JP2012243792A - GaN THIN FILM BONDED SUBSTRATE AND METHOD OF MANUFACTURING THE SAME, AND GaN-BASED HIGH ELECTRON MOBILITY TRANSISTOR AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance HEMT in which a buffer leakage current and a gate leakage current are suppressed.SOLUTION: A method of manufacturing a GaN thin film bonded substrate includes steps of: implanting hydrogen ions with an average implantation dosage of 1×10cmor more and 3×10cmor less to a plane 10i at a depth 0.1 μm or more and 100 μm or less from a main surface of a GaN bulk crystal 10; bonding a different composition substrate 20 having a chemical composition different from GaN onto the main surface of the GaN bulk crystal 10 to which hydrogen ions are implanted; and forming a structure with a GaN thin film 10a bonded on the different composition substrate 20, the GaN thin film 10a being obtained by separating the GaN bulk crystal 10 at the plane 10i positioned at the hydrogen ion implanted depth by heat treating the GaN bulk crystal 10. A method of manufacturing a GaN-based HEMT includes a step of growing at least one GaN-based semiconductor layer 30 onto the GaN thin film 10a of the GaN thin film bonded substrate 1.

Description

  The present invention relates to a GaN thin film bonded substrate suitable for a GaN high electron mobility transistor and a method for manufacturing the same, and a GaN high electron mobility transistor including the GaN thin film bonded substrate and a method for manufacturing the same.

A GaN-based high electron mobility transistor (hereinafter also referred to as a GaN-based HEMT) uses a SiC substrate or the like to form a GaN layer, an In _x Ga _1-x N layer (0 <x <1), an Al _x Ga ₁₋ the GaN-based semiconductor layer such as the channel layer _x N layer (0 <x <1), was used Al _y Ga _1-y N layer (0 <x <y <1 ) GaN -based semiconductor layer such as the barrier layer HEMT (High Electron Mobility Transistor). Such a GaN-based HEMT is excellent in electron concentration, thermal conductivity, electron mobility, and the like. For example, a high-concentration two-dimensional electron gas is generated by a piezo electric field generated at the interface between the Al _y Ga _1-y N layer and the GaN layer. This is advantageous for reducing the resistance. Further, since a high breakdown voltage can be obtained by using a GaN-based semiconductor layer having a large band gap, it has attracted attention as a power device or the like.

For example, a scientific technique, ED 25005-134 (2005) (Non-Patent Document 1), uses a GaN layer and an Al _x Ga _1-x N layer (0 < A GaN-based HEMT having a heterostructure of x <1) is disclosed.

  In addition, Journal of Applied Electronic Physical Properties, Vol. 12, No. 1 (Non-Patent Document 2) discloses a GaN-based HEMT using a self-standing GaN substrate having a low dislocation density.

  Japanese Patent Laying-Open No. 2010-177281 (Patent Document 1) discloses increasing the resistance of the surface by forming an ion implantation layer on the surface of the conductive free-standing GaN.

JP 2010-177281 A

IEICE Technical, ED 25005-134 (2005) Journal of Applied Electronics Properties Subcommittee, Vol. 12, No. 1

  However, a GaN-based HEMT using a different composition substrate such as a SiC substrate as disclosed in Shingaku Technique, ED 25005-134 (2005) (Non-Patent Document 1), includes a GaN layer and an AlGaN formed on the SiC substrate. Due to the difference in lattice constant and thermal expansion coefficient between the SiC substrate and the SiC substrate, threading dislocations are introduced to increase the dislocation density, and defects such as pits, depressions and cracks occur on the surface, resulting in gate leakage current. There is a problem of doing.

  In addition, a GaN-based HEMT using a self-standing GaN substrate having a low dislocation density as disclosed in Journal of Applied Electronics Physical Properties Subcommittee, Vol. 12, No. 1 (Non-patent Document 2) is manufactured by a self-standing GaN substrate. In general, the HEMT (high electron mobility transistor) formed has n-type conductivity, and a leak (buffer leak) current flows through the free-standing GaN substrate. is there.

