US4939557A
Expired / Lapsed
US
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(110) GaAs microwave FET
Assignee: Varian Medical Systems Inc
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Filing: 1989-02-15
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Granted: 1990-07-03
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Expires: 2009-02-15
Abstract
Abstract A field effect transistor (FET) structure suitable for use at microwave frequencies is fabricated on a planar surface of a semi-insulating single crystal GaAs substrate which has been cut and polished to present the (110) surface. This orientation is selected because of its non-polar and other unique surface and interface properties. The (110) crystal axis is tilted from the normal of the planar surface in the direction to expose more of the (111) Ga face about 5° to facilitate molecular beam epitaxial (MBE) growth of smooth, defect-free thin films. An elongate gate electrode is formed along the bottom of an anisotropically etched trench having a pair of longitudinal sidewalls, one vertical and the other tilted outwardly. The trench is selectively oriented on the substrate to facilitate such anisotropic etching. Source and drain electrodes are respectively formed proximate the outwardly tilted and vertical trench sidewalls thereby forming a FET with a higher drain-to-gate breakdown voltage combined with lower parasitic resistance between the source and gate electrode. The invention has demonstrated potential for high speed digital circuits as well a microwave power FET applications.
Inventors
- 👤 Yi-Ching Pao
- 👤 James S. Harris
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:36
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/80; H10D30/87; H10D30/877; H10D62/00; H10D62/40; H10D62/405; H10D64/00; H10D64/20; H10D64/27; H10D64/311; H10D64/411
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
198 words
A FET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face in a range from 2° to 8°; a first layer of N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs material epitaxially grown on said first layer; an elongate gate electrode disposed along the bottom of an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 2
Dependent Claim
198 words
A FET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face in a range from 2° to 8°; a first layer of N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs material epitaxially grown on said first layer; an elongate gate electrode disposed along the bottom of an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 3
Dependent Claim
207 words
A FET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face in a range from 2° to 8°; a first layer of N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs material epitaxially grown on said first layer; an elongate Schottky barrier gate electrode formed in selected portions of said first layer along the bottom of an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 4
Dependent Claim
207 words
A FET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face in a range from 2° to 8°; a first layer of N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs material epitaxially grown on said first layer; an elongate Schottky barrier gate electrode formed in selected portions of said first layer along the bottom of an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 5
Dependent Claim
20 words
A FET as in claim 2 wherein said first layer of N type semiconductor material comprises GaAs doped with Si.
Claim 6
Dependent Claim
21 words
The FET of claim 3 wherein said second layer of GaAs is doped with Si to form N+ type semiconductor material.
Claim 7
Dependent Claim
31 words
The FET of claim 4 wherein said (110) axis is tilted from the normal of said planar surface in the direction to expose more of the (111) Ga face about 5°.
Claim 8
Dependent Claim
16 words
The FET of claim 5 wherein said Schottky barrier gate electrode comprises Ti, Pt, and Au.
Claim 9
Dependent Claim
19 words
The FET of claim 2 wherein said first layer of N type semiconductor material comprises AlGaAs doped with Si.
Claim 10
Dependent Claim
21 words
The FET of claim 7 wherein said second layer of GaAs is doped with Si to form N+ type semiconductor material.
Claim 11
Dependent Claim
31 words
The FET of claim 8 wherein said (110) axis is tilted from the normal of said planar surface in the direction to expose more of the (111) Ga face about 5°.
Claim 12
Dependent Claim
16 words
The FET of claim 9 wherein said Schottky barrier gate electrode comprises Ti, Pt, and Au.
Claim 13
Dependent Claim
19 words
The FET of claim 2 wherein said first layer of N type semiconductor material comprises GaAs doped with Te.
Claim 14
Dependent Claim
19 words
The FET of claim 2 wherein said first layer of N type semiconductor material comprises AlGaAs doped with Te.
Claim 15
Dependent Claim
221 words
A MESFET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face about 5°; a first layer of GaAs doped with Si to form N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs doped with Si to form N+ type semiconductor material epitaxially grown on said first layer; an elongate Schottky barrier gate electrode formed with Ti, Pt and Au in selected portions of said first layer along the bottom of an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 16
Dependent Claim
221 words
A MESFET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face about 5°; a first layer of GaAs doped with Si to form N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs doped with Si to form N+ type semiconductor material epitaxially grown on said first layer; an elongate Schottky barrier gate electrode formed with Ti, Pt and Au in selected portions of said first layer along the bottom of an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 17
Dependent Claim
235 words
A FET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face in a range from 2° to 8°; a first layer of N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs material epitaxially grown on said first layer; an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a third layer of electrically insulating material formed on selected exposed portions of said first layer of material along the bottom of said anisotropically etched trench; an elongate gate electrode formed on selected portions of said third layer along the bottom of said anisotropically etched trench; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 18
Dependent Claim
235 words
A FET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face in a range from 2° to 8°; a first layer of N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs material epitaxially grown on said first layer; an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a third layer of electrically insulating material formed on selected exposed portions of said first layer of material along the bottom of said anisotropically etched trench; an elongate gate electrode formed on selected portions of said third layer along the bottom of said anisotropically etched trench; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 19
Dependent Claim
20 words
A FET as in claim 14 wherein said first layer of N type semiconductor material comprises GaAs doped with Si.
