Methods of manufacturing vertical semiconductor diodes using an engineered substrate

A method of forming a semiconductor diode, the method comprising:

• forming a substrate by:
• providing a polycrystalline ceramic core;
• encapsulating the polycrystalline ceramic core with a first adhesion shell;
• encapsulating the first adhesion shell with a barrier layer;
• forming a bonding layer on the barrier layer;
• and
• joining a substantially single crystal layer to the bonding layer;
• forming a buffer layer on the substantially single crystal layer;
• forming a semi-insulating layer on the buffer layer;
• forming a first epitaxial N-type gallium nitride layer on the semi-insulating layer, the first epitaxial N-type gallium nitride layer having a first doping concentration;
• forming a second epitaxial N-type gallium nitride layer on the first epitaxial N-type gallium nitride layer, the second epitaxial N-type gallium nitride layer having a second doping concentration less than the first doping concentration;
• forming an epitaxial P-type gallium nitride layer on the second epitaxial N-type gallium nitride layer;
• removing a portion of the second epitaxial N-type gallium nitride layer and a portion of the epitaxial P-type gallium nitride layer to expose a portion of the first epitaxial N-type gallium nitride layer;
• forming an anode contact on a remaining portion of the epitaxial P-type gallium nitride layer;
• and
• forming a cathode contact on the exposed portion of the first epitaxial N-type gallium nitride layer.