JP2021002575A - Structure, optical device, and their manufacturing methods - Google Patents

Abstract

To provide a technique for obtaining a device capable of being driven with a high efficiency while holding down the device manufacturing cost.SOLUTION: A structure 10 comprises a group III nitride semiconductor substrate 100 arranged so that a semipolar surface makes a first principal face 101, and a multilayer structure 200. The multilayer structure 200 includes a quantum well structure 220. In a graph, of which the abscissa represents a peak wavelength λp[nm] of photoluminescence spectra and the ordinate represents a polarization ratio Rp of light emitted by photoluminescence, the plots of results obtained by photoluminescence of the structure 10 arranged to have an excitation wavelength of 325 nm are located in a first parallelogram. The first parallelogram is defined by a straight line λp=360, a straight line λp=560, a straight line Rp=-0.005 λp+2.2 and a straight line Rp=-0.005 λp+1.4. The polarization ratio Rp of photoluminescence of the structure 10 arranged to have an excitation wavelength of 325 nm is smaller than 0.SELECTED DRAWING: Figure 1

Description

The present invention relates to a structure, an optical device, a method for manufacturing an optical device, and a method for manufacturing a structure.

Power saving is required for optical devices such as lasers. In group III nitride semiconductors, it is expected that the internal electric field will be reduced and the internal quantum efficiency will be improved by forming the device on the semi-polar plane.

Patent Document 1 describes that a quantum well structure is provided on a main surface which is a semi-polar surface of a gallium nitride based semiconductor region. Here, it is described that the thickness of the well layer is 4 nm or more.

Patent Document 2 describes that a wavy portion is provided in a well layer in a quantum well structure formed on a (20-2-1) plane which is a semi-polar plane of a nitride semiconductor. It is also described that such a well layer can radiate polarized luminescence.

Patent Document 3 describes that a multiple quantum well layer or the like is laminated on a u-GaN layer whose main surface is a {11-22} surface.

Patent Document 4 describes that a nitride semiconductor layer is epitaxially grown on a substrate having a main surface. Here, as the substrate, a nitride semiconductor substrate in which the normal of the main surface is inclined at an angle in the range of 5 degrees or more and 17 degrees or less in the + c-axis direction from the [11-22] axis of the nitride semiconductor is mentioned. Has been done.

Non-Patent Document 1 describes the polarization ratio of light emitted from LDs and LEDs formed on the {20-21} plane, which is a semi-polar plane, and a single quantum well formed on the {11-22} plane. The polarization ratio of the light emitted from the structure is described.

Japanese Unexamined Patent Publication No. 2012-109624 Japanese Unexamined Patent Publication No. 2013-258275 International Publication No. 2013/128894 Japanese Unexamined Patent Publication No. 2016-12717

Takashi Kyono, 7 outsiders, "Optical Polarization Characteristics of InGaN Quantum Wells for Green Laser Diodes on Semi-Polar {2021} GaN Substrates", Applied Physics Express, Japan Society of Applied Physics, January 8, 2010, 3rd Volume, No. 1, p. 011003.1-1-011003.3

However, there is still room for consideration to obtain a device that can be driven with high efficiency while suppressing the manufacturing cost of the device.

The present invention provides a technique for obtaining a device that can be driven with high efficiency while suppressing the manufacturing cost of the device.

According to the present invention
A group III nitride semiconductor substrate having a semi-polar surface as the first main surface,
A structure comprising a multilayer structure made of a group III nitride semiconductor laminated on the first main surface of the substrate or on the second main surface opposite to the first main surface.
The multilayer structure includes a quantum well structure.
With the axis of the c-axis projected onto the first main surface as the c-projection axis, the polarization ratio Rp of the light emitted by photoluminescence is Rp = (intensity of m-axis polarization component-c-projection-axis polarization component) / (m). It is expressed by (intensity of axially polarized light component + c intensity of projected axis polarized light component).
In a graph in which the peak wavelength λp [nm] of the maximum peak in the range of 360 nm or more and 560 nm or less in the photoluminescence spectrum is on the horizontal axis and the polarization ratio Rp is on the vertical axis, the photoluminescence of the structure having an excitation wavelength of 325 nm. The resulting plot obtained in is located inside the first parallelogram,
The first parallelogram is composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, and a straight line Rp = -0.005λp + 1.4.
Provided is a structure having a polarization ratio Rp of less than 0 obtained by photoluminescence of the structure having an excitation wavelength of 325 nm.

According to the present invention
With the above structure
An optical device including a first electrode and a second electrode electrically connected to the multilayer structure is provided.

According to the present invention
A method for manufacturing an optical device for forming a first electrode and a second electrode electrically connected to the multilayer structure is provided for the above structure.

According to the present invention
It is a method of manufacturing a structure.
A group III nitride semiconductor is placed on the first main surface of a substrate of a group III nitride semiconductor having a semipolar surface as the first main surface or on the second main surface opposite to the first main surface. Includes a forming step of growing to form a multi-layer structure
The multilayer structure includes a quantum well structure.
With the axis of the c-axis projected onto the first main surface as the c-projection axis, the polarization ratio Rp of the light emitted by photoluminescence is Rp = (intensity of m-axis polarization component-c-projection-axis polarization component) / (m). It is expressed by (intensity of axially polarized light component + c intensity of projected axis polarized light component).
In a graph in which the peak wavelength λp [nm] of the maximum peak in the range of 360 nm or more and 560 nm or less in the photoluminescence spectrum is on the horizontal axis and the polarization ratio Rp is on the vertical axis, the photoluminescence of the structure having an excitation wavelength of 325 nm. The resulting plot obtained in is located inside the first parallelogram,
The first parallelogram is composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, and a straight line Rp = -0.005λp + 1.4.
Provided is a method for producing a structure having a polarization ratio Rp of less than 0 obtained by photoluminescence of the structure having an excitation wavelength of 325 nm.

According to the present invention, it is possible to provide a technique for obtaining a device that can be driven with high efficiency while suppressing the manufacturing cost of the device.

