A technique for fabricating controlled Schottky barrier heights to GaAs over the entire band gap is demonstrated. Thin, highly doped semiconductor layers at the metal-semiconductor interface allowed the reproducible control of the effective barrier height on n-type GaAs from near zero (i.e., ohmic behavior at 300 K) to 1.33 eV (the band gap equals 1.43 eV at 300 K) with diode ideality factors 1.02≤n≤1.21. Molecular-beam epitaxy was used to grow GaAs epitaxial layers with in situ deposited Al metal layers, resulting in diodes with nearly ideal electrical and structural characteristics. Electrical characterization by current-voltage (I-V) and capacitance-voltage (C-V) techniques, models for these I-V and C-V characteristics, and structural characterization by high resolution transmission electron microscopy lattice images are presented. Implications of this work for models of Schottky barrier formation are discussed, as well as some applications for these ‘‘engineered Schottky barrier diodes.’’