JPH05327018A - Semiconductor light emitting device and its manufacture - Google Patents

Abstract

PURPOSE:To make light output characteristic uniform by preventing metal from attaching to an unnecessary part in a vapor deposition process of an electrode. CONSTITUTION:A buried layer 12 of a high resistance compound semiconductor is buried in a reverse mesa type etching groove formed in both sides of a line of a light emitting part 7 parallel to the line keeping electric isolation and a surface is flat as before etching. Therefore, a projecting corner part is not formed in the light emitting part 7 even if a normal mesa type etching groove is thereafter formed for separating each light emitting part 7. As a result, metal is not vapor deposited on an unnecessary part during vapor deposition of an electrode 10, light emitted from the light emitting part 7 is not screened and a p-n junction part is not shortcircuited.

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 such as a monolithic light emitting diode array.

[0002]

2. Description of the Related Art Conventionally, light emitting diode arrays have been used as various light sources in various devices such as LED printers. Then, in a monolithic light-emitting diode array in which a plurality of light-emitting portions (light-emitting diode portions) are formed in rows on the surface of a compound semiconductor made of each layer epitaxially grown on a single crystal substrate, each light-emitting portion has a selective diffusion method or mesa. They are separated by a mold etching method or the like. For example, when the light emitting portion of the compound semiconductor in which the GaAsP layer is epitaxially grown on the GaAs substrate is separated by the selective diffusion method, Zn is often diffused into the boundary portion of each light emitting portion of the epitaxially grown GaAsP layer. Although this method is adopted, this method is applied to the interface between the diffusion mask and the GaAsP layer surface by Z
There is a drawback that n easily diffuses and the manufacturing yield deteriorates.

Therefore, a mesa type etching method is widely used in which unevenness is formed on the surface of the substrate to separate each light emitting portion. This mesa type etching method will be described with reference to FIGS. FIG. 5 is a perspective view showing a compound semiconductor before etching,
6 is a sectional view taken along the line AA of the semiconductor light emitting device obtained by etching the compound semiconductor shown in FIG. 5, and FIG. 7 is a sectional view taken along the line BB.
FIG. 8 is a partially enlarged perspective view showing a light emitting portion.

The compound semiconductor shown in FIG.
0) p-type Al _w Ga _1-w As on p-type GaAs substrate 1
A buffer layer 2, a p-type Al _x Ga _1-x As clad layer 3,
p-type Al _y Ga _1-y As active layer 4 and n-type Al _z Ga
_{The 1-z} As clad layer 5 is formed by sequentially performing epitaxial crystal growth by a method such as LPE (liquid phase epitaxy) (however, y <x, z). And on this, SiO ₂ , S
An etching mask 6 such as iN is provided as shown in the figure, and after patterning, when etching is performed using a hydrochloric acid-based or phosphoric acid-based etchant, the light emitting portion 7 is separated as shown in FIGS. 6 and 7. To be done.

Generally, a III-V compound semiconductor crystal has a strong anisotropy in the etching direction, and when the (1 0 0) plane is mesa-etched to form a groove in the <0 1 1> direction, the groove is formed. The ridge angle on the side surface of the groove is an acute angle (inverse mesa), and when the mesa etching is performed to form a groove in the <0 −1 1> direction, the ridge angle on the side surface of the groove is an obtuse angle (forward mesa).
Becomes Therefore, in this example, the crystal axis in the column direction (array direction) in which the light emitting portions 7 are arranged is the <0 -11> direction, and therefore the grooves etched in the direction parallel to this column are in the forward direction as shown in FIG. The groove is a mesa-type etching groove, and in the direction perpendicular to this groove, the crystal axis is in the <0 1 1> direction, so that the groove etched between them in order to separate each light emitting portion 7 is as shown in FIG. It becomes an inverted mesa type etching groove. Then, the n-type Al _z Ga _{1 -z} As clad layer 5
After forming a protective film 8 on the entire surface and forming a through hole 9 in the electrode contact portion on the light emitting portion 7, the electrode 10 is made to crawl on a forward mesa type etching groove by a lift-off method (vertical direction to the array direction. ), And is pulled out (Fig. 8). It should be noted that when metal is vapor-deposited on the inverted mesa type etching groove, breakage occurs, so that it is not preferable to draw out the electrode so as to crawl on the inverted mesa type etching groove.

