JP2812069B2 - 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 semiconductor laser,
In particular, the present invention relates to a multi-beam semiconductor laser in which a plurality of laser resonators having an independently driven structure are formed in a laser chip.

[0002]

2. Description of the Related Art Recently, multi-beam semiconductor lasers have been used as high-output light sources for laser printers, optical disks, and the like. This type of multi-beam semiconductor laser has a plurality of laser resonators of an independent drive structure in a laser chip, unlike a semiconductor laser in which a plurality of laser resonators are simultaneously driven by a common electrode for high output. .

FIG. 6 is a cross-sectional structural view of a chip of this type of multi-beam semiconductor laser, in which a first buffer layer 11, a first cladding layer 12, and an active layer 1 are formed on a semiconductor substrate 10.
3, the second cladding layer 14 and the second buffer layer 15 are formed in this order, and the second buffer layer 15 and the second cladding layer 14 are mesa-etched to form a plurality (two in FIG. 6) of stripes. Has formed an area. These stripe regions are separated at predetermined intervals by current block layers 16a to 16c, and contact layers 18a and 18b separated by a resist layer 17 are formed on the surfaces of these layers.
In addition, the p-electrode 19
a, 19b and a common n-electrode 19c on the lower surface of the semiconductor substrate 10.
Are formed. The first and second buffer layers 1
Reference numerals 1 and 15 denote a semiconductor substrate 10 and a second cladding layer 1, respectively.
There is also a structure that is integrated with No. 4 and does not exist independently.

In the above structure, conventionally, an n-type (first conductivity type, hereinafter the same) GaAs mixed crystal is usually formed on the semiconductor substrate 10, an n-type III-V mixed crystal is formed on the first cladding layer 12, and an active layer is formed. 13, a mixed crystal of undoped III-V atoms, a mixed crystal of p-type (second conductivity type, the same applies hereinafter) III-V atoms for the second cladding layer 14, and a GaAs mixed crystal for the current blocking layer. .

In the multi-beam semiconductor laser having such a structure, when a current flows in the vertical direction of FIG.
Carriers from 19b are current blocking layers 16a to 16c
And moves through the second cladding layer 14 through the upper surface of each stripe region. At that time, the carrier
An electric field distributes the beam from the second cladding layer 14 to the n-common electrode 19c across the active layer 13 and the first cladding layer 12. Therefore, a current flows in the upper surface of each stripe region with the width, and the active layer 1 corresponding to each current width
Laser oscillation is performed independently in the region 3. That is, a laser resonator that can be independently driven is formed for each stripe region.

[0006]

One of the problems in driving a multi-beam semiconductor is thermal crosstalk. This is because, for example, in a multi-beam semiconductor laser having two laser resonators as shown in FIG. 6, when driving one laser resonator to emit a beam, driving the other laser resonator In addition, heat generated by energization is conducted to one of the laser resonators to lower the beam output level.

[0007] In the case of the conventional multi-beam semiconductor laser, since the driving current is large and the thermal resistance is relatively large, heat conduction easily occurs between the laser resonators. For this reason, the output level of the beam emitted from each laser resonator fluctuates greatly, leading to a reduction in operation reliability. To avoid the effects of this thermal crosstalk,
It is necessary to take measures such as increasing the interval between the laser resonators and disposing a member for preventing heat conduction between the laser resonators, and there is a limit in reducing the manufacturing cost.

The present invention has been made under such a background, and an object of the present invention is to provide a semiconductor laser having a structure capable of effectively preventing thermal crosstalk.

[0009]

According to the present invention, there is provided a semiconductor laser having a conventional structure, wherein the current blocking layer is formed by a conventional Ga laser.
Instead of As mixed crystal, AlG with higher thermal resistance
It is characterized by being formed of a semiconductor mixed crystal composed of either aInP or AlInP.

