JPH0832111A - Semiconductor light emitting element as well as light emitting device, photodetector, optical information processor, and photocoupler utilizing the element - Google Patents

Abstract

PURPOSE:To provide a highly reliable semiconductor light emitting element having a high luminous efficiency. CONSTITUTION:An n-AlGaln lower clad layer 2, p<->-GaInP active layer 3, p- AlGaInP upper clad layer 4, lower p-AlGaAs current diffusing layer 5, high- resistance layer 6, and upper p-AlGaAs current diffusing layer 5 are successively formed on an n-GaAs substrate 1 by growing crystals. The high-resistance layer 6 is formed by temporarily changing the dopant from Zn to Mg. Therefore, the electric current injected from a p-side electrode is sufficiently diffused in the lateral direction in cross section by the layer 6 and injected to nearly all area of the active layer 3. Since the layer 6 can be formed in a thin layer, the injected current can be increased without increasing the electrical resistance of a light emitting element. Since the layer 6 is thin, in addition, a semiconductor layer having excellent crystallinity can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, a light emitting device using the semiconductor light emitting device, an optical detecting device,
The present invention relates to an optical information processing device and an optical coupling device. Specifically, a high-efficiency, high-power surface emitting semiconductor light emitting element, which is important in the field of optical communication or optical information processing, and a light emitting device using the semiconductor light emitting element, an optical detection device, and optical information. The present invention relates to a processing device and an optical coupling device.

[0002]

2. Description of the Related Art As one of semiconductor light emitting devices aiming at improvement of light emission efficiency and high light output, Japanese Laid-Open Patent Publication No.
There is one disclosed in Japanese Patent No. 171679. The cross-sectional structure of this light emitting element N is shown in FIG. The light emitting element N is n-
On the GaAs substrate 61, an n-InGaAlP lower clad layer 62, an InGaAlP active layer 63, and p-InGaAl.
P upper clad layer 64, p-GaAlAs current spreading layer 65
And a p-GaAs cap layer 66 are sequentially stacked, and a p-side electrode 67 made of Au-Zn is formed on the cap layer 66.
An n-side electrode 68 made of Au-Ge is formed on the lower surface of the n-GaAs substrate 61.

In the light emitting device N, the current injected from the p-side electrode 67 is diffused in the lateral direction of the cross section in the current diffusion layer 65 as shown by the broken line in FIG. 16, and the proportion of the current flowing directly below the p-side electrode 67 is reduced. However, the current injected into the active layer 63 corresponding to the peripheral region of the p-side electrode 67 increases. As a result, the amount of light emitted from the active layer 63 that is blocked by the p-side electrode region is reduced and the p-side electrode 67 is reduced.
The amount of light emitted from the peripheral region of the light emitting element N increases and the light emitting efficiency of the light emitting element N improves.

Here, in order to sufficiently diffuse the current injected in the current diffusion layer 65 in the lateral direction, it is necessary to make the thickness of the current diffusion layer 65 sufficiently large. However, if the thickness of the current diffusion layer 65 is increased, the resistance of the current diffusion layer 65 increases and the injection current decreases. Therefore, in the light emitting element N, the current diffusion layer 65 is made of a material having a low resistivity.

[0005]

However, even if a material having a low resistivity is used, the current spreading layer 65 having a relatively large thickness is used.
Therefore, there is a problem in that it is difficult to grow the current diffusion layer 65 having excellent crystallinity. In addition, the stress due to the difference in thermal expansion coefficient between the current diffusion layer 65 and the upper cladding layer 64 is large, and there is a problem in the reliability of the light emitting element N. Further, there is a problem that the manufacturing cost increases as the growth time of the current diffusion layer 65 increases.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object thereof is to diffuse an injection current in a lateral direction without using a thick current diffusion layer. The purpose is to solve the above problems.

[0007]

According to a first semiconductor light emitting device of the present invention, an active layer is formed above a substrate, a plurality of semiconductor layers are laminated on the active layer, and the semiconductor layer is partially formed on the semiconductor layer. A front emission type semiconductor light emitting device in which a front surface electrode is formed and a back surface electrode is formed below a substrate is characterized in that a high resistance layer is provided in the semiconductor layer between an active layer and the front surface electrode. .

At this time, the high resistance layer may be formed so as to cross a partial region of a current path between the surface electrode and the active layer. Further, it may be provided on at least the whole or a part immediately below the current injection region of the surface electrode.

In a second semiconductor light emitting device of the present invention, an active layer is formed above a substrate, a plurality of semiconductor layers are laminated on the active layer, and a surface electrode is partially formed on the semiconductor layer. In a front emission type semiconductor light emitting device having a back electrode formed below a substrate, a reverse conductive layer having a reverse conductivity type to the semiconductor layer is formed in the semiconductor layer, and voltage can be independently applied to the reverse conductive layer. It is characterized by having done.

In the above semiconductor light emitting device, a current constriction structure may be provided to limit a region where an injection current injected into the active layer flows. Further, it is preferable to provide a multilayer reflective film between the substrate and the active layer.

