US20030157776A1
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Methods of fabricating aluminum gallium nitride/gallium nitride high electron mobility transistors having a gate contact on a gallium nitride based cap segment
Assignee: Individual
•
Filing: 2003-02-25
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Granted: —
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Expires: 2023-02-25
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 Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:40
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: 47
Claim 1
Independent Claim
160 words
1 . 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
160 words
1 . 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
27 words
2 . 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
20 words
3 . A HEMT according to claim 1 , wherein the GaN based cap segment comprises a GaN cap segment.
Claim 5
Dependent Claim
26 words
4 . 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
25 words
5 . 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
16 words
6 . HEMT according to claim 5 , wherein the GaN cap segment comprises undoped GaN.
Claim 8
Dependent Claim
28 words
7 . 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
27 words
8 . 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
29 words
9 . 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
30 words
10 . 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
22 words
11 . A HEMT according to claim 3 , wherein the AlGaN barrier layer comprises between about 15% and about 60% aluminum.
Claim 13
Dependent Claim
33 words
12 . 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
25 words
13 . 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
20 words
14 . A HEMT according to claim 13 wherein the AlGaN barrier layer has a thickness of about 25 nm.
Claim 16
Dependent Claim
23 words
15 . A HEMT according to claim 3 , further comprising a substrate, and wherein the GaN channel layer is on the substrate.
Claim 17
Dependent Claim
15 words
16 . A HEMT according to claim 15 , wherein the substrate comprises silicon carbide.
Claim 18
Dependent Claim
14 words
17 . A HEMT according to claim 15 , wherein the substrate comprises sapphire.
Claim 19
Dependent Claim
24 words
18 . 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
24 words
19 . 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
18 words
20 . A HEMT according to claim 1 , wherein the gate electrode comprises a T-shaped gate electrode.
Claim 22
Dependent Claim
179 words
21 . A method of fabricating a high electron mobility transistor (HEMT), comprising: forming a first gallium nitride (GaN) layer on a substrate; forming an aluminum gallium nitride (AlGaN) layer on the first GaN layer; forming a GaN-based segment on the AlGaN layer, the GaN-based segment having an aluminum concentration of less than the AlGaN layer; forming a first ohmic contact to the AlGaN layer adjacent and spaced apart from the GaN segment to provide a source electrode; forming a second ohmic contact to the AlGaN layer adjacent and spaced apart from the GaN segment and opposite first ohmic contact such that the GaN segment is disposed between the first ohmic contact and the second ohmic contact to provide a drain electrode; and forming a non-ohmic contact on the GaN segment to provide a gate contact, the gate contact having a first sidewall which is substantially aligned with the a first sidewall of the GaN segment adjacent the source contact and the gate contact extending only a portion of a distance between the first sidewall the second ohmic contact.
Claim 23
Dependent Claim
179 words
21 . A method of fabricating a high electron mobility transistor (HEMT), comprising: forming a first gallium nitride (GaN) layer on a substrate; forming an aluminum gallium nitride (AlGaN) layer on the first GaN layer; forming a GaN-based segment on the AlGaN layer, the GaN-based segment having an aluminum concentration of less than the AlGaN layer; forming a first ohmic contact to the AlGaN layer adjacent and spaced apart from the GaN segment to provide a source electrode; forming a second ohmic contact to the AlGaN layer adjacent and spaced apart from the GaN segment and opposite first ohmic contact such that the GaN segment is disposed between the first ohmic contact and the second ohmic contact to provide a drain electrode; and forming a non-ohmic contact on the GaN segment to provide a gate contact, the gate contact having a first sidewall which is substantially aligned with the a first sidewall of the GaN segment adjacent the source contact and the gate contact extending only a portion of a distance between the first sidewall the second ohmic contact.
Claim 24
Dependent Claim
36 words
22 . A method according to claim 21 , wherein the non-ohmic contact extends only a portion of a distance between the first sidewall and a second sidewall of the GaN segment adjacent the drain contact.
Claim 25
Dependent Claim
23 words
23 . A method according to claim 22 , wherein forming a GaN-based segment comprises forming a GaN segment on the AlGaN layer.
