JPH0362987A - Semiconductor laser and its manufacturing method - Google Patents

Abstract

PURPOSE:To reduce thermal resistance and improve cooling by forming an electrode for ohmic contact in the state where a cap layer is made thinner and projecting and recessed parts are left on the surface of a semiconductor layer and then forming a bump layer for bonding. CONSTITUTION:Even if a cap layer 9 which is laminated on a ridge strip 8 and a current narrow layer 7 with recessed and projecting parts on the surface is thin and recessed and projecting parts remain on the surface of the cap layer 9, an electrode 11 for ohmic contact to be formed on it by the vacuum deposition and electrolytic plating and a bump layer 12 for bonding absorb the recessed and projecting part, thus enabling the surface of the bump layer 12 to be flat. In this case, the electrode 11 for ohmic contact and the bump layer 12 for bonding are equivalent to a heat sink, thus preventing thermal resistance at this part from being increased and enabling thermal resistance to be decreased due to thinning of the gap layer 9.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, Aj!
The present invention relates to a compound semiconductor semiconductor laser such as a Ga1nP visible light semiconductor laser and a method for manufacturing the same.

[Conventional technology]

A7! As a semiconductor laser that emits Galnp visible light, there is a conventional semiconductor laser as shown in FIG.

(Autumn 1963 Applied Physics Society Proceedings 4I”ZC-11).

In Figure 3, l is n GaAs1 plate, 2 is n71
, ffQalnP lower cladding layer, 3 is Ga1nP active layer, 4 is p-Aj! Ga1nP upper craft layer, 5 is p
7 is an n-GaAs current confinement layer, 8 is a rift stripe, 9 is a p-GaAs camp layer, 10 is a cathode electrode, and 1 is an anode electrode.

In this semiconductor laser, the current path is restricted by the n-GaAs current confinement layer 7. Further, in order to absorb the emitted light, there is an equivalent refractive index difference in the lateral direction, and a refractive index waveguide mechanism is provided.

A method of manufacturing the semiconductor laser shown in FIG. 3 will be described with reference to FIG. 4.

In this semiconductor laser, first, as shown in FIG. 4 (al), an n-GaAs substrate 1, which is a compound semiconductor substrate,
AlGa InP lower cladding layer 2°Ga InP active layer 3. p-AAGalnP upper craft layer 4 p-
Ga1nP anti-oxidation N5 is sequentially grown by MOVPE method.

Next, as shown in FIG.
a Ridge stripes 8 are formed on the InP upper cladding layer 4.

Furthermore, as shown in FIG. 4 fcl, the MOVP
Using the E method, an n-GaAs current confinement layer 7 is selectively grown with the 5i02 stripe mask 6 left in place, so as to extend one inch into both sides of the ridge stripe 8.

Finally, as shown in FIG. 4+dl, the SiO2 stripe mask 6 is removed, and then a p-GaAs cap W19 is grown to form the cathode electrode 10 and the anode electrode 11, respectively.

[Problem to be solved by the invention]

This semiconductor laser manufactured as described above is an n-G
A raised portion 70 is formed near the side surface of the rift stripe 8 of the aAs current confinement layer 7 . As a result, in order to flatten the crystal surface, the pGaAsGaAs cap layer 9 thereon needs to have a thickness of about 3 μm. Flattening of the crystal surface is necessary because a semiconductor laser chip is normally mounted upside down on a heat sink 15 with solder 14, as shown in FIG.

However, Aj! The Ga1nP crystal has a fairly large thermal resistivity of about 14°C IJ/W, and the distance between the heat generating part 13 and the heat sink 15 greatly affects the thermal resistance of the entire device, and the thickness of the p-GaAs cap layer 9 If the thickness is as much as 3 μm, the thermal resistance will increase.

Note that the Au-based anode electrode 11 used for -a is
Since the thermal resistance can be ignored, it can be considered equivalent to a heat sink.

As described above, in the semiconductor laser shown in FIG.
It is desirable that the GaAs cap layer 9 be as thin as possible.

However, on the other hand, if the p-QaAs camp layer 9 is too thin, the current path will be too narrow and the device resistance will increase.

An object of the present invention is to provide a semiconductor laser that can shorten the distance from the heat generating part to the heat sink to reduce thermal resistance, improve maturation, and achieve high output and high reliability.

