KR100278629B1 - Semiconductor laser diode and manufacturing method thereof - Google Patents

Abstract

Disclosed is a refractive index waveguide semiconductor laser diode which modifies the structure of a current blocking layer for limiting current flow and performs optical waveguide using the bending of an active layer. The P-type current blocking layer is formed on the n-type substrate so that the side wall forms a constant inclined surface and the bottom surface has a flat through groove left at the center portion of the n-type substrate, and the exposed portion is exposed through the current blocking layer and the through groove. The n-type cladding layer is formed on the substrate and has a structure in which n-type / p-type impurities are alternately doped on the inclined surface and serves to cut off current. An active layer having a laser oscillation region formed in the through-hole region is formed on the n-type cladding layer, and a p-type cladding layer is formed on the active layer.

The current spreading phenomenon is eliminated, driving current value is lowered, single mode oscillation is advantageous, and astigmatism distance is reduced.

Description

Semiconductor laser diode and manufacturing method thereof

1 is a schematic cross-sectional view of a conventional laser diode.

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

3 is a cross-sectional view for explaining the principle of operation of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser diode and a method for manufacturing the same, and more particularly, to a refractive index waveguide semiconductor laser diode and a method for manufacturing the same, used in an information processing device, plastic optical communication, a point of sales (POS) system, and the like.

In general, lasers using amplification of light by induced emission are characterized by coherence, unipolarity, directivity, and high intensity. Helium-neon lasers and argon There are a variety of types ranging from gas lasers such as (Ar) lasers and solid state lasers such as YAG lasers and ruby lasers to semiconductor lasers that are small and easily modulated by modulating bias current at high frequencies.

In particular, semiconductor lasers are used for information processing devices such as compact disc players (CDPs), optical memories, high-speed laser printers, and optical communication devices. The range is expanding.

Generally, a semiconductor laser device is a semiconductor device including a concept of quantum electrons based on a PN junction, and recombines by artificially inducing electron-hole recombination by injecting current into a thin film made of a semiconductor material, that is, an active layer. A semiconductor laser diode that emits light corresponding to the reduced energy.

In recent years, the performance of semiconductor lasers is epitaxial growth technology for the development of materials that determine the wavelength, and the device structure that determines the characteristics and reliability of the critical current, light output, efficiency, single wavelength, spectrum spectrum width, etc. And the remarkable development by the progress of the micro-processing technology.

Particularly, epitaxial growth technology replaces the conventional liquid phase growth method (LPE method), and at the atomic layer level by metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) methods. It is possible to control and reduce the critical current such as quantum well laser using quantum well as active layer, improve efficiency, improve output, high speed, narrow spectrum line width, etc. Significant performance improvements have been made.

On the other hand, AlGaInP-based laser, which is a material of a semiconductor laser, is the first to be realized by the above-described MOCVD method. As a semiconductor laser by injection of a carrier capable of continuous oscillation at room temperature, red visible light having the shortest wavelength of 0.6 µm is used. It is a laser. As a substitute for helium-neon lasers, which are widely used for measurement, it is currently used InGaP in which the active layer is lattice matched with a GaAs substrate.

On the other hand, in order to use the semiconductor laser diode in the above-mentioned application field, it is necessary to oscillate the stable optical beam by the index guide structure. Currently, the laser diode shown in FIG. 1 is an example of a laser diode used as a refractive index waveguide structure of a short wavelength semiconductor laser.

Referring to the drawings, a ridge is formed at the center of the upper surface of the p-In _0.5 (Ga _0.3 Al _0.7 ) _0.6 P cladding layer 5 and a p-In _0.5 Ga _0.5 P conducting bilayer 6 is formed on top of the ridge. And an n-GaAs current blocking layer 7 having an opening that exposes a central portion of the current transfer layer 6 thereon, and a p-GaAs cap layer 8 above the current blocking layer 7. Is formed and a p-metal electrode 9 is formed on the cap layer 8. An In _0.5 Ga _0.5 P active layer 4 is provided below the p-clad layer 5, and n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer 3 is provided below the active layer 4. The n-GaAs buffer layer 2 is provided. The single layer structure as described above is formed on the n-GaAs substrate 1 on which the n-metal electrode 10 is formed.

The laser diode of such a structure requires a third rough crystal growth process, which is not only complicated and time-consuming, but also disadvantageous in yield and mass productivity. Furthermore, the p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer (5) containing Al, in particular, exposed to air during crystal growth must be etched and the n-GaAs current blocking layer (7) is grown again on it. Therefore, due to contamination and oxidation of the p-clad layer 5 exposed to air, it is difficult to grow high-quality crystals during secondary growth, which results in deterioration of characteristics and reliability.

In addition, in the above structure, selective epitaxy is required to form an n-current blocking layer 7 while an insulating film such as, for example, a silicon oxide film is deposited on the upper ridge, which is a very advanced technique. In addition, when the silicon oxide film is removed after epitaxial growth, the p-In _0.5 Ga _0.5 P current carrying layer 6 inside the silicon oxide film is crystalline due to a different thermal expansion coefficient between the silicon oxide film and the compound semiconductor. A problem arises in that crystal quality is degraded.