Claim 20
Dependent Claim
21 words
The FET of claim 15 wherein said second layer of GaAs is doped with Si to form N+ type semiconductor material.
Claim 21
Dependent Claim
31 words
The FET of claim 16 wherein said (110) axis is tilted from the normal of said planar surface in the direction to expose more of the (111) Ga face about 5°.
Claim 22
Dependent Claim
17 words
The FET of claim 16 wherein said third layer of electrically insulating material comprises SiO 2 .
Claim 23
Dependent Claim
19 words
The FET of claim 16 wherein said third layer of electrically insulating material comprises Si 3 N 4 .
Claim 24
Dependent Claim
15 words
The FET of claim 19 wherein said elongate gate electrode comprises highly doped polycrystalline Si.
Claim 25
Dependent Claim
13 words
The FET of claim 19 wherein said elongate gate electrode comprises a metal.
Claim 26
Dependent Claim
19 words
The FET of claim 14 wherein said first layer of N type semiconductor material comprises AlGaAs doped with Si.
Claim 27
Dependent Claim
21 words
The FET of claim 22 wherein said second layer of GaAs is doped with Si to form N+ type semiconductor material.
Claim 28
Dependent Claim
31 words
The FET of claim 23 wherein said (110) axis is tilted from the normal of said planar surface in the direction to expose more of the (111) Ga face about 5°.
Claim 29
Dependent Claim
17 words
The FET of claim 23 wherein said third layer of electrically insulating material comprises SiO 2 .
Claim 30
Dependent Claim
19 words
The FET of claim 23 wherein said third layer of electrically insulating material comprises Si 3 N 4 .
Claim 31
Dependent Claim
15 words
The FET of claim 26 wherein said elongate gate electrode comprises highly doped polycrystalline Si.
Claim 32
Dependent Claim
13 words
The FET of claim 26 wherein said elongate gate electrode comprises a metal.
Claim 33
Dependent Claim
19 words
The FET of claim 14 wherein said first layer of N type semiconductor material comprises GaAs doped with Te.
Claim 34
Dependent Claim
19 words
The FET of claim 14 wherein said first layer of N type semiconductor material comprises AlGaAs dopes with Te.
Claim 35
Dependent Claim
244 words
A MISFET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face about 5°; a first layer of GaAs doped with Si to form N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs doped with Si to form N+ type semiconductor material epitaxially grown on said first layer; an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a third layer of electrically insulating material formed on selected exposed portions of said first layer of material along the bottom of said anisotropically etched trench; an elongate gate electrode formed on selected portions of said third layer along the bottom of said anisotropically etched trench; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
Claim 36
Dependent Claim
244 words
A MISFET suitable for use at microwave frequencies comprising: a body of semi-insulating single crystal GaAs having a substantially planar surface wherein the (110) axis is tilted from the normal of said substantially planar surface in the direction to expose more of the (111) Ga face about 5°; a first layer of GaAs doped with Si to form N type semiconductor material epitaxially grown above said substantially planar surface; a second layer of GaAs doped with Si to form N+ type semiconductor material epitaxially grown on said first layer; an anisotropically etched trench extending through portions of said second layer, said trench having a longitudinal center line disposed parallel said planar surface and rotationally aligned such that said trench possesses first and second longitudinal sidewalls, said first sidewall being substantially vertical and said second sidewall being tilted outwardly; a third layer of electrically insulating material formed on selected exposed portions of said first layer of material along the bottom of said anisotropically etched trench; an elongate gate electrode formed on selected portions of said third layer along the bottom of said anisotropically etched trench; a drain electrode formed in ohmic contact on selected portions of said second layer, said drain electrode possessing an elongate edge disposed proximate and parallel said first longitudinal sidewall; and a source electrode formed in ohmic contact on other selected portions of said second layer, said source electrode possessing an elongate edge disposed proximate and parallel said second longitudinal sidewall.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-07-02 | 1994-01-01 | 1994-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-02 | 1998-01-01 | 1998-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-02 | 2002-01-01 | 2002-07-03 | $7700.00 | Window Closed / Lapsed |