We have observed a degradation in the epitaxial layer quality of AlInAs when it is grown by molecular beam epitaxy at a substrate temperature of about 400°C compared to that for alloys grown at 300 and 500°C. The barrier height and ideality factor of Ti-and Au-AlInAs Schottky diodes also exhibit large spatial variations and dependence on growth temperatures. The observed phenomena can be explained by invoking a kinetic growth model or thermodynamic phase equilibria in the growing surface layer.