The first light emitting device of the present invention comprises the semiconductor light emitting element of the present invention and a lens for converting the emitted light of the semiconductor light emitting element into substantially parallel light. The light emitting device of the present invention is the semiconductor light emitting device of the present invention. It is composed of an element and a lens that focuses the emitted light of the semiconductor light emitting element.

Further, the optical information processing apparatus of the present invention comprises the light emitting device of the present invention, a scanning means for scanning the emitted light of the light emitting device, and a light receiving means.

Further, the optical coupling device of the present invention comprises the light emitting device of the present invention, a reflecting means for reflecting the light emitted from the light emitting device, and a light receiving means.

[0014]

In the first semiconductor light emitting device according to the present invention, since the high resistance layer is provided in the semiconductor layer between the active layer and the surface electrode, the current injected from the surface electrode depends on the existence of the high resistance layer. It is diffused in the lateral direction of the cross section of the semiconductor layer. As a result,
The injection current that has passed through the high resistance layer is injected over almost the entire surface of the active layer, and the light emitted in the active layer can be efficiently emitted from the top emission window around the surface electrode. Since this high resistance layer has a high resistance value, it can be sufficiently diffused laterally with a relatively thin film thickness. Therefore, the semiconductor layer can be formed without impairing the reliability of the light emitting element. Further, since the high resistance layer is thin, the electrical resistance between the front surface electrode and the back surface electrode can be small, and a large current can be injected to increase the output of the light emitting element.

At this time, if the high resistance layer is provided so as to cross a partial region of the current path between the surface electrode and the active layer,
Since the injected current flows through the region where the high resistance layer does not exist, the electric resistance between the front surface electrode and the back surface electrode can be further reduced. Therefore, a larger current is injected, and the light emission efficiency can be further improved.

Further, if the high-resistance layer is provided on at least the whole or part of the surface electrode immediately below the current injection region, the current injected from the surface electrode is prevented from flowing straight to the active layer, and the light emitting window is provided. Current can be injected into the active layer region corresponding to. Therefore, the luminous efficiency of the light emitting element can be further improved. In particular, in a light emitting device having a current confinement structure, a current can be injected into the central portion of the active layer region corresponding to the light emitting layer, so that so-called ring emission is eliminated and a uniform light emitting region is obtained. You can

In the second semiconductor light emitting device of the present invention, the reverse conductive type reverse conductive layer formed in the semiconductor layer between the active layer and the surface electrode is in a state where no voltage is applied. It acts as a high resistance layer, and the charges injected from the surface electrode are diffused in the lateral direction of the cross section and accumulated on the upper surface of the reverse conductive layer. At this time, if a voltage is applied to the reverse conductive layer, the reverse conductive layer changes to a low resistance layer, and the charges accumulated in the laterally diffused state are injected into the active layer at once. Therefore the second
Even in the light emitting device, the thin reverse conductive layer can sufficiently diffuse current in the lateral direction, and can be a light emitting device with high reliability and high light emission efficiency.

Further, since the light emitting device having the current confinement structure can inject current into the region of the active layer corresponding to the light emitting window, the light emitting efficiency can be further improved.

Further, if a multilayer reflective film is provided between the substrate and the active layer, the light emitted from the active layer to the substrate side can be reflected from the multilayer reflective film to be emitted to the outside from the surface electrode side. Moreover, the luminous efficiency can be further improved.

Further, by using these semiconductor light emitting elements in a light emitting device, an optical detection device, an optical information processing device or an optical coupling device, it is possible to increase the resolution.

[0021]

EXAMPLE FIG. 1 is a sectional structural view showing a light emitting device A which is one example of the present invention. 2 is n-AlGa
InP lower cladding layer, 3 is a p ^-- GaInP (or p ^-- AlGaInP) active layer, and 4 is a p-AlGaIn
P upper clad layer, 5 is a p-AlGaAs current diffusion layer, 6
Is a high resistance layer, and in the light emitting device A, the lower clad layer 2, the active layer 3, the upper clad layer 4 and the lower current diffusion layer 5 are crystal-grown on the GaAs substrate 1, and then the high resistance layer 6 is formed. After crystal growth of the current diffusion layer 5 and the current diffusion layer 5 on the upper side, the p ⁺ -GaAs cap layer 7 is further formed thereon. Zn, for example, is used as a dopant in these p-type semiconductor layers (from the active layer 3 to the cap layer 7), and the high resistance layer 6 temporarily changes the dopant to, for example, Mg so as to increase its resistivity. Crystal growth is performed to form a thin high resistance layer 6. The high resistance layer 6 has a higher resistance than the current diffusion layer 5, but is not an insulating layer to which a current does not flow at a normal driving voltage. Then, a p-side electrode 8 is formed on the cap layer 7, and G
An n-side electrode 9 is formed on the lower surface of the aAs substrate 1.

