Vertical geometry light emitting diode with group III nitride active layer and extended lifetime

A light emitting diode (LED) having an extended light emitting lifetime, the LED comprising:

• a conductive silicon carbide substrate;
• a conductive buffer layer on said silicon carbide substrate and selected from the group consisting of gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having the formula A.sub.x B.sub.1-x N, where A and B are Group III elements and where x is zero, one, or a fraction between zero and one, quaternary Group III nitrides having the formula A.sub.x B.sub.y C.sub.1-x-y N where A, B, and C are Group III elements;
• x and y, are zero, one, or a fraction between zero and one, and 1 is greater than (x+y), and alloys of silicon carbide with such ternary Group III nitrides;
• a first Group III nitride layer formed on said buffer layer, said first Group III nitride layer having a first conductivity type;
• a second Group III nitride layer formed on said first Group III nitride layer, said second Group III nitride layer having a second conductivity type so that said first and second Group III nitride layers form a p-n junction device;
• said first and second Group III nitride layers forming a heterostructure;
• an ohmic contact formed on said second Group III nitride layer;
• and
• a second ohmic contact formed on said silicon carbide substrate so that a current supplied across said first and second ohmic contacts to the p-n junction device produces a high light intensity output therefrom.

A light emitting diode that emits in the blue portion of the visible spectrum and that is characterized by an extended lifetime, said light emitting diode comprising:

• a conductive silicon carbide substrate;
• an ohmic contact to said silicon carbide substrate;
• a conductive buffer on said substrate, said buffer comprising
• a first layer upon said substrate formed of a graded composition of silicon carbide aluminum gallium nitride in which the portion adjacent the substrate is substantially entirely silicon carbide and the portion furthest from the substrate is substantially entirely aluminum gallium nitride with the portions therebetween being progressively graded in content from predominantly silicon carbide to predominantly aluminum gallium nitride;
• and
• a second layer upon said first layer and formed of a graded composition of aluminum gallium nitride;
• and
• a p-n junction diode structure on said buffer layer in which the p-type and n-type layers are selected from the group consisting of binary Group III nitrides and ternary Group III nitrides.

A light emitting diode (LED) having an extended light emitting lifetime, the LED comprising:

• a conductive silicon carbide substrate;
• a conductive buffer on said substrate, said buffer comprising
• a first layer upon said substrate formed of a graded composition of silicon carbide aluminum gallium nitride in which the portion adjacent the substrate is substantially entirely silicon carbide and the portion furthest from the substrate is substantially entirely aluminum gallium nitride with the portions therebetween being progressively graded in content from predominantly silicon carbide to predominantly aluminum gallium nitride;
• and
• a second layer upon said first layer and formed of a graded composition of aluminum gallium nitride;
• and
• a first Group III nitride layer formed on said second buffer layer, said first Group III nitride layer having a first conductivity type;
• a second Group III nitride layer formed on said first Group III nitride layer, said second Group III nitride layer having a second conductivity type so that said first and second Group III nitride layers form a p-n junction device;
• an ohmic contact formed on said second Group III nitride layer;
• and
• a second ohmic contact formed on said silicon carbide substrate so that a current supplied across said first and second ohmic contacts to the p-n junction device produces a high light intensity output therefrom.