It is a figure which illustrates the structure of the structure which concerns on 1st Embodiment. It is a figure for demonstrating the condition about polarization. It is a figure which illustrates the structure of the apparatus which measures the intensity of the c-projection axis polarization component, and the intensity of the m-axis polarization component of light emitted by photoluminescence. It is a figure which illustrates the structure which has a multiple quantum well structure as a quantum well structure. It is a figure which illustrates the structure of the structure which concerns on 2nd Embodiment. It is a figure which illustrates the structure of the optical device which concerns on 2nd Embodiment. It is a figure which shows the structure of the structure which concerns on Example 1. FIG. It is a figure which shows the surface temperature in the forming process which concerns on Example 1. It is a figure which shows the structure of the structure which concerns on Example 2 to Example 5. It is a figure which shows the surface temperature in the forming process which concerns on Example 2 to Example 5. It is a figure which shows the result of having performed the photoluminescence measurement on the structure of Example 1. FIG. It is a figure which shows the result of having performed the photoluminescence measurement on the structure of Example 2. It is a figure which shows the result of having performed the photoluminescence measurement on the structure of Example 3. It is a figure which shows the result of having performed the photoluminescence measurement on the structure of Example 4. It is a figure which shows the result of having performed the photoluminescence measurement on the structure of Example 5. 6 is a graph plotting the results of photoluminescence of the structures of Examples 1 to 5.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate.

FIG. 1 is a diagram illustrating the configuration of the structure 10 according to the first embodiment. The structure 10 includes a substrate 100 and a multilayer structure 200. The substrate 100 is a group III nitride semiconductor substrate having a semi-polar surface as a first main surface 101. The multilayer structure 200 is a structure made of a group III nitride semiconductor laminated on the first main surface 101 or the second main surface 102 of the substrate 100. Here, the second main surface 102 is the main surface of the substrate 100 opposite to the first main surface 101. Further, the multilayer structure 200 includes a quantum well structure 220. Then, in a graph in which the peak wavelength λp [nm] of the photoluminescence spectrum is on the horizontal axis and the polarization ratio Rp of the light emitted by photoluminescence is on the vertical axis, the photoluminescence of the structure 10 having an excitation wavelength of 325 nm is obtained. The resulting plot is located inside the first parallel quadrilateral. Here, the peak wavelength λp is the peak wavelength of the maximum peak in the range of 360 nm or more and 560 nm or less. Further, with the axis obtained by projecting the c-axis onto the first main surface 101 as the c-projection axis, the polarization ratio Rp is Rp = (intensity of m-axis polarization component −c intensity of projection-axis polarization component) / (intensity of m-axis polarization component). + C Projection axis It is represented by the intensity of the polarized light component). The first parallelogram is composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, and a straight line Rp = -0.005λp + 1.4. The polarization ratio Rp obtained by photoluminescence of the structure 10 having an excitation wavelength of 325 nm is less than 0. This will be described in detail below.

A component in which the vibration direction of the electric field of light is orthogonal to the m-axis is called an m-axis polarized light component. A component in which the vibration direction of the electric field of light is orthogonal to the c-axis projection axis is called a c-axis projection component. Further, in the above graph, the fact that the plot of the result obtained by photoluminescence of the structure having the excitation wavelength of 325 nm is located inside the first parallelogram is also referred to as "condition related to polarization".

When a device (eg, optical device, electronic device, etc.) is formed on the c-plane, which is the polar plane of a group III nitride semiconductor crystal, the internal quantum efficiency decreases due to the internal electric field. In particular, in the quantum well structure on the polar surface, the internal electric field increases as the In composition is increased in order to increase the wavelength, which is a problem. Therefore, attempts have been made to form the device on a so-called semi-polar surface (a surface different from the polar surface and the non-polar surface). It is considered that if the device is formed on the semipolar plane, the internal electric field can be significantly reduced and the internal quantum efficiency can be increased as compared with the case where the device is formed on the c plane.

In addition, when manufacturing a laser, the cleavage surface functions as a mirror surface, so that the manufacturing cost of the device can be reduced. In a group III nitride semiconductor, for example, it is conceivable that the m-plane is a cleavage plane and the m-plane is a mirror plane. In that case, the cavity is provided in the m-axis direction.

The structure 10 according to the present embodiment satisfies the above-mentioned conditions relating to polarization. By doing so, when the laser is manufactured with the cleavage plane as the mirror plane, a large gain can be secured in the cavity direction. Specifically, in the light emitted from the quantum well structure, the gain in the cavity direction can be increased by increasing the proportion of the polarization component of the c projection axis. As a result, a highly efficient and energy-saving drive device can be obtained.

The structure 10 is preferably used for producing a laser, but the use of the structure 10 is not particularly limited. The structure 10 may be used for manufacturing an optical device other than a laser.

FIG. 2 is a diagram for explaining conditions relating to polarization. The horizontal axis of the graph shown in this figure is the peak wavelength λp, and the vertical axis is the polarization ratio Rp. Further, in the graph, a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, a straight line Rp = -0.005λp + 1.4, and a straight line Rp = -0.005λp + 1.6. The part is drawn. The four sides of the first parallelogram overlap λp = 360, straight line λp = 560, straight line Rp = -0.005λp + 2.2, and straight line Rp = -0.005λp + 1.4, respectively. That is, the vertices of the first parallelogram are (λp, Rp) = (360, 0.4), (560, -0.6), (560, -1.4), (360, -0. There are four points in 4).

Regarding the conditions for polarization, in this graph, the plot of the result obtained by photoluminescence of the structure 10 having an excitation wavelength of 325 nm is located inside the first parallelogram, and the excitation wavelength is 325 nm. The polarization ratio Rp obtained by photoluminescence of body 10 is less than 0. Of the light emitted by the structure 10, the intensity of the c-projection-axis polarization component is greater than the intensity of the m-axis polarization component. As a result, the optical gain in the cavity direction when the m-plane is a mirror plane can be further improved, and a highly efficient light emitting device can be realized.

In this graph, the resulting plot obtained by photoluminescence of structure 10 with an excitation wavelength of 325 nm may be further located inside the second parallelogram below. The second parallelogram is a parallelogram composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = −0.005λp + 2.2, and a straight line Rp = −0.005λp + 1.6. The vertices of the second parallelogram are (λp, Rp) = (360, 0.4), (560, -0.6), (560, -1.2), (360, -0.2). There are four points.

FIG. 3 is a diagram illustrating the configuration of the device 40 for measuring the intensity of the c-axis polarized light component and the intensity of the m-axis polarized light component of the light emitted by photoluminescence. In this figure, the light path is shown by solid arrows and broken lines.

