Gallium oxide-based heterojunction and growth method thereof

Abstract

The invention discloses a gallium oxide-based heterojunction and a growth method thereof, relates to a semiconductor heterojunction technology, and aims to solve the problem of lack of a high-quality single-domain gallium oxide heterojunction in the prior art. Patterning a specified growth region of gallium oxide on the substrate by using a first mask, and laterally growing epsilon-phase gallium oxide crystals on the specified growth region and then healing the epsilon-phase gallium oxide crystals; and isolating the mixed domain part by using a second mask, carrying out secondary growth on the exposed single domain part to obtain a high-quality single domain gallium oxide film, and finally preparing aluminum gallium oxide to form a final device. The method has the advantages that the grown epsilon-phase gallium oxide single crystal has no in-plane rotation domain, the crystal structure is uniform and consistent, the crystal quality is high, and the surface appearance is flat. And the grown heterojunction has a flat interface and can be applied to subsequent high-quality epsilon-phase gallium oxide heterojunction devices. Meanwhile, the pattern preparation method is compatible with the semiconductor technological process and can be used for large-size batch growth.

Description

TECHNICAL FIELD

[0001] The present application relates to semiconductor heterojunction technology, and in particular to a gallium oxide-based heterojunction and a growth method thereof. BACKGROUND

[0002] Gallium oxide is one of the popular materials for ultraviolet detectors, transparent electrode materials and high-power electronic devices due to its band gap of up to ~4.5-4.9 eV. The epsilon phase gallium oxide is the second stable phase of gallium oxide materials. Unlike the most stable beta phase gallium oxide, the epsilon phase gallium oxide has a spontaneous polarization effect. Theoretical calculation results show that the epsilon phase gallium oxide can produce a high concentration of two-dimensional electron gas, which is expected to be higher than the aluminum gallium nitride / gallium nitride heterojunction, and is a very promising material.

[0003] Since the epsilon phase gallium oxide is a metastable phase, there is a lack of means to grow single crystal substrates, so the epsilon phase gallium oxide can only be grown by heteroepitaxy. The metal organic chemical vapor deposition technology has the advantages of high thin film crystalline quality, smooth thin film surface, good thin film uniformity and fast growth speed. At the same time, the metal organic chemical vapor deposition technology can realize the uniform growth of large-scale and large-size thin films, and the control of doping is more convenient, which meets the needs of the semiconductor industry for thin film epitaxy. It is the most commonly used method for heteroepitaxy of epsilon phase gallium oxide at present. The commonly used substrates for heteroepitaxy of epsilon phase gallium oxide include sapphire, silicon carbide, gallium nitride, aluminum nitride, etc. However, due to the mismatch of crystal symmetry between the epsilon phase gallium oxide and the substrate, the epsilon phase gallium oxide grown on the substrate by heteroepitaxy has a serious in-plane rotational domain defect problem, resulting in a class, b class and c class of rotational domains, and the three domains present an in-plane 120° rotation. Research literature (CrystEngComm, 19, 1509, 2017) confirms that the formation of the rotational domain of the epsilon phase gallium oxide is due to the mismatch of the substrate and the orthogonal phase gallium oxide to the substrate, resulting in an in-plane 120° rotation. Therefore, high-quality epsilon phase gallium oxide single crystals without rotational domains cannot be grown by traditional heteroepitaxy, which further leads to the inability to realize single-domain epsilon phase aluminum gallium oxide, and ultimately leads to the inability to realize high-quality epsilon phase aluminum gallium oxide / gallium oxide heterojunction. The document CN109148351A (Al x Ga 1-x )2O3 / Ga2O3 device epitaxial layer transfer method has a related description. The (Al x Ga 1-x )2O3 / Ga2O3 in the document is the aluminum gallium oxide described in the present application. The epsilon phase is one of the phases of aluminum gallium oxide, and is generally represented by epsilon-(Al x Ga 1-x )2O3 / Ga2O3.

