KR100364770B1 - High-power laser diode - Google Patents

Abstract

PURPOSE: A high-power laser diode is provided to increase the size of a beam spot by forming a separate waveguide layer between clad layers over an active layer. CONSTITUTION: A first clad layer(21), an active layer(22), a second clad layer(23), a separate waveguide layer(24), a third clad layer(25), and a cap layer(26) are sequentially deposited on a substrate(20) through an LPE(Liquid Phase Epitaxy) having a higher heat characteristic than an MOCVD(Metal Organic Chemical Vapor Deposition). These layers form a double heterostructure. A mesa structure is formed by selectively etching the cap layer(26), the third clad layer(25), the separate waveguide layer(24), and a second clad layer(23) through a photolithography. A current limiting layer is formed on both laterals of the mesa structure through the MOCVD.

Description

High power laser diode

The present invention relates to high power laser diodes, and more particularly to high power laser diodes having low drive current and high thermal characteristics.

In order to obtain a high power laser diode, the laser diode emits light generated inside the device near the cleaved surface and absorbs the cleaved surface (Catastropic Optical Damage) phenomenon. It must be restrained. The laser diode structure proposed to suppress this COD phenomenon is shown in FIGS. 1 and 2.

The laser diode structure of FIG. 1 has a first cladding layer 2, an active layer 3, a second cladding layer 4, and a cap layer 5 formed on the substrate 1 in the vicinity of the cleavage surface of the lamination structure. NAM (Non Absorbing Mirror) (6) structure is formed. FIG. 1B illustrates a cross-sectional structure along the line AA ′ of FIG. 1.

The laser diode of FIG. 2 has a first cladding layer 2, an active layer 3, a second cladding layer 4 and a cap layer 5 on a special mesa formed by a current limiting layer 7 formed on a substrate 1. In order to form a double hetero structure, the thickness of the active layer (3) in the upper part of the mesa becomes thin, so that the light generated from the active layer is not limited to the active layer of the upper part of the mesa so that the light spreads to both clad layers It was made possible. In other words, the size of the beam spot on the cleaved surface is increased, the optical density is reduced, so that a high output can be obtained. FIG. 2 shows a cross-sectional structure along the line B-B 'of FIG. 1 (a).

In order to implement the NAM structure as shown in FIG. 1, not only the epitaxial growth should be additionally performed to form the NAM, but also the epitaxial growth must be performed on the side or the top of the various boundary layers, so that the uniform growth is difficult and the reproducibility aspect is increased. In addition, there is a problem, and since there is a current loss as much as the NAM region, there is a problem in that the operating current is relatively high.

Although the structure of FIG. 2 is relatively simple to fabricate, the active layer ratio becomes thinner, resulting in a low operation ratio due to a lower light distribution factor (confinement factor) in the active layer compared to the light distribution in all sections. have.

The present invention has been made to solve such a problem, and an object thereof is to provide a high power laser diode having a low driving current and a high thermal characteristic.

The high-power laser diode of the present invention for achieving the above object comprises a substrate, a current limiting layer formed on a predetermined region of the substrate, a first cladding layer, an active layer, a second cladding layer formed in turn on the substrate and the current limiting layer, A laser diode composed of a third cladding layer and a cap layer, wherein the second and third cladding layers have a refractive index smaller than the refractive index of the active layer and larger than the second and third cladding layers, and larger than the energy band gap of the active layer. And a separate optical waveguide layer having an energy bandgap smaller than the energy bandgap of the three cladding layers.

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

3 shows a cross-sectional structure of a high power laser diode according to an embodiment of the present invention.

In the high power laser diode of the present invention, the current limiting layer 11 is formed on a predetermined region of the substrate 10, and the first cladding layer 12, the active layer 13, and the second cladding layer are formed on the substrate and the current limiting layer. 14), the separation optical waveguide layer 15, the third cladding layer 16, and the cap layer 17 are formed in this order.

When the separation optical waveguide layer 15 is formed between the cladding layers 14 and 16 on the active layer 13 as described above, light generated in the active layer is separated from the active layer 13 and the separation optical waveguide layer 15 and between the active layer and the separation optical waveguide layer. Since light is conducted in the cladding layer 14 to increase the beam spot size on the cleaved surface, the light output density becomes high, thereby enabling high power operation.

