Integrated heterostructures of Group III-V nitride semiconductor materials including epitaxial ohmic contact, non-nitride buffer layer and methods of fabricating same

An n-on-p integrated heterostructure device of Group III-V nitride compound semiconductor materials, comprising:

• a conductive substrate comprising p-type monocrystalline silicon carbide;
• a first layer comprising p-type aluminum nitride or p-type aluminum gallium nitride on said substrate;
• a second layer comprising p-type aluminum gallium nitride on said first layer;
• a third layer comprising p-type aluminum gallium nitride on said second layer;
• said second layer being continuously graded such that the concentration of gallium relative to aluminum increases continuously from adjacent said first layer to adjacent said third layer, said second layer forming an ohmic contact between said first layer and said third layer;
• an active device region on said third layer;
• a fourth layer comprising n-type aluminum gallium nitride on said active device region, opposite said third layer;
• a fifth layer comprising n-type aluminum gallium nitride on said fourth layer;
• and
• a sixth layer comprising n-type gallium nitride or aluminum gallium nitride on said fifth layer;
• said fifth layer being continuously graded such that the concentration of gallium relative to aluminum increases continuously from adjacent said fourth layer to adjacent said sixth layer, said fifth layer forming an ohmic contact between said fourth layer and said sixth layer.

An n-on-p integrated heterostructure device of Group III-V nitride compound semiconductor materials, comprising:

• a substrate comprising p-type monocrystalline silicon carbide;
• a first layer comprising p-type aluminum nitride or p-type aluminum gallium nitride on said substrate;
• a second layer comprising a multiple quantum well on said first layer;
• a third layer comprising p-type aluminum gallium nitride on said second layer;
• wherein said first layer comprises p-type Al.sub.1-x Ga.sub.x N, wherein said third layer comprises p-type Al.sub.1-z Ga.sub.z N where x is less than z and where x can be zero, and wherein said second layer multiple quantum well comprises alternating layers of p-type Al.sub.1-x Ga.sub.x N and p-type Al.sub.1-z Ga.sub.z N, wherein the thickness of said layers of Al.sub.1-x Ga.sub.x N decreases from adjacent said first layer to adjacent said third layer, said second layer multiple quantum well forming an ohmic contact between said first layer and said third layer;
• an active device region on said third layer;
• a fourth layer comprising n-type aluminum gallium nitride on said active device region, opposite said third layer;
• a fifth layer comprising a multiple quantum well on said fourth layer;
• and
• a sixth layer comprising n-type gallium nitride or aluminum gallium nitride on said fifth layer;
• wherein said fourth layer comprises n-type Al.sub.1-x Ga.sub.x N, wherein said sixth layer comprises n-type Al.sub.1-z Ga.sub.z N where x is less than z and where x can be zero, and wherein said fifth layer multiple quantum well comprises alternating layers of n-type Al.sub.1-x Ga.sub.x N and n-type Al.sub.1-z Ga.sub.z N, wherein the thickness of said layers of Al.sub.1-x Ga.sub.x N decreases from adjacent said fourth layer to adjacent said sixth layer said fifth layer multiple quantum well forming an ohmic contact between said fourth layer and said sixth layer.

A negative-electron-affinity (NEA) device of Group III-V nitride compound semiconductor materials, comprising:

• a conductive substrate comprising p-type monocrystalline silicon carbide;
• a first layer comprising p-type aluminum nitride or p-type aluminum gallium nitride on said conductive substrate;
• a second layer comprising p-type aluminum gallium nitride on said first layer;
• and
• a third layer comprising p-type aluminum gallium nitride on said second layer;
• said second layer being continuously graded such that the concentration of gallium relative to aluminum increases continuously from adjacent said first layer to adjacent said third layer, said second layer forming an ohmic contact between said first layer and said third layer.

A negative-electron-affinity (NEA) device of Group III-V nitride compound semiconductor materials, comprising:

• a conductive substrate comprising p-type monocrystalline silicon carbide;
• first layer comprising p-type aluminum nitride or p-type aluminum gallium nitride on said conductive substrate;
• a second layer comprising a multiple quantum well on said first layer;
• a third layer comprising p-type aluminum gallium nitride on said second layer;
• wherein said first layer comprises p-type Al.sub.1-x Ga.sub.x N, wherein said third layer comprises p-type Al.sub.1-z Ga.sub.z N where x is less than z and where x can be zero, and wherein said multiple quantum well comprises alternating layers of p-type Al.sub.1-x Ga.sub.x N and p-type Al.sub.1-x Ga.sub.z N, wherein the thickness of said layers of Al.sub.1-x Ga.sub.x N decreases from adjacent said first layer to adjacent said third layer said multiple quantum well forming an ohmic contact between said first layer and said third layer.