[0004] Due to the lack of single-domain epsilon phase gallium oxide single crystal material, the high-quality heterostructure of epsilon phase gallium oxide cannot be realized at present, which seriously affects the development and application of epsilon phase gallium oxide heterojunction devices. Therefore, a growth method is needed to realize the growth of single-domain epsilon phase gallium oxide single crystal. And for mass production, the introduced growth method should be compatible with large-size manufacturing. SUMMARY

[0005] The present application aims to provide a gallium oxide-based heterojunction and a growth method thereof to solve the problems existing in the prior art.

[0006] The gallium oxide-based heterojunction in the present application has mixed-domain epsilon phase gallium oxide grown on a substrate; a patterned first barrier layer is arranged on the surface of the mixed-domain epsilon phase gallium oxide; the first barrier layer has an empty window area, and the mixed-domain epsilon phase gallium oxide extends upward through the first barrier layer in the empty window area; a second barrier layer is arranged on the top end of the part of the mixed-domain epsilon phase gallium oxide that extends through the first barrier layer; the second barrier layer completely covers the part of the mixed-domain epsilon phase gallium oxide that extends through the first barrier layer; single-domain epsilon phase gallium oxide is grown on the outside of the part of the mixed-domain epsilon phase gallium oxide that extends through the first barrier layer, above the first barrier layer, and above the second barrier layer; an epsilon phase aluminum gallium oxide layer is arranged on the upper end surface of the single-domain epsilon phase gallium oxide; the epsilon phase aluminum gallium oxide layer and the single-domain epsilon phase gallium oxide form a heterojunction;

[0007] The width of the first barrier layer is d1, and the width of the empty window is w1;

[0008] The width of the second barrier layer is w2, and the interval between adjacent second barrier layers is d2;

[0009] The distance from the side surface of the mixed-domain epsilon phase gallium oxide to the first barrier layer is L;

[0010] Each dimension satisfies the following relationship:

[0011] w1+d1=w2+d2;

[0012] w2>w1+2*L;

[0013] w1≤d1;

[0014] 50μm≥d1≥3μm.

[0015] The substrate is one of sapphire, silicon carbide, gallium nitride, and aluminum nitride.

[0016] The first barrier layer is parallel to the <112 _ 0> direction of sapphire, or the <101 _ 0> direction of sapphire, or the <112 _ 0> direction of sapphire, or the <101 _0> crystal orientation, or gallium nitride <112 _ 0> crystal orientation, gallium nitride <101 _ 0> crystal orientation, or aluminum nitride <112 _ 0> crystal orientation, or aluminum nitride <101 _ 0> Crystal orientation.

[0017] The first barrier layer and / or the second barrier layer are silicon dioxide, metal, or silicon nitride.

[0018] The thickness of the second barrier layer is greater than 10 nm.

[0019] The method for growing a gallium oxide-based heterojunction as described in this invention includes the following steps:

[0020] S1. Gallium oxide crystal is grown on the substrate;

[0021] S2. A patterned first barrier layer is deposited on a gallium oxide crystal, wherein the first barrier layer exposes predetermined portions of the gallium oxide crystal at intervals using window areas;

[0022] S3. Gallium oxide crystals are further grown on the exposed gallium oxide crystal area using lateral epitaxy, and the grown gallium oxide crystals are healed in the lateral region; the gallium oxide crystals above the window area and the gallium oxide crystals between the first barrier layer and the substrate are both mixed-domain crystals, and the mixed-domain crystals above the window area extend laterally a distance L towards the upper end face of the first barrier layer; the gallium oxide crystals between adjacent mixed-domain crystals above the window area are single-domain crystals;

[0023] S4. A patterned second barrier layer is prepared at the top of the mixed-domain crystal above the void region; the second barrier layer completely covers the portion of the mixed-domain ε-phase gallium oxide that penetrates the first barrier layer;

[0024] S5. Continue growing gallium oxide crystal to obtain a gallium oxide thin film with single domains on the top;

[0025] S6. An ε-phase aluminum gallium oxide layer is prepared on the gallium oxide thin film to obtain the target device.

[0026] The gallium source used for gallium oxide crystal growth is one of trimethylgallium, triethylgallium, and gallium chloride; the oxygen source used is one or more of oxygen, nitrous oxide, and water.

[0027] The temperature used for growing the gallium oxide crystal is between 500℃ and 800℃.

