the growth of GaAs on two different vicinal surfaces of Ge (100), cut 6degrees off the (100) plane toward the (110) plane or toward the (111) plane. Both substrates exhibit evidence of a regular array of double steps. Ge substrates and GaAs films are characterized with low energy electron diffraction, low temperature photoluminescence, scanning tunneling microscopy, electron channeling, and scanning electron microscopy. GaAs grown on wafers cut toward the (111) plane exhibits high quality as compared to reference GaAs samples, whereas GaAs grown on wafers cut toward the (110) plane displays clear evidence of three-dimensional growth and low crystallinity. (C) 2004 American Vacuum Society.