FIG. 2A shows how the injection current flows in the light emitting device A, which is obtained by calculation. In the high resistance layer 6, the resistivity is high and it is difficult for current to flow. As shown in FIG. 2A, the current injected from the p-side electrode 8 (broken line in the figure; the same applies hereinafter) is Due to the presence of the high resistance layer 6, the current diffusion layer 5 on the upper side is sufficiently diffused in the lateral direction of the cross section. The diffused injection current is injected into almost the entire area of the active layer 3, and light is emitted from almost the entire area of the active layer 3. Therefore, the emitted light can be efficiently extracted from the surface region where the p-side electrode 8 is not formed, that is, the light emitting window 10. On the other hand, in the conventional light emitting device N without the high resistance layer in which the current spreading layer 65 is simply formed, as shown in FIG. 2B, the same current spreading layer 65 as the light emitting device A of the present invention.
It can be seen that the injection current is not sufficiently diffused in the lateral direction when the thickness is set to. Thus, by providing the high resistance layer 6 in the current diffusion layer 5, the injected current can be sufficiently diffused in the lateral direction of the cross section, and the light emission efficiency can be improved. Further, since the injected current can be diffused without increasing the film thickness of the high resistance layer 6, the electric resistance between the p-side electrode 8 and the n-side electrode 9 does not increase, and the injection current increases. Therefore, the light output of the light emitting element A can be increased. Further, since the high resistance layer 6 and the like can be formed in a state where the crystal structure is relatively good, the reliability of the light emitting element A is not impaired.

In the light emitting device A, the high resistance layer 6 is formed by changing the dopant, but a different kind of dopant is added without changing the dopant, for example Zn.
The high resistance layer 6 may be formed by adding Mg to the dopant, or the high resistance layer 6 may be formed by reducing the doping concentration. In this way, the high resistance layer 6 can be easily formed by changing the type of dopant or adjusting the concentration during crystal growth.
The light emitting element A can be manufactured without increasing the manufacturing cost. In particular, if the dopant is changed, the injection current can be diffused by the thin high resistance layer 6, which is advantageous in that the light emitting device A can be made thin. Alternatively, the high resistance layer 6 may be formed by implanting impurity ions into the crystal-grown current diffusion layer 5, and the high resistance layer 6 may be formed using another different semiconductor material.
May be formed. The former method is preferable in that the high resistance layer 6 can be easily formed in a desired region by changing the ion implantation conditions, and the latter method is preferable in that a further thin high resistance layer 6 can be formed.
Further, by using a multiple quantum barrier structure as described below, it is possible to form a thinner high resistance layer 6.

FIG. 3 is a cross-sectional structural view of a light emitting device B according to another embodiment of the present invention, in which the high resistance layer 6 uses a multiple quantum barrier structure. The multi-quantum barrier structure is a structure in which the potential barrier is virtually enhanced by utilizing the characteristics of electron waves that are quantum mechanically reflected at the discontinuity points of the potential barrier. Are alternately laminated. At this time, an electron wave is reflected at a potential discontinuity point such as a boundary between the well layer and the barrier layer. The phase of the electron wave reflected at each reflection point changes by π each time the reflection point moves by one. When shifted by n times (n = 1, 2, 3, ...), the incident electron wave resonates and is strongly reflected. That is, if the thickness of the well layer is d ₁ , the thickness of the barrier layer is d _2, and the energy of the incident electron wave is E, then (2m ₁ ^* × (E−ΔEc)) ^1/2 × (d ₁ / h) = (2m ₂ ^* × (E−ΔEc)) ^1/2 × (d ₂ / h) = 1/4 If the materials and thicknesses of the well layer and the barrier layer are designed so as to satisfy the relationship , A multiple quantum barrier structure can be formed. Here, m ₁ ^* and m ₂ ^* are effective masses of electrons in the well layer and the barrier layer, ΔEc is the barrier potential, and h is Planck's constant. The same applies to holes in the valence band as well as electrons in the conduction band.

More specifically, in the light emitting device B, undoped Al _x Ga _1-x InP (x =
0.7) Layer 6a and undoped Al _x Ga _1-x I
The nP (x = 0.2) layers 6b are alternately laminated by 10 layers to form a multiple quantum barrier structure, and the high resistance layer 6 is formed.
The two types of semiconductor layers 6a and 6b are five atomic layers
er) are overlapped with each other to form one unit semiconductor layer,
The high resistance layer 6 is configured by repeatedly stacking 10 pairs of the unit semiconductor layers. The current injected from the p-side electrode 8 is sufficiently diffused in the lateral direction of the cross section by the high resistance layer 6 having the multiple quantum barrier structure, so that the luminous efficiency of the light emitting element B can be improved.

In the high resistance layer 6 utilizing the multiple quantum barrier structure, the high resistance layer under desired conditions can be obtained by selecting appropriate semiconductor materials and the thickness and period of the well layer and the barrier layer as described above. 6 can be easily formed,
In particular, as in the present embodiment, the semiconductor layers 6a and 6b of several atomic layers may be repeatedly laminated for about 10 pairs, which is advantageous in that a very thin high resistance layer 6 can be formed.

