JPS6359279B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a semiconductor laser with a monitor in which a photodetector (monitor) and a laser are formed on the same substrate (chip), and particularly relates to a semiconductor laser with a monitor in which a photodetector (monitor) and a laser are formed on the same substrate (chip). The present invention relates to a semiconductor laser device with a monitor that can achieve optical coupling.

[Prior art]

An example of a conventional semiconductor laser with a monitor of this type has a striped metal electrode attached to a double heterostructure compound semiconductor crystal using InP/InGaAsP, and is perpendicular to the electrode in the center of the crystal. An etched groove is formed in the direction by chemical or physical etching, and one side of the groove is used as a laser and the other side is used as a photodetector. Although the photodetector and the laser have the same cross-sectional structure, they are electrically applied with bias voltages in opposite directions (Applied Physics Letters by B.I. Mira and K. Iga). (BI Miller and K.Iga,
Appl, Phys. Lett., Vol. 37, No. 4, p. 339 (1980)).

Here, if the inclination in the depth direction of the etched end faces of both laser and photodetector facing the groove separating them is not appropriate, the optical coupling between the two will be inappropriate, and the desired function will not be achieved. I can't. That is, if the slope is too large, a sufficient amount of laser output light will not reach the active part of the photodetector, while if it is too small, the two will form a double cavity, resulting in unnecessary interaction (crosstalk). happens. However, in the above-mentioned known example, there is no limitation on the respective inclinations in the depth direction of both end faces facing the groove. However, in reality, as mentioned above, this slope has an important meaning.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide an etched groove portion that can achieve sufficient optical coupling between the laser and the photodetector and at the same time prevent unnecessary interaction between the two. It is an object of the present invention to provide a semiconductor laser with a monitor, in which both end faces facing the surface have an appropriate inclination in the depth direction.

[Summary of the invention]

In order to achieve this object, the semiconductor laser with a monitor of the present invention is characterized by having a groove portion that widens in the depth direction and has an angle of 5° or more and 15° or less with respect to the direction perpendicular to the layer plane of the layered crystal. There is.

That is, by making the inclination of the end faces of the photodetector and the laser facing the groove part 5 degrees or more, the light from the photodetector is prevented from entering the laser back, and at the same time, the inclination is 15 degrees or less. In particular, the design is such that a sufficient amount of light emitted from the laser is projected onto the active layer of the photodetector. Note that this angle limit is -50 for all devices using GaAs/GaAlAs, InP/InGaAsP in the wavelength range of 0.6 to 1.7 μm.
It is derived from Fresnel's law that this applies in the temperature range from ℃ to +100℃.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic cross-sectional view of a semiconductor laser with a monitor according to an embodiment of the present invention. The semiconductor laser with a monitor of this embodiment is constructed by forming a groove as shown in the figure in a double heterostructure crystal made of GaAs/GaAlAs by wet chemical etching. A laser was formed on the same substrate. In this figure, 1 is an n-type GaAs substrate, 2 is an n-type GaAlAs clad layer, 3 is an n-type GaAs active layer,
4 is a P-type GaAlAs clad layer, 5 is a P-type GaAs cap layer, 6 is a metal electrode, 7 is a photodetector (photodetector), 8 is a laser unit (laser), 9 is a groove, 10,
Reference numeral 11 indicates the etched end surfaces of the photodetector section 7 and the laser section 8 facing the groove section 9, and 12 and 13 indicate the etched end surfaces 1.
0.11, that is, the angle formed by the etched end faces 10 and 11 with respect to each layer plane of the layered crystal. The monitor-equipped semiconductor laser of the present invention has etched end faces 10 and 11.
By making the slopes 12 and 13 of 5° or more and 15° or less, the desired purpose could be achieved. In other words, the light receiving efficiency is maintained at 70% or more, and the light detecting section 7
Almost no light reflected inside the laser unit 8 enters back into the laser unit 8, and stable operation without unnecessary interaction is achieved. In addition, in order to obtain a slope of 5° or more and 15° or less, H ₃ PO ₄ :H ₂ O ₂ :
HOCH ₂ CH ₂ OH (ethylene glycol) (1:
Using a solution of 1:3), the etched surface was etched so that the inclination of the etched surface was between 5° and 15° at the position of the active layer (nGaAs active layer 3 in Figure 1). The etching time was carefully controlled while observing.
In addition to this, the etching solution includes NH ₄ OH/H ₂ O ₂ ,
H ₃ PO ₄ /H ₂ O ₂ , Br ₂ /CH ₃ OH, etc. may also be used. Furthermore, the etching solution used to create the groove 9 in the InP/InGaAsP crystal is HCl:
A solution of CH ₃ COOH:H ₂ O ₂ (1:2:1) is good. In either case, since the inclination of the etched surface differs depending on the orientation of the substrate crystal, it is necessary to know in advance the etching characteristics of the surface orientation to be used. In particular, as shown in FIG. 1, when the etched surface is selected in the reverse mesa direction, that is, when a small amount of etching is performed, the cross section becomes a trapezoid 14 that spreads upward, and this angle control is effective. works fine.

As mentioned above, the semiconductor laser with a monitor according to the present invention has an angle of 5° or more with respect to the direction perpendicular to the layer plane of the layered crystal.
By having a groove that widens in the depth direction with an angle of 15 degrees or less, it stabilizes the sensitivity of the photodetector and at the same time stabilizes the laser output, achieving sufficient optical coupling between the two. Unnecessary interaction between the two can be prevented, and output and mode characteristics equivalent to those of a single laser can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor laser with a monitor according to an embodiment of the present invention. 1...n-type GaAs substrate, 2...n-type GaAlAs cladding layer, 3...n-type GaAs active layer, 4...P-type
GaAlAs cladding layer, 5... P-type GaAs cap layer, 6... Metal electrode, 7... Photodetection section, 8... Laser section, 9... Groove section, 10, 11... Etched end surface,
12, 13...Inclination.

Claims (1)

[Claims] 1. In a semiconductor laser with a monitor, which has a photodetecting section and a laser section on the same substrate, which are separated by a groove formed in a part of a layered crystal of a compound semiconductor, the groove is perpendicular to the layer plane of the layered crystal. 1. A semiconductor laser device with a monitor, characterized in that the groove portion widens in the depth direction and has an angle of 5° or more and 15° or less with respect to the direction.