JP7288656B2 - GaN structure and manufacturing method thereof - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act "2018 The 65th Spring Meeting of the Japan Society of Applied Physics, Lecture Proceedings" (DVD), 12-138, The Japan Society of Applied Physics [Publications] "2019 No. 66 The Japan Society of Applied Physics Spring Meeting Proceedings" (DVD), 11-204, The Japan Society of Applied Physics

The present invention relates to a GaN structure using recoil implantation technology and a method for manufacturing the same.

GaN (gallium nitride) has characteristics such as higher thermal conductivity, higher electron saturation velocity, and higher dielectric breakdown voltage than Si (silicon). Expected to be used.
However, a technique for patterning a p-type GaN region having p-type conductivity in a GaN base material has not been established, which is a major obstacle to the practical use of GaN devices.

2. Description of the Related Art As a method for fabricating Si devices, an ion implantation method for implanting impurity ions into Si is widely practiced for pattern formation of p-type and n-type regions.
When forming the p-type GaN region into the GaN base material by this ion implantation method, it is conceivable to ion-implant Mg (magnesium) as a p-type impurity.
However, when Mg ions are implanted into the GaN base material, the crystals in the GaN base material are severely collapsed, and structural damage is caused to the GaN base material that cannot be recovered even by the subsequent annealing treatment. In addition, when the ion irradiation energy is high, Ga agglomerates in the GaN base material. Therefore, there is a problem that the ion implantation method similar to that for the Si device cannot be applied to the fabrication of the GaN device (see Non-Patent Document 1).

In order to solve these problems, a method has been proposed in which hydrogen ions are implanted together with Mg ions to form the p-type GaN region in the GaN base material (see Non-Patent Document 2).
However, hydrogen ions interfere with the activation of the Mg in the p-type GaN region and adversely affect the properties of the GaN device.
Further, in the above proposal, the Ga surface in the p-type GaN region to be formed is roughened, making it difficult to epitaxially grow a further GaN layer on the Ga surface. There is a problem that the GaN device cannot be produced.

By the way, as an ion implantation technique different from the above ion implantation method, a recoil material is ion-irradiated to the layer of the material to be recoiled in a state in which a layer of the material to be recoiled for imparting conductivity is arranged on the Si base material. An implantation method is known (see Non-Patent Document 3).
In this method, the material to be recoiled is recoiled (flicked out) by the material to be recoiled by irradiating the layer of the material to be recoiled with ions, and the ions are implanted into the Si base material.
However, this recoil implantation method lacks superiority over the ion implantation method, and is hardly used at present.
Moreover, there is no example in which the recoil implantation method is applied to the formation of the p-type GaN region.
One of the reasons for this is that even if the Mg ions are implanted into the GaN base material by the recoil implantation method, the crystallinity of the GaN base material is damaged, so high-temperature annealing is required to recover from the damage. In addition, since Mg is a material that easily causes anomalous diffusion due to heat, the implanted Mg anomalously diffuses in the GaN base material, making it difficult to form the p-type GaN region. It was assumed that
In fact, the inventor of the present invention applied a p-type GaN layer (non-patterned structure) by uniformly epitaxially growing GaN containing Mg on a GaN substrate layer by MOCVD (chemical vapor deposition), as in commercially available LEDs. (see Non-Patent Document 4, the recoil implantation method is not performed), but in this case, the Mg anomalously diffuses into the GaN base layer. has been confirmed.

S. O. Kucheyev et al., Materials Science and Engineering. 33 (2001) 51-107 Tetsuo Narita et al., Applied Physics Express 10, 016501 (2017) R. S. Nelson, The theory of recoil implantation, Radiation Effects, 2:1, 47-50 (1969) Juichi Yamada et al., "Trial of Recoil Implantation of Mg into GaN by Nitrogen", The 64th JSAP Spring Meeting, Proceedings, 17p-P3-9 (2017)

An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a GaN structure capable of forming a device structure similar to that of a Si device, and a method for manufacturing the same.

In order to solve the above problems, the present inventor conducted further research and found that when the Mg ions are implanted into the GaN base material by the recoil implantation method, the crystallinity can be recovered by the subsequent annealing treatment. The inventors have found that the above-described aberrant diffusion of Mg can be suppressed while the above-mentioned Mg is maintained, and the above-mentioned p-type GaN region can be formed in the above-mentioned GaN base material. This finding means that the ion implantation technology capable of constructing a device structure similar to that of the Si device can be established for the GaN as well, making a leap toward the practical use of the GaN device, which is a next-generation device. bring significant progress.