[0010]

A dielectric crystal such as Si ₃ N ₄ or SiO ₂ or a mixed crystal of AlInP and AlGaInP is made of GaAs.
Higher thermal resistance than mixed crystals. Therefore, when these materials are used for the current blocking layer, the heat generated in the laser resonator due to energization is less likely to be conducted to the adjacent laser resonator via the current blocking layer. As a result, in the laser, heat transmitted to the adjacent resonator via the current blocking layer side of the active layer is suppressed, so that the total amount of heat conducted to the adjacent resonator is reduced. Therefore, by adopting the crystal structure of the present invention, the thermal conductivity between laser resonators becomes smaller than before, and the influence of thermal crosstalk is reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the present invention, since the composition of the layer crystal of the conventional multi-beam semiconductor laser is changed, the names and reference numerals of the respective layers will be described as they are.

A multi-beam semiconductor laser according to one embodiment of the present invention has a structure in which the current blocking layer 16 is formed of either AlGaInP or AlInP in the conventional layer structure shown in FIG. An example in which the current block layer 16 is formed of a Si ₃ N ₄ dielectric will be described.

One means for suppressing the thermal crosstalk of the multi-beam semiconductor laser is to improve the heat radiation from the laser chip and reduce the temperature rise due to heat generation. According to this idea, the use of a Si ₃ N ₄ dielectric having a higher thermal resistance than the conventional GaAs mixed crystal seems to be disadvantageous. However, due to our considerations,
Considering the path of heat conduction, it has been found that the fact that the thermal resistance of the current blocking layer is large works rather advantageously. That is,
As shown in FIG. 1, the heat generated in the active layer when the laser resonator is driven is suppressed in the semiconductor laser from conduction through the current blocking layer side of the active layer by the current blocking layer made of a dielectric material having a large thermal resistance. Is done. Therefore, the amount of heat conducted to the adjacent resonator is smaller than in the related art, and the thermal crosstalk is accordingly reduced.

In the above description, the current blocking layer 16 is made of Si ₃
This is the case where it is formed of an N ₄ dielectric material.
The same effect can be obtained when formed of a dielectric such as iO ₂ or polyimide.

FIG. 2 is a sectional view of a layer structure of a laser epi to be a starting material of the multi-beam semiconductor laser of this embodiment. Referring to FIG. 2, a first buffer layer 11 having a thickness of 0.23 [μm] and a thickness of 1.1
[Μm] first cladding layer 12, strained quantum well layer 13a
The active layer portion 13 composed of １３13 g, the second cladding layer 14 having a thickness of 1.1 [μm], and the second buffer layer 15 having a thickness of 0.14 [μm] are respectively OMVPE (Organometallic v).
It is formed in this order by a well-known crystal growth means such as an apor phase epitaxy method.

The semiconductor substrate 10 and the layers 11 to 15
Of these, the semiconductor substrate 10 has an electron concentration of 2 × 10 ¹⁸ [cm
^-3 ] Si-doped GaAs mixed crystal, first buffer layer 1
Reference numeral 1 denotes a Si-doped GaAs mixed crystal having an electron concentration of 1.5 × 10 ¹⁸ [cm ⁻³ ], and the first cladding layer 12 has an electron concentration of 2
× 10 ¹⁷ [cm ⁻³ ] Se-doped (Al _0.7 G
a _0.3 ) In _0.5 P mixed crystal, and the active layer 13 is made of undoped (Al _0.4 ) having a thickness of 0.08 [μm].
Ga _0.6 ) _0.5 In _0.5 P layers, 13 c and 13 e undoped (Al _0.4 Ga _0.6 ) having a thickness of 0.008 [μm]
_0.5 In _0.5 P layer, 13b, 13d, 13f has a thickness of 0.
The first clad layer 14 has a Ga _0.43 In _0.57 P layer of 01 μm and a Zn-doped (Al _0.7 Ga _0.3 ) In _0.5 P mixed crystal having a hole concentration of 4 × 10 ¹⁷ cm ⁻³ . The buffer layer 15 is made of a Zn-doped Ga _0.5 In _0.5 P mixed crystal having a hole concentration of 1 × 10 ¹⁸ [cm ⁻³ ].

FIGS. 3 to 5 are views showing the steps of manufacturing a multi-beam (double-beam) semiconductor laser according to this embodiment. Less than,
Each step will be described with reference to these figures.

