(Sc,Y):AIN SINGLE CRYSTALS FOR LATTICE-MATCHED AIGaN SYSTEMS

Abstract

The invention concerns a method for the production of single crystal aluminium nitride doped with scandium and/or yttrium, with scandium and/or yttrium contents in the range 0.01 atom % to 50 atom % with respect to 100 atom % of the total quantity of the doped aluminium nitride, characterized in that in a crucible, in the presence of a gas selected from nitrogen or a noble gas, or a mixture of nitrogen and a noble gas: a doping material selected from scandium, yttrium, scandium nitride or yttrium nitride or a mixture thereof
and a source material formed from aluminium nitride
are sublimated and recondensed onto a seed material which is selected from aluminium nitride or aluminium nitride doped with scandium and/or yttrium.

The invention also concerns a corresponding device as well as the corresponding single crystal products and their use, whereupon the basis for novel components based on layers or stacks of layers of aluminium gallium nitride, indium aluminium nitride or indium aluminium gallium nitride is generated.

Claims

1. A method for the production of single crystal aluminium nitride doped with scandium and/or yttrium, with scandium and/or yttrium contents in the range 0.01 atom % to 50 atom % with respect to 100 atom % of the total quantity of the doped aluminium nitride, wherein in a crucible, in the presence of a gas selected from nitrogen or a noble gas, or a mixture of nitrogen and a noble gas: a) a doping material selected from scandium, yttrium, scandium nitride or yttrium nitride or a mixture thereof; and b) a source material formed from aluminium nitride are sublimated and recondensed onto a seed material which is selected from aluminium nitride or aluminium nitride doped with scandium and/or yttrium.

2. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein the temperature of the doping material is 1K to 400K higher than the temperature of the source material.

3. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein the temperature of the doping material is the same as or lower than the temperature of the source material.

4. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein the temperature of the source material is 1K to 300K higher than the temperature of the seed material.

5. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein the total gas pressure is in the range 10 to 1200 mbar, preferably in the range 200 to 1000 mbar, particularly preferably in the range 500 to 900 mbar.

6. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein a heating means is disposed or can be disposed outside the crucible, preferably at least in the lower region of the crucible, wherein the temperature provided by the heating means is in the range 1500 C. to 2700 C.

7. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein the seed material is disposed or can be disposed in the crucible separated from or separable from the source and doping material, separated from or separable from or disposed or can be disposed above the source and doping material.

8. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein in the crucible, the source and doping material are completely or partially admixed, sintered or present as aluminium nitride doped with scandium and/or yttrium.

9. The method for the production of single crystalline aluminium nitride doped with scandium and/or yttrium of claim 1, wherein in the crucible, the source and doping materials are spatially separated or separable or spaced apart or can be spaced apart, wherein the mean separation of the doping material from the seed material is less than the mean separation of the source material from the seed material.

10. Single crystal aluminium nitride doped with yttrium, produced in accordance with the method of claim 1.

11. Single crystal aluminium nitride doped with scandium and yttrium, produced in accordance with the method of claim 1.

12. Single crystal aluminium nitride doped with scandium, having geometric dimensions of at least 3 mm3 mm100 m, produced in accordance with the method of claim 1.

13. Single crystal aluminium nitride doped with yttrium, having geometric dimensions of at least 3 mm3 mm100 m, produced in accordance with the method of claim 1.

14. Single crystal aluminium nitride doped with scandium and yttrium, having geometric dimensions of at least 3 mm3 mm100 m, produced in accordance with the method of claim 1.

15. Use of single crystal aluminium nitride doped with scandium in accordance with the method of claim 1, as a substrate (wafer) for the production of layers or stacks of layers formed from aluminium gallium nitride, indium aluminium nitride or indium aluminium gallium nitride, preferably with a layer thickness of more than 2 nm, more preferably with a layer thickness of 100 nm to 50 m.

16. Use of single crystal aluminium nitride doped with yttrium as a substrate (wafer) for the production of layers or stacks of layers formed from aluminium gallium nitride, indium aluminium nitride or indium aluminium gallium nitride, preferably with a layer thickness of more than 2 nm, more preferably with a layer thickness of 100 nm to 50 m.

17. Use of single crystal aluminium nitride doped with scandium and yttrium as a substrate (wafer) for the production of layers or stacks of layers formed from aluminium gallium nitride, indium aluminium nitride or indium aluminium gallium nitride, preferably with a layer thickness of more than 2 nm, more preferably with a layer thickness of 100 nm to 50 m.

18. A component comprising a first layer consisting of layers or stacks of layers of aluminium gallium nitride, indium aluminium nitride or indium aluminium gallium nitride which are on single crystalline aluminium nitride substrates doped with scandium and/or yttrium, which are produced in accordance with the method of claim 1.

19. The component of claim 18, comprising at least one further layer formed from crystalline aluminium nitride or a layer formed from aluminium gallium nitride, which contains more aluminium (as an atomic percentage) than the first layer.

