JP2010034267A - Broad-area type semiconductor laser device, broad-area type semiconductor laser array, laser display, and laser irradiation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a broad-area type semiconductor laser device that prevents the deterioration caused from the side of a current narrowing structure at a high power operation. <P>SOLUTION: A width of a ridge 20 is constant in an oscillator direction, and a modulation structure 2 between a wide region 31 and a narrow region 32 is formed on a contact layer 19. In the wide region 31, the contact layer 19 has the same width as the ridge 20. At the same time, the narrow region 32 is provided with a notch 19A on the contact layer 19 and the width of the contact layer 19 becomes smaller than that of the ridge 20. In the narrow part 32, a current is not injected, and a gain is reduced. A first impurity diffusion region 33 is formed to the notch 19A of the narrow region 32 in a part of a layer other than the contact layer 19 of a semiconductor multilayer structure 10A. In the first impurity diffusion region 33, a band gap is expanded by impurity diffusion to suppress heat generation by light absorption and to prevent the deterioration caused from the side of the ridge 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a broad area type semiconductor laser device and a broad area type semiconductor laser array having the same. The present invention also relates to a laser display and a laser irradiation apparatus using them.

  The so-called broad area type semiconductor laser with an expanded waveguide width, that is, a stripe width, is a compact, highly reliable, low-cost, high-power laser light source that can be used as a display, printing device, optical disk initialization device, material processing or medical treatment. It is used in various fields. In general, in a semiconductor laser called a broad area type, the stripe width is at least 5 μm, most of which is 10 μm or more and about several hundred μm at the maximum.

  Recently, in these application fields, high output is often desirable, and there is an increasing demand for high-power semiconductor lasers. Although it is possible to increase the output by increasing the amount of injected current, conventionally, if the amount of injected current is increased too much, there has been a problem in that the laser output is adversely affected, such as a decrease in light output due to heat storage. . However, with the recent improvement in quantum efficiency, the problem of decreasing optical output has been solved, and recently, COD (Catastrophic Optical Damage) due to an increase in photon density at the cleavage plane constituting the optical resonator has been solved. It has become a problem.

  By the way, the NFP (Near Field Pattern) of the broad area type semiconductor laser is a superposition of many transverse modes, and the top hat type in which the light intensity under the ridge (current confinement structure) is almost constant is ideal. . Under a driving condition where the light output is constant, the maximum photon density at the end face is the lowest in the top hat type. On the other hand, when the top hat type is disturbed and several peaks appear in the NFP, the light is concentrated on the peak, so that the maximum photon density is increased. It is known that COD in a broad area type semiconductor laser occurs only at a part of the end face. That is, local COD occurs at the peak position of NFP (see, for example, Non-Patent Document 1).

  One method for increasing the COD resistance of such a broad area type semiconductor laser is to bring NFP closer to a top hat type. In the broad area type semiconductor laser, it is known that the refractive index at the center of the ridge is lowered due to the plasma effect by the injection current (see, for example, Patent Document 2). Therefore, in a non-absorbing dielectric film embedded ridge structure such as a narrow stripe type semiconductor laser having a stripe width of about several μm, the lateral refractive index distribution is low-high-low-high-low, so The side peak where the NFP becomes strong becomes remarkable. When such a side peak appears, the photon density partially increases and COD tends to occur. Therefore, a loss guide structure using a metal-embedded ridge structure has been reported as a technique for realizing a top hat type NFP in a broad area type semiconductor laser. In this structure, the generation of a peak is suppressed by increasing the absorption loss at the site where the side peak occurs.

As another method for increasing the COD tolerance of the broad area semiconductor laser, it is also effective to form an impurity diffusion window structure for suppressing the end face COD. This is a technique widely used in narrow stripe type semiconductor lasers. In a semiconductor laser including an As-based active layer having an oscillation wavelength in the near-infrared region and a P-based active layer having an oscillation wavelength in the red band, an end face is used. In addition, impurities such as Zn and Si are diffused in the vicinity thereof (see, for example, Patent Document 1 and Patent Document 2). In this way, by diffusing impurities in the end face and in the vicinity thereof, the group III atoms are mainly replaced with the impurities to perform the ordering of the active layer, and the band gap of the active layer where the impurities are diffused is activated. The band gap of the region where the impurity is not diffused (gain region) in the layer is made larger, and the laser beam generated in the gain region of the active layer is absorbed at the end face and in the vicinity thereof, and the rate of conversion into heat is reduced. ing.
M. Bou Sanayeh, et al. , "Temperature-power dependence of catastrophic optical damage in AlGaInP laser diodes", Applied Physics Letters, 2007, 91, 041115. T. Asatsuma, et al., Proc. SPIE, 2006, 6104, 61040C Japanese Patent No. 3718952 JP 2006-294879 A

  However, as a result of experiments by the present inventor, when an impurity diffusion window structure is employed in a broad area type semiconductor laser, it has been clarified that COD occurs at another location during high output driving. The substrate of the deteriorated broad area type semiconductor laser is removed by etching, and the active layer under the ridge stripe is measured by the CL (Cathode Luminescence) method. As a result, it is found that DLD (Dark Line Defect) occurs from the side of the ridge. It was.

  Such deterioration is a phenomenon peculiar to a broad area type semiconductor laser in which NFP is a superposition of a large number of transverse modes. As described above, a broad area type semiconductor laser is ideally a top hat type in which the light intensity under the ridge is almost constant, and a loss guide structure is adopted. Therefore, it is considered that DLD was generated by heat generation due to light absorption on the side surface of the ridge. On the other hand, in a narrow stripe semiconductor laser with a non-absorbing dielectric film embedded ridge structure that oscillates in the transverse fundamental mode, the photon density is maximized at the center of the ridge, so that no DLD occurs on the side of the ridge due to side peaks.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a broad area type semiconductor laser element capable of suppressing deterioration from the side of the current confinement structure during high output operation and a broad having the same. It is an object to provide an area type semiconductor laser array, and a laser display and a laser irradiation apparatus using them.

