Is a potentially useful semiconductor which can have either the sphalerite structure or the chalcopyrite structure with no tetragonal distortion . We have grown on various orientations of by liquid phase epitaxy and found that the best growth occurs on {110} surfaces. Double‐crystal x‐ray diffraction measurements indicate that these {110} layers have a lattice constant of 5.6507Å, while {111} As layers grown under identical conditions have a lattice constant of 5.6532Å, which matches to within . Back reflection Laue patterns show that the {110} layers are chalcopyrite, while the {111} As layers are sphalerite. The Laue patterns also indicate that the {110} epitaxy is mixed with the c‐axis out of the growth plane. A possible explanation for these results is that the {110} surfaces in liquid phase epitaxy reconstruct into chalcopyrite‐like chains in the [001] direction, while the {111} As surfaces do not. This would promote the formation of chalcopyrite with antiphase boundaries on {110} surfaces.