JP2716717B2 - Semiconductor laser device - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial application field) The present invention relates to a semiconductor laser device in a long wavelength band which becomes a light source for optical communication.

(Prior Art) As a semiconductor laser device for optical communication, there is a double heterojunction laser using GaInAsP as an active layer and an InP cladding layer, and devices having various structures have been proposed. GaInAsP
By changing the composition of the GaInAsP crystal in the laser used as the active layer, the oscillation wavelength of the laser light can be freely changed from 0.92 μm to 1.65 μm within the range of lattice matching with the InP substrate crystal. Within this oscillation wavelength, it is the wavelength with the lowest loss of the optical fiber used for optical communication 1.
Since 55 μm and 1.3 μm, which is the wavelength with the smallest dispersion, are included, GaInAsP is used as an ohmic contact layer in a conventional GaInAsP / InP-based semiconductor laser that is a promising semiconductor laser as a light source for optical communication. I was However, GaInAsP is difficult to dope at a high concentration, and it is difficult to lower the device resistance.

(Problems to be Solved by the Invention) As described above, since the conventional semiconductor laser uses the GaInAsP ohmic contact layer, there is a problem that it is difficult to reduce the element resistance.

The present invention uses GaInAsP as an ohmic contact layer, and further includes a GaInAsP
It is an object of the present invention to insert a composition transition layer to resist a semiconductor laser device having a low device resistance.

[Configuration of the invention]

(Means for Solving the Problems) In the semiconductor laser device according to the present invention, the active layer is GaInAs.
The P layer and the cladding layer are composed of an InP layer, and the ohmic contact layer is a duffel heterojunction structure composed of a GaInAsP composition transition layer and a GaInAs layer, and can be manufactured using a combination of materials that lattice-match with InP. In order to lattice match the InP substrate,
The composition x of the ohmic contact layer Ga _1-x In _x As layer is approximately
It must be 0.53.

(Function) According to the present invention, a semiconductor laser having a low device resistance can be manufactured by using a GaInAsP composition transition layer and a GaInAs layer for an ohmic contact layer. can get. GaInAsP active layer, InP
In a semiconductor laser with a cladding layer, the band discontinuity of the conduction band between the ohmic contact layer and the cladding layer is
The relaxation by the composition transition layer suppresses the spread of the injection current at the interface between the ohmic contact layer and the cladding layer. Further, since the GaInAs layer on the GaInAsP composition transition layer has a small barrier with respect to the ohmic electrode and can be doped with a high concentration of impurities, the resistance in the ohmic contact layer decreases.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a semiconductor laser device according to one embodiment. An n-type InP substrate 101 is used, and an n-type InP cladding / buffer layer 102 is about 1 μm thick, and Ga _0.4 In _0.6 As _0.9 P _{0.1 is} activated. The layer 103 is about 0.1 μm, and the p-type InP cladding layer 104 is about 1 μm.
m, p-type GaInAsP composition transition layer 105 is about 0.1 μm, Ga _0.47 In
A double hetero junction in which _0.53 As layers 106 are stacked in an order of about 0.4 μm is formed. Each semiconductor layer is epitaxially grown by metal organic chemical vapor deposition (MOCVD). Next, an active region is formed by etching halfway through the n-type InP cladding layer using the SiO ₂ stripe film having a width of about 1.5 μm as a mask. Next, using the SiO ₂ stripe film as a mask, the active region is buried with a p-type InP layer 107 and an n-type InP layer. For this buried growth, an organic metal growth method is used. TMGa, TMIn, AsH ₃ , and PH ₃ were used as raw materials when the active region and the buried region were grown by metal organic chemical vapor deposition. Finally, the SiO ₂ stripe film is removed, a SiO ₂ film 109 is newly formed in a portion other than the active region, and an n-side ohmic contact 111 is formed by vapor deposition of a metal.
Au / AuGe was used as the n-side ohmic electrode 110, and Au / AuZn was used as the p-type ohmic electrode 111. The length of the cavity formed by cleavage is about 250 μm.

The oscillation threshold current of the semiconductor laser device according to this example was 20 mA, and the differential quantum efficiency was about 32%, and characteristics equivalent to those of the related art were obtained. FIG. 2 shows II-dV of this semiconductor laser.
Shows / dI characteristics. The slope of the straight line is the element resistance Rs (Ω), 1.8
(Ω). As described above, the output can be reduced by 3 (Ω) or more as compared with the conventional value of about 5 to 6 (Ω), whereby the optical output Pmax is 35 mW compared to the conventional 20 mW.

Note that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the scope of the invention. For example, the mesa shape is not limited to an inverted mesa. Further, the composition of the active layer can be changed as appropriate.

〔The invention's effect〕

As described above, according to the present invention, a GaInAsP composition transition layer and a GaI
By using the nAsP layer, a semiconductor laser device having low device resistance and high optical output can be obtained.

[Brief description of the drawings]

FIG. 1 is a structural sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIG.
It is a / dI characteristic diagram. 101: n-type InP substrate, 102: n-type InP, 103: Ga _0.4 In _0.6 As _0.9 P _0.1 , 104: p-type InP, 105: p-type Ga _1-x In _x As _1-y P _y composition transition layer, 106: p-type Ga _0.47 In _0.53 As, 107: p-type InP buried layer, 108: n-type InP buried layer, 109: SiO film, 110: Au / AuGe electrode, 111 ... ... Au / AuZn electrode.

Claims (1)

(57) [Claims] An InP cladding layer is provided on both sides of a GaInAsP active layer, and at least one of the InP cladding layers has a composition x, y from InP to Ga _1-x In _x As under conditions substantially lattice-matched to InP. A semiconductor wherein at least two layers of a Ga _1-x In _x As _1-y P _y composition transition layer and a Ga _1-x In _x As layer are provided, and an electrode layer is provided thereon. Laser element.