The present invention is based on the above findings, and means for solving the above problems are as follows. Namely
<1> A layered GaN structure including at least an n-type or non-doped GaN base material region arranged to have a recess and a p-type GaN region containing Mg as a p-type impurity and arranged in the recess The minimum backscattering yield χ _min , which is measured by channeling measurement based on the RBS method for the p-type GaN region and represented by the following formula, H _c /H _r , is 0.04 or less. A GaN structure that
However, in the above formula, the H _c is the backscattered ion energy at the peak of the backscattering yield due to surface scattering in the channeling spectrum obtained by injecting ions in the direction along the crystal axis in the p-type GaN region. In a random spectrum obtained by injecting the _ions from a direction not along the crystal axis, The backscattering yield when having the same backscattering ion energy as the H _c is shown.
<2> The GaN structure according to <1> above, wherein the exposed surface of the p-type GaN region forming part of the surface of the GaN structure has a surface roughness RMS of 1.0 nm or less.
<3> The GaN structure according to any one of <1> to <2> above, wherein the p-type GaN region has a Mg concentration of 1×10 ¹⁵ cm ⁻³ to 1×10 ²¹ cm ⁻³ .
<4> The GaN structure according to any one of <1> to <3>, wherein the maximum diameter of the exposed surface of the p-type GaN region is 10 nm to 10 mm.
<5> The GaN structure according to any one of <1> to <4>, wherein the GaN structure portion further includes an n-type GaN region arranged in the recess, which is the p-type GaN region.
<6> The GaN structure according to any one of <1> to <5>, wherein a structure of either a GaN growth layer or an insulating oxide film is arranged on the surface of the GaN structure.
<7> A laminate in which an Mg layer is laminated on an n-type or non-doped GaN base material layer is irradiated with recoil ions from the Mg layer side in the lamination direction, and Mg ions recoiled from the Mg layer. into the GaN base material layer; an Mg layer removal step of removing the Mg layer from the GaN base material layer implanted with the Mg ions; and the GaN from which the Mg layer has been removed. and an annealing step of annealing a base material layer to activate the Mg ions implanted into the GaN base material layer.
<8> The method for producing a GaN structure according to <7> above, wherein the annealing temperature in the annealing step is less than 1,000°C.
<9> The method for producing a GaN structure according to any one of <7> to <8>, wherein the recoil ions are nitrogen ions.

ADVANTAGE OF THE INVENTION According to this invention, the said various problems in a prior art can be solved, and the GaN structure which can form the device structure similar to a Si device, and its manufacturing method can be provided.

1 is a cross-sectional view showing the outline of a GaN structure according to a first embodiment; FIG. FIG. 4 is a cross-sectional view showing the outline of a GaN structure according to a second embodiment; 1 is a cross-sectional view (1) for explaining a manufacturing process of a GaN structure according to the first embodiment; FIG. FIG. 2B is a cross-sectional view (2) for explaining the manufacturing process of the GaN structure according to the first embodiment; 3 is a cross-sectional view (3) for explaining the manufacturing process of the GaN structure according to the first embodiment; FIG. 4 is a cross-sectional view (4) for explaining the manufacturing process of the GaN structure according to the first embodiment; FIG. 1 is an explanatory diagram showing an outline of a GaN structure according to Example 1; FIG. 4 is an electron microscope image showing the surface of the n-type GaN layer before forming the Mg layer. 4 is an electron microscope image showing the surface of the n-type GaN layer after removing the Mg layer. FIG. 4 is a diagram showing SIMS measurement results for the GaN structure according to Example 1; FIG. 10 is a diagram showing measurement results of RBS measurement on the GaN structure according to Example 1; FIG. 10 is a diagram showing measurement results of SIMS measurement on the GaN structure according to Example 2; FIG. 10 is a diagram showing measurement results of RBS measurement on the GaN structure according to Example 2; FIG. 10 is a cross-sectional view showing an outline of a GaN structure according to Example 2 after electrode formation; FIG. 10 is a diagram showing PL measurement results for the GaN structure according to Example 2; FIG. 11(a) is a diagram showing an enlarged appearance region of DAP in FIG. 11(a). FIG. 10 is a diagram showing IV characteristics for the GaN structure according to Example 2; FIG. 10 is a diagram showing the result of EL measurement on the GaN structure according to Example 2; 13(a) is an enlarged view of the appearance area of the DAP. FIG.