  The broad area type semiconductor laser device of the present invention has a plurality of layers including an active layer on a substrate, and a current injected into the active layer in a part including the uppermost contact layer among the plurality of layers. A semiconductor layered structure in which a band-shaped current confinement structure to be confined is formed, and a pair of end faces facing the extending direction of the current confinement structure with the active layer and the current confinement structure in between, and the contact layer has a current confinement structure And a narrow region that is narrower than the current confinement structure by providing a cut, and a part of the semiconductor stacked structure other than the contact layer is used to cut the narrow region. A first impurity diffusion region formed and having a band gap larger than the energy corresponding to the emission wavelength of the active layer, and at least one of the pair of end faces and the vicinity thereof; And it has a second impurity diffusion regions having a larger band gap than the corresponding energy.

  The broad area type semiconductor laser array of the present invention has a plurality of broad area type semiconductor laser elements, and each of the plurality of broad area type semiconductor laser elements is constituted by the broad area type semiconductor laser element of the present invention. It is what has been.

  The laser display of the present invention includes a broad area type semiconductor laser array having a plurality of broad area type semiconductor laser elements, and each of the plurality of broad area type semiconductor laser elements is a broad area type semiconductor laser element of the present invention. A semiconductor laser element is used.

  A laser irradiation apparatus of the present invention includes a broad area type semiconductor laser array having a plurality of broad area type semiconductor laser elements, and each of the plurality of broad area type semiconductor laser elements is a broad area of the present invention. Type semiconductor laser element.

  In the broad area type semiconductor laser device according to the present invention, the contact layer has a wide region having the same width as that of the current confinement structure and a narrow region in which the width is narrower than that of the current confinement structure by providing the cut. Therefore, in a narrow region, no current is injected and the gain is reduced. In addition, since the first impurity diffusion region is formed in the narrow region cut in a part of the semiconductor stacked structure other than the contact layer, the band gap is expanded by impurity diffusion in the first impurity diffusion region, Heat generation due to light absorption is suppressed. Therefore, deterioration from the side of the current confinement structure is suppressed during high output operation. Therefore, if this broad area type semiconductor laser array is used to form a broad area type semiconductor laser array, it is possible to obtain high output with a small number of elements, and applications such as laser displays or laser irradiation devices that require high output. It is very suitable for.

  According to the broad area type semiconductor laser device of the present invention, a narrow region is provided in the contact layer, and the first impurity diffusion region is provided in the cut of the narrow region. In addition, the heat generation due to light absorption can be suppressed, and deterioration from the side of the current confinement structure during high output operation can be suppressed. Therefore, if this broad area type semiconductor laser array is used to form a broad area type semiconductor laser array, it is possible to obtain high output with a small number of elements, and applications such as laser displays or laser irradiation devices that require high output. It is very suitable for.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a schematic configuration of a broad area type semiconductor laser device 1 according to an embodiment of the present invention. FIG. 2 shows a planar configuration of the front end surface S1 and the rear end surface S2 of the broad area type semiconductor laser device 1 shown in FIG. FIG. 3 shows a cross-sectional configuration of the broad area type semiconductor laser device 1 shown in FIG. 1 in the direction of arrows III-III (resonator direction).

  This 1 element of a broad area type semiconductor laser has a buffer layer 11, a lower cladding layer 12, a lower guide layer 13, an active layer 14, an upper guide layer 15, an upper cladding layer 16A, a stop layer 17, an upper cladding layer on a substrate 10. 16B, the intermediate layer 18 and the contact layer 19 are provided with a semiconductor multilayer structure 10A formed by laminating in this order from the substrate 10 side. A stripe-shaped ridge portion 20 is formed in the upper portion of the semiconductor multilayer structure 10A, specifically, in the upper cladding layer 16B, the intermediate layer 18, and the contact layer 19. The ridge portion 20 has a function as a current confinement structure for confining the current injected into the active layer 14. In the broad area type semiconductor laser device 1, the width of the ridge portion 20 is 10 μm or more, typically 50 μm or more and 400 μm or less.

  The substrate 10 is made of, for example, n-type GaAs. The buffer layer 11 is made of, for example, n-type GaInP. The lower cladding layer 12 is made of, for example, n-type AlInP. Here, as an n-type impurity contained in each of the above layers, for example, silicon (Si) can be cited.

  The lower guide layer 13 is made of, for example, non-doped AlGaInP. The active layer 14 is made of, for example, non-doped GaInP. In this active layer 14, a region facing the ridge portion 20 becomes a light emitting region 14A. The light emitting region 14A corresponds to a current injection region into which a current confined by the ridge portion 20 is injected. The upper guide layer 15 is made of, for example, non-doped AlGaInP.

  The upper clad layers 16A and 16B are made of, for example, p-type AlInP, and the upper clad layer 16B is provided at the bottom of the ridge portion 20. The stop layer 17 is made of, for example, p-type GaInP, and functions as an etching stop layer when forming the ridge portion 20 in a manufacturing process described later. The intermediate layer 18 is made of, for example, p-type GaInP, and is provided between the upper cladding layer 16 </ b> B and the contact layer 19 in the ridge portion 20. Here, as a p-type impurity contained in each said layer, magnesium (Mg) is mentioned, for example. The contact layer 19 is made of, for example, p-type GaAs, forms the uppermost layer of the semiconductor multilayer structure 10A, and is provided on the uppermost portion (upper surface) of the ridge portion 20. Here, the p-type impurity contained in the contact layer 19 includes an impurity different from the impurity contained in each of the above layers, for example, zinc (Zn), and the concentration thereof is, for example, 1 × 10 18 atoms / cm 3 to 3 × 10 19 atoms / cm 2. The concentration is as high as cm3.

