Double heterojunction group III-nitride structures

• US 9,231,064 B1
• Filed: 08/12/2014
• Issued: 01/05/2016
• Est. Priority Date: 08/12/2014
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Reza, Shahed, Chumbes, Eduardo M., Kazior, Thomas E., Sollner, Gerhard
• Primary Examiner(s): Payen, Marvin
• Assistant Examiner(s): Joy, Jeremy
• Application Number:
  US14/457,436
• Time in Patent Office: 511 Days
• Field of Search: 257/194, 257/E29.246, 257/E29.251, 257/E21.408, 438/172
• US Class Current: 1/1
• CPC Class Codes: H01L 21/2654 in AIIIBV compounds
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/205 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/36 characterised by the concentration or distribution of impurities in the bulk material within semiconductor regions H01L29/06
• CPC Class Codes: H01L 29/365 Planar doping, e.g. atomic-plane doping, delta-doping
• CPC Class Codes: H01L 29/66462 with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
• CPC Class Codes: H01L 29/7784 with delta or planar doped donor layer H01L29/7785 takes precedence
• CPC Class Codes: H01L 29/7786 with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
• CPC Class Codes: H01L 29/7787 with wide bandgap charge-carrier supplying layer, e.g. direct single heterostructure MODFET
• CPC Class Codes: H01L 29/7788 Vertical transistors
• CPC Class Codes: H01L 29/7789 the two-dimensional charge carrier gas being at least partially not parallel to a main surface of the semiconductor body

Abstract

A semiconductor structure having: a Group III-N channel layer, a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer; and a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer. The channel layer has disposed therein a predetermined n-type conductive dopant.

Claims

1. A semiconductor structure, comprising:

a Group III-N channel layer;

a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer;

a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer;

wherein the Group III-N channel layer has disposed therein a doped region having predetermined n-type conductive dopant; and

wherein the doped region is a delta-doped region having a peak doping concentration a predetermined finite distance from the upper surface of the channel layer and a predetermined finite distance from the lower surface of the channel layer.

2. The semiconductor structure recited in claim 1 wherein the peak doping concentration is in a range of 1×

10¹²/cm² to 2×

10¹³/cm².

3. The semiconductor structure recited in claim 1 wherein the heterojunction formed with the upper surface of the channel layer produces a 2 Dimensional Electron Gas (2DEG) region in the III-N channel layer and wherein the peak doping concentration of the delta-doped region is at a predetermined position in the channel layer, the position being in a range, R, extending from 5 nanometers above a lower surface of the III-N channel layer to 5 nanometers below an upper surface of the III-N channel layer.

4. The semiconductor structure recited in claim 3 wherein the delta-doped region has a width δ

, here is 1-3 atomic layers (<

2 nm).

5. The semiconductor structure recited in claim 1 wherein the channel layer is GaN, the top-barrier polarization-generating layer is AlGaN having a mole concentration in a range of 20-35%, and the back-barrier polarization-generating layer is AlGaN having a mole concentration in a range of 3-8%.

6. The semiconductor structure recited in claim 5 wherein the top-barrier polarization-generating layer has a thickness in a range of 15-30 nm and the back-barrier polarization-generating layer has a thickness greater than 20 nm.

7. The semiconductor structure recited in claim 1 wherein the channel layer is n-type doped GaN having a thickness in a range of 10-50 nm.

8. The semiconductor structure recited in claim 7 wherein the top-barrier polarization-generating layer is AlGaN having a mole concentration in a range of 20-35%, and the back-barrier polarization-generating layer is AlGaN having a mole concentration in a range of 3-8%.

9. The semiconductor structure recited in claim 8 wherein the top-barrier polarization-generating layer has a thickness in a range of 15-30 nm and the back-barrier polarization-generating layer has a thickness greater than 20 nm.

10. The semiconductor structure recited in claim 1 including a source electrode over a first surface portion of the structure, a drain electrode over a second surface portion of the structure;

and a gate electrode over a third portion of the structure, the gate electrode controlling a flow of carriers between the source electrode and the drain electrode through the channel layer.

22. The structure recited in claim 1 wherein the heterojunction formed with the upper surface of the channel layer produces a 2 Dimensional Electron Gas (2DEG) region in the III-N channel layer.

11. A semiconductor structure, comprising:

a GaN channel layer having an n-doped region;

a first AlGaN layer forming a heterojunction with an upper surface of the channel layer;

a second AlGaN layer forming a heterojunction with a lower surface of the channel layer; and

wherein the heterojunction formed with the upper surface of the channel layer produces a 2 Dimensional Electron Gas (2DEG) region in the III-N channel layer.