(GaN structure)
The GaN structure of the present invention has a GaN structure and, if necessary, other members.

<GaN structure>
The GaN structure is constructed as a layered member including at least a GaN matrix region and a p-type GaN region.

- GaN base material area -
The GaN base material region is arranged to have a concave portion and is configured as an n-type or non-doped region.
The GaN base material region is formed in a GaN base material layer by a method for manufacturing a GaN structure, which will be described later, and is made p-type by the implantation of Mg ions into the GaN base material layer. The concave portion is formed by the remainder except for .
The constituent material of the GaN base material layer, that is, the constituent material of the GaN base material region, is not particularly limited and can be appropriately selected according to the purpose. , a known GaN substrate can be used, and in the case of n-type conductivity, the GaN substrate is ion-implanted with an n-type impurity (eg, Si), or a GaN layer epitaxially grown on the GaN substrate. can be exemplified by ion-implanting the n-type impurity. The n-type impurity ion implantation, unlike the p-type impurity (Mg) ion implantation, causes less damage to GaN and is widely used as a method for forming n-type GaN.

-p-type GaN region-
The p-type GaN region is configured as a region that contains the Mg as the p-type impurity and is disposed within the recess.
The p-type GaN region is formed by the manufacturing method of the GaN structure, which will be described later, and the core of the technology is that the p-type region of GaN can be arbitrarily patterned in the GaN structure by recoil implantation technology. form.
That is, according to the recoil implantation technique, it is possible to form the p-type GaN region in which the structural damage caused by the Mg ion implantation is suppressed in the GaN base material layer.

As for the p-type GaN region, since structural damage caused by the Mg ion implantation is suppressed, the GaN crystal structure in the region is maintained with less damage.
As a general evaluation method of the crystal structure, there is an evaluation method by the RBS method (Rutherford Backscattering Spectroscopy). The minimum backscattering yield χ _min measured by the channeling measurement based on the RBS method for the p-type GaN region and represented by the following formula, _Hc / _Hr , is 0.12 or less.
However, in the above formula, the H _c is the backscattered ion energy at the peak of the backscattering yield due to surface scattering in the channeling spectrum obtained by injecting ions in the direction along the crystal axis in the p-type GaN region. In a random spectrum obtained by injecting the _ions from a direction not along the crystal axis, The backscattering yield when having the same backscattering ion energy as the H _c is shown.
Further, the minimum backscattering yield χ _min is preferably 0.04 or less because the smaller the value, the less damage the structure has. The lower limit of the minimum backscattering yield χ _min is a value exceeding zero.

The Mg concentration in the p-type GaN region can be widely adjusted by setting the irradiation energy and dose of recoil ions in the recoil implantation step described later, and is 1×10 ¹⁵ cm depending on the desired device structure. ⁻³ to 1×10 ²¹ cm ⁻³ . The ability to adjust the Mg concentration over such a wide range is a significant advantage in constructing various GaN devices.

The GaN structure portion may further include an n-type GaN region arranged in the recess, with the p-type GaN region serving as a recess.
That is, since structural damage is suppressed in the p-type GaN region, the n-type impurity (for example, Si) is further ion-implanted to nest the n-type GaN region in the p-type GaN region. can be formed into
A known ion implantation method can be applied as the method for implanting the n-type impurity ions.

The p-type GaN region is patterned at any location of the GaN matrix layer rather than a uniform film. In other words, by forming the structures in the concave portions of the GaN base material regions in the target regions, it contributes to the realization of various GaN device structures.
Limiting factors for the formation region of the p-type GaN region include processing limits of lithography processing technology using a mask and thermal diffusion of the Mg implanted into the GaN base material layer. Based on these limiting factors, The maximum diameter of the exposed surface of the p-type GaN region can be 10 nm to 10 mm, and being able to set the maximum diameter in such a wide range is important in constructing various GaN devices. be an advantage.
The maximum diameter means the maximum diameter of the outer contour of the p-type GaN region when viewed from the surface side of the GaN structure portion. Even when the n-type GaN region is formed in the GaN-type region, the concept is the same before and after the formation of the n-type GaN region.

