JP2005159073A - Semiconductor laser element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser element having laser characteristic assuring excellent reproducibility and a manufacturing method for the same. <P>SOLUTION: The semiconductor laser element 1 comprises a first conductivity type clad layer 4; an active layer 5; a first second conductivity type clad layer 6; a second conductivity type etching stop layer 7 which is thinner in the periphery than the center area; a rectangular ridge 10 composed of a second conductivity type clad layer 8, and a second conductivity type cap layer 9 formed at the center of the second conductivity type etching stop layer 7; a pair of first conductivity type current pinching layers 11, 11 for holding the ridge 10, and a second conductivity type contact layer 12 laminated on the ridge 10; and a pair of first conductivity type current pinching layers 11, 11. In the semiconductor laser element 1, the second conductivity type etching stop layer 7 is formed of a material which is the same as those of a pair of first conductivity type current pinching layers 11, 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal confinement type semiconductor laser device having a current confinement layer and a method for manufacturing the same.

  As the writing speed of DVD-R / RW devices increases, it is desired to increase the output of semiconductor laser elements. In order to suppress kinks generated during the operation of the semiconductor laser element, a method for suppressing an increase in the equivalent refractive index inside and outside the waveguide and a narrowing of the ridge portion serving as the waveguide are effective. In general, since the fabrication is easy, the ridge portion is narrowed. In this case, the kink level is not sufficiently increased due to heat generation due to an increase in series resistance. For this reason, it has been considered to increase the kink level by improving the perpendicularity of the ridge portion.

As such a semiconductor laser device, there is one described in Non-Patent Document 1.
That is, in Non-Patent Document 1, when a semiconductor laser device having a ridge portion whose both side surfaces are vertical is manufactured, when the ambient temperature is 5 to 25 ° C., the kink level is 300 mW or more, and 40 to 80 degrees. In the case of the above, it is described that the kinematic operation is not recognized up to 210 to 280 mW and the operation is stable.

64th Joint Physics Conference / Preliminary Proceedings NO.3 / p1046 / 31a-YC-11

However, it has been difficult to produce both sides of the ridge vertically with good reproducibility.
This will be described with reference to FIG.
FIG. 3 is an enlarged cross-sectional view of the conventional method for manufacturing a semiconductor laser device (ridge forming step).
The formation of the ridge portion 17 will be described.
An n-type GaAs buffer layer 3, an n-type Al _0.5 Ga _0.5 As clad layer 4, a non-doped MQW active layer 5, a first p-type Al _0.5 Ga _0.5 As clad layer 6, a p-type Al _0.7 Ga on the n-type GaAs substrate 2. After sequentially forming a _0.3 As etching stop layer 7, a second p-type Al _0.5 Ga _0.5 As cladding layer 8, a p-type GaAs cap layer 9 and a central portion of the p-type GaAs cap layer 9, an SiO ₂ pattern 18 is formed. Except for being covered with the _two patterns 18, the p-type Al _0.7 Ga _0.3 As etching stop layer 7 is dry-etched to just before it and stopped.

little to stop short of the p-type Al _0.7 Ga _0.3 As etch stop layer 7, p-type Al _0.7 Ga _0.3 As etch stop layer 7, since 0.03μm as thin as about, p-type Al _0.7 Ga _0.3 by dry etching This is because the As etching stop layer 7 may also be removed by etching.
Thereafter, using a selective etching solution, only the second p-type Al _0.5 Ga _0.5 As cladding layer 8 remaining on the p-type Al _0.7 Ga _0.3 As etching stop layer 7 is removed, and the ridge shown in FIG. A portion 17 is formed.

At this time, a residue 19 due to dry etching is generated below the ridge portion 17 in the vicinity of the p-type Al _0.7 Ga _0.3 As etching stop layer 7. The shape of the residue 19 is different every time dry etching is performed and there is no reproducibility. For this reason, when the semiconductor laser element is operated, the drive current flows through the residue 19 portion, resulting in variations in laser characteristics. As a result, a semiconductor laser element with uniform laser characteristics could not be produced with good reproducibility.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a semiconductor laser device having laser characteristics with good reproducibility and a manufacturing method thereof.