  Further, as disclosed in Japanese Patent Application Laid-Open No. 2010-177281 (Patent Document 1), even when a high-resistance layer is interposed between a self-standing GaN substrate and an active GaN-based semiconductor layer, it is conductive during high-frequency operation. There is a problem that a gain cannot be obtained due to the electric capacity between the self-supporting GaN substrate and the gate electrode.

  An object of the present invention is to solve the above problems and provide a high-performance HEMT in which buffer leak current and gate leak current are suppressed.

The present invention is a method for manufacturing a GaN thin film bonded substrate, wherein an average implantation amount of hydrogen ions is 1 × 10 ¹⁴ cm ⁻² into a surface having a depth of 0.1 μm or more and 100 μm or less from the main surface of a GaN bulk crystal. The step of implanting at 3 × 10 ¹⁷ cm ⁻² or less, the step of bonding a different composition substrate having a chemical composition different from that of GaN to the main surface of the GaN bulk crystal into which hydrogen ions are implanted, and the heat treatment of the GaN bulk crystal A step of separating the GaN bulk crystal on the surface having the depth into which the hydrogen ions have been implanted, and forming a GaN thin film bonded on the different composition substrate. It is.

  The present invention is also a method for manufacturing a GaN-based high electron mobility transistor, wherein at least one GaN layer is formed on the GaN thin film of the GaN thin film bonded substrate manufactured by the above-described GaN thin film bonded substrate manufacturing method. A method for manufacturing a GaN-based high electron mobility transistor including a step of growing a semiconductor layer.

The present invention also includes a different composition substrate having a chemical composition different from that of GaN, and a GaN thin film bonded to the different composition substrate, the GaN thin film having a thickness of 0.1 μm to 100 μm, A GaN thin film bonded substrate having a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less.

In the GaN thin film bonded substrate according to the present invention, the dislocation density of the GaN thin film can be 1 × 10 ⁹ cm ⁻² or less. Further, the carrier concentration of the GaN thin film can be set to 1 × 10 ¹⁵ cm ⁻³ or less. Further, the sheet resistance of the GaN thin film can be set to 1 × 10 ⁴ Ω / □ or more.

The present invention also includes a different composition substrate having a chemical composition different from that of GaN, a GaN thin film bonded to the different composition substrate, and at least one GaN-based semiconductor layer formed on the GaN thin film, The thin film is a GaN-based high electron mobility transistor having a thickness of 0.1 μm to 100 μm and a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ^{−2 to} 3 × 10 ¹⁷ cm ⁻² .

In the GaN-based high electron mobility transistor according to the present invention, the dislocation density of the GaN thin film can be 1 × 10 ⁹ cm ⁻² or less. Further, the carrier concentration of the GaN thin film can be set to 1 × 10 ¹⁵ cm ⁻³ or less. Further, the sheet resistance of the GaN thin film can be set to 1 × 10 ⁴ Ω / □ or more.

  According to the present invention, it is possible to provide a high-performance HEMT in which buffer leakage current and gate leakage current are suppressed.

It is a schematic sectional drawing which shows an example of the manufacturing method of the GaN thin film bonded substrate and GaN-type high electron mobility transistor concerning this invention. It is a schematic sectional drawing which shows an example of the GaN thin film bonded substrate concerning this invention. It is a schematic sectional drawing which shows an example of the GaN-type high electron mobility transistor concerning this invention. 4 is a graph showing the relationship between the average implantation amount of hydrogen ions and the sheet resistance of a GaN thin film in the production of a GaN thin film bonded substrate and a GaN-based high electron mobility transistor according to the present invention.

