KR100248431B1 - High power semiconductor laser - Google Patents

Abstract

The present invention effectively dissipates the heat generated when the conventional 0.98㎛ semiconductor laser operates at high power, thereby reducing the oscillation wavelength change according to the temperature of the semiconductor laser and increasing the quantum efficiency to improve the characteristics of the semiconductor laser. The structure of the laser, the area in which light on the left and right sides of the active layer is not induced, the semiconductor laser chip is connected to the chip fixing substrate using solder, and the TEC for heat dissipation is connected to the chip fixing substrate. A semiconductor laser having was prepared.

Accordingly, the semiconductor laser of the present invention improves the efficiency of the semiconductor laser by providing a new type of heat dissipation structure that narrows the distance between the active layer and the metal layer, which is the main cause of heat generation, by etching the active layer regions on the left and right of the ridge. It became.

Description

High power semiconductor laser with new heat dissipation structure

SUMMARY OF THE INVENTION An object of the present invention is to provide a high power semiconductor laser having a new heat dissipation structure in which the external quantum efficiency is increased by effectively dissipating heat generated in the active layer of the semiconductor laser.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor lasers, and more particularly, to a high power semiconductor laser having a novel heat dissipation structure.

Semiconductor lasers oscillating in the wavelength range of 0.98㎛ used as the light source of the EDFA (Erbium Doped Fiber Amplifier) will increase the optical amplification rate as the light output increases.

For this purpose, a high-power semiconductor laser is an essential requirement. Effective control of the heat generated in the active layer, which is one of the factors that influence the characteristics of the semiconductor laser, is essential to stably output high light output.

In the conventional case, heat generated in the active layer was mainly transferred to the TEC (Thermoelectric Cooler: TEC) through the electrode via the cladding layer on the active layer.

In the case of the conventional semiconductor laser, since the heat generated from the active layer is transferred to the TEC through the cladding layer on the active layer, effective temperature control is difficult. As the light output is increased, the temperature is increased, and thus the oscillation wavelength is changed to decrease the quantum efficiency. There was a problem.

1 to 3 show a conventional method for fabricating a 0.98 탆 RWG (ridge waveguide) semiconductor laser.

Hereinafter, a method of manufacturing a semiconductor laser according to the prior art will be described with reference to FIGS. 1 to 3.

Referring to FIG. 1, a GaInAsP buffer layer (2), a GaInP clad layer (3), and a GaInAsP layer are provided on the GaAs compound semiconductor substrate (1) to prevent the flow of current due to the difference in the band gap between the GaAs and GaInP layers. Buffer layer (4), GaInAs / GaInAsP active layer (5), GaInAsP buffer layer (6), GaInP cladding layer (7), GaAs layer (8), GaInP cladding layer (9), GaInAsP for etch stop during ridge formation The buffer layer 10 and the GaAs ohmic layer 11 for forming ohmic contact are sequentially stacked using an organometallic vapor phase crystal growth apparatus (MOVPE: Metal Organic Vapor Phase Epitaxy).

Subsequently, as shown in FIG. 2, an Si ₃ N ₄ or SiO ₄ insulating film (not shown) is formed on the GaAs layer 11 to define an active region, and then patterned to form an active region of the GaAs layer 11. After the pattern is formed to expose a predetermined portion, the exposed GaAs layer 11, GaInAsP buffer layer 10, GaInP cladding layer 9, and GaAs layer 8 are sequentially removed by wet etching or dry etching. It is formed to have a width of 2 to 3 µm and a channel width of 20 µm.

Next, as shown in FIG. 3, the remaining Si ₃ N ₄ and SiO ₂ insulating films are removed to inject current into the ridge, and then the insulating film 12 made of Si ₃ N ₄ or SiO ₂ is exposed on the entire surface. ).

Subsequently, the insulating layer 12 is patterned by photolithography to expose the upper end of the ridge to form a current injection hole. Then, the p-side electrode 13 is deposited on the entire surface of the exposed substrate, and p is deposited through a plating process. The side electrode is formed to a thickness of 2 to 3 mu m.

Subsequently, the back surface of the n-GaAs substrate 1 is polished so that only about 100 μm is left, and the n-side electrode 14 is formed to complete the fabrication of a 0.98 μm RWG (Ridge Waveguide) semiconductor laser.

When the semiconductor laser is manufactured by the above method, when the current is injected into the semiconductor laser, the heat generated in the active layer passes through the cladding layer on the active layer and is transferred to the TEC outside the chip through the electrode (see path A of FIG. 6). The temperature is controlled through

Therefore, the conventional semiconductor laser as described above has a disadvantage in that the temperature is not effectively controlled and characteristics are deteriorated as the heat transfer path from the inside of the chip to the external cooling element is limited.