The light source 420 is a laser light source, specifically, a He-Cd laser that emits light at a wavelength of 325 nm. The light emitted from the light source 420 enters the measurement target 500 (for example, the structure 10) through the mirror 421, the emission line cut filter 422, the mirror 423, the mirror 424, and the lens 425. Then, the light emitted from the measurement target 500 by photoluminescence is collimated by the lens 431, and a part of the light is incident on the polarizer 432. In the polarizer 432, the polarization component to be transmitted can be switched by changing the angle thereof. The light transmitted through the polarizer 432 is focused on the light receiving unit 434 by the lens 433 and received by the light receiving unit 434. The receiver 435 is composed of a spectroscope and a CCD detector. The light received by the light receiving unit 434 is separated by the spectroscope of the light receiving unit 435 and received by the CCD detector. Then, the intensity of each wavelength is detected by the CCD detector.

Further, for the data obtained by the receiver 435, in addition to the sensitivity correction of the CCD receiver performed by the usual photoluminescence measurement, the angle dependence of the polarizer transmission intensity is corrected as follows, for example. First, using an InGaN quantum well structure (emission wavelength 450 nm) on the c-plane that emits unpolarized light, the intensity P ₀ when the angle of the polarizer is 0 ° and the intensity P ₉₀ when the angle is 90 ° are set. Measure. Then, the value of P ₉₀ / P ₀ is calculated for each wavelength, and the average value of the calculated values is obtained. Then, the corrected intensity is obtained by multiplying the average value by the measurement data of the measurement target 500 when the angle of the polarizer is 90 °.

The structure of the structure 10 will be described in detail below. Examples of the substrate 100 include a GaN substrate. The substrate 100 is a self-supporting substrate. The thickness of the substrate 100 is not particularly limited, but is preferably 100 μm or more from the viewpoint of ease of handling. Further, from the viewpoint of miniaturization of the structure 10, the thickness of the substrate 100 is preferably 1.5 mm or less. The substrate 100 may be an undoped substrate or an n-type or p-type semiconductor substrate.

The first main surface 101 of the substrate 100 is a surface having an off angle of 10 ° or less from the {11-2n} surface or the {11-2n} surface, and n is a number of 0 or more. n is preferably an integer that holds 0 ≦ n ≦ 4, and more preferably n = 3. The multilayer structure 200 may be formed on the first main surface 101 side of the substrate 100, or may be formed on the second main surface 102 side. The first main surface 101 is, for example, a (11-2n) surface or a surface whose off angle from the (11-2n) surface is within 10 °. In this case, the second main surface 102 is the (-112-n) surface or the surface whose off angle from the (-112-n) surface is within 10 °. In the structure 10, the multilayer structure 200 is in contact with the first main surface 101 or the second main surface 102 of the substrate 100. The multilayer structure 200 includes a plurality of layers laminated with each other.

The substrate 100 preferably has a certain degree of high crystallinity. Specifically, of the first main surface 101 and the second main surface 102 of the substrate 100, the half width of ω of (112) of the X-ray locking curve (XRC) measured with respect to the surface on the multilayer structure 200 side is In the following m-axis incident measurement, 500 arcsec. It is preferably 200 arcsec. More preferably: Further, among the first main surface 101 and the second main surface 102 of the substrate 100, the half width of ω of (112) of the X-ray locking curve (XRC) measured with respect to the surface on the side forming the multilayer structure 200 is In the following c-projection axis incident measurement, 500 arcsec. It is preferably 200 arcsec. More preferably: The full width at half maximum in the m-axis incident measurement and the c-projection-axis incident measurement is, for example, 30 arcsec. It may be the above.

The X-ray locking curve measurement will be described below. Since the space group of the unit cell of the group III nitride semiconductor is P63 mc, X-ray diffraction from, for example, the {11-23} plane cannot be obtained due to the annihilation law. Therefore, for example, the locking curve measurement is performed on the {11-22} plane, which is a plane relatively close to the {11-23} plane.

In particular, the semipolar plane of a group III nitride semiconductor often has crystallinity anisotropy in the m-axis direction and the c-projection axis direction with respect to the main plane. Therefore, for example, the X-ray locking curve is measured in these two axial directions. Specifically, in the evaluation of the XRC (112) ω half price width, X-rays are incident parallel to the main surface of the measurement target in parallel with the m-axis, and the incident direction of the X-rays and the angle formed by the main surface are scanned. Two types of measurement are performed: axis incident measurement and c-projection axis incident measurement in which X-rays are incident parallel to the c-projection axis of the main surface to be measured and the angle between the X-ray incident direction and the main surface is scanned. .. By doing so, the crystallinity in each direction can be evaluated.

For example, the off angle from the {11-23} plane can be calculated from the result of the locking curve measurement for the {11-22} plane. Specifically, in order to calculate the off-angles in the m-axis direction and the c-projection-axis direction from the {11-23} plane on the main surface to be measured, the m-axis incident measurement of the above-mentioned X-ray locking curve measurement and c. For each of the projection axis incident measurements, the substrate 100 is rotated 180 ° in the in-plane direction of its main surface. Based on the off angles in the m-axis direction and the c-projection axis direction obtained from the results of these measurements, the final off-angle, that is, the angle formed by the {11-23} plane and the main plane to be measured can be calculated.

Further, among the first main surface 101 and the second main surface 102 of the substrate 100, the dark spot density of the surface on the multilayer structure 200 side is preferably 1 × 10 ⁷ cm- ² or less, and 3 × 10 ⁶ cm ^−. It is more preferably ² or less. The dark spot density may be, for example, 1 × 10 ⁴ cm- ² or more. The scotoma density can be derived by cathodoluminescence (CL) measurement.

Of the first main surface 101 and the second main surface 102 of the substrate 100, the size of the radius of curvature of the surface on the side forming the multilayer structure 200 is preferably 0.5 m or more in the m-axis direction and 2 m or more. Is more preferable. Further, the radius of curvature of the surface of the first main surface 101 and the second main surface 102 of the substrate 100 on the side forming the multilayer structure 200 is preferably 0.5 m or more in the c projection axis direction. More preferably, it is 2 m or more. The radius of curvature of the surface on the side forming the multilayer structure 200 may be, for example, 100 m or less. The radius of curvature in each direction can be calculated, for example, from the result of the above-mentioned X-ray locking curve measurement.

The multilayer structure 200 includes a quantum well structure 220. The quantum well structure 220 has an alternating laminated structure of a GaN layer 222 and an InGaN layer 224. The quantum well structure 220 may be a single quantum well structure or a multiple quantum well structure. Another layer may or may not be present between the quantum well structure 220 and the substrate 100.

