JP4066317B2 - Semiconductor laser device, manufacturing method thereof, and optical disc apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is a semiconductor laser element expected to be applied to the field of optical information processing., Its manufacturing method and Optical disk deviceAbout.
[0002]
[Prior art]
  In general, an end face reflecting film is provided on a resonator end face of laser light in a semiconductor laser element. In particular, the reflection end face, which is the rear end face facing the laser light emission face, is required to have a high reflectance, so that the film thickness is λ / 4n.₁ Low refractive index film and film thickness is λ / 4n₂ A high-reflectivity end-face reflection film is formed by alternately laminating these high-refractive-index films. Here, λ represents the oscillation wavelength of the laser beam, and n₁ Represents the refractive index at the wavelength λ of the low refractive index film, and n₂ Represents the refractive index of the high refractive index film at the wavelength λ.
[0003]
  The low-refractive index film and the high-refractive index film constituting the end face reflection film are required to have a sufficiently small absorption coefficient at the wavelength of the laser beam. Therefore, silicon oxide (SiO 2) having a low absorption coefficient in a wide band including the visible light region and the ultraviolet region is included in the low refractive index film constituting the end face reflection film.₂ ) Or aluminum oxide (Al₂ O_Three ) Is used. On the other hand, various dielectric materials are used for the high refractive index film constituting the end face reflection film depending on the wavelength of the laser beam.
[0004]
  For example, an infrared or red semiconductor laser element made of aluminum gallium arsenide (AlGaAs) that outputs laser light having a wavelength of about 780 nm uses amorphous silicon (α-Si) as its high refractive index film. Here, the value of the absorption coefficient for light having a wavelength of 780 nm of amorphous silicon is 4 × 10.^Four cm^-1It is.
[0005]
  As an application example of this infrared or red semiconductor laser element in the field of optical disc devices, there is a quadruple speed CD-R (CD-recordable) laser element that can be written only once at a speed four times the standard. Can be mentioned. In the quadruple speed CD-R laser element, a laminated film in which silicon oxide and amorphous silicon form a pair is used as an end face reflection film on the rear end face. For example, the reflectance can be set to 95% by forming the end face reflection film from two sets (periods) of silicon oxide and amorphous silicon.
[0006]
  Using this end face reflection film, a quadruple-speed CD-R laser element having a light output of 100 mW when the duty ratio is 50% driven and 80 mW when continuously driven (CW) is realized. ing.
[0007]
  On the other hand, a high refractive index film of a red semiconductor laser element made of aluminum gallium indium phosphide (AlGaInP) that outputs laser light having a wavelength of about 650 nm is replaced with titanium oxide (TiO 2) instead of amorphous silicon.₂ ) Is used. The reason why amorphous silicon is not used is that the absorption coefficient of amorphous silicon with respect to light having a wavelength near 650 nm is large. Therefore, when this is used for an end face reflection film, light absorption in the amorphous silicon layer increases. This is because the crystallinity in the vicinity of the cavity end face of the laser element deteriorates due to the temperature rise accompanying this light absorption, and the reliability of the element decreases.
[0008]
  Therefore, a red semiconductor laser element having a wavelength of about 650 nm uses titanium oxide as an end face reflecting film, which has a sufficiently large refractive index and a smaller absorption coefficient than amorphous silicon as compared with silicon oxide. The value of the absorption coefficient for light with a wavelength of 650 nm of amorphous silicon is 1 × 10^Five cm^-1On the other hand, the value of the absorption coefficient for light with a wavelength of 650 nm of titanium oxide is 2 cm.^-1It is.
[0009]
  Further, even in a blue-violet semiconductor laser element having an oscillation wavelength of about 400 nm that is currently being developed, a laminated film made of silicon oxide and titanium oxide is used as an end face reflection film. For example, as an end face reflection film of a semiconductor laser element made of aluminum indium gallium nitride (AlInGaN), a semiconductor laser element using a laminated film made of silicon oxide and titanium oxide is disclosed in Jpn. J. Appl. Phys. Vol. 1999) pp. L184-L186. The value of the absorption coefficient for light with a wavelength of 400 nm of titanium oxide is 2400 cm.^-1It is.