12. The semiconductor structure recited in claim 11 wherein the doped region is a delta-doped region having a peak doping concentration a predetermined distance from the upper surface of the channel layer and the lower surface of the channel layer.

13. The semiconductor structure recited in claim 12 wherein the peak doping concentration is in a range of 1×

10¹²/cm² to 2×

10¹³/cm².

14. The semiconductor structure recited in claim 12 wherein the heterojunction formed with the upper surface of the channel layer produces a 2 Dimensional Electron Gas (2DEG) region in the III-N channel layer and wherein the peak doping concentration of the delta-doped region is at a predetermined position in the channel layer, the position being in a range, R, extending from 5 nanometers above a lower surface of the channel layer to 5 nanometers below an upper surface of the channel layer.

15. The semiconductor structure recited in claim 14 wherein the doping spike has width δ

, where δ

is 1-3 atomic layers (<

2 nm).

16. The semiconductor structure recited in claim 11 including a source electrode over a first surface portion of the structure, a drain electrode over a second surface portion of the structure;

and a gate electrode over a third portion of the structure, the gate electrode controlling a flow of carriers between the source electrode and the drain electrode through the n-doped GaN channel layer.

17. A semiconductor structure, comprising:

a Group III-N channel layer;

a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer and producing a 2D Electron Gas (2-DEG) region in the Group III-N channel layer;

a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer, the back-barrier polarization-generating layer reducing charge density in the 2D Electron Gas (2-DEG) region in the Group III-N channel layer;

wherein the Group III-N channel layer has disposed therein a doped region having a predetermined amount of n-type conductive dopant, the predetermined amount of n-type conductive dopant being selected to replace the charge density reduced in the 2D Electron Gas (2-DEG) region.

18. A method for forming a semiconductor structure having:

a Group III-N channel layer;

a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer and producing a 2D Electron Gas (2-DEG) region in the Group III-N channel layer; and

a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer, the back-barrier polarization-generating layer reducing charge density in the 2D Electron Gas (2-DEG) region, the method comprising;

providing a predetermined amount of n-type conductivity dopant in the Group III-N channel layer, the predetermined amount of introduced n-type conductivity dopant provided being related to the reduced charge density in the 2D Electron Gas (2-DEG) region channel.

19. The method recited in claim 18 wherein the doped region is a delta-doped region having a peak doping concentration at a predetermined distance from the upper surface of the channel layer and the lower surface of the channel layer.

20. The method recited in claim 18 including determining amount of charge density reduced by the back-barrier polarization-generating layer and using the determined amount of charge density reduced by the back-barrier polarization-generating layer to determine the predetermined amount of n-type conductivity dopant provided in the Group III-N channel layer.

21. The method recited in claim 20 wherein the doped region is a delta-doped region having a peak doping concentration at a predetermined distance from the upper surface of the channel layer and the lower surface of the channel layer.

23. A method for forming a semiconductor structure having:

a Group III-N channel layer;

a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer and producing a 2D Electron Gas (2-DEG) region in the Group III-N channel layer; and

a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer, the back-barrier polarization-generating layer reducing charge density in the 2D Electron Gas (2-DEG) region, the method comprising;

providing a predetermined amount of n-type conductivity dopant in the Group III-N channel layer, the predetermined amount of introduced n-type conductivity dopant being selected to compensate for the reduced charge density in the 2D Electron Gas (2-DEG) region channel.

24. The method recited in claim 23 wherein the doped region is a delta-doped region having a peak doping concentration a predetermined distance from the upper surface of the channel layer and the lower surface of the channel layer.

25. The method recited in claim 23 including determining amount of charge density reduced by the back-barrier polarization-generating layer and using the determined amount of charge density reduced by the back-barrier polarization-generating layer to determine the predetermined amount of n-type conductivity dopant provided in the Group III-N channel layer.

26. The method recited in claim 25 wherein the doped region is a delta-doped region having a peak doping concentration a predetermined distance from the upper surface of the channel layer and the lower surface of the channel layer.

27. A method for forming a semiconductor structure having:

a Group III-N channel layer;

a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer and producing a 2D Electron Gas (2-DEG) region in the Group III-N channel layer; and

a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer, the back-barrier polarization-generating layer reducing charge density in the 2D Electron Gas (2-DEG) region, the method comprising;

determining the amount of reduced charge density in the 2D Electron Gas (2-DEG) region; and

providing a predetermined amount of n-type conductivity dopant in the Group III-N channel layer, the predetermined amount of introduced n-type conductivity dopant provided being related to the determined amount of reduced charge density in the 2D Electron Gas (2-DEG) region channel.