FIG. 1 is a diagram illustrating a structure 10 having a single quantum well structure as a quantum well structure 220. FIG. 4 is a diagram illustrating a structure 10 having a multiple quantum well structure as the quantum well structure 220. In the quantum well structure 220, the InGaN layer 224 is sandwiched between the GaN layers 222, the InGaN layer 224 functions as a well layer, and the InGaN layer 224 functions as a barrier layer. The interface between the InGaN layer 224 and the GaN layer 222 is preferably flat, and the interface between the InGaN layer 224 and the GaN layer 222 is preferably not uneven with a height larger than the film thickness of the InGaN layer 224. When the quantum well structure 220 is a multiple quantum well structure, the number of InGaN layers 224 included in the quantum well structure 220 is preferably 2 or more and 5 or less, for example.

The thickness of the InGaN layer 224 is preferably 3 nm or less, more preferably less than 3 nm, and even more preferably 2.5 nm or less. By doing so, it is possible to suppress the occurrence of lattice failure and defects and to form a good 220. Further, in order to obtain a more uniform film, the thickness of the InGaN layer 224 is preferably 1.5 nm or more.

In the quantum well structure of a III nitride semiconductor, the emission wavelength can be lengthened to green or the like by increasing the In composition of the InGaN layer. However, a higher In composition is required on the semi-polar surface than on the polar surface. On the other hand, when the In composition is increased, the lattice constant of the InGaN crystal becomes large and the inconsistency with the GaN layer becomes large. As a result, the crystal structure becomes very fragile due to lattice relaxation, lattice failure, and the like.

Here, focusing on the film thickness of the InGaN layer, a certain thickness is required to form a uniform film. On the other hand, if the film thickness becomes too thick, lattice failure occurs. As the number of quantum wells increases, it becomes difficult to obtain a better crystal structure. Therefore, in order to form a quantum well structure capable of emitting light at a long wavelength on a semi-polar surface, it is necessary to highly control the In composition and the film thickness.

In the structure 10 according to the present embodiment, a high-quality quantum well structure 220 can be realized by reducing the thickness of the InGaN layer 224 to some extent, for example, 3 nm or less. Further, by setting the thickness of the InGaN layer 224 to 3 nm or less, the In composition of the InGaN layer 224 can be enhanced, and light emission at a long wavelength becomes possible. Further, it is considered that the composition fluctuation of In becomes small in the thin InGaN layer 224, and the transition can be generated between the same levels. Therefore, for example, when a laser is manufactured using the structure 10, it is presumed that the laser oscillation will be facilitated.

The composition of the InGaN layer 224 is represented by In _x Ga _(1-x) N. Here, for example, it is preferable that 0.1 ≦ x ≦ 0.75 holds. However, in order to enable highly efficient light emission in the green wavelength region, it is more preferable that 0.28 ≦ x ≦ 0.5 is satisfied, and it is more preferable that 0.3 ≦ x ≦ 0.4 is held.

The thickness of the GaN layer 222 is not particularly limited, but is, for example, 10 nm or more and 100 nm or less. When the quantum well structure 220 is a multiple quantum well structure, the thickness of the GaN layer 222 located between the two InGaN layers 224 is preferably 10 nm or more and 50 nm or less. In the quantum well structure 220, the thicknesses of the plurality of GaN layers 222 may or may not be the same. Further, the GaN layer 222 may be doped with Si. When the GaN layer 222 is doped with Si, the concentration of Si in the GaN layer 222 is preferably 5 × 10 ¹⁷ cm ^-3 or more and 1 × 10 ¹⁹ cm ^-3 or less.

It is preferable that a homoepitaxial GaN layer is contained between the substrate 100 and the InGaN layer 224. By doing so, a good quality quantum well structure 220 can be formed. The homoepitaxial GaN layer may also serve as the GaN layer 222 which is a barrier layer. The film thickness of the homoepitaxial GaN layer is preferably 10 nm or more and 10000 nm or less.

The presence or absence of the quantum well structure 220 in the multilayer structure 200 can be confirmed by, for example, a method using a transmission electron microscope (TEM) or a method of performing X-ray diffraction measurement. If the existence of the quantum well structure 220 can be confirmed at least by one of these methods, it can be determined that the multilayer structure 200 includes the quantum well structure 220. Specifically, in the method using TEM, each film thickness of the InGaN layer and the GaN layer is confirmed. In the method of performing X-ray diffraction measurement, the main diffraction from the GaN layer, the main diffraction from the InGaN layer, and the fringe (periodic vibration) thereof are confirmed.

The peak wavelength λp obtained by photoluminescence of the structure 10 having an excitation wavelength of 325 nm can be 500 nm or more and 560 nm or less. According to such a structure 10, a device that emits green light can be realized. Further, the half width of the maximum peak in the range of 360 nm or more and 700 nm or less in the photoluminescence spectrum of the structure 10 having an excitation wavelength of 325 nm can be, for example, 100 nm or less, and further can be 60 nm or less.

The peak intensity of the first peak appearing in the photoluminescence spectrum of the structure 10 having an excitation wavelength of 325 nm is preferably 1 time or more, preferably 1.5 times or more the peak intensity of the second peak. More preferred. Here, the first peak is a peak having the maximum peak intensity in the wavelength range of 500 nm or more and 560 nm or less. The first peak may be, for example, a peak having a peak wavelength of λp. The second peak is the peak having the maximum peak intensity in the wavelength range of 350 nm or more and 400 nm or less. The second peak is, for example, the emission peak of GaN. That is, when the structure 10 emits green light, it is preferable that the structure 10 includes a quantum well structure 220 having sufficient structural accuracy so as to have a first peak of such intensity.

The peak wavelength λp of the photoluminescence spectrum of the structure 10 can be set by adjusting the In composition of the InGaN layer 224 and the like. The emission color of the structure 10 is not limited to green, and may be red, blue, or the like. The peak wavelength λp can be, for example, in the range of 360 nm or more and 700 nm or less, or in the range of 360 nm or more and 560 nm or less.

The angle formed by at least one cleavage surface of the structure 10 and the first main surface 101 is preferably 75 ° or more and 105 ° or less, more preferably 80 ° or more and 100 ° or less, and 85 ° or more and 95 ° or more. It is more preferably ° or less. By doing so, it is possible to easily manufacture a laser having the cleavage plane as a mirror plane by using the structure 10. This cleavage plane is, for example, the m plane.

