Process for the manufacture of a doped III-N bulk crystal and a free-standing III-N substrate, and doped III-N bulk crystal and free-standing III-N substrate as such

• US 8,778,078 B2
• Filed: 08/08/2007
• Issued: 07/15/2014
• Est. Priority Date: 08/09/2006
• Status: Active Grant

• Current Assignee: Freiberger Compound Materials GMBH (Federmann House Limited)
• Original Assignee: Freiberger Compound Materials GMBH (Federmann House Limited)
• Inventors: Scholz, Ferdinand, Brckner, Peter, Habel, Frank, Leibiger, Gunnar
• Primary Examiner(s): SONG, MATTHEW J
• Application Number:
  US11/835,669
• Publication Number:
  US 20080083910A1
• Time in Patent Office: 2,533 Days
• Field of Search: 117/84, 117/88, 117/99, 117/91, 117/952
• US Class Current: 117/99
• CPC Class Codes: C30B 25/00 Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/165 the flow of the reactive gases
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 29/2003 Nitride compounds

Abstract

A process for producing a doped III-N bulk crystal, wherein III denotes at least one element of the main group III of the periodic system, selected from Al, Ga and In, wherein the doped crystalline III-N layer or the doped III-N bulk crystal is deposited on a substrate or template in a reactor, and wherein the feeding of at least one dopant into the reactor is carried out in admixture with at least one group III material. In this manner, III-N bulk crystals and III-N single crystal substrates separated therefrom can be obtained with a very homogeneous distribution of dopants in the growth direction as well as in the growth plane perpendicular thereto, a very homogeneous distribution of charge carriers and/or of the specific electric resistivity in the growth direction as well as in the growth plane perpendicular thereto, and a very good crystal quality.

Claims

1. A process for producing a doped III-N bulk crystal, comprising:

depositing a doped III-N bulk crystal, wherein III denotes at least one element of the main group III of the periodic system selected from Al, Ga and In, on a substrate or a template in a reactor, by a process that includes bringing species of at least one group III material and of at least one dopant into a vapor phase together and in admixture,

feeding vaporized species of the at least one group III material and of the at least one dopant, or reaction products thereof, in mixed form into the reactor or towards a growth region of the reactor,

feeding an N starting material into the reactor or towards a growth region of the reactor, and

growing the doped III-N bulk crystals at a growth rate of about 200 to about 1000 μ

m/h,

wherein the doped III-N bulk crystal is formed with a homogeneous incorporation of the dopant into the III-N crystal, such that the produced doped III-N bulk crystal satisfies at least one of the following conditions (a) to (c);

(a) in a micro-Raman mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the measured frequency positions of the LPP⁺-mode

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower;

(b) in an MDP mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the photoconductivity signals

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower;

(c) in a micro photoluminescence mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the line width of the D⁰X transition

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower.

2. The process according to claim 1, wherein the mixed feeding is carried out by feeding a combined material in which at least one dopant has been added to the at least one group III starting material.

3. The process according to claim 1, wherein the mixed feeding is carried out by feeding a mixture of the at least one dopant in elemental form and the at least one group III starting material in elemental form.

4. The process according to claim 1, wherein said species of the at least one Group III starting material and the at least one dopant are brought into a vapor phase together and in admixture from a solid solution, an alloy, or a mixed melt.

5. The process according to claim 1, wherein, the feeding further comprises feeding, separately from the mixed feeding,

at least one dopant alone or in combination with at least one group III material, or

at least one group III material without a dopant.

6. The process according to claim 1, wherein said depositing comprises depositing a doped III-N bulk crystal by means of vapor phase epitaxy in a vapor phase epitaxy reactor on a substrate or template.

7. The process according to claim 1, wherein the depositing comprises a hydride vapor phase epitaxy growth method.

24. A process for producing a free-standing doped III-N crystal substrate, wherein III denotes at least one element of the main group III of the periodic system, selected from Al, Ga and In, comprising:

a) carrying out the process according to claim 1, and

b) separating one or more doped III-N substrates.

25. The process according to claim 24, wherein the separating comprises wire sawing, and further comprising at least one treatment step following subsequently, selected from lapping, polishing, annealing and final cleaning steps.

