JP2008141039A - Edge emitting semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an edge emitting semiconductor laser wherein cleavage can be carried out even if a plating layer is provided to a surface and heat dissipation property of a resonator edge face is improved. <P>SOLUTION: An n-type clad layer 3, an active layer 4, a p-type clad layer 5, an n-type current constriction layer 6 and a p-type contact layer 7 are formed on a substrate 2. An n-electrode 1 is formed in a rear of the substrate 2, and a p-electrode 8 is formed on the p-type contact layer 7. A plating layer 9 is formed on the p-electrode 8 from one edge face of a resonator to the other edge face thereof. The width of the plating layer 9 formed in an edge face part is made smaller than the width of the plating layer 9 formed in a central part. Consequently, it is possible to improve heat dissipation property of an edge face and to carry out cleavage in an edge face position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an edge-emitting semiconductor laser having a plating layer on the surface.

  As a semiconductor laser, an edge-emitting laser has been well known. For example, as shown in Patent Document 1 and Patent Document 2, an edge-emitting laser has an n-type AlGaAs cladding layer, an active layer, a p-type AlGaAs cladding layer, and an n-type AlGaAs current blocking layer on an n-type GaAs substrate. And p-type contact layer. An n-electrode is formed on the back surface of the n-type GaAs substrate, and a p-electrode is formed on the top surface of the p-type GaAs contact layer.

  In order to bond the semiconductor laser chip to a substrate or the like with solder or the like, a plating layer such as Au is provided on either the n electrode or the p electrode.

  When a plated layer is formed on an electrode, the semiconductor laser structure as described above is formed on one wafer and a plated layer is formed on one electrode in order to produce a large number of chips at once. And then cleaved to separate.

FIG. 8 shows a part of a wafer having an edge-emitting semiconductor laser structure as viewed from the electrode side, and shows the structure of a conventional plating layer. In order to separate the wafer from the wafer as shown in FIG. 8 for each chip, it is necessary to cleave along the cleavage position 23 (the broken line position in the figure). Therefore, the plating layer 22 is not formed continuously on the electrode 21 so as to be cleaved, but is formed separately at a predetermined interval, and the plating layer 22 is not provided near the cleavage position 23. I was doing.
JP-A-60-201687 Japanese Utility Model Publication No. 61-100165

  However, in the structure in which the plating layer 22 is not provided in the vicinity of the cleavage position 23 as in the above-described prior art, the cleavage can be performed, but the heat dissipation at the end face of the semiconductor laser chip after separation becomes worse, and COD (Catastrophic Optical Damage) There is a problem that destruction tends to occur. In particular, depending on the constituent material of the semiconductor laser (for example, an AlGaInP laser), the light absorption at the end face increases, the temperature rises significantly, and optical damage is likely to occur.

  The present invention was devised in order to solve the above-described problems. An edge-emitting semiconductor laser that can be cleaved even if a plating layer is provided on the surface and has improved heat dissipation of the resonator end face is provided. It is intended to provide.

  In order to achieve the above object, an invention according to claim 1 is an edge-emitting semiconductor laser in which a plating layer is formed on the surface from one end face of the resonator to the other end face, and the plating layer The edge-emitting semiconductor laser is characterized in that the width of the end is narrower than the width of the center.

  According to a second aspect of the present invention, in the edge-emitting semiconductor laser according to the first aspect, the end portion of the plating layer is formed at a position corresponding to a ridge structure that performs current confinement. .

  The invention according to claim 3 is characterized in that the width of the end face of the plating layer is 1/2 or less of the width of the central portion. This is an edge-emitting semiconductor laser.

  According to a fourth aspect of the present invention, in the edge-emitting semiconductor laser according to any one of the first to third aspects, the shape of the plating layer is a cross shape or an octagonal shape. .

  According to the present invention, since the plating layer is formed on the element surface from one end face to the other end face of the resonator, heat dissipation at the end face is ensured, and COD breakdown can be prevented. On the other hand, since the width of the end portion of the plated layer is narrower than the width of the central portion of the plated layer, it is possible to cleave to form the end face of the resonator.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an edge emitting semiconductor laser of the present invention. FIG. 2 is a plan view of FIG. 1 as viewed from above. An n-type cladding layer 3, an active layer 4, a p-type cladding layer 5, an n-type current confinement layer 6, and a p-type contact layer 7 are formed on a substrate 2. A p-electrode 8 is formed on the p-type contact layer 7.