Further, the structure 10 may be a device. The structure 10 may further include electrodes.

The structure 10 according to the present embodiment can be manufactured by a manufacturing method including a forming step. In the forming step, a group III nitride semiconductor is grown on the first main surface 101 or the second main surface 102 of the substrate 100 to form the multilayer structure 200. The substrate 100 is a group III nitride semiconductor substrate having a semi-polar surface as a first main surface 101. The second main surface 102 is a main surface of the substrate 100 opposite to the first main surface 101. The multilayer structure 200 includes a quantum well structure 220. Then, in a graph in which the peak wavelength λp [nm] of the photoluminescence spectrum is on the horizontal axis and the polarization ratio Rp of the light emitted by photoluminescence is on the vertical axis, the photoluminescence of the structure 10 having an excitation wavelength of 325 nm is obtained. The resulting plot is located inside the first parallel quadrilateral. Here, the peak wavelength λp is the peak wavelength of the maximum peak in the range of 360 nm or more and 560 nm or less. Further, with the axis obtained by projecting the c-axis onto the first main surface 101 as the c-projection axis, the polarization ratio Rp is Rp = (intensity of m-axis polarization component −c intensity of projection-axis polarization component) / (intensity of m-axis polarization component). + C Projection axis It is represented by the intensity of the polarized light component). The first parallelogram is composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, and a straight line Rp = -0.005λp + 1.4. The polarization ratio Rp obtained by photoluminescence of the structure 10 having an excitation wavelength of 325 nm is less than 0. This will be described in detail below.

The multilayer structure 200 can be formed by using, for example, the MOCVD method. Also, V group material gas used for forming the multilayer structure 200 is NH ₃ gas, for example, III group material gas is an organometallic gas. Examples of the organometallic gas include trimethylGa (TMGa), triethylGa (TEGa), trimethylIn (TMIn), trimethylAl (TMAl), and triethylAl (TEAl). The group V raw material gas and the group III raw material gas are reactive gases that react with each other. Further, in the forming step, the carrier gas may be further supplied to the growth chamber of the MOCVD apparatus. The carrier gas is, for example, hydrogen (H ₂ ) gas and nitrogen (N ₂ ) gas, and does not react with the raw material gas. When TMGa gas is used as the group III raw material gas, the temperature of the supplied TMGa gas is preferably −5 ° C. or higher and 25 ° C. or lower, and more preferably 0 ° C. or higher and 20 ° C. or lower. When TMIn gas is used as the group III raw material gas, the temperature of the supplied TMIn gas is preferably 25 ° C. or higher and 55 ° C. or lower, and more preferably 30 ° C. or higher and 50 ° C. or lower. However, the temperature of each gas can be appropriately set according to the configuration of the MOCVD apparatus, the vapor pressure required for manufacturing the multilayer structure 200, and the like. Each gas to be supplied can be brought to a desired temperature by using, for example, a constant temperature bath.

By arranging the substrate 100 in the growth chamber of the MOCVD apparatus and supplying the group III raw material gas containing Ga and the group V raw material gas, a layer made of GaN such as the GaN layer 222 can be grown. Further, by supplying the group III raw material gas containing Ga, the group III raw material gas containing In, and the group V raw material gas, a layer made of InGaN such as InGaN layer 224 can be grown.

In the forming step, the surface temperature, the growth pressure, and the supply amount of each gas can be controlled. Here, the surface temperature is the temperature of the surface on which the crystal is to be grown, that is, the temperature of the surface to which the raw material gas is supplied. The surface temperature can be either the temperature of the main surface of the substrate 100 or the temperature of the crystal surface laminated on the substrate 100. The surface temperature can be measured using, for example, a pyrometer. The surface temperature during crystal growth is also referred to as a growth temperature.

The first to third conditions for manufacturing the structure 10 will be described below. By satisfying all of the first to third conditions in the forming step, it is possible to obtain a structure 10 including a high-quality multilayer structure 200 and satisfying the conditions relating to polarization. In particular, it is preferable that at least the first to third conditions are satisfied when forming the quantum well structure 220. However, the method for producing the structure 10 is not particularly limited as long as the conditions relating to polarization are satisfied. The method satisfying the first to third conditions is an example of a method for manufacturing the structure 10.

The first condition is that the forming step includes a film forming interruption step or a hydrogen gas supply step described below.

The interruption step is a step of interrupting growth between at least one layer. Specifically, for example, the crystal growth is stopped by stopping the supply of at least one of the group III raw material gas and the group V raw material gas in the interruption step. During the interruption step, the surface temperature may be changed to increase or decrease as described above. In the interruption step, the supply of one of the group III raw material gas and the group V raw material gas may be continued. For example, in the interruption process, the group III raw material gas is not supplied, but the group V raw material gas is supplied. The interruption step is preferably performed every time the surface temperature is changed. Further, the interruption step is preferably performed between all layers of the layers included in the quantum well structure 220, and more preferably performed between all layers of the layers included in the multilayer structure 200. Each interruption step is preferably 30 seconds or more and 180 seconds or less.

The hydrogen gas supply step is a step of supplying hydrogen when forming a boundary between layers. The hydrogen gas supply step is preferably performed when at least one boundary is formed. The interruption process and the hydrogen gas supply process do not have to be performed at the same time. In the hydrogen gas supply step, H ₂ gas is supplied toward the substrate 100 in a state where crystal growth is continued. That is, the type of raw material gas is switched or the surface temperature is changed while supplying hydrogen gas. By doing so, an etching effect due to hydrogen flow can be obtained, excess atoms at the boundary can be removed, and a steep interface between layers can be obtained. Moreover, the thin layer can be grown uniformly. The amount of hydrogen gas supplied in the hydrogen gas supply step is preferably, for example, 0.5 slm or more and 10 slm or less.

The second condition is to adjust the temperature appropriately. Specifically, the growth temperature in the forming step is preferably 500 ° C. or higher and 1000 ° C. or lower, and more preferably 700 ° C. or higher and 1000 ° C. or lower. In particular, it is preferable that the growth temperature of the GaN layer 222 is higher than the growth temperature of the InGaN layer 224. The growth temperature of the InGaN layer 224 is preferably 700 ° C. or higher and 850 ° C. or lower. By keeping the growth temperature low to some extent, the uptake efficiency of In can be increased. In addition, a good crystal structure and interface can be obtained by not lowering the growth temperature too much.

