Doped gallium oxide crystalline material and preparation method and application thereof

Abstract

A Group VB element doped with a β-gallium oxide crystalline material, and a preparation method and application thereof. The series doped with the β—Ga.sub.2O.sub.3 crystalline material is monoclinic, the space group is C2/m, the resistivity is in the range of 2.0×10.sup.−4 to 1×10.sup.4Ω.Math.cm, and/or the carrier concentration is in the range of 5×10.sup.12 to 7×10.sup.20/cm.sup.3. The preparation method comprises steps of: mixing M.sub.2O.sub.5 and Ga.sub.2O.sub.3 with a purity of 4N or more at molar ratio of (0.000000001-0.01):(0.999999999-0.99); an then performing crystal growth. The present invention can prepare a high-conductivity β-Ga.sub.2O.sub.3 crystalline material with n-type conductivity characteristics by conventional processes, providing a basis for applications thereof to electrically powered electronic devices, optoelectronic devices, photocatalysts or conductive substrates.

Claims

1. A doped gallium oxide crystalline material, wherein the gallium oxide crystalline material is doped with a Group VB element, and the gallium oxide crystalline material has a resistivity in a range of 2.0×10.sup.−4 to 1×10.sup.4Ω.Math.cm, a carrier concentration in the range of 5×10.sup.12 to 7×10.sup.20/cm.sup.3, or both; and a molecular formula of the doped gallium oxide crystalline material is Ga.sub.2 (.sub.1-x)M.sub.2O.sub.3, doped element M is vanadium (V), niobium (Nb), tantalum (Ta), or a combination thereof, and x is defined as 0.000000001 ≤x ≤0.01.

2. The doped gallium oxide crystalline material of claim 1, wherein the gallium oxide is a monoclinic crystal with a space group of C2/m.

3. The doped gallium oxide crystalline material of claim 1, wherein x is defined as 0.000001 ≤x ≤0.01.

4. The doped gallium oxide crystalline material of claim 1, wherein the doped gallium oxide crystalline material is Ta-doped —Ga.sub.2O.sub.3 crystalline material, and the Ta-doped —Ga.sub.2O.sub.3 crystalline material has a resistivity in a range of 2.0×10.sup.4 to 1×10.sup.4Ω.Math.cm, a carrier concentration in a range of 5×10.sup.12 to 7×10.sup.20/cm.sup.3, or both.

5. The doped gallium oxide crystalline material of claim 4, wherein the Ta-doped —Ga.sub.2O.sub.3 crystalline material is a Ta-doped Ga.sub.2O.sub.3 crystal, and the Ta-doped Ga.sub.2O.sub.3 crystal optionally has a resistivity in a range of 2.0×10.sup.−3 to 3.6×10.sup.2Ω.Math.cm, a carrier concentration in a range of 3.7×10.sup.15 to 6.3×10.sup.19/cm.sup.3, or both.

6. The doped gallium oxide crystalline material of claim 4, wherein the Ta-doped —Ga.sub.2O.sub.3 crystalline material is a Ta-doped Ga.sub.2O.sub.3 single crystal, and the Ta-doped Ga.sub.2O.sub.3 single crystal optionally has a resistivity in a range of 4×10.sup.−3 to 7.9Ω.Math.cm, a carrier concentration in a range of 3.7×10.sup.15 to 3.0×10.sup.19/cm.sup.3, or both.

7. The doped gallium oxide crystalline material of claim 1, wherein the doped gallium oxide crystalline material is a Nb-doped Ga.sub.2O.sub.3 crystalline material having a resistivity in a range of 2.5×10.sup.−4 to 1×10.sup.4Ω.Math.cm, a carrier concentration in a range of 5×10.sup.12 to 5.6×10.sup.20/cm.sup.3, or both.

8. The doped gallium oxide crystalline material of claim 7, wherein the Nb-doped Ga.sub.2O.sub.3 crystalline material is Nb doped Ga.sub.2O.sub.3 crystal, and the Nb-doped Ga.sub.2O.sub.3 crystal optionally has a resistivity in a range of 2.5×10.sup.−3 to 3.6×10.sup.2Ω.Math.cm, a carrier concentration in a range of 3.7×10.sup.15˜5×10.sup.19/cm.sup.3, or both.

