KR100263934B1 - Semiconductor laser device and its manufacturing method - Google Patents

Abstract

PURPOSE: A semiconductor laser device is provided to reduce an astigmatism distance and an oscillation start current by surrounding an active layer with an AlGaInP clad layer having high energy gap and low refractive index. CONSTITUTION: An n-GaInP buffer layer(20), an n-InGaAIP lower clad layer(30) are formed on an n-GaAs substrate(10) the lower surface of which an n-type lower electrode(101) is formed on. An inverse mesa structure consists of a GaInP active layer(41), a p-type AlGaInP upper clad layer(51) and a p-GaInP layer(61) sequentially formed on the lower clad layer(30). A p-AlGaInP upper clad layer is prepared at both sides of the active layer(41)and the upper clad layer(51). An n-GaAs current limiting layer(80) is formed on the upper clad layer. A p-GaAs cap layer(90) and a p-type upper electrode(201) are prepared on the layers(80,61).

Description

Semiconductor laser device and manufacturing method thereof

1 is a schematic cross-sectional view of a semiconductor laser device according to the prior art.

2 is a schematic cross-sectional view of a semiconductor laser device according to the present invention.

3 to 6 are schematic cross-sectional views of manufacturing steps of the semiconductor laser device according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor laser devices used for optical information processing such as optical disks and magneto-optical disks, and more particularly, to a semiconductor laser device having a small oscillation start current and capable of high output operation, and a method of manufacturing the same.

In general, lasers using amplification of light by induced emission are characterized by unipolarity, directivity, and high intensity, and are gas lasers such as helium-neon (He-Ne) lasers or iron (Ar) lasers. And solid-state lasers such as YAG lasers and ruby lasers, ranging from small, high-frequency semiconductor lasers that are easily modulated by modulating bias current at high frequencies. Among them, semiconductor lasers are particularly useful for information processing devices such as compact disc players (CDPs), optical memories, high-speed laser printers, and optical communication devices, and replace the conventional gas lasers such as helium-neon. The range is expanding.

A semiconductor laser device is a semiconductor device that includes the concept of quantum electrons based on PN junctions, and induces electron-hole recombination by artificially injecting current into a thin film made of a semiconductor material, that is, an active layer. It emits light corresponding to the reduced energy that follows.

In recent years, the performance of semiconductor lasers has grown epitaxially to develop materials that determine wavelengths and to realize device structures that determine characteristics and reliability such as critical current, light output, oscillation efficiency, single wavelength, and spectral line width. Significant developments are being made due to advances in technology and micromachining technology. Particularly in epitaxial growth technology, instead of the conventional liquid phase epitaxy (LPE) method, such as organic organic vapor deposition (MOCVD) and molecular beam epitaxy (MBE), etc. The widespread use of gas phase growth has allowed atomic level control.

Meanwhile, the semiconductor laser device for optical information processing represented by the optical disk requires shortening the wavelength and high output of the semiconductor laser device in order to increase the optical information processing speed and the information storage density. In addition, semiconductor laser devices have various types of device structures in order to increase optical power, increase efficiency, and obtain a desired type of beam.

1 shows an example of a semiconductor laser device having a conventional SBR (Selectively Buried Ridge) structure.

Referring to FIG. 1, as a conventional ridge stripe structure, a ridge is formed in the center of the upper surface of the P-InGaAlP cladding layer 5, and a p-InGaP buffer layer (6: bi-conducting layer) is formed on the ridge. Is formed. N-GaAs current limiting layer 7 having an opening for exposing the transfer layer 6 is provided on both sides of the ridge, and a p-GaAs cap layer 8 and a p-metal electrode are disposed on the current limiting layer. 201: upper electrode) is formed. A GaInP active layer 4 is provided below the p-InGaAlP cladding layer, and an n-InGaAlP cladding layer 3 and a buffer layer 2 are formed below the active layer. The single layer structure as described above is formed on a substrate on which an n-metal electrode 101 (lower electrode) is formed on its bottom surface.

According to the conventional technique, the semiconductor laser device having the above-mentioned ridge stripe structure is manufactured by three times crystal growth by the organometallic vapor phase growth method. Specifically, first, an n-GaInP buffer layer 2, an n-AlGaInP clad layer 3, a GaInP active layer 4, a p-AlGaInP clad layer 5 and a p-GaInP buffer layer 6 on a GaAs substrate 1. : Firstly grow the current transfer layer), and then form a silicon oxide film (not shown) for ridge formation on the buffer layer 6, and use the silicon oxide film as a mask to form the buffer layer 6 and p The AlGaInP cladding layer 5 is partially etched to form the ridge of the semiconductor laser device.