(Means for Solving the Problem) The semiconductor laser according to claim (1) is provided by forming electrodes for ohmic contact with the camp layer thinned and unevenness left on the surface of the semiconductor layer, and then forming an electrode for ohmic contact. In the method for manufacturing a semiconductor laser according to claim (2), the method includes a bump layer for bonding.
In producing the semiconductor laser described in ff requirement (1), electrodes for over-the-counter contact are formed by vacuum evaporation, and bump layers for bonding are formed by electrolytic plating.

In the semiconductor laser according to claim (3), the side surfaces of the ridge stripe are shaped perpendicularly to the substrate surface, and current confinement layers are formed on the upper cladding layer on both sides thereof. The thickness of the current confinement layer at this time is made the same as the height of the ridge stripe.

Then, a camp layer with a small thickness is laminated on the top surface of the flattened Fuji stripe and current confinement layer.

In the method for manufacturing a semiconductor laser according to claim (4), claim +
In producing the semiconductor laser described in 1+, a ridge stripe is formed by reactive ion etching.

[Effect]

According to the semiconductor laser according to claim (1) and the method for manufacturing a semiconductor laser according to claim (2), the cap layer having an uneven surface and laminated on the di-stripes and the current confinement layer is thin and the cap layer is thin. Even if unevenness remains on the surface of the layer, the electrode for ohmic contact and the bump layer for bonding, which are formed on top of it by vacuum evaporation and electrolytic plating, respectively, will absorb the unevenness, and the surface of the bump layer will be smooth. becomes flat. At this time, the electrode for ohmic contact and the bump layer for bonding are equivalent to a heat sink, so even if their film thickness increases, the thermal resistance of these parts will not increase, and the cap layer will be thinner. This reduces thermal resistance.

Therefore, the distance between the heat generating part and the heat sink can be reduced to less than half that of conventional elements, so thermal resistance can be reduced and the heat generated by the semiconductor laser can be effectively dissipated. Therefore, it is possible to increase the output power and reliability of the semiconductor laser.

According to the semiconductor laser according to claim (3) and the method for manufacturing a semiconductor laser according to claim (4), the ridge stripe is formed by reactive ion etching using chlorine gas, so that the side surface is not attached to the substrate surface. A ridge stripe is formed vertically. Thereafter, when the current confinement layer is selectively grown on the upper cladding layer on both sides of the ridge stripe, the current confinement layer is selectively grown and hardly grows on the sides of the Fuji stripe. For this reason,
The occurrence of swelling near the side surfaces of the ridge stripe is suppressed, and the surface is flattened at this point. Therefore, it is not necessary for the gap layer to absorb the swelling near the side surfaces of the ridge stripe, and it is possible to make the gap layer thinner.

Therefore, the distance between the heat generating part and the heat sink can be reduced to less than half that of conventional elements, so thermal resistance can be reduced and the heat generated by the semiconductor laser can be effectively dissipated. Therefore, it becomes possible to increase the output power and reliability of the semiconductor laser.

[Example] Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows a semiconductor laser corresponding to claim (1),
This semiconductor laser uses an n-Ga compound semiconductor substrate.
An As substrate 1 and an n-AjlGa [nP lower cladding layer 2. Ga1
nP active layer 3. p-AIGarnP upper ground layer 4, p-ca+nr'M prevention layer 5, and this p-A6G
P-AlGa1nP is formed on the alnP upper cladding layer 4 and the p-Ga1nP oxidation prevention layer 5, and fills the Fuji stripe 8 and both sides of this ridge stripe 8.
The n-GaAs current confinement layer 7 formed on the upper cladding layer 4 and the p-Ga layer 8 with a thickness of 0.5 to 1 pm laminated on the upper surfaces of the ridge stripe 8 and the n-GaAs current confinement layer 7 are capped. layer 9, an anode electrode 11 for ohmic contact and a bump layer 12 for bonding, which are laminated in order on the p-GaAs cap layer 9, and a cathode electrode 10 made of an n-GaAs substrate. In this case, the total thickness of the anode electrode 11 and the bump layer 12 is preferably about 3 μm or more in order to flatten the unevenness on the surface of the semiconductor layer.

Next, a method for manufacturing this semiconductor laser will be explained.