In addition, the conventional structure is an optical waveguide structure using an effective refractive index in the lateral direction of the active layer 4 due to the presence of the n-GaAs current blocking layer (7), in this structure astigmatism (Astignatism) It is difficult to reduce to within 10㎛, in this case there is a burden such as adding a complex optical system for focusing the ray beam, the current blocking layer 7 is to absorb the beam oscillated from the active layer (4) It lowers the temperature characteristic of the device and accelerates the degradation due to deterioration.

It is therefore an object of the present invention to improve the problems of the prior art, to provide a semiconductor laser diode capable of oscillating a stable optical mode in which the optical waveguide is performed by the bending of the active layer.

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

In order to achieve the above object, the semiconductor laser diode according to the present invention comprises a first conductive substrate; A second conductive type current blocking layer formed on the first conductive type substrate such that a sidewall thereof forms a constant inclined surface and a bottom surface thereof has a flat through groove left in the center portion of the first conductive type substrate; It is formed recessedly on the substrate exposed through the current blocking layer and the through groove, the first conductive type doped on the flat surface is a current passing through the surface, the first conductive type / first on the inclined surface A first conductive type first clad layer having a structure in which impurities are doped alternately in the form of two conductivity type / first conductivity type / second conductivity type ... An active layer having a laser oscillation region formed in the through-hole region on the first conductive first cladding layer; And a second conductive second cladding layer formed on the active layer.

The present invention can be applied not only to InGaP / InGaAlP-based laser diodes, but also to GaAs / AlGaAsrP, InGaAs / InGaP-based two-way, three-way and four-way compound semiconductor laser diodes.

In the present invention, the n-type cladding layer is etched after primary crystal growth to form a p-type current blocking layer having an inclined surface, and in forming secondary crystal growth on the current blocking layer and the exposed substrate, the flat (100) The n-type impurity is doped onto the surface to form a current passing region, and alternately doped to n / p / n / ptlr along the inclined surface to form a current blocking layer. The inclined surface is etched to be (n11) plane (n ≦ 3). In addition, the active layer is bent into the through groove, characterized in that the optical waveguide is performed accordingly.

In addition, a p-type cap layer is formed on the p-type cladding layer through a p-type conductive layer, an n-type metal electrode is formed on the n-type substrate, and a p-type metal electrode is formed on the p-type cap layer.

In addition, in order to achieve the above another object, the method of manufacturing a semiconductor laser diode according to the present invention comprises the steps of forming a current blocking layer by primary crystal growth on the first conductive substrate; Forming a sloping surface having a constant sidewall at a central portion of the current blocking layer and having a flat through groove at a bottom thereof; Secondary crystal growth is carried out on the entire surface of the resultant, and the first conductive type impurities are doped on a flat surface to form a current passing through area. On the inclined surface, the first conductive type / second conductive type / first conductive type / second conductive type Forming a first conductive cladding layer alternately doped to form a current blocking role and recessed into the through groove; Forming an active layer recessed with the through grooves on the front surface thereof; and forming a second conductive clad layer on the active layer. In a specific method of manufacturing a semiconductor laser diode of the present invention, the first conductive cladding layer is formed by performing an epitaxial growth process while continuously supplying first conductive impurities and intermittently supplying second conductive impurities. can do.

In the present invention, the inclined surface is etched to be (n11) plane (n≤3), wherein the n-type cladding layer is performed by organometallic vapor phase growth (MOCVD), n-type impurities and p-type impurities It is formed by simultaneously doping.

In the present invention, the n-p / n / p ... alternately doped layer formed on the inclined surface of the p-type current blocking layer acts as a current blocking layer so that the current flows only to the through-groove portion, so that the current Spreading is prevented and the efficiency of the small intestine is increased.

In addition, in the present invention, as a real index guide structure in which the optical waveguide due to the bending of the active layer is performed, it is advantageous for single mode oscillation, and the astigmatism distance is reduced.

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

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

Referring to FIG. 2, a p-GaAs current blocking layer 22 is formed on the n-GaAs substrate 11. The current blocking layer 22 is formed on the entire surface of the substrate except for the stripe-shaped through grooves through which current may flow in the central portion of the substrate 11. The side wall of the through groove maintains a constant inclined surface. The inclined surface is maintained to be a (n11) plane (n ≦ 3), and the flat surface of the p-current blocking layer 22 forms a (100) plane.

N-type cladding layers 13 and 21 are formed on the n-type substrate 11 and the p-current blocking layer 22 exposed by the through holes. In this case, n-In0.5 (Ga _0.3 Al _0.7 ) _0.5 P (13) into which an n-type dopant (H ₂ Se) is implanted onto the flat (100) plane of the exposed substrate 11 and the p-current blocking layer 22. And p-type dopants such as DMZn (Di-Methyl Zn) or DEZn (Di-Ethyl Zn) and n-type dopants alternately doped on the inclined surface of the P-type current blocking layer 22. In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P layer 21 is formed. N / p / n / p .. In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P layer 21 formed on the inclined surface serves to block current flow.

