KR19990025500A - Laser diode and method of manufacturing the same - Google Patents

Abstract

A first conductive clad layer, an active layer, a second conductive type first clad layer, an etch stop layer, a second conductive type clad layer, and a second conductive type clad layer on the first conductive type substrate. A second conductive type InGaP layer and a second conductive type first GaAs layer are successively formed on the first conductive type GaAs layer, a first insulating film pattern is formed on a predetermined region on the second conductive type GaAs layer, and the first insulating film pattern is used as a mask The second conductive type first GaAs layer, the second conductive type InGaP layer, and the second conductive type second clad layer are removed to form a ridge. Then, after the first insulating film pattern is removed and a second conductive type second GaAs layer is formed on the entire surface including the ridge, a second insulating film pattern is formed on the second conductive type second GaAs layer in the ridge region, The second conductive type second GaAs layer is removed to leave the second conductive type second GaAs layer only on the top and both sides of the ridge and then the current is applied to both sides of the second conductive type second GaAs layer with the second insulating film pattern as a mask Thereby selectively forming a barrier layer. Next, by forming the cap layer on the current blocking layer and the second conductive type second GaAs layer by removing the second insulating film pattern, and then forming the electrode on the upper part of the cap layer and the lower part of the substrate, The width of the ridge can be reduced without doing so, which can greatly increase the squareness of the square.

Description

Laser diode and method of manufacturing the same

The present invention relates to a laser diode, and more particularly, to a laser diode having a large square square and a manufacturing method thereof.

Currently visible light semiconductor laser diodes in the 635nm, 650nm and 670nm bands are index waveguide-type using InGap / AlGaInP heterostructure.

The epi structure for fabricating such a semiconductor laser diode is generally designed to avoid a superlattice structure naturally occurring during crystal growth and to obtain a shorter wavelength in a shorter period of time For example, 9 degrees, 15 degrees) on a misoriented substrate.

Therefore, if a ridge is formed using a wet etching process in the fabrication of a device, an asymmetrical shape is formed due to the influence of the substrate.

As a result, the size of the square of the square of the laser diode is reduced and the stability of the mode is lowered.

In addition, it has a considerable influence on mass productivity and yield increase due to unstable wet etching.

The conventional laser diode having the above-described problems will be described in more detail with reference to the drawings.

1 is an index guided AlGaInP laser structure which is a widely used SBR (Selectively Buried Ridge) waveguide laser diode fabricated by wet etching.

Here, in order to maintain a uniform thickness t, an etch stop layer having a thickness of several tens of angstroms has been developed as shown in FIG.

It is indispensable that the thickness t is an important factor that affects the mode characteristics, optical characteristics and current characteristics of the laser constantly.

The SBR structure as shown in FIG. 2 has a great merit in manufacturing simplicity, but has a structural problem in manufacturing.

That is, since the ridge is formed by wet etching using the insulating film as a mask, as shown in FIG. 2, a large difference between the top ridge width W _T and the bottom ridge width W _B A difference occurs and an asymmetrical shape such as an angle a and an angle b occurs due to the characteristics of the substrate.

Here, the magnitude of W _T is related to the oscillation initiation current (I _th ) of the current characteristics, and the magnitude of W _B is closely related to the characteristics of the optical characteristics, especially the parallel far-field angle.

In the SBR structure, the magnitude of the insulating film is adjusted and the magnitude of W _T and W _B is adjusted. Since there is a trade-off between the oscillation starting current and the square of squareness between W _T and W _B , It is necessary to make a ridge structure.

That is, in order to increase the number m square is W _B should be less, which W _T also more reduced eventually W _T is surface reduces below one size oscillation start current is rapidly increased is limited to the size of W _B occurs because .

On the contrary, in order to reduce the oscillation starting current, W _T must be large, which results in increasing the magnitude of W _B , thereby reducing the squared square.

In order to overcome these problems, as shown in FIG. 3, many researches have been conducted to construct a vertical ridge structure using reactive ion etching.

Reactive ion etching is a symmetric and vertical ridge structure easily realized in an epitaxial structure grown on a misoriented wafer by anisotropic etching, and etching depth control is easier than wet etching, and there are various advantages in device manufacturing Because.

As shown in FIG. 3, the difference between W _T and W _B can not be compared with the ridge structure using the wet etching shown in FIG. 2, and the above-mentioned characteristics can be satisfied.

However, even when reactive ion etching is used, the ridge width can not be made infinitely small.

This is because W _T (current injection width) is narrowed as the ridge width is reduced. Therefore, high-temperature operation and high-power operation of the laser diode become difficult due to an increase in the resistance and an increase in the oscillation start current.

The conventional laser diode has the following problems.

Laser diodes fabricated by wet etching have asymmetrical ridge shapes, which reduce the size of the rectangular square and decrease the stability of the mode.