  The width of the ridge portion 20, that is, the width of the intermediate layer 18 and the upper cladding layer 16B is constant in the resonator direction. On the other hand, the contact layer 19 has the modulation structure 2 as shown in FIG. 4, and its width changes in the direction of the resonator. That is, the contact layer 19 includes a wide area 31 having a wide width and a narrow area 32 having a narrow width.

  In the wide region 31, the width of the contact layer 19 is substantially the same as the width of the ridge portion 20, that is, the intermediate layer 18 and the upper cladding layer 16B. Here, “substantially the same” is because when the ridge portion 20 is formed by selective wet etching, the slope becomes gentle and a difference of about 0.5 μm occurs.

  On the other hand, in the narrow region 32, the contact layer 19 is provided with a cut 19 </ b> A, so that the width of the contact layer 19 is narrower than the width of the ridge portion 20. Further, in a part other than the contact layer 19 of the semiconductor stacked structure 10A (for example, the intermediate layer 18 to the lower guide layer 13), a notch 19A in the narrow region 32 is formed with zinc (Zn), as shown in FIG. A first impurity diffusion region 33 in which impurities such as magnesium (Mg) and silicon (Si) are diffused is formed. The first impurity diffusion region 33 has a band gap larger than the energy corresponding to the emission wavelength of the active layer 14. Thereby, in this broad area type semiconductor laser device 1, the deterioration from the side surface of the ridge portion 20 can be suppressed during the high output operation.

  The difference dW (total width of the narrow regions 32 on both sides of the ridge 20) between the maximum width W31 (width in the wide region 31) and the minimum width W32 (width in the narrow region 32) of the contact layer 19 is, for example, 4 μm or more. Preferably, 4 μm ≦ dW ≦ 20 μm is more preferable. When the thickness is less than 4 μm, a sufficient gain is generated in the narrow region 32 due to current diffusion in the ridge portion 20 (for example, the upper cladding layer 16B or the upper guide layer 15), and the side peak of NFP is not sufficiently suppressed. This is because deterioration from the side surface of the portion 20 is likely to occur. Further, if it is larger than 20 μm, the NFP at the center of the ridge portion 20 tends to become strong, and it becomes difficult to obtain a top hat shape.

  The cuts 19A are desirably provided symmetrically on the left and right sides of the ridge portion 20 in the width direction (the direction perpendicular to the resonator direction and the stacking direction). This is to adjust the left-right balance of NFP. Further, the width of the narrow region 32 may be different on both sides of the ridge portion 20. In this case, however, the difference dW between the maximum width W31 (width in the wide region 31) and the minimum width W32 (width in the narrow region 32) of the contact layer 19 is, for example, 4 μm or more as described above. Preferably, 4 μm ≦ dW ≦ 20 μm is more preferable.

  The narrow regions 32 are preferably formed at a plurality of locations (three locations in FIG. 1) in the extending direction of the ridge portion 20. The reason is as follows. When only one narrow region 32 is formed, if the length of the narrow region 32 in the resonator direction (hereinafter simply referred to as the length) is too short, a sufficient gain is obtained in the narrow region 32 due to current diffusion in the ridge portion 20. This is because the NFP side peak is not sufficiently suppressed, and deterioration from the side surface of the ridge portion 20 is likely to occur. On the other hand, when only one narrow region 32 is formed and the length thereof is increased, the transverse mode is drawn into the narrow region 32, and the NFP has a shape close to gain guide oscillation. Therefore, it is desirable to form narrow regions 32 having appropriate lengths at a plurality of locations in the ridge portion 20.

  Specifically, the length of the narrow region 32 is preferably not less than 10 μm and less than 200 μm, for example. If the thickness is less than 10 μm, it is difficult to perform impurity diffusion with good controllability in the manufacturing process described later. Further, when the length is longer than 200 μm, the pulling of the transverse mode into the narrow region 32 becomes strong as described above.

  Further, the upper surface of the semiconductor multilayer structure 10A (the upper surface and both side surfaces of the ridge portion 20 and the surface of the stop layer 17 other than the portion facing the ridge portion 20) other than the central portion of the ridge portion 20 A buried layer 21 is formed. The buried layer 21 is made of a dielectric material such as SiO2, SiN, Al2 O3, TiO2, Ta2 O3, ZrO2. As a result, a real index guide structure with a low absorption loss is formed on the side surface of the ridge portion 20 by the buried layer 21 made of a dielectric, and the resonator has a synergistic effect with the first impurity diffusion region 33 described above. The absorption loss near the side surface of the ridge portion 20 averaged in the direction can be further reduced, and the side peak near the side surface of the ridge portion 20 of NFP can be suppressed.

  The buried layer 21 has an opening (not shown) in a region facing the central portion of the ridge portion 20. The edge of the opening may be on the upper surface of the ridge portion 20, but is desirably 5 μm or less from the edge of the contact layer 19 regardless of the wide region 31 or the narrow region 32. If the overlap between the buried layer 21 and the contact layer 19 is 5 μm or more, the contact area between the upper electrode 22 and the contact layer 19 to be described later decreases, so that the contact resistance increases or the current spread in the contact layer 19 is not sufficient. This is because problems such as concentration of NFP in the center of the ridge portion 20 may occur.

