Boron delta-doped diamond structures have been synthesized using microwave plasma chemical vapor deposition, and fabricated into FET and gated Hall bar devices for assessment of the electrical characteristics. A detailed study of variable temperature Hall, conductivity and field-effect mobility measurements was completed. This was supported by Schrödinger-Poisson and relaxation time calculations based upon application of Fermi's golden rule. A two carrier-type model was developed with an activation energy of ~0.2 eV between the delta layer lowest subband with mobility ~1 cm 2 /Vs and the bulk valence band with high mobility. This new understanding of the transport of holes in such boron delta-doped structures has shown that although Hall mobility as high as 900 cm 2 /Vs was measured at room temperature, this dramatically overstates the actual useful performance of the device.a Corresponding author