III-nitride semiconductor device with reduced electric field between gate and drain and process for its manufacture
A conductive field plate is formed between the drain electrode and gate of each cell of a III-Nitride semiconductor and is connected to the source electrode to reduce the electric field between the gate and the drain. The electrodes may be supported on N + III-Nitride pad layers and the gate may be a Schottky gate or an insulated gate.
1. A III-Nitride semiconductor device comprising:
a first III-Nitride layer of a first composition,
a second III-Nitride layer of a second composition different from the said first composition atop said first III-Nitride layer,
a 2DEG layer formed by the interface between said first and second III-Nitride layers,
a source contact connected to the free surface of said first III-Nitride layer,
a drain contact laterally spaced from said source contact and connected to said free surface of said first III-Nitride layer,
a gate contact coupled to said free surface of said first III-Nitride layer and disposed laterally between said source and drain contacts, and
a conductive field plate disposed between said gate and drain contacts and connected to said source contact to reduce the electric field between said gate and drain contacts when said 2DEG layer is non-conductive, said conductive field plate substantially coplanar with said gate contact, wherein said conductive field plate is formed from a first portion of a wide gate electrode, and wherein said gate contact is formed from a second portion of said wide gate electrode, said second portion being physically separated and laterally spaced from said first portion;
wherein said first layer is GaN and said second layer is AlGaN; and
wherein said field plate is a layer of N type III-Nitride material.
2. The device of claim 1 , wherein said second layer is supported on a substrate.
3. The device of claim 2 , wherein said substrate is silicon and includes a transition layer connected to said second layer.
4. The device of claim 2 , which further includes a highly conductive III-Nitride pad disposed between said source and drain contacts and said free surface of said first III-Nitride layer.
5. The device of claim 2 , wherein said field plate is a layer of highly conductive N+ III-Nitride material.
6. The device of claim 1 , wherein said gate contact is a Schottky contact.
7. The device of claim 6 , which further includes a highly conductive III-Nitride pad disposed between said source and drain contacts and said free surface of said first III-Nitride layer.
8. The device of claim 6 , wherein said field plate is a layer of highly conductive N+ III-Nitride material.
9. The device of claim 1 , wherein said gate contact is dielectrically insulated from said surface of said first III-Nitride layer.
10. The device of claim 9 , which further includes a highly conductive III-Nitride pad disposed between said source and drain contacts and said free surface of said first III-Nitride layer.
11. The device of claim 9 , wherein said field plate is a layer of highly conductive N+ III-Nitride material.
12. The device of claim 1 , which further includes a highly conductive III-Nitride pad disposed between said source and drain contacts and said free surface of said first III-Nitride layer.
13. The device of claim 12 , wherein said field plate is a layer of highly conductive N+ III-Nitride material.
14. The device of claim 1 , which further includes a highly conductive III-Nitride pad disposed between said source and drain contacts and said free surface of said first III-Nitride layer.
15. The device of claim 1 , wherein said field plate is a layer of highly conductive N+ III-Nitride material.