The third condition is to appropriately set the V / III ratio in the raw material gas. The V / III ratio indicates the ratio of the number of supplied group V atoms to the number of supplied group III atoms. In addition, each supply number is the supply number by raw material gas. The V / III ratio in the forming step is preferably 5000 or more and 20000 or less. That is. The number of group V atoms supplied is preferably 5,000 times or more and 20,000 times or less the number of group III atoms supplied. Further, in the forming step, the number of group V atoms supplied is more preferably 6000 times or more and 17,000 times or less of the number of group III atoms supplied.

When growing InGaN, the number of In atoms supplied is preferably 0.4 times or more and 0.8 times or less, and 0.5 times or more and 0.7 times or less of the total number of Group III atoms supplied. Is more preferable. By doing so, it is possible to suppress the half width of the emission peak, increase the emission intensity, and stably emit light over the entire area.

In the forming step, the pressure in the growth chamber is preferably 100 Torr or more and 500 Torr or less.

Further, in the method for manufacturing the structure 10, thermal cleaning of the surface of the substrate 100 may be performed prior to the forming step. In thermal cleaning, for example, the surface temperature of the substrate 100 is maintained at 900 ° C. or higher and 1100 ° C. or lower for 5 minutes or longer. The thermal cleaning time can be 60 minutes or less.

Next, the operation and effect of this embodiment will be described. According to the present embodiment, when the structure 10 satisfies the conditions relating to polarization, it is possible to obtain a device that can be driven with high efficiency while suppressing the manufacturing cost of the device.

(Second Embodiment)
FIG. 5 is a diagram illustrating the configuration of the structure 10 according to the second embodiment. The structure 10 according to the first embodiment is the first embodiment except that the multilayer structure 200 includes at least one of a guide layer, a clad layer, an electron block layer, and a contact layer in addition to the quantum well structure 220. It is the same as the structure 10 according to.

In the example of this figure, the multilayer structure 200 includes an n-type clad layer 251 and an n-GaN guide layer 233, an InGaN guide layer 231 and a quantum well structure 220, an InGaN guide layer 231 and an electron block layer 240, and a p-GaN guide layer 234. , P-type clad layer 252, and p-type contact layer 260 are included in this order from the substrate 100 side. Further, the substrate 100 is n-type GaN. By using such a structure 10, a good laser element can be manufactured.

The InGaN guide layer 231 is made of InGaN, and the quantum well structure 220 is located between the two InGaN guide layers 231. Further, the n-GaN guide layer 233 is made of n-type GaN, and the p-GaN guide layer 234 is made of p-type GaN. The quantum well structure 220 is located between the n-GaN guide layer 233 and the p-GaN guide layer 234. Further, the electron block layer 240 is located between the InGaN guide layer 231 and the p-GaN guide layer 234. The electron block layer 240 is made of, for example, p-type AlGaN.

The clad layer is made of AlGaN having a composition represented by, for example, Al _y Ga _(1-y) N. Specifically, the n-type clad layer 251 is made of n-type AlGaN, and the p-type clad layer 252 is made of p-type AlGaN. Here, y is preferably 0.1 or more, and more preferably 0.15 or more. Further, y is preferably 0.25 or less. The quantum well structure 220 is located between the n-type clad layer 251 and the p-type clad layer 252. The p-type contact layer 260 is located at the end of the multilayer structure 200 opposite to the substrate 100 side. The p-type contact layer 260 is made of, for example, p-type GaN.

Among the layers included in the multilayer structure 200, the layer made of an n-type group III nitride semiconductor can be formed, for example, by further supplying a doping gas containing an n-type dopant during growth. The n-type dopant is one or more selected from the group consisting of, for example, Si, Ge, and O.

Among the layers included in the multilayer structure 200, the layer made of a p-type group III nitride semiconductor can be formed, for example, by further supplying a doping gas containing a p-type dopant during growth and performing an activation treatment. The activation treatment is heat treatment or electron beam irradiation. The p-type dopant is one or more selected from the group consisting of, for example, Mg, Zn, Cd, and Be.

Among the layers included in the multilayer structure 200, the layer made of AlGaN can be formed by supplying a group III raw material gas containing Ga, a group III raw material gas containing Al, and a group V raw material gas during growth. ..

FIG. 6 is a diagram illustrating the configuration of the optical device 30 according to the second embodiment. The optical device 30 includes a structure 10, a first electrode 310, and a second electrode 320. The first electrode 310 and the second electrode 320 are electrically connected to the multilayer structure 200. In the example of this figure, the first electrode 310 is in contact with the substrate 100, and the second electrode 320 is in contact with the layer at the end of the multilayer structure 200 opposite to the substrate 100.

The optical device 30 can be manufactured by forming a first electrode 310 and a second electrode 320 on the structure 10. Specifically, the surface of the substrate 100 opposite to the multilayer structure 200 side is etched or the like as necessary to form the first electrode 310. Further, a second electrode 320 is formed on the surface of the p-type contact layer 260 opposite to the substrate 100 side. Each electrode is composed of at least one metal such as Pd, Pt, Au, and In. In addition, each electrode may have a laminated structure of a plurality of metal layers. Further, the shape may be processed by cleaving or dicing the structure 10 as needed.

The optical device 30 is, for example, a laser. Here, it is preferable that the cleavage surface, which is the side surface of the structure 10, functions as a mirror surface. By doing so, the optical device 30 can be operated as a highly efficient laser. As a result, lasers can be manufactured at low cost. As the cleavage surface used as the mirror surface, for example, the m surface is preferable.

The structures of the structure 10 and the optical device 30 according to the present embodiment are not limited to the examples of FIGS. 5 and 6, respectively. Further, the optical device 30 is not limited to the laser, and may be a wavelength conversion element, a light emitting diode, a sensor, or the like. When the optical device 30 is a light emitting device such as a laser or a light emitting diode, the emission wavelength of the optical device 30 can be set to, for example, 500 nm or more and 560 nm or less. That is, a green light emitting device can be manufactured by using the structure 10. The emission wavelength of the optical device 30 can be set by adjusting the In composition of the InGaN layer 224 and the like. The emission color of the optical device 30 is not limited to green, and may be red, blue, or the like.

Next, the operation and effect of this embodiment will be described. According to this embodiment, the same actions and effects as those of the first embodiment can be obtained. In addition, the device can be easily obtained by using the structure 10.

Hereinafter, this embodiment will be described in detail with reference to Examples. The present embodiment is not limited to the description of these examples.

In Example 1, a structure containing a single quantum well structure (SQW) was produced. In Examples 2 to 5, a structure containing a multiple quantum well structure (MQW) was prepared. Here, the In composition was changed in Examples 1 to 5. Then, the polarization characteristics of the structures of each example were evaluated.

FIG. 7 is a diagram showing the configuration of the structure according to the first embodiment, and FIG. 8 is a diagram showing the surface temperature in the forming step according to the first embodiment. Table 1 shows the manufacturing conditions of the structure according to the first embodiment.

In this embodiment, first, a GaN free-standing substrate having a square shape of 10 mm × 10 mm and having a first main surface (11-23) was prepared, and the substrate was evaluated. Then, the substrate was divided into 2 mm × 3 mm rectangular substrates and used for forming a multilayer structure.

The results of the evaluation performed on the 10 mm × 10 mm square substrate are as follows. First, the thickness of the substrate and the density of CL dark spots on the first main surface were evaluated. The results of the evaluation were as follows.
Thickness: 408 μm
CL scotoma density: 1.53 x 10 ⁶ cm ^-2

Then, the XRC (112) ω half width, the off-angle from the {11-23} plane, and the radius of curvature of the first main surface were evaluated by the method described in the first embodiment.
XRC (112) ω half width: m-axis incident measurement 138 arcsec. , C Projection axis incident measurement 66.4 arcsec.
Off angle in each axial direction from the {11-23} plane: -0.06 ° in the m-axis direction, 0.16 ° in the c projection axis direction ({11-23} plane and the angle formed by the main plane to be measured It was confirmed that it was within 10 °.)
Radius of curvature: m-axis direction -2.69m, c projection axis direction + 8.79m
The + of the radius of curvature indicates that the main surface to be measured has the radius of curvature of the crystal axis in the convex direction, and − indicates that the radius of curvature has the radius of curvature of the crystal axis in the concave direction.

The divided substrate was attached to the MOCVD apparatus, and a single quantum well structure was produced under the conditions shown in Table 1. First, the surface temperature was raised from room temperature (RT) and maintained at 980 ° C. for 20 minutes to perform thermal cleaning of the substrate surface. During the thermal cleaning, NH ₃ gas, H ₂ gas and N ₂ gas were supplied to the growth chamber at the flow rates shown in Table 1, respectively.

Next, a homoepitaxial GaN layer (HT-GaN), an InGaN layer (GaInN), and a cap-GaN layer were grown in this order on the first main surface of the substrate to obtain the structure of Example 1. The growth conditions of each layer are as shown in Table 1. In Table 1, the "atomic number ratio" is the atomic number ratio between Group V and Group III (V / III ratio) or the atomic number ratio between In and Group III (In / III ratio) contained in the raw material gas. ) Is shown. “Pressure” indicates the pressure in the growth chamber of the MOCVD apparatus.

As shown in Table 1, an interruption step of lowering the surface temperature without causing crystal growth was provided between the growth of the homoepitaxial GaN layer and the growth of the InGaN layer. Further, the growth temperature in the forming step was set in the range of 700 ° C. or higher and 1000 ° C. or lower. Then, the V / III ratio of the raw material gas to be supplied was set in the range of 6000 or more and 17,000 or less.

FIG. 9 is a diagram showing the configuration of the structure according to the second to fifth embodiments, and FIG. 10 is a diagram showing the surface temperature in the forming step according to the second to fifth embodiments. Table 2 shows the manufacturing conditions of the structures according to Examples 2 to 5. The surface temperature shown in A in this table was 830 ° C. in Example 2, 750 ° C. in Example 3, 770 ° C. in Example 4, and 800 ° C. in Example 5.

In Examples 2 to 5, the same GaN free-standing substrate as in Example 1 was divided into rectangles of about 2 mm × 3 mm and used as the substrate. Then, a multilayer structure was formed on the (11-23) surface which is the first main surface of the substrate to obtain a structure. The multilayer structure was formed separately from each other in Examples 2 to 5.

In the same manner as in Example 1, the divided substrate was attached to the MOCVD apparatus, and a multiple quantum well structure was produced under the conditions shown in Table 2. First, the surface of the substrate was thermally cleaned in the same manner as in Example 1.

Next, a homoepitaxial GaN layer (HT-GaN) was formed on the substrate, and three barrier GaN layers (barrier GaN) and an InGaN layer (GaInN) were alternately formed. Then, a cap-GaN layer was formed, and the structures of Examples 2 to 5 were obtained. In Table 2, the "atomic number ratio" is the atomic number ratio between Group V and Group III (V / III ratio) or the atomic number ratio between In and Group III (In / III ratio) contained in the raw material gas. ) Is shown.

As shown in Table 2, an interruption step was provided between the layers to prevent crystal growth. Each interruption step was within the range of 30 seconds or more and 180 seconds or less. Further, the growth temperature in the forming step was set in the range of 700 ° C. or higher and 1000 ° C. or lower. Then, the V / III ratio of the raw material gas to be supplied was set in the range of 6000 or more and 17,000 or less.

11 to 15 are diagrams showing the results of photoluminescence measurement of the structures of Examples 1 to 5 using the apparatus shown in FIG. 3, respectively. In FIGS. 11 to 14, the c-projection-axis polarization component is shown by a solid line, and the m-axis polarization component is shown by a dotted line. Photoluminescence measurement was performed at room temperature. The excitation wavelength was 325 nm.

Further, Table 3 shows the results of photoluminescence measurement of the structures according to Examples 1 to 5 with an excitation wavelength of 325 nm. Further, FIG. 16 is a graph plotting the results of photoluminescence of the structures of Examples 1 to 5. This graph is as described in the first embodiment, with the horizontal axis representing the peak wavelength λp and the vertical axis representing the polarization ratio Rp. In this graph, a part of the straight line λp = 360, the straight line λp = 560, the straight line Rp = -0.005λp + 2.2, the straight line Rp = -0.005λp + 1.4, and the straight line Rp = -0.005λp + 1.6 are shown. It is drawn together. In addition, as a comparative example, the polarization ratio of the light emitted from the single quantum well structure formed on the {11-22} plane described in Non-Patent Document 1 is plotted in this graph.

As a result of photoluminescence measurement of the structures according to Examples 1 to 5, the peak wavelength λp was in the range of 360 nm or more and 560 nm or less. In addition, the half width of the maximum peak in the range of 360 nm or more and 700 nm or less in the photoluminescence spectrum was 100 nm or less.

