High on-state breakdown heterojunction bipolar transistor

• US 20060049485A1
• Filed: 06/14/2005
• Published: 03/09/2006
• Est. Priority Date: 08/19/2004
• Status: Active Grant

• Current Assignee: MicroLink Devices, Inc.
• Original Assignee: MicroLink Devices, Inc.
• Inventors: Pan, Noren, Wibowo, Andree
• Granted Patent: US 7,687,886 B2
• Time in Patent Office: Days
• US Class Current: 257/565
• CPC Class Codes: H01L 29/0817 of heterojunction bipolar transistors H01L29/7375 takes precedence
• CPC Class Codes: H01L 29/0821 Collector regions of bipolar transistors
• CPC Class Codes: H01L 29/7371 Vertical transistors

Abstract

A heterojunction bipolar transistor (HBT) is provided with an improved on-state breakdown voltage V_CE. The improvement of the on-state breakdown voltage for the HBT improves the output power characteristics of the HBT and the ability of the HBT to withstand large impedance mismatch (large VSWR). The improvement in the on-state breakdown voltage is related to the suppression of high electric fields adjacent a junction of a collector layer and a sub-collector layer forming a collector region of the HBT.

Claims

1. A heterojunction bipolar transistor, comprising

a substrate;

a collector region having a plurality of layers of a first material, each of the plurality of layers of the first material having a distinct impurity concentration;

a base region having at least one layer of said first material;

an emitter region having at least one layer of a second material; and

a contact region having a first layer of said first material and a second layer of a third material;

wherein the collector region reduces an electric field adjacent to two of the plurality of layers of the first material to improve a drain source on-state breakdown voltage of the heterojunction bipolar transistor.

2. The heterojunction bipolar transistor of claim 1, wherein the substrate comprises a semi-insulating material.

3. The heterojunction bipolar transistor of claim 1, wherein the first material comprises GaAs.

4. The heterojunction bipolar transistor of claim 1, wherein the plurality of layers of the collector region comprises;

a sub-collector layer of the first material;

a first collector layer of the first material;

a second collector layer of the first material; and

a third collector layer of the first material.

5. The heterojunction bipolar transistor of claim 4, wherein the first collector layer has a thickness of between about 200 nm and about 400 nm.

6. The heterojunction bipolar transistor of claim 4, wherein the second collector layer has a thickness of between about 200 nm and about 400 nm.

7. The heterojunction bipolar transistor of claim 4, wherein the third collector layer has a thickness of between about 100 nm and about 500 nm.

8. The heterojunction bipolar transistor of claim 1, wherein the second material comprises InGaP.

9. The heterojunction bipolar transistor of claim 1, wherein the second material comprises Al_xGa_1-xAs (0<

x<

0.35).

10. The heterojunction bipolar transistor of claim 1, wherein the second material comprises (Al_xGa_1-x)_0.49In_0.51P (0<

x<

0.35).

11. The heterojunction bipolar transistor of claim 1, wherein the third material comprises In_0.5Ga_0.5As.

12. A heterojunction bipolar transistor, comprising

a substrate;

a collector region having a plurality of layers of a first material and a layer of a second material, each of the layers of the first and second materials having a distinct impurity concentration;

a base region having at least one layer of said first material;

an emitter region having at least one layer of a third material; and

a contact region having a first layer of said first material and a second layer of a fourth material;

wherein the collector region reduces an electric field adjacent to two adjacent layers of the plurality of layers of said collector region to improve a drain-source on-state breakdown voltage of the heterojunction bipolar transistor.

13. The heterojunction bipolar transistor of claim 12, wherein the first material comprises GaAs.

14. The heterojunction bipolar transistor of claim 12, wherein the second material comprises AlGaAs.

15. The heterojunction bipolar transistor of claim 12, wherein the third material comprises InGaP.

16. The heterojunction bipolar transistor of claim 12, wherein the fourth material comprises In_0.5Ga_0.5As.

17. The heterojunction bipolar transistor of claim 12, wherein the plurality of layers of the first material of the collector region comprises,

a sub-collector layer of the first material;

a first collector layer of the first material; and

a second collector layer of the first material.

18. The heterojunction bipolar transistor of claim 17, wherein the first collector layer of the first material has a thickness of between about 200 nm and about 400 nm.

19. The heterojunction bipolar transistor of claim 17, wherein the second collector layer of the first material has a thickness of between about 200 nm and about 400 nm.

20. The heterojunction bipolar transistor of claim 17, wherein the sub-collector layer has a thickness of between about 100 nm and about 500 nm.

21. The heterojunction bipolar transistor of claim 17, wherein in the collector region the layer of the second material of has a thickness of about 200 nm.

22. The heterojunction bipolar transistor of claim 17, wherein the substrate comprises a semi-insulating material.

23. A heterojunction bipolar transistor, comprising

a substrate;

a collector region having a first layer of a first material and at least a second layer of the first material, the second layer having a gradually varied doping concentration from a first surface to a second surface of the second layer;

a base region having at least one layer of said first material;

an emitter region having at least one layer of a second material; and

a contact region having a first layer of said first material and a second layer of a third material;

wherein the collector region reduces an electric field adjacent to a first surface of the first layer of the first material and a first surface of the second layer of the first material to improve a drain source on-state breakdown voltage of the heterojunction bipolar transistor.

24. The heterojunction bipolar transistor of claim 23, wherein the first material comprises GaAs.

25. The heterojunction bipolar transistor of claim 23, wherein the doping concentration of the at least second layer of the first material forming a portion of the collector region increases in concentration from the first surface of the second layer adjacent a surface of the base region to the second surface of the second layer adjacent a first surface of the first layer of collector region.

26. The heterojunction bipolar transistor of claim 23, wherein the first layer of the first material of the collector region comprises, a sub-collector layer of the first material.

27. The heterojunction bipolar transistor of claim 23, wherein the second layer of the first material of the collector region comprises, a collector layer of the first material.