  Further, the broad area type semiconductor laser device 1 has a pair of end faces, that is, a front end face S1 and a rear end face S2, which are opposed to each other in the extending direction of the ridge part 20 between the active layer 14 and the ridge part 20. That is, the broad area type semiconductor laser device 1 is an edge emitting semiconductor laser having a resonator constituted by a front end face S1 and a rear end face S2. The front end surface S1 and the rear end surface S2 are covered with a dielectric film (not shown).

  A second impurity diffusion region 30 in which an impurity such as zinc (Zn) is diffused is formed in at least one of the front end surface S1 and the rear end surface S2 (both in FIG. 1 to FIG. 3) and in the vicinity thereof. The second impurity diffusion region 30 has a band gap larger than the energy corresponding to the emission wavelength of the active layer 14.

  The contact layer 19 in the vicinity of the second impurity diffusion region 30 is desirably a wide region 31. Further, the length of the wide region 31 is desirably 50 μm or more. When the contact layer 19 in the vicinity of the second impurity diffusion region 30 is the narrow region 32, or when the wide region 31 is short, the central portion of the NFP becomes strong or the wavefront is curved, resulting in astigmatism. Because it will become larger.

  The second impurity diffusion region 30 does not have the contact layer 19. The second impurity diffusion region 30 may be covered with the buried layer 21 or may be covered with another dielectric film. Alternatively, it may be directly covered by the upper electrode 22 described later.

  In addition, the broad area type semiconductor laser device 1 has an upper electrode 22 on the surface including the upper surface and both side surfaces of the central region of the ridge portion 20, and a lower electrode 23 on the back surface of the substrate 10. Yes. The upper electrode 22 is formed by, for example, laminating titanium (Ti), platinum (Pt), and gold (Au) in this order from the ridge portion 20 side, and is electrically connected to the contact layer 19 of the ridge portion 20. . The lower electrode 23 has a structure in which, for example, an alloy of gold (Au) and germanium (Ge), nickel (Ni), and gold (Au) are stacked in this order from the substrate 10 side. It is connected to the.

  The semiconductor laser 1 having such a configuration can be manufactured, for example, as follows.

  In order to manufacture the semiconductor laser 1 using the compound semiconductor exemplified in the above configuration, the semiconductor stacked structure 10A on the substrate 10 is formed by, for example, the MOCVD (Metal Organic Chemical Vapor Deposition) method. . At this time, for example, trimethylaluminum (TMAl), trimethylgallium (TMGa), trimethylindium (TMIn), phosphine (PH3), and arsine (AsH3) are used as the compound semiconductor material. Monosilane (SiH4) is used, and biscyclopentadienyl magnesium (Cp2Mg) or dimethyl zinc (DMZn) is used as the acceptor impurity material.

  First, as shown in FIG. 6, a buffer layer 11, a lower cladding layer 12, a lower guide layer 13, an active layer 14, an upper guide layer 15, an upper cladding layer 16A, a stop layer 17, and an upper cladding layer are formed on a substrate 10. 16B, the intermediate layer 18 and the contact layer 19 are laminated in this order.

  Next, as shown in FIG. 7, a mask layer (not shown) made of, for example, a resist is formed on the contact layer 19, and a region 20A (FIG. 7) where the ridge portion 20 is to be formed using, for example, a phosphoric acid-based etchant. The contact layer 19 is selectively removed except for the position indicated by the dotted line in FIG. At that time, in the planned formation region 20A of the ridge portion 20, a notch 19A is provided to form the modulation structure 2 composed of the wide region 31 and the narrow region 32, and the portion which becomes the front end surface S1 and the rear end surface S2 by cleavage later A groove 40 is provided in the vicinity of. Further, in the cut 19A, an island portion 19B is formed leaving the contact layer 19, and a groove 41 is provided around the island portion 19B. In the portion where the contact layer 19 is removed, the intermediate layer 18 is exposed. In FIG. 7, the exposed intermediate layer 18 is shown with shading. Thereafter, the mask layer is removed.

  Subsequently, as shown in FIG. 8, a hard mask layer 50 made of SiO2 is formed on the entire surface, and a portion that becomes the front end face S1 and the rear end face S2 is formed on the hard mask layer 50 using a hydrofluoric acid-based etchant. An opening 51 is provided between the groove 40 and an opening 52 smaller than the island portion 19B is provided corresponding to the island portion 19B.

  After that, a ZnO film (not shown) is formed on the entire surface with a thickness of about 100 nm to 500 nm, for example. Thereby, the ZnO film and the contact layer 19 are in contact with each other through the opening 51, and the ZnO film and the island-shaped portion 19 </ b> B are in contact with each other through the opening 52.

  At this time, the edge of the opening 51 is formed to be 50 μm or less on the front end surface S1 side or the rear end surface S2 side from the boundary line 40A between the contact layer 19 and the groove 40 in contact with the front end surface S1 or the rear end surface S2. Preferably, it is more preferably formed to 10 μm or less. In addition, the edge of the opening 52 is preferably formed to be 50 μm or less from the edge of the island-shaped portion 19A, and more preferably 10 μm or less. This is because, in the Zn solid-phase diffusion by the subsequent annealing step, the contact layer 19 or the island-like portion 19B has a Zn diffusion buffering effect, thereby enabling in-plane uniform diffusion. Moreover, since Zn is diffused immediately below the contact layer 19 or the island-like portion 19B, the Zn diffusion shape can be made steep. In particular, when the Zn diffusion shape becomes gentle in the narrow region 32, Zn diffuses to the central portion of the ridge portion 20, and the gain at the central portion of the ridge portion 20 may be reduced. On the other hand, when the thickness is 50 μm or more, the lateral diffusion of Zn cannot be sufficiently performed in the contact layer 19 or the island-shaped portion 19B, and in-plane non-uniform diffusion depending on the shape of the openings 51 and 52 and the grain shape of ZnO occurs. When such non-uniform diffusion is performed, non-uniformity and instability of the transverse mode is induced. In particular, in a broad area type semiconductor laser, the top hat shape of the NFP is easily disturbed due to non-uniform diffusion, and the COD value is lowered. Moreover, since the Zn diffusion shape becomes gentle, the gain decreases.