According to a first aspect of the present invention, there is provided a first conductivity type cladding layer, an active layer, a first second conductivity type cladding layer, and a peripheral portion which are formed on a first conductivity type substrate sequentially than a central portion. A rectangular ridge portion comprising a thin second conductivity type etching stop layer, a second second conductivity type cladding layer and a second conductivity type cap layer formed at the center of the second conductivity type etching stop layer, and A semiconductor laser comprising: a pair of first conductivity type current confinement layers that sandwich the ridge portion; and a second conductivity type contact layer stacked on the ridge portions and the pair of first conductivity type current confinement layers. In the element
The second conductivity type etching stop layer is made of a material having the same composition as that of the pair of first conductivity type current confinement layers.
According to a second aspect of the present invention, a first conductivity type cladding layer, an active layer, a first second conductivity type cladding layer, and a second conductivity type etching stop layer are sequentially formed on a first conductivity type substrate, and the second conductivity type is formed. A ridge portion is formed on the etching stop layer, and a pair of first conductivity type current confinement layers sandwiching the ridge portion is formed on the second conductivity type etching stop layer, and the ridge portion and the pair of first first layers are formed. In a method for manufacturing a semiconductor laser device, wherein a second conductivity type contact layer is formed on a conductivity type current confinement layer,
The ridge portion is formed by sequentially forming a second second-conductivity-type cladding layer, a second-conductivity-type cap layer, and an insulating layer on the second-conductivity-type etching stop layer, and a photoresist pattern is formed in the central portion of the insulating layer. A method of manufacturing a semiconductor laser device comprising: forming a rectangular shape by dry etching from the insulating layer to the middle of the second conductivity type etching stop layer except for being covered with the photoresist pattern I will provide a.

  According to the present invention, since the second conductivity type etching stop layer is made of a material having the same composition as that of the pair of first conductivity type current confinement layers, it is possible to obtain a semiconductor laser device with good reproducibility and uniform laser characteristics. it can.

An embodiment of a semiconductor laser device and a manufacturing method thereof according to the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing an embodiment of a semiconductor laser device of the present invention.
2A and 2B show a method for manufacturing a semiconductor laser device according to an embodiment of the present invention, wherein FIG. 2A is a (first step), FIG. 2B is a second step, FIG. 2C is a third step, D) is a sectional view of (fourth step).
The same components as those of the conventional technology are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 1, a semiconductor laser device 1 includes an n-type GaAs buffer layer 3 doped with 1 × 10 ¹⁸ cm ⁻³ Si on an n-type GaAs substrate 2 and 1 × 10 ¹⁸ cm ⁻³ Si. Doped n-type Al _0.5 Ga _0.5 As cladding layer 4, non-doped MQW active layer 5 (hereinafter simply referred to as active layer 5), and first p-type Al _0.5 Ga doped with 5 × 10 ¹⁷ cm ⁻³ Zn. _{A 0.5} As cladding layer 6 and a p-type Al _0.7 Ga _0.3 As etching stop layer 7 in which the peripheral portion 7b doped with Zn of 1 × 10 ¹⁸ cm ⁻³ is thinner than the central portion 7a are sequentially stacked. The active layer 5 has, for example, a double quantum well structure and includes a non-doped Al _0.9 Ga _0.1 As well layer and a non-doped Al _0.3 Ga _0.7 As barrier layer. The n-type Al _0.5 Ga _0.5 As clad layer 4, the active layer 5, and the first p-type Al _0.5 Ga _0.5 As clad layer 6 form a double heterojunction structure.

Further, a second p-type Al _0.5 Ga _0.5 As cladding layer 8 doped with 1 × 10 ¹⁸ cm ⁻³ of Zn is formed on the central portion 7a of the p-type Al _0.7 Ga _0.3 As etching stop layer 7, and 2 × A rectangular ridge portion 10 is formed by sequentially laminating a thin p-type GaAs cap layer 9 doped with 10 ¹⁸ cm ⁻³ of Zn. Here, in order not to increase the series resistance, and p-type Al _0.7 Ga _0.3 As etch stop layer 7 during dry etching to be described later from being etched away, a p-type Al _0.7 Ga _0.3 As etch stop layer 7 Has a thickness of 0.1 to 0.3 μm.