And laser diodes fabricated using reactive ion etching are difficult to operate at high temperature and high power due to limit of ridge width.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a laser diode having a large square square by improving the disadvantages of the ridge structure using wet etching and the ridge structure using reactive ion etching.

1 to 3 are cross-sectional views showing a laser diode according to the prior art

4A to 4F are process cross-sectional views showing a manufacturing process of a laser diode according to the present invention

DESCRIPTION OF THE REFERENCE NUMERALS

11: n-type GaAs substrate 12: n-type GaAs buffer layer

13: n-type AlGaInP cladding layer 14: active layer

15: p-type primary AlGaInP cladding layer 16: p-type InGaP etch stop layer

17: p-type secondary AlGaInP cladding layer 18: p-type InGaP layer

19: p-type first GaAs layer 20: first insulating film

21: p-type second GaAs layer 22: second insulating film

23: n-type GaAs current blocking layer 24: p-type GaAs cap layer

25: p-type electrode 26: n-type electrode

The feature of the laser diode according to the present invention is that the laser diode has epitaxial layers formed on a substrate, an active layer formed therebetween, a ridge formed in a predetermined region of the epilayer, and ridge portions formed on the ridge upper and both sides A current blocking layer formed on both sides of the current conduction path, a cap layer formed on the current blocking layer and the current conduction path, and an electrode formed on the cap layer and below the substrate.

Another feature of the laser diode according to the present invention resides in that it includes a first conductive cladding layer and a second conductive-type cladding layer formed on a substrate, an active layer formed therebetween, and a second conductive- A second conductive type second cladding layer, a second conductive type InGaP layer, and a second conductive type first GaAs layer are sequentially formed on a predetermined region of the upper portion of the etch stop layer; A current blocking layer formed on both sides of the second conductive type second GaAs layer; a cap layer formed on the current blocking layer and the second conductive type second GaAs layer; And an electrode formed on the top of the cap layer and the bottom of the substrate.

The method of manufacturing a laser diode according to the present invention is characterized in that a first conductive type clad layer, an active layer, a second conductive type first clad layer, an etch stop layer, a second conductive type second clad layer, A step of forming a second conductive type InGaP layer and a second conductive type first GaAs layer in this order; forming a first insulating film pattern on a predetermined region on the second conductive type GaAs layer; Forming a ridge by removing the first GaAs layer, the second conductive InGaP layer, and the second conductive type second cladding layer; removing the first insulating film pattern to form a second conductive type second GaAs layer Forming a second insulating film pattern on the second conductive type second GaAs layer in the ridge region and removing the second conductive type second GaAs layer using the second insulating film pattern as a mask to form the second insulating film pattern on the upper and both sides of the ridge Leaving a second conductivity type second GaAs layer; Selectively forming a current blocking layer on both sides of the second conductive type second GaAs layer using the film pattern as a mask; removing the second insulating film pattern to form a cap layer on the current blocking layer and the second conductive type second GaAs layer And a step of forming electrodes on the upper portion of the cap layer and the lower portion of the substrate, respectively.

A laser diode and a manufacturing method thereof according to the present invention having the above-described characteristics will now be described with reference to the accompanying drawings.

4A to 4F are cross-sectional views illustrating a manufacturing process of a laser diode according to the present invention. As shown in FIG. 4A, an n-type GaAs buffer layer 12, an n-type AlGaInP cladding layer Type AlGaInP cladding layer 13, the p-type primary AlGaInP cladding layer 15, the p-type InGaP etch stop layer 16, the p-type secondary AlGaInP cladding layer 17, the p-type InGaP layer 18, Type first GaAs layer 19 are successively grown.

Next, as shown in FIG. 4B, a first insulating layer 20 is formed on the p-type first GaAs layer 19 and patterned to form a p-type first GaAs layer 19).

Here, the first insulating film 20 is formed of SiO ₂ or SiN _x .

Then, the p-type first GaAs layer 19, the p-type InGaP layer 18, the p-type second AlGaInP clad layer 17 exposed by reactive ion etching or wet etching using the patterned first insulating film 20 as a mask, To form a ridge.

Next, as shown in FIG. 4C, the remaining first insulating layer 20 is removed, and a p-type second GaAs layer 21 is formed on the entire surface including the ridge.

4D, a second insulating layer 22 pattern is formed on the p-type second GaAs layer 21 in the upper portion of the ridge, and the second insulating layer 22 is patterned by reactive ion etching After removing a portion of the p-type second GaAs layer 21, the p-type second GaAs layer 21 remaining in the wet etching process is removed to remove the damage layer on the surface caused by the reactive ion etching Leaving only the p-type second GaAs layer 21 on the top and both sides of the ridge.

4E, an n-type GaAs current blocking layer 23 is formed on both sides of the p-type second GaAs layer 21 by selective growth, and then a pattern of the second insulating layer 22 is formed Remove.