  After forming the ZnO film, a cap layer (not shown) made of, for example, SiO2 is formed over the entire surface including the ZnO film. This cap layer has a role of preventing Zn atoms from being desorbed into the gas phase in a later annealing step.

  After the cap layer is formed, annealing is performed in a N 2 atmosphere at a temperature of about 500 ° C. to 600 ° C. for about 10 minutes to 2 hours, for example. As a result, Zn atoms contained in the ZnO film diffuse to the active layer 14 and further to the lower cladding layer 12 via the contact layer 19 or the island-shaped portion 19B. The active layer 14 is disordered by mutual substitution of group III atoms via substitution of Zn atoms with Zn atoms, and the band gap of the active layer 14 in which Zn atoms are diffused is Zn in the active layer 14. It becomes larger than the band gap of the region where the atoms are not diffused (gain region). Thereby, the first impurity diffusion region 33 and the second impurity diffusion region 30 are formed.

  Here, the Zn diffusion rate in the AlGaInP layer doped with Mg is compared with the Zn diffusion rate in the GaAs layer doped with Zn at a high concentration (for example, about 1 × 10 18 atoms / cm 3 to 3 × 10 19 atoms / cm 3). And the former is smaller than the latter. Therefore, in the present embodiment, the upper cladding layer 16A, the stop layer 17, the upper cladding layer 16B, and the intermediate layer 18 are formed of a P-based compound semiconductor such as AlInP, GaInP, and AlGaInP, and for these layers, When the contact layer 19 is formed of GaAs and the contact layer 19 is doped with high-concentration Zn as the p-type impurity, the upper cladding layer 16A, the stop layer 17 that the Zn diffusion rate in the upper cladding layer 16B and the intermediate layer 18 is smaller than the Zn diffusion rate in the contact layer 19. Therefore, as described above, when Zn atoms contained in the ZnO film are diffused into the semiconductor stacked structure 10A using the solid phase diffusion method, the Zn atoms contained in the ZnO film are intermediate layers immediately below the contact layer 19. Therefore, the contact layer 19 is laterally diffused. As a result, since the contact layer 19 functions as a buffer for diffusing Zn atoms, even if the ZnO film has a grain shape, the portion that becomes the front end surface S1 and the rear end surface S2, the groove 40, Zn atoms can be uniformly diffused immediately below the contact layer 19 sandwiched between them or directly below the island-shaped portion 19B.

  After annealing, the cap layer is removed with, for example, a hydrofluoric acid-based etchant. Subsequently, the ZnO film is removed with, for example, a hydrochloric acid-based etchant, and then the hard mask layer 50 is removed with, for example, a hydrofluoric acid-based etchant. To do.

  After removing the cap layer, the ZnO film, and the hard mask layer 50, as shown in FIG. 9, using a phosphoric acid-based etchant, for example, between the portion that becomes the front end surface S1 and the rear end surface S2 and the groove 40 The sandwiched contact layer 19 and island-shaped portion 19B are removed, and the intermediate layer 18 is also exposed to these portions. The contact layer 19 and the island-like portion 19B removed at this time may contain a large amount of interstitial Zn by Zn solid phase diffusion. Therefore, if not removed, defects are induced when the laser is driven. It is because it becomes a factor which reduces lifetime. In addition, in re-annealing to be described later, there is a possibility that the element characteristics may be deteriorated by diffusing to the surroundings.

  Thereafter, if necessary, reannealing may be performed at a temperature of about 500 ° C. to 750 ° C. for about 10 minutes to 2 hours in an atmosphere of N2, AsH 3 or PH 3, for example. Thereby, Zn atoms diffused in the semiconductor multilayer structure 10A are surely stored in the group III site, and the crystallinity of the semiconductor multilayer structure 10A is improved. Whether or not crystallinity has improved can be confirmed by measuring PL (photoluminescence) and observing whether or not light emission from a deep level broadly spread in the long wavelength region is suppressed. is there.

  After re-annealing, a mask layer (not shown) is formed on the surface including the contact layer 19, and the intermediate layer 18 and the upper cladding layer 16B are selectively removed using, for example, a hydrochloric acid-based etchant. At this time, since the stop layer 17 functions as an etching stop layer, the etching stops when the stop layer 17 is exposed. As a result, as shown in FIG. 10, a striped ridge portion 20 is formed. Thereafter, the mask layer is removed.

  Thereafter, after forming the buried layer 21, the upper electrode 22, and the lower electrode 23, the front end face S1 and the rear end face S2 are formed by cleavage. In this way, the semiconductor laser 1 of the present embodiment is manufactured.

  The first impurity diffusion region 33 can also be formed after the ridge portion 20 is formed.

  Next, the operation and effect of the broad area type semiconductor laser device 1 of the present embodiment will be described.

  In this broad area type semiconductor laser device 1, when a predetermined voltage is applied between the upper electrode 22 and the lower electrode 23, the current is confined by the modulation structure 2 of the ridge portion 20 and the contact layer 19, and the active layer 14 A current is injected into the current injection region (light emitting region 14A), and light emission is caused by recombination of electrons and holes. This light is reflected by the pair of front end face S1 and rear end face S2, causes laser oscillation at a predetermined wavelength, and is emitted to the outside as a laser beam.