[0028] The gallium oxide-based heterojunction and the growth method thereof have the advantages that the grown epsilon phase gallium oxide single crystal has no in-plane rotation domain, the crystal structure is uniform and consistent, the crystallization quality is high, and the surface morphology is flat. The grown heterojunction interface is flat, and can be used for subsequent high-quality epsilon phase gallium oxide heterojunction device applications. At the same time, the patterning method is compatible with the semiconductor process, and can be used for large-size batch growth. On the other hand, compared with the prior art patent document CN 116666196A, the present patent uses a patterned mask to achieve 100% filtering of rotation domains on various substrates, and the prepared epsilon phase aluminum gallium oxide surface is flat and smooth. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a structural schematic diagram of the gallium oxide-based heterojunction described in the present application.

[0030] Figure 2 is Figure 1 a sectional view of A-A in

[0031] Figure 3 is a flowchart of the growth method described in the present application Figure 1 .

[0032] Figure 4 is a flowchart of the growth method described in the present application Figure 2 .

[0033] Figure 5 is a flowchart of the growth method described in the present application Figure 3 .

[0034] Figure 6 is a flowchart of the growth method described in the present application Figure 4 .

[0035] Figure 7 is Figure 6 a sectional view of the structure shown in

[0036] Figure 8 is Figure 7 a partial enlarged view of

[0037] Figure 9 is a flowchart of the growth method described in the present application Figure 5 .

[0038] Figure 10 is a surface morphology diagram of the gallium oxide-based heterojunction described in the present application under an optical microscope.

[0039] Figure 11 is a surface morphology diagram of the sample prepared in the comparative example under an optical microscope

[0040] Figure reference numerals: 100-substrate, 301-mixed-domain ε-phase gallium oxide, 302-single-domain ε-phase gallium oxide, 401-first barrier layer, 402-second barrier layer, 500-ε-phase aluminum gallium oxide layer. Detailed Implementation

[0041] like Figure 1 and Figure 2 As shown, the gallium oxide-based heterojunction of the present invention comprises a mixed-domain ε-phase gallium oxide 301 grown on a substrate 100. A patterned first barrier layer 401 is disposed on the surface of the mixed-domain ε-phase gallium oxide 301. The first barrier layer 401 has a window region through which the mixed-domain ε-phase gallium oxide 301 extends upward through the first barrier layer 401. A second barrier layer 402 is disposed at the top of the portion of the mixed-domain ε-phase gallium oxide 301 that extends through the first barrier layer 401. The second barrier layer 402 completely covers the portion of the mixed-domain ε-phase gallium oxide 301 that extends through the first barrier layer 401. Single-domain ε-phase gallium oxide 302 is grown on the outer side of the portion of the mixed-domain ε-phase gallium oxide 301 that extends through the first barrier layer 401, above the first barrier layer 401, and above the second barrier layer 402. An ε-phase aluminum gallium oxide layer 500 is deposited on the upper surface of the single-domain ε-phase gallium oxide 302. The ε-phase aluminum gallium oxide layer 500 and the single-domain ε-phase gallium oxide 302 form a heterojunction.

[0042] The width of the first blocking layer 401 is d1, and the width of the open window is w1.

[0043] The width of the second barrier layer 402 is w2, and the interval between adjacent second barrier layers 402 is d2.

[0044] The distance from the side of the mixed-domain ε-phase gallium oxide 301 to the first barrier layer 401 is L.

[0045] Each dimension satisfies the following relationship:

[0046] w1+d1=w2+d2.

[0047] w2>w1+2*L.

[0048] w1≤d1.

[0049] 50μm≥d1≥3μm.

[0050] The substrate 100 is one of sapphire, silicon carbide, gallium nitride, and aluminum nitride. The first barrier layer 401 is parallel to the sapphire <112 _ 0> crystal orientation, or sapphire <101 _ 0> crystal orientation, or silicon carbide <112 _ 0> crystal orientation, or silicon carbide <101 _ 0> crystal orientation, or gallium nitride <112 _0> crystal orientation, or gallium nitride <101 _ 0> crystal orientation, or aluminum nitride <112 _ 0> crystal orientation, or aluminum nitride <101 _ 0> crystal orientation.

