JPH02181488A - Heat sink for semiconductor laser element use - Google Patents

Abstract

PURPOSE:To lower a heat resistance and to secure the long lifetime or the title heat sink due to a heat dissipation effect by a method wherein the heat sink, which is soldered to a buried semiconductor laser element having a square recessed part in its base, is provided with a protruding part to fit into the recessed part. CONSTITUTION:A heat sink 10a, which is soldered to a buried semiconductor laser element provided with a recessed part having a base of a width of (a1) and height of (b3), is provided with a protruding part. When the relation between the width (a) and the height (b) of this protruding part is assumed to be a<a1 and b>b1, the conditions of b<b2 and b<b3 are satisfied. As the sink 10a is soldered to the element in such a way that the protruding part of the sink 10a comes into contact to the recessed part of the laser element, an active layer 3 of the element keeps a distance or 5 to 6mum from solder layers 11 and 11a to the creeping of a solder to the side surfaces of the element and moreover, as the distance between the sink and the luminous region of the element active layer can be also kept in 2mum or thereabouts, the heat dissipation effect of the sink is good and the long lifetime of the sink can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat sink connected to a semiconductor laser element.

[Conventional technology]

The GaAa-Aj GaAs-based buried semiconductor laser device has the structure shown in FIG. 3, and has excellent characteristics that cannot be obtained with conventional double heterojunction semiconductor laser devices. FIG. 3 is a schematic cross-sectional view seen from the front of the device, in which a first cladding layer 2° active layer 3. Second cladding layer4. The contact layer 5 is formed in this order, and both side surfaces of the striped mesa portion formed in the second cladding layer 4 parallel to the laser beam traveling direction are filled with a current pinching layer 6. That is, the active layer 3 has two cladding layers 2
．． The active layer 3 is further sandwiched between the active layer 3 and the current pinching layer 6
It has a structure in which current flows only in a part of the semiconductor laser element, and by selecting the material for the current-spanning layer 6, the current-spanning layer 6 becomes a light absorption layer, so this semiconductor laser device can obtain high output. . In this way, embedded semiconductor laser devices provide high-output, stable light sources, and are therefore considered promising for use as light sources for optical information transmission and optical information processing. Note that 7.8 represents the upper and lower electrodes, respectively.

This semiconductor laser device is manufactured as follows. Figure 4 (al~+d+ shows the order of the main steps, and the same parts as in Figure 3 are denoted by the same reference numerals. First, the n-G with a thickness of 100 μm and a carrier concentration of 3 XIQ"/aJ)
A thickness of 1.5 mm was formed on an aAs substrate 1 using the MOCVD method. H
, n-MIlGat- with a carrier concentration of 5×10”/cd
x^3 1st clad rfi2, thickness 0.1-, carrier concentration 3X10I? /- p -Aj, Ga, -2As
Active layer 3° thickness 1.5-+ carrier concentration 5 x 10
I? / cd p-kl, Ga, -, As second cladding layer 4. Thickness 0.5 Irm, carrier concentration lXl0”/
- p-Ga^3 contact layer 5a is sequentially grown [
FIG. 4 (5)] Next, a SiJ film is deposited on the entire upper surface of this laminate, a photoresist is applied and patterned,
After forming the stow film 9 in a stripe shape and removing the resist, a contact layer 5a is formed using the 5 lot film 9 as a mask.
Then, the second cladding layer 4 is etched to remove part of the second cladding layer 4 to form a striped mesa portion, and then the MOCVD method is used again to form a mesa portion with a thickness of 1.7n+.
An n-GaAs current-spanning layer 6 with a carrier concentration of 3XIQ''/aJ is selectively grown on both sides of the mesa portion, but at this time, the upper surface of the current-spanning layer 6 is not aligned with the surface of the contact layer 5a. 5a (FIG. 4, 1et). Subsequently, a contact layer 5b with a thickness of 3 pm is grown on the current blocking layer 6 while leaving the 5 lot film 9. This contact layer 5b is connected to the previously formed contact layer 5a at the side surface of the mesa portion and becomes the contact layer 5 as one unit (FIG. 4 1et)
, After the completion of crystal growth, the device was taken out from the reaction tank and 5L
(By removing the h film 9, a buried semiconductor laser device having the structure shown in FIG.
-Ge alloy electrode 8/ Both are constructed as shown in FIG. 3 by sputtering.