8. A process for producing a doped III-N bulk crystal, wherein III denotes at least one element of the main group III of the periodic system, selected from Al, Ga and In, in a reactor for hydride vapor phase epitaxy (HVPE), having a common source and/or a common feed-line for feeding a group III starting material and a dopant into the HVPE reactor, comprising:

feeding a halide reaction gas into, or towards, at least one of the common source and the common feed-line to form a mixture of halides of the group III starting material and the dopant;

feeding the mixture to a growth region of the HVPE reactor;

feeding an N starting material into the HVPE reactor, and

growing the doped III-N bulk crystal at a growth rate of about 200 to about 1000 μ

m/h,

wherein the doped crystalline III-N layer or the doped III-N bulk crystal is formed with a homogeneous incorporation of the dopant into the III-N crystal, such that the produced doped III-N bulk crystal satisfies at least one of the following conditions (a) to (c);

(a) in a micro-Raman mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the measured frequency positions of the LPP⁺-mode

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower;

(b) in an MDP mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the photoconductivity signals

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower;

(c) in a micro photoluminescence mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the line width of the D⁰X transition

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower.

9. A process for producing a doped III-N bulk crystal, whereby III denotes at least one element of the main group III of the periodic system, selected from Al, Ga and In, comprising;

contacting a solid solution, an alloy or a mixed melt, respectively, comprising the element of the main group III of the periodic system and the element of the dopant for the III-N material of the doped III-N bulk crystal, with a reaction gas to form mixed products of the group III element and the dopant, respectively, with a component of the reaction gas in vapor phase;

contacting the thus formed mixed products with an N-starting material in vapor phase;

growing the doped III-bulk crystal at a growth rate of about 200 to about 1000 μ

m/h, on a substrate or template a III-N bulk crystal with dopant being homogeneously incorporated, such that the produced doped III-N bulk crystal satisfies at least one of the following conditions (a) to (c);

(a) in a micro-Raman mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the measured frequency positions of the LPP⁺-mode

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower;

(b) in an MDP mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the photoconductivity signals

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower;

(c) in a micro photoluminescence mapping on a plane

(i) parallel to a growth plane and/or

(ii) in a growth direction,

a standard deviation of the line width of the D⁰X transition

in case of (i) is 5% or lower, and

in case of (ii) is 10% or lower.

10. The process according to claim 9, wherein the reaction gas comprises HCl or another chloride, optionally mixed with carrier gas, to form mixed products comprising chlorides of the group III element and of the dopant.

11. The process according to claim 9, wherein the amount of dopant in the solid solution, the alloy or the mixed melt lies in the range of higher than 0 wt.-% of the total weight of dopant and group III element up to the solubility limit of the dopant in the solid solution, the alloy or the mixed melt.

12. The process according to claim 9, wherein a mixed melt is contacted with the reaction gas and wherein the mixed melt contains an amount of dopant exceeding the solubility limit of the dopant in the mixed melt.

13. The process according to claim 9, further comprising, in advance of growing the doped III-N bulk crystal, depositing at least one intermediate layer as a base layer, the composition of which is chosen independently from that of the doped III-N bulk crystal.

14. The process according to claim 9, wherein a doped or undoped III-N substrate having a c-, a-, m- or r-plane as growth plane is used as a substrate for depositing the doped III-N bulk crystal on the growth plane.

15. The process according to claim 9, wherein a doped or undoped III-N substrate with a growth plane having a misorientation of 0.1-30°

C. towards a c-, a-, m- or r-plane is used as a substrate for depositing the doped III-N bulk crystal thereon.

16. The process according to claim 9, wherein the dopant is selected from the group consisting of silicon, tellurium, magnesium, iron, germanium, tin, selenium, beryllium, vanadium, manganese, zinc, chrome, nickel, copper and a mixture thereof.

17. The process according to claim 9, wherein the doped III-N bulk crystal has an almost circular cross-section, and the diameter of the substrate or template and of the III-N bulk crystal is ≧

5 cm, respectively.

18. The process according to claim 9, wherein the length of the doped, grown III-N bulk crystal is ≧

0.1 mm.

19. The process according to claim 18, wherein the length of the doped, grown III-N bulk crystal is ≧

1 mm.

20. The process according to claim 18, wherein the length of the grown doped III-N bulk crystal is ≧

1 cm.

21. The process according to claim 18, wherein the length of the grown doped III-N bulk crystal is ≧

3 cm.

22. The process according to claim 9, wherein the substrate is selected from the group consisting of single-crystalline sapphire, silicon carbide, gallium arsenide, lithium aluminate and silicon.

23. The process according to claim 9, wherein a doped or undoped GaN substrate is used as the substrate, or a foreign substrate coated with GaN is used as the template.