Furthermore, a pair of n-type Al _0.7 Ga _0.3 As doped with 1 × 10 ¹⁸ cm ⁻³ sandwiching the ridge portion 10 formed on the central portion 7 a of the p-type Al _0.7 Ga _0.3 As etching stop layer 7. Current confinement layers 11, 11, and a p-type GaAs contact layer doped with 2 × 10 ¹⁸ cm ⁻³ Zn formed on ridge portion 10 and a pair of n-type Al _0.7 Ga _0.3 As current confinement layers 11, 11. 12 are formed. Since the composition of the pair of n-type Al _0.7 Ga _0.3 As current confinement layers 11 and 11 is the same as that of the p-type Al _0.7 Ga _0.3 As etching stop layer 7, an excellent lattice-matched junction can be obtained.

  An Au-based p-type ohmic electrode 13 is formed on the p-type GaAs contact layer 12, and an Au-based n-type ohmic electrode 14 is formed on the n-type GaAs substrate 2 opposite to the stacking direction.

  The semiconductor laser element 1 injects a forward current from the p-type ohmic electrode 13 side to the n-type ohmic electrode 14 side, and when this current becomes equal to or higher than the oscillation threshold, the activity corresponding to the lower portion of the ridge portion 10 Laser light is emitted from the layer 5.

As described above, according to the present invention, the p-type Al _0.7 Ga _0.3 As etching stop layer 7 is made of a material having the same composition as the pair of n-type Al _0.7 Ga _0.3 As current confinement layers 11, 11. Since it has a thickness of 1 to 0.3 μm, it is possible to obtain the semiconductor laser device 1 having laser characteristics that are easy to manufacture and have good reproducibility.

Next, the manufacturing method will be described with reference to FIG.
(First step)
As shown in FIG. 2A, an n-type doped with 1 × 10 ¹⁸ cm ⁻³ of Si on the n-type GaAs substrate 2 by performing the first growth by MOCVD (Metal Organic Chemical Deposition) method. GaAs buffer layer 3, n-type Al _0.5 Ga _0.5 As cladding layer 4 doped with 1 × 10 ¹⁸ cm ⁻³ Si, active layer 5, and first doped with 5 × 10 ¹⁷ cm ⁻³ Zn a p-type Al _0.5 Ga _0.5 as cladding layer 6, and 1 × 10 ¹⁸ cm p-type doped with Zn of ^-3 Al _0.7 Ga _0.3 as etch stop layer 7, the doped with Zn of 1 × 10 ¹⁸ cm ^-3 Two p-type Al _0.5 Ga _0.5 As cladding layers 8 and a thin p-type GaAs cap layer 9 doped with 2 × 10 ¹⁸ cm ⁻³ Zn are sequentially stacked. At this time, the thickness of the p-type Al _0.7 Ga _0.3 As etching stop layer 7 is 0.1 to _0.3 μm.

(Second step)
Next, as shown in FIG. 2B, an insulating layer 15 and a photoresist are sequentially formed on the p-type GaAs cap layer 9, and then a photoresist pattern 16 that leaves the central portion of the photoresist by photolithography is formed. Form. Further, the insulating layer 15 other than that covered with the photoresist pattern 16 is removed by etching. Then, dry etching is performed from the p-type GaAs cap layer 9 exposed from the insulating layer 15 and the photoresist pattern 16 to the middle of the p-type Al _0.7 Ga _0.3 As etching stop layer 7 and stopped. Dry etching of p-type Al _0.7 Ga _0.3 As etch stop layer 7 can be performed at an etching rate of several tens of Å / sec, the thickness of the p-type Al _0.7 Ga _0.3 As etch stop layer 7, 0.1 Since it is as thick as ˜0.3 μm, it can be stopped in the middle of the thickness.

Thereafter, similarly to the conventional method, the damaged layer on the p-type Al _0.7 Ga _0.3 As etching stop layer 7 generated by dry etching is removed by etching using a selective etching solution. The damaged layer is etched by about 0.01 μm.
When each semiconductor layer is etched by dry etching, each semiconductor layer can be etched vertically, so that the ridge portion 10 thus obtained has a rectangular shape. As a result, the p-type Al _0.7 Ga _0.3 As etching stop layer 7 has a peripheral portion 7b thinner than the central portion 7a.

(Third step)
Next, as shown in FIG. 2C, after removing the photoresist pattern 16, the second growth is performed by MOCVD, and 1 × 10 ¹⁸ cm ⁻³ of Si sandwiching the ridge portion 10 is doped. The paired n-type Al _0.7 Ga _0.3 As current confinement layers 11 and 11 are formed. At this time, no growth is performed on the insulating layer 15. The pair of n-type Al _0.7 Ga _0.3 As current confinement layers 11, 11 have the same composition as the p-type Al _0.7 Ga _0.3 As etching stop layer 7, and only the conductivity type is different.