  Incidentally, in the present embodiment, the second impurity diffusion region 30 is provided on at least one of the pair of front end surface S1 and rear end surface S2 and in the vicinity thereof. As a result, the rate at which the laser light generated in the central region (gain region) of the active layer 14 is absorbed and converted into heat at the front end surface S1 and the rear end surface S2 and in the vicinity thereof is reduced. Therefore, the COD value can be improved as compared with the case where the second impurity diffusion region 30 is not provided.

  Further, the contact layer 19 has a modulation structure 2 of a wide region 31 having the same width as the ridge portion 20 and a narrow region 32 having a width narrower than that of the ridge portion 20 by providing the cut 19A. Therefore, no current is injected into the narrow region 32, and the gain in the vicinity of the side surface of the ridge portion 20 is reduced. Therefore, the gain distribution in the ridge portion 20 integrated in the resonator direction decreases in the vicinity of the side surface of the ridge portion 20 as shown in FIG.

  Furthermore, since the first impurity diffusion region 33 is formed in the cut 19A of the narrow region 32 in a part other than the contact layer 19 of the semiconductor stacked structure 10A (for example, the intermediate layer 18 to the lower guide layer 13). In the first impurity diffusion region 33, the band gap of the active layer 14 is expanded by impurity diffusion, and the absorption loss at the laser wavelength is reduced. Therefore, the rate at which the laser light generated in the central region (gain region) of the active layer 14 is absorbed in the narrow region 32 and converted to heat is reduced. Therefore, heat generation due to light absorption is suppressed, and deterioration from the side surface of the ridge portion 20 is suppressed during high output operation.

  In addition, since it has a real index guide structure in which the buried layer 21 made of a dielectric is formed on the side surface of the ridge portion 20, the absorption loss is low. Therefore, the absorption loss near the side surface of the ridge portion 20 averaged in the direction of the resonator is further reduced, thereby suppressing the side peak near the side surface of the ridge portion 20 of the NFP.

  On the other hand, when the first impurity diffusion region 33 is not formed, the band gap of the active layer 14 in the narrow region 32 is not enlarged, and therefore, the saturable absorption characteristic is shown with respect to the laser wavelength. Since the band gap of the active layer 14 contracts due to heat generation on the side surface of the ridge portion 20, the absorption coefficient increases nonlinearly with respect to the laser wavelength. In other words, it is more likely to deteriorate than when the first impurity diffusion region 33 is formed.

  On the other hand, in the real index guide structure in which the width of the contact layer is uniform and the side surface of the ridge portion is embedded with a dielectric, as in the conventional structure described above (hereinafter referred to as the conventional structure A), it is caused by the injection current. Due to the plasma effect at the central portion of the ridge, the refractive index of the central portion is lowered, and a side peak appears remarkably in NFP. When such a side peak is present in NFP, the coupling coefficient with an optical device or an optical component is reduced, and the photon density at the peak position is increased, so that damage is likely to occur on the end face or the ridge side face.

  Further, in the case of a loss guide structure in which the width of the contact layer is made uniform and the side surface of the ridge portion is buried with metal as in other conventional structures (hereinafter referred to as conventional structure B), as shown in FIG. The side peak was suppressed by light absorption on the side surface of the ridge portion. However, during high output operation, heat generation increases due to light absorption on the side surface of the ridge portion, and COD is generated on the side surface of the ridge portion, similarly to the end surface.

  In order to clarify this, the present inventor rapidly deteriorated a broad area type semiconductor laser element (ridge width 60 μm, resonator length 700 μm) having the conventional structure B and not having the second impurity diffusion region. After that, the active layer directly under the ridge was examined by CL measurement. FIG. 13 shows the result, which is a copy of the CL image of the entire active layer immediately below the ridge. As can be seen from FIG. 13, a black line extends from the rear end surface S2. This black line represents a defect called DLD. That is, it can be seen that when the second impurity diffusion region is not provided, rapid deterioration occurs due to the COD of the end face.

  The present inventor also relates to a broad area type semiconductor laser element (ridge width 60 μm, resonator length 700 μm) having the conventional structure B and provided with the second impurity diffusion regions on the front end face and the rear end face. A similar investigation was conducted. FIG. 14 shows the result and is a copy of the obtained CL image. As can be seen from FIG. 14, DLD was not observed from the front end face and the rear end face, but DLD starting from the side face of the ridge portion was observed. The COD light output was 1.5 to several times that of the case where the second impurity diffusion region was not provided.

  On the other hand, in the broad area type semiconductor laser device 1 of the present embodiment, COD does not occur with an equivalent light output. As described above, by suppressing the side peak of NFP while suppressing the absorption loss on the side surface of the ridge portion 20, it is possible to suppress the deterioration from the side surface of the ridge portion 20.

  As described above, in the present embodiment, the narrow region 32 is provided in the contact layer 19, and the first impurity diffusion region 33 is formed in the notch 19 </ b> A of the narrow region 32 in a part other than the contact layer 19 in the semiconductor stacked structure 10 </ b> A. Since it is provided, it is possible to eliminate current injection into the narrow region 32 and reduce the gain, suppress heat generation due to light absorption, and suppress deterioration from the side surface of the ridge portion 20 during high output operation. Therefore, if a broad area type semiconductor laser array is constructed using this broad area type semiconductor element 1, it becomes possible to obtain a high output with a small number of elements, such as a laser display or a laser processing apparatus that requires a high output. Very suitable for application.