This semiconductor laser was fabricated on an n-GaAs substrate l by a process similar to that described for FIGS.
AllGa I nP lower cladding layer 2. QaInP
Active layer 3. p-A7! A Ga1nP upper cladding layer 4 and a p-Ga1nP oxidation prevention layer 5 are sequentially laminated, and 5i02
A ridge stripe 8 is created using a stripe mask 6, and then n-GaA is applied on both sides of the ridge stripe 8.
The s-current confinement layer 7 is formed by selective growth technique of MOVPE method. As a result, a raised portion 70 is formed near the side surface of the ridge, similar to the conventional example. After removing the S i O 2 stripe mask 6, a p-GaAs cap layer 9 is grown thereon, the film JI being much thinner than the conventional example and having a thickness of, for example, 0.5 μm. At this point, the surface of the semiconductor layer has
Unevenness reflecting the raised portion 70 of the n-GaAs current confinement layer 7 remains.

Next, as the cathode electrode 10, AuGe/Ni/A
u. As the anode electrode 11, Cr/Au is formed to a thickness of, for example, about 1 μm by vacuum evaporation, and then Au plating is performed in an acidic plating bath at a temperature of 50° C. and an electrolytic current of 10 mA for 10 minutes. . The thus formed bump layer 12 has a thickness of about 2 μm and has a substantially flat surface regardless of the unevenness remaining on the p-GaAs cap layer 9.

Chief of Tsimpei group FIG. 2 shows a semiconductor laser corresponding to claim (3).

This semiconductor laser uses an n-Ga compound semiconductor substrate.
As vE plate 1 and n-A1, which is formed by sequentially laminating this n-Ga 8 to 1 layer! Ga1nP lower cladding layer 2. G
aInP active layer 3. p-AIGaInP upper ground layer 4, p-Ga1nP oxidation prevention layer 5, and this p-A7
! Ga InP upper cladding layer 4 and p-Ga1nP
A ridge stripe 8 formed on the anti-oxidation layer 5 and having side surfaces perpendicular to the substrate surface, and an n-GaAs current confinement layer formed on both sides of the ridge stripe 8 with the same thickness as the height of the ridge stripe 8. 7, a p-GaAs cap layer 9 with a film thickness of 0.5 to 1 μm formed on the ridge stripe 8 and the n-GaAs current confinement layer 7, and a p-GaAs cap layer 9 formed on the ridge stripe 8 and the n-GaAs current confinement layer 7;
an anode electrode 11 formed on the aAs cap layer 9;
It includes a cathode electrode lO formed on an n-GaAs substrate l.

Next, a method for manufacturing this semiconductor laser will be explained.

This semiconductor laser was fabricated on an n-GaAs substrate l using a process similar to that described in FIG. 3fa). Ga
1nP lower cladding layer2. Ga1nP active layer 3. p-A
An fGalnP upper cladding N4 and a p-Ga1nP oxidation prevention layer 5 are sequentially laminated, and then a ridge stripe 8 is formed using an St○2 stripe mask 6. In this case, the side surfaces of the ridge stripes 8 are formed perpendicular to the substrate surface. This is a gas pressure of 5 x 10-
'Torr.

It is obtained by performing reactive ion etching using chlorine gas at an extraction voltage of 1.5 KV.

Next, add MOVPE on both sides of this ridge stripe 8.
The n-GaAs current confinement layer 7 is selectively grown by the method. As a result, since the ridge stripe side surface 80 hardly ever gets bent, it is possible to suppress the occurrence of a raised portion near the side surface of the ridge stripe 8 as in the conventional example. Therefore, when the film is grown to the same thickness as the height of the ridge stripe 8, the surface is almost completely flattened.

On top of this, a p-GaAs cap layer 9 with a film thickness of 0.5 μm is formed, and finally a cathode? it pole 10. The anode electrode 11 is formed to complete the semiconductor laser.

In this case, there is no need to absorb the raised portion with the p-○aAs cap N9, so it is possible to save the material as described above.

In the configurations of Example 1 and Example 2, the anode ″:rL
Since the thermal resistance of the pole 11 or the bump layer 12 can be ignored, if we consider that they are equivalent to a heat sink, the distance between the heat generating part and the heat sink after mounting in the upside town will be the same as that of the p-AfGa InP upper cladding layer 4 and the heat sink. p-
The film thickness of the Ga1nP oxidation prevention layer 5 was set to 0.8 μm and 0.8 μm, respectively.
．． If it is 1 μm, it can be made close to 1.4 μm. Therefore, heat dissipation is better (1.1 to 1.5 times)
, low thermal resistance can be achieved. For example, it was possible to reduce the temperature from around 40°C/W to 30°C/W. Therefore, the semiconductor laser can be effectively cooled, making it possible to increase the output and reliability of the semiconductor laser.