FIG. 4A is a sectional structural view showing a light emitting device C which is another embodiment of the present invention, in which the high resistance layer 6 is one of the current paths injected from the p-side electrode 8. It is provided in the current spreading layer 5 so as to cross the partial region.
The high resistance layer 6 is formed on the semiconductor chip 11 (GaAs substrate 1
Is formed by ion-implanting hydrogen ions into a predetermined region in layers. In this light emitting element C, as shown in FIG. 4B, the current injected from the p-side electrode 8 is diffused in the lateral direction of the cross section by the high resistance layer 6, and a part of the current is partially absorbed.
Is injected into the active layer 3 through the current spreading layer 5 not provided with. With such a structure, the injected current passes through the region where the high resistance layer 6 is not provided, so that the electric resistance between the p-side electrode 8 and the n-side electrode 9 is reduced and the active layer 3 is formed.
As a result of an increase in the injection current into the device, the light emission efficiency can be further improved. Further, by providing the high resistance layer 6 in a partial region as described above, a large amount of injection current flows on both sides of the high resistance layer 6 and the amount of light emitted from the light emitting window 10 can be increased. Further, it is also convenient in that the electric resistance between the p-side electrode 8 and the n-side electrode 9 becomes smaller than that when an insulating layer is provided.

By using such an ion implantation method, the high resistance layer 6 can be easily formed in a desired region by changing the mask shape. Therefore, it is possible to easily dispose the high resistance layer 6 in a region away from the p-side electrode 8,
As shown in the figure, if it is provided in the entire region (may be a partial region) immediately below the current injection region of the p-side electrode 8, the current injected from the p-side electrode 8 is straightened.
Is particularly advantageous because it can be prevented from flowing into the active layer 3 and current can be injected into the region of the active layer 3 corresponding to the light emitting window 10.

Further, by appropriately changing the type of implanted ions, the implantation energy intensity, the dose amount and the annealing conditions after implantation, it is possible to easily form an arbitrary high resistance layer 6.

FIG. 5 is a sectional structural view showing a light emitting device D which is still another embodiment of the present invention. In the light emitting device D, the multilayer reflective film layer 12 is provided between the n-GaAs substrate 1 and the lower cladding layer 2. The multilayer reflective film layer 12 is composed of two semiconductor layers having different refractive indices, for example, n-Al.
It has a structure in which As layers 12a and n-AlGaAs layers 12b are alternately laminated. Here, when the refractive index of the AlAs layer 12a is n ₁ , the refractive index of the AlGaAs layer 12b is n ₂ , and the central wavelength (in vacuum) of the light emitted from the active layer 3 is λ, the two semiconductor layers 12a, The film thicknesses d ₁ and d ₂ of 12b are formed such that d ₁ = λ / 4n ₁ ... D ₂ = λ / 4n ₂ .

Light emitted from the active layer 3 toward the GaAs substrate 1 is reflected by the multilayer reflective film layer 12 toward the light emitting window 10, and the light emitting efficiency can be further improved.
Further, different wavelengths lambda ₁ little by _{little, λ 2, ..., λ d} 11 = λ 1 / 4n 1, d 12 = λ 1 / 4n 2 ( 1st multilayer reflective film layer) with respect to _i d ₂₁ = λ ₂ / 4n ₁ , d ₂₂ = λ ₂ / 4n ₂ (second multilayer reflective film layer) ・ ・ ・ ・ d _i1 = λ _i / 4n ₁ , d _i2 = λ _i / 4n ₂ (i-th multilayer) By laminating several pairs of i-layered multilayer reflective film layers 12 so as to form a reflective film layer), it is possible to reflect broad light having a wavelength from λ ₁ to λ _i , and the active layer 3 emits light. The generated light having a wide wavelength can be taken out from the light emitting window 10 without any trouble. Also, obliquely incident light can be efficiently reflected.

FIG. 6A is a sectional structural view showing a light emitting device E which is still another embodiment of the present invention. The light emitting element E has a current confinement structure, and the cap layer 7 and the insulating layer 13 formed on the current diffusion layer 5 are etched to form the light emitting window 1
P-side electrode 8 provided on the entire upper surface of the insulating layer 13 by opening 0
Are brought into contact with the cap layer 7 in the inner peripheral region of the opening region.
In the light emitting element E, the current injected from the p-side electrode 8 is diffused in the lateral direction of the cross section in the high resistance layer 6 as shown in FIG. Current is injected in the region of layer 3. Conventionally, in a light emitting device having a current constriction structure, current is hardly injected into the region of the active layer 3 corresponding to the light emitting window 10, particularly in the central region, and so-called ring light emission is generated. By providing 6, the injection current can be diffused to the central region of the active layer 3 corresponding to the light emission window 10, and a uniform light emission region can be obtained, which is particularly effective. Further, like the light emitting element F shown in FIG. 7, the high resistance layer 6 may be provided in a region immediately below the current injection region of the p-type electrode so as to obstruct the current path from the p-side electrode 8. In the light emitting device F having such a structure, a larger amount of current can be injected into the region of the active layer 3 corresponding to the light emitting window 10.