[Embodiment 1]
Referring to FIG. 1, in the method for manufacturing a GaN thin film bonded substrate according to an embodiment of the present invention, a hydrogen ion is applied to a surface 10 i having a depth D of 0.1 μm or more and 100 μm or less from a main surface of a GaN bulk crystal 10. A step of implanting I with an average implantation amount of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less (FIG. 1A), and the main surface of the GaN bulk crystal 10 into which hydrogen ions are implanted. The step of bonding the different composition substrate 20 having a chemical composition different from that of GaN (FIG. 1B) and the heat treatment of the GaN bulk crystal 10 to which the different composition substrate 20 is bonded are subjected to heat treatment to thereby apply the GaN bulk crystal. 10 is separated on the surface 10i having the above-mentioned depth embrittled by implantation of hydrogen ions, and a GaN thin film 10a bonded to the different composition substrate 20 is formed (FIG. 1C).

The GaN thin film bonded substrate manufacturing method of the present embodiment includes a different composition substrate 20 having a chemical composition different from that of GaN, and a GaN thin film 10a bonded to the different composition substrate 20, and the GaN thin film 10a has a thickness thereof. The GaN thin film bonded substrate 1 having a thickness T _D of 0.1 μm or more and 100 μm or less and a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less can be obtained efficiently. Such a GaN thin film bonded substrate 1 is suitably used for manufacturing a high-performance GaN-based HEMT 2 in which buffer leak current and gate leak current are suppressed.

(Hydrogen ion implantation process)
First, referring to FIG. 1A, in the method of manufacturing a GaN thin film bonded substrate according to this embodiment, hydrogen is applied to a surface 10i having a depth D of 0.1 μm or more and 100 μm or less from the main surface of the GaN bulk crystal 10. A step of implanting ions I at an average implantation amount of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less (hydrogen ion implantation step).

Here, the GaN bulk crystal 10 is not particularly limited, but from the viewpoint of obtaining a highly crystalline GaN thin film, the dislocation density is preferably 1 × 10 ⁹ cm ⁻² or less, and more preferably 1 × 10 ⁷ cm ⁻² or less. preferable. The method for producing the GaN bulk crystal 10 is not particularly limited. From the viewpoint of obtaining a highly crystalline GaN bulk crystal, the HVPE (hydride vapor phase epitaxy) method, the MOCVD (metal organic chemical vapor deposition) method, the MBE (molecular) Line growth) method, gas phase method such as sublimation method, flux method. A liquid phase method such as a high nitrogen pressure solution method is preferred.

  The depth D for implanting hydrogen ions is to avoid disappearance of the GaN thin film due to thermal decomposition at the ambient temperature when the GaN-based semiconductor layer is epitaxially grown on the GaN thin film of the bonded substrate to be manufactured. From the viewpoint of thinning the conductive GaN thin film, a thickness of 0.1 μm or more and 100 μm or less from the main surface of the GaN bulk crystal 10 is preferable.

The average implantation amount of hydrogen ions (average dose) reduces the buffer leakage current after the HEMT formation by sufficiently increasing the sheet resistance of the GaN thin film, and suppresses defects such as dislocations in the GaN thin film and after the HEMT formation. 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less is preferable from the viewpoint of reducing the gate leakage current.

(Bonding process of different composition substrates)
Next, referring to FIG. 1B, in the method for manufacturing a GaN thin film bonded substrate according to this embodiment, the main surface of the GaN bulk crystal 10 into which hydrogen ions are implanted has a different chemical composition from that of GaN. A step of bonding the composition substrate 20 (a step of bonding different composition substrates) is included.

The heterogeneous substrate 20 is not particularly limited, but from a viewpoint suitable for manufacturing a HEMT, a sapphire substrate, a Si substrate, a MgO substrate, a ZnO substrate, a ZnS substrate, a ZnSe substrate, a quartz substrate, a carbon substrate, a diamond substrate, such as Ga ₂ O ₃ substrate is preferably exemplified.