Since the laser diode structure of the present invention does not cause current loss as in the conventional NAM structure, the operating current is lowered, and the active layer thickness is not as thin as the structure of FIG. 2 using a special mesa structure. As the percentage of light distribution increases, the thermal characteristics are excellent, enabling high power laser diodes to be realized.

In this case, the separated optical waveguide layer is formed of a material having a refractive index smaller than that of the active layer, larger than the lower cladding layer, and an energy bandgap larger than the active layer and smaller than the clad layer.

4 illustrates a high power laser diode structure and a method of manufacturing the same according to another embodiment of the present invention.

First, as shown in FIG. 4A, the first cladding layer 21, the active layer 22, the second cladding layer 23, the separation optical waveguide layer 24, and the third cladding layer 25 are formed on the substrate 20. ) And cap layer 26 to Liquid Phase Epitaxy (LPE) (e.g., AlGaAS laser diode, which has a higher thermal property than Metal Organic Chemical Vapor Deposition (MOCVD), is 200K To and 140K To MOCVD). In order to form a double heterostructure.

Subsequently, a portion of the cap layer 26, the third cladding layer 25, the separation optical waveguide layer 24 and the second cladding layer 23 is selectively etched through a photolithography process as shown in FIG. 4 (b). To form a structure.

Next, as shown in FIG. 4 (c), a high power laser diode is formed by forming current limiting layers 27 on both sides of the mesa structure by secondary growth using MOCVD (Metal Organic Chemical Vapor Deposition) process, which is easy to interfacial growth. To make.

In this manner, the double hetero growth by LPE can form a laser diode having more excellent thermal characteristics having a high thermal characteristic temperature (To).

As described above, the present invention can increase the beam spot size by forming a separate optical waveguide layer between the clad layers on the active layer, the current loss and the light distribution percentage in the active layer compared to the light distribution in all cross sections. The high output laser diode with low driving current and high thermal characteristics can be realized by preventing the decrease of

In addition, since the manufacturing process is simple, the yield at the time of manufacture can be improved.

1 is a structural diagram of a laser diode employing a conventional NAM structure.

2 is a structure diagram of a conventional laser diode

3 is a cross-sectional view of a laser diode according to an embodiment of the present invention.

4 is a process flowchart showing a method of manufacturing a laser diode according to another embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

10,20 Substrate 11,27 Current limiting layer

12,21 First cladding layer 13,22 Active layer

14,23 Second cladding layer 15,24Separated optical waveguide layer

16,25 Third cladding layer 17,26 Cap layer

Claims (6)

A laser diode comprising a substrate, a current limiting layer formed on a predetermined region of the substrate, and a first cladding layer, an active layer, a second cladding layer, a third cladding layer, and a cap layer sequentially formed on the substrate and the current limiting layer. , An energy bandgap between the second and third cladding layers is smaller than the refractive index of the active layer and larger than the second and third cladding layers and is larger than the energy bandgap of the active layer and smaller than the energy bandgap of the second and third cladding layers. The high power laser diode comprising a branched optical waveguide layer The first cladding layer, the active layer, and the second cladding layer, which are sequentially formed on the substrate, and the separation optical waveguide layer, the third cladding layer, and the cap layer, which are sequentially formed on a predetermined region of the second cladding layer to form a mesa structure, Comprising a current limiting layer formed on both sides, the separation optical waveguide layer has a refractive index smaller than the refractive index of the active layer and larger than the refractive index of the second cladding layer and the third cladding layer, larger than the energy band gap of the active layer and the second cladding layer And an energy bandgap smaller than the energy bandgap of the third cladding layer. The high power laser diode of claim 2, wherein the first cladding layer, the active layer, the second cladding layer, the separation optical waveguide layer, the third cladding layer, and the cap layer are formed by an epitaxial growth process to have high thermal characteristics. 4. The high power laser diode of claim 3, wherein the epitaxial growth process is an LPE process. The high power laser diode of claim 2, wherein the current limiting layer is formed by an epitaxial growth process that facilitates interfacial growth. 6. The high power laser diode of claim 5, wherein the epitaxial growth process is MOCVD.