Enhancement mode III-nitride FET
View Patent ↗A III-nitride switch includes a recessed gate contact to produce a nominally off, or an enhancement mode, device. By providing a recessed gate contact, a conduction channel formed at the interface of two III-nitride materials is interrupted when the gate electrode is inactive to prevent current flow in the device. The gate electrode can be a schottky contact or an insulated metal contact. Two gate electrodes can be provided to form a bi-directional switch with nominally off characteristics. The recesses formed with the gate electrode can have sloped sides. The gate electrodes can be formed in a number of geometries in conjunction with current carrying electrodes of the device.
1. A method of fabricating an enhancement mode III-nitride device, comprising:
forming a conduction channel at a III-nitride heterojunction between first and second III-nitride bodies, said conduction channel including a two-dimensional electron gas;
forming a modified region in said first III-nitride body, said modified region causing an interrupted region in said conduction channel, said modified region comprising an oxidized region;
disposing a gate electrode over said interrupted region, said gate electrode operable to restore said interrupted region of said conduction channel thereby permitting current conduction in said conduction channel.
2. The method of claim 1 , wherein said forming said modified region comprises oxidizing said first III-nitride body.
3. The method of claim 1 , wherein said gate electrode is Schottky coupled to said second III-nitride body.
4. The method of claim 1 , wherein said first III-nitride body is comprised of AlGaN and said second III-nitride body is comprised of GaN.
5. The method of claim 1 , wherein forming said conduction channel at said III-nitride heterojunction comprises forming said first III-nitride body on said second III-nitride body, wherein said first and second III-nitride bodies comprise undoped III-nitride bodies.
6. The method of claim 1 , wherein said oxidized region is in a top surface of said first III-nitride body.
7. The method of claim 1 , wherein said first III-nitride body is an AlGaN layer and said oxidized region is of said AlGaN layer.
8. The method of claim 1 , wherein said forming said modified region comprises oxidizing AlGaN.
9. The method of claim 1 , wherein said oxidized region is disposed below said gate electrode.
10. The method of claim 1 , wherein said gate electrode is directly on said oxidized region.
11. The method of claim 1 , wherein said oxidized region is recessed below a top surface of said first III-nitride body.
12. The method of claim 1 , wherein said oxidized region is on sidewalls of a recess in said first III-nitride body.
13. The method of claim 1 , wherein a portion of said oxidized region tapers into said first III-nitride body.