JPH05251737A - Light emitting device - Google Patents

Abstract

PURPOSE:To reduce the device resistance of a surface light emission type diode having a current constricting structure by impurity diffusion without reducing the light emission output. CONSTITUTION:Grown above a substrate 1 are a p-type active layer 3, a p-type upper clad layer 4, an n-type current blocking layer 5 and a p-type cap layer 6. Zn is diffused from the cap layer 6 to the upper clad layer 4 to form a p-type current passage region 9. On the upper surface of the current passage region 9, the edge line is formed irregularly, the inner peripheral edge of a light output window 12 of a p-side electrode 11 formed on the cap layer 6 is inscribed in the irregular edge line, and the outer peripheral portion of the current passage region is partially covered with the p-side electrode 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device. Specifically, the present invention relates to surface-emitting light emitting devices such as light emitting diodes (LEDs) and semiconductor laser devices.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing a conventional light emitting diode 31. This is an n-type lower clad layer 33, a p-type active layer 34, a p-type
The on-mold cladding layer 35, the n-type current blocking layer 36, and the p-type or n-type cap layer 37 are sequentially grown to form the cap layer 37.
To the upper clad layer 35, Zn is diffused in the central portion to form a p-type current passage region 38, and the current passage region 38 is formed in the central portion of the p-side electrode 39 provided on the upper surface of the cap layer 37.
Opening a light extraction window 40 larger than the upper surface of the substrate 3
The n-side electrode 41 is provided on the entire lower surface of No. 2.

However, in the light emitting diode having the current constriction structure, when a driving voltage is applied between the p-side electrode 39 and the n-side electrode 41, the current flowing from the inner peripheral edge of the p-side electrode 39 into the cap layer 37. Enters the current passage region 38 through the cap layer 37, and when current is injected into the active layer 34, the active layer 34 emits light, and the light emitted from the active layer 34 is emitted from the light extraction window 40 of the p-side electrode 39. It is emitted to the outside.

However, in such a light emitting diode 31, since a current flows from the p-side electrode 39 to the current passage region 38 through the cap layer, the cap layer 37 is formed.
There is a problem in that the sheet resistance in (1) cannot be ignored and the element resistance increases. The thickness of the cap layer 37 may be increased to reduce the sheet resistance. However, if the thickness of the cap layer 37 is increased, the crystal growth time of the cap layer 37 and the Zn diffusion time for forming the current passage region 38 are increased. However, there is a problem that the manufacturing efficiency of the light emitting diode 31 is reduced due to the increase in length.

FIG. 8 is a sectional view showing another conventional light emitting diode 51. In this light emitting diode 51, the light extraction window 40 provided in the p-side electrode 39 is made smaller than the upper surface of the current passage region 38 so that the inner peripheral portion of the p-side electrode 39 overlaps the outer peripheral portion of the current passage region 38. I have to. Light emitting diode 5 having such a structure
In No. 1, since the current flows directly from the inner peripheral edge of the p-side electrode 39 into the current passage region 38 without passing through the cap layer 37, the element resistance becomes small.

However, in this light emitting diode, since the outer peripheral portion of the current passage region 38, which is also the light emission passage, is covered by the p-side electrode 39, the light emitted through the current passage region 38 is not emitted. There is a problem that the light output of the light emitting diode is reduced because the light is shielded by the inner peripheral portion of the p-side electrode 39.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object thereof is to provide a surface-emitting type light emitting device capable of reducing device resistance without lowering light emission output. To do.

[0008]

In the light emitting device of the present invention, a current blocking layer having at least one reverse pn junction is formed above the active layer, and impurities are diffused by penetrating a part of the current blocking layer. Thus, in the light emitting element in which the current passage region is provided and the electrode provided above the current blocking layer has the light extraction window facing the upper surface of the current passage region, the edge line of the upper surface of the current passage region is uneven. It is characterized in that the electrode formed and provided above the current blocking layer is in contact with the upper surface of the current passage region over all or part of the uneven edge line.

[0009]

In the light emitting device of the present invention, the edge line on the upper surface of the current passage region is formed in a concavo-convex shape, and the electrode formed above the cap layer is crossed over the concavo-convex edge line to form the current passage region. Is in contact with the upper surface of. That is, since the outer peripheral portion of the upper surface of the current passage region is only partially covered by the electrode, the outer periphery of the upper surface of the current passage region and the inner periphery of the electrode are concentrically formed, and As compared with the conventional light emitting element in which the outer peripheral portion is entirely covered, the shadow due to the electrode becomes smaller, and the reduction in light emission output can be reduced.

