JP2692557B2 - Manufacturing method of semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser used for optical communication or the like.

[0002]

2. Description of the Related Art Optical fiber communication technology has made remarkable progress in recent years, and large capacity optical communication systems such as 400 Mb / s and 1.6 Gb / s have been introduced not only in Japan but also through foreign countries through submarine cables. ing. A key device indispensable for this optical communication technology is a semiconductor laser that serves as a light source for optical communication. With the increase in distance and capacity of optical communication systems, semiconductor lasers are required to have higher output and higher speed. Further, in recent years, as represented by the term "optical information highway", there is a concept of covering each home with an optical fiber communication network. For this purpose, downsizing of the optical fiber communication system is also important.

A semiconductor laser currently in general use has a structure in which the substrate side is the first electrode and the second electrode is taken out from the epitaxial surface side of the semiconductor. On the other hand, a drive circuit that sends a modulation signal to a semiconductor laser is mainly composed of an electronic device such as a silicon IC. In a general electronic device, a circuit is formed on the surface of a substrate. Therefore, as shown in FIG. 2, the signal line is once taken out from the electronic device to the transmission line and connected to the semiconductor laser by wire bonding. At this time, a method of flip-chip mounting using solder bumps as shown in FIG. 3 is also used in a magazine "Electronic Letters (Electron.
ett. ) Vol. 27, p499, 1991 ". On the other hand, if the electrodes of the semiconductor laser can be taken out from the same surface of the chip, flip chip mounting can be performed on the coplanar transmission line of the electronic device, so wire bonding is unnecessary and the device can be downsized. Furthermore, since the parasitic reactance due to the bonding wire does not occur, high-speed modulation of the semiconductor laser is possible. As a conventional example of the semiconductor laser in which the electrodes are taken out from the same surface of the chip, a method of manufacturing the semiconductor laser by disordering the superlattice, diffusion, ion implantation or the like is well known. In recent years, the magazine "Photonics Technology Letters ((IEEE Photon.Techno
l. Lett. ), Vol. 4, p673, 1992)
4 reports an ultra-high-speed semiconductor laser in which electrodes are taken out from the same surface of a chip as shown in FIG. 4 and pressure-bonded to a probe having a coplanar transmission line for evaluation.

[0004]

The conventional semiconductor laser described above has the following problems. First, in the conventional semiconductor laser in which electrodes are taken out from both sides of the chip as shown in FIGS. 2 and 3, wire bonding with a transmission line is necessary, which makes it difficult to downsize the device. was there. At the same time, there is a problem that the parasitic reactance due to the bonding wire is large and high-speed modulation cannot be performed. On the other hand, there is a problem that it is difficult to control the manufacturing process in the conventional well-known method of manufacturing a semiconductor laser in which electrodes are taken out from the same surface of the chip by disordering or diffusion of superlattice, ion implantation or the like. Further, in the conventional example as shown in FIG. 4, there is a problem that a complicated manufacturing method of two times of mesa etching and three times of crystal growth is required to realize this form.

[0005]

The present invention provides a method for manufacturing a semiconductor laser which solves the above problems, in which an n-type cladding layer, an active layer, a p-type cladding layer,
forming a stripe-shaped first mesa structure in which a p-type contact layer and a cap layer are laminated, and a semiconductor layer laminated in the above step is exposed at a (111) A plane.
A step of forming a second mesa structure in which azimuth planes other than the (111) A plane in stripes parallel to the mesa structure are exposed; and the first and the first while simultaneously supplying p-type impurities and n-type impurities 2. The step of forming a semiconductor layer that covers the side surface of the mesa structure.

[0006]

In the semiconductor laser formed by the manufacturing method of the present invention, the two electrodes are taken out from the same surface of the wafer, so that the semiconductor laser can be easily mounted on the coplanar transmission line and no wire bonding is required. Can be miniaturized. At the same time, since there is no influence of the parasitic reactance due to the bonding wire, high speed modulation is possible. In addition, since the manufacturing method of the present invention does not use disordering of the superlattice, impurity diffusion, ion implantation, etc., the process control is easy and the device manufacturing yield is improved.
Further, the current block structure can be formed by one-time crystal growth, and the pn junction area is small, so that the capacitance is small and high-speed modulation is possible.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor laser according to the present invention will be described in detail with reference to the drawings.

1A and 1B are cross-sectional views for explaining a method for manufacturing a semiconductor laser of the present invention.