The GaN structure portion includes the p-type GaN region having a characteristic that structural damage due to the implantation of the Mg ions is suppressed.
This feature of the p-type GaN region also means that surface roughness of the p-type GaN region due to the implantation of Mg ions can be suppressed. The surface roughness RMS of the exposed surface of the p-type GaN region constituting the is small.
Specifically, the surface roughness RMS can be 1.0 nm or less, preferably 0.5 nm or less.
This feature provides a significant advantage in adding any device structure on the surface of the GaN structure, such as a GaN growth layer as an epitaxial growth layer on the p-type GaN region or an insulating oxide film.
The lower limit of the surface roughness RMS is not particularly limited, but the value of the surface roughness RMS can be set to Since the increase can be suppressed to about 0.096 nm, the surface roughness of the GaN base material layer can be assumed to be 0.11 nm assuming the smallest surface roughness.
As the surface roughness RMS, although it depends on the size of the exposed surface of the p-type GaN region, the measurement result of an arbitrarily selected fixed region (for example, about 2 μm square) is Measurement results may be substituted.

<Other parts>
The other members are not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include the GaN growth layer and the insulating oxide film.

The GaN growth layer is not particularly limited, and includes, for example, a GaN layer grown on the surface of the GaN structure including the exposed surface of the p-type GaN region by a known epitaxial growth method.
The insulating oxide film is not particularly limited, and includes, for example, various insulating oxide films employed in known MOSFET structures, and these can be formed by known forming methods.

Although it is difficult to directly measure the surface roughness RMS of the p-type GaN region with the GaN growth layer and the insulating oxide film formed on the surface, the surface roughness of the p-type GaN region Since the normal GaN growth layer and the insulating oxide film are not formed when . .

Next, an example of the GaN structure according to the present invention will be briefly described with reference to the drawings.
First, FIG. 1 shows a cross-sectional view showing the outline of the GaN structure according to the first embodiment.
As shown in FIG. 1, the GaN structure 1 is constructed as the GaN structure itself as a simple example for explanation, and is arranged such that the p-type GaN region 3 is embedded in the concave portion of the GaN base material region 2 . consists of
Although the GaN base material region 2 is illustrated as having n-type conductivity, it may be non-doped.
The maximum diameter of the exposed surface of the p-type GaN region 3 corresponds to the diameter indicated by symbol W, and can be set within the range of 10 nm to 10 mm.

Next, FIG. 2 shows a cross-sectional view showing the outline of the GaN structure according to the second embodiment.
As shown in FIG. 2, a GaN structure 1′ is constructed as the GaN structure itself as a simple example for explanation, and an n-type GaN region 4 is nested within a p-type GaN region 3 in the GaN structure 1. is formed and configured.

As shown in these embodiment examples, according to the GaN structure of the present invention, a pn junction can be formed at any desired position. can be formed.
It should be noted that these examples of embodiments are limited examples, and the idea of the GaN structure of the present invention is not limited to these examples.
For example, another said p-type GaN region can be formed in the n-type GaN region 4 shown in FIG. Any low loss power device or high frequency electronic device structure may be provided by providing an epitaxial growth layer of GaN or the like, or a MOSFET structure may be provided by providing the insulating oxide film or the like.
These structures result from the formation of the p-type GaN region in the GaN base material layer based on the method of manufacturing the GaN structure according to the present invention. Details will be described below.

(Manufacturing method of GaN structure)
The method for manufacturing the GaN structure according to the present invention includes a recoil implantation process, a Mg layer removal process, an annealing process, and may include other processes as necessary.

<Recoil implantation process>
In the recoil implantation step, a laminate in which an Mg layer is laminated on an n-type or non-doped GaN base material layer is irradiated with recoil ions from the Mg layer side in the lamination direction, and the recoil is applied from the Mg layer. and implanting the Mg ions into the GaN base material layer.

The GaN base material layer is not particularly limited, and may be the known GaN substrate or the known layer into which the n-type impurity is introduced.

A method for laminating the Mg layer on the GaN base material layer is not particularly limited, and includes a known vapor deposition method.

The recoil ion irradiation method is not particularly limited, and examples thereof include irradiation methods using various ion implanters used in known ion implantation methods.
That is, in the recoil implantation step, ion implantation can be performed using an existing ion implantation apparatus, and the cost of introducing new equipment can be reduced.

The target Mg concentration in the p-type GaN region can be set by the irradiation energy and dose amount of the recoil ions.
For example, when the Mg concentration is 1×10 ¹⁵ cm ⁻³ to 1×10 ²¹ cm ⁻³ , the GaN base material of the Mg layer is The irradiation energy that sets the depth of the incident peak near the interface with the layer is selected, and the dose amount is determined so that the Mg concentration becomes the set value.