[0010]
[Problems to be solved by the invention]
  2. Description of the Related Art In recent years, semiconductor laser elements for optical disk devices are required to have a high output for improving the recording speed on the optical disk and a short wavelength for improving the recording density.
[0011]
  However, it is used for an end face reflection film made of a laminate of silicon oxide and amorphous silicon, which is used in a conventional infrared or red semiconductor laser device having an oscillation wavelength of about 780 nm, and a red semiconductor laser device having an oscillation wavelength of about 650 nm. The end face reflection film made of a laminated body of silicon oxide and titanium oxide has a problem that it cannot cope with an increase in output of the laser element.
[0012]
  Another problem is that the end face reflection film made of a laminated body of silicon oxide and titanium oxide, which is also used for a blue-violet semiconductor laser element having an oscillation wavelength of about 400 nm, cannot cope with the shorter wavelength of the laser element. is there.
[0013]
  This is because the light absorption coefficient of the high refractive index film in the emitted light of each semiconductor laser element cannot be said to be sufficiently small. Therefore, when the output of the laser element is increased, the temperature rises due to the light absorption of the high refractive index film. This is because the crystal structure of the semiconductor laser element, particularly in the vicinity of the cavity end face in the active region, deteriorates.
[0014]
  Similarly, when shortening the oscillation wavelength to 400 nm or less, it is difficult to cope with an end face reflection film made of a conventional laminated film with silicon oxide. This is because the absorption coefficient of titanium oxide greatly increases in the short wavelength region.
[0015]
  An object of the present invention is to solve the above-mentioned conventional problems and to obtain an end face reflection film that can cope with a higher output or shorter wavelength of a semiconductor laser element.
[0016]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides niobium oxide (Nb oxide) on a high refractive index film constituting an end face reflection film of a semiconductor laser element.₂O_Five).
[0017]
  Specifically, the present invention relates toHalfConductor laser elementsandwiched between an n-type semiconductor layer, a p-type semiconductor layer, and an n-type semiconductor layer and a p-type semiconductor layer III- An active layer made of a group V nitride semiconductor, a resonator including an active layer disposed between an n-type semiconductor layer and a p-type semiconductor layer, and a reflective film including niobium oxide disposed on an end face of the resonator. The oscillation wavelength is 0.4 μm or shorter than 0.4 μm..
[0018]
  The present inventionAccording to the semiconductor laser element, since the reflecting film formed on the end face of the resonator contains niobium oxide having a light absorption coefficient smaller than that of titanium oxide, for example, the absorption of laser light is less than that of titanium oxide. An increase in temperature of the reflective film is suppressed. For this reason, since the deterioration of the crystal structure of the semiconductor layer near the end face of the resonator can be prevented, the output of the laser element can be increased or the wavelength can be shortened.
[0019]
  In the semiconductor laser device of the present invention, the active layer preferably contains In.
[0020]
  In the semiconductor laser device of the present invention, the reflective film preferably covers the end face of the resonator.
[0021]
  In the semiconductor laser device of the present invention, it is preferable that the reflective film has a first dielectric layer and a second dielectric layer containing niobium oxide.
[0022]
  In this case, the refractive index of the second dielectric layer is preferably larger than the refractive index of the first dielectric layer.
[0023]
  In this case,The first dielectric layer is silicon oxide or aluminum oxideIt is preferable to contain.
[0024]
  The present inventionHalfThe manufacturing method of the conductor laser element is as follows:Targeting a method for manufacturing a semiconductor laser device having an oscillation wavelength shorter than 0.4 μm or 0.4 μm, an n-type semiconductor layer, a p-type semiconductor layer, an n-type semiconductor layer, and a p-type semiconductor layer are formed on a substrate. Sandwiched III- A step of growing an active layer made of a group V nitride semiconductor, and a step of forming an end face of a resonator by cleaving or etching a substrate on which an n-type semiconductor layer, a p-type semiconductor layer, and an active layer are grown. And a step of forming a reflective film containing niobium oxide on the end face of the resonator.