FIG. 8A is a sectional structural view of a light emitting device G which is still another embodiment of the present invention, in which the cap layer 7 and p formed on the current diffusion layer 5 are formed.
The side electrode 8 is etched to open the light emitting window 10.
Further, the current diffusion layer 5 below the high resistance layer 6 has the insulating layer 13 formed in the outer peripheral region of the region corresponding to the light emitting window 10, and the inner peripheral region of the insulating layer 13 becomes the current path region. It has a current constriction structure. In this light emitting element G, the high resistance layer 6 is formed above the insulating layer 13 forming the current constriction structure, and the current injected from the p-side electrode 8 is as shown in FIG. And is diffused laterally in the cross section by the high resistance layer 6 (in this case, toward the current path),
The diffused current flows into the current path region surrounded by the insulating layer 13 and is injected in the vicinity of the region of the active layer 3 facing the light emitting window 10. As a result, the injected current outside the region corresponding to the light emitting window 10 is collected by the high resistance layer 6 in the current path region by the insulating layer 13, and the amount of current flowing through the active layer 3 increases. Therefore, the light emission amount of the light emitting element G can be further increased, and the light emission efficiency can be further enhanced.

The current constriction structure can be formed by providing the insulating layer 13 immediately below the p-side electrode 8 as in the light emitting element E or by providing the insulating layer 13 in the current diffusion layer 5 as in the light emitting element G. . The insulating layer 13 can be provided, for example, by ion-implanting hydrogen ions into the current diffusion layer 5 or the like, or by performing crystal growth while injecting a dopant. However, like the light-emitting element G, the insulating layer 13 is located below the high resistance layer 6 and is an active layer. Three
There is an advantage that the current constriction structure is formed closer to the point where the current constriction effect is greater.

Further, as shown in FIG. 9, after the semiconductor chip 14 (from the GaAs substrate 1 to the cap layer 7) is obtained by crystal growth in the same manner as the light emitting device A of the first embodiment, the light emitting window 10 is removed. In the region, the region from the cap layer 7 of the semiconductor chip 14 to the lower clad layer 2 is etched to form the mesa portion 15 under the light emitting window 10, and SiO 2 is formed in the region extending from the outer peripheral surface of the mesa portion 15 to the upper surface of the GaAs substrate 1. ₂
Alternatively, the p-side electrode 8 may be formed on the outer peripheral surface of the mesa portion 15 from above the insulating layer 13, and the p-side electrode 8 may be brought into contact with the outer periphery of the upper surface of the cap layer 7. According to the light emitting device H, the region of the semiconductor chip 14 where the current injected from the p-side electrode 8 does not flow is removed by etching, so that the current constriction effect can be maximized, and the light emitting efficiency of the light emitting device H is further improved. Can be made.

FIG. 10 is a sectional structural view showing a light emitting device I which is still another embodiment of the present invention. The light emitting device I is composed of n-AlGaInP on the n-GaAs substrate 1.
Lower cladding layer 2, p ^-- AlGaInP or p ^-- G
The aInP active layer 3, the p-AlGaInP upper cladding layer 4, and the lower p-AlGaAs current diffusion layer 5 are crystal-grown, and subsequently, the n-type reverse conductive layer 16 and the upper p-AlGa are formed.
After crystallizing the As current diffusion layer 5 and the p ⁺ -GaAs cap layer 7 sequentially to obtain the semiconductor chip 17, the cap layer 7 of the semiconductor chip 17 excluding the region where the p-side electrode 8 is formed.
And the current diffusion layer 5 on the upper side up to the reverse conductive layer 16 is partially removed. The p-type semiconductor layer (active layer 3 to cap layer 7) is formed by crystal growth while doping Zn, for example, and the dopant is changed from Zn to S.
The reverse conductive layer 16 of the reverse conductive type is formed by temporarily changing to i and growing the crystal. Upper current spreading layer 5
A gate electrode 18 is formed on the upper surface of the reverse conductive layer 16 which is exposed by removing the gate electrode 18 so that a gate voltage can be applied from the outside. In addition, the cap layer 7
A p-side electrode 8 is formed on the upper surface, and an n-side electrode 9 is formed below the GaAs substrate 1.

In this light emitting element I, the gate electrode 1
When the gate voltage is not applied to 8, the reverse conductive layer 16 and the current diffusion layer 5 thereunder are reverse biased, and the reverse conductive layer 16 functions as a high resistance layer close to the insulating layer. The current is almost not flowing. Therefore, the charges injected from the p-side electrode 8 are dammed by the reverse conductive layer 16 like a dam as shown in FIG. 11A, diffused in the lateral direction of the cross section of the current diffusion layer 5, and are reversed. Accumulates on the upper surface. After that, when a positive gate voltage is applied to the gate electrode 18, the reverse conductive layer 16 becomes a low resistance layer and becomes conductive, exhibiting the same function as the gate-on signal is applied to the thyristor, as shown in FIG. ), Charges accumulated on the upper surface of the reverse conductive layer 16 are injected into the active layer 3 all at once in a state of being diffused in the lateral direction. As a result, charges flow into the active layer 3 at a stretch, and the luminous efficiency and maximum light output of the light emitting device I can be increased.

In the light emitting device I, the reverse conductive layer 16 acts as a low resistance layer when the gate voltage is applied, so that the charges injected from the p-side electrode 8 are on the upper surface of the reverse conductive layer 16. Does not accumulate in. Therefore, the injected current flows from the p-side electrode 8 to the active layer 3 without being laterally diffused, and the current flows only in the vicinity of the active layer 3 region directly below the p-side electrode 8 as shown in FIG. 11C. Will be injected. Therefore, it is desirable to apply a pulsed voltage to the gate electrode 18 and use it as a pulsed light source.