Therefore, in order to solve the problems according to the related art, the deterioration of characteristics due to heat at a high injection current of a high-power laser can effectively dissipate heat by forming a channel layer around the active layer and forming a thick metal film. To provide a semiconductor laser that stabilizes the oscillation wavelength and improves the light output.

The semiconductor laser according to the first embodiment of the present invention for achieving the above object is a GaInAsP buffer layer, GaInP cladding layer, GaInAsP buffer layer, active layer, GaInAsP buffer layer, GaInP cladding layer, GaAs layer for etching stop, GaInP on GaAs substrate A clad layer, a GaInAsP buffer layer, and a high concentration of GaAs ohmic layers for forming ohmic contacts are sequentially stacked, and recesses having a step at predetermined intervals from the GaAs ohmic contact layer to a predetermined depth of the GaInP clad layer under the active layer are formed. The ridge is formed, the p-side electrode connected to the GaAs ohmic layer of the ridge is formed on the upper surface, the n-side electrode is formed on the back surface of the substrate, and the p-side electrode of the semiconductor laser chip having the RWG structure is soldered. It is coupled to the chip fixing substrate by, characterized in that it has a structure in which the TEC is coupled to the chip fixing substrate.

In the semiconductor laser according to the second exemplary embodiment of the present invention for achieving the above object, a cladding layer, an active layer, a cladding layer, and an InGaAs ohmic layer for forming ohmic contact are formed on an InP substrate, and under the active layer from the ohmic layer. A recess having a step up to a predetermined depth of the cladding layer is formed. A recess is formed between the recesses by the formation of the recess, and the p-side electrode formed on the upper surface in contact with the ohmic layer of the ridge is formed on the rear surface of the substrate. A n-side electrode is formed, and a semiconductor laser chip having an RWG structure and a chip fixing substrate are connected by solder, and a TEC is connected to the solder as a heat sink.

1 is a semiconductor laser structure after primary growth for fabricating a conventional high power laser.

2 is a cross-sectional view of a semiconductor laser after an etching process for fabricating a conventional rigid waveguide (RWG) semiconductor laser.

3 is a cross-sectional view of a conventional RWG semiconductor laser after fabrication.

4 is a cross-sectional view of a semiconductor laser after an etching process for fabricating a high power laser of the present invention.

5 is a cross-sectional view after fabrication of the RWG semiconductor laser of the present invention.

6 is an assembly diagram and a heat transfer path diagram of the RWG semiconductor laser and TEC of the present invention.

* Description of the symbols for the main parts of the drawings *

1: Substrate 2: GaInAsP buffer layer

3: n-GaInP cladding layer 4: GaInAsP buffer layer

5: GaInAs / GaInAsP active layer 6: GaInAsP buffer layer

7: p-GaInP cladding layer 8: GaAs layer

9: p-GaInP clad layer 10: p-GaInAsP buffer layer

11: p + -GaAs ohmic layer 12: insulating film

13: p-side electrode 14: n-side electrode

15: insulating film 16: p-side electrode

17: n-side electrode 18: TEC

19: shoulder 20: chip fixing substrate

The semiconductor laser oscillating in the wavelength range of 0.98㎛ used as the light source of EDFA, the greater the light output, the higher the optical amplification factor. For this purpose, a high-power semiconductor laser is an essential requirement. Effective control of the heat generated in the active layer, which is one of the factors that influence the characteristics of the semiconductor laser, is essential to stably output high light output.

The present invention relates to a structure of a new semiconductor laser that facilitates heat dissipation by etching around the active layer by 1 μm in depth and 10 μm in width to effectively remove heat generated in the active layer of the conventional 0.98 μm semiconductor laser.

A detailed description of a method for manufacturing a semiconductor laser according to a first embodiment of the present invention with reference to Figures 4 to 6 as follows.

4 is a cross-sectional view of the manufacturing process of the semiconductor laser of the present invention, showing a state in which a recess having a step is formed to form a ridge.

The manufacturing fixation of the semiconductor laser of the present invention includes the same steps as those of the first and second drawings described with respect to the prior art.

That is, as shown in FIG. 4, the n-GaInAsP buffer layer 2 for preventing the flow of current due to the band gap difference between the GaAs and GaInP layers on the compound semiconductor substrate 1, which is an n-type GaAs substrate, n-GaInP cladding layer (3), GaInAsP buffer layer (4), active layer (5) formed of GaInAs / GaInAsP layer (MQW: Multiple Quantum Well), GaInAsP buffer layer (6), p-GaInP cladding layer (7), ridge The organometallic gas phase is in the order of the p-GaAs layer (8), the p-GaInP clad layer (9), the p-GaInAsP buffer layer (10), and the ohmic layer (11) made of GaAs for forming ohmic contact. Laminate in the same manner as in the prior art using the crystal growth equipment.

