A majority carrier diode is described in which current flow is controlled by a potential hump in the bulk of a semiconductor. In order to make a diode of good quality on an n-type substrate a highly doped p+ region is used to form a potential barrier between a degenerate n-type region and the substrate. Silicon diodes with ideality factors <2 have been made using ion implantation at low energies. The current voltage characteristics of these diodes and their switching behaviour were found to be consistent with majority carrier transport over a potential barrier.