Patent US6548333B2 successfully refreshed from Google Patents.
US6548333B2
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Aluminum gallium nitride/gallium nitride high electron mobility transistors having a gate contact on a gallium nitride based cap segment
Assignee: Wolfspeed Inc
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Filing: 2001-07-12
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Granted: 2003-04-15
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Expires: 2021-07-12
Abstract
Abstract High electron mobility transistors (HEMTs) and methods of fabricating HEMTs are provided Devices according to embodiments of the present invention include a gallium nitride (GaN) channel layer and an aluminum gallium nitride (AlGaN) barrier layer on the channel layer. A first ohmic contact is provided on the barrier layer to provide a source electrode and a second ohmic contact is also provided on the barrier layer and is spaced apart from the source electrode to provide a drain electrode. A GaN-based cap segment is provided on the barrier layer between the source electrode and the drain electrode. The GaN-based cap segment has a first sidewall adjacent and spaced apart from the source electrode and may have a second sidewall adjacent and spaced apart from the drain electrode. A non-ohmic contact is provided on the GaN-based cap segment to provide a gate contact. The gate contact has a first sidewall which is substantially aligned with the first sidewall of the GaN-based cap segment. The gate contact extends only a portion of a distance between the first sidewall and the second sidewall of the GaN-based cap segment.
Inventors
- 👤 Richard Peter Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:41
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/20; H10D64/27; H10D64/311; H10D64/411; H10D30/00; H10D30/40; H10D30/47; H10D30/471; H10D30/473; H10D30/4732; H10D62/00; H10D62/80; H10D62/85; H10D62/8503
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
158 words
A high electron mobility transistor (HEMT) comprising: a gallium nitride (GaN) channel layer; an aluminum gallium nitride (AlGaN) barrier layer on the channel layer; a first ohmic contact on the barrier layer to provide a source electrode; a second ohmic contact on the barrier layer and spaced apart from the source electrode to provide a drain electrode; a GaN-based cap segment on the barrier layer between the source electrode and the drain electrode, the GaN-based cap segment having a lower concentration of aluminum than the barrier layer and having a first sidewall adjacent and spaced apart from the source electrode; and a non-ohmic contact on the GaN cap segment to provide a gate contact, the gate contact having a first sidewall which is substantially aligned with the first sidewall of the GaN cap segment and the gate contact extending only a portion of a distance between the first sidewall and the second sidewall of the GaN cap segment.
Claim 2
Dependent Claim
158 words
A high electron mobility transistor (HEMT) comprising: a gallium nitride (GaN) channel layer; an aluminum gallium nitride (AlGaN) barrier layer on the channel layer; a first ohmic contact on the barrier layer to provide a source electrode; a second ohmic contact on the barrier layer and spaced apart from the source electrode to provide a drain electrode; a GaN-based cap segment on the barrier layer between the source electrode and the drain electrode, the GaN-based cap segment having a lower concentration of aluminum than the barrier layer and having a first sidewall adjacent and spaced apart from the source electrode; and a non-ohmic contact on the GaN cap segment to provide a gate contact, the gate contact having a first sidewall which is substantially aligned with the first sidewall of the GaN cap segment and the gate contact extending only a portion of a distance between the first sidewall and the second sidewall of the GaN cap segment.
Claim 3
Dependent Claim
25 words
A HEMT according to claim 1 , wherein the GaN based cap segment has a second sidewall adjacent and spaced apart from the drain electrode.
Claim 4
Dependent Claim
18 words
A HEMT according to claim 1 , wherein the GaN based cap segment comprises a GaN cap segment.
Claim 5
Dependent Claim
24 words
A HEMT according to claim 3 , wherein the non-ohmic contact extends to, but not past, the first sidewall of the GaN cap segment.
Claim 6
Dependent Claim
23 words
A HEMT according to claim 3 , wherein the GaN cap segment has a thickness of from about 10 to about 60 Å.
