JPH0983078A - Semiconductor laser transmitting/receiving element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor laser transmitting/receiving element in which oscillation takes place without causing any supersaturation absorbing phenomenon in the receiving layer. SOLUTION: A light emitting region 14 having a laser active layer 11 is coupled optically with a light receiving region 13 having a light receiving layer 12. Wavelength at the light absorbing end of light receiving layer 12 is set longer than the emission wavelength of laser active layer 11. The light receiving region 13 and the light emitting region 14 are provided individually with electrodes 15, 16 connected through a resistor 17. The resistor 17 is integrated on a semiconductor formed the light receiving region 13 and light emitting region 14 or an external resistor is employed. The electrode 15 in the light receiving region 13 serves as a joint to an external electric circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser transmitting / receiving element used as a transmitting light emitting element and a receiving light receiving element.

[0002]

2. Description of the Related Art In optical communication, a light emitting element such as a semiconductor laser converts an electric signal into an optical signal during transmission, and a light receiving element such as a photodiode converts an optical signal into an electric signal during reception. The semiconductor laser transmission / reception element performs both of these functions by one element, and is a useful element for cost reduction.

The conventional semiconductor laser transmitting / receiving element described in Japanese Patent Laid-Open No. 7-106700 has a laser active layer and a light receiving layer, and oscillates the laser active layer at the time of transmission to generate signal light, and at the time of receiving, the light receiving layer It was structured to receive optical signals. In this semiconductor laser transmitting / receiving element, only one common electrode is provided above the laser active layer and the light receiving layer as a p-side electrode for transmission / reception, and a current is uniformly injected into the laser active layer and the light receiving layer during transmission. .

[0004]

By the way, in the conventional semiconductor laser transmitting / receiving element, since current is uniformly injected into the laser active layer and the light receiving layer during transmission, the light receiving layer functions as a supersaturation absorption region near the threshold current, The optical output rapidly rose, making high-speed transmission difficult. SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor laser transmitting / receiving element capable of oscillating without generating a supersaturated absorption phenomenon of a light receiving layer.

[0005]

FIG. 1 shows a basic structure of a semiconductor laser transmitting / receiving element according to a first aspect of the present invention. The semiconductor laser transmitting / receiving element shown here has a structure in which a light emitting region 14 having a laser active layer 11 and a light receiving region 13 having a light receiving layer 12 are optically coupled. (1) is an example in which the light receiving layer 11 and the laser active layer 12 in the light receiving region 13 have a two-layer structure, and (2) is an example in which the light receiving region 13 is composed of only the light receiving layer 11. The light absorption edge wavelength of the light receiving layer 11 is set to be longer than the emission wavelength of the laser active layer 12. The light receiving area 13 and the light emitting area 14 are individually provided with electrodes 15 and 1 respectively.
6 is arranged, and the electrodes thereof are connected via a resistor 17. The resistor 17 includes a light receiving area 13 and a light emitting area 1.
4 is integrated on the semiconductor forming 4 or an external resistor is used. The electrode 15 of the light receiving region 13 becomes a connection point to an external electric circuit.

FIG. 2 shows the basic structure of the semiconductor laser transmitting / receiving element of claim 2. The semiconductor laser transmitting / receiving element shown here is the same as the semiconductor laser transmitting / receiving element of FIG.
The diffraction grating 18 having the Bragg wavelength set to the emission wavelength of the laser active layer 12 is provided at a predetermined position of the emission region 14. (1) is an example in which the light receiving layer 11 and the laser active layer 12 in the light receiving region 13 have a two-layer structure, and (2)
Is an example in which the light receiving region 13 is composed only of the light receiving layer 11.

FIG. 3 shows an equivalent circuit of the semiconductor laser transmitting / receiving element of the present invention. Here, the capacitance component is ignored. The element resistance during the light emitting operation is a value near the threshold current, which is derived from the IV curve of a typical semiconductor laser.
[Ω]. If the length of the light receiving region 13 is 15 [μm] and the length of the light emitting region 14 is 385 [μm], the resistance area changes without changing the resistivity. Therefore, the element resistance near the threshold current in the light receiving region 13 is changed. Is 5.385 / 15 ≈ 130 [Ω]. Further, the separation resistance of the light receiving area 13 and the light emitting area 14 is R
The resistance value of the resistor 17 was R [Ω].

