A method of manufacturing a germanium-on-insulator substrate is disclosed, comprising: (i) doping a first portion of a germanium layer with a first dopant to form a first electrode, the germanium layer arranged with a first semiconductor substrate; (ii) forming at least one layer of dielectric material adjacent to the first electrode to obtain a combined substrate; (iii) bonding a second semiconductor substrate to the layer of dielectric material and removing the first semiconductor substrate from the combined substrate to expose a second portion of the germanium layer with misfit dislocations; (iv) removing the second portion of the germanium layer to enable removal of the misfit dislocations and to expose a third portion of the germanium layer; and (v) doping the third portion of the germanium layer with a second dopant to form a second electrode. The electrodes are separated from each other by the germanium layer, and the first dopant is different to the second dopant.