First, using the laser epi as a starting material (see FIG. 3A), a resist film 20 is formed on the upper surface of the second buffer layer 15 and then patterned with a resist 21 (FIG. 3B). reference). Then, the resist film 20 other than the portion covered with the resist 21 is etched, and thereafter, the resist 21 is removed (see (c)). This was mixed with a 50 ° C. mixed acid (sulfuric acid: hydrogen peroxide solution: water = 3: 1:
Etching is performed for 6 minutes in 1) to leave about 0.2 [μm] of the second cladding layer 14 (see (d)). This allows
Two stripe regions are formed.

Next, the Si ₃ N ₄ dielectric film is formed to a thickness of 0.3 [μm].
m] After the growth, the remaining resist film 20 is etched. As a result, the current block layers 16a to 16c are formed (see FIG. 4A). Then, the current blocking layer 1
A resist film 22 is formed on the surface of each of the stripe regions 6a to 16c and each stripe region, and a resist 23 is placed on the center of the resist film 22 (see FIG. 1B). Then, the resist film 22 other than the portion where the resist 23 is placed is etched (see (c)), and Zn-doped GaAs (hole concentration 4 × 10 ¹⁷ [c
m ⁻³ ]) is grown by 1 μm. As a result, the contact layers 18a and 18b are formed (see (d)).

The central portion of the resist film 22 is removed, and a new insulating film 24 is formed on the entire surface of the contact layers 18a and 18b. A resist 25 is patterned at the center (see FIG. 5A). Then, the contact layers 18a, 18b
The insulating film 24 on the upper surface is etched (see (b)), and a p-electrode member 26 is deposited on the entire surface (see (c)). The resist 25 is removed, and at the same time, the p-electrode member 26 on the upper surface is removed.
Also remove. As a result, p electrodes 19a and 19b are formed. Further, the substrate 10 is etched from the back, and 70 [μ]
m]. After that, the n common electrode 1 is
9c is vapor-deposited and alloyed at 400 ° C./1 minute in a nitrogen atmosphere (see (d)).

Next, an embodiment of the present invention will be described.
The configuration of this semiconductor laser is almost the same as the above-described example, and only the composition of the current blocking layer is different. That is, in this embodiment, the current blocks 16a to 16c of FIG.
It was formed of a mixed crystal of nP or AlGaInP. As described above, by changing the material of the current blocking layer and passing through the steps of FIGS. 3 to 5 as in the above-described embodiment, a multi-beam semiconductor laser with small thermal crosstalk can be obtained.

[0022]

As described above in detail, according to the present invention, in a semiconductor laser using a GaAs substrate, the current blocking layer is made of AlInP or AlGa having high thermal resistance.
Since the semiconductor laser is formed of a semiconductor mixed crystal of InP, the thermal conductivity between the laser resonators is smaller than that of a semiconductor laser having a conventional structure, and there is an effect that thermal crosstalk is reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a heat transfer path of a multi-beam semiconductor laser.

FIG. 2 is a sectional view of a layer structure of a laser epi according to an embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of the multi-beam semiconductor laser of the present embodiment.

FIG. 4 is a manufacturing process diagram of the multi-beam semiconductor laser of the present embodiment (continuation of FIG. 3).

FIG. 5 is a manufacturing process diagram of the multi-beam semiconductor laser of the present embodiment (continuation of FIG. 4).

FIG. 6 is a sectional view of a layer structure of a general multi-beam semiconductor laser to which the present invention is applied.

[Explanation of symbols]

Reference Signs List 10: semiconductor substrate, 12: first cladding layer, 13: active layer, 14: second cladding layer, 16a to 16c: current blocking layer, 19a to 19c: electrode.

Continuation of the front page (56) References JP-A-1-281786 (JP, A) JP-A-2-257691 (JP, A) JP-A-3-203283 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) H01S 3/18 H01S 3/25

Claims (1)

(57) [Claims] At least a first cladding layer of a first conductivity type semiconductor mixed crystal, a semiconductor mixed crystal active layer, and a second cladding of a second conductivity type semiconductor mixed crystal are formed on a first conductivity type GaAs substrate. Layers are formed at least in this order, and the surface of the second clad layer is formed as a plurality of stripe regions separated at predetermined intervals by a current block layer, and a plurality of laser resonators having an independent drive structure are formed. In the semiconductor laser, the current blocking layer is formed of a semiconductor mixed crystal of AlGaInP or AlInP.