The recoil ions are not particularly limited, but nitrogen ions are preferred. When the Mg ions are implanted into the GaN base material layer, nitrogen in GaN may be ejected from the GaN base material layer. It can be expected to replace nitrogen ejected from the GaN base material layer.

<Mg layer removal step>
a step of removing the Mg layer from the GaN base material layer implanted with the Mg ions;
A method for performing the Mg removal step is not particularly limited, and examples thereof include a method of removing by reacting with pure water. Moreover, if there is a residue after the reaction with the pure water, it can be removed by further reaction with hydrochloric acid.
According to such a removing method, it is possible to suppress an increase in surface roughness on the surface of the GaN base material layer after removal.

<Annealing process>
A step of annealing the GaN base material layer from which the Mg layer has been removed to activate the Mg ions implanted into the GaN base material layer.
As a method for performing the annealing step, there is an annealing method using a known annealing apparatus. That is, in the annealing step, existing equipment can be used, and the cost of introducing new equipment can be reduced.

The annealing temperature in the annealing step is not particularly limited, but is preferably less than 1,000°C.
Such an annealing temperature can suppress diffusion of the Mg in the GaN base material layer to unintended positions.
The lower limit of the annealing temperature is preferably 700° C. or higher, more preferably 800° C. or higher, from the viewpoint of recovering structural damage caused during the Mg ion implantation.

Next, an example of the method for manufacturing the GaN structure according to the present invention will be described with reference to FIGS. 3(a) to 3(d). 3A to 3D are cross-sectional views (1) to (4) for explaining the manufacturing process of the GaN structure according to the first embodiment.

First, a resist pattern is formed using a stencil mask or a photomask to form a GaN base material layer 2 (here, for simplicity of explanation, the same reference numerals as those of the GaN base material region 2 in the first embodiment are used). A resist layer 5 is formed at a predetermined position above (see FIG. 3(a)).
Next, after depositing the Mg layer 6 on the GaN base material layer 2 on which the resist layer 5 is formed, it is placed in the ion implantation apparatus, and the recoil ions are irradiated from the side of the Mg layer 6 in the stacking direction. The Mg ions recoiled from the layer 6 are implanted into the GaN base material layer 2 (see FIG. 3(b)). Here, the Mg ions implanted into the GaN base material layer 2 form Mg ion implanted regions 3' (see FIG. 3(c)).
Next, the GaN base material layer 2 having the Mg ion-implanted regions 3′ formed thereon is put into a known annealing apparatus and heat-treated to form p-type GaN regions 3 in which the Mg ion-implanted regions 3′ are activated. , to manufacture the GaN structure according to the first embodiment shown in FIG. 1 (see FIG. 3(d)).
The pattern formation method using the resist layer 5 and the Mg layer 6 is merely an example, and other lithographic processes capable of forming a structure similar to that of the p-type GaN region 3 can be used instead of the resist layer 5 and the Mg layer 6. Techniques can be employed as appropriate.

According to the manufacturing method of the GaN structure according to the present invention, since the recoil implantation technique is employed in place of the ion implantation method, structural damage in the GaN base material layer 2 into which the Mg is ion-implanted is suppressed. and this structural damage is recovered by the annealing step.
Therefore, according to the method for manufacturing the GaN structure according to the present invention, the ion implantation of the impurity material (Mg), which is comparable to the fabrication of the Si device by the ion implantation method, is performed by the recoil implantation technique to form the GaN device. , and can bring about a dramatic advance toward the practical use of the GaN device, which is a next-generation device.

<Other processes>
The other steps are not particularly limited, and include known steps for adding a known device structure portion to the GaN base material layer, depending on the desired device structure (for example, FIG. 2). .

(Example 1)
A GaN structure according to Example 1 was manufactured with the configuration shown in FIG. Specific manufacturing conditions are as follows. In addition, FIG. 4 is a cross-sectional view showing an outline of the GaN structure according to the first embodiment. In addition, since we are interested in whether the p-type GaN region can be formed by the recoil implantation technique, the p-type GaN region is patterned in the GaN base material region as shown in the structure shown in FIG. It is not formed, but is formed as a uniform layer.

