Thin layers of GaAs, heavily doped with Sn, Si, or Be, have been incorporated into Schottky barrier diode and bulk unipolar (camel) diode structures. The effective barrier height of the Schottky diodes has been varied between 0.48 and 0.96 eV by changing the doping and thickness of the heavily doped layer adjacent to the metal contact, and camel diodes with barriers between 0.55 and 0.94 eV have also been fabricated. There is a quantitative discrepancy between the experimental and theoretical diode parameters, however, and possible explanations are discussed.