9. The doped gallium oxide crystalline material of claim 7, wherein the Nb-doped Ga.sub.2O.sub.3 crystalline material is Nb-doped Ga.sub.2O.sub.3 single crystal, and the Nb-doped Ga.sub.2O.sub.3 single crystal optionally has a resistivity in a range of 5.5×10.sup.−3 to 36 Ω.Math.cm, a carrier concentration in a range of 9.55×10.sup.16 to 1.8×10.sup.19/cm.sup.3, or both.

10. The doped gallium oxide crystalline material according to claim 1, wherein the doped gallium oxide crystalline material is V-doped Ga.sub.2O.sub.3 crystalline material having a resistivity in a range of 2.0×10.sup.−4 to 1×10.sup.4Ω.Math.cm, a carrier concentration in a range of 5×10.sup.12 to 7×10.sup.20/cm.sup.3, or both.

11. The doped gallium oxide crystalline material according to claim 10, wherein the V-doped Ga.sub.2O.sub.3 crystalline material is V doped Ga.sub.2O.sub.3 crystal, and the V-doped Ga.sub.2O.sub.3 crystal optionally has a resistivity in a range of 2.0×10.sup.−3 to 3.6×10.sup.2Ω.Math.cm, a carrier concentration in a range of 3.7×10.sup.15 to 6.3×10.sup.19/cm.sup.3, or both.

12. The doped gallium oxide crystalline material of claim 10, wherein the V-doped Ga.sub.2O.sub.3 crystalline material is V-doped Ga.sub.2O.sub.3 single crystal, and the V-doped Ga.sub.2O.sub.3 single crystal optionally has a resistivity in a range of 3×10.sup.−2 to 50 Ω.Math.cm, a carrier concentration in a range of 5×10.sup.15 to 3.69×10.sup.18/cm.sup.3, or both.

13. A method for preparing the M-doped gallium oxide crystalline material as described in claim 1, comprising mixing M.sub.2O.sub.5 and Ga.sub.2O.sub.3, both the M.sub.2O.sub.5 and Ga.sub.2O.sub.3 having a purity of above 4N, in a molar ratio of (0.000000000001-0.01):(0.9999999-0.99) to grow crystals, obtaining the M-doped gallium oxide crystalline material, and optionally, annealing the M-doped gallium oxide crystalline material after crystal growth.

14. The method for preparing the M-doped gallium oxide crystalline material of claim 13, wherein the purity of M.sub.2O.sub.5 and Ga.sub.2O.sub.3 are both over 5N.

15. The method for preparing the M-doped gallium oxide crystalline material of claim 13, wherein the M-doped gallium oxide crystalline material is an M-doped single crystal, the purity of Ga.sub.2O.sub.3 is higher than 6N, and the molar ratio of M.sub.2O.sub.5 and Ga.sub.2O.sub.3 is in a range of (0.000001-0.01):(0.999999-0.99).

16. The method for preparing the M-doped gallium oxide crystalline material of claim 15, wherein the M-doped single crystal is grown by a melt method that is an edge defined film-fed growth (EFG) method, Czochralski method, floating zone method, or Bridgman method.

17. An M-doped gallium oxide crystalline material prepared by the method of claim 13.

18. A method for using the doped gallium oxide crystalline material of claim 1, wherein the doped gallium oxide crystalline material is applied in power electronic devices, optoelectronic devices, photocatalysts, or conductive substrates.

19. The method for using the doped gallium oxide crystalline material of claim 18, wherein the photoelectronic devices comprises transparent electrodes, solar panels, light emitting devices, photodetectors, sensors, and a combination thereof, and the conductive substrate is for GaN-based material, AlN-based material, both GaN-based and AlN-based material, or Ga.sub.2O.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing the relationship between the doping concentration of Ta.sub.2O.sub.5 (as shown in the horizontal axis (mol %)) and the carrier concentration (as shown on the vertical axis on the left (cm.sup.−3)) and resistivity (as shown on the vertical axis on the right (Ω.Math.cm)) of the Ta-doped β-Ga.sub.2O.sub.3 primary crystal of Example 1-4 in the present invention.