[0051] The first barrier layer 401 and / or the second barrier layer 402 is silicon dioxide or metal or silicon nitride, wherein the metal material can be used as a bottom electrode lead-out in subsequent application. The thickness of the second barrier layer 402 is greater than 10 nm, which ensures that the subsequent gallium oxide crystal growth will not be disturbed by the underlying mixed domain crystal.

[0052] The gallium oxide-based heterojunction growth method in the application comprises the following steps:

[0053] S1. Growing a gallium oxide crystal on a substrate 100.

[0054] S2. Laying a patterned first barrier layer 401 on the gallium oxide crystal, wherein the first barrier layer 401 exposes the preset part of the gallium oxide crystal through the air window area, as shown in FIG. 2. Figure 3

[0055] S3. Continuing to grow the gallium oxide crystal on the exposed part of the gallium oxide crystal by using lateral epitaxy technology. The first grown part is the corresponding gallium oxide crystal above the air window area of the first barrier layer 401, as shown in FIG. 3. At this time, all the gallium oxide crystals are mixed domain crystals, and the mixed domain crystal above the air window area extends to the upper surface of the first barrier layer 401 by a distance L. Figure 4

[0056] Continuing lateral epitaxy and healing the grown gallium oxide crystal in the lateral interval, as shown in FIG. 4. After the distance of epitaxy into the first barrier layer 401 reaches L, the continuously grown gallium oxide is converted into a single domain crystal and gradually heals. Figure 5

[0057] The gallium source used for growing the gallium oxide crystal is one of trimethyl gallium, triethyl gallium and gallium chloride. The oxygen source used is one or a mixture of more than one of oxygen, laughing gas and water. The temperature used for growing the gallium oxide crystal is between 500℃ and 800℃.

[0058] After many experiments, it is found that the size of the first barrier layer 401 has a direct relationship with the purification of the rotation domain and the healing of the crystal. Some data with representative significance are extracted and shown in the following table.

[0059] Sample w1 (pm) d1 (pm) w1 + d1 (pm) Patterning conditions Experimental results 1 5 25 30 w1 < d1 ; 50 μm ≥ d1 ≥ 3 μm Monodomain 2 15 15 30 w1 = d1 ; 50 pm > d1 > 3 pm Monodomain 3 1 3 4 w1 < d1 ; d1 = 3 μm Monodomain 4 30 50 80 w1 < d1 ; d1 = 50 μm Monodomain 5 25 5 30 w1 > d1 ; 50 pm > d1 > 3 pm Mixed domain 6 2 2.5 4.5 w1 < d1 ; d1 < 3 μm Mixed domain 7 5 60 65 w1 < d1 ; d1 > 50 μm Not healable 8 65 60 125 w1 > d1 ; d1 > 50 pm Not healable

[0060] ​​​The experimental results of "single domain" in the table indicate that after the gallium oxide crystal is partially blocked by the first blocking layer 401, single domain ε-phase gallium oxide 302 can continue to grow outside the mixed domain ε-phase gallium oxide 301 and can be healed, and after healing, it can be used for subsequent preparation, which is the core test index of the patent. The experimental results of "mixed domain" indicate that even if the gallium oxide crystal can continue to grow and heal after passing through the first blocking layer 401, it only contains mixed domain crystals and does not contain single domain crystals, which is the result to be excluded by the technical solution. The experimental results of "unable to heal" indicate that the gallium oxide crystal that continues to grow after passing through the first blocking layer 401 cannot be healed, and the sample preparation fails.