Further, in forming the reverse conductive layer 16, not only crystal growth may be performed while doping impurities, but also ion implantation may be performed after crystal growth of the semiconductor chip 17. Ion implantation has an advantage that crystal growth can be easily performed with a single dopant. Further, the reverse conductive layer 16 can be formed by using different semiconductor materials. In this case, the reverse conductive layer 16 can be used as an etch stop layer by using an appropriate etchant, so that the reverse conductive layer 16 can be easily formed. The upper current spreading layer 5 can be removed.

Although not shown, the reverse conductive layer may be formed on a light emitting element having a current constriction structure such as the light emitting element E or the light emitting element G. In this case as well, it is needless to say that the current can be sufficiently injected into the region of the active layer 3 corresponding to the light emitting window, particularly in the central region, so that the light emitting efficiency is further enhanced and the ring light emission is eliminated. Absent.

In each of the above-mentioned embodiments, the p-type semiconductor layer (active layer 3 to cap layer 7) is used for explanation.
Of course, a light emitting element can also be formed using an n-type semiconductor layer. Further, although the high resistance layer 6 and the reverse conductive layer 16 are provided in the current diffusion layer 5, they do not necessarily have to be provided in the current diffusion layer 5, such as the upper side or the lower side of the current diffusion layer 5 and the active layer 3 and the cap layer. If it is provided in between, the current injected from the p-side electrode 8 can be diffused in the lateral direction of the cross section. Further, the effect of the high resistance layer 6 and the reverse conductive layer 16 can be further enhanced by providing the current diffusion layer 5, but
It is not always necessary to provide the current spreading layer 5. Further, the current constriction structure may be provided below the active layer 3 by providing the insulating layer 13 in the lower cladding layer 2 or the like.

As described above, according to the present invention, it is possible to provide a small-sized light emitting device which has a high luminous efficiency and a large output. In particular, a device having a current constriction structure can be used as a light emitting device having a high output and a small light emitting diameter. Therefore, by using such a light emitting element, a high-performance optical device having high resolution can be provided. A specific example will be described below.

FIG. 12 is an explanatory view showing the outline of an optical distance sensor J using the semiconductor light emitting device 21 of the present invention.
The optical distance sensor J includes a light projecting portion including a light emitting element 21 and a collimating lens 22 of the present invention, and a light receiving lens 2.
3 and a light receiving portion including the position detecting element 24.

FIG. 12 shows a case where the distance sensor J measures the unevenness q of the unevenness of the object 25. The light emitted from the semiconductor light emitting device 21 is collimated by the collimator lens 22 and then irradiated onto the object 25 to generate beam spots SP ₁ and SP _{2, which} are reflected by the beam spots SP ₁ and SP ₂ , respectively. An image is formed on the position detecting element 24. These image forming positions can be detected by the signal ratio obtained by the signal lines 26 and 27 of the position detecting element 24, and the step q is calculated from the position shift amount using the principle of triangulation.

The semiconductor light emitting device 21 of the present invention has a high output and a small light emission diameter. Since a normal light emitting diode, that is, the emission area of the light is about 350 μm square,
It is difficult to detect a long distance or highly accurate, but if the semiconductor light emitting device 21 according to the present invention is used for such a distance sensor J, long distance detection is possible, and further, the beam spot diameter is small and the resolution is improved. You can If a laser diode is used, high-precision detection can be performed over a long distance, but there is a problem in safety because a laser beam is used. On the other hand, if a light emitting diode with a high output and a small light emitting diameter having a structure like the semiconductor light emitting element 21 of the present invention is manufactured, it is possible to detect even at a long distance, and the beam spot diameter is small, and the resolution is high. Can be obtained.

FIG. 13 shows a semiconductor light emitting device 31 according to the present invention.
It is a perspective view which shows the barcode reader K using. This bar code reader K includes a semiconductor light emitting element 31, a light projecting side condenser lens 32, a rotary polygon mirror 33, a scanner motor 34 for rotating the rotary polygon mirror 33 in a certain direction at a constant speed, a constant velocity scanning lens 35, and a light receiving side. Condensing lens 36, light receiving element 37
It consists of

Thus, the light emitted from the semiconductor light emitting element 31 passes through the light projecting side condenser lens 32 and passes through the rotating polygon mirror 33.
The light is reflected by the laser beam, is scanned in the horizontal direction, is made uniform in velocity by the constant velocity scanning lens 35, is condensed on the barcode 38, and is scanned on the barcode 38. Further, the reflected light from the bar code 38 is condensed and detected on the light receiving element 37 by the light receiving side condensing lens 36, and a bar code signal is obtained.

In such a bar code reader K,
For example, a conventional surface emitting LED (light emission diameter 400 μm) is used, and a focal length f = 15 mm is 250 mm with a condenser lens.
If the light is focused on the above bar code, the beam diameter on the bar code becomes larger than about 6.7 mm due to the poor light converging property, and the bar code (generally, the minimum line width is 0 .2 mm) cannot be read at all.