Next, using the silicon oxide film as an epitaxial growth suppression mask, after selectively growing the n-GaAs current limiting layer 7 on both sides of the ridge on the p-AlGaInP cladding layer 5, the silicon Remove the oxide film. Next, a p-GaAs cap layer 8 is tertiarily grown on the current limiting layer 7 and the current transfer layer 6.

Then, the upper electrode 201 is formed on the cap layer 8, and the lower electrode 101 is formed on the bottom surface of the substrate 1 to complete the semiconductor laser device.

In order to manufacture the semiconductor laser device having the conventional ridge structure described above, rough crystal growth is required three times, and in order to obtain a basic transverse mode (FTM), the thickness of the active layer 4 and the active layer and the p-clad layer 5 There is a process difficulty to precisely adjust the distance of).

In addition, the distance between the active layer 4 and the p-clad layer 5 should be reduced in order to reduce the astigmatism distance between the single mode and the optical power density, which is too high. There is a problem.

Accordingly, it is an object of the present invention to provide a semiconductor laser device having a novel structure in which the above problems are improved.

Another object of the present invention is to provide a method for manufacturing a semiconductor laser device suitable for manufacturing the semiconductor laser device.

In order to achieve the above object, the semiconductor laser device of the present invention is a semiconductor laser device having an active layer formed on a substrate and having a local laser oscillation region and a current limiting layer for supplying a limited current to the active layer, wherein the active layer Is characterized by being surrounded by a clad layer having a large energy cap and a low refractive index adjacent to the upper, lower, left and right sides.

For example, the active layer may be formed of GaInP, and the clad layer may be formed of AlGaInP.

Specific semiconductor laser device of the present invention is a GaAs substrate; An n-InGaAlP lower clad layer formed on the substrate; An inverted mesa structure formed at a central portion on the lower clad layer and comprising a GaInP active layer, a p-AlGaInP upper first clad layer formed on the active layer, and a p-GaInP conducting bilayer formed on the upper first clad layer; A second p-AlGaInP upper cladding layer formed on both sides of the reverse mesa structure on the lower cladding layer; An n-GaAs current limiting layer formed on the upper second cladding layer; And a p-GaAs cap layer formed on the current limiting layer and the current transfer layer.

In another aspect, a method of manufacturing the present invention includes: forming a lower clad layer, an active layer, an upper first clad layer, and an electricity transfer layer on a substrate; Partially etching the active layer, the upper first cladding layer, and the energizing bilayer to form an inverted mesa structure including an active layer, an upper first cladding layer, and an energizing bilayer, which are etched in a central region above the lower clad layer; ; Selectively forming an upper second clad layer on both sides of the reverse mesa structure on the lower clad layer; And selectively forming a current limiting layer on the upper second cladding layer.

The active layer of the present invention is in the form of a stripe formed in a portion of the central region on the lower clad layer, the upper second clad layer is formed lower than the upper first clad layer on both sides of the reverse mesa structure. In addition, the current limiting layer is formed on the upper second cladding layer on both sides of the reverse mesa structure, the height is formed the same as the current transfer layer to form a flat surface.

In the present invention, the stripe-type active layer is surrounded by an AlGaInP clad layer having a high energy cap and a low refractive index, thereby improving the light limiting effect in the lateral direction, thereby lowering the oscillation start current and astigmatism distance, and easily obtaining a high output.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view showing the structure of a semiconductor laser device according to the present invention.

An n-GaInP buffer layer 20 and an n-InGaAlP lower clad layer 30 are formed on an n-GaAs substrate 10 having an n-bottom electrode 101 formed on a bottom surface thereof. An inverted mesa structure including a GaInP active layer 41 formed at a central portion on the lower cladding layer 30, a p-AlGaInP upper first cladding layer 51, and a p-GaInP conducting transition layer 61 is provided. The active layer 41 is made of GaInP but may be made of other materials such as GaAs, AlGaAs, InGaAs, InGaAsP, or the like.

In addition, p-AlGaInP upper second cladding layer 70 formed on both sides of the active layer 41 and the upper first cladding layer 51 to a predetermined depth is provided, and n-GaAs current limiting is formed on the upper second cladding layer. Layer 80 is formed. The p-GaAs cap layer 90 and the p-phase electrode 201 are provided on the current limiting layer and the current transfer layer.

