We describe a method to form InAs quantum dots on GaAs by cooling an InAs film that is deposited at high substrate temperatures. The reflection high-energy electron diffraction pattern taken after deposition of 1.9 monolayers of InAs on (100) GaAs at 540 degreesC does not display the characteristic spot pattern that is seen when three-dimensional islands form on the surface. The characteristic,spot pattern appears when the sample is cooled to about 330 degreesC, indicating that the three-dimensional islands appear at this temperature. Atomic force microscopy confirms the existence of the islands. An explanation for this behavior based on an increase in intermixing at the InAs/GaAs interface is proposed.