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US4959702A
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Si-GaP-Si heterojunction bipolar transistor (HBT) on Si substrate
Assignee: NXP USA Inc
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Filing: 1989-10-05
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Granted: 1990-09-25
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Expires: 2009-10-05
Abstract
Abstract A heterojunction bipolar transistor (HBT) is provided having a silicon substrate in which a conventional junction base is formed. A coherently strained layer of semiconductor material having a wider band gap than silicon, such as gallium phosphide, is formed over the base to form a first portion of an emitter multilayer. A second portion of the emitter multilayer comprises silicon which can be epitaxially grown on the coherently strained layer. A thin heteropotential barrier is thus formed at the base-emitter junction which preferentially allows electrons to move from emitter to base while significantly reducing hole current from base to emitter, thereby improving emitter injection efficiency and current gain.
Inventors
- 👤 Curtis D. Moyer
- 👤 Raymond K. Tsui
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:14
CPC Classifications
H; H10; H10D; H10D10/00; H10D10/80; H10D10/821; H10D10/891
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
60 words
A heterojunction bipolar transistor (HBT) comprising: a silicon collector layer of a first conductivity type; a base region of a second conductivity type formed adjacent to the collector layer; an epitaxially grown gallium phosphide (GaP) region formed on top of of the base region; and an epitaxially grown silicon emitter of the first conductivity type formed over the GaP region.
Claim 2
Dependent Claim
60 words
A heterojunction bipolar transistor (HBT) comprising: a silicon collector layer of a first conductivity type; a base region of a second conductivity type formed adjacent to the collector layer; an epitaxially grown gallium phosphide (GaP) region formed on top of of the base region; and an epitaxially grown silicon emitter of the first conductivity type formed over the GaP region.
Claim 3
Dependent Claim
17 words
The HBT of claim 1 wherein the GaP region is from 0.01 microns to 0.03 microns thick.
Claim 4
Dependent Claim
16 words
The HBT of claim 1 wherein the GaP region is essentially free of lattice mismatch defects.
Claim 5
Dependent Claim
80 words
A heterojunction bipolar transistor (HBT) comprising: a silicon layer of a first conductivity type which serves as a collector; a base region of a second conductivity type formed on the silicon layer of a first conductivity type; an epitaxially grown coherently strained region formed on top of the base region, wherein the coherently strained region has a wider bandgap than that of silicon; and an epitaxially grown silicon emitter of the first conductivity type formed over the coherently strained region.
Claim 6
Dependent Claim
80 words
A heterojunction bipolar transistor (HBT) comprising: a silicon layer of a first conductivity type which serves as a collector; a base region of a second conductivity type formed on the silicon layer of a first conductivity type; an epitaxially grown coherently strained region formed on top of the base region, wherein the coherently strained region has a wider bandgap than that of silicon; and an epitaxially grown silicon emitter of the first conductivity type formed over the coherently strained region.
Claim 7
Dependent Claim
21 words
The HBT of claim 4 wherein the coherently strained region comprises a material with a lattice constant which closely matches silicon.
Claim 8
Dependent Claim
30 words
The HBT of claim 4 wherein the thickness of the coherently strained region is such that hole tunneling through the coherently strained region is significantly less probable than electron tunneling.
Claim 9
Dependent Claim
14 words
The HBT of claim 4 wherein the silicon emitter has a graded doping concentration.
Claim 10
Dependent Claim
14 words
The HBT of claim 4 wherein the silicon emitter has an abrupt doping concentration.
Claim 11
Dependent Claim
54 words
A heterojunction bipolar transistor (HBT) comprising: a silicon substrate of a first conductivity type which serves as a collector; a base region of a second conductivity type formed in the substrate; an emitter multilayer formed in contact with the base region, wherein the emitter multilayer forms a valence band discontinuity with the base region.
Claim 12
Dependent Claim
54 words
A heterojunction bipolar transistor (HBT) comprising: a silicon substrate of a first conductivity type which serves as a collector; a base region of a second conductivity type formed in the substrate; an emitter multilayer formed in contact with the base region, wherein the emitter multilayer forms a valence band discontinuity with the base region.
Claim 13
Dependent Claim
15 words
The HBT of claim 9 wherein the valence band discontinuity is greater than 0.25 eV.
Claim 14
Dependent Claim
41 words
The HBT of claim 9 wherein the emitter multilayer comprises a GaP layer which is formed in contact with the base region and a silicon emitter layer of the first conductivity type which is formed in contact with the GaP layer.
References Cited (Backward Citations)
US4617724A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-09-24 | 1994-03-26 | 1994-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-09-24 | 1998-03-26 | 1998-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-09-24 | 2002-03-26 | 2002-09-25 | $7700.00 | Window Closed / Lapsed |