First, a GaN substrate (manufactured by Mitsubishi Chemical Corporation, C-axis oriented GaN substrate) was prepared as the GaN substrate 17 . This GaN substrate 17 is a dislocation-concentrated substrate in which dislocations in other regions are reduced by intentionally introducing dislocations at a pitch of 700 μm. Also, the GaN substrate 17 is a self-supporting substrate made of GaN. Also, the GaN substrate 17 has a surface crystal structure oriented along the C-axis.
Next, an n-type GaN layer 12 doped with Si as an n-type impurity at a concentration of 2×10 ¹⁶ cm ⁻³ is formed on the surface of the GaN substrate 17 using an MOCVD apparatus (manufactured by Taiyo Nippon Sanso Corporation). It was formed with a thickness of 10 μm.
Next, a Mg layer having a thickness of 250 nm was formed on the surface of the n-type GaN layer 12 using a vacuum deposition apparatus (manufactured by Kitano Seiki Co., Ltd.).
Next, using an ion implanter (manufactured by ULVAC, IH-800UPS), these laminates were irradiated with nitrogen ions in the lamination direction from the Mg layer side at an irradiation energy of 120 keV and a dose of 2×10 ¹⁶ cm ⁻² . A recoil ion plantation process was performed in which the Mg ions recoiled from the Mg layer were implanted into the n-type GaN layer 12 and the surface side of the n-type GaN layer 12 was made the Mg ion implantation region. .
Next, the sample after the recoil ion plantation process was placed in pure water, and the Mg layer removing process was performed to remove the Mg layer present on the Mg ion implantation region.
Next, the sample after the Mg layer removal step is placed in an MOCVD apparatus (manufactured by AIXTRON) and heated at 948° C. for 1 hour in a nitrogen atmosphere, and then further heated at 700° C. for 0.5 hour in the air for an annealing step. was carried out, and the surface side of the n-type GaN layer 12 was used as the p-type GaN layer 13 .
The GaN structure 10 was manufactured as Example 1 by the above.

A measurement result of the surface roughness RMS of the GaN structure according to Example 1 using a scanning probe microscope (manufactured by Hitachi High-Tech Science, AFM5100N) will be described.
FIG. 5(a) shows the state of the surface of the n-type GaN layer 12 before forming the Mg layer. FIG. 5(b) shows the state of the surface of the n-type GaN layer 12 after removing the Mg layer.
The surface roughness RMS that the n-type GaN layer 12 originally had before the formation of the Mg layer obtained as a result of measurement was 0.094 nm, and the surface roughness RMS after the removal of the Mg layer was Since the thickness was 0.19 nm, the surface of the n-type GaN layer 12 was not roughened when the Mg layer was removed. It can be evaluated as a state where it is not.
Moreover, it is assumed that the surface roughness RMS after the annealing step is equal to or less than 0.19 nm after the removal of the Mg layer due to damage recovery.

Next, measurement results of SIMS measurement (secondary ion mass spectrometry) of the GaN structure according to Example 1 using a secondary ion mass spectrometer (IMS 4f, manufactured by CAMECA) will be described.
FIG. 6 shows SIMS measurement results for the GaN structure according to Example 1. In FIG.
As shown in FIG. 6, in the GaN structure according to Example 1 (see "recoil implantation" in the figure), the Mg in the Mg layer migrates from the surface of the n-type GaN layer 12 to a deep position. It is confirmed that there is In the figure, "w/o implantation" indicates the Mg profile of the reference sample in which only the recoil implantation step was not performed in Example 1. Mg migration is confirmed only at extremely shallow positions.

Next, the results of RBS measurement of the GaN structure according to Example 1 using an RBS analyzer (3SDH Pelletron, manufactured by National Electrostatics Corporation) will be described.
FIG. 7 shows the result of RBS measurement for the GaN structure according to Example 1. As shown in FIG. This measurement result shows an RBS spectrum measured by channeling measurement based on the RBS method for the p-type GaN layer 13 . Note that helium ions are used as the incident ions for the measurement.
As a result of the measurement, in the channeling spectrum obtained by injecting ions from the direction (aligned direction) along the crystal axis (<0001>) in the p-type GaN layer 13 shown in FIG. In the range where the backscattering ion energy is smaller than that at the peak, H _c indicating the smallest value of the backscattering yield is 870 counts. In a random spectrum obtained by irradiating the ions at an angle of 160° with the in-plane direction of Hr, Hr, which indicates the backscattering yield when the backscattering ion energy is the same as the _Hc , 7,371 counts, so that the minimum backscattering yield χ _min expressed as H _c /H _r was about 0.12.
In FIG. 7, the hump seen in the channeling spectrum at the backscattering ion energy near 1,780 keV indicates the peak waveform of the backscattering yield associated with the surface scattering.