  The bonding method of the different composition substrate 20 is not particularly limited, but from the viewpoint of uniformly bonding at a relatively low temperature, a surface activation method, a fusion bonding method, or the like is preferable. Here, the surface activation method refers to a method in which the surfaces to be bonded are activated by exposing the surfaces to be exposed to plasma, and the bonding method is a method in which the cleaned surfaces (bonding surfaces) are heated under pressure. And the method of pasting together.

(Process for forming GaN thin film)
Next, referring to FIG. 1C, in the manufacturing method of the GaN thin film bonded substrate according to the present embodiment, the GaN bulk crystal 10 is heat-treated so that hydrogen ions are implanted into the GaN bulk crystal 10 and become embrittled. The step of forming the GaN thin film 10a bonded to the different composition substrate 20 by separating by applying thermal stress on the surface 10i having the above depth (GaN thin film forming step) is included.

  By heat-treating the GaN bulk crystal 10, the GaN bulk crystal 10 is embrittled with the surface 10 i having the above depth into which hydrogen ions have been implanted, and the GaN bulk crystal 10 is bonded to the different composition substrate 20 on the surface. 10a and the remaining GaN bulk crystal 10b. Further, since the heat treatment is passivated by hydrogen ions implanted with donor impurities in the GaN thin film 10a, the GaN thin film 10a has a high resistance. Note that the hydrogen atoms present in the GaN thin film after the heat treatment (the hydrogen atoms that have been implanted to become hydrogen atoms by passivating the donor impurities) grow on the GaN thin film because the diffusion coefficient is very low. It hardly diffuses into the GaN-based semiconductor layer.

  The heat treatment condition of the GaN bulk crystal is that the GaN bulk crystal 10 can be separated into the GaN thin film 10a and the remaining GaN bulk crystal 10b and is passivated by hydrogen ions implanted with donor impurities in the GaN thin film 10a. Any condition may be used.

The GaN thin film bonded substrate 1 can be efficiently obtained by the above method for manufacturing a GaN thin film bonded substrate. The thickness T _D of this manner GaN film obtained bonded GaN thin film 10a of the substrate 1, to become substantially equal to the depth D of the hydrogen ions implanted into GaN bulk crystalline body 10, 100 [mu] m or more 0.1μm It becomes as follows. Here, the thickness T _D of the GaN thin film, a step meter, can be measured by SEM (Scanning Electron Microscope) image. In addition, the hydrogen sheet concentration of the GaN thin film 10a (referred to as the hydrogen concentration per unit area on the main surface of the GaN thin film; hereinafter the same) is substantially the same as the average implantation amount of hydrogen ions implanted into the GaN bulk crystal 10. 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less. Here, the hydrogen sheet concentration of the GaN thin film can be measured by SIMS (secondary ion mass spectrometry) or the like.

[Embodiment 2]
Referring to FIG. 2, a GaN thin film bonded substrate 1 according to another embodiment of the present invention includes a different composition substrate 20 having a chemical composition different from that of GaN, a GaN thin film 10a bonded to the different composition substrate 20, The GaN thin film 10a has a thickness T _D of 0.1 μm or more and 100 μm or less, and a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less.

Substrate 1 thin GaN film-joined in this embodiment, the thickness T _D of the thin film of GaN 10a is at 0.1μm or 100μm or less, the hydrogen sheet density of GaN film 10a is 1 × 10 ¹⁴ cm ^-2 or more 3 × 10 ¹⁷ Since it is cm ⁻² or less, the resistance of the GaN thin film 10a is high, which is suitable for manufacturing the GaN-based HEMT2.