[0061] After detecting all the successfully prepared samples, it is found that as long as single domain crystals can be grown, the one-sided distance of the mixed domain crystals epitaxially grown on the first blocking layer 401 is generally 1-1.5 μm, which is independent of the thickness and material of the first blocking layer 401 and independent of the growth thickness of the gallium oxide. Therefore, when the width w2 of the second blocking layer 402 is selected in the subsequent process, it only needs to take the maximum value of L, that is, w2 is slightly larger than w1+2*L, so as to completely cover the mixed domain crystals to be shielded, which is convenient for process operation. Corresponding to sample 6 in the above table, since the total width of the mixed domain crystals grown laterally at both ends is close to or equal to 3 μm, the lateral growth width is too small when d1 is not enough, thereby affecting the growth of single domain, and the final result is mixed domain. When d1 is greater than 50 μm, such as samples 7 and 8, the distance is too large, which affects the lateral epitaxial process, so that the sample is difficult to heal. From the above table, it can be seen that as long as the relationship of w1≤d1; 50 μm≥d1≥3 μm is met, single domain ε-phase gallium oxide 302 can be grown from the side of the mixed domain ε-phase gallium oxide 301 and successfully healed.

[0062] S4. A patterned second blocking layer 402 is prepared at the top end of the mixed domain crystal above the window area; the second blocking layer 402 completely covers the part of the mixed domain ε-phase gallium oxide 301 that passes through the first blocking layer 401, as shown in Figure 6 、 Figure 7 、 Figure 8 .

[0063] S5. The gallium oxide crystal is continuously grown to obtain a gallium oxide thin film with single domain on the upper part, as shown in Figure 9 .

[0064] S6. An ε-phase aluminum gallium oxide layer 500 is prepared on the gallium oxide thin film to obtain a target device, as shown in Figure 1 .

[0065] The device prepared in step S6 is subjected to optical microscope testing, and the characterization results of the surface morphology are as shown in Figure 10As shown. The heterojunction surface is smooth and flat, and the roughness is small. It can form a good contact with the metal electrode in the subsequent preparation of the heterojunction device. Through high-resolution X-ray diffraction experiments, it is found that the ε-phase gallium oxide single crystal thin film without rotation domains has high quality, and the in-plane rocking curve broadening is greatly reduced.

[0066] In the present application, the principle of twice lateral epitaxial growth to realize rotation domain filtering is adopted: the ε-phase gallium oxide belongs to an orthogonal structure, and due to the mismatch of its rotation symmetry and the substrate, the ε-phase gallium oxide is prone to appear triple rotation domains. The first barrier layer 401 is patterned as a first mask to accurately select the preset area for growing the gallium oxide crystal for the first time, so that the ε-phase gallium oxide is epitaxially grown under the influence of rotation domains. The mixed rotation domains only appear in a controllable range slightly larger than the window area of the first barrier layer 401, and the remaining part is the a-type domain area. Based on the healing after the first lateral epitaxial growth, the positions of the ε-phase gallium oxide mixed domain area and the a-type domain area are determined according to the patterned structure. The second barrier layer 402 is patterned as a second mask to effectively filter the ε-phase gallium oxide rotation domains, and the window area of the second mask only leaves the growth surface of a single crystal domain, and then the second lateral epitaxial growth is carried out. Based on the single crystal domain area and the double masks, epitaxial growth is carried out, so as to obtain a ε-phase gallium oxide single crystal thin film without rotation domains on a silicon substrate. The aluminum gallium oxide prepared on the high-quality ε-phase gallium oxide single crystal thin film without rotation domains on a silicon substrate can obtain the heterojunction with the quality described in the present application.

[0067] The difference between the comparative example and the embodiment is that the ε-phase gallium oxide is directly grown on the substrate without rotation domain filtering, and then the aluminum gallium oxide is continuously prepared to form another heterojunction sample. The sample plate of the comparative example is scanned by an optical microscope with the same size, and the result is shown in Figure 11 It can be seen that the surface of the sample is rough and cannot be healed, which leads to the formation of a continuous smooth film. This is because in the case of mixed domains, the epitaxial matching relationship of the ε-phase aluminum gallium oxide is affected, and high-quality single crystal ε-phase aluminum gallium oxide cannot be formed. Finally, it leads to the failure to prepare a high-quality heterojunction of ε-phase aluminum gallium oxide / ε-phase gallium oxide.

[0068] For those skilled in the art, other various corresponding changes and modifications can be made according to the above-described technical solutions and concepts, and all of these changes and modifications should belong to the protection scope of the claims of the present application.