On the other hand, in the bar code reader K using the semiconductor light emitting device 31 according to the present invention, since the light emitting diameter can be made as small as about 10 μm, even if the light is focused under the same conditions, the bar code reader K can be used. The beam diameter on the code can be narrowed down to the minimum line width of the barcode (less than 0.2 mm), and the barcode can be read.

FIG. 14 shows an optical coupling device,
Specifically, it is a planar arrangement type photocoupler L using the semiconductor light emitting device 41 according to the present invention as a light source. The photocoupler L includes a semiconductor light emitting element 41 and a semiconductor light receiving element 42.
Are die-bonded to the lead frames 44 and 45, respectively, and are wire-bonded to the other lead frames 43 and 46, and are sealed in the transparent epoxy resin 47 in that state. An opaque resin film 48 is formed on the surface of the. In general, many photocouplers have a shape in which a light emitting element and a light receiving element face each other, but this planar arrangement type photocoupler L is characterized in that the light emitting element 41 and the light receiving element 42 are arranged on the same plane. There is.

In the case of such a plane-arranged photocoupler L, it is easy to manufacture because it can be easily molded, but a problem is that high coupling efficiency cannot be obtained unless the emission intensity is increased. In the photocoupler L having such a shape, higher output light can be obtained by using the light emitting element 41 according to the present invention than by using the conventional semiconductor light emitting element, and thus high coupling efficiency can be obtained. Further, when the transparent epoxy resin 47 is molded into an elliptic spherical shape and the light emitting element 41 and the light receiving element 42 are arranged so as to come to the respective focal points of the elliptic spherical shape, the coupling can be efficiently performed. In this case, the light emitting element 41 according to the present invention is used. Since the emission diameter is small, higher coupling efficiency can be obtained.

FIG. 15 illustrates a projector M as an example of the light emitting device. In this projector M, a semiconductor light emitting device 51 of the present invention is die-bonded onto one lead frame 52 and wire-bonded to the other lead frame 53, and a sealing resin 5 such as a transparent epoxy resin is used.
At 4, a low pressure is cast into a predetermined shape and sealed to form a square block-shaped outer shape as a whole. On the surface of the sealing resin 54, a Fresnel type flat plate lens 55 in which a large number of annular lens units are concentrically arranged is integrally formed, and on both sides of the surface, the same height as the Fresnel type flat plate lens 55, or Fresnel. A jaw 56 that is slightly higher than the plate lens 55
And the jaw portion 56 protects the Fresnel type flat lens 55.

In the case of this projector M, the semiconductor light emitting element 51
Has a high luminous efficiency and has a minute light emitting region. Therefore, the Fresnel type flat plate lens 55 narrows the directional characteristics of light, and a strong output and a thin beam can be obtained even at a long distance. For example, a Fresnel type flat lens 55 is used, a focal length f = 4.5 mm and a lens diameter 3.5.
mm, and the diameter of the light emitting window of the semiconductor light emitting element 51 is 20 μm.
The beam diameter at a distance of 1 m is 4 mm.
It is a degree. However, a conventional light emitting diode that has been conventionally used (that is, the light emission area thereof is 350
In the case of (μm square), the diameter spreads to about 70 mm, so that a great advantage can be obtained by manufacturing the projector M using the semiconductor light emitting device 51 according to the present invention.

In the first semiconductor light emitting device according to the present invention, by providing the high resistance layer in the semiconductor layer between the active layer and the surface electrode, the cross-sectional lateral direction can be increased without increasing the film thickness. It is possible to sufficiently inject the injection current into the active layer and inject a large current into the entire region of the active layer. Therefore, a semiconductor layer having a good crystal structure can be formed, and a light-emitting element with high emission efficiency and high output can be provided without impairing reliability.

At this time, if the high resistance layer is provided so as to cross a partial region of the current path between the surface electrode and the active layer,
Since the injected current flows through the region where the high resistance layer does not exist, the electric resistance between the front surface electrode and the back surface electrode can be further reduced. Therefore, a larger current is injected, and the light emission efficiency can be further improved.

Further, if the high-resistance layer is provided on at least the whole or a part of the surface electrode immediately below the current injection region, the current injected from the surface electrode is prevented from flowing straight to the active layer, and the light emitting window is provided. Current can be injected into the active layer region corresponding to. Therefore, the luminous efficiency of the light emitting element can be further improved. In particular, in a light emitting device having a current confinement structure, a current can be injected into the central portion of the active layer region corresponding to the light emitting layer, so that so-called ring emission is eliminated and a uniform light emitting region is obtained. You can

In the second light emitting device of the present invention, the charges injected from the surface electrode by the reverse conductive type reverse conductive layer formed in the semiconductor layer between the active layer and the surface electrode are cross-sectional. Diffuses in the direction and accumulates on the upper surface of the reverse conductive layer. At this time, if a voltage is independently applied to the reverse conductive layer, the reverse conductive layer changes to a low resistance layer, and the charges accumulated in the laterally diffused state are injected into the active layer at a stroke. Therefore, the injection current can be sufficiently diffused in the cross-sectional lateral direction by the thin reverse conductive layer, and it is possible to provide a light emitting device with high luminous efficiency and high output without impairing reliability.