In the GaN thin film bonded substrate 1 of this embodiment, the dislocation density of the GaN thin film 10a is preferably 1 × 10 ⁹ cm ⁻² or less from the viewpoint of reducing gate leakage current after HEMT formation. More preferably, it is ⁷ cm ⁻² or less. Here, the dislocation density of the GaN thin film 10a can be measured by observing etch pits after chemical treatment. The carrier concentration of the GaN thin film is 1 × 10 ¹⁵ cm ⁻³ from the viewpoint of reducing drain (buffer) leakage current after HEMT formation and increasing high-frequency operating gain (that is, increasing current gain cutoff frequency). The following is preferable. Here, the carrier concentration of the GaN thin film 10a can be measured by hole measurement, non-contact eddy current measurement, or the like. Further, the sheet resistance of the GaN thin film is 1 × 10 ⁴ Ω / □ from the viewpoint of reducing drain (buffer) leakage current after HEMT formation and increasing high-frequency operating gain (that is, increasing current gain cutoff frequency). The above is preferable. Here, the sheet resistance of the GaN thin film 10a can be measured by hole measurement, non-contact eddy current measurement, or the like.

[Embodiment 3]
Referring to FIG. 1 (particularly, FIG. 1D), a method for manufacturing a GaN-based HEMT (GaN-based high electron mobility transistor) according to still another embodiment of the present invention is the GaN thin film according to the first embodiment. A step of growing at least one GaN-based semiconductor layer 30 (GaN-based semiconductor layer growth step) on the GaN thin film 10a of the GaN thin-film bonded substrate 1 of Embodiment 2 manufactured by the method for manufacturing a bonded substrate. Including.

  The method for growing the GaN-based semiconductor layer 30 is not particularly limited, but from the viewpoint of epitaxially growing the highly crystalline GaN-based semiconductor layer 30 on the GaN thin film 10a, the MOCVD method, the HVPE method, the MBE method, the sublimation method, etc. Preferable examples include a liquid phase method such as a gas phase method, a flux method, and a high nitrogen pressure solution method.

The GaN-based semiconductor layer 30 is not particularly limited as long as it exhibits the function of the GaN-based HEMT. For example, the i-type GaN layer 32 and the i-type Al _0.25 Ga _0.75 N layer 34 can be used. Here, the i-type GaN layer 32 functions as an electron transit layer, and the i-type Al _0.25 Ga _0.75 N layer 34 functions as an electron supply layer.

  Further, referring to FIG. 1E, in the method of manufacturing the GaN-based high electron mobility transistor of this embodiment, the source electrode 42, the drain electrode 44, and the gate electrode 46 are formed on the GaN-based semiconductor layer 30. A process (electrode formation process) can be included.

  The method for forming the source electrode 42, the drain electrode 44, and the gate electrode 46 is not particularly limited as long as it is suitable for forming these electrodes, and a photolithographic method, a lift-off method, and the like are preferable.

  Further, these electrodes are not particularly limited as long as they exhibit the functions of these electrodes, and as the source electrode 42 and the drain electrode 44, an Al layer / Ti layer / Au layer alloyed, etc. A preferable example of the gate electrode 46 is an Au layer.

The GaN-based HEMT 2 can be efficiently obtained by the above-described GaN-based HEMT manufacturing method. The thickness T _D of the thin film of GaN 10a of the thus obtained GaN-based HEMT2 is the same as the thickness T _D of the GaN thin film of GaN-based thin-film-joined substrate, and 0.1μm or 100μm or less. Further, the hydrogen sheet concentration of the GaN thin film 10a of the GaN-based HEMT ² is the same as the hydrogen sheet concentration of the GaN thin film 10a of the GaN-based thin film bonded substrate 1, and is 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ^−2. It becomes as follows.

[Embodiment 4]
Referring to FIG. 3, a GaN-based HEMT 2 which is still another embodiment of the present invention includes a different composition substrate 20 having a chemical composition different from that of GaN, a GaN thin film 10a bonded to the different composition substrate 20, and a GaN thin film. And the GaN thin film 10a has a thickness of 0.1 μm or more and 100 μm or less, and a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ^−2. This is 3 × 10 ¹⁷ cm ⁻² or less.

GaN system of this embodiment HEMT2, the thickness T _D of the thin film of GaN 10a is at 0.1μm or 100μm or less, the hydrogen sheet density of GaN film 10a is 1 × 10 ¹⁴ cm ^-2 or more 3 × 10 ¹⁷ cm ^-2 Since the resistance of the GaN thin film 10a is high, buffer leak and gate leak are suppressed and high performance is exhibited.