Claim 26
Dependent Claim
57 words
24 . A method according to claim 23 , wherein the forming a GaN segment and forming a non-ohmic contact comprises: forming a second GaN layer on the AlGaN layer; forming a non-ohmic contact on the second GaN layer; patterning the non-ohmic contact and the second GaN layer to provide the GaN segment and the gate contact.
Claim 27
Dependent Claim
93 words
25 . A method according to claim 24 , wherein patterning the non-ohmic contact and the second GaN layer comprises: forming a mask layer on the non-ohmic contact and the second GaN layer so that the mask covers portions of the non-ohmic contact and the second GaN layer so as to define a sidewall of the non-ohmic contact and the GaN segment adjacent the source contact and a sidewall of the GaN segment adjacent the drain contact; etching the non-ohmic contact and the second GaN layer to expose portions of the AlGaN layer.
Claim 28
Dependent Claim
26 words
26 . A method according to claim 23 , wherein the GaN segment is formed to a thickness of from about 10 to about 60 Å.
Claim 29
Dependent Claim
16 words
27 . A method according to claim 26 , wherein the GaN segment comprises undoped GaN.
Claim 30
Dependent Claim
46 words
28 . A method according to claim 23 , wherein forming a first ohmic contact and forming a second ohmic contact comprises forming a first ohmic contact and a second ohmic contact which are spaced apart a distance of from about 2 to about 4 μm.
Claim 31
Dependent Claim
28 words
29 . A method according to claim 23 , wherein the first ohmic contact is formed a distance of less than about 2 μm from the GaN segment.
Claim 32
Dependent Claim
30 words
30 . A method according to claim 29 , wherein the first ohmic contact is formed a distance of from about 0.3 to about 1.5 μm from the GaN segment.
Claim 33
Dependent Claim
39 words
31 . A method according to claim 23 , wherein the non-ohmic contact is patterned so that a sidewall of the non-ohmic contact is from about 0.5 to about 1 μm from the second sidewall of the GaN segment.
Claim 34
Dependent Claim
27 words
32 . A method according to claim 23 , wherein forming an AlGaN layer comprises forming an AlGaN layer having between about 15% and about 60% aluminum.
Claim 35
Dependent Claim
37 words
33 . A method according to claim 32 , wherein forming an AlGaN layer comprises forming an AlGaN layer doped with silicon to provide a total sheet concentration of up to about 5×10 12 cm −2 .
Claim 36
Dependent Claim
31 words
34 . A method according to claim 32 , wherein forming an AlGaN layer further comprises forming an AlGaN layer to a thickness of from about 15 to about 40 nm.
Claim 37
Dependent Claim
26 words
35 . A method according to claim 34 , wherein forming an AlGaN layer comprises forming an AlGaN layer to a thickness of about 25 nm.
Claim 38
Dependent Claim
15 words
36 . A method according to claim 23 , wherein the substrate comprises silicon carbide.
Claim 39
Dependent Claim
14 words
37 . A method according to claim 23 , wherein the substrate comprises sapphire.
Claim 40
Dependent Claim
25 words
38 . A method according to claim 23 , wherein the substrate comprises at least one of 4H silicon carbide and 6 H silicon carbide.
Claim 41
Dependent Claim
25 words
39 . A method according to claim 23 , further comprising forming a third GaN layer disposed between the first GaN layer and the substrate.
Claim 42
Dependent Claim
24 words
40 . A method according to claim 23 , further comprising forming a metallization layer on the non-ohmic contact to provide a T-shaped gate.
Claim 43
Dependent Claim
102 words
41 . A high electron mobility transistor (HEMT), comprising: a gallium nitride (GaN) channel layer; an aluminum gallium nitride (AlGaN) barrier layer; ohmic contacts on the AIGaN 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 44
Dependent Claim
102 words
41 . A high electron mobility transistor (HEMT), comprising: a gallium nitride (GaN) channel layer; an aluminum gallium nitride (AlGaN) barrier layer; ohmic contacts on the AIGaN 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 45
Dependent Claim
77 words
42 . A HEMT according to claim 41 , 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 AIGaN 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 46
Dependent Claim
33 words
43 . A HEMT according to claim 42 , 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 47
Dependent Claim
25 words
44 . A HEMT according to claim 42 , wherein the segment of GaN extends a distance of from about 0.5 to about 1 μm.
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