Further, since the outer peripheral portion of the upper surface of the current passage region is partially in contact with the electrode, some current flows from the electrode to the current passage region, and some current flows from the electrode to the uppermost layer (for example, Flow through the cap layer) to the outer peripheral surface of the current passage region. In addition, since the edge line of the current passage region is uneven, the length of the current injection region is increased, the amount of current injected from the outer peripheral surface of the current passage region is increased, and the element resistance is reduced.

Therefore, according to the present invention, the length of the current injection region can be increased without increasing the current passage region in the shadow of the electrode as much as possible, and the device resistance can be reduced without reducing the light emission output as much as possible. be able to.

[0012]

1 is a sectional view showing a light emitting diode A according to an embodiment of the present invention. 2A to 2E are cross-sectional views showing a method for manufacturing the light emitting diode A. Less than,
The structure of the light emitting diode A will be described according to the manufacturing order. First, for example, MBE is formed on the n-GaAs substrate 1.
By (molecular beam epitaxy) growth method, n-Al _0.3 G
a _0.7 As lower clad layer 2, p-Al _0.03 Ga _0.97 As
Active layer 3, p-Al _0.3 Ga _0.7 As upper cladding layer 4, n
-Al _0.3 Ga _0.7 As current blocking layer 5, p-Al _0.1
The Ga _0.9 As cap layer 6 is sequentially grown [FIG.
(A)]. As a result, a pnpn structure is formed.

Thereafter, the film thickness is set so as to satisfy the antireflection (AR) condition with respect to the emission wavelength emitted from the active layer 3.
A diffusing agent (OCD) having a coating property is spin-coated on the entire surface of the cap layer 6 (FIG. 2B). The non-reflection condition is that the thickness of the diffusing agent layer 7 is λ / 4n, where λ is the emission wavelength and n is the refractive index of the diffusing agent (diffusion source). In this example, since lamp annealing is performed at 800 ° C. to diffuse Zn, the refractive index of the diffusing agent layer 7 is 1.44,
Since the emission wavelength is 830 nm, the film thickness of the diffusing agent layer 7 is 1440Å. FIG. 6 shows the relationship between the rotation speed of the spinner and the coating film thickness when this diffusing agent is applied by the spinner. According to this figure, in order to obtain a film thickness of 1440Å, the rotation speed of the spinner is 1800 rpm. And it is sufficient.

Then, the diffusing agent layer 7 applied on the cap layer 6 is baked at 300 ° C. for 60 minutes, then an AZ resist is applied on the diffusing agent layer 7, and an AZ resist film 8 is formed by a photolithography process. The peripheral edge line is formed in a pattern having an uneven shape (for example, a gear shape), and using the AZ resist film 8 as a mask, the diffusing agent layer 7 outside the AZ resist film 8 is formed.
Are removed by etching, and the edge line of the diffusing agent layer 7 is formed into a desired uneven pattern [FIG. 2 (c)]. After this,
The AZ resist film 8 is peeled off.

In this way, after the pattern of the diffusing agent layer 7 in which the peripheral edge line is uneven is formed on the upper surface of the cap layer 6,
This diffusing agent layer 7 is subjected to, for example, lamp annealing at 800 ° C.
By heating for 10 minutes, Zn is contained in at least the current blocking layer 5
Is diffused to a depth penetrating through [Fig. 2 (d)]. As a result, a part of the current blocking layer 5 becomes a high-concentration p-type inversion region, and the current passage region 9 is formed by the p ⁺ -AlGaAs high-concentration semiconductor region. As shown in FIG. 3, the upper surface of the current passage region 9 has an outer peripheral edge line on the surface of the cap layer 6 which is an uneven edge line 13 having a shape like a gear.

After that, the AZ resist 10 is applied again on the diffusing agent layer 7 and a shape (for example, inscribed in the uneven edge line of the diffusing agent layer 7 is inscribed by a normal photolithography process).
The AZ resist 10 is patterned so as to form an inscribed circle). When the p-side electrode 11 is formed on the upper surface of the cap layer 6 by using the AZ resist 10 as a mask [FIG. 2 (e)] and the light extraction window 12 is formed in the p-side electrode 11 by the lift-off method, the light extraction window 12 is The periphery is the current passage area 9
It is inscribed in the uneven edge line 13 on the upper surface of. Finally, the n-side electrode 14 made of AuGeNi is formed on the entire lower surface of the substrate 1 [FIG. 1].

In this light emitting diode A, however, when a driving voltage is applied between the p-side electrode 11 and the n-side electrode 14, a current flows from the p-side electrode 11 into the current passage region 9 and the current passage region is formed. Current is injected from the bottom surface of the active layer 9 into the active layer 3 to emit light in the active layer 3. The light emitted from the active layer 3 passes through the current passage region 9 and is emitted from the light extraction window 12 of the p-side electrode 11.

