Semiconductor heterostructure diodes
Planar Schottky diodes for which the semiconductor material includes a heterojunction which induces a 2DEG in at least one of the semiconductor layers. A metal anode contact is on top of the upper semiconductor layer and forms a Schottky contact with that layer. A metal cathode contact is connected to the 2DEG, forming an ohmic contact with the layer containing the 2DEG.
1. A diode, comprising:
a first III-N material layer;
a second III-N material layer on the first III-N material layer, wherein the second III-N material layer has a thickness and a 2DEG channel is in the first III-N material layer because of a compositional difference between the first III-N material layer and the second III-N material layer;
a first insulator layer on the second III-N material layer so that the second III-N material layer is between the first insulator layer and the first III-N material layer; and
two terminals, wherein a first terminal is an anode that extends through an entirety of the thickness of the second III-N material layer to contact the first III-N material layer and form a Schottky contact with the first III-N material layer and has an extending portion that extends over the first insulator layer, and a second terminal is a single cathode in ohmic contact with the 2DEG channel.
2. The diode of claim 1 , wherein the first insulator layer is less than 7 nm thick.
3. The diode of claim 2 , further comprising:
a second insulator layer on the first insulator layer; and
a field plate, wherein the field plate extends from the extending portion of the anode and the second insulator layer is between the field plate and the first insulator layer.
4. The diode of claim 3 , wherein the second insulator layer comprises SiN.
5. The diode of claim 1 , further comprising sidewall insulating material surrounding a lateral sidewall of the anode, wherein a horizontal portion of the anode contacts the first III-N material layer.
6. The diode of claim 1 , further comprising a third III-N material layer between the first III-N material layer and the second III-N material layer.
7. The diode of claim 6 , wherein the third III-N material layer is AlN.
8. The diode of claim 1 , further comprising a third III-N material layer contacting the first III-N material layer on a side opposite the second III-N material layer, wherein the first, second, and third III-N material layers are N-polar or nitrogen-terminated semi-polar material and the first insulator is on an N-polar or nitrogen-terminated semi-polar face of the second III-N material layer.
9. The diode of claim 8 , wherein the first III-N material layer has a first thickness, the thickness of the second III-N material layer is a second thickness, and the anode further extends through an entirety of the first thickness of the first III-N material layer to contact the third III-N material layer.
10. The diode of claim 1 , wherein the first insulator layer comprises SiN.
11. The diode of claim 1 , wherein the first insulator layer functions as a surface passivation layer.
12. The diode of claim 1 , wherein the first insulator layer includes a first aperture with at least two sidewalls, and the diode further comprises a second insulator layer including a second aperture with at least two sidewalls, the second insulator layer disposed on the first insulator layer so that the first insulator layer is between the second insulator layer and the second III-N material layer, wherein the anode is at least partially between the at least two sidewalls of the first aperture, and the extending portion of the anode further extends over the second insulator layer.
13. The diode of claim 12 , wherein the first aperture has a first width and the second aperture has a second width, the second width being larger than the first width.
14. The diode of claim 12 , wherein the extending portion of the anode functions as a field plate.
15. The diode of claim 12 , wherein the extending portion of the anode contacts at least one of the at least two sidewalls of the second insulator layer.