  The active layer 4 is an active layer having a quantum well structure, and has a structure in which a well layer (well layer) is sandwiched between barrier layers (barrier layers) having a larger band gap than the well layer. ing. The quantum well structure may be multiplexed instead of one. In this case, an MQW (Multi Quantum Well), that is, a multiple quantum well structure is formed.

  Here, a configuration example of each layer of the edge emitting semiconductor laser of FIG. 1 is shown. The substrate 2 is an n-type GaAs substrate, the n-type cladding layer 3 is an n-type AlGaInP, the active layer 4 is a GaInP well layer and an undoped AlGaInP barrier. A multi-quantum well structure in which several layers are alternately stacked, the p-type cladding layer 5 is composed of p-type AlGaInP, the n-type current confinement layer 6 is composed of n-type AlInP, and the p-type contact layer 7 is composed of p-type GaAs. The active layer 4 may have a structure including an AlGaInP light guide layer. Further, Si is used as the n-type dopant, and Mg is used as the p-type dopant. The p-electrode 8 is made of a Ti / Au multilayer metal film or the like, and the n-electrode 1 is made of an Au / Ge / Ni alloy layer, Ti / Au multilayer metal film or the like. The above configuration is merely an example of an edge emitting semiconductor laser, and is not limited to these composition materials.

  The edge-emitting semiconductor laser shown in FIG. 1 has a p-type cladding layer 5 formed with a striped ridge portion, an n-type current confinement layer 6 disposed on both sides of the ridge portion, and the p-type cladding layer 5 and the current confinement. The layer 6 has a buried ridge structure in which the p-type contact layer 7 is covered.

  Light is confined in the horizontal direction by the difference between the refractive index of the ridge portion and the refractive index of the n-type current confinement layer 6 disposed on the side surface of the ridge. The current does not flow in the n-type current confinement layer 6 serving as a reverse bias and the lower portion thereof, but flows in the striped ridge portion.

  When a current is applied between the p electrode 8 and the n electrode 1, the current is confined by the current confinement layer 6, and light emission is obtained from the central portion of the active layer 4 corresponding to the lower position of the ridge portion. The emitted light is reflected by the end face A and the end face B constituting the laser resonator, reciprocates between them to generate laser oscillation, and is emitted as a laser beam from one of the end faces to the outside.

  By the way, a plating layer 9 made of a metal such as Au (gold) is formed on the p-electrode 8 from one end face to the other end face. The plating layer 9 has a cross shape, and as shown in FIG. 2, the width X3 of the plating layer 9 formed at the end surface portion is smaller than the width X2 of the plating layer 9 formed at the center portion. is doing. By doing in this way, while improving the heat dissipation of an end surface, it enables it to cleave at an end surface position.

  An example of dimensions when the plated layer 9 is Au is 200 μm, Y1 is 910 μm, the thickness of the plated layer 9 is 3 μm to 5 μm, X2 is 120 μm, Y2 is 810 μm, and X3 is 50 μm. The width of the ridge portion is 2 to 3 μm.

  The narrow plating layer region formed on the end face of the resonator indicated by X3 in FIG. 2 has poor heat dissipation at the end face if it is too long in the direction of the resonator, and can cope with cleavage position errors if it is too short. Since it will disappear, it is set to an appropriate length. In addition, if the width X3 of the end portion of the plating layer 9 is too large, cleavage cannot be performed. Therefore, the width X3 is preferably less than or equal to half the width X2 of the central portion of the plating layer 9.

  Furthermore, since the active layer 4 immediately below the ridge portion of the p-type cladding layer 5 emits light, heat generation is concentrated in this portion. Therefore, in order to efficiently dissipate heat, the width X3 of the end portion of the plating layer 9 is It is desirable to form so as to include the entire width of the ridge portion serving as a current path.

  FIG. 3 shows the relationship with the cleavage position when the plating layer 9 shown in FIG. 2 is continuously formed on each element on the wafer on which the edge emitting semiconductor laser elements are continuously formed. Since the width of the plating layer 9 at the cleavage position 15 is made narrower than that of the central portion, cleavage separation can be performed.

  FIG. 4 shows an edge-emitting semiconductor laser having the same layer structure as that shown in FIG. 2 but having a different layer structure. The same reference numerals as those in FIG. 1 indicate the same configurations. Compared to FIG. 1, the other layer structure is the same except that the p-type contact layer 7 is not provided in FIG.

  By not providing the p-type contact layer 7, it is possible to suppress light absorption due to distortion and defects due to thermal expansion due to the p-type contact layer 7. Further, the p-electrode 8 is in contact with the ridge portion of the p-type cladding layer 5 and the n-type current confinement layer 6, so that heat generated immediately below the ridge portion is more easily transmitted to the end portion of the plating layer 9 than in FIG. There is also an advantage that the heat dissipation effect is improved.

