We investigated the initial stages of growth of Al films fabricated by chemical vapor deposition at 100 degrees C on GaAs(001)2x4 surfaces using the molecular precursor dimethylethylamine alane. In situ reflection high energy electron diffraction and scanning tunneling microscopy and spectroscopy, as well as ex situ atomic and lateral force microscopy, were employed for morphological analysis. Film growth was found to occur in the Volmer-Weber mode and involve islands with remarkably low z-aspect ratio (similar to 1.16). Scanning tunneling spectroscopy data on some of these islands in the early stages of growth suggest the formation of an AlAs interface phase.