Bipolar diode

A semiconductor diode, comprising

• a first doped region of a first conductivity type;
• an intermediate drift region of the first conductivity type doped with a dopant concentration less than that in the first region;
• a second doped region of a conductivity type opposite to the first conductivity type, sandwiching the intermediate drift region between the first and second regions, wherein the second doped region forms a bipolar diode structure with the intermediate and first regions;
• and
• a plurality of field electrodes for depleting the intermediate drift region under reverse bias, the plurality of field electrodes being arranged in a plurality of closely spaced insulated trenches extending laterally across the semiconductor diode and extending through the second and intermediate regions, wherein the first doped region and intermediate drift region are formed of a first semiconductor material and the second doped region is a thin region formed of a second semiconductor material having a lower band-gap than the first semiconductor material, the thickness of the thin second region and the lattice mismatch of the first and second semiconductor materials being selected such that the level of mechanical stress remains below a level at which misfit dislocations are formed.