Subsequently, an Si ₃ N ₄ or SiO ₂ insulating film is formed on the ohmic layer 11 and patterned by a photolithography process so that the active layer has a width of 2-3 μm and a channel width of 20 μm (not shown). Next, the insulating film is removed by wet or dry etching from the exposed ohmic layer 11 to the p-GaAs layer 8 using the insulating film pattern as an etching mask, and the remaining insulating film pattern is removed from the HF etching solution. To remove.

Next, an insulating film (not shown) made of Si ₃ N ₄ or SiO ₂ is formed on the entire surface, and it is patterned by a photolithography process so that the GaInP clad layer 7 between the ridges is exposed to a width of 10 μm. The insulating film pattern is formed as much as possible.

At this time, the region exposed by the insulating layer pattern is formed so as to be located 1.5-2㎛ away from the side wall of the ridge. This is to ensure that the beam generated in the active layer is sufficiently guided without being disturbed by the electrode.

Subsequently, sulfuric acid-based (H ₂ SO ₄ : H ₂ O: H ₂ O ₂ ) to be etched from the exposed GaInP cladding layer 7 to a predetermined depth of the GaInP cladding layer 3 using the insulating film pattern as an etching mask. Selective wet etching using phosphoric acid (HCl: H ₃ PO ₄ ) or etching using a dry etching to a depth of 1㎛ to form a recess having a step in the space between the ridges.

Next, as shown in FIG. 5, after removing the insulating film pattern used as an etching mask, an insulating film 15 made of Si ₃ N ₄ or SiO ₂ is formed on the entire surface, and the insulating film 15 is formed by photolithography. By patterning, the surface of the ohmic layer 11 formed of the ridge top, for example, p ⁺ -GaAs, is exposed to a predetermined width to form a current injection hole.

Subsequently, metal is deposited on the entire surface of the exposed substrate, and the P-side electrode 16 is formed to have a thickness of 2-3 μm to withstand high current through the plating process.

Then, the back surface is polished so that the substrate 1 has a thickness of about 100 μm, and then the n-side electrode 17 is formed on the back surface of the substrate.

Subsequently, as shown in FIG. 6, the semiconductor laser chip on which the n-side electrode is formed is bonded to the chip fixing substrate 20 using a solder (conductive bonding material) 19, and the fixing substrate 20 To the TEC 18 for dissipating heat generated from the semiconductor laser to the outside, thereby manufacturing the semiconductor laser according to the present invention.

In addition, the manufacturing method of the semiconductor laser according to the second embodiment of the present invention will be described.

The manufacturing method of the semiconductor laser according to the second embodiment of the present invention includes some processes of the first embodiment described above, and the difference is that the semiconductor material layer formed on the compound semiconductor substrate 1 is manufactured by changing the layer of semiconductor material according to the desired wavelength range. A method of doing this is disclosed.

The semiconductor laser according to the second embodiment includes a cladding layer 3 formed of InP or AlGaAs on the compound semiconductor substrate 1 made of InP or GaAs, an active layer 5 formed of GaInAs / GaInAsP or AlGaAs / GaAs, and InP. Alternatively, the cladding layer 9 formed of AlGaAs and the ohmic layer 11 formed of InGaAs or GaAs are sequentially stacked, and the ohmic layer 11 is first etched by the same photolithography process as in FIG. An active layer is defined, and a recess having a step between the ridges is formed by etching the cladding layer 9, the active layer 5, and the cladding layer 3 between the ridges by a secondary photolithography process.

Subsequently, a subsequent process is performed in the same manner as in the first embodiment to manufacture a semiconductor laser. For example, except for the type of semiconductor material layer formed on the substrate 1 and the number of material layers stacked in the second embodiment, the remaining process conditions are the same as in the first embodiment.

As shown in FIG. 6, the semiconductor laser of the present invention manufactured with the structure as described above is connected to the channel newly formed by the solder 19, so that the heat generated in the active layer is adjacent to the active layer in comparison with the conventional semiconductor laser. It is easily delivered to the TEC 18 through the formed metal electrode 16 (B or C path).

In addition, since the heat dissipated to the cladding layer under the active layer 5 is also dissipated through the metal electrode 16, the heat emitted to the left and right of the active layer 5 is increased more than before, thereby enabling effective temperature control.

Embodiments of the present invention are equally applicable to 0.98 탆 semiconductor lasers and 1.48 탆 semiconductor lasers as excitation light sources for optical fiber amplifiers, as well as semiconductor lasers oscillating at different wavelengths.

Accordingly, the present invention provides a high power semiconductor laser structure that has stable wavelength characteristics even at high power operation as the heat is effectively released and the light output is improved compared to the conventional structure under the same applied current conditions.

The semiconductor laser oscillating in the wavelength range of 0.98㎛ is used as a light source of Er-added fiber-optic amplifier EDFA (Erbium Doped Fiber Amplifier) to amplify the signal passing through the optical fiber. Therefore, the greater the light output of the 0.98㎛ semiconductor laser, the higher the optical amplification factor of EDFA.

