Polarization field enhanced tunnel structures

• US 20030151042A1
• Filed: 02/08/2002
• Published: 08/14/2003
• Est. Priority Date: 02/08/2002
• Status: Active Grant

• Current Assignee: Broadcom International Pte Ltd. (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Hueschen, Mark R.
• Granted Patent: US 6,878,975 B2
• Time in Patent Office: Days
• US Class Current: 257/12
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/88 Tunnel-effect diodes
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01S 5/3095 Tunnel junction

Abstract

A novel tunnel structure is described that enables tunnel diode behavior to be exhibited even in material systems in which extremely heavy doping is impossible and only moderate or light doping levels may be achieved. In one aspect, the tunnel heterostructure includes a first semiconductor layer, a second semiconductor layer, and an intermediate semiconductor layer that is sandwiched between the first and second semiconductor layers and forms first and second heterointerfaces respectively therewith. The first and second heterointerfaces are characterized by respective polarization charge regions that produce a polarization field across the intermediate semiconductor layer that promotes charge carrier tunneling through the intermediate semiconductor layer. In another aspect, the invention features a semiconductor structure having a p-type region, and the above-described heterostructure disposed as a tunnel contact between the p-type region of the semiconductor structure and an adjacent n-type region.

Claims

1. A heterostructure, comprising:

a first semiconductor layer;

a second semiconductor layer; and

an intermediate semiconductor layer sandwiched between the first and second semiconductor layers and forming first and second heterointerfaces respectively therewith, wherein the first and second heterointerfaces are characterized by respective polarization charge regions producing a polarization field across the intermediate semiconductor layer promoting charge carrier tunneling through the intermediate semiconductor layer.

2. The heterostructure of claim 1, wherein the intermediate semiconductor layer has a thickness (D) enabling charge carriers to tunnel through the intermediate semiconductor layer with a current density greater than 1 A/cm².

3. The heterostructure of claim 2, wherein the polarization field has a magnitude (ξ

_p) on the order of (E_c,1−

E_v,2)/(q·

D), wherein E_c,1 is a relative conduction band energy at the first heterointerface, E_v,2 is a relative valence band energy at the second heterointerface, q is a unit carrier charge, and D is the thickness of the intermediate semiconductor layer.

4. The heterostructure of claim 2, wherein the polarization field has a magnitude (ξ

_p) sufficient to align conduction band states at the Fermi level at the first heterointerface with valence band states at the Fermi level at the second heterointerface.

5. The heterostructure of claim 1, wherein the first semiconductor layer is doped n-type and the second semiconductor layer is doped p-type.

6. The heterostructure of claim 5, wherein the polarization field enhances a dopant-induced drift field produced between the first and second semiconductor layers.

7. The heterostructure of claim 1, wherein the first and second semiconductor layers are formed from the same semiconductor material.

8. The heterostructure of claim 7, wherein the first and second semiconductor layers are formed from GaN and the intermediate semiconductor layer is formed from AlGaN.

9. The heterostructure of claim 7, wherein the first and second semiconductor layers are formed from GaN and the intermediate semiconductor layer is formed from InGaN.

10. The heterostructure of claim 1, wherein the first, second and intermediate semiconductor layers are characterized by crystallographic structures allowing spontaneous polarization charge formation at the first and second heterointerfaces.

11. The heterostructure of claim 10, wherein each of the first, second and intermediate semiconductor layers has a hexagonal crystallographic structure.

12. The heterostructure of claim 10, wherein each of the first, second and intermediate semiconductor layers is formed from a III-V nitride semiconductor material.

13. The heterostructure of claim 12, wherein each of the first, second and intermediate semiconductor layers is formed from a semiconductor material selected from the group consisting of:

GaN, AlGaN, InGaN, AlN, InN, InAlN.

14. The heterostructure of claim 10, wherein each of the first, second and intermediate semiconductor layers is formed from a II-VI semiconductor material.

15. The heterostructure of claim 1, wherein each of the first and second heterointerfaces is characterized by a substantial piezoelectric charge formation.

16. A heterostructure, comprising:

a semiconductor structure having a p-type region; and

a tunnel contact structure disposed between the p-type region of the semiconductor structure and an adjacent n-type region, wherein the tunnel contact structure includes,

a first semiconductor layer coupled to the n-type region and doped n-type,

a second semiconductor layer coupled to the p-type region of the semiconductor structure and doped p-type, and

an intermediate semiconductor layer sandwiched between the first and second semiconductor layers and forming first and second heterointerfaces respectively therewith, wherein the first and second heterointerfaces are characterized by respective polarization charge regions producing a polarization field across the intermediate semiconductor layer promoting charge carrier tunneling through the intermediate semiconductor layer.

17. The heterostructure of claim 16, wherein the semiconductor structure comprises a light emitting region.

18. The heterostructure of claim 16, wherein the intermediate semiconductor layer has a thickness (D) enabling charge carriers to tunnel through the intermediate semiconductor layer with a current density greater than 1 A/cm².

19. The heterostructure of claim 18, wherein the polarization field has a magnitude (ξ

_p) sufficient to align conduction band states at the Fermi level at the first heterointerface with valence band states at the Fermi level at the second heterointerface.

20. The heterostructure of claim 16, wherein each of the first, second and intermediate semiconductor layers is formed from a III-V nitride semiconductor material or a II-VI semiconductor material.