[0006]

In the lift-off method, the resist is patterned before the electrode material is deposited.
It is difficult to apply the resist uniformly on the surface of a substrate having steps, and the resist becomes thin at the corners of the protruding steps. In the semiconductor light emitting device having the conventional structure as described above and shown in FIG. 8, the resist applied to the four corner portions of the light emitting portion 7 etched into the mesa shape becomes thin, and the resist in this portion is developed during development. Thaw and protective film 8
Is exposed, and metal 1 is also deposited on this part during metal deposition of the electrode 10.
0a to 10d were sometimes vapor-deposited. Therefore, the n-type Al _z Ga _1-z As cladding layer 5 and the p-type Al _x
The Ga _1-x As clad layer 3 and this metal 10a to 10d
Are connected to each other to cause a short circuit or interfere with light emitted from the upper surface of the light emitting portion 7,
There was a problem that the output light level of was not uniform. In addition, if the entire resist is applied thickly to prevent metal adhesion to the corners, it becomes difficult to obtain a precise line width for patterning, and a good electrode shape cannot be obtained. was there. Therefore, it is an object of the present invention to prevent the metal from adhering to unnecessary portions in the electrode vapor deposition process by eliminating the protruding corners of the light emitting portion.

[0007]

As a means for achieving the above object, in a semiconductor light emitting device having a plurality of light emitting portions formed in a row in a compound semiconductor having a pn junction, each light emitting portion is a forward mesa. It is characterized in that it is separated from each other by a groove having a rectangular shape and a groove having a reverse mesa shape provided in a direction perpendicular to the groove having a forward mesa shape, and a high resistance compound semiconductor is embedded in the groove having a reverse mesa shape. And a method for manufacturing a semiconductor light emitting device in which a plurality of light emitting portions are formed in rows on a surface of a compound semiconductor having a pn junction, wherein the compound is formed to form a pn junction on a single crystal substrate. A step of epitaxially growing a semiconductor, a step of etching the compound semiconductor surface until a pn junction is exposed to form a reverse mesa-shaped groove, and a step of forming the reverse mesa-shaped groove And a step of selectively growing a compound semiconductor having a resistance and a step of forming a forward mesa groove by etching the compound semiconductor surface in a direction perpendicular to the reverse mesa groove until a pn junction is exposed. An object of the present invention is to provide a method for manufacturing a semiconductor light emitting device.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the semiconductor light emitting device of the present invention will be described with reference to the drawings. 1 is a perspective view showing a semiconductor light emitting device of this embodiment, FIG. 2 is a sectional view taken along line CC of the semiconductor light emitting device shown in FIG. 1, and FIG. 3 is a sectional view taken along line DD of the semiconductor light emitting device shown in FIG.
FIG. 4 is a perspective view showing the compound semiconductor before etching.

First, a method of manufacturing the semiconductor light emitting device shown in FIG. 1 will be described. The compound semiconductor shown in FIG.
0) p-type Al _w Ga _1-w As on p-type GaAs substrate 1
A buffer layer 2, a p-type Al _x Ga _1-x As clad layer 3,
p-type Al _y Ga _1-y As active layer 4 and n-type Al _z Ga
Each of the _1-z As cladding layers 5 is LPE (liquid phase growth method)
The epitaxial crystal is sequentially grown by the above method (however, y <x, z). And this n-type Al
After the etching mask 6 made of SiO ₂ , SiN or the like is attached on the entire surface of the _z Ga _{1 -z} As clad layer 5 by the plasma CVD method, the etching mask 6 is provided as shown in the figure in order to form an inverted mesa type etching groove. Dry etching is performed in a stripe shape in the <0 1 1> direction. Next, using a hydrochloric acid-based or phosphoric acid-based etchant, the portion without the etching mask 6 is etched up to the middle of the p-type Al _x Ga _1-x As clad layer 3, and the light emitting portions 7 are aligned in the column direction. An inverted mesa type etching groove parallel to the (array direction) is obtained.