Claim 7
Dependent Claim
14 words
HEMT according to claim 5 , wherein the GaN cap segment comprises undoped GaN.
Claim 8
Dependent Claim
26 words
HEMT according to claim 2 wherein the source electrode and the drain electrode are spaced apart a distance of from about 2 to about 4 μm.
Claim 9
Dependent Claim
25 words
A HEMT according to claim 3 wherein the first sidewall of the GaN cap segment is less than about 2 μm from the source electrode.
Claim 10
Dependent Claim
27 words
HEMT according to claim 8 , wherein the first sidewall of the GaN cap segment is from about 0.3 to about 1.5 μm from the source electrode.
Claim 11
Dependent Claim
28 words
A HEMT according to claim 2 , wherein the second sidewall of the GaN cap segment is from about 0.5 to about 1 μm from the gate electrode.
Claim 12
Dependent Claim
20 words
A HEMT according to claim 3 , wherein the AlGaN barrier layer comprises between about 15% and about 60% aluminum.
Claim 13
Dependent Claim
31 words
A HEMT according to claim 11 , wherein the AlGaN barrier layer is doped with silicon to provide a total sheet concentration of up to about 5×10 12 cm −2 .
Claim 14
Dependent Claim
23 words
A HEMT according to claim 11 , wherein the AlGaN barrier layer has a thickness of from about 15 to about 40 nm.
Claim 15
Dependent Claim
18 words
A HEMT according to claim 13 wherein the AlGaN barrier layer has a thickness of about 25 nm.
Claim 16
Dependent Claim
21 words
A HEMT according to claim 3 , further comprising a substrate, and wherein the GaN channel layer is on the substrate.
Claim 17
Dependent Claim
13 words
A HEMT according to claim 15 , wherein the substrate comprises silicon carbide.
Claim 18
Dependent Claim
12 words
A HEMT according to claim 15 , wherein the substrate comprises sapphire.
Claim 19
Dependent Claim
22 words
A HEMT according to claim 15 , wherein the substrate comprises at least one of 4H silicon carbide and 6H silicon carbide.
Claim 20
Dependent Claim
22 words
A HEMT according to claim 15 , further comprising a GaN buffer layer disposed between the GaN channel layer and the substrate.
Claim 21
Dependent Claim
16 words
A HEMT according to claim 1 , wherein the gate electrode comprises a T-shaped gate electrode.
Claim 22
Dependent Claim
100 words
A high electron mobility transistor (HEMT), comprising: a gallium nitride (GaN) channel layer; an aluminum gallium nitride (AlGaN) barrier layer; ohmic contacts on the AlGaN barrier layer to provide source and drain contacts; a non-ohmic gate contact disposed between the source and drain contacts; and means, operably associated with the non-ohmic gate contact and the AlGaN barrier layer, for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact as compared to a device without the means for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact.
Claim 23
Dependent Claim
100 words
A high electron mobility transistor (HEMT), comprising: a gallium nitride (GaN) channel layer; an aluminum gallium nitride (AlGaN) barrier layer; ohmic contacts on the AlGaN barrier layer to provide source and drain contacts; a non-ohmic gate contact disposed between the source and drain contacts; and means, operably associated with the non-ohmic gate contact and the AlGaN barrier layer, for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact as compared to a device without the means for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact.
Claim 24
Dependent Claim
75 words
A HEMT according to claim 21 , wherein the means for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact comprises a segment of GaN between the gate contact and the AlGaN barrier layer, the segment of GaN having the gate contact on a portion of the segment of GaN adjacent the source contact and the segment of GaN extending past the gate contact toward the drain contact.
Claim 25
Dependent Claim
31 words
A HEMT according to claim 22 , wherein the gate contact extends to but not past a sidewall of the segment of GaN adjacent but spaced apart from the source electrode.
Claim 26
Dependent Claim
23 words
A HEMT according to claim 22 , wherein the segment of GaN extends a distance of from about 0.5 to about 1 μm.
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