The electric current at the time of transmission is from the electrode 15 to the light receiving region 1
3 and is injected into the electrode 16 through the resistor 17.
Is injected into the light emitting region 14. At this time, the resistor 17
As shown in FIG. 4, the current density supplied to the light receiving region 13 is larger than that of the light emitting region 14 by increasing the resistance R of the light receiving region 13. For example, by setting R = 5 [Ω], the current density is supplied to the light receiving region 13 at about twice the current density of the light emitting region 14. Even if the separation resistance Rsep of the light receiving region 13 and the light emitting region 14 changes from 100 [Ω] to 2 [kΩ], the current density hardly changes.

As described above, in the light-receiving region 13, sufficient carriers are injected even at a threshold current or less to generate a gain, which is transparent to the oscillation wavelength. Therefore, in the light receiving region 13, even if the threshold current is supplied, a sharp rise of the IL curve due to the absorption of supersaturation is not observed, and the light output can be smoothly increased. This enables high-speed transmission.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 5 shows claims 1 and 3.
2 shows an embodiment of the semiconductor laser transmitting / receiving element of FIG. In the figure, 31 is an n-type InP substrate, 32 is an InGaAsP lower SC.
H layer, 33 is an InGaAsP-MQW active layer, and 34 is InG
aAsP upper SCH layer, 35 is an InP etch stop layer,
36 is an InGaAsP light receiving layer, 37 is a p-type InP cladding layer, 38 is a Fe-InP buried layer, and 39 is a light receiving region p.
Side AuZnNi electrode, 40 is a p-side AuZnNi electrode in the light emitting region, 41 is an n-side AuGeNi electrode, 42 is a Pt resistor, 4
3 is a SiO ₂ insulating film. In the figure, a part is cut away to show the inside. The same applies to the following examples.

A method of manufacturing the semiconductor laser transmitting / receiving element of this embodiment will be briefly described. First, an InGaAsP lower SCH layer 32, an InGaAsP-MQW active layer 33, an InGaAsP upper SCH layer 34, an InP etch stop layer 35, an InGaAsP light receiving layer are formed on an n-type InP substrate 31 by using a metalorganic vapor phase epitaxial growth method. 36 are sequentially formed. Next, a SiO ₂ thin film is formed on the InGaAsP light-receiving layer 36, and a portion of the Si that becomes a light emitting region is formed by photolithography.
The O ₂ thin film is removed, and then In is applied by wet etching.
The GaAsP light receiving layer 36 is removed.

Next, after removing all the SiO ₂ thin film,
A p-type InP clad layer 37 is formed on the entire surface by using a metal organic vapor phase epitaxial growth method. Next, a mesa structure is formed in a stripe shape in order to control the transverse mode. Next, using the metalorganic vapor phase epitaxial growth method, Fe-
An InP buried layer 38 is formed. Next, the SiO ₂ insulating film 43 is formed on the entire surface, and the SiO ₂ insulating film 4 in the stripe portion is formed.
3 is removed by photolithography and wet etching, and a p-side AuZnNi electrode 39 in the light receiving region and a p-side AuZnNi electrode 40 in the light emitting region are formed by lift-off.
Further, a Pt resistor 42 is formed on the semiconductor by lift-off so as to connect each electrode. Next, n-side AuGeN
The i electrode 41 is formed.

Here, the InGaAsP-MQW active layer 33 is formed.
Has a bandgap wavelength (emission wavelength) of 1.3 [μm], and the InGaAsP light-receiving layer 36 has a bandgap wavelength (light absorption edge wavelength) of 1.34 [μm]. The Pt resistor 42 on the semiconductor has a width of 10 [μm], a length of 200 [μm], and a thickness of 400.
[Nm]. In this embodiment, the light receiving area is In
GaAsP-MQW active layer 33 and InGaAsP light receiving layer 36
However, the light receiving region may be composed of only a light receiving layer formed by butt joint growth.

FIG. 6 shows an embodiment of the semiconductor laser transmitting / receiving element according to claims 1 and 4. In this embodiment,
P-side AuZnNi electrode 39 in the light-receiving region and p-side A in the light-emitting region
The uZnNi electrode 40 is characterized in that it is connected via a chip resistor 44. Between the chip resistor 44 and each electrode,
Bonding wires 45 and 46 are used for connection. Others are manufactured by the same method as the structure of FIG.

An optical element having a light receiving region and a light emitting region is enclosed in a package, and the p-side AuZnNi of the light receiving region is enclosed.
The electrode 39 and the p-side AuZnNi electrode 40 in the light emitting region may be individually drawn out, and an external resistor may be connected therebetween. When transmitting a high-speed signal, it is preferable that the resistor is close to each electrode, and the integrated structure shown in FIG. 5 is preferable.