(2) FIG. 2 is a graph showing the relationship between the doping concentration of Ta.sub.2O.sub.5 (as shown in the horizontal axis (mol %)) after annealing and the carrier concentration (as shown on the vertical axis on the left (cm.sup.−3)) and resistivity of the Ta-doped β-Ga.sub.2O.sub.3 after annealing primary crystal of Example 1-3 in the present invention.

(3) FIG. 3 is a graph showing the relationship between the doping concentration of Nb.sub.2O.sub.5 (as shown in the horizontal axis (mol %)) and the carrier concentration (as shown on the vertical axis on the left (cm.sup.−3)) and resistivity (as shown on the vertical axis on the right (Ω.Math.cm)) of the Nb-doped β-Ga.sub.2O.sub.3 primary crystal of Example 5-9 in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention is further illustrated in the following examples, without thereby limiting the present invention to the scope of the examples. The experimental methods in the following examples which do not specify the specific conditions are selected according to conventional methods and conditions, or according to the product specifications.

(5) In the following examples, the starting materials and reagents used are commercially available.

Example 1

(6) A Ta-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Ta.sub.2xO.sub.3 (x=0.000001) and belonging to the monoclinic system and a space group of C2/m is prepared by the method and specific steps as follows:

(7) (1) Ingredients:Ga.sub.2O.sub.3 with a purity of 6N or more and Ta.sub.2O.sub.5 with a purity of 4N or more are weighed according to a molar ratio of 0.999999:0.000001;

(8) (2) Mixing: put the weighed raw materials into a clean PTFE ball mill jar, put into a high-purity corundum ball, pour the appropriate amount of absolute ethanol, seal, put into a ball mill, and mix for 12 hrs;

(9) (3) Drying: the ball grinding tank is placed in an oven, baked at 80° C. for 6 hrs, the ethanol is completely volatilized, and then placed in a ball mill for 10 minutes to grind the dried bulk material into a powder;

(10) (4) Pressure bar: the dried mixed powder is placed in an organic mold and pressed into a material bar by using an isotactic press;

(11) (5) Sintering: the pressed rod is placed in a muffle furnace and sintered at 1500° C. for 10 hrs, the moisture in the raw material is removed, and the Ta.sub.2O.sub.5 and the Ga.sub.2O.sub.3 raw material are subjected to solid phase reaction to form a polycrystalline material;

(12) (6) Crystal growth: the sintered polycrystalline rod is placed in a floating zone furnace as an upper rod, and the Ga.sub.2O.sub.3 crystal in the <010> direction is placed below as a seed crystal. First, temperature is raised to melt the seed crystal, and then the seed crystal is contacted with the upper rod to reach stabilization and initiate crystal growth. The crystal growth rate is 5 mm/hr, the rotation speed is 10 rpm, and the growth atmosphere is air atmosphere. After the crystal growth is completed, stop the dropping of the loading rod, and cause the gradual separation of the melting zone by naturally dropping the crystal underneath. After about 1 hour, the temperature slowly drops to room temperature, and the crystal is taken out. The primary crystal obtained therefrom is intact with even color and no cracking;

(13) (7) Annealing: The resulting primary crystals are annealed at 1000° C. for 3 hrs.

Example 2

(14) A Ta-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Ta.sub.2xO.sub.3 (x=0.00005) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the doping concentration of Ta.sub.2O.sub.5 in step (1) is different, and the molar ratio of Ga.sub.2O.sub.3 to Ta.sub.2O.sub.5 is 0.99995:0.00005.

Example 3

(15) A Ta-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Ta.sub.2xO.sub.3 (x=0.001), belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the doping concentration of Ta.sub.2O.sub.5 in step (1) is different, and the molar ratio of Ga.sub.2O.sub.3 to Ta.sub.2O.sub.5 is 0.999:0.001. Additionally, no annealing operation is performed.

Example 4

(16) A Ta-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Ta.sub.2xO.sub.3(x=0.01) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the doping concentration of Ta.sub.2O.sub.5 in step (1) is different, and the molar ratio of Ga.sub.2O.sub.3 to Ta.sub.2O.sub.5 is 0.99:0.01. No annealing operation is performed.

Example 5

(17) A Nb-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Nb.sub.2xO.sub.3 (x=0.000001) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (Nb.sub.2O.sub.5) and doping concentration of Nb.sub.2O.sub.5 in step (1) are different.