FIG. 4 is an enlarged plan view showing an X portion of FIG.
5A and 5B are a sectional view taken along the line YY and a sectional view taken along the line ZZ of FIG. In the light emitting diode A manufactured in this way, as shown in FIG. 4, when the outer peripheral portion of the current passage region 9 does not overlap the p-side electrode 11 over the entire circumference and the overlap length s is equal. As compared with the conventional light emitting diode in which the outer peripheral portion of the current passage region 9 is entirely covered by the p-side electrode 11, the ratio of the outer peripheral portion of the current passage region 9 being shaded by the p-side electrode 11 is reduced by half. There is. Therefore, although the outer peripheral portion of the current passage region 9 overlaps the p-side electrode 11, it is possible to prevent the luminous efficiency from decreasing as much as possible.

The current j injected into the current passage region 9
₁ is directly injected from the p-side electrode 11 into the upper surface of the outer peripheral portion of the current passage region 9 as shown in FIGS. 4 and 5A and 5B. At the same time, the current j ₂ flowing into the cap layer 6 from the p-side electrode 11 in the vicinity of the current passage region 9 is generated from the outer peripheral surface of the cap layer 6 (the surface along the irregular edge line 13).
Is injected into. However, in this light emitting diode A,
Since the outer periphery of the current passage region 9 is the uneven edge line 13, the length of the current injection region where the current j ₂ is injected from the cap layer 6 to the current passage region 9 (distance along the uneven edge line 13).
Is very long, the current j ₁ + j ₂ injected from the cap layer 6 to the current passage region 9 is increasing, and the resistance between the p-side electrode 11 and the current passage region 9 is small.
Therefore, the element resistance of the light emitting diode A is small. As a result, in the light emitting diode A of the present invention, it is possible to reduce the element resistance while reducing the reduction in light emission efficiency.

In the above embodiment, the shape of the uneven edge line 13 on the upper surface of the current passage region 9 is a square wave shape, but it may be a triangular wave shape or a sine wave shape, and as shown in FIG. It does not have to be present, and may be a non-periodic uneven edge line 13 or a random uneven edge line 13. Further, the inner peripheral edge of the light extraction window 12 of the p-side electrode 11 is inscribed in the uneven edge line 13 in the embodiment, but may be in the middle between the position inscribed in the uneven edge line 13 and the position inscribed in the outer edge. Good (that is, the p-side electrode 11 may partially overlap the region of the uneven edge line 13).

Although the case of the light emitting diode has been described in the above embodiment, the present invention can be similarly applied to the semiconductor laser device.
Also, the conductivity type is not limited to that of the above embodiment, and the conductivity type of each layer may be opposite to that of the above embodiment. In that case, the current passage region also needs to be n-type. It goes without saying that the light emitting element is not limited to the AlGaAs light emitting element. Moreover,
Although there is one pn junction on the active layer in the above embodiment, it may be two or more.

[0022]

According to the present invention, it is possible to reduce the shadow of the electrode and reduce the reduction of the light emission output. Moreover, the current passage region and the electrode can be brought into contact with each other, the length of the current injection region can be increased, and the element resistance can be reduced to improve the reliability of the element.

Therefore, according to the present invention, the current passage region in the shadow of the electrode can be made as small as possible, and the element resistance can be made small without reducing the light emission output.

[Brief description of drawings]

FIG. 1 is a sectional view showing a light emitting diode according to an embodiment of the present invention.

2 (a), (b), (c), (d), and (e) are cross-sectional views showing a method for manufacturing the above light emitting diode.

FIG. 3 is a plan view showing a light emitting diode immediately after a current passage region is formed in the above manufacturing process.

FIG. 4 is an enlarged plan view of an X portion of FIG.

5A and 5B are cross-sectional views taken along the line YY of FIG. 4 and Z-.
It is a Z line sectional view.

FIG. 6 is a diagram showing the relationship between the rotation speed of the spinner and the film thickness of the diffusing agent applied by the spinner.

FIG. 7 is a cross-sectional view showing a conventional light emitting diode.

FIG. 8 is a sectional view showing another conventional light emitting diode.

[Explanation of symbols]

 3 Active Layer 5 Current Blocking Layer 9 Current Passage Region 11 P-side Electrode 12 Light Extraction Window 13 Uneven Edge Line

Claims (1)

[Claims] 1. A current block layer having at least one reverse pn junction is formed above the active layer, and a current passage region is provided by diffusing impurities by penetrating a part of the current block layer to form a current block region. In a light-emitting element in which an electrode provided above the layer has a light extraction window facing the upper surface of the current passage region, an edge line on the upper surface of the current passage region is formed in an uneven shape and provided above the current block layer. The light-emitting element is characterized in that the electrode is in contact with the upper surface of the current passage region over all or part of the uneven edge line.