For this purpose, the fabrication of a 0.98㎛ semiconductor laser capable of high light output is important.

In particular, for use in EDFA, improving the light output of semiconductor laser is one of the important factors in the production of EDFA module. In order to obtain high light output, the applied current must be improved, so that the temperature of the active layer is gradually increased.

As a result, the characteristics of the device deteriorate, such as the wavelength of the output beam changes and the external quantum efficiency decreases. In order to solve this problem, in the present invention, the heat generated in the active layer is effectively removed in the high power operation to solve the problem caused by the wavelength change with temperature and improve the light output characteristics of the device.

Channels were formed around the active layer to effectively dissipate heat generated in the active layer. To this end, an insulating film was formed on the entire surface after etching to form a ridge by the conventional method, and a channel having a width of 10 μm and a depth of 1 μm was formed on the left and right sides of the active layer in the resonator length direction through a photolithography process.

Accordingly, heat generated in the active layer is easily dissipated to the TEC 18 through the metal layers on the left and right sides of the active layer, so that the misconduct around the active layer 5 is controlled faster than in the conventional case.

The effects of the present invention are as follows. Heat generation is facilitated by forming channels around the active layer to generate high heat around the active layer generated by the high-power semiconductor laser. First, the oscillation wavelength of the semiconductor laser is stabilized. Second, semiconductor laser characteristics such as quantum efficiency increase of the semiconductor laser. You can expect an improvement.

Claims (9)

GaInAsP buffer layer (2), GaInP cladding layer (3), GaInAsP buffer layer (4), GaInAs / GaInAsP active layer (5), GaInAsP buffer layer (6), GaInP cladding layer (7), on GaAs substrate (1) A GaAs layer 8, a GaInP cladding layer 9, a GaInAsP buffer layer 10, and a high concentration of GaAs ohmic layer 11 for forming ohmic contact are sequentially stacked, and the channel around the active layer 5 is a sidewall of the ridge. A ridge is formed by forming a recess having a step at a predetermined interval from the GaAs ohmic layer 11 to a predetermined depth from the GaAs ohmic layer 11. The p-side electrode 16 is formed to be connected to the GaAs ohmic contact layer 11 of the ridge, and the n-side electrode 17 is formed on the back surface of the substrate 1 to form the p-side electrode of the semiconductor laser chip having the RWG structure. (16) is coupled to the chip holding substrate 20 by the solder 19, the TEC (18) is coupled to the substrate 20 has a structure High-output semiconductor laser having a heat radiating structure according to claim. The method of claim 1, A high power semiconductor laser having a heat dissipation structure, characterized in that the depth of the recess formed from the thin GaInP cladding layer 7 to the GaAs cladding layer 3 is 1 탆. The method of claim 1, The n-side electrode 16 is a high power semiconductor laser having a heat radiation structure, characterized in that formed in a thickness of 2-3㎛. The method of claim 1, The recessed portion is a high power semiconductor laser having a heat dissipation structure, characterized in that formed by using selective wet etching or dry etching. The cladding layer 3, the active layer 5, the cladding layer 9 and the ohmic layer 11 for forming ohmic contact are formed on the substrate 1, and the channel around the active layer 5 is formed from the sidewall of the ridge. 1.5-2 micrometers apart, the recessed part which has a level | step difference from the said ohmic layer 11 to the predetermined depth of the cladding layer 3 is formed, The formation of the said recessed part provides the ridge between recessed parts, The said ridge A semiconductor laser chip having an RWG structure and a chip fixing substrate 20 having a p-side electrode 16 formed on an upper surface and an n-side electrode 17 formed on a rear surface of the substrate 1 in contact with the ohmic layer 11 of the substrate 1. ) Is connected by a solder (19), and TEC (18) is connected to the solder as a heat sink. The method of claim 5, The substrate is InP or GaAs, the cladding layers 3, 7, 9 are InP or AlGaAs, the active layer 5 is InGaAs / InP, InGaAs / InGaAsP or AlGaAs / GaAs multilayer quantum well structure, and the ohmic layer 11 is InGaAs or A high power semiconductor laser having a heat dissipation structure, characterized in that formed of GaAs. The method of claim 5, A high power semiconductor laser having a heat dissipation structure, characterized in that the concave portion formed from the cladding layer (7) to the cladding layer (3) below the active layer has a width of 10 m and a depth of 1 m. The method of claim 5, The n-side electrode 16 is a high power semiconductor laser having a heat radiation structure, characterized in that formed in a thickness of 2-3㎛. The method of claim 5, The recessed portion is a high power semiconductor laser having a heat dissipation structure, characterized in that formed by using a selective wet etching or dry etching.