First, as a first step, an n-type Inp substrate 1
The n-type InP buffer layer 2, the n-type cladding layer 3, the non-doped InGaAsP active layer 4, the p-type InP cladding layer 5, the p-type InGaAsP contact layer 6, and the non-doped I
The nP cap layer 7 is sequentially grown. Next, a SiO ₂ stripe mask is formed in the (110) direction and a part of InP is formed.
The cap layer 7 is removed and the InGaAsP contact layer 6 is removed.
Expose the surface. After removing the stripe mask,
An SiO ₂ film is again deposited on the entire surface and a stripe-shaped mask 8 having a width of 5 μm is formed by photolithography. Here, mesa etching is performed until the n-type substrate 1 is reached using a brommethanol-based etching solution. At this time, as shown in FIG. 1A, the stripe portion of the InP cap layer 7 immediately below the SiO ₂ mask 8 is (111).
The shape of the inverted mesa exposes the A surface 10. On the other hand, SiO
_{2 In} the stripe portion of the InGaAsP contact layer 6 just below the mask 8, the (111) A plane is not exposed by the side etching of InGaAsP.

Next, in a second step, I was simultaneously doped with Zn as a p-type impurity and Se as an n-type impurity.
Re-grow nP. In this case, as shown in FIG. 1B, In grown on the sidewall surface where the (111) A plane 10 is exposed is grown.
P is Zn in the In site and p-type InP buried layer 1
On the other hand, the InP grown on the portion other than the exposed (111) A surface becomes the n-type InP buried layer 12. Further, since the mesa is masked by the SiO ₂ mask 8, InP does not grow.

Finally, in a third step, the SiO ₂ mask 8 is removed, the InP cap layer 7 on the reverse mesa is removed with an etchant made of hydrochloric acid to expose the InGaAsP contact layer 6, and an etchback method is used. The electrode 13 is formed on the mesa.

The semiconductor laser manufactured by this manufacturing method has both the p-electrode and the n-electrode formed on the epitaxial surface of the wafer and can be mounted on the coplanar transmission line. If it can be mounted on a coplanar transmission line, it can be easily connected to electronic devices, the semiconductor laser device can be downsized, and wire bonding is unnecessary, so high-speed modulation of the semiconductor laser is possible without the influence of parasitic reactance. .

The embodiments of the present invention have been described above, but some supplements will be given below. In the embodiment shown in FIG. 1A, non-doped InGaAsP is used for the active layer 4,
It may be doped, and is not limited to this material as long as it is a material capable of forming a double hetero structure with a cladding layer such as a multiple quantum well. The contact layer 6 is also made of InG.
Although aAsP is used, the material is not limited to this material as long as an ohmic contact is obtained and the etching rate is faster than that of InP for a bromomethanol-based etchant.

[0014]

As described above, according to the present invention, the semiconductor laser can be mounted on the coplanar transmission line. If it can be mounted on a coplanar transmission line, it can be easily connected to electronic devices, the semiconductor laser device can be downsized, and wire bonding is unnecessary, so high-speed modulation of the semiconductor laser is possible without the influence of parasitic reactance. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a method for manufacturing a semiconductor laser of the present invention.

FIG. 2 is a diagram of a conventional semiconductor laser mounting method.

FIG. 3 is a diagram of a conventional method for mounting on a transmission line.

FIG. 4 is a diagram of a conventional method for manufacturing a semiconductor laser that can be mounted on a coplanar transmission line.

[Explanation of symbols]

1 n-type InP substrate 2 n-type InP buffer layer 3 n-type InP clad layer 4 non-doped InGaAsP active layer 5 p-type InP clad layer 6 p-type InGaAsP contact layer 7 non-doped InP cap layer 8 SiO ₂ mask 10 (111) A surface 11 p-type InP buried layer 12 n-type InP buried layer 13 electrode

Claims (1)

(57) [Claims] 1. A step of laminating an n-type clad layer, an active layer, a p-type clad layer, a p-type contact layer, and a cap layer on a semiconductor substrate, and the semiconductor layer laminated by the step is (111) A plane Forming a first stripe-shaped first mesa structure that is exposed, and forming a second mesa structure in which a azimuth plane other than the (111) A plane that is parallel to the first mesa structure is exposed; And a step of forming a semiconductor layer that covers the side surfaces of the first and second mesa structures while simultaneously supplying a type impurity and an n-type impurity.