20. A device, in particular for carrying out the method of claim 1, in particular for the production of single crystal aluminium nitride doped with scandium and/or yttrium, with scandium and/or yttrium contents in the range 0.01 atom % to 50 atom % with respect to 100 atom % total quantity of the doped aluminium nitride, comprising a crucible which in a first region, is provided with a first means in which a seed material can be accommodated or is, and in a second region, is provided with at least one second means in which a source material and/or a doping material can be accommodated or is/are accommodated.

21. The device of claim 20, characterized in that the at least one second means in which a source and/or a doping material can be or is/are accommodated comprises at least two said second means, of which one is configured to accommodate the source material and the other is configured to accommodate the doping material, wherein the mean separation of the second means for accommodating the doping material from the first means for accommodating the seed material is less than the mean separation of the second means for accommodating the source material from the first means for accommodating the seed material.

22. The device of claim 21, characterized in that the second means for accommodating the source material is formed by the lower inner region of the crucible and the second means for accommodating the doping material is disposed or can be disposed above the means for accommodating the source material and below the means for accommodating the seed.

23. The device of claim 21, wherein the lower region of the crucible has a thicker wall than in the upper region, which has an approximately horizontal upper face.

24. The device of claim 21, characterized in that in the inside of the crucible within the thicker wall, a separate crucible is disposed or can be disposed which forms the second means for accommodating the source material, and/or one or more heat shields, with a further separate device which is disposed or can be disposed thereon.

25. The device of claim 23, wherein the upper face of the thicker wall and/or the further separate device which is disposed on the heat shield(s) forms the second means for accommodating the doping material.

Description

EXAMPLES

Example 1Investigation of Nitriding of Sc by TG/DTA Measurements

[0109] Sc in graphite crucible in stream of N.sub.2 to 1640 C., rate of heating 10 K/min

[0110] Nitriding of scandium in accordance with the following reaction:

Sc+N.sub.2-->ScN

[0111] commences from 1000 C., with a strong exothermic peak at 1375 C.

[0112] The phase composition of the reaction product produced pure ScN.

Example 2PVT of Sc:AlN (Crucible Design as Shown in FIG. 2.1)

[0113] Up to 1% by weight of Sc intimately mixed into AlN source material

[0114] Tp.sub.y,o=2030 C., t=15 h; growth rate 180 m/h

[0115] AlN seed, h=5 mm; top diameter 3 mm

[0116] As a result, a hexagonally grown crystal was obtained:

[0117] Diameter 78 mm; h=8 mm (sample reference FZ_221, see FIG. 3)

[0118] The crystal was sawn into one a-plane wafer and four c-plane wafers. Chemo-mechanical polishing (CMP) was used to obtain uniform thin layers (both sides). Sc was found in all of the wafers (EDX, XRF), with uniform Sc distribution in c-plane wafers (EDX, XRF).

[0119] The result of the X-ray fluorescence analysis (XRF, line scan c-plane capping layer) is shown in FIG. 4. The ScN concentration was between 0.3 atom % and 0.35 atom % this corresponded to ScN in AlN or 0.65 atom % to 0.7 atom % Sc in ScAl.

[0120] This gives: Sc.sub.0.007Al.sub.0.993N

[0121] The variations in the Sc concentration result from the unevenness of the capping layer.

[0122] The result of the X-ray fluorescence analysis (XRF, line scan c-plane capping layer) in the vicinity of the seed is shown in FIG. 5.

[0123] The ScN concentration was between 0.3 atom % and 0.4 atom % ScN in AlN, or 0.6 atom % to 0.8 atom % Sc in ScAl. An increasing Sc concentration was observed in en-plane grown AlN. This gives as a maximum: Sc.sub.0.008Al.sub.0.992N

[0124] The increasing Sc concentration in the a-plane wafer (XRF) was 0.4 atom % ScN; the result of the XRF is shown in FIG. 6. The ScN concentration was between 0.3 atom % and 0.4 atom % ScN in AlN;

[0125] The rocking curve for the capping layer of sample FZ_221 (as-grown) was 33.1 arcsec and is shown in FIG. 7 (primary beam apertures 2 and 0.05 mm; open detector).

[0126] The result indicates the presence of several grains.

[0127] Determination of Lattice Parameters (XRD Etc).:

TABLE-US-00001 AlN ScAlN Sample CH879 FZ_221 (capping layer) a 3.1113 3.11287 0.00157 c 4.9812 4.981996

[0128] For Sc.sub.xAl.sub.1-xN, using the Da according to Morarn (2014) produced:

[0129] Sc.sub.0.009Al.sub.0.991Nthis corresponds to 0.9 atom % Sc or 0.45 atom % ScN

[0130] The result compared well with the XRF values given above.