Example 6

(18) A Nb-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Nb.sub.2xO.sub.3 (x=0.00001) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (Nb.sub.2O.sub.5) and doping concentration of Nb.sub.2O.sub.5 in step (1) are different.

Example 7

(19) A Nb-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Nb.sub.2xO.sub.3 (x=0.0001) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (Nb.sub.2O.sub.5) and doping concentration of Nb.sub.2O.sub.5 in step (1) are different. No annealing operation is performed.

Example 8

(20) A Nb-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Nb.sub.2xO.sub.3 (x=0.002) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (Nb.sub.2O.sub.5) and doping concentration of Nb.sub.2O.sub.5 in step (1) are different. No annealing operation is performed.

Example 9

(21) A Nb-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)Nb.sub.2xO.sub.3 (x=0.008) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (Nb.sub.2O.sub.5) and doping concentration of Nb.sub.2O.sub.5 in step (1) are different. No annealing operation is performed.

Example 10

(22) A V-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)V.sub.2xO.sub.3 (x=0.01) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (V.sub.2O.sub.5) and doping concentration of V.sub.2O.sub.5 in step (1) are different. No annealing operation is performed.

Example 11

(23) A V-doped β-Ga.sub.2O.sub.3 single crystal with a molecular formula of Ga.sub.2(1-x)V.sub.2xO.sub.3 (x=0.00001) and belonging to the monoclinic system and a space group of C2/m is prepared by the same steps and conditions as in Example 1, except that the dopant (V.sub.2O.sub.5) and doping concentration of V.sub.2O.sub.5 in step (1) are different. No annealing operation is performed.

Comparative Example

(24) A pure β-Ga.sub.2O.sub.3 single crystal without Ta.sub.2O.sub.5 doping is prepared by the same steps and conditions as in Example 1.

(25) The M-doped maple-Ga.sub.2O.sub.3 single crystals obtained in Examples 1-11 and the pure Ga.sub.2O.sub.3 single crystal in the comparative example are cut into samples with the size of 5 mm×5 mm×0.3 mm. Four (4) Indium (In) electrodes are fabricated on four corners of each of the samples and Hall measurements are taken. All samples show N-type conductivity and detail results of carrier concentration and resistivity as shown in Table 1.

(26) TABLE-US-00001 TABLE 1 Carrier concentration and resistivity of different examples carrier concentration (/cm.sup.3) Resistivity (Ω .Math. cm) Examples Dopants as-grown after annealing as-grown after annealing Example1 Ta = 0.000001  7.12 × 10.sup.17 3.7 × 10.sup.15 0.13 7.9 Example2 Ta = 0.00005  1.44 × 10.sup.18 5.4 × 10.sup.16 0.04 0.86 Example3 Ta = 0.001  6.3 × 10.sup.18 1.7 × 10.sup.17 0.02 — Example4 Ta = 0.01  3.0 × 10.sup.19 — 0.004 — Example5 Nb = 0.000001 2.014 × 10.sup.18 9.554 × 10.sup.16  0.07746 36.63 Example6 Nb = 0.00001 7.484 × 10.sup.18 2.613 × 10.sup.17  0.01584 2.065 Example7 Nb = 0.0001 1.596 × 10.sup.18 — 0.09291 — Example8 Nb = 0.002 8.818 × 10.sup.18 — 0.009181 — Example9 Nb = 0.008 1.812 × 10.sup.19 — 0.005523 — Example10 V = 0.01  3.69 × 10.sup.18 0.03 Example11 V = 0.000001  2.68 × 10.sup.17 — 0.54 — Contrastive —  3.96 × 10.sup.14 exceeding 67 exceeding example limit of limit of detection detection (>10.sup.5)

(27) According to the data from Table 1, the pure crystal of Ga.sub.2O.sub.3 is almost insulated after annealing. Compared with the pure crystal, the carrier concentration and conductivity of Ga.sub.2O.sub.3 single crystal doped with Group VB elements increase significantly, and the carrier concentration increase at least 10.sup.3 times and the resistivity decrease at least 500 times, indicating that M metal ions have been successfully doped into the lattice of Ga.sub.2O.sub.3 and achieve desired control effect.

