Field reducing structures for nitrogen-polar group III-nitride semiconductor devices
Field reducing structures for transistor devices having Group III-nitride semiconductor structures are provided. In one example, a transistor device includes a nitrogen-polar (N-polar) Group III-nitride semiconductor structure. The transistor device includes a source contact, a drain contact, and a gate contact. The transistor device includes a field reducing structure operable to reduce an electric field in a region in the N-polar Group III-nitride semiconductor structure between the gate contact and the drain contact.
1 . A transistor device, comprising:
a nitrogen-polar (N-polar) Group III-nitride semiconductor structure;
a source contact, a drain contact, and a gate contact; and
a field reducing structure operable to reduce an electric field in a region in the N-polar Group III-nitride semiconductor structure between the gate contact and the drain contact;
wherein the gate contact has a gate length of about 100 nm or greater.
2 . The transistor device of claim 1 , wherein the field reducing structure comprises a field plate overlapping the N-polar Group III-nitride semiconductor structure.
3 . The transistor device of claim 2 , wherein the field plate is electrically coupled to the source contact.
4 . The transistor device of claim 2 , wherein the field plate has a laterally extending portion that overlaps at least a portion of the gate contact.
5 . The transistor device of claim 2 , wherein the field plate does not overlap the gate contact.
6 . The transistor device of claim 2 , further comprising a dielectric layer between the field plate and the N-polar Group III-nitride semiconductor structure.
7 . The transistor device of claim 6 , wherein the field plate is at least partially recessed into the N-polar Group III-nitride semiconductor structure.
8 . The transistor device of claim 2 , wherein the field plate is directly on the N-polar Group III-nitride semiconductor structure to form a Schottky contact with the N-polar Group III-nitride semiconductor structure.
9 . The transistor device of claim 2 , wherein the N-polar Group III-nitride semiconductor structure comprises a barrier layer and a channel layer on the barrier layer, and one or more cap layers, wherein the field plate is at least partially recessed into the one or more cap layers.
10 . The transistor device of claim 1 , wherein the field reducing structure comprises an implanted region in the N-polar Group III-nitride semiconductor structure.
11 . The transistor device of claim 10 , wherein the implanted region is electrically coupled to the source contact.
12 . The transistor device of claim 10 , wherein the implanted region is electrically coupled to the drain contact.
13 . The transistor device of claim 10 , wherein the implanted region comprises a plurality of implanted dopants, the implanted dopants comprising silicon (Si), magnesium (Mg), fluorine (F), iron (Fe), carbon (C), tin (Sn), or oxygen (O).
14 . The transistor device of claim 1 , wherein the transistor device comprises a second field plate overlapping the N-polar Group III-nitride semiconductor structure.
15 . The transistor device of claim 1 , wherein the transistor device is associated with an operating frequency of less than about 40 GHz.
16 . The transistor device of claim 1 , wherein the transistor device further comprises a silicon carbide substrate.
17 . The transistor device of claim 1 , wherein the transistor device is a high electron mobility transistor device.
18 . A transistor device, comprising:
a nitrogen-polar (N-polar) Group III-nitride semiconductor structure;
a field plate overlapping the N-polar Group III-nitride semiconductor structure;
a second field plate overlapping the field plate; and
a third field plate overlapping the second field plate.
19 . A method of forming a transistor device, comprising:
forming a nitrogen-polar (N-polar) Group III-nitride semiconductor structure;
forming a gate contact having a gate length of about 100 nm or greater; and
forming a field plate overlapping at least a portion of the N-polar Group III-nitride semiconductor structure.