(4th process)
Next, as shown in FIG. 2D, after the insulating layer 15 is removed, the third growth is performed by the MOCVD method, and the p-type GaAs cap layer 9 of the ridge portion 10 and the pair of n-type Al _0.7 Ga. A p-type GaAs contact layer 12 doped with 2 × 10 ¹⁸ cm ⁻³ Zn is sequentially laminated on the _0.3 As current confinement layers 11 and 11.

Thereafter, an Au-based p-type ohmic electrode 13 is formed on the p-type GaAs contact layer 12, and an Au-based n-type ohmic electrode 14 is formed on the n-type GaAs substrate 2 opposite to the stacking direction.
Thus, the semiconductor laser device 1 shown in FIG. 1 is manufactured.

Since the rectangular ridge portion 10 is formed by dry etching from the p-type GaAs cap layer 9 to the middle of the p-type Al _0.7 Ga _0.3 As etching stop layer 7, a current flows only through the ridge portion 10 during operation. For this reason, it is easy to manufacture, and a semiconductor laser element having reproducible laser characteristics can be manufactured.
The embodiment of the present invention is not limited to the above, and can be applied to semiconductor laser elements other than AlGaAs as long as it is an internal confinement semiconductor laser element.

  The present invention can be applied to an optical pickup device or an optical measurement application when reading information from an optical recording medium.

It is sectional drawing of the semiconductor laser element of embodiment of this invention. 1A and 1B show a method for manufacturing a semiconductor laser device according to an embodiment of the present invention, in which FIG. 1A is a (first step), FIG. 1B is a second step, FIG. 3C is a third step, and FIG. It is sectional drawing of a 4th process. It is an expanded sectional view in the (ridge part formation process) of the manufacturing method of the conventional semiconductor laser element.

Explanation of symbols

1 ... semiconductor laser device, 2 ... n-type GaAs substrate (first conductivity type substrate), 3 ... n-type GaAs buffer layer, 4 ... n-type Al _0.5 Ga _0.5 As cladding layer (the first conductivity type cladding layer), 5 ... Active layer, 6... First p-type Al _0.5 Ga _0.5 As cladding layer (first second conductivity type cladding layer), 7... P-type Al _0.7 Ga _0.3 As etching stop layer, 8. _0.5 Ga _0.5 As cladding layer, 9 ... p-type GaAs cap layer, 10 ... ridge portion, 11 ... n-type Al _0.7 Ga _0.3 As current confinement layer (first conductivity type current confinement layer), 12 ... p-type GaAs contact layer ( Second conductivity type contact layer), 13 ... p-type ohmic electrode, 14 ... n-type ohmic electrode, 15 ... insulating layer, 16 ... photoresist pattern

Claims (2)

A first conductivity type cladding layer sequentially formed on the first conductivity type substrate; an active layer; a first second conductivity type cladding layer; a second conductivity type etching stop layer whose peripheral portion is thinner than the central portion; A rectangular ridge portion formed of a second second-conductivity-type cladding layer and a second-conductivity-type cap layer formed in a central portion of the second-conductivity-type etching stop layer, and a pair of sandwiching the ridge portion In a semiconductor laser device comprising: a first conductivity type current confinement layer; and a ridge portion and a second conductivity type contact layer stacked on the pair of first conductivity type current confinement layers,
The second conductivity type etching stop layer is made of a material having the same composition as that of the pair of first conductivity type current confinement layers. A first conductivity type cladding layer, an active layer, a first second conductivity type cladding layer, and a second conductivity type etching stop layer are sequentially formed on the first conductivity type substrate, and a ridge is formed on the second conductivity type etching stop layer. A pair of first conductivity type current confinement layers sandwiching the ridge portion on the second conductivity type etching stop layer, and the ridge portion and the pair of first conductivity type current confinement layers. In the method of manufacturing a semiconductor laser device, in which the second conductivity type contact layer is formed
The ridge portion is formed by sequentially forming a second second-conductivity-type cladding layer, a second-conductivity-type cap layer, and an insulating layer on the second-conductivity-type etching stop layer, and a photoresist pattern is formed in the central portion of the insulating layer. A method of manufacturing a semiconductor laser device comprising: forming a rectangular shape by dry etching from the insulating layer to the middle of the second conductivity type etching stop layer except for being covered with the photoresist pattern .

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