(Broad area type semiconductor laser array)
Next, a broad area type semiconductor laser array including a plurality of broad area type semiconductor laser elements 1 will be described with reference to FIGS. This broad area type semiconductor laser array 3 is used for laser display, laser processing or medical application. For example, as shown in FIG. 15, a plurality of ridge portions 20 are formed monolithically on a common substrate 10. By doing so, a watt-class light output can be obtained.

  For example, as shown in FIG. 16, the broad area type semiconductor laser array 3 is joined to a submount 70 having high thermal conductivity such as SiC via a junction (down) via solder (not shown). Are joined to a metal heat sink 80 via solder (not shown). An electrode member 81 that is electrically connected to the lower electrode 23 via a wire 85 is provided on the side opposite to the light emission side of the semiconductor laser array 3. The electrode member 81 is fixed by screws 82 on an insulating plate 83 that is insulated from the heat sink 80. A protection member 84 that protects the wire 85 from the outside is fixed on the electrode member 81 by screws 82.

  In such a broad area type semiconductor laser array 3, thermal interaction is likely to occur between adjacent emitters (corresponding to one broad area type semiconductor laser element 1), so that the emitter interval is preferably set to about 400 μm. Accordingly, when the light output from one emitter increases, the number of emitters can be reduced, and the optical elements that are optically coupled to the broad area type semiconductor laser array 3 can be reduced in size and quantity.

  Furthermore, the broad area type semiconductor laser array 3 shown in FIG. 16 is incorporated in a module (not shown) in a nitrogen atmosphere as necessary, and is applied as a light source of a laser display or a laser irradiation apparatus. For example, in a laser display, laser light emitted from a module is collimated by a lens or the like, spatially modulated by an optical element corresponding to two-dimensional image information, and irradiated on a screen. As these optical elements, for example, liquid crystal, optical MEMS (Micro Electro Mechanical Systems) such as DLP (Digital Light Processing) and GLV (Grating Light Valve) are used.

(Laser display)
FIG. 17 shows an application example in which the broad area type semiconductor laser array 3 of the present embodiment is applied to a laser display. The laser display device 200 includes light sources 201a, 201b, and 201c that emit red (R), green (G), and blue (B) light, and the above-described implementation as the light source 201a that emits red light. A broad area type semiconductor laser array 3 of the form is arranged. The laser display device 200 further includes beam shaping optical systems 202a, 202b, 202c and liquid crystal panels 203a, 203b, 203c, a dichroic prism 204, a projection 205, and a projection provided corresponding to the light sources 201a, 201b, 201c. A screen 206 is provided.

  In this laser display device 200, the light emitted from the RGB light sources 201a, 201b, and 201c passes through the beam shaping optical systems 202a, 202b, and 202c, respectively, and then enters the liquid crystal panels 203a, 203b, and 203c. It is spatially modulated into image information. After that, it is multiplexed by the dichroic prism 204 and projected onto the projection screen 206 via the projection 205.

(Laser irradiation device)
FIG. 18 shows an application example in which the broad area type semiconductor laser array 3 of the present embodiment is applied to a light source of a laser processing apparatus as an example of a laser irradiation apparatus. In the laser irradiation apparatus 300, the laser light 304 emitted from the light source 301 is coupled to the surface of the processing object 303 via the optical system 302 and processed. Since the NFP of the broad area semiconductor laser having a wide ridge portion 20 is rectangular, the beam pattern coupled to the surface of the workpiece 303 is also rectangular. Therefore, in the case of processing of a rectangle or a line shape, the beam utilization efficiency is increased. The laser irradiation apparatus 300 can be applied not only to laser processing but also to surface modification and inspection.

  While the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and various modifications can be made. For example, the material and thickness of each layer, the film formation method, and the film formation conditions described in the above embodiment are not limited, and other materials and thicknesses may be used. It is good also as conditions.

  In the above-described embodiment, the configurations of the broad area type semiconductor laser device 1 and the broad area type semiconductor laser array 3 are specifically described. However, it is not necessary to provide all the layers, and other layers may be provided. Furthermore, you may provide.

  In the above-described embodiments, the present invention has been described by taking an AlGaInP-based compound semiconductor laser as an example. However, other compound semiconductor lasers, for example, a red semiconductor laser such as a GaInAsP-based semiconductor, a nitride such as a GaInN-based and AlGaInN-based semiconductor The present invention is also applicable to II-VI group semiconductor lasers such as gallium semiconductor lasers and ZnCdMgSSeTe. The present invention is also applicable to semiconductor lasers whose oscillation wavelength is not always in the visible range, such as AlGaAs, InGaAs, InP, and GaInAsNP.

  In the above-described embodiments, the present invention has been described by taking the semiconductor laser having an index guide structure as an example. However, the present invention is not limited to this, and other structures, for example, gain guide structures. The present invention can also be applied to a semiconductor laser.