(Example 2)
A GaN structure according to Example 2 was manufactured in the same manner as in Example 1, except that the thickness of the Mg layer was changed from 250 nm to 400 nm in the recoil implantation step in Example 1.

Measurement results of SIMS measurement of the GaN structure according to Example 2 using the secondary ion mass spectrometer apparatus performed in the same manner as in Example 1 will be described.
FIG. 8 shows the result of SIMS measurement for the GaN structure according to Example 2. In FIG.
As shown in FIG. 8, also in the GaN structure according to Example 2, as in Example 1, the Mg in the Mg layer migrated from the surface of the n-type GaN layer to a deep position. It is confirmed.

Next, the measurement results of the RBS measurement of the GaN structure according to Example 2 using the RBS analyzer apparatus performed in the same manner as in Example 1 will be described.
FIG. 9 shows the result of RBS measurement for the GaN structure according to Example 2. As shown in FIG.
As a _result of the measurement, _{H c} is 275 counts and H _r is 7,942 counts, as shown in _FIG . was 0.03.
In FIG. 9, the hump seen in the channeling spectrum at the backscattering ion energy near 1,780 keV indicates the peak waveform of the backscattering yield associated with the surface scattering.
Thus, in the GaN structure (H _c /H _r =0.03) according to Example 2, the thickness of the Mg layer was changed, and the incidence of nitrogen ions on the Mg layer viewed from the interface with the n-type GaN layer was By changing the position, a p-type GaN layer with less damage than the GaN structure according to Example 1 (H _c /H _r =0.12) is obtained.

Next, using an EB vacuum deposition apparatus (manufactured by ANELVA), a 50 nm thick Ni layer and a 160 nm thick Au layer were formed on the surface of the p-type GaN layer on the GaN structure according to Example 2. were laminated in this order to form an electrode, and heat treatment was performed at 500°C. Various measurements were performed to confirm whether or not the p-type region was formed in the GaN structure according to Example 2 after formation.
Note that FIG. 10 shows an outline of the GaN structure 20 according to Example 2 after forming the electrodes. In the figure, reference numeral 27 indicates a GaN substrate, reference numeral 22 indicates an n-type GaN layer, reference numeral 23 indicates a p-type GaN layer, and reference numeral 28 indicates an electrode.

First, the results of PL (photoluminescence) measurement of the GaN structure (after electrode formation) according to Example 2 using a photoluminescence measuring device (LabRAM-HR PL, manufactured by Horiba, Ltd.) performed at room temperature will be described. .
FIG. 11(a) is a diagram showing the results of PL measurement for the GaN structure according to Example 2. FIG. FIG. 11(b) is an enlarged view of the DAP appearing area in FIG. 11(a).
As shown in FIGS. 11(a) and 11(b), DAP and its phonon replica, DAP-LO, are recognized.
Here, DAP is luminescence in which conduction electrons and holes are combined and annihilated at the interface between an N-type region generated by a donor (D) and a P-type region generated by an acceptor (A). Point to the signal. Also, LO is a longitudinal optical mode phonon, and an emission signal in which one longitudinal optical mode phonon intervenes in the emission of DAP is DAP-LO. Both are luminescence signals derived from crystals. Emission with a wavelength shorter than that is associated with band edge emission that occurs in GaN, which is a direct transition semiconductor.
Since the presence of DAP means the presence of a PN junction, the p-type GaN layer 23 in the GaN structure according to Example 2 is considered to have p-type conductivity.

Next, measurement results of the IV characteristics of the GaN structure (after electrode formation) according to Example 2 using a semiconductor device parameter analyzer (manufactured by KEYSIGHT, B1500A) will be described. In addition, the measurement was performed in a temperature environment of 100K.
FIG. 12 is a diagram showing IV characteristics for the GaN structure according to Example 2. In FIG.
As shown in FIG. 12, rectification characteristics are confirmed. Rectification characteristics are observed in both Schottky diodes and PN junction diodes. No bumps such as those shown in 12 are present. On the other hand, in a PN junction diode, since both electron and hole carriers are injected, a current signal due to their recombination is seen at the beginning of voltage application, but when the voltage is higher than that, an increase due to injection of single carriers. Two humps are observed as shown in FIG.
Therefore, also from the measurement results of the IV characteristics, the p-type GaN layer 23 of the GaN structure according to Example 2 has p-type conductivity, and the device structure of the PN junction diode can be realized. I can say.

