High voltage switching devices and process for forming same
View Patent ↗The present invention relates to various switching device structures including Schottky diode, P-N diode, and P-I-N diode, which are characterized by low defect density, low crack density, low pit density and sufficient thickness (>2.5 um) GaN layers of low dopant concentration (<1E16 cm −3 ) grown on a conductive GaN layer. The devices enable substantially higher breakdown voltage on hetero-epitaxial substrates (<2 KV) and extremely high breakdown voltage on homo-epitaxial substrates (>2 KV).
1. A microelectronic device structure adapted for high voltage operation, said microelectronic device structure comprising:
(a) a first conductive GaN base layer comprising a GaN structure having a thickness of greater than about 50 μm and having a top surface characterized by a dislocation defect density of not more than about 5×10 6 /cm 2 ;
(b) a second GaN layer having a dopant concentration of not more than about 1×10 16 /cm 3 , disposed adjacent to the top surface of said first conductive GaN base layer; and
(c) at least one metal contact adjacent to at least one of (i) the top surface of said first conductive GaN base layer and (ii) said second GaN layer, forming a metal-to-semiconductor junction with at least one of said first conductive GaN base layer and said second GaN layer;
wherein said microelectronic device structure has a breakdown voltage of at least about 450V.
2. The microelectronic device structure of claim 1 , having a breakdown voltage of at least 1000V.
3. The microelectronic device structure of claim 1 , having a breakdown voltage of at least 2000V.
4. A microelectronic device structure adapted for high voltage operation, said microelectronic device structure comprising:
(a) a first GaN layer of n-type conductivity and comprising a GaN structure having a thickness of greater than about 50 μm and having a top surface characterized by a dislocation defect density of not more than about 5×10 6 /cm 2 ;
(b) a second GaN layer having a dopant concentration of not more than about 1×10 15 /cm 3 , disposed adjacent to said first GaN layer;
(c) a third GaN layer of p-type conductivity, disposed adjacent to said second GaN layer; and
(d) at least one metal contact disposed adjacent to said third GaN layer;
wherein the microelectronic device structure has a breakdown voltage of at least about 450V.
5. The microelectronic device structure of claim 4 , having a breakdown voltage of at least 1000V.
6. The microelectronic device structure of claim 4 , having a breakdown voltage of at least 2000V.
7. The microelectronic device structure of claim 1 , wherein a first metal contact of said at least one metal contact forms a Schottky contact with said second GaN layer, and wherein a second metal contact of said at least one metal contact forms an ohmic contact with said first conductive GaN base layer.
8. The microelectronic device structure of claim 1 , wherein the top surface of said first conductive GaN base layer is undoped, and wherein the second GaN layer is subsequently grown uniformly adjacent to the first conductive GaN base layer.
9. The microelectronic device structure of claim 1 , comprising a Schottky diode selected from the group consisting of mesa-type Schottky diodes and planar-type Schottky diodes.
10. The microelectronic device structure of claim 1 , further comprising at least one electrically conductive underside contact adjacent to the first conductive GaN base layer.
11. The microelectronic device structure of claim 1 , wherein the at least one metal contact forms a metal-to-semiconductor junction with the second GaN layer.
12. The microelectronic device structure of claim 1 , wherein the first conductive GaN base layer is of n-type conductivity.
13. The microelectronic device structure of claim 4 , wherein said second GaN layer is more than about 10 μm in thickness, and wherein said third GaN layer of p-type conductivity is more than about 0.25 μm in thickness.
14. The microelectronic device structure of claim 4 , wherein a first metal contact of said at least one metal contact forms a first ohmic contact with said first GaN layer of n-type conductivity, and wherein a second metal contact of said at least one metal contact forms a second ohmic contact with said third GaN layer of p-type conductivity.
15. The microelectronic device structure of claim 4 , wherein the second GaN layer is doped with germanium.
16. The microelectronic device structure of claim 4 , wherein the top surface of said first GaN layer of n-type conductivity is undoped, and wherein the second GaN layer is subsequently grown uniformly adjacent to the first GaN layer.
17. The microelectronic device structure of claim 4 , wherein the third GaN layer is less than 50 mm in thickness.
18. The microelectronic device structure of claim 4 , comprising a Schottky diode selected from the group consisting of mesa-type Schottky diodes and planar-type Schottky diodes.
19. The microelectronic device structure of claim 4 , further comprising at least one electrically conductive underside contact adjacent to the first GaN layer.
20. The microelectronic device structure of claim 4 , wherein the at least one metal contact is disposed in direct contact with the third GaN layer.