However, when operating a high-power semiconductor laser device,
Since the element generates heat as a result of laser oscillation, the optical output characteristics of the element deteriorate and its lifespan is shortened. Therefore, in order to enhance the heat dissipation effect of the device, the electrode near the active layer of the device, that is, the contact layer side, is usually bonded to a heat sink (heat sink) using In solder or the like. FIG. 5 is a schematic cross-sectional view showing the semiconductor laser element shown in FIG. 3 bonded to a heat sink. Heat sink 10 such as Cu in Fig. 5
Soldering is performed by placing the electrode 7 of the element on the In solder layer 11 formed on the substrate, heating it to a predetermined temperature, and cooling it. As can be seen from FIG. 3 showing the structure of this semiconductor laser device and FIG. 4 showing the manufacturing process thereof, both sides of the p-GaAs contact layer 5 of the device protrude slightly when viewed from the front. I
The reason why the indium solder 11 grows so as to form a recess in W5 is that when the element and heat sink are bonded, the In solder 11 wraps around the sides of the element and reaches the active layer 3, making both sides thick so that it does not interfere with light emission. It makes it grow.

[Problem to be solved by the invention]

However, when connecting the semiconductor laser element to the heat sink IO as described above, the following problem occurs. This is because the distance between the active FI 3, which is the light emitting region of the device, and the heat sink IO is 5 to 6 nm apart, and there is a space formed by the recess formed in the contact layer 5, so that the heat dissipation effect is not sufficient. In order to increase the heat dissipation effect, the thickness of the contact layer 5 can be made thinner, but as mentioned earlier, since the solder wraps around, it cannot be made thinner than 3-, which reduces the heat dissipation effect and the solder wrap. This is contradictory to preventing crowding.

The present invention has been made in view of the above-mentioned points, and its purpose is to improve the heat dissipation effect of a semiconductor laser element having a recessed portion in a contact layer, and to provide a heat sink that does not cause solder to run around.

[Means to solve the problem]

In order to achieve the above object, a convex part is provided on the heat sink to be soldered to the embedded semiconductor laser element, which has a concave part with a convexity a on the bottom surface and a height b1.
The height (bt) is the sum of a < a,, b > bt plus the thickness of the electrode, and b < b, plus the thickness of the solder. Since soldering is carried out with the tip of the convex part in contact with the concave part of the semiconductor laser element, in order to prevent the solder from going around the sides of the element, the active layer of the element is separated from the solder layer by 5-6-
Moreover, since the distance between the heat sink and the light emitting region of the element active layer can be set to about 2 -, the heat dissipation effect is good.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a schematic perspective view showing the shape of the heat sink of the present invention. This heat sink 10a has a convex part as shown in Fig. 1, and its radius a is 5-9, and the height b is 4.5 n. Although the In solder layers 11.11a provided on both sides are also shown, the solder layer 11a at the tip of the convex portion is not provided over the entire length in the longitudinal direction, but is masked on a portion near the end faces of the front and rear surfaces. 1
The film is deposited over the entire width a of the tip of the convex portion to a length of 50 nm. This is because if the solder layer is present near the end face of the convex portion, there is a risk that the solder will penetrate into the active layer 3 during bonding with the semiconductor laser element.

FIG. 2 is a schematic cross-sectional view showing a state in which a semiconductor laser S element is bonded to this heat sink, and parts common to the figures described above are indicated by the same reference numerals. Here, in order to make it as shown in FIG. 2, the width a and height b of the convex portion of the heat sink 10a in FIG. It is necessary to determine the

The width a of the convex portion of the heat sink 10a is narrower than the convergence of the bottom of the element recess, and the height b of the convex portion is the sum of the height of the element recess and the thickness of the contact layer side electrode 7 (b). high (and this plus the thickness of the solder layer 11 (b,
) thinner (to do, i.e. a〈al+ b > b
g, b < bs.

Therefore, for example, if the width a of the convex part of the heat sink 10a is 5μ,
The height is 4.5 μ, the thickness of the solder Jt2111 is 3 μ, and the solder Jill is deposited on the convex portion of the heat sink 10a.
The thickness a can absorb dimensional errors due to processing accuracy of the convex portion of the heat sink 10a.

When machining the convex portion of the heat sink 10a, if the height b is larger than the set value, the contact layer side electrode 7 and the heat sink 10a may not be sufficiently bonded when bonding to the semiconductor laser element, and the height b may be larger than the set value. If the thickness is lower than the set value, the thickness of the solder layer 11a compensates for problems such as poor contact between the tips of the convex portions of the heat sink 10a and the concave portions of the element. The solder layer 11a at the tip of the convex portion of the heat sink 10a fills the gap with the concave portion of the semiconductor laser element to make close contact between the two, thereby helping to dissipate heat from the element toward the heat sink 10a. The difference between FIG. 2 and FIG. 5 is that when soldering a semiconductor laser element, the concave part of the element does not simply remain as a space, and the heat sink 1 is placed there.
The convex portion formed at 0M enters and comes into close contact with the element recess through the In solder, thereby increasing the heat dissipation effect from the element active layer 3.