Further, this compound semiconductor was put in a MOCVD apparatus to obtain a high resistance undoped GaAs burying layer 1.
2 is selectively grown in an inverted mesa type etching groove by MOCVD (metal organic chemical vapor deposition) to make the compound semiconductor substrate surface almost flat. By setting the resistance value of the buried layer 12 to 10 ⁷ Ω · cm or more, both sides of the buried layer 12 are practically electrically insulated. At this time, the compound semiconductor substrate temperature and GaAs
GaAs can have a high resistance by properly selecting the composition ratio of. Further, since there is no unevenness other than the inverted mesa type etching groove, the GaAs buried layer 12 can be grown in a flat state. Furthermore, since the growth rate of GaAs is stable, the GaAs buried layer 12
The height of the can be easily controlled.

Then, the etching mask 6 is attached again to the flattened surface of the compound semiconductor substrate, and in order to separate the light emitting portions 7 this time, the p-type is formed in the direction perpendicular to the row direction of the light emitting portions 7 between them. Al _x Ga _1-x As clad layer 3
Etching is performed halfway. At this time, since the crystal axis of the etching groove is in the <0 -11> direction, a forward mesa etching groove is formed, and each light emitting portion 7 is divided by the forward mesa etching groove. After that, SiN is formed on the entire surface of the n-type Al _z Ga _1-z As cladding layer 5 side.
After providing the protective film 8 such as, the through hole 9 is provided in the electrode contact portion on the light emitting portion 7 by dry etching,
Au should be pulled out in a direction perpendicular to the row direction of the light emitting portions 7.
The electrode 10 is provided by depositing a GeNi alloy. Furthermore, p
After polishing the back surface of the type GaAs substrate 1, AuBe is vapor-deposited on the entire surface to form the electrode 11.

The semiconductor light emitting device thus formed is
As shown in FIG. 2, a high-resistance compound semiconductor burying layer 12 is buried in the opposite mesa type etching grooves formed on both side surfaces of the row of the light emitting portions 7 in a direction parallel to the row and electrically isolated. Since the flat surface state is the same as that before etching, even if a forward mesa type etching groove for separating each light emitting portion 7 is formed thereafter, no protruding corner portion is formed in the light emitting portion 7. .. As a result, the metal is not vapor-deposited even on a portion which is not necessary when the electrode 10 is vapor-deposited, and the light emitted from the light-emitting portion 7 is not blocked or the pn junction portion is not short-circuited. Then, the electrode 10 deposited over the buried layer 12 is deposited.
Since it crawls on a flat surface, the shape of each electrode 10 can be easily made uniform, and it is possible to further reduce variations in characteristics due to the electrode shape. Even if the embedded layer 12 is higher than the surface of the light emitting portion 7, there is no protruding corner in the light emitting portion 7, so that no electrode material is deposited on unnecessary portions on the light emitting portion 7. It is possible to obtain the same effect as that of the above embodiment.

It is also possible to form the rows of light emitting portions in the <0 -11> direction which is the vertical direction to the above-mentioned embodiment. In this case, a forward mesa etching groove is formed on both side surfaces of the row of light emitting portions in a direction parallel to this row, and a reverse mesa etching groove is formed in a direction perpendicular to the row of light emitting portions so as to separate each light emitting portion. And a buried layer of a high resistance compound semiconductor is formed in the inverted mesa type etching groove. In this case, the electrode is crawled over the forward mesa type etching groove, and there is some variation in characteristics as compared with the case of crawling over the buried layer, but the groove that separates each light emitting part is a reverse mesa type etching groove. Since it is a groove, it is possible to form the light emitting portions closer to each other. As a result, the semiconductor light emitting device can be downsized, and more light emitting portions can be formed within a certain area. And, even in this case, since the protruding corner portion cannot be formed in the light emitting portion, the metal is not deposited even in a portion unnecessary when depositing the electrode, and the light emitted from the light emitting portion is blocked. , The pn junction portion is not short-circuited.