(28) Further, in order to study the relationship between different doping concentrations and carrier concentration or resistivity, the Ta.sub.2O.sub.5 doping concentration-carrier concentration-resistivity curve of samples without annealing in Examples 1-4 are shown in FIG. 1. Examples 5-9 correspond to the curve of Nb.sub.2O.sub.5 doping concentration-carrier concentration-resistivity, as shown in FIG. 3. In addition, in order to study the relationship between the doping concentration of Ta.sub.2O.sub.5 and carrier concentration after annealing, the present invention draws the doping concentration-carrier concentration curve of the sample annealed in Examples 1-4 as shown in FIG. 2.

(29) It can be seen from FIGS. 1 and 3 that there is a linear relationship between M.sub.2O.sub.5 doping concentration and carrier concentration, and between M.sub.2O.sub.5 doping concentration and resistivity. Within the doping concentration range of the present invention, the carrier concentration increases linearly and the resistivity decreases linearly with the increase of M.sub.2O.sub.5 doping concentration before annealing. As shown in FIG. 2, the carrier concentration decreases after annealing.

(30) It should be noted that the carrier concentration and resistivity of the above Group VB elements doped Ga.sub.2O.sub.3 single crystal are obtained by the specific experiments of the present invention. Due to the influence of the purity of raw materials, preparation technology and test conditions, the measured carrier concentration and resistivity of the doped crystal will be different from the theoretical value, or there is a situation that can not be detected. Therefore, the above examples are merely illustrations. According to the Group VB element doping concentration disclosed by the present invention and the common knowledge in the field, it can be inferred that the carrier concentration of the Group VB element doped Ga.sub.2O.sub.3 crystalline material can be controlled in the range of 5×10.sup.12 to 7×10.sup.20/cm.sup.3, and the resistivity can be controlled in the range of 2.0×10.sup.−4 to 1×10.sup.4Ω.Math.cm. Taking Ta as an example, the specific calculation process is as follows.

(31) According to the experiment of the present invention, the maximum value of Ta-doping concentration in the Ga.sub.2O.sub.3 single crystal is 1 at % (i.e. x=0.01). The volume of 1 mol-Ga.sub.2O.sub.3 is 184.44/5.94 cm.sup.3=31 cm.sup.3;

(32) The number of Ta atoms in 1 mol Ta-doped Ga.sub.2O.sub.3 is: 1×2×1%×6.023×10.sup.23=1.2×10.sup.22; therefore, the theoretical value of carrier concentration of Ta-doped Ga.sub.2O.sub.3 is 2×1.2×10.sup.22/31=7.7×10.sup.20/cm.sup.3.

(33) The Hall effect instrument with low resistance module is used to test the resistivity below the limit value of 10.sup.5Ω.Math.cm. The experiment of the present invention shows that the resistivity of 6N pure Ga.sub.2O.sub.3 crystal exceeds the test limit after annealing, indicating that the resistivity of 6N pure Ga.sub.2O.sub.3 crystal exceeds 10.sup.5Ω.Math.cm. Therefore, the resistivity of 6N pure Ga.sub.2O.sub.3 doped with Ta can be controlled to 1×10.sup.4Ω.Math.cm, which is 1/1266 of Example 1. The carrier concentration in the example is multiplied by 1/1266, 3×10.sup.12/cm.sup.3 can be obtained, so it is feasible to achieve 5×10.sup.12/cm.sup.3 carrier concentration in Ta-doped—Ga.sub.2O.sub.3 crystal material. The doping concentration of Ta corresponding to the doping concentration is 10.sup.−7 at %.

(34) Therefore, the amount of Ta doping in Ta-doped Ga.sub.2O.sub.3 crystalline materials can be controlled in the range of x=0.000000001 to 0.01, the resistivity can be controlled in the range of 2.0×10.sup.−4 to 1×10.sup.4Ω.Math.cm, and the carrier concentration can be controlled in the range of 5×10.sup.12 to 7×10.sup.20/cm.sup.3.

(35) Other doped elements including Nb and V may be calculated by the same method.

(36) The examples of the present invention are described above. However, the examples mentioned are only examples for illustration and are not intended to limit the present invention. Technicians in the field may make a number of changes and modifications without departing from the spirit and scope of the present invention. The scope of protection advocated by the present invention shall prevail as described in the claims.