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US 8,044,432 B2Granted
Low density drain HEMTs
AssigneeThe Hong Kong University of Science and Technology
InventorsJing Chen, Kei May Lau
Life of this patent
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Abstract
Methods and devices for fabricating AlGaN/GaN normally-off high electron mobility transistors (HEMTs). A fluorine-based (electronegative ions-based) plasma treatment or low-energy ion implantation is used to modify the drain-side surface field distribution without the use of a field plate electrode. The off-state breakdown voltage can be improved and current collapse can be completely suppressed in LDD-HEMTs with no significant degradation in gains and cutoff frequencies.
Claims14
A field-effect transistor, comprising:
- a source contact and a drain contact;
- a channel, in a vertically inhomogeneous semiconductor material having at least two layers, a top layer of the at least two layers overlain by a gate, wherein the gate is disposed between the source contact and the drain contact;
- the top layer of said vertically inhomogeneous semiconductor material having a higher aluminum fraction than an other layer of the at least two layers and a wider bandgap than the other layer;
- and
- a first fixed negative ion region and a second permanently fixed negative ion region within the top layer of the at least two layers of said vertically inhomogeneous semiconductor material, said first fixed negative ion region being under the gate, and said second permanently fixed negative ion region being between the gate and the drain contact, wherein a non-zero density of negative ions is lower in said second permanently fixed negative ion region than a density of negative ions in said first fixed negative ion region.
2 more elements
A field-effect transistor, comprising:
- a source contact and a drain contact;
- a channel, in a vertically inhomogeneous semiconductor material having at least two layers, a top layer of the at least two layers overlain by a gate, wherein the gate is disposed between the source contact and the drain contact;
- the top layer of said vertically inhomogeneous semiconductor material having a higher aluminum fraction than an other layer of the at least two layers and a wider bandgap than the other layer;
- and
- a first fixed negatively charged fluorine ion region and a second fixed negatively charged fluorine ion region within the top layer of the at least two layers of said vertically inhomogeneous semiconductor material, said first fixed negatively charged fluorine ion region being under the gate, said second fixed negatively charged fluorine ion region being between the gate and the drain contact, wherein said first fixed negatively charged fluorine ion region and said second fixed negatively charged fluorine ion region are physically adjacent to each other, and a non-zero density of negatively charged fluorine ion in said second fixed negatively charged fluorine ion region is lower than a density of negatively charged fluorine ion in said first fixed negatively charged fluorine ion region.
2 more elements
A field-effect transistor, comprising:
- a source contact and a drain contact;
- a channel, in a vertically inhomogeneous semiconductor material having at least two layers, a top layer of the at least two layers overlain by a gate, wherein the gate is disposed between the source contact and the drain contact;
- the top layer of said vertically inhomogeneous semiconductor material having a higher aluminum fraction than an other layer of the at least two layers and a wider bandgap than the other layer;
- and
- a region of trapped fluorine ions, within the top layer of said vertically inhomogeneous semiconductor material, which lies between said gate and said channel, and which also extends laterally toward said drain contact.
2 more elements
A field-effect transistor, comprising:
- a source contact and a drain contact;
- a top layer directly on an other layer, wherein the top layer is overlain by a gate, wherein the gate is provided between the source contact and the drain contact, and wherein the top layer has a higher aluminum fraction and a wider bandgap than the other layer;
- and
- a first fixed negative ion region and a second permanently fixed negative ion region within the top layer, wherein the first fixed negative ion region is under the gate, and the second permanently fixed negative ion region is between the gate and the drain contact, wherein a non-zero density of negative ions is lower in the second permanently fixed negative ion region than a density of negative ions in the first fixed negative ion region.
1 more element
Dependencies are inferred from the claim text.