FIG. 7 shows an embodiment of the semiconductor laser transmitting / receiving element according to claims 2 and 3. The present embodiment is characterized in that the diffraction grating 18 is provided at a predetermined position of the InGaAsP-MQW active layer 33 in the configuration of FIG.
This diffraction grating 18 is manufactured by removing the InP etch stop layer 35 only in the light emitting region and removing the InGaAs AsP upper SCH.
The diffraction grating 18 having the Bragg wavelength set to the emission wavelength of the active layer is formed in the layer 34 by an interference exposure method or the like. Others are manufactured by the same method as the structure of FIG.

FIG. 8 shows an embodiment of the semiconductor laser transmitting / receiving element of claims 2 and 4. The present embodiment is characterized in that the InGaAsP-MQW active layer 33 has a diffraction grating 18 at a predetermined position in the configuration of FIG.
The method of manufacturing the diffraction grating 18 is the same as that shown in FIG. Others are manufactured by the same method as the structure of FIG.

In any of the structures shown in FIGS. 5 to 8, oscillation occurred at the bandgap wavelength of the InGaAsP-MQW active layer 33 during transmission, and no supersaturated absorption phenomenon was observed in the IL characteristics. However, the oscillation threshold was increased by 10 to 25% as compared with the semiconductor laser without the absorption layer. Further, at the time of reception, a flat light receiving sensitivity up to the bandgap wavelength of the light receiving layer was obtained.

In the above structure, the MQW is used as the laser active layer.
(Multiple quantum well structure) is used, but a single layer can be operated in the same manner.

[0020]

As described above, in the semiconductor laser transmitting / receiving element of the present invention, the light receiving region becomes transparent to the oscillation wavelength during transmission, and the oscillation operation can be performed without causing the supersaturation absorption phenomenon. This enables high-speed transmission. During reception, almost 100% of light can be absorbed in the light receiving region having a bandgap wavelength longer than that of the light emitting region.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a semiconductor laser transmitting / receiving element according to claim 1.

FIG. 2 is a diagram showing a basic configuration of a semiconductor laser transmitting / receiving element according to claim 2;

FIG. 3 is a diagram showing an equivalent circuit of a semiconductor laser transmitting / receiving element of the present invention.

FIG. 4 is a diagram showing a relationship between a resistance value R of a resistor and a current density.

FIG. 5 is a diagram showing an embodiment of the semiconductor laser transmitting / receiving element according to claims 1 and 3;

FIG. 6 is a diagram showing an embodiment of the semiconductor laser transmitting / receiving element according to claims 1 and 4.

FIG. 7 is a diagram showing an embodiment of the semiconductor laser transmitting / receiving element according to claims 2 and 3;

FIG. 8 is a diagram showing an embodiment of the semiconductor laser transmitting / receiving element according to claim 2 and claim 4;

[Explanation of symbols]

11 light receiving layer 12 laser active layer 13 light receiving area 14 light emitting area 15 and 16 electrode 17 resistor 18 diffraction grating 31 n-type InP substrate 32 InGaAsP lower SCH layer 33 InGaAsP-MQW active layer 34 InGaAsP upper SCH stop layer 35 InP 36 InGaAsP light receiving layer 37 p-type InP clad layer 38 Fe-InP buried layer 39 p-side AuZnNi electrode 40 in light-receiving region p-side AuZnNi electrode 41 in light-emitting region 42 n-side AuGeNi electrode 42 Pt resistor 43 SiO ₂ insulating film 44 , 46 Bonding wire

Claims (4)

[Claims] 1. A light emitting region having a laser active layer, and a light receiving layer optically coupled to the laser active layer,
The light absorption edge wavelength of the light receiving layer is set to a longer wavelength than the light emission wavelength of the laser active layer, the light receiving area and the electrodes individually arranged in the light emitting area, and the electrode of the light receiving area A semiconductor laser transmitting / receiving element, comprising: a resistor connecting to an electrode in the light emitting region, wherein the electrode in the light receiving region serves as a connection point to an external electric circuit. 2. The semiconductor laser transmitter / receiver device according to claim 1, wherein the semiconductor laser transmitter / receiver device has a diffraction grating whose Bragg wavelength is set to the emission wavelength of the laser active layer at a predetermined position in the light emitting region. . 3. The semiconductor laser transmitter / receiver device according to claim 1, wherein a resistor connecting an electrode in the light receiving region and an electrode in the light emitting region is integrated. element. 4. The semiconductor laser transmitter / receiver device according to claim 1, wherein the resistor connecting the electrode in the light receiving region and the electrode in the light emitting region is an external resistor. element.