Process for obtaining of bulk monocrystalline gallium-containing nitride

• US 7,364,619 B2
• Filed: 04/17/2003
• Issued: 04/29/2008
• Est. Priority Date: 06/26/2002
• Status: Expired due to Term

• Current Assignee: Ammono Sp. Z O.O., Nichia Corporation
• Original Assignee: Ammono Sp. Z O.O., Nichia Corporation
• Inventors: Kanbara, Yasuo, Doradzinski, Roman, Garczynski, Jerzy, Dwilinski, Robert, Sierzputowski, Leszek P.
• Primary Examiner(s): HITESHEW, FELISA CARLA
• Application Number:
  US10/519,141
• Publication Number:
  US 20060032428A1
• Time in Patent Office: 1,839 Days
• Field of Search: 117/81, 117/83
• US Class Current: 117/81
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 7/00 Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions from molten solvents C30B9/00; by normal or gradient freezing C30B11/00; under a protective fluid C30B27/00
• CPC Class Codes: C30B 7/005 Epitaxial layer growth

Abstract

The invention relates to new improvements in a process for crystal growth in the environment of supercritical ammonia-containing solution, which are based on use of specific azide mineralizers and result in the improved bulk Group XIII element nitride monocrystals, in particular balk monocrystalline gallium-containing nitride, intended mainly for variety of nitride-based semiconductor products such as various opto-electronic devices. The invention further relates to a mineralizer used for supercritical ammonia-containing solution which comprises at least one compound selected from the group consisting of LiN₃, NaN₃, KN₃, and CsN₃.

Claims

1. A process for obtaining a bulk gallium-containing nitride monocrystal, comprising:

contacting ammonia with a mineralizer comprising a Group I azide in a pressurized reaction vessel to form a supercritical ammonia-containing solution comprising an ion of a Group I element;

dissolving a gallium-containing feedstock at a dissolution temperature and pressure condition under which the gallium feedstock dissolves in the supercritical ammonia-containing solution; and

crystallizing a gallium-containing nitride on a surface of a seed at a crystallization temperature and pressure condition,

wherein the crystallization temperature and pressure condition is determined using a temperature coefficient of solubility and a pressure coefficient of solubility of the gallium-containing nitride to be crystallized.

2. The process according to claim 1, wherein gaseous nitrogen, produced during decomposition of the azide, is at least partially evacuated before the crystallizing step is started.

3. The process according to claim 1, wherein the crystallized gallium-containing nitride has a general formula Al_xGa_1-xN, where 0≦

x<

1.

4. The process according to claim 1, wherein the mineralizer is selected from the group consisting of LiN₃, NaN₃, KN₃, CsN₃ and mixtures thereof.

5. The process according to claim 4, wherein the mineralizer contains at least one compound selected from the group consisting of LiN₃, NaN₃, KN₃ and CsN₃.

6. The process according to claim 5, wherein the mineralizer contains NaN₃ and KN₃.

7. The process according to claim 5, wherein the mineralizer contains NaN₃ and LiN₃.

8. The process according to claim 5, wherein the mineralizer contains KN₃ and LiN₃.

9. The process according to claim 5, wherein the mineralizer further contains Group I element-containing compound other than azide.

10. A process according to claim 9, wherein the mineralizer further comprises a Group II element-containing compound other than an azide.

11. The process according to claim 1, wherein the Group I azide is added in a molar ratio of azide to ammonia ranging from 1:

200 to 1;

2.

12. The process according to claim 1, wherein the seed comprises a crystalline layer of Group XIII element-containing nitride having a dislocation density less than 10⁷/cm².

13. The process according to claim 1, wherein the seed comprises a structure having a number of surfaces spaced apart from each other, arranged on a primary substrate and susceptible to a lateral overgrowth of a crystalline nitride.

14. The process according to claim 1, wherein a monocrystalline nitride layer that is obtained has the same or better quality as the gallium-containing nitride monocrystal gets thicker.

15. The process according to claim 13, wherein the seed contains the primary substrate made of a crystalline nitride of Group XIII element.

16. The process according to claim 15, wherein the seed contains the primary substrate made of gallium nitride.

17. The process according to claim 15, wherein the seed contains the primary substrate made of a crystalline material such as sapphire, spinel, ZnO, SiC or Si, and wherein the primary substrate made of a material reactive to a supercritical ammonia-containing solution is covered with a protective layer prior to formation of a monocrystalline nitride layer.

18. A process according to claim 17, wherein the protective layer comprises a Group XIII element-containing nitride or a metallic Ag.

19. The process according to claim 1, wherein the bulk nitride monocrystal obtained consists essentially of gallium nitride.

20. The process according to claim 1, wherein the bulk nitride monocrystal obtained contains any of the following elements:

Ni, Cr, Co, Ti, Fe, Al, Ag, Mo, W, Si and Mn.

21. The process according to claim 1, wherein a surface of the seed is covered with a mask layer prior to formation of a monocrystalline nitride layer.

22. A process according to claim 1, wherein the mineralizer further comprises a Group II azide and the supercritical ammonia-containing solution further comprises an ion of a Group II element.

24. A process according to claim 2, wherein the mineralizer further comprises a Group II azide and the supercritical ammonia-containing solution further comprises an ion of a Group II element.

23. A process for obtaining a bulk gallium-containing nitride monocrystal, comprising:

contacting ammonia with a mineralizer comprising a Group I azide in a pressurized reaction vessel at a condition under which a gallium-containing nitride has a negative temperature coefficient of solubility and a positive pressure coefficient of solubility, forming a supercritical ammonia-containing solution comprising an ion of a Group I element;

dissolving a gallium-containing feedstock at a dissolution temperature and pressure condition under which the gallium-containing feedstock dissolves in the supercritical ammonia-containing solution;

obtaining a super-saturation of the supercritical ammonia-containing solution at a crystallization temperature and pressure condition having a temperature higher than that of the dissolution temperature and pressure condition or a pressure lower than that of the dissolution temperature and pressure condition; and

crystallizing a gallium-containing nitride on a surface of a seed by maintaining the super-saturation of the supercritical ammonia-containing solution at the level at which spontaneous crystallization of nitride is negligible.

25. A method for creating an epitaxial layer on a nitride monocrystal, comprising:

contacting ammonia with a mineralizer comprising a Group I azide in a pressurized reaction vessel to form a supereritical ammonia-containing solution comprising an ion of a Group I element;

dissolving a gallium-containing feedstock at a dissolution temperature and pressure condition under which the gallium feedstock dissolves in the supereritical ammonia-containing solution;

crystallizing a gallium-containing nitride on a surface of a seed at a crystallization temperature and pressure condition to obtain a nitride monocrystal,

wherein the crystallization temperature and pressure condition is determined using a temperature coefficient of solubility and a pressure coefficient of solubility of the gallium-containing nitride to be crystallized; and

growing an epitaxial layer on the nitride monocrystal.

26. The method of claim 25, wherein the bulk nitride monocrystal has at least one epitaxial layer of the same or different Group XIII element-containing nitride, deposited by a MOCVD, HVPE or MBE method as a template for opto-electronic devices.

27. The method of claim 26, wherein the epitaxial layer is doped with one or more dopants.