In addition, in the example, the anode electrode 1 for ohmic contact
In 1, since a non-alloy type Cr/Au system was used, the thickness of the p-GaAs cap layer 9 was set to 0.5 μm. However, when using an alloy type Au/Zn system etc., the alloy layer is formed, so a pGaAsGaAs cap layer of about 91 μm is required. In this case, the distance between the heat generating part and the heat sink after mounting is
If the film thicknesses of the TnP upper cladding layer 4 and the p-Ca1nP oxidation prevention layer 5 are the same as above, they are 1.9 μm.

In addition, although Ga1nP was used for the active layer, AlGa1nP
Materials of any composition may be used.

Furthermore, the same effect can be obtained even in the case of a configuration in which p and n are reversed.

〔Effect of the invention〕

According to the semiconductor laser according to claim fi+ and the method for manufacturing a semiconductor laser according to claim (2), since the electrode for ohmink contact and the bump layer for bonding are formed on the cap layer, the thermal resistance is low. Even if the large cap layer is thin, the thermal resistance is small and it is considered equivalent to a heat sink for Ohmink contact? By making the bump layer for bonding with the P pole 11, the flatness of the element surface can be obtained. Therefore, the thermal resistance can be reduced without compromising the flatness of the element surface for mounting, and the semiconductor laser can be effectively cooled, making it possible to increase the output power and reliability of the semiconductor laser. It becomes possible.

The semiconductor laser according to claim (3) and claim (
4) According to the method for manufacturing a semiconductor laser described above, since the upper cladding layer has side surfaces perpendicular to the substrate surface or the sistripes are formed, current confinement layers are formed on both sides of the ridge stripes on the upper cladding layer. When forming the
It is possible to suppress the generation of raised parts due to the current confinement layer on the sides of the ridge stripe, and by forming the current confinement layer on both sides of the ridge stripe with the same thickness as the height of the ridge stripe, the ridge stripe and current confinement layer can be suppressed. The top surface can be made flat. Therefore, the cap layer can be thin, and the thermal resistance can be reduced without impairing the flatness of the element surface for mounting, and the semiconductor laser can be effectively cooled, which can increase the output power of the semiconductor laser. , high reliability is possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the semiconductor laser of Example 1, FIG. 2 is a cross-sectional view of the semiconductor laser of Example 2, FIG. 3 is a cross-sectional view of a conventional semiconductor laser, and FIG. 4 is a conventional manufacturing method of the semiconductor laser. The process diagram and FIG. 5 are cross-sectional views showing the mounted state of the semiconductor laser. ] ---n-LG a As substrate, 2-n-Al
GalnP lower cladding layer, 3...Ga1nP active layer, 4...p-AAGalnP upper cladding layer, P-GalnP oxidation prevention layer, 6...SiO2
Strive mask, 7... n-GaAs current confinement layer,
8... Ridge stripe, 9... p-Qafi, s
Cap layer, 10... Cathode electrode, 11... Anode electrode, 12... Bump layer, 13... Heat generating part, 1
4...Solder, 15...Heat sink, 70...
Swelling part of electric comb constriction layer, 80... Ridge stripe side view Figure 8...'J 7 Distripe 70... Swelling part 8... Ridge stripe O... Ridge stripe side view

Claims (4)

[Claims] (1) A compound semiconductor substrate, a lower cladding layer, an active layer, and an upper cladding layer laminated in this order on this compound semiconductor substrate, a ridge stripe formed on this upper cladding layer, and a layer that embeds both sides of this ridge stripe. a current confinement layer formed on the upper cladding layer, a cap layer laminated on the upper surface of the ridge stripe and the current confinement layer, and an electrode for ohmic contact and a bonding layer laminated on the cap layer in this order. A semiconductor laser having a bump layer. (2) A method of manufacturing a semiconductor laser according to claim (1), characterized in that the electrode for ohmic contact is formed by vacuum evaporation, and the bump layer for bonding is formed by electrolytic plating. (3) A compound semiconductor substrate, a lower cladding layer, an active layer, and an upper cladding layer formed on this compound semiconductor substrate in this order, and a ridge stripe formed on this upper cladding layer and having side surfaces perpendicular to the substrate surface. A semiconductor laser comprising: a current confinement layer formed on both sides of the ridge stripe to have the same thickness as the height of the ridge stripe; and a cap layer formed on the ridge stripe and the current confinement layer. (4) A method for manufacturing a semiconductor laser according to claim (3), characterized in that the ridge stripe having side surfaces perpendicular to the substrate surface is formed by reactive ion etching using chlorine gas.