Further, by using a light emitting device having a current constriction structure, a current can be injected into the region of the active layer corresponding to the light emitting window, so that the light emitting efficiency can be further improved.

Further, when a multilayer reflective film is provided between the substrate and the active layer, the light emitted from the active layer to the substrate side can be reflected from the multilayer reflective film to be emitted from the surface electrode side to the outside. Further, the luminous efficiency can be further improved.

Further, by using these semiconductor light emitting elements in a light emitting device, an optical detecting device, an optical information processing device or an optical coupling device, it is possible to increase the resolution.

[Brief description of drawings]

FIG. 1 is a cross-sectional structural view showing a semiconductor light emitting device that is an embodiment of the present invention.

FIG. 2A is an explanatory diagram showing a current path of an injection current in the above semiconductor light emitting element, and FIG. 2B is an explanatory diagram showing a current path of an injection current in a conventional semiconductor light emitting element.

FIG. 3 is a sectional structural view showing a semiconductor light emitting device which is another embodiment of the present invention.

FIG. 4A is a sectional structural view showing a semiconductor light emitting device which is still another embodiment of the present invention, and FIG. 4B is an explanatory view showing a current path of an injection current in the light emitting device.

FIG. 5 is a sectional structural view showing a semiconductor light emitting element which is still another embodiment of the present invention.

FIG. 6A is a sectional structural view showing a semiconductor light emitting element which is still another embodiment of the present invention, and FIG. 6B is an explanatory view showing a current path of an injection current in the light emitting element.

FIG. 7 is a sectional structural view showing a semiconductor light emitting device which is still another embodiment of the present invention.

FIG. 8A is a sectional structural view showing a semiconductor light emitting element which is still another embodiment of the present invention, and FIG. 8B is an explanatory view showing a current path of an injection current in the light emitting element.

FIG. 9 is a sectional structural view showing a semiconductor light emitting device which is still another embodiment of the present invention.

FIG. 10 is a sectional structural view showing a semiconductor light emitting device which is still another embodiment of the present invention.

11 (a), (b) and (c) are operation explanatory views of the above light emitting element.

FIG. 12 is a schematic view showing a configuration of a distance sensor using a semiconductor light emitting device according to the present invention.

FIG. 13 is a perspective view showing a bar code reader using the semiconductor light emitting device according to the present invention.

FIG. 14 is a cross-sectional view showing a planar arrangement type photocoupler using a semiconductor light emitting device according to the present invention.

FIG. 15 is a perspective view showing a projector using a semiconductor light emitting device according to the present invention.

FIG. 16 is a cross-sectional structural diagram of a semiconductor light emitting device that is a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 GaAs substrate 3 Active layer 4 Upper clad layer 5 Current diffusion layer 6 High resistance layer 8 p-side electrode 10 Light emitting window 12 Multi-layer reflection film layer 16 Reverse conductive type reverse conductive layer 18 Gate electrode 21, 31, 41, 51 Semiconductor light emission Element 22 Collimating lens 33 Rotating polygonal mirror 42 Semiconductor light receiving element 55 Fresnel type flat lens

Claims (11)

[Claims] 1. An active layer is formed above a substrate, a plurality of semiconductor layers are stacked on the active layer, a front surface electrode is partially formed on the semiconductor layer, and a back surface electrode is formed below the substrate. In the surface emitting semiconductor light emitting device, a high resistance layer is provided in the semiconductor layer between the active layer and the surface electrode. 2. The semiconductor light emitting device according to claim 1, wherein the high resistance layer is formed so as to cross a partial region of a current path between the surface electrode and the active layer. element. 3. The semiconductor light emitting device according to claim 1, wherein the high resistance layer is provided at least in whole or in a portion directly below the current injection region of the surface electrode. 4. An active layer is formed above a substrate, a plurality of semiconductor layers are stacked on the active layer, a front surface electrode is partially formed on the semiconductor layer, and a back surface electrode is formed below the substrate. In the surface emission type semiconductor light emitting element, a semiconductor light emitting element is characterized in that a reverse conductive layer having a reverse conductivity type to the semiconductor layer is formed in the semiconductor layer, and voltage can be independently applied to the reverse conductive layer. . 5. A current confinement structure for limiting a region where an injection current injected into the active layer flows.
Alternatively, the semiconductor light emitting device according to the item 4. 6. The semiconductor light emitting device according to claim 1, wherein a multilayer reflective film is provided between the substrate and the active layer. 7. A light-emitting device comprising the semiconductor light-emitting element according to claim 1, 2, 3, 4, 5 or 6, and a lens for converting light emitted from the semiconductor light-emitting element into substantially parallel light. 8. A light emitting device comprising the semiconductor light emitting element according to claim 1, 2, 3, 4, 5 or 6, and a lens for converging light emitted from the semiconductor light emitting element. 9. An optical detection device comprising the light emitting device according to claim 7 or 8, and a light receiving means. 10. A light emitting device according to claim 7,
An optical information processing device comprising: a scanning unit that scans emitted light of the light emitting device; and a light receiving unit. 11. A light emitting device according to claim 7,
An optical coupling device comprising a reflecting means for reflecting the emitted light of the light emitting device and a light receiving means.