GaN-based HEMT2 of this embodiment, for example, the GaN and chemical composition is different from different composition substrate 20, the thickness T _D is 0.1μm or more 100μm or less and the hydrogen sheet concentration of 1 × 10 ¹⁴ cm ^-2 or more 3 × A GaN thin film 10a of 10 ¹⁷ cm ⁻² or less is disposed, and an i-type GaN layer 32 (electron transit layer) and an i-type Al _0.25 Ga _0.75 N layer are formed on the GaN thin film 10a as at least one GaN-based semiconductor layer 30. 34 (electron supply layer) are sequentially arranged, and a source electrode 42, a drain electrode 44, and a gate electrode 46 are arranged on the i-type Al _0.25 Ga _0.75 N layer 34, respectively.

In the GaN-based HEMT2 of the present embodiment, the dislocation density of the GaN thin film 10a is preferably 1 × 10 ⁹ cm ⁻² or less from the viewpoint of reducing the gate leakage current of the HEMT, and is 1 × 10 ⁷ cm ⁻² or less. It is more preferable that The carrier concentration of the GaN thin film is 1 × 10 ¹⁵ cm ⁻³ or less from the viewpoint of reducing the drain (buffer) leakage current of the HEMT and increasing the high-frequency operating gain (that is, increasing the current gain cutoff frequency). Preferably there is. Further, the sheet resistance of the GaN thin film is 1 × 10 ⁴ Ω / □ or more from the viewpoint of reducing HEMT drain (buffer) leakage current and increasing the high-frequency operating gain (that is, increasing the current gain cutoff frequency). Preferably there is. Here, the dislocation density, carrier concentration, and sheet resistance of the GaN thin film 10a in the HEMT can be measured by the above-described measurement method for the GaN thin film 10a after the HEMT is decomposed to expose the GaN thin film 10a.

Example 1
1. Hydrogen ion implantation After growth by HVPE, a GaN bulk crystal 10 having a diameter of 2 inches (5.08 cm) and a thickness of 10 mm was prepared by grinding and polishing the main surface into a mirror surface. For this GaN bulk crystal 10, the dislocation density was 1 × 10 ⁶ cm ⁻² as measured by etch pit observation after chemical treatment, the carrier concentration was 5 × 10 ¹⁴ cm ⁻³ as measured by hole measurement, and the sheet resistance was hole. It was 5 × 10 ⁴ Ω / □ when measured by measurement.

Referring to FIG. 1A, an average implantation amount (average dose) of hydrogen ions is introduced from the N atom main surface side of GaN bulk crystal 10 to a surface having a depth D of 0.3 μm from the N atom main surface. The amount was injected at 1 × 10 ¹⁴ cm ⁻² .

2. Bonding of Different Composition Substrates As the different composition substrate 20, a sapphire substrate having a diameter of 2 inches (5.08 cm) and a thickness of 400 μm was prepared.

  Referring to FIG. 1B, the main surface of the N atom of the GaN bulk crystal 10 implanted with hydrogen ions was etched with chlorine gas to obtain a clean surface. The main surface of the sapphire substrate (different composition substrate 20) was etched with argon gas to obtain a clean surface.

  The cleaned N atom main surface of the GaN bulk crystal 10 implanted with hydrogen ions and the cleaned main surface of the sapphire substrate (different composition substrate 20) were bonded together by a surface activation method.

3. Formation of GaN Thin Film Referring to FIG. 1 (C), GaN bulk crystal 10 bonded to a sapphire substrate (different composition substrate 20) is heat-treated at 60 ° C. in a nitrogen atmosphere, so that GaN bulk crystal 10 is hydrogenated. The GaN thin film 10a is formed on the sapphire substrate (different composition substrate 20) by forming the GaN thin film 10a bonded on the sapphire substrate (different composition substrate 20) by separating on the surface where the ions are implanted. A bonded GaN thin film bonded substrate 1 was obtained.