[0014]

According to the semiconductor light emitting device of the present invention, each light emitting portion is separated by the forward mesa groove and the reverse mesa groove provided in the direction perpendicular to the forward mesa groove. Since the high-resistance compound semiconductor is embedded in the inverted mesa-shaped groove, when patterning the resist when depositing the electrode, there is no exposed portion that is not covered by the resist, and the electrode material adheres to the unnecessary portion. As a result, there is no short circuit from the n-clad layer to the p-clad layer, which enables optimum electrode wiring. Further, since the electrode material does not adhere to unnecessary portions of the light emitting portion and interferes with the emitted light, there is an effect that the current-light output characteristics in each light emitting portion become substantially uniform.

Further, the plurality of light emitting portions are separated by the inverted mesa-shaped grooves formed in the direction parallel to the row direction, and separated by the forward mesa-shaped grooves formed in the direction perpendicular to the row direction. In the case where a high-resistance compound semiconductor is embedded in the inverted mesa-shaped groove and each electrode connected to a plurality of light-emitting portions is drawn out through the high-resistance compound semiconductor, The electrodes can be vapor-deposited on a flat surface, and the shapes of the electrodes can be easily made uniform to reduce the variation in characteristics.

After forming the reverse mesa-shaped groove, the high-resistance compound semiconductor is selectively grown in the reverse mesa-shaped groove before forming the forward mesa-shaped groove. Can be grown flat to the same height as and the electrode can be deposited on a flat surface.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a semiconductor light emitting device of the present invention.

FIG. 2 is a sectional view taken along line CC of the embodiment shown in FIG.

FIG. 3 is a cross-sectional view taken along the line DD of the embodiment shown in FIG.

FIG. 4 is a perspective view showing a patterning example of the semiconductor light emitting device of the present invention.

FIG. 5 is a perspective view showing a patterning example of a conventional semiconductor light emitting device.

6 is a cross-sectional view taken along line AA of the conventional example shown in FIG. 5 after etching.

7 is a cross-sectional view taken along line BB of the conventional example shown in FIG. 5 after etching.

FIG. 8 is a partially enlarged perspective view showing a conventional semiconductor light emitting device.

[Explanation of symbols]

1 p-type GaAs substrate 2 p-type Al _w Ga _1-w As buffer layer 3 p-type Al _x Ga _1-x As clad layer 4 p-type Al _y Ga _1-y As active layer 5 n-type Al _z Ga _1-z As clad layer 6 Etching mask 7 Light emitting portion 8 Protective film 9 Through hole 10, 11 Electrode 12 Buried layer

Claims (3)

[Claims] 1. A semiconductor light emitting device having a plurality of light emitting portions formed in a row in a compound semiconductor having a pn junction, wherein each light emitting portion has a forward mesa groove and a direction perpendicular to the forward mesa groove. A semiconductor light emitting device, characterized in that they are separated by provided reverse mesa-shaped grooves, and a high-resistance compound semiconductor is embedded in the reverse mesa-shaped grooves. 2. A semiconductor light emitting device having a plurality of light emitting portions formed in a row in a compound semiconductor having a pn junction, wherein the plurality of light emitting portions have an inverted mesa shape formed in a direction parallel to the row direction. While being separated by a groove, each is separated by a forward mesa-shaped groove formed in a direction perpendicular to the columnar direction, and a high-resistance compound semiconductor is embedded in the inverted mesa-shaped groove, and A semiconductor light emitting device, wherein each electrode connected to a plurality of light emitting portions is drawn out through the high resistance compound semiconductor. 3. A method for manufacturing a semiconductor light-emitting device, wherein a plurality of light-emitting portions are formed in rows on the surface of a compound semiconductor having a pn junction, the compound semiconductor being epitaxially grown so as to form a pn junction on a single crystal substrate. A step of forming a reverse mesa-shaped groove by etching the compound semiconductor surface until the pn junction is exposed, a step of selectively growing a high-resistance compound semiconductor in the reverse mesa-shaped groove, A step of etching a semiconductor surface in a direction perpendicular to the reverse mesa-shaped groove until a pn junction is exposed to form a normal mesa-shaped groove.