  Next, FIG. 5 shows another structure of the plating layer 9. In FIG. 5, the plating layer 9 formed on the p-electrode 8 has an octagonal shape. The example of dimensions is the same as FIG. 1, X1 is 200 μm, Y1 is 910 μm, the thickness of the plating layer 9 is 3 μm to 5 μm, X2 is 120 μm, Y2 is 810 μm, and X3 is 50 μm. In this way, by gradually narrowing the plated layer from the center to the end, heat dissipation of the resonator end face is ensured and cleavage can be performed.

  The manufacturing method of the edge emitting semiconductor laser of the present invention will be described below. The structure of the plating layer 9 is that shown in FIG. First, the n-type cladding layer 3, the active layer 4, and the p-type cladding layer 5 are epitaxially grown on the substrate 1 which becomes a large wafer by MOCVD or the like. The number of chips is formed in stripes on the p-type cladding layer 5 with the laser cavity direction (stripe direction of the ridge portion) as the longitudinal direction.

  The p-type cladding layer 5 is formed in a ridge shape by the number of chips by wet etching. The n-type current confinement layer 6 is selectively grown again by the MOCVD method or the like again. After the previous mask is lifted off, the p-type contact 7 is grown. Finally, the wafer is made to have a desired thickness by lapping and polishing, and an n-electrode 1 and a p-electrode 8 and a plating layer 9 made of Au or the like are formed by vapor deposition or the like.

  With the above manufacturing method, a large number of chips having the structure of FIG. 1 are arranged on one wafer. FIG. 6 shows this state. The wafer 12 shows a state in which a large number of chips having the structure of FIG. 1 are formed, and is a view as seen from the plated layer 9 side.

  Here, the line shown with the broken line is the cleavage position 16 for the first cleavage. Each of the marking positions 16 indicated by a broken line is marked with an inscription, and then separated by cleavage. FIG. 7 shows a state where the chips are arranged in a line by this separation. As shown in FIG. 7, by the first cleavage separation, a reflective coat (reflective film) is formed on both cleavage surfaces (resonator end faces A and B) constituting the resonator in a state where chips are arranged in a line. An AR coat (low reflection film) 10 is formed on the laser light emission end face side, and an HR coat (high reflection film) 11 is formed on the opposite side of the laser light emission end face.

For example, alumina or the like is used for the AR coat 10, and the HR coat 11 is a multilayer film in which SiO ₂ and TiO ₂ are alternately stacked for 3 to 4 cycles, or SiO ₂ and ZrO ₂ are alternately 3 to 4 cycles. A laminated multilayer film or the like is used.

Next, a second cleavage is performed to form the final chip. As in the case of FIG. 6, the cleavage is separated at the broken line position by putting an inscription on the broken cleavage position 17 and tapping it. Then, the edge emitting semiconductor laser of FIG. 1 is completed.

It is a perspective view which shows an example of a structure of the edge-emitting semiconductor laser of this invention. It is the top view which looked at the edge emitting semiconductor laser of FIG. 1 from the upper surface. It is a figure which shows the structure of the plating layer in the some chip | tip formed in the wafer. It is a perspective view which shows an example of the other structure of the edge-emitting type semiconductor laser of this invention. It is a figure which shows the other structure of a plating layer. It is a figure which shows the some chip | tip which has the plating layer formed in the wafer. It is a figure which shows the some chip | tip which has the plating layer formed in the wafer after the 1st cleavage. It is a figure which shows the structure of the conventional plating layer.

Explanation of symbols

1 n-electrode 2 substrate 3 n-type cladding layer 4 active layer 5 p-type cladding layer 6 n-type current confinement layer 7 p-type contact layer 8 p-electrode 9 plating layer

Claims (4)

An edge-emitting semiconductor laser in which a plating layer is formed on the surface from one end face of the resonator to the other end face,
The edge-emitting semiconductor laser according to claim 1, wherein a width of an end portion of the plated layer is narrower than a width of a central portion.   2. The edge-emitting semiconductor laser according to claim 1, wherein an end portion of the plating layer is formed at a position corresponding to a ridge structure that performs current confinement.   3. The edge-emitting semiconductor laser according to claim 1, wherein the width of the end portion of the plated layer is ½ or less of the width of the central portion.   4. The edge-emitting semiconductor laser according to claim 1, wherein the plated layer has a cross shape or an octagonal shape. 5.

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