The obtained thin GaN film-joined substrate 1, the thickness T _D of the GaN thin film was 0.3μm was measured by cross-sectional SEM image observation, 5 × 10 ¹⁵ cm where hydrogen sheet density of GaN films was measured by SIMS is ^-2, GaN dislocation density of the thin film was measured by etch pit observation after chemical treatments 1 × 10 ⁶ cm ^-2, the carrier concentration of the GaN thin film is 5 × 10 ¹⁴ cm ^-3 was measured by hole measurement, The sheet resistance of the GaN thin film was 1 × 10 ⁵ Ω / □ as measured by Hall measurement. Thus, the thickness T _D of the thin GaN film-joined GaN thin film 10a of the substrate 1 was approximately equal to the depth D of the hydrogen ions implanted into GaN bulk crystalline body 10. Further, the hydrogen sheet concentration of the GaN thin film 10a was almost the same as the average amount of hydrogen ions implanted into the GaN bulk crystal 10.

4). Fabrication of GaN-based high electron mobility transistor Referring to FIG. 1D, an i-type GaN layer having a thickness of 3 μm is formed as GaN-based semiconductor layer 30 on GaN thin film 10a of GaN thin film bonded substrate 1 by MOCVD. The i-type Al _0.25 Ga _0.75 N layer 34 having a thickness of 32 and a thickness of 20 nm was sequentially grown.

Referring to FIG. 1E, a source electrode 42, a drain electrode 44, and a gate electrode 46 were formed on the i-type Al _0.25 Ga _0.75 N layer 34 by using a photolithography method and a lift-off method. Here, the source electrode 42 and the drain electrode 44 are both alloyed by laminating a Ti layer having a thickness of 50 nm, an Al layer having a thickness of 100 nm, and an Au layer having a thickness of 200 nm, and performing heat treatment at 800 ° C. for 30 seconds. Was formed. The gate electrode 46 was formed of an Au layer having a thickness of 300 μm so that the gate width was 2 μm and the gate length was 150 μm.

(Example 2)
A GaN thin film bonded substrate 1 was obtained in the same manner as in Example 1 except that hydrogen ions were implanted into the GaN bulk crystal 10 at an average implantation amount (average dose amount) of 1 × 10 ¹⁵ cm ⁻² . The obtained GaN thin film bonded substrate 1 has a GaN thin film thickness T _D of 0.3 μm, a GaN thin film hydrogen sheet concentration of 5 × 10 ¹⁵ cm ⁻² , and a GaN thin film dislocation density of 1 ×. 10 ⁶ is cm ^-2, the carrier concentration of the GaN thin film is of 5 × 10 ¹⁴ cm ^-3, the sheet resistance of the GaN thin film is 5 × 10 was ^{4 Ω} / □.

(Example 3)
A GaN thin film bonded substrate 1 was obtained in the same manner as in Example 1 except that hydrogen ions were implanted into the GaN bulk crystal 10 at an average implantation amount (average dose amount) of 1 × 10 ¹⁷ cm ⁻² . The obtained GaN thin film bonded substrate 1 has a GaN thin film thickness T _D of 0.3 μm, a GaN thin film hydrogen sheet concentration of 1 × 10 ¹⁷ cm ⁻² , and a GaN thin film dislocation density of 1 ×. It was 10 ⁷ cm ⁻² , the carrier concentration of the GaN thin film was 5 × 10 ¹⁴ cm ⁻³ or less, and the sheet resistance of the GaN thin film was 2 × 10 ⁶ Ω / □.

