Tunneling current measurements onn‐type &dgr;‐doped Si(100) structures were carried out, with sheet doping concentrations ranging from ∼4×1012to 2.0×1013cm−2at 4 K. All samples have been grown by using a low‐energy ion source for antimony doping in a silicon molecular beam epitaxy system. From analysis ofdI/dVgand (dI/dVg)/ (I/Vg) spectra, tunneling associated with quantized electron subbands is identified. The subband energy positions relative to the equilibrium Fermi levelEF0under zero bias were determined from the tunneling current measurements as a function of the sheet doping concentration. Self‐consistent theoretical calculations of the electronic structure of &dgr; layers have been performed, and good agreement between theory and experiment is obtained for most structures in the tunneling spectra.