Resonant interband tunnelling through doping barriers in homoepitaxial InSb is observed. The band structures for the chosen doping profiles are calculated self-consistently including non-parabolicity effects. A p⁺- delta p⁺-i-n⁺-i- delta p⁺-p⁺ doping structure is designed to create a two-dimensional triangular inversion well between two degenerate p-type slab layers. Holes in the p-type layer then tunnel resonantly through the two-dimensional occupied electron states of the n⁺-induced well into the collector on the other side. These structures exhibit symmetric negative differential resistance (NDR) with peak-to-valley ratios of 1.6 and peak current densities of 120 A cm^-2 at 4.2 K.