(Comparative Example 1)
A GaN thin film bonded substrate 1 was obtained in the same manner as in Example 1 except that hydrogen ions were implanted into the GaN bulk crystal 10 at an average implantation amount (average dose amount) of 1 × 10 ¹³ cm ⁻² . The obtained GaN thin film bonded substrate 1 has a GaN thin film thickness T _D of 0.3 μm, a GaN thin film hydrogen sheet concentration of 1 × 10 ¹³ cm ⁻² , and a GaN thin film dislocation density of 1 ×. a 10 ⁶ cm ^-2, the carrier concentration of the GaN thin film is the 5 × 10 ¹⁶ cm ^-3, the sheet resistance of the GaN thin film was 1 × 10 ² Ω / □ is.

FIG. 4 shows the relationship between the average amount of hydrogen ions implanted into the GaN bulk crystal and the sheet resistance of the GaN thin film for Examples 1 to 3 and Comparative Example 1. As shown in FIG. 4, by setting the average implantation amount of hydrogen ions implanted into the GaN bulk crystal to 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less, the sheet resistance of the GaN thin film becomes 1 × 10 6. A GaN thin film bonded substrate of ⁴ Ω / □ or more and a GaN-based HEMT were obtained, and it was found that the GaN-based HEMT had high performance.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 GaN thin film bonded substrate, 2 GaN-based HEMT, 10,10b GaN bulk crystal, 10a GaN thin film, 10i plane, 20 different composition substrate, 30 GaN-based semiconductor layer, 32 i-type GaN layer, 34 i-type Al _0.25 Ga _0.75 N layer, 42 source electrode, 44 drain electrode, 46 gate electrode.

Claims (10)

A method of manufacturing a GaN thin film bonded substrate,
A step of implanting hydrogen ions at a depth of 0.1 μm or more and 100 μm or less from the main surface of the GaN bulk crystal at an average implantation amount of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less;
A step of bonding a different composition substrate having a chemical composition different from that of GaN to the main surface of the GaN bulk crystal implanted with the hydrogen ions;
Separating the GaN bulk crystal at the depth surface into which the hydrogen ions have been implanted by heat-treating the GaN bulk crystal, and forming a GaN thin film bonded onto the different composition substrate. A method for manufacturing a GaN thin film bonded substrate. A method for manufacturing a GaN-based high electron mobility transistor,
A GaN-based high electron mobility transistor comprising a step of growing at least one GaN-based semiconductor layer on the GaN thin film of the GaN thin-film bonded substrate manufactured by the method for manufacturing a GaN thin-film bonded substrate according to claim 1. Manufacturing method. A different composition substrate having a chemical composition different from that of GaN, and a GaN thin film bonded on the different composition substrate,
The GaN thin film bonded substrate, wherein the GaN thin film has a thickness of 0.1 μm to 100 μm and a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ^{−2 to} 3 × 10 ¹⁷ cm ⁻² . The GaN thin film bonded substrate according to claim 3, wherein the dislocation density of the GaN thin film is 1 x 10 ⁹ cm ^-2 or less. 5. The GaN thin film bonded substrate according to claim 3, wherein a carrier concentration of the GaN thin film is 1 × 10 ¹⁵ cm ⁻³ or less. The GaN thin film bonded substrate according to claim 3, wherein the sheet resistance of the GaN thin film is 1 × 10 ⁴ Ω / □ or more. A different composition substrate having a chemical composition different from that of GaN, a GaN thin film bonded onto the different composition substrate, and at least one GaN-based semiconductor layer formed on the GaN thin film,
The GaN thin film has a thickness of 0.1 μm or more and 100 μm or less and a hydrogen sheet concentration of 1 × 10 ¹⁴ cm ⁻² or more and 3 × 10 ¹⁷ cm ⁻² or less. The GaN-based high electron mobility transistor according to claim 7, wherein the dislocation density of the GaN thin film is 1 × 10 ⁹ cm ⁻² or less. 9. The GaN-based high electron mobility transistor according to claim 7, wherein a carrier concentration of the GaN thin film is 1 × 10 ¹⁵ cm ⁻³ or less. The GaN-based high electron mobility transistor according to claim 7, wherein the GaN thin film has a sheet resistance of 1 × 10 ⁴ Ω / □ or more.

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