Electron transport properties of double delta-doped GaAs structures based on high electron mobility single delta-doped layers with a sheet concentration of3×1012 cm−2have been investigated for spacer thicknesses up to 1100 Å at 77 and 300 K. At an optimized spacer thickness of about 200 Å, a maximum in conductivity is observed, which exceeds the conductivity of a single delta-doped layer with the same total concentration by 30&percent; and 20&percent; at 300 and 77 K. The mobility and concentration as a function of spacer thickness are also presented and analyzed. ©1998 American Institute of Physics.