Example 3PVT of Sc:AlN with Crucible Configuration as Shown in FIG. 2.2b (Sample FZ_266)

[0131] Tp.sub.y,o=2030 C.; t=15 h; p=600 mbar

[0132] The aim was to obtain a very good quality hexagonal crystal:

[0133] One centre of growth (Nomarski),

[0134] Rocking curve, capping layer=21.4 arcsec (shown in FIG. 8)

Lattice Constant (XRD):

[0135]

TABLE-US-00002 AlN ScAlN Sample CH879 FZ_266 (capping layer) a 3.1113 3.1132 0.0019 c 4.9812 4.9822

[0136] For Sc.sub.xAl.sub.1-xN, using the Da according to Moram (2014) produced:

[0137] Sc.sub.0.0097Al.sub.0.9903Nthis corresponds to 0.97 atom % Sc or 0.48 atom % ScN

[0138] The XRD line scan on the capping layer of the sample FZ_266 produced a ScN content of approximately 0.4 atom % ScN.

[0139] Overall, the agreement with the XRD values was good.

Example 4Doping of AlN with Y or (Sc,Y)

[0140] Doping of AlN with yttrium or (Sc,Y) was carried out in a manner analogous to that for scandium. The success of the doping was based on the comparatively small partial pressure difference for Sc and Y (FIG. 1) in connection with similar ionic radii of 73 pm for Sc and 93 pm for Y.

BRIEF DESCRIPTION OF THE FIGURES

[0141] FIG. 1 partial pressure of Sc, Y and Al in presence of AlN as a function of temperature at 600 mbar (FactSage);

[0142] FIG. 2.1 crucible 3 with crucible cover 2; inside is the source material 4 and the doping material 5; the seed 1 is attached to the cover 2;

[0143] FIG. 2.2 source material 4 and doping material 5 separated in different zones of the crucible

[0144] 2.2a) the doping material 5 is on an apertured diaphragm 6 which functions to inhibit the vaporization of the source material kinetically;

[0145] 2.2b) the doping material 5 is in a small crucible 7 below the seed 1; the design also includes an apertured diaphragm 6 on the source material 4;

[0146] FIG. 2.3 crucible 11, 11a, 11b with different wall thicknesses with separate crucible 10 in the lower region, heat shield 9 (crucible height may exceed that of heat shield), seed 1 on crucible cover 2; additional crucible opening 12 to reduce vaporization of source material (cooling)

[0147] 2.3 a) doping material 5 in central, hot region of crucible on a step or the like, i.e. on surface 11c;

[0148] 2.3 b) doping material 5 on small apertured diaphragm 8 which is either on the inner heat shield or directly on the crucible 10, apertured diaphragm serves to accommodate the doping material and for orientated vaporization of source material 4 in the direction of the seed 1;

[0149] 2.3 c) doping material 5 both on apertured diaphragm (small) 8 and on step in crucible 11, i.e. on surface 11c; apertured diaphragm 8 is either on inner heat shield or directly on the crucible 10;

[0150] 2.3 d) doping material 5 both on apertured diaphragm (small) 8 and on step in crucible 11, i.e. on surface 11c; apertured diaphragm 8 is either on inner heat shield or directly on the crucible 10; additional heating of the doping material 5 by graphite contact 13 (formed from graphite, etc) between susceptor and crucible wall installed outside the crucible 11;

[0151] FIG. 2.4 long crucible 16;

[0152] 2.4a) with diaphragm 14 to accommodate doping material (powder/granulate/etc); with and without external contact 13, source material 4 in lower region of crucible;

[0153] 2.4b) with step 15 to accommodate doping material (powder/granulate/etc); with and without external contact 13, source material 4 in lower region of crucible;

[0154] FIG. 3 Sc:AlN single crystal, as-grown (sample FZ_221);

[0155] FIG. 4 XRF line scan over the as-grown capping layer of sample FZ_221;

[0156] FIG. 5 XRF line scan over a c-plane wafer near seed in sample FZ_221;

[0157] FIG. 6 XRF line scan over an a-plane wafer (FZ_221);

[0158] FIG. 7 rocking curve of Sc:AlN capping layer FZ_221; primary beam apertures 2 and 0.05 mm; open detector; result indicates the presence of a plurality of grains;

[0159] FIG. 8 rocking curve of capping layer of Sc:AlN (FZ_266); peak width at half height of 21.4 arcsec;

[0160] FIG. 9 XRF line scan on capping layer (FZ_266), ScN content at approximately 0.4 atom % ScN.

LIST OF REFERENCE NUMERALS

[0161] 1seed/seed material [0162] 2crucible cover [0163] 3crucible (large) [0164] 4source material/AlN source [0165] 5doping material [0166] 6apertured diaphragm (large) [0167] 7small crucible/smaller (inner) crucible (to accommodate doping material) [0168] 8apertured diaphragm (small) [0169] 9heat shield(s) [0170] 10crucible (small)/separate crucible (inner) in lower region to accommodate source material [0171] 11crucible with steps/(differing) wall thicknesses [0172] 11aupper crucible region (with thinner wall) [0173] 11bthick-walled crucible region [0174] 11c-(upper) face of thick-walled crucible region [0175] 12opening [0176] 13graphite contact [0177] 14diaphragm [0178] 15step [0179] 16long crucible

LITERATURE

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