GaN-based Schottky barrier diode with algan surface layer
A Schottky diode and method of fabricating the Schottky diode using gallium nitride (GaN) materials is disclosed. The method includes providing an n-type GaN substrate having first and second opposing surfaces. The method also includes forming an ohmic metal contact electrically coupled to the first surface, forming an n-type GaN epitaxial layer coupled to the second surface, and forming an n-type aluminum gallium nitride (AlGaN) surface layer coupled to the n-type GaN epitaxial layer. The AlGaN surface layer has a thickness which is less than a critical thickness, and the critical thickness is determined based on an aluminum mole fraction of the AlGaN surface layer. The method also includes forming a Schottky contact electrically coupled to the n-type AlGaN surface layer, where, during operation, an interface between the n-type GaN epitaxial layer and the n-type AlGaN surface layer is substantially free from a two-dimensional electron gas.
1. A method of fabricating a Schottky diode using gallium nitride (GaN) materials, the method comprising:
providing an n-type GaN substrate having a first surface and a second surface, the second surface opposing the first surface;
forming an ohmic metal contact electrically coupled to the first surface of the n-type GaN substrate;
forming an n-type GaN epitaxial layer coupled to the second surface of the n-type GaN substrate, wherein the n-type GaN epitaxial layer comprises a polar GaN material;
forming an n-type aluminum gallium nitride (AlGaN) surface layer coupled to the n-type GaN epitaxial layer; and
forming a Schottky contact electrically coupled to the n-type AlGaN surface layer,
wherein, during operation, an interface between the n-type GaN epitaxial layer and the n-type AlGaN surface layer is substantially free from a two-dimensional electron gas.
2. The method of claim 1 , wherein the thickness of the n-type AlGaN surface layer is between 0.5 nm and 15 nm.
3. The method of claim 2 , wherein the thickness of the n-type AlGaN surface layer is between 1 nm and 3 nm.
4. The method of claim 1 , wherein the n-type AlGaN layer is graded with a graded aluminum mole fraction of the n type AlGaN surface layer and is graded as a function of thickness.
5. The method of claim 4 , wherein the aluminum mole fraction increases as a distance to the Schottky contact decreases.
6. The method of claim 1 , wherein the AlGaN surface layer has a thickness which is less than a critical thickness, wherein the critical thickness is determined based on an aluminum mole fraction of the AlGaN surface layer.
7. A semiconductor device comprising:
an n-type GaN substrate having a first surface and a second surface, the second surface opposing the first surface;
an ohmic metal contact electrically coupled to the first surface of the n-type GaN substrate;
an n-type GaN epitaxial layer coupled to the second surface of the n-type GaN substrate, wherein the n-type GaN epitaxial layer comprises a polar GaN material;
an n-type aluminum gallium nitride (AlGaN) surface layer coupled to the n-type GaN epitaxial layer; and
a Schottky contact electrically coupled to the n-type AlGaN surface layer,
wherein, during operation, an interface between the n-type GaN epitaxial layer and the n-type AlGaN surface layer is substantially free from a two-dimensional electron gas.
8. The device of claim 7 , wherein the thickness of the n-type AlGaN surface layer is between 0.5 nm and 15 nm.
9. The device of claim 8 , wherein the thickness of the n-type AlGaN surface layer is between 1 nm and 3 nm.
10. The device of claim 7 , wherein the n-type AlGaN layer is graded with a graded aluminum mole fraction and is graded as a function of thickness.
11. The device of claim 10 , wherein a graded aluminum mole fraction increases as a distance to the Schottky contact decreases.
12. The device of claim 7 , wherein the AlGaN surface layer has a thickness which is less than a critical thickness, wherein the critical thickness is determined based on an aluminum mole fraction of the AlGaN surface layer.