The active layer of the present invention is in the form of a stripe formed in a portion of the central region on the lower clad layer, the upper second clad layer is formed lower than the upper first clad layer on both sides of the reverse mesa structure. In addition, the current limiting layer is formed on the upper second cladding layer on both sides of the reverse mesa structure, the height is formed the same as the current transfer layer to form a flat surface.

In the present invention, since the stripe-type active layer is surrounded by an AlGaInP material layer having a high energy cap and a low refractive index, the light limiting effect in the lateral direction is improved.

The semiconductor laser device of the present invention having such a structure has a modified SBR structure.

Hereinafter, the manufacturing method of the semiconductor laser element of this invention is demonstrated in detail.

3 to 6 are schematic diagrams for illustrating an example of the method for manufacturing the laser diode of the present invention described above.

Referring to FIG. 3, the n-GaInP buffer layer 20 (first buffer layer), the n-AlGaInP lower cladding layer 30 and the GaInP active layer 40 may be formed on the n-GaAs substrate 10 by an organometallic vapor phase growth method. Growing sequentially by molecular beam growth method. Subsequently, a p-AlGaInP upper first cladding layer 50 and a p-GaInP buffer layer 60 (second buffer layer) are sequentially stacked on the active layer by organometallic vapor phase growth or molecular beam growth.

Referring to FIG. 4, after forming a silicon oxide film on the second buffer layer 60, the silicon oxide film is patterned by a conventional photolithography process to form a reverse mesa structure at a central portion. The silicon oxide film pattern 62 is formed.

The active layer 40, the upper cladding layer 50, and the second buffer layer 60 are etched using the silicon oxide layer pattern 62 as an etching mask. The etched active layer 41, the upper first cladding layer 51, and the second buffer layer 61 have an inverse mesa structure in which the width of the etched second buffer layer 61 is relatively wider than that of the tkdrl etched active layer 41. do.

Referring to FIG. 5, both sides of the etched active layer 41, the upper first cladding layer 51, and the second buffer layer 61 are formed by using the silicon oxide layer pattern 62 as an epitaxial growth suppression mask. Optionally, the p-AlGaInP upper second cladding layer 70 and the n-GaAs current limiting layer 80 are sequentially formed.

Referring to FIG. 6, after removing the silicon oxide layer pattern 62, a p-GaAs cap layer 90 is formed on the upper surface of the current limiting layer 80 and the second buffer layer 61 etched.

Next, an upper electrode 201 is formed on the cap layer 90, and a lower electrode 101 is formed on the bottom surface of the substrate 10 to complete the semiconductor laser device of the present invention as shown in FIG. 2. do.

The active layer of the present invention is formed in a central predetermined region on the lower cladding layer and has a stripe shape, and is surrounded by an AlGaInP cladding layer on the upper, lower and left and right sides of the active layer.

In the present invention described above, since the active layer is formed in a stripe shape and is surrounded by an AlGaInP cladding layer having a high energy cap and a low refractive index, the light limiting effect in the lateral direction is improved, so that the oscillation start current and astigmatism distance can be lowered and high power can be obtained. It can be obtained easily.

As mentioned above, although this invention was demonstrated concretely by the said Example, this invention is not limited to this, A deformation | transformation and improvement are a matter of course within the range of common knowledge of a person skilled in the art.

Claims (5)

A semiconductor laser device having an active layer formed on a substrate and having a local laser oscillation region and a current limiting layer for supplying current to the active layer in a limited manner, wherein the active layer forms the active layer on the top, bottom, left and right sides thereof. A semiconductor laser device characterized in that it is surrounded by a cladding layer composed of a material having a larger energy cap and a lower refractive index than the material. The semiconductor laser device according to claim 1, wherein the active layer is made of GaInP, and the clad layer is made of AlGaInP. According to claim 1, wherein the lower cladding layer is provided below the active layer and the upper first cladding layer and the conductive layer is formed on the upper, the active layer, the upper first cladding layer and the conductive layer is a reverse mesa structure The semiconductor laser device characterized by the above-mentioned. 4. The semiconductor laser device according to claim 3, wherein the current limiting layer is provided on the second upper cladding layer formed on both sides of the reverse mesa structure, and the height is formed to be the same as the current transfer layer to form a flat surface. . Forming a lower cladding layer, an active layer, an upper first cladding layer, and an electricity transfer layer on the substrate; Partially etching the active layer, the upper first cladding layer, and the energizing bilayer to form an inverted mesa structure including an active layer, an upper first cladding layer, and an energizing bilayer etched in a central predetermined area above the lower clad layer; step; Selectively forming an upper second clad layer on both sides of the reverse mesa structure on the lower clad layer; And selectively forming a current limiting layer on the upper second cladding layer.