Next, Example 2 using a current applying device (KEITHLEY, 2450 SourceMeter), a monochromator (Horiba, HR 460), and a spectroscope (Horiba, Synapse) was performed at room temperature. The results of EL (Electroluminescence) measurement of the GaN structure (after forming the electrodes) will be described.
FIG. 13(a) is a diagram showing the result of EL measurement for the GaN structure according to Example 2. FIG. FIG. 13(b) is an enlarged view of the DAP appearing area in FIG. 13(a).
As shown in FIG. 13(a), no band-edge emission was observed when the forward current was 0 mA, and DAP was observed when 20 mA was applied. Generally, when a diode is positively biased, hole carriers are supplied from one current terminal to the p-type region, and electron carriers are supplied from the other current terminal to the n-type region, and these carriers are reproduced at the PN junction interface. Combine and disappear. That is, in the case of such an EL measurement, electron-hole recombination occurs at the PN junction interface, so band edge emission does not occur, and only emission due to DAP and some defect occurs. Here, DAP and band edge emission have different wavelengths, so they can be clearly distinguished.
Also, even if it is confirmed by enlarging it in FIG. 13(b), the DAP can be clearly confirmed, but no band-edge emission is observed. Even assuming that the diode as the GaN structure according to Example 2 is a Schottky diode, the carriers injected from the electrode are single carriers of only electrons. In situations where the signal cannot be observed, this assumption does not hold.
Therefore, it can be determined that this diode is a PN junction diode, not a Schottky diode, and it is more clearly demonstrated that the p-type GaN layer 23 has p-type conductivity.

Reference Signs List 1, 1', 10, 20 GaN structure 2 GaN base material region 3 p-type GaN region 3' Mg ion implantation region 4 n-type GaN region 5 resist 6 Mg layer 12, 22 n-type GaN layer 13, 23 p-type GaN Layers 17, 27 GaN substrate 28 electrode

Claims (9)

At least a layered GaN structure portion including a n-type or non-doped GaN base material region arranged to have a recess, and a p-type GaN region containing Mg as a p-type impurity and arranged in the recess. death,
A GaN structure characterized in that a minimum backscattering yield χ _min measured by channeling measurement based on the RBS method for the p-type GaN region and represented by the following formula H _c /H _r is 0.04 or less.
However, in the above formula, the H _c is the backscattered ion energy at the peak of the backscattering yield due to surface scattering in the channeling spectrum obtained by injecting ions in the direction along the crystal axis in the p-type GaN region. In a random spectrum obtained by injecting the _ions from a direction not along the crystal axis, The backscattering yield when having the same backscattering ion energy as the H _c is shown. 2. The GaN structure according to claim 1, wherein the exposed surface of the p-type GaN region forming part of the surface of the GaN structure has a surface roughness RMS of 1.0 nm or less. 3. The GaN structure according to claim 1, wherein the Mg concentration in the p-type GaN region is 1×10 ¹⁵ cm ⁻³ to 1×10 ²¹ cm ⁻³ . 4. The GaN structure according to any one of claims 1 to 3, wherein the maximum diameter of the exposed surface of the p-type GaN region is 10 nm to 10 mm. 5. The GaN structure according to any one of claims 1 to 4, wherein the GaN structure portion further includes an n-type GaN region arranged in the recess with the p-type GaN region serving as a recess. 6. The GaN structure according to any one of claims 1 to 5, wherein a structure of either a GaN grown layer or an insulating oxide film is arranged on the surface of the GaN structure. A laminate in which an Mg layer is laminated on an n-type or non-doped GaN base material layer is irradiated with recoil ions from the Mg layer side in the lamination direction, and Mg ions recoiled from the Mg layer are transferred to the GaN layer. a recoil implantation step of injecting into the base material layer;
an Mg layer removing step of removing the Mg layer from the GaN base material layer implanted with the Mg ions;
An annealing step of annealing the GaN base material layer from which the Mg layer has been removed to activate the Mg ions implanted into the GaN base material layer;
A method for manufacturing a GaN structure, comprising: 8. The method of manufacturing a GaN structure according to claim 7, wherein the annealing temperature in the annealing step is less than 1,000[deg.]C. 9. The method for manufacturing a GaN structure according to claim 7, wherein the recoil ions are nitrogen ions.

Images