[0025]
  The present inventionAccording to the semiconductor laser device manufacturing method ofN-type semiconductor layer, p-type semiconductor layer and active layer were grownBy cleaving or etching the substrate,Substrate including each semiconductor layer and active layerTo expose a resonator end face, and to form a reflective film containing niobium oxide on the exposed resonator end face.Half ofA conductor laser element can be realized.
[0026]
  The present inventionIn the method of manufacturing a semiconductor laser device, the step of forming the reflective film includes the first dielectric layer having a refractive index smaller than that of niobium oxide and the second dielectric layer made of niobium oxide. It is preferable to include a step of forming a laminated structure. Thus, the second or third semiconductor laser element of the present invention can be realized.
[0027]
  The present inventionIn the semiconductor laser device manufacturing method, it is preferable to form the reflective film by sputtering or reactive sputtering.
[0028]
  An optical disc apparatus according to the present invention is reflected by a recording medium, a light emitting unit including a semiconductor laser element, a condensing optical unit that condenses laser light emitted from the light emitting unit on a recording medium on which data is recorded, and A light detecting section for detecting light, the semiconductor laser element issandwiched between an n-type semiconductor layer, a p-type semiconductor layer, and an n-type semiconductor layer and a p-type semiconductor layer III- An active layer made of a group V nitride semiconductor; a resonator including an active layer disposed between the n-type semiconductor layer and the p-type semiconductor layer;On the end face of the resonatorPlacedReflective film containing niobium oxideThe oscillation wavelength is 0.4 μm or shorter than 0.4 μm.
[0029]
  According to the optical disk device of the present invention, since the semiconductor laser element that constitutes the light emitting section has the reflective film containing niobium oxide formed on the end face of the resonator, the light emitting section can increase the output of the semiconductor laser element. It becomes possible to cope with shorter wavelengths.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
  (First embodiment)
  A first embodiment of the present invention will be described with reference to the drawings.
[0031]
  FIG. 1 shows a blue-violet semiconductor laser element having an oscillation wavelength of about 400 nm, which is a semiconductor laser element according to the first embodiment of the present invention.
[0032]
  As shown in FIG. 1, the semiconductor laser device 10 includes at least an n-type quantum well active layer 11 including a barrier layer made of gallium nitride (GaN) and a well layer made of indium gallium nitride (InGaN), for example. And a resonator 12 sandwiched from above and below between light guide layers made of p-type aluminum gallium nitride (AlGaN).
[0033]
  An end face reflection film 13 is provided on the reflection end face 10 b opposite to the emission end face 10 a of the laser beam 100 in the resonator 12.
[0034]
  The end face reflection film 13 is formed in order from the end face side of the resonator 12 and is formed of silicon oxide (SiO 2) as a first dielectric layer.₂ ) And a niobium oxide (Nb) as the second dielectric layer.₂O_Five) And a plurality of unit reflection films 130 each including the high refractive index film 13b.
[0035]
  The film thicknesses of the low refractive index film 13a and the high refractive index film 13b, and the number of unit reflection films 130 can be set to appropriate values depending on the specifications of the semiconductor laser element. For example, by forming three sets of unit reflection films 130 made of silicon oxide having a film thickness of about 68 nm and niobium oxide having a film thickness of about 40 nm, a reflectivity of about 93.9% is obtained on the end face reflection film 13. be able to.
[0036]
  Here, as in the conventional case, titanium oxide (TiO 2) is applied to the high-refractive index film 13b that is a reflection film for laser light having an oscillation wavelength of about 400 nm.₂ ), It is possible to obtain a reflectance comparable to that of niobium oxide.
[0037]
  However, in the first embodiment, since niobium oxide is used for the high refractive index film 13b of the end face reflecting film 13, the light absorption coefficient of niobium oxide is smaller than that of titanium oxide. Temperature rise can be suppressed. As a result, the crystallinity of the quantum well active layer 11 and its peripheral part is hