JP2013175536A - Light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element with a simple element structure, capable of shaping light beam and controlling its direction by single light-emitting element.SOLUTION: A light-emitting element 1 is a light-emitting element which emits light from a flat surface, and comprises: a buffer layer 4 having the flat surface; three semiconductor columnar parts 5, 6, 7 arranged above the buffer layer 4 so as to surround a predetermined region and having a diameter being larger than a wavelength of a radiation light in a free space; and light-emitting part 3 arranged in a part of region including points immediately below centers of each of three semiconductor columnar parts 5, 6, 7 below the buffer layer 4. Light emitted from light-emitting part 3 is radiated from semiconductor columnar parts 5, 6, 7, respectively. Since three semiconductor columnar parts 5, 6, 7 are arranged in the arrangement, the light-emitting element 1 can shape light beam by the interference effect of light near columnar parts, and the radiation direction of the light beam can be controlled because of a difference between the height H-δ of one semiconductor columnar part 7 and the height H of other semiconductor columnar parts 5, 6.

Description

  The present invention relates to a light emitting element, and more particularly to a light emitting element that can be used in a stereoscopic image display apparatus.

  Current stereoscopic display technology can be broadly classified into two-lens type, multi-view type, volume display type, and aerial image reproduction type. Here, the aerial image reproduction type is being developed with the aim of satisfying all four visual functions of binocular parallax, convergence, focus adjustment, and motion parallax. This aerial image reproduction type is a method that reproduces the light from the subject itself, and does not require special glasses for stereoscopic observation. This type of stereoscopic display may be able to use all of the four visual functions described above, and thus can be a human-friendly stereoscopic image display device without causing eye fatigue.

  Typical methods in this aerial image reproduction type stereoscopic display technology include holography, parallax stereogram, lenticular sheet, or integral photography (hereinafter referred to as IP). Regarding the practical application of these methods, excluding holography, it is thought that it can be realized at an early stage with a simple method that does not require coherent light. In particular, IP can express parallax information in the vertical direction in addition to the horizontal direction, enabling natural 3D display, and early development of a 3D display that does not cause fatigue to the eyes and is easy on humans. It is particularly promising as a feasible method.

  The IP display system includes a lens array in which a large number of minute lenses (element lenses) that reproduce light rays are arranged, and a display that displays a large number of images (element images) corresponding to each lens. The observer obtains partial information corresponding to the position of the observer from one element image corresponding to one element lens, and observes a stereoscopic image in which element images are arranged by the number of element lenses. In the IP display system, the resolution of the stereoscopic image is determined by the resolution of the element lens, the resolution of the element image, and the viewing distance. Further, regarding the viewing zone angle of the IP display system, the performance of the element lens is a dominant factor. Under such circumstances, in order to generate a practical stereoscopic image by the IP method, it is indispensable to increase the definition and function of the light emitting element and the optical element (for example, see Non-Patent Document 2).

  However, even if the definition of the light emitting element and the optical element is increased, an optical system using a lens has performance limits that cannot be removed in principle, such as the diffraction limit and focal length of the lens. For example, if the pixel size of the display is smaller than the minimum spot size of the element lens, image blurring occurs, so it is necessary to reduce the spot size at the same time, but in principle it is necessary to make the spot size smaller than the Abbe diffraction limit. Impossible.

  The viewing zone angle in a system using a lens is inversely proportional to the focal length of the element lens, but the focal length of the element lens cannot be made infinitely small in order to increase the viewing zone angle. Furthermore, since the viewing zone angle is proportional to the pitch of the element lens, if the pitch of the element lens is increased, the viewing zone angle can be enlarged, but the resolution deteriorates. There is a trade-off relationship between viewing zone angles.

  Although not directly related to IP display systems, in the field of light-emitting elements, LEDs (Light Emitting Diodes), which are self-emitting elements, have attracted attention in various applications because their light-emitting characteristics have advanced dramatically in recent years. Collecting. Since LEDs have good straightness of emitted light, a mechanism for diffusing them is necessary for application to lighting equipment and the like. If the technology for diffusing the emitted light of the LED further advances and the direction in which the light is emitted can be controlled, it can be applied to a display or the like.

Although it is not a display using an LED, as a related technique, for example, in Patent Document 1, by providing a beam deflection unit such as a spatial light modulation element using a liquid crystal device in front of an image display unit composed of a liquid crystal display, There is described a stereoscopic display device that displays a stereoscopic image from a plurality of two-dimensional images having different viewpoint positions by deflecting light from pixels.
Further, as a technique for controlling the direction of light extracted from an LED, Patent Document 2 discloses a light emitting device capable of adjusting the emission angle of LED light.

Japanese Patent Laid-Open No. 6-110374 JP 2008-147182 A

"Ultra-high-definition image technology and stereoscopic image technology", IEICE Journal, May 2010, Vol.93, No.5, p.372-381 Japan Association for Mechanical Systems Promotion and Japan Photonics Technology Promotion Association, “Survey Report on Formation of Spatial Image that Enables Natural Stereoscopic Viewing—Summary”, System Technology Development Survey 19-R-5, 2008 March, p.14-16

However, the light emitting device described in Patent Document 2 requires various components in order to control the direction of light extracted from the LED. In addition, when applying to a display to control the direction of each light emitting element, it is necessary to form a large number of fine light emitting elements. Further, it is extremely difficult to emit the emitted light of these fine light emitting elements in directions other than the front.
Furthermore, there is no known technology that can control the direction of light extracted from an LED having a fine structure.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a light-emitting element having a simple element structure that enables light beam shaping and direction control with a single light-emitting element. To do.

  In order to solve the above-described problem, the light emitting device according to claim 1 is provided so as to surround a predetermined region on a buffer layer having a flat surface and on the upper side of the buffer layer, and to emit light from the exit surface of the stigma. Radiating at least three semiconductor columnar portions; and a light emitting portion provided in a partial region under the buffer layer and including immediately below the center of each of the at least three semiconductor columnar portions; The height of at least one of the at least three semiconductor columnar portions is different from the height of the other columns.

  According to such a configuration, the light emitting element emits light from the light emitting portion provided below the buffer layer having a flat surface, and is emitted from each semiconductor columnar portion provided above the buffer layer having a flat surface. The light beam is shaped by the interference effect. If the height of each semiconductor columnar part is the same, the light beam is on a line that goes from the center of gravity of the plane figure of the locus connecting all the semiconductor columnar parts on the element surface in a direction perpendicular to the element surface. Will be formed. On the other hand, the light emitting device of the present invention having such a configuration propagates through the inside of at least one semiconductor columnar portion because the height of the column of at least one semiconductor columnar portion is different from the height of the columns of other semiconductor columnar portions. Thus, the phase of the light emitted from the emission surface and the light emitted from the emission surface after propagating through the other semiconductor columnar portions can be made different. Thereby, the radiation direction of the light beam formed by the interference of the respective radiation lights having different phases can be inclined from the direction perpendicular to the element surface.

  In addition, the light emitting portion is not provided uniformly below the buffer layer, but is provided in a partial region including immediately below the center of each of at least three semiconductor columnar portions provided above the buffer layer. . By appropriately setting the light emitting area of the light emitting portion and the light intake area of each corresponding semiconductor columnar portion, most of the light emitted from the light emitting portion can be incident on each semiconductor columnar portion. Therefore, it is possible to emit light having a strength sufficient for forming a light beam from the emission surface of the top of each semiconductor columnar part. Further, light emitted from the light emitting portion leaks from the element surface (particularly, the upper surface of the buffer layer) other than the light emitting surface of each light emitting portion, and is emitted from the light emitting surface of the column head of each semiconductor columnar portion. It is possible to suppress an extra interference effect between the two.

  The light-emitting element according to claim 2 is the light-emitting element according to claim 1, wherein the light-emitting portion has a cross-sectional area equal to or smaller than an area of a circumscribed circle surrounding all of the at least three semiconductor columnar portions. It was decided that it was formed.

  According to such a configuration, it is possible to prevent light emitted from the light emitting portion from leaking from the element surface (in particular, the upper surface of the buffer layer) other than the emission surface of each semiconductor columnar portion. Therefore, it is possible to suppress an extra interference effect caused by the light leaking from the element surface and the light emitted from the emission surface of each semiconductor columnar part. Thus, since the influence of the light leaking from the element surface can be suppressed to such an extent that an extra interference effect does not occur, it is possible to increase the arbitraryness of the light emission direction.

  The light-emitting device according to claim 3 is the light-emitting device according to claim 1 or 2, wherein the light-emitting portion has a cross-sectional area of the column of the at least three semiconductor columnar portions. It was decided that it was formed so that it might become more than the sum total.

  According to this configuration, most of the light emitted from the light emitting part can be incident on each semiconductor columnar part. Therefore, the intensity of light emitted from the emission surface of each semiconductor columnar portion can be increased, and the clarity of the light beam formed by the interference of these lights can be increased.

  The light-emitting element according to claim 4 is the light-emitting element according to any one of claims 1 to 3, wherein a difference in height of the columns of the semiconductor columnar portions is radiation in the semiconductor columnar portions. It is characterized by being less than or equal to half the wavelength of light.

  According to such a configuration, the light emitting element has a length difference such that the difference between the heights of the columns is dominantly affected by the difference between the position of the exit surface of at least one column and the position of the exit surface of the other columns. Therefore, the angle formed by the emitted light with respect to the direction perpendicular to the element surface can be made relatively large.

According to the present invention, the following excellent effects can be obtained.
According to the first aspect of the present invention, the light-emitting element can enable light beam shaping and direction control with a single element. The light emitting element can be easily manufactured by forming a light emitting portion having a predetermined size below the buffer layer and forming a column having a predetermined height above the buffer layer.
According to the second aspect of the present invention, the light-emitting element can effectively perform light beam shaping and direction control. In particular, the direction control of the light beam can be performed satisfactorily.
According to the third aspect of the present invention, the light emitting element can effectively perform light beam shaping and direction control. In particular, the clarity of light can be increased.
According to the invention described in claim 4, the light emitting element can effectively perform the shaping and direction control of the light beam. In particular, the direction control of the light beam can be performed efficiently.

It is a partially exploded perspective view which shows typically the structure of the light emitting element which concerns on embodiment of this invention. It is a top view which shows typically the structure of the light emitting element which concerns on embodiment of this invention. It is a conceptual diagram of the interference of light according to the height difference of the control pillar and waveguide pillar in the light emitting element which concerns on embodiment of this invention. It is a conceptual diagram for demonstrating the relationship of the dimension of the semiconductor columnar part and light emission part in the light emitting element which concerns on embodiment of this invention. In the light-emitting device according to the embodiment of the present invention, FIG. 6 is an explanatory diagram illustrating a calculation example of a beam pattern when the difference in height between the control column and the waveguide column is 0, where (a) is a perspective view; (B) shows beam patterns on the XY plane, respectively. In the light emitting device according to the embodiment of the present invention, calculation of the beam pattern in each XY plane when the width in the cross section of the light emitting portion and the height difference between the control column and the waveguide column are changed. It is explanatory drawing which shows an example. In the light emitting device according to the embodiment of the present invention, a graph showing the control angle in the light direction obtained by calculation when the width in the cross section of the light emitting section and the height difference between the control column and the waveguide column are changed. It is. It is a conceptual diagram of the IP three-dimensional display using the light emitting element which concerns on embodiment of this invention, Comprising: (a) Front view, (b) shows a perspective view.

  Hereinafter, embodiments for carrying out the light-emitting element of the present invention will be described in detail with reference to the drawings. Note that the size and positional relationship of members and the like shown in the drawings may be exaggerated for clarity of explanation.

[Outline of light emitting device structure]
As shown in FIG. 1, the light-emitting element 1 is an element that emits light having high directivity, and is a light-directional light-emitting element that emits light in a specific direction. The light emitting element 1 emits light from a flat surface, such as an LED. The light-emitting element 1 has three or more columns (semiconductor columnar portions) so as to surround a predetermined region on a flat surface, and the height of at least one semiconductor columnar portion is different from the others. It is characterized in that light is emitted from the columnar part. Hereinafter, as an example, the light emitting element 1 will be described as having three semiconductor columnar portions 5, 6, and 7 having a circular cross section, and the semiconductor columnar portion 7 is lower than the semiconductor columnar portions 5 and 6. Here, on the upper surface of the element, three semiconductor columnar portions 5, 6, and 7 arranged so as to surround a predetermined region in an annular shape are shown in FIG.

<Structure of light emitting element>
As shown in FIG. 1, the light emitting element 1 includes a semiconductor layer 2, a light emitting portion 3, a buffer layer 4, and semiconductor columnar portions 5, 6, and 7. The semiconductor layer 2 is an n-type semiconductor layer provided below the light emitting unit 3 and between a substrate (not shown). The buffer layer 4 is a p-type semiconductor layer provided on the upper side of the light emitting unit 3 and between the element surface, and has a flat surface.

<Light emitting part>
Here, the light emitting unit 3 is formed in a partial region including a portion immediately below each of the semiconductor columnar units 5 that are formed in a circular shape in cross section and provided as a set of plural pieces on the upper side of the buffer layer 4. ing. Further, the light emitting unit 3 is arranged so that the center of gravity is located coaxially with the center of gravity of the three semiconductor columnar portions 5. Details will be described later.
When the light emitting element 1 is a blue light emitting element, the light emitting unit 3 is formed as, for example, an InGaN quantum well layer.

<Semiconductor layer>
The semiconductor layer 2 may have a structure in which, for example, an n-type GaN layer and an n-type GaN / InGaN barrier layer are stacked in this order from the substrate side (not shown).
<Buffer layer>
The buffer layer 4 may have a structure in which, for example, a p-type GaN / InGaN barrier layer and a p-type GaN layer are stacked in order from the light emitting unit 3 side.

<Electrode>
Although the illustration of the electrode structure is omitted, a step is provided between the semiconductor layer 2 and the buffer layer 4 and an ohmic contact is formed in a portion drawn from the step, as in a general LED element. If an electrode can be formed by, it will not specifically limit. Moreover, a general metal electrode can be used as an electrode material.

<Semiconductor columnar part>
The semiconductor columnar parts 5, 6, 7 are formed of the same material as that of the buffer layer 4.
In addition, the semiconductor columnar portions 5, 6, and 7 have a diameter (diameter 2φ) that is about the wavelength λ ₀ or more of the light emitted from the light emitting element 1. Here, the wavelength λ ₀ indicates the wavelength of the emitted light in free space.
<Planar shape of semiconductor columnar part>
In FIG. 1 and FIG. 2, the shape of the planar figure when the semiconductor columnar portions 5, 6, 7 are projected on the element surface (upper surface) is assumed to be circular. As shown in FIGS. 1 and 2, the thicknesses of the semiconductor columnar portions 5, 6, and 7 are assumed to be equal (radius φ).

<Semiconductor columnar interval>
The semiconductor columnar portions 7, 8, 9 are arranged at equal intervals around the predetermined origin on the light extraction surface in the direction of a uniform angle β (in this case, α = 120 degrees). The interval between the semiconductor columnar portions is set in advance to such a length that light from adjacent semiconductor columnar portions can interfere. In other words, the interval between the semiconductor columnar portions is preferably equal to or less than the coherence length of the light emitting element. The coherence length of light depends on the half-value width of the emission spectrum of the light source and the center wavelength. When the light source is an LED, the length is, for example, about 10 to several tens of μm.

<Origin M of Arrangement of Multiple Semiconductor Columns>
In the example shown in FIG. 2, the predetermined origin M is a point located in a predetermined region that is annularly surrounded by three semiconductor columnar portions 5, 6, and 7 on the upper surface of the element. Further, the origin M, as shown in FIG. 2, the center O ₁ of the semiconductor pillar portion 5, the center O ₂ of the semiconductor columnar portion 6, a point equidistant from the center O ₃ Metropolitan semiconductor pillar portion 7 Yes, it is the center of gravity of the equilateral triangle having the centers O ₁ , O ₂ , and O ₃ as vertices (denoted as the origin M). Here, it is preferable that the three semiconductor columnar portions 5, 6, and 7 are arranged in an annular shape and at an equal distance. The predetermined region surrounded by the plurality of semiconductor columnar portions is specifically an inscribed circle of the plurality of semiconductor columnar portions, and the shape and size of the predetermined region is balanced with the diameter of the semiconductor columnar portion. As desired, it can be designed appropriately while taking For example, if the diameter of the semiconductor columnar portion is about several wavelengths of the emission wavelength λ ₀ , the size of the predetermined region can be set to a fraction of a wavelength to a few wavelengths.

Further, the distances ρ from the origin M to the semiconductor columnar portions 5, 6 and 7 on the lines connecting the origin M and the centers O ₁ , O ₂ and O _{3 of the} semiconductor columnar portions 5, 6 and 7 are respectively 100 nm. It has become. The distance ρ is preferably not more than the wavelength λ ₀ of the emitted light in free space, for example, about ¼ to 1 wavelength. That is, the distance ρ is preferably about 1/4 to 1 of the diameter 2φ. In particular, when the distance ρ is set to be about ¼ of the diameter 2φ, the light emitted from the emission surfaces 5a, 6a, and 7a of the semiconductor columnar portions 5, 6, and 7 is made to interfere with each other, and is sufficiently molded. Since it is possible to emit a light beam with a high intensity, this configuration is preferable.

Of the semiconductor columnar portions 5, 6, and 7, the heights of the two semiconductor columnar portions 5 and 6 are set as reference heights H, respectively. When the difference in height between the semiconductor columnar portion 7 and the other semiconductor columnar portions 5 and 6 is δ, the height of the semiconductor columnar portion 7 is (H−δ) (see FIG. 1). In the light emitting element 1 of the present embodiment, the height difference δ of the semiconductor columnar portion 7 is not more than the length of the wavelength λ ₁ of the emitted light in the semiconductor based on the experimental results described later. Here, the wavelength λ ₁ is a wavelength when light having the wavelength λ ₀ is propagated in the semiconductor (inside the semiconductor columnar portions 5, 6, 7) as an optical waveguide in free space. In general, since the dielectric constant of a semiconductor is higher than that in a vacuum (in air), the speed of light when propagating in a semiconductor is lower than the speed of propagating in air. Specifically, when the velocity of light in the atmosphere or vacuum is c and the refractive index of the semiconductor is n, the velocity in the semiconductor is given by c / n.

Therefore, the wavelength λ ₁ can be obtained by dividing the value of the wavelength λ ₀ by the refractive index n inside the semiconductor columnar parts 5, 6, 7. For example, when the semiconductor columnar portions 5, 6, and 7 are formed of LEDs in which In is added to GaN, the refractive index n of GaN is 2.6. ₁ is about 131.5 nm.
Hereinafter, the semiconductor columnar portions 5 and 6 are referred to as waveguide columns 5 and 6, and the semiconductor columnar portion 7 whose height is adjusted to be different from the semiconductor columnar portions 5 and 6 may be referred to as a control column 7. .

[Specific examples of light emitting element design]
The light emitting element 1 is, for example, an LED obtained by adding In to GaN, and the center wavelength (λ ₀ ) of the emission spectrum is 405 nm.
The thickness of the buffer layer 4 (see FIG. 1) of the light emitting element 1 was about 500 nm.
The interval between the semiconductor columnar portions 5, 6 and 7 was set to 405 nm corresponding to the wavelength λ ₀ in the free space of the emitted light.
The radius φ (see FIG. 2) of the semiconductor columnar portions 5, 6 and 7 was set to 405 nm corresponding to the wavelength λ ₀ in the free space of the emitted light.
The height H (see FIG. 3) of the waveguide pillars 5 and 6 was set to 263 nm corresponding to about two wavelengths of the wavelength λ _{1 in} the semiconductor of the emitted light.
The height (H−δ) (see FIG. 3) of the control column 7 is controlled by changing the value of δ as a height obtained by subtracting δ [nm] from 263 nm.

[Reciprocal relationship between light emitting part and semiconductor pillar part]
Hereinafter, the correlation between the dimensions of the light emitting section 3 and the dimensions of the semiconductor columnar sections 5, 6, and 7 will be described with reference to FIG.

  As described above, in the light emitting element 1, the light emitted from the light emitting portion 3 enters the semiconductor columnar portions 5, 6, 7 through the buffer layer 4, and the inside of the semiconductor columnar portions 5, 6, 7 is used as an optical waveguide. A light beam is formed by interference of light that has propagated and exited from the exit surfaces 5a, 6a, and 7a. Therefore, the intensity of the light beam formed by the interference of the light emitted from the exit surfaces 5a, 6a, 7a of the semiconductor columnar portions 5, 6, 7 is such that the light emitted from the light emitting portion 3 is the semiconductor columnar portions 5, 6, 7 Varies depending on the amount taken into the interior. When the amount of light emitted from the light emitting portion 3 is taken into the semiconductor columnar portions 5, 6, 7 is less than a certain amount, the light exits from the emission surfaces 5 a, 6 a, 7 a of the semiconductor columnar portions 5, 6, 7. Light with sufficient intensity is not emitted, and it becomes difficult to form a light beam by interference of these lights.

  On the other hand, in order to improve the arbitrary control of the direction of the light beam emitted from the exit surfaces 5a, 6a, 7a of the semiconductor columnar portions 5, 6, 7, the light emitting portion 3 emits light and the semiconductor columnar portions 5, 6, 7 are emitted. The light leaked from the element surface (the upper surface of the buffer layer 4) without being incident on the light and the light incident on the semiconductor columnar portions 5, 6, 7 and emitted from the exit surfaces 5a, 6a, 7a are excessive interference. It is necessary to suppress the cause.

  In order to achieve both of these, the relationship between the light emitting portion 3 and the semiconductor columnar portions 5, 6, 7 is established between the light emitting portion 3 and the semiconductor columnar portions 5, 6, 7 so that the relationship described below is established. It is desirable to define the dimensions.

As shown in FIG. 3, first, a planar figure drawn so as to be in contact with a part of the outer edge of the pillars of the semiconductor columnar parts 5, 6, 7 so as to surround all of the three semiconductor columnar parts 5, 6, 7. Is assumed. Here, a circular figure surrounding all of the semiconductor columnar parts 5, 6, and 7 is assumed. The center of this circle coincides with the origin M, which is the center of gravity of an equilateral triangle having vertices at the centers O ₁ , O ₂ , and O ₃ of the semiconductor columnar portions 5, 6, and 7. Here, the radius of the minimum circle surrounding all the semiconductor columnar portions 5, 6, 7 is the distance ρ from the origin M to the contact point of the semiconductor columnar portions 5, 6, 7, and the diameter of the semiconductor columnar portions 5, 6, 7. 2φ is added.

  Therefore, as shown in FIG. 3, the area of the minimum circle (hereinafter referred to as area SO) surrounding all of the semiconductor columnar portions 5, 6, and 7 and the area of the light emitting portion 3 (hereinafter referred to as area SL). And each area (henceforth referred to as area SP) of semiconductor pillar-like parts 5, 6, and 7 can be calculated by the following formulas (1) to (3), respectively.

Here, Ψ in the formula (1) is the radius of the light emitting unit 3.
At this time, it is desirable that the relationship expressed by the following formula (4) is established between the area SL of the light emitting unit 3 and the area SO of the smallest circle that surrounds all of the semiconductor columnar units 5, 6, and 7.

  Further, it is desirable that the relationship expressed by the following formula (5) is established between the area SL of the light emitting portion and the area 3SP that is the sum of the areas SP of the semiconductor columnar portions 5, 6, and 7.

  In the above formula (5), the number multiplied by the area SP varies depending on the number of semiconductor columnar portions installed.

  Therefore, when these are summarized, in order to achieve both the improvement of the clarity of the light beam and the improvement of the arbitrary control of the direction of the light beam, the following equation (6) is obtained from the above equations (4) and (5). It is desirable that the relationship shown is established.

  As shown in the formula (6), by setting the area SL of the light emitting unit 3 to be equal to or smaller than the area SO of the minimum circle surrounding all the semiconductor columnar parts 5, 6, 7, the light emitted from the light emitting unit 3 can be obtained. Leaked from the element surface (the surface of the buffer layer 4 (see FIG. 1)) other than the semiconductor columnar portions 5, 6, and 7, the emission surfaces 5a, 6a, and 7a of the semiconductor columnar portions 5, 6, and 7 (see FIG. 1) ) Can be prevented from causing an extra interference effect with the light emitted from the light source), so that it is possible to improve the light beam direction control.

  In addition, as shown in the above formula (6), the light emitting unit 3 emits light by the light emitting unit 3 by setting the area SL of the light emitting unit 3 to an area 3SP or more which is the sum of the areas SP of the semiconductor columnar units 5, 6, and 7. Most of the emitted light can enter the semiconductor columnar portions 5, 6, and 7. For this reason, it is possible to increase the intensity of light propagating through the inside of the semiconductor pillars 5, 6, and 7 and exiting from the exit surfaces 5a, 6a, and 7a (see FIG. 1). The clarity of the light beam formed by the interference can be improved.

[Principle of interference of light emitted from semiconductor columnar portion of light emitting element]
Hereinafter, the principle of interference of light emitted from the semiconductor columnar portions 5, 6, and 7 of the light emitting element 1 will be described with reference to FIG. 4 and the following mathematical expressions as appropriate. Since the semiconductor columnar portions 105 and 106 have the same height, in the explanation using FIG. 4 and the following mathematical formula, the semiconductor columnar portions 105 and 106 are emitted from the two semiconductor columnar portions 106 and the semiconductor columnar portions 107 having different heights for the sake of simplicity. An explanation will be given taking light interference as an example.

The light emitting element in FIG. 4 includes a semiconductor layer 102, a light emitting unit 103, and a buffer layer 104, similarly to the light emitting element 1. Further, assuming that the outermost surface of the element is a reference position, the height of the semiconductor columnar portion 106 is H, and the height of the semiconductor columnar portion 107 is (H−δ). Here, for explanation, the reference position is changed. That is, the position of the upper surface of the buffer layer 104 is set as the reference altitude h ₀ . Also, the position of the stigma of the exit surface 107a of the semiconductor pillar portion 107 and altitude h _1, and altitude h ₂ a position of the exit surface 106a of the stigma of a semiconductor columnar portion 106. That is, there is a relationship of h ₂ −h ₁ = δ. The interval between the two semiconductor columnar portions 106 and 107 is p. A predetermined point C on the vertical central axis located at an equal distance from the central axes of the two semiconductor columnar portions 106 and 107 is defined as an altitude h ₃ .

  In the light emitting element of FIG. 4, light from the light emitting portion 103 is branched and emitted to a high semiconductor columnar portion 106 and a low semiconductor columnar portion 107. Further, when passing through the high semiconductor columnar portion 106, it passes through a point A1 in the semiconductor columnar portion 106 and a center point A2 of the exit surface 106a of the semiconductor columnar portion 106 as one optical path (hereinafter referred to as optical path A). Assume an optical path reaching point C. Further, an optical path reaching the point C via the center point B1 of the emission surface 106a of the semiconductor columnar part 106 and the point B2 positioned higher than the point B1 by δ when passing through the low semiconductor columnar part 107 is assumed.

And light passing through the light and the optical path B passing through the optical path A remains Since the same phase to advanced h ₁ advances the same medium (buffer layer 104) by the same distance. When the phase of the time the initial phase theta _0, the phase in the optical path A point A1 is theta _0, the phase in the optical path point B1 B, is theta _0.

The light passing through the optical path A and the light passing through the optical path B travel through different media from the height h ₁ to the height h ₂ . At this time, in the optical path A, the medium is the semiconductor columnar portion 106 (semiconductor), and in the optical path B, the medium is air. As described above, when the speed of light in the atmosphere or vacuum is c and the refractive index of the semiconductor is n, the speed in the semiconductor is given by c / n (for example, n = 2.6 for GaN, for example). ). For this reason, when the light generated in the semiconductor element is branched into two, one is emitted as it is in the atmosphere (or in a vacuum), and the other is propagated in the semiconductor and then emitted. When they meet after two lights are emitted, the optical paths are different, so the phases of the light are different. Therefore, if the wavelength in the free space of light from the light emitting element of FIG. 4 is λ ₀ and the phase advances by α in the semiconductor in the section from the height h ₁ to the height h ₂ in the optical path A, the point of the optical path A In A2, the phase is expressed by the following formula (7).

Further, assuming that the phase advances by β in the free space from the height h ₁ to the height h _{2 in} the optical path B, the phase in the optical path B is represented by the following formula (7) at the point B2.

Furthermore, since it is free space from altitude h ₂ to altitude h ₃ , the light passing through the optical path A and the light passing through the optical path B travel on the same medium (free space). At this time, the distance from the point A2 to the point C on the optical path A and the distance from the point B2 to the point C on the optical path B are the same. Therefore, the difference between the phase at the point A2 of the light passing through the optical path A and the phase at the point B2 of the light passing through the optical path B is also preserved at the point C. This phase difference τ is expressed by Equation (9). That is, the phase difference τ between the optical path A and the optical path B can be controlled by the height difference δ between the semiconductor columnar section 106 and the semiconductor columnar section 107. When Expression (9) is transformed, the height difference δ is expressed by Expression (10).

  Since the light passing through the semiconductor columnar portion 106 is delayed as compared with the light passing through the semiconductor columnar portion 107, when both are mixed, a wave having a completely different wavefront from the wavefront of the two lights is generated. . That is, the wavefronts of the light emitted from the semiconductor columnar portions 106 and 107 interfere with each other, and in a direction (direction) determined by the relative positions (positions of the three-dimensional space) of these two semiconductor columnar portions 106 and 107. The light will be emitted.

Next, interference of light emitted from the semiconductor columnar portion 106 as the wave source at the position r ₁ in the three-dimensional space and the semiconductor columnar portion 107 as the wave source at the position r ₂ in the three-dimensional space will be described.
The intensity I (r) of light formed at the time t in the position r in the three-dimensional space by the light emitted from the wave source at the position r ₁ and the wave source at the position r ₂ is expressed by the following equation (11). ).

In Expression (11), since there is a third term representing the interference of light, the light emitted from the light emitting unit 103 is superimposed after being emitted from the two wave sources, and the wave front is changed to advance the wave. The direction can be changed. In equation (11), the real part of γ in equation (12) is used. E ^{* in the} formula (12) indicates a complex conjugate of E. As shown in Equation (12), γ takes a value from 0 to 1, and indicates how much the light emitted from the two wave sources is correlated in time and space. Therefore, γ can be divided into cases as shown in the following equations (13) to (15).

  The case of Equation (13) is called fully coherent, the case of Equation (14) is called incoherent, and the case of Equation (15) is called partial coherent. Here, since the light source of LED is used as a light emitting element, it is partially coherent. Therefore, in the light emitting element of FIG. 4, the contribution of the third term of the formula (11) is large in the light intensity, so that the light traveling direction is greatly bent.

  When the horizontal interval p between the semiconductor columnar portions 106 and 107 is very small, the height difference δ of the semiconductor columnar portions becomes a dominant factor.

  In FIG. 4, for the sake of simplicity, the direction of the light beam due to the interference of light emitted from two semiconductor columnar portions having different heights has been described. The formula (11) can be extended also when there are three semiconductor columnar portions as wave sources. For example, the above formula (11) is applied using a combination of the first semiconductor columnar part 105 and the second semiconductor columnar part 106 as two wave sources, and the second semiconductor columnar part 106 and the third semiconductor columnar part 107 The above formula (11) is applied using the combination of the two semiconductors as the two wave sources, and the above formula (11) is applied using the combination of the third semiconductor columnar section 107 and the first semiconductor columnar section 105 as the two wave sources. By adding the two combinations, the relational expression for the case where there are three semiconductor columnar portions as wave sources can be obtained. Below, the simulation performed regarding shaping | molding of the light ray in the case of having three semiconductor columnar parts like the light emitting element 1 of this embodiment, and the direction control of a light ray is demonstrated sequentially.

[Performance of light emitting element]
In order to confirm the performance of the light-emitting element 1 of the present embodiment, a simulation by a FDTD (Finit-Difference Time Domain) method was performed. Prior to the description of the simulation result, an example of the calculation result of the beam pattern by the simulation by the FDTD method will be described.

(Beam pattern)
As an example of the calculation result of the beam pattern, in the arrangement of the three semiconductor columnar portions 5, 6, and 7 as shown in FIG. 2, the simulation is performed when the heights of the semiconductor columnar portions 5, 6, and 7 are equal (δ = 0). The results are shown in FIG. Specifically, as shown in FIG. 5A, the light-emitting elements 1 in which the heights of the three semiconductor columnar portions 5, 6, and 7 are made equal are arranged in an XYZ-axis three-dimensional space.

FIG. 5B shows an integrated value of the light intensity on the XY plane as the radiation pattern of the light emitting element 1 as a beam pattern on the XY plane. In this beam pattern, the area denoted by reference numeral r represents the red area in the case of color display in FIG. 5B, and is red on the scale shown in FIG. 5B, that is, the light intensity is about 0.1 W. / M ² . Here, the power density obtained by taking the square of the electric field in the FDTD method was used as the light intensity.

The area indicated by the symbol y indicates the yellow area in the case of color display in FIG. 5B, and is yellow on the scale shown in FIG. 5B, that is, the light intensity is approximately 0.07 W / m ^2. Indicates that
The area indicated by the symbol g indicates the green area in the color display shown in FIG. 5B, and is green on the scale shown in FIG. 5B, that is, the light intensity is about 0.05 W / m ² . It shows that.
The area denoted by reference numeral b represents the blue area in the color display of FIG. 5B, and is blue on the scale shown in FIG. 5B, that is, the light intensity is approximately 0 W / m ^2. Show.
The region denoted by reference symbol r represents a region with much light reaching 8000 nm above the device surface, and the region denoted by symbol b represents a region where light does not reach 8000 nm above the device surface.
Assuming that the light beam passes through the central point of the light intensity distribution, the central point of the light intensity distribution appears on the origin, so that it was confirmed that the light beam can be formed on a line extending in a direction perpendicular to the element surface.

  Next, in the light-emitting element 1 according to the present embodiment, the simulation result by the FDTD method using the dimension of the radius Ψ of the light-emitting portion 3 and the height difference δ of the semiconductor columnar portions 5, 6 and 7 as parameters is shown in FIG. 7 and FIG. 1 as appropriate.

Here, the radius Ψ of the light emitting portion 3 is changed between 1.4λ _{0 and} 2.6λ ₀ , and the height difference δ of the semiconductor columnar portions 5, 6, 7 is changed within the range of 0 to λ _1. Each simulation was performed, and the results are shown in the table shown in FIG. As a simulation condition, a square region (size: 4000 nm × 4000 nm) having a plane parallel to the surface (upper surface) of the light emitting element 1 was assumed. In addition, a region from the light emitting region to 8000 nm above the element surface was set as a calculation target. Here, the height of the high semiconductor columnar portions 5 and 6 (waveguide columns 5 and 6) from the element surface is 263 nm.
In the evaluation of the light direction, the point where the electric field intensity is maximum at the upper end of the calculation region is the center of the light beam, and the angle formed with the normal of the surface of the light emitting element 1 is the control angle θ in the light direction.

In the table shown in FIG. 6, each column represents the height difference δ between the waveguide columns 5 and 6 and the control column 7, and the length (2λ ₁ ) of two wavelengths of the emission wavelength λ _{1 in} the semiconductor. As shown. Each row indicates the control angle θ in the light ray direction obtained by calculation.
Further, the image in the table of FIG. 6 is a beam pattern showing a locus (wavefront) of light emitted from the light emitting element 1 in the XY plane. The control angle θ at this time reflects the size of the radius Ψ of the light emitting part 3 and the height difference δ of the semiconductor columnar parts 5, 6, 7. Moreover, in the table | surface shown in FIG. 6, it becomes the comparative example 1, Example 1, Example 2, and the comparative example 2 from the top to the bottom. As described above, the radius φ of the semiconductor columnar portions 5, 6 and 7 is equal to λ ₀ which is the emission wavelength in free space, and the distance ρ is ¼ of the radius φ.

Further, the radius φ and distance ρ of the semiconductor columnar portions 5, 6 and 7 in the formula (2) and the radius r _{SO of the} circle surrounding all the semiconductor columnar portions 5, 6 and 7 in the formula (3) (see FIG. 4). Can all be expressed in terms of the emission wavelength λ ₀ in free space. In the following, in conformity with the expression of the radius Ψ of the light emitting unit 3 in the expression (1) by the light emission wavelength λ ₀ , in the expression (2), the radius φ = λ ₀ and the distance ρ≈4 / λ ₀ are replaced. In (3), the radius r _SO ≈ (2 + 1/4) λ ₀ is substituted for calculation. Further, the height difference δ between the waveguide pillars 5 and 6 and the control pillar 7 is equal to the height H of the reference waveguide pillars 5 and 6 (263 nm [2λ ₁ ]). It is determined by multiplying by a numerical value.

[In the case of Comparative Example 1]
In Comparative Example 1, and the 1.4Ramuda ₀ radius Ψ of the light emitting portion 3. Here, when the radius Ψ is 1.4λ ₀ , the area SL of the light emitting unit 3 is SL = 1.96λ ₀ ² from the above-described equation (3). On the other hand, each area SP of the semiconductor columnar portions 5, 6, 7 is λ ₀ ^{2 according} to the above-described equation (3), and thus the total sum of the areas SP is area 3SP = 3λ ₀ ² . Therefore, a relationship of SL <3SP is established between the area SL and the area 3SP. Therefore, the comparative example 1 does not satisfy the condition of the above-described formula (6).

  In this case, as shown in the graph of FIG. 6, when the height difference δ of the semiconductor columnar portions 5, 6, 7 is 0.0H to 0.2H, the light emitted from the light emitting portion 3 is emitted from the semiconductor columnar portions 5, 5. As a result, the intensity of the light emitted from each of the exit surfaces 5a, 6a, and 7a is reduced, and therefore the intensity of the central portion of the shaped light beam is reduced. . Therefore, it was confirmed that Comparative Example 1 that does not satisfy the condition of the above-described formula (6) has low light clarity.

[In the case of Example 1]
In Example 1, and the 1.8Ramuda ₀ radius Ψ of the light emitting portion 3. Here, when the radius Ψ is 1.8λ ₀ , the area SL is SL = 3.24λ ₀ ² from the above-described equation (3). On the other hand, each area SP of the semiconductor columnar portions 5, 6, 7 is λ ₀ ^{2 according} to the above-described equation (3), and thus the total sum of the areas SP is area 3SP = 3λ ₀ ² . Therefore, the relationship SL≈3SP is established between the area SL and the area 3SP. Therefore, Example 1 satisfies the condition of the above-described formula (6).

In this case, as shown in the graph of FIG. 6, when the height difference δ of the semiconductor columnar portions 5, 6, 7 is 0.0H to 0.3H, the exit surfaces 5 a of the semiconductor columnar portions 5, 6, 7 are formed. It can be seen that a light beam having a high intensity at the central portion is formed by interference of light emitted from 6a and 7a. Further, as the height difference δ increases, the position of the central portion of the light beam changes. Specifically, the control angle θ increases.
Therefore, it was confirmed that Example 1 satisfying the condition of the above-described formula (6) can improve the clarity of the light beam and can improve the arbitrary control of the direction of the light beam.

[In the case of Example 2]
In Example 2, and the 2.2Ramuda ₀ radius Ψ of the light emitting portion 3. Here, when the radius Ψ is 2.2λ ₀ , the area SL of the light emitting unit 3 is SL = 4.84λ ₀ ² from the above-described formula (3). On the other hand, the area SO of the smallest circle surrounding all the semiconductor columnar portions 5, 6, and 7 is SO = (2 + 1/4) ² λ ₀ ² ≈5λ ₀ ² from the above-described equation (3).
Therefore, the relationship SL≈SO is established between the area SL and the area SO. Therefore, Example 2 satisfies the condition of the above-described formula (6).

In this case, as shown in the graph of FIG. 6, when the height difference δ of the semiconductor columnar portions 5, 6, 7 is 0.0H to 0.4H, the emission surfaces 5 a, Due to the interference of the light emitted from 6a and 7a, a light beam having a high intensity at the central portion is formed. Further, as the height difference δ increases, the position of the central portion of the light beam changes, specifically, the light beam inclination angle θ increases.
Therefore, according to Example 2, it was confirmed that the clarity of the light beam can be improved and the arbitrary control of the light beam direction can be improved.

[In the case of Comparative Example 2]
In Comparative Example 2, the radius Ψ of the light emitting unit 3 is 2.6λ ₀ . Here, when the radius Ψ of the light emitting unit 3 is 2.6λ ₀ , the area SL of the circle when the light emitting unit 3 is orthogonally projected onto the buffer layer 4 is calculated by the area SL = 5.66λ from the above equation (3). ₀ ² On the other hand, the area SO of the minimum circle surrounding all the semiconductor columnar portions 5, 6, and 7 is the area SO = (2 + 1/4) ² λ ² ≈5λ ₀ ² from the above-described equation (3). Therefore, the relationship SL> SO is established between the area SL and the area SO. Therefore, Example 2 does not satisfy the condition of the above-described formula (6).

  In this case, as shown in the graph of FIG. 6, when the height difference δ of the semiconductor columnar portions 5, 6, 7 is 0.0H to 0.4H, the emission surfaces 5 a, A light beam having a high intensity at the central portion is formed by interference of light emitted from 6a and 7a, but the position of the central portion of the light beam can be obtained even if the height difference δ is changed from 0.0H to 0.4H. There has been little change. Therefore, according to Comparative Example 2, it was confirmed that the arbitrary control of the direction of the light beam was low.

In addition, as shown in the graph of FIG. 6, in common with Examples 1 and 2 and Comparative Examples 1 and 2, when the height difference δ of the semiconductor columnar portions 5, 6 and 7 becomes larger than a certain level, the side lobes are reduced. It becomes large and it becomes impossible to form a light beam. Specifically, in Comparative Example 1, when the height difference δ is larger than 0.3H, in Example 1, when the height difference δ is larger than 0.4H, in Example 2 and Comparative Example 2, When the height difference δ was larger than 0.5H, the result was that the beam could not be shaped. Therefore, in order to satisfactorily control the direction of the light beam, in Examples 1 and 2, the height difference between the waveguide pillars 5 and 6 and the control pillar 7 is the largest, and the emission wavelength λ ₁ (δ = 0.5H) or less, and more preferably, the height difference δ is set to be about 0.3H.

The direction control in the simulation described above can also be confirmed by the graph shown in FIG.
The graph shown in FIG. 7 shows the result of simulation by changing the value of the radius Ψ of the light emitting unit 3 from 1.4λ _{0 to} 2.8λ ₀ . In FIG. 7, as Example 3, a simulation result in the case where the value of the radius Ψ of the light emitting unit 3 is 2.0λ ₀ is added. As Comparative Examples 3 to 5, simulation results were added for the case where the value of the radius Ψ of the light emitting unit 3 was 1.6λ ₀ , 2.4λ ₀ , and 2.8λ ₀ .
In FIG. 7, as described in FIG. 6, when the height difference δ of the semiconductor columnar parts 5, 6, and 7 is 0.4 H or more, the result that the shaping of the light beam becomes difficult is obtained. Therefore, FIG. 7 mainly shows the simulation results when the value of the height difference δ is 0.0H to 0.3H. In the graph shown in FIG. 7, the horizontal axis indicates the height difference δ between the waveguide columns 5 and 6 and the control column 7 in units of the length of the emission wavelength λ ₁ in the semiconductor. The vertical axis represents the control angle θ in the light ray direction obtained by calculation.

  As shown in the graph of FIG. 7, it can be seen that the dimension of the radius Ψ of the light emitting unit 3 and the control angle θ are inversely proportional. That is, as the dimension of the radius Ψ of the light emitting unit 3 is smaller, the control angle θ is larger and the light beam is more easily inclined with respect to the normal line of the surface of the light emitting element 1. On the other hand, it can be seen that the greater the dimension of the radius Ψ of the light emitting unit 3, the smaller the control angle θ and the more difficult it is to tilt the light beam with respect to the normal of the surface of the light emitting element 1.

Here, as described above, the dimension of the radius Ψ of the light emitting unit 3 that satisfies the condition of the above-described formula (6) is 1.8λ ₀ ≦ Ψ ≦ 2.2λ ₀ .
If the radius Ψ of the light emitting portion 3 is 1.8λ ₀ (Example 1), as shown in the graph of FIG. 7, as the difference in height between Shirubehahashira 5,6 and the control column 7 [delta] increases It can be seen that the control angle θ is increased. The maximum value of the control angle θ is about 9 degrees when the height difference δ is 0.3H. That is, by changing the height difference δ from 0.0H to 0.3H, the control angle θ can be changed from 0 degree to a maximum of about 9 degrees. Therefore, according to Example 1, it turns out that the direction control of a light beam can be performed favorably.

If the radius Ψ of the light emitting portion 3 is 2.0Ramuda _0, as shown in the graph of FIG. 7, large control angle θ is as the difference in height between Shirubehahashira 5,6 and the control column 7 [delta] increases You can see that The maximum value of the control angle θ is about 8 degrees when the height difference δ is 0.3H. That is, by changing the height difference δ from 0.0H to 0.3H, the control angle θ can be changed from 0 degree to a maximum of about 8 degrees. Therefore, according to Example 2, it turns out that the direction control of a light beam can be performed favorably.

If the radius Ψ of the light emitting portion 3 is 2.2λ ₀ (Example 2), as shown in the graph of FIG. 7, as the difference in height between Shirubehahashira 5,6 and the control column 7 [delta] increases It can be seen that the control angle θ is increased. The maximum value of the control angle θ is about 7 degrees when the height difference δ is 0.3H. That is, the control angle θ can be changed from 0 degree to a maximum of about 7 degrees by changing the height difference δ from 0.0H to 0.3H. Therefore, according to Example 2, it turns out that the direction control of a light beam can be performed favorably.
As described above, when the dimension of the radius Ψ of the light emitting unit 3 is in the range of 1.8λ ₀ ≦ Ψ ≦ 2.2λ ₀ , the light beam can be sufficiently tilted with respect to the normal line of the surface of the light emitting element 1. The light emitting device 1 according to this embodiment is suitable for an IP stereoscopic display and the like.

[Application examples of light-emitting elements]
As shown in FIGS. 8A and 8B, by arranging a large number of light emitting elements 1 on a substrate 11, it is possible to provide an IP 3D display 10 that is an IP display. Although illustration is omitted, it is possible to display (reproduce) a solid by having an IP stereoscopic photographing apparatus corresponding to the IP stereoscopic display 10 photograph a subject such as a cylinder or a cube shown in FIG. ). As a result, as shown in FIG. 8B, each light emitting element 1 of the IP stereoscopic display 10 projects the element images onto the space, and these are integrated to form a reproduced image (stereoscopic image) of the subject, for example, a cylinder. Or a cube is displayed.

  As shown in FIG. 8A, the IP stereoscopic display 10 has the light emitting elements 1 arranged in the rightmost column facing the screen on the side on which two semiconductor columnar portions are arranged (waveguide pillars 5, 5). 6 side) is directed to the right side of the screen, and the side where one semiconductor columnar portion is disposed (control column 7 side) is directed to the left side of the screen. This is an arrangement in which the light-emitting element 1 on the right side toward the screen is intended to tilt the light beam from the normal direction of the element surface toward the left side in FIG. Here, in each of the light emitting elements 1 corresponding to the pixels, the difference in height is determined for each pixel, and is set so as to define the direction of the light beam emitted from the pixel. In FIG. 8B, for example, a thick arrow whose end point is a cylinder or a cube indicates the direction of the light beam.

  Further, in the IP stereoscopic display 10, the light emitting elements 1 arranged in the leftmost column facing the screen and the light emitting elements arranged in the rightmost column facing the screen have semiconductor columnar portions arranged. It is symmetrical. This is an arrangement intended to tilt the light beam from the normal direction of the element surface toward the right side in FIG.

In the IP stereoscopic display 10, the light emitting elements 1 arranged in the uppermost row toward the screen and the light emitting elements arranged in the lowermost row toward the screen are arranged in a semiconductor columnar portion. Is symmetric. This arrangement is also for the same reason. Furthermore, the light emitting elements 1 arranged in other screen areas are also arranged in accordance with the location.
Therefore, intensity modulation can be performed in the pixel by the light emitted from each of the three wave sources in the pixel structure of the element unit (light emitting element 1). Depending on the position of the pixel, there is a position where the heights of the semiconductor pillars 5, 6, and 7 should be made equal in order to set the control angle θ = 0 degree.

On the other hand, since the light source (light emitting unit 3) is different between the light emitting elements 1 of the three-dimensional display 10, that is, between pixels, there is no correlation in terms of light emission intensity. Therefore, the intensity of the light to be molded is simply an addition of the intensity of each light emitted from the three pixels. In other words, the intensity of the light formed between the pixels is obtained by an operation corresponding to the first term and the second term of the equation (11) when the three pixels are regarded as three wave sources.
As described above, the three-dimensional display 10 has a specific light emitting element 1 from each light emitting element 1 without passing through an optical lens by individually determining the direction (direction) in which the light emitting elements 1 constituting each pixel are emitted. Light having directivity in the direction (direction) can be emitted.

  A display element (FPD) in which a large number of light emitting elements 1 having such a fine structure are arranged has the same function as an apparatus in which a lens plate and a light emitting surface are joined in the prior art. In the IP stereoscopic display 10 created in this way, the resolution of the stereoscopic display depends only on the definition of the light-emitting element 1, and video blur due to insufficient resolution of the optical system does not occur. Further, the viewing zone angle in the IP display using the light emitting element 1 depends only on the maximum value of the angle (control angle θ) formed by the radiated light with respect to the direction perpendicular to the element surface, and the resolution and the viewing zone angle are independent. It is possible to improve.

[Possibility of using light emitting elements]
The light-emitting element 1 can be applied to general devices that require light beam shaping and direction control. For example, it is suitable for a light source for a projector, a connector used for spatial light interconnection, an illumination light source that does not require a diffuser.