1 is a perspective view illustrating an overall configuration of a broad area type semiconductor laser device according to an embodiment of the present invention. FIG. 2 is a side view of the broad area type semiconductor laser device shown in FIG. 1 as viewed from the front end face or the rear end face. It is sectional drawing of the III-III arrow direction of the broad area type | mold semiconductor laser element shown in FIG. FIG. 2 is a plan view illustrating a planar positional relationship between a contact layer and a ridge portion illustrated in FIG. 1. It is sectional drawing along the VV line of FIG. FIG. 3 is a cross-sectional view for explaining a method of manufacturing the broad area type semiconductor laser device shown in FIG. FIG. 7 is a top view for explaining a step following FIG. 6. FIG. 8 is a top view for explaining a step following the step in FIG. 7. FIG. 9 is a top view for explaining a step following the step in FIG. 8. FIG. 10 is a top view for explaining a step following the step in FIG. 9. It is a figure showing gain distribution in case a contact layer has a narrow structure. It is a figure showing the gain distribution of the conventional loss guide structure. It is a figure showing an experimental result. It is a figure showing another experimental result. It is a perspective view showing the whole structure of a broad area type semiconductor laser array. FIG. 16 is a perspective view illustrating a mounting example of the broad area type semiconductor laser array illustrated in FIG. 15. It is a figure showing the structure of the laser display apparatus which is an example of application of this invention. It is a figure showing the structure of the laser irradiation apparatus which is an example of application of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Broad area type semiconductor laser element, 2 ... Modulation structure, 3 ... Broad area type semiconductor laser array, 10 ... Substrate, 11 ... Buffer layer, 12 ... Lower clad layer, 13 ... Lower guide layer, 14 ... Active layer, 14A Light emitting region, 15 Upper guide layer, 16A and 16B Upper cladding layer, 17 Stop layer, 18 Intermediate layer, 19 Contact layer, 19A Notch, 19B Island-like portion, 20 Ridge portion, 21 Embedded layer, 22 ... upper electrode, 23 ... lower electrode, 30 ... second impurity diffusion region, 31 ... wide region, 32 ... narrow region, 33 ... first impurity diffusion region, 70 ... submount, 80 ... heat sink, 81 ... Electrode member, 82 ... Screw, 83 ... Insulating plate, 84 ... Protection member, 85 ... Wire, S1 ... Front end face, S2 ... Rear end face

Claims (7)

A plurality of layers including an active layer are formed on a substrate, and a band-shaped current confinement structure for confining a current injected into the active layer is formed in a part including the uppermost contact layer among the plurality of layers. A laminated semiconductor structure,
A pair of end faces facing the extending direction of the current confinement structure with the active layer and the current confinement structure in between,
The contact layer has a wide region having the same width as the current confinement structure, and a narrow region having a width narrower than the current confinement structure by being provided with a cut,
Part of the semiconductor laminated structure other than the contact layer is
A first impurity diffusion region formed in the narrow region cut and having a band gap larger than the energy corresponding to the emission wavelength of the active layer;
And a second impurity diffusion region formed in at least one of the pair of end faces and in the vicinity thereof and having a band gap larger than energy corresponding to the emission wavelength of the active layer. The broad area type semiconductor laser device according to claim 1, further comprising a buried layer made of a dielectric film on a side surface of the current confinement structure. 3. The broad area type semiconductor laser device according to claim 1, wherein the narrow region and the first impurity diffusion region are formed at a plurality of locations in an extending direction of the current confinement structure. The broad area type semiconductor laser device according to claim 3, wherein a difference between a width in the wide region of the contact layer and a width in the narrow region is 4 μm or more. A broad area semiconductor laser array having a plurality of broad area semiconductor laser elements,
Each of the plurality of broad area semiconductor laser elements is
A plurality of layers including an active layer are formed on a substrate, and a band-shaped current confinement structure for confining a current injected into the active layer is formed in a part including the uppermost contact layer among the plurality of layers. A laminated semiconductor structure,
A pair of end faces facing the extending direction of the current confinement structure with the active layer and the current confinement structure in between,
The contact layer has a wide region having the same width as the current confinement structure, and a narrow region having a width narrower than the current confinement structure by being provided with a cut,
Part of the semiconductor laminated structure other than the contact layer is
A first impurity diffusion region formed in the narrow region cut and having a band gap larger than the energy corresponding to the emission wavelength of the active layer;
A broad area type semiconductor laser array comprising: a second impurity diffusion region formed in at least one of the pair of end faces and in the vicinity thereof and having a band gap larger than energy corresponding to the emission wavelength of the active layer. A laser display comprising a broad area type semiconductor laser array having a plurality of broad area type semiconductor laser elements,
Each of the plurality of broad area semiconductor laser elements is
A plurality of layers including an active layer are formed on a substrate, and a band-shaped current confinement structure for confining a current injected into the active layer is formed in a part including the uppermost contact layer among the plurality of layers. A laminated semiconductor structure,
A pair of end faces facing the extending direction of the current confinement structure with the active layer and the current confinement structure in between,
The contact layer has a wide region having the same width as the current confinement structure, and a narrow region having a width narrower than the current confinement structure by being provided with a cut,
Part of the semiconductor laminated structure other than the contact layer is
A first impurity diffusion region formed in the narrow region cut and having a band gap larger than the energy corresponding to the emission wavelength of the active layer;
And a second impurity diffusion region formed in at least one of the pair of end faces and in the vicinity thereof and having a band gap larger than energy corresponding to the emission wavelength of the active layer. A laser irradiation apparatus comprising a broad area type semiconductor laser array having a plurality of broad area type semiconductor laser elements,
Each of the plurality of broad area semiconductor laser elements is
A plurality of layers including an active layer are formed on a substrate, and a band-shaped current confinement structure for confining a current injected into the active layer is formed in a part including the uppermost contact layer among the plurality of layers. A laminated semiconductor structure,
A pair of end faces facing the extending direction of the current confinement structure with the active layer and the current confinement structure in between,
The contact layer has a wide region having the same width as the current confinement structure, and a narrow region having a width narrower than the current confinement structure by being provided with a cut,
Part of the semiconductor laminated structure other than the contact layer is
A first impurity diffusion region formed in the narrow region cut and having a band gap larger than the energy corresponding to the emission wavelength of the active layer;
And a second impurity diffusion region formed in at least one of the pair of end faces and in the vicinity thereof and having a band gap larger than the energy corresponding to the emission wavelength of the active layer.

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