The method of mounting the semiconductor laser element on the heat sink 10a is basically the same as the conventional method, and when using the heat sink 10a of the present invention, the recessed part of the element is placed on the In solder layer 11a deposited on the tip of the convex part. All you have to do is match them.

Next, the thermal resistance of 100 semiconductor laser devices mounted on the heat sink 10a of the present invention in the same manufacturing loft as described above was measured.
A comparison was made with 100 samples using 0. As a result, the average value of thermal resistance was 58℃/W with the conventional one, and the variance was 2.
In contrast, in the case of the present invention, the average value of the thermal resistance was 34° C./W and the variance was 16° C./W, which is a decrease of about 40%.

This may be due to the fact that the distance between the light emitting region and the heat sink is shorter in the present invention because the heat sink convex portion is positioned to replace the space between the light emitting region of the device and the heat sink, as described above.
This is because the heat dissipation effect by the heat sink convex portion has been improved.

In addition, one semiconductor laser device assembled using the heat sink of the present invention and one assembled using a conventional heat sink were each used.
An aging test was conducted on 00 pieces at an output of 30+iW for 1000 hours. As a result, in the case of the heat sink of the present invention, there were 6 elements whose characteristics deteriorated after 1000 hours of aging, whereas in the conventional case, 21 elements deteriorated. This shows that the improved heat dissipation effect by the heat sink of the present invention has a significant effect on the life of the element, and its effectiveness was confirmed. In addition, no solder penetration into the active layer of the device is observed.

〔Effect of the invention〕

To dissipate the heat generated from a semiconductor laser device, when soldering the device to a heat sink, thicken the contact layer on both sides of the device so that the solder does not reach the active region of the device and prevent light emission. Providing a recess is effective in that it increases the distance between the active region and the solder layer on the heat sink, but on the other hand, it creates a gap between the element and the heat sink, which is still not sufficient for heat dissipation. In contrast, in the present invention, as described in the embodiment, a heat sink is provided with a convex portion, and a part of the solder layer formed at the tip of the convex portion is aligned with the element concave portion, so that the heat sink convex portion and the element concave portion are in close contact with each other, and Since the width and height of the heat sink protrusion are appropriately determined so that the heat sink and the entire surface of the element contact layer side electrode are soldered together, the distance between the element active region and the heat sink is sufficiently set.
In addition to the fact that the solder does not run around, the heat generated especially from the active region of the device can be dissipated from the heat sink convex portion, and as a result, the semiconductor laser device soldered using the heat sink of the present invention has a higher performance than the conventional one. Thermal resistance is significantly reduced, and its heat dissipation effect makes it possible to ensure a long life.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing the shape of the heat sink of the present invention, FIG. 2 is a schematic cross-sectional view showing a state in which a semiconductor laser element is soldered to the heat sink of the present invention, and FIG. 3 is a semiconductor device having a recessed portion in the contact layer. A schematic cross-sectional view of a laser element,
FIG. 4 (al to [dl are main manufacturing process diagrams of the semiconductor laser device shown in FIG. 3, and FIG. 5 is a schematic cross-sectional view showing a state in which the semiconductor laser device is soldered to a conventional heat sink. 1: Substrate , 2: first cladding layer, 3: active layer, 4: second
Cladding layer, 5.5a, 5b: Contact layer, 6:
Current pinching layer, 7, 8: electrode, 9: sto*lIl,
10.10a: Heat sink, 11. Ila: Solder layer. 11a I'! 1 Figure 1 Figure 2'$3 Figure 5'$4! ! 1

Claims (1)

[Claims] 1) A first cladding layer, an active layer, and a second cladding layer having a striped mesa portion, which are laminated on a semiconductor substrate.
A heat sink for a semiconductor laser element that is soldered to the contact layer side of an embedded semiconductor laser element, which has a contact layer having a concave portion on the upper surface, a current pinching layer embedded in both sides of a mesa part, and both upper and lower electrodes, Width (a) and height (b) of the convex portion formed on the bonding surface with the element
are the width (a_1) and height (b_1) of the bottom surface of the contact layer recess.
1), height of b_1 plus electrode thickness (b_2), b
A heat sink for a semiconductor laser element, characterized in that a height (b_3) obtained by adding the thickness of a solder layer to_2 has the following relationships: a<a_1, b>b_2, and b<b_3.