As can be seen from FIGS. 11 to 15, the intensity of the c-projection-axis polarization component was higher than the intensity of the m-axis polarization component in any of the structures. That is, the polarization ratio Rp was less than 0. And, as can be seen from FIG. 16, all the plots of the examples were located inside the first parallelogram described in the first embodiment, and further inside the second parallelogram. On the other hand, the plots of the comparative examples were all located above the first parallelogram. That is, the ratio of the c-projection axis polarization component of the structure according to the example was higher than the ratio of the c-projection axis polarization component of the structure according to the comparative example. Therefore, it was confirmed that when the structure according to the example was used, the gain in the cavity direction could be increased as compared with the case where the structure according to the comparative example was used. Therefore, according to the structure according to the embodiment, it is considered that a highly efficient device can be realized.

In both the examples and the comparative examples, the polarization ratio Rp tended to decrease as the emission wavelength increased.

Although the embodiments of the present invention have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than the above can be adopted.

10 Structure 30 Optical device 40 Device 100 Substrate 101 First main surface 102 Second main surface 200 Multi-layer structure 220 Quantum well structure 222 GaN layer 224 InGaN layer 231 InGaN guide layer 233 n-GaN guide layer 234 p-GaN guide layer 240 Electronic block layer 251 n-type clad layer 252 p-type clad layer 260 p-type contact layer 310 First electrode 320 Second electrode 420 Light source 421,423,424 Mirror 422 Bright line cut filter 425,431,433 Lens 432 Polarizer 434 Light receiving part 435 Receiver 500 Measurement target

Claims (17)

A group III nitride semiconductor substrate having a semi-polar surface as the first main surface,
A structure comprising a multilayer structure made of a group III nitride semiconductor laminated on the first main surface of the substrate or on the second main surface opposite to the first main surface.
The multilayer structure includes a quantum well structure.
With the axis of the c-axis projected onto the first main surface as the c-projection axis, the polarization ratio Rp of the light emitted by photoluminescence is Rp = (intensity of m-axis polarization component-c-projection-axis polarization component) / (m). It is expressed by (intensity of axially polarized light component + c intensity of projected axis polarized light component).
In a graph in which the peak wavelength λp [nm] of the maximum peak in the range of 360 nm or more and 560 nm or less in the photoluminescence spectrum is on the horizontal axis and the polarization ratio Rp is on the vertical axis, the photoluminescence of the structure having an excitation wavelength of 325 nm. The resulting plot obtained in is located inside the first parallelogram,
The first parallelogram is composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, and a straight line Rp = -0.005λp + 1.4.
A structure having a polarization ratio Rp of less than 0 obtained by photoluminescence of the structure having an excitation wavelength of 325 nm. In the structure according to claim 1,
The first main surface is a {11-2n} surface or a surface having an off angle of 10 ° or less from the {11-2n} surface.
A structure in which n is a number of 0 or more. In the structure according to claim 2,
A structure in which n = 3. In the structure according to any one of claims 1 to 3,
A structure in which an angle formed by at least one cleavage surface of the structure and the first main surface is 75 ° or more and 105 ° or less. In the structure according to any one of claims 1 to 4,
The quantum well structure is a structure having an alternating laminated structure of GaN layers and InGaN layers. In the structure according to claim 5,
The composition of the InGaN layer is represented by In _x Ga _(1-x) N.
A structure in which 0.28 ≤ x ≤ 0.5 holds. In the structure according to any one of claims 1 to 6,
A structure having a λp of 500 nm or more and 560 nm or less obtained by photoluminescence of the structure having an excitation wavelength of 325 nm. In the structure according to any one of claims 1 to 7.
A structure in which the half width of the maximum peak in the range of 360 nm or more and 700 nm or less of the photoluminescence spectrum of the structure having an excitation wavelength of 325 nm is 100 nm or less. In the structure according to any one of claims 1 to 8.
The multilayer structure includes a clad layer made of AlGaN having a composition represented by Al _y Ga _(1-y) N.
A structure in which y is 0.1 or more. The structure according to any one of claims 1 to 9 and
An optical device including a first electrode and a second electrode electrically connected to the multilayer structure. In the optical device according to claim 10,
An optical device that is a laser with the cleavage surface of the structure as a mirror surface. A method for manufacturing an optical device for forming a first electrode and a second electrode electrically connected to the multilayer structure on the structure according to any one of claims 1 to 9. It is a method of manufacturing a structure.
A group III nitride semiconductor is placed on the first main surface of a substrate of a group III nitride semiconductor having a semipolar surface as the first main surface or on the second main surface opposite to the first main surface. Includes a forming step of growing to form a multi-layer structure
The multilayer structure includes a quantum well structure.
With the axis of the c-axis projected onto the first main surface as the c-projection axis, the polarization ratio Rp of the light emitted by photoluminescence is Rp = (intensity of m-axis polarization component-c-projection-axis polarization component) / (m). It is expressed by (intensity of axially polarized light component + c intensity of projected axis polarized light component).
In a graph in which the peak wavelength λp [nm] of the maximum peak in the range of 360 nm or more and 560 nm or less in the photoluminescence spectrum is on the horizontal axis and the polarization ratio Rp is on the vertical axis, the photoluminescence of the structure having an excitation wavelength of 325 nm. The resulting plot obtained in is located inside the first parallelogram,
The first parallelogram is composed of a straight line λp = 360, a straight line λp = 560, a straight line Rp = -0.005λp + 2.2, and a straight line Rp = -0.005λp + 1.4.
A method for producing a structure having a polarization ratio Rp of less than 0 obtained by photoluminescence of the structure having an excitation wavelength of 325 nm. In the method for manufacturing a structure according to claim 13,
A method for producing a structure in which the growth temperature in the forming step is 500 ° C. or higher and 1000 ° C. or lower. In the method for manufacturing a structure according to claim 13 or 14.
The forming step is a method for manufacturing a structure, which comprises a step of interrupting growth between at least one layer. In the method for manufacturing a structure according to claim 13 or 14.
The forming step is a method for manufacturing a structure including a step of supplying hydrogen when forming at least one boundary portion between layers. In the method for manufacturing a structure according to any one of claims 13 to 16.
A method for producing a structure in which the number of Group V atoms supplied by the raw material gas in the forming step is 5,000 times or more and 20,000 times or less the number of Group III atoms supplied.

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