[Method for Manufacturing Light-Emitting Element]
As a method for manufacturing the light-emitting element 1, various known fine processing techniques can be used. The light-emitting element 1 can be prepared by preparing a light-emitting element having a flat radiation surface such as an LED and finely processing the surface.

  An example of the manufacturing process of the light-emitting element 1 is as follows. First, a semiconductor substrate such as GaAs or Si is formed on a semiconductor substrate such as a molecular beam epitaxy (MBE) method or a metal organic chemical vapor deposition (MOCVD) method. The semiconductor layer 2, the light emitting portion 3, and the buffer layer 4 are stacked by a film method.

Here, for the light emitting unit 3, the material of the light emitting unit 3 is formed on the semiconductor layer 2 with a thickness equal to or greater than the thickness of the light emitting unit 3. Then, a region where the light emitting unit 3 is formed is masked. Then, the light emitting portion 3 is formed by performing dry etching such as reactive ion etching (RIE) or wet etching using a chemical solution from above the mask.
Alternatively, the light emitting unit 3 may be formed by depositing a material of the light emitting unit 3 on the semiconductor layer 2 and patterning a portion other than the portion that becomes the light emitting unit 3.
Alternatively, a part of the region may function as the light emitting unit 3 by forming a material of the light emitting unit 3 on the semiconductor layer 2 and exciting the material locally using, for example, laser light.

  The buffer layer 4 is first formed with a thickness equal to or greater than the uppermost portions of the semiconductor columnar portions 5, 6, 7 (the exit surfaces 5 a, 6 a of the waveguide columns 5, 6). Then, a region for forming the semiconductor columnar parts 5, 6, and 7 is masked. Then, semiconductor columnar portions 5, 6, and 7 are formed by performing etching on the mask based on the various etching methods described above.

  Moreover, you may form the light emitting element 1 as follows. First, the semiconductor layer 2 and the light emitting portion 3 are formed on a semiconductor substrate such as GaAs or Si by a film forming method such as a molecular beam epitaxy (MBE) method or a metal organic chemical vapor deposition (MOCVD) method. The buffer layer 4 is stacked. Then, on the buffer layer 4, a dielectric reflection film having one window formed in a partial region with a size including a position immediately below the center of each of the semiconductor columnar portions 5 is formed. On the other hand, a transparent dielectric substrate having the semiconductor columnar portions 5 disposed on the surface is separately formed. Then, the surface opposite to the surface on which the plurality of semiconductor columnar portions 5 of the transparent dielectric substrate are provided is attached to the surface on which the dielectric reflection film of the buffer layer 4 is provided by a bonding method or the like. At this time, it is assumed that the windows provided in the dielectric reflection film are aligned and pasted so as to be disposed in a partial region including a portion immediately below the center of each of the semiconductor columnar portions 5 of the transparent dielectric substrate.

  In the present embodiment, since the light emitting unit 3 is provided in a partial region of the lower surface of the buffer layer 6, the portion where the light emitting unit 3 is provided and the other portions are thicker by the thickness of the light emitting unit 3. A difference arises. However, since the light emitting portion 3 is extremely thin (about 3 to 10 nm) as described above, there is almost no gap due to the difference in thickness. Absent. Further, according to the method for controlling the position of implanting impurities (In ions) as described above, the height of the interface becomes equal, so that no gap itself is generated.

  As described above, the light emitting device 1 according to the embodiment of the present invention forms light beams by the mutual interference effect of the light emitted from the semiconductor columnar portions by forming three or more semiconductor columnar portions on the surface. Can be molded. In addition, the light emitting element 1 can shape a light beam radiated in an arbitrary direction other than the vertical direction from the element surface by appropriately selecting the height of the control column 7 and breaking the balance of the column heights. It becomes possible. Further, the light emitting element 1 has a simple structure because the direction of the light beam can be controlled only by forming the semiconductor columnar parts 5, 6, and 7 on the surface.

As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to this. For example, although the material of the LED element has been described as being GaN, the present invention is not limited to this, and may be AlN, GaAlN, ZnO, GaAs, GaP, GaAlAs, GaAlAsP, or the like.
The light emitting element is not limited to an injection type EL element such as an LED element, and may be an intrinsic EL element such as an organic EL element or an inorganic EL element.

Hereinafter, the modification about the semiconductor columnar part of a light emitting element is enumerated.
The cross-sectional shape of the semiconductor columnar portion is not limited to the illustrated circle, and may be a polygon or the like. In addition, the number of semiconductor columnar portions is three, but may be four or more. When the number of semiconductor columnar portions is four, one semiconductor columnar portion is a control column and another semiconductor columnar portion is a waveguide column, or two semiconductor columnar portions are control columns and other semiconductors The columnar portion is a waveguide column. The four semiconductor columnar portions are preferably arranged such that the angle α in FIG. 2 is 90 degrees.

  When the number of semiconductor columnar portions is five, one or two semiconductor columnar portions are the same control columns, and the other semiconductor columnar portions are waveguide columns. The five semiconductor columnar portions are preferably arranged such that the angle α in FIG. 2 is 72 degrees.

  When the number of semiconductor columnar portions is 6, one, two, or three semiconductor columnar portions are the same control columns, and the other semiconductor columnar portions are waveguide columns. The six semiconductor columnar portions are preferably arranged such that the angle α in FIG. 2 is 60 degrees. For example, when six semiconductor columnar portions are arranged in a ring shape, the interval may be substantially zero.

When the semiconductor columnar portion as the wave source is an integer N of 4 or more, if the number of combinations of two adjacent columns is _N C2, ₃ C ₂ (= 3) when there are three semiconductor columnar portions. It is possible to extend the equation (11) by applying and adding the equation (11) only _N C ₂ times in the same manner as applying the equation (11) times. It is.

Even if the interval between the plurality of semiconductor columnar portions arranged in a single annular shape is substantially zero, the size of the element increases in proportion to the total number of semiconductor columnar portions. The total number can be designed as appropriate.
A plurality of semiconductor columnar portions arranged in a ring shape, such as three on the inner side and six on the outer side, may be doubled.
In addition, the diameters of all the semiconductor columnar portions are not necessarily equal.

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Semiconductor layer 3 Light emitting part 4 Buffer layer 5,6 Waveguide pillar (semiconductor columnar part)
7 Control column (semiconductor column)
10 IP stereoscopic display 11 Substrate

Claims (4)

A buffer layer having a flat surface;
On the upper side of the buffer layer, at least three semiconductor columnar portions that are provided so as to surround a predetermined region and emit light from the emission surface of the stigma,
A light emitting portion provided in a partial region including a portion directly below the center of each of the at least three semiconductor columnar portions, on the lower side of the buffer layer;
A light emitting device, wherein a height of at least one of the at least three semiconductor columnar portions is different from a height of another column.   2. The light emitting device according to claim 1, wherein the light emitting portion is formed so that a cross-sectional area is equal to or smaller than a circumscribed circle surrounding all of the at least three semiconductor columnar portions.   The light-emitting portion is formed so that a cross-sectional area is equal to or greater than a sum of cross-sectional areas of columns of the at least three semiconductor columnar portions. The light emitting element of description.   The difference in height between the columns of the semiconductor columnar portions is equal to or less than half the wavelength of the emitted light inside the semiconductor columnar portions. The light emitting element as described in any one.