A p-In0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer 15 is formed on the active layer 14, and a conductive layer 16 and a p-GaAs cap layer are formed on the p-type cladding layer 15. 18) is formed. In addition, an n-type metal electrode 20 is connected to the n-type substrate 11, and a p-type metal electrode 19 is connected to the p-type cap layer 18.

The present invention is not only applied to the InGaP / InGaAlP-based laser diodes, but is also wide in the GaAs / AlGaAs-based, InGaAs / AlGaAs-based, two-, three- and four-way compound semiconductor laser diodes. Can be widely applied.

3 is a cross-sectional view for explaining the operation principle of the present invention, in which the current blocking layer 22 and the current blocking region of n / p / n / p .. are formed so that local oscillation occurs in the active layer formed in the hollow portion. To limit the flow of

Looking at the manufacturing process of the semiconductor laser diode of the present invention shown in FIG. 2 as follows.

First, a p-type GaAs layer is grown on the n-type substrate 11 by primary crystal growth and then etched to form a p-type current blocking layer 22. A portion of the central portion penetrates through the etching process, and the sidewall thereof has a (n11) plane (n ≦ 3).

Subsequently, subsequent collisions are grown to produce subsequent collisions. In this case, the In _0.6 (Ga _0.3 Al _0.7 ) _0.5 P layer, which is first grown in the second crystal, uses a simultaneous doping method, which is characteristic of organometallic vapor phase growth (MOCVD). In other words, the n-type dopant is continuously supplied, but the p-type dopant is intermittently added and grown. In this case, on the (100) plane of the exposed n-type substrate 11 and the flat p-type current blocking layer 22, the dopant is n-type irrespective of the supply of the p-type dopant, while the p-type dopant is etched on the etched slope. While is supplied, it is doped into p-type and grown in the form of n / p / n / p ..

Subsequently, the active layer 14, the p-type cladding layer 15, the conductive layer 16, and the p-type cap layer 18 are formed in a conventional manner, and a metal electrode is attached thereto.

As described above, according to the present invention, a true refractive index waveguide structure due to the bending of the active layer is formed, which is advantageous for single mode oscillation, and the astigmatism distance is also reduced to 5 μm or less.

In addition, due to the current blocking region of n / p / n / p .. type, the current spreading phenomenon is eliminated, thereby increasing the device efficiency and lowering the driving current value.

In addition, the present invention is simple because the production is completed only by the secondary crystal growth process is improved and productivity is also improved.

In addition, according to the manufacturing method of the present invention, there is no problem caused by aluminum oxidation, so it is easy to regrow, and since the selective crystal growth is not performed as in the prior art, it is easy to manufacture, and there is no deterioration of the film quality characteristic by a silicon oxide film or the like.

In addition, deterioration of the device caused by the oscillated beam being absorbed by the current blocking layer is excluded.

The present invention is not limited to the above embodiments, and various modifications and changes can be made within the scope of the technical gist of the present invention as understood from the claims below.

Claims (5)

A first conductive substrate; A second conductive type current blocking layer formed on the first conductive type substrate such that a sidewall thereof forms a constant inclined surface and a bottom surface thereof has a flat through groove left in the center portion of the first conductive type substrate; It is formed in the substrate yarn exposed through the current blocking layer and the through-groove, and the first conductive type impurities are doped on the flat surface to become a current passing region, and the first conductive type / first on the inclined surface A first conductive type first clad layer having a structure in which impurities are doped alternately in the form of two conductivity type / first conductivity type / second conductivity type ... An active layer having a laser oscillation region formed in the through groove portion on the first conductive first clad layer; And a second conductive second cladding layer formed on the active layer. The semiconductor laser diode of claim 1, wherein the active layer / clad layer is any one selected from the group consisting of InGaP / InGaAlP-based, GaAs / AlGaAs-based, InGaAs-based, and InGaAs / InGaP-based. The semiconductor laser diode of claim 1, wherein the inclined surface forms a (n11) plane (n ≦ 3). Forming a current blocking layer by primary crystal growth on the first conductive substrate; Forming a sloping surface having a constant sidewall at a central portion of the current blocking layer and having a flat through groove at a bottom thereof; Secondary crystal growth is carried out on the entire surface of the resultant, and the first conductive type impurities are doped on a flat surface to form a current passing through area. On the inclined surface, the first conductive type / second conductive type / first conductive type / second conductive type Forming a first conductive cladding layer alternately doped to form a current blocking role and recessed into the through groove; Forming an active layer recessed in the through grooves on the result; And forming a second conductive cladding layer on the active layer. The semiconductor laser according to claim 4, wherein the first conductive cladding layer is formed by performing an epitaxial growth process while continuously supplying the first conductive impurity and intermittently supplying the second conductive impurity. Method of manufacturing a diode.