When the n-type GaAs current blocking layer 23 is formed, the pattern of the second insulating film 22 is removed in addition to the above method, and an n-type GaAs current blocking layer (not shown) is formed on the entire surface including the p- 23 may be formed and then a portion of the n-type GaAs current blocking layer 23 may be removed by an etching process so that the upper portion of the p-type second GaAs layer 21 is exposed to form an electric current path .

4F, after the p-type GaAs cap layer 24 is formed on the entire surface including the n-type GaAs current blocking layer 23, a p-type electrode 25 is formed on the p-type GaAs cap layer 24, And an n-type electrode 26 is formed under the n-type GaAs substrate 11 to fabricate a laser diode.

The operation of the laser diode of the present invention will now be described.

First, as shown in FIG. 4F, when a bias is applied to both electrodes, holes flow into the open portion of the Li layer due to the influence of the n-type GaAs current blocking layer 23 I will enter.

These holes flow into the active layer 14 through the p-type second GaAs layer 21 on both sides of the ridge portion and the ridge portion as indicated by arrows.

The electrons flow from the n-type AlGaInP cladding layer 13 into the active layer 14, light is generated by recombination in the active layer 14, is amplified by a mirror formed on both sides of the laser diode, lasing occurs.

On the other hand, in the guiding aspect of light, it is almost the same as the conventional structure, but in the conventional case, both sides of the ridge are the n-type GaAs current blocking layer. On the other hand, the present invention is characterized in that both sides of the ridge are formed of the p- GaAs current blocking layer 23 are formed at the same time.

However, since the wavelength of the laser beam is about 630 to 650 nm, the absorption of light occurs in the same manner as in the conventional structure, and the guiding is the same as in the related art.

Therefore, the present invention can reduce the ridge width without increasing the resistance and the oscillation starting current in order to increase the square of the square.

That is, according to the present invention, by forming the p-type second GaAs layer 21 on both sides of the ridge to form the current path, it is possible to prevent an increase in the resistance and an increase in the oscillation start current due to the decrease in the ridge width.

Further, the p-type second GaAs layer 21, which is a current path, can also compensate the low current conductivity of the AlGaInP system to some extent by allowing current to flow into the side surface of the p-type secondary AlGaInP cladding layer 17 of the ridge, To reduce series resistance.

The laser diode according to the present invention and its manufacturing method have the following effects.

Increasing Resistance The ridge width can be reduced without causing an increase in the starting current of the oscillation, which can greatly increase the squared square.

Claims (5)

In a laser diode having an active layer between epitaxial layers formed on a substrate, A ridge formed in a predetermined region of the epilayer; A current conduction path formed on the top and both sides of the ridge excluding the front and back sides of the ridge; A current blocking layer formed on both sides of the current conduction path; A cap layer formed on the current blocking layer and the current path; And an electrode formed on the upper portion of the cap layer and the lower portion of the substrate. In a laser diode having an active layer between a first conductivity type cladding layer formed on a substrate and a second conductivity type first cladding layer, An etch stop layer formed on the second conductive type first clad layer; A second conductive type second cladding layer, a second conductive InGaP layer, and a second conductive type first GaAs layer sequentially formed on a predetermined region of the etch stop layer; A second conductive type second GaAs layer formed on the ridge upper and both sides with a predetermined thickness; A current blocking layer formed on both sides of the second conductive type second GaAs layer; A cap layer formed on the current blocking layer and the second conductive type second GaAs layer; And an electrode formed on the upper portion of the cap layer and the lower portion of the substrate. The first conductive type clad layer, the active layer, the second conductive type first clad layer, the etching stop layer, the second conductive type second clad layer, the second conductive type InGaP layer, the second conductive type clad layer, 1 GaAs layer sequentially; Forming a first insulating film pattern on a predetermined region of the second conductive type GaAs layer; forming a second insulating film pattern on the second conductive type GaAs layer, the second conductive type InGaP layer, Removing the layer to form a ridge; Removing the first insulating film pattern and forming a second conductive type second GaAs layer on the entire surface including the ridge; A second insulating layer pattern is formed on the second conductive type second GaAs layer of the ridge region and the second conductive type second GaAs layer is removed using the second insulating layer pattern as a mask so that the second conductive type second GaAs layer is formed only on the upper and both sides of the ridge, Leaving a second GaAs layer; Selectively forming a current blocking layer on both sides of the second conductive type second GaAs layer using the second insulating film pattern as a mask; Removing the second insulating film pattern to form a cap layer on the current blocking layer and the second conductive type second GaAs layer; And forming electrodes on the upper portion of the cap layer and the lower portion of the substrate, respectively. The method of claim 3, wherein the first and second insulating films are SiO ₂ or SiN _x . The method of claim 3, wherein the current blocking layer is formed by removing the second insulating layer pattern, forming a current blocking layer on the entire surface, and removing the current blocking layer to expose an upper portion of the second conductive type second GaAs layer Wherein the laser diode is fabricated.