Claims

1. A gallium oxide-based heterojunction, characterized in that, A mixed-domain ε-phase gallium oxide (301) is grown on a substrate (100); a patterned first barrier layer (401) is disposed on the surface of the mixed-domain ε-phase gallium oxide (301); the first barrier layer (401) has a window region, and the mixed-domain ε-phase gallium oxide (301) extends upward through the first barrier layer (401) in the window region; a second barrier layer (402) is disposed at the top of the portion of the mixed-domain ε-phase gallium oxide (301) that extends through the first barrier layer (401); the second barrier layer (402)... 2) Completely cover the portion of the mixed-domain ε-phase gallium oxide (301) that extends through the first barrier layer (401); single-domain ε-phase gallium oxide (302) is grown on the outer side of the portion of the mixed-domain ε-phase gallium oxide (301) that extends through the first barrier layer (401), above the first barrier layer (401), and above the second barrier layer (402); an ε-phase aluminum gallium oxide layer (500) is deposited on the upper surface of the single-domain ε-phase gallium oxide (302); the ε-phase aluminum gallium oxide layer (500) and the single-domain ε-phase gallium oxide (302) form a heterojunction; The width of the first barrier layer (401) is d1, and the width of the open window is w1; The width of the second barrier layer (402) is w2, and the interval between adjacent second barrier layers (402) is d2; The distance from the side of the mixed-domain ε-phase gallium oxide (301) to the first barrier layer (401) is L; Each dimension satisfies the following relationship: w1+d1=w2+d2; w2>w1+2*L; w1≤d1; 50μm≥d1≥3μm.

2. The gallium oxide-based heterojunction according to claim 1, characterized in that, The substrate (100) is one of sapphire, silicon carbide, gallium nitride, and aluminum nitride.

3. The gallium oxide-based heterojunction according to claim 2, characterized in that, The first barrier layer (401) is parallel to the sapphire <112 _ 0> crystal orientation, or sapphire <101 _ 0> crystal orientation, or silicon carbide <112 _ 0> crystal orientation, or silicon carbide <101 _ 0> crystal orientation, or gallium nitride <112 _ 0> crystal orientation, gallium nitride <101 _ 0> crystal orientation, or aluminum nitride <112 _ 0> crystal orientation, or aluminum nitride <101 _ 0> Crystal orientation.

4. The gallium oxide-based heterojunction according to claim 1, characterized in that, The first barrier layer (401) and / or the second barrier layer (402) are silicon dioxide, metal, or silicon nitride.

5. The gallium oxide-based heterojunction according to claim 1, characterized in that, The thickness of the second barrier layer (402) is greater than 10 nm.

6. A growth method for preparing a gallium oxide-based heterojunction as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Gallium oxide crystal is grown on substrate (100); S2. A patterned first barrier layer (401) is laid on a gallium oxide crystal, wherein the first barrier layer (401) exposes predetermined portions of the gallium oxide crystal at intervals using window areas; S3. Gallium oxide crystals are further grown on the exposed gallium oxide crystal area using lateral epitaxy, and the grown gallium oxide crystals are healed in the lateral region; the gallium oxide crystals above the window area and the gallium oxide crystals between the first barrier layer (401) and the substrate (100) are all mixed-domain crystals, and the mixed-domain crystals above the window area extend laterally a distance L towards the upper end face of the first barrier layer (401); the gallium oxide crystals between adjacent mixed-domain crystals above the window area are single-domain crystals; S4. A patterned second barrier layer (402) is prepared at the top of the mixed-domain crystal above the window region; the second barrier layer (402) completely covers the portion of the mixed-domain ε-phase gallium oxide (301) that extends out of the first barrier layer (401); S5. Continue growing gallium oxide crystal to obtain a gallium oxide thin film with single domains on the top; S6. An ε-phase aluminum gallium oxide layer (500) is prepared on the gallium oxide thin film to obtain the target device.

7. The growth method according to claim 6, characterized in that, The gallium source used for gallium oxide crystal growth is one of trimethylgallium, triethylgallium, and gallium chloride; the oxygen source used is one or more of oxygen, nitrous oxide, and water.

8. The growth method according to claim 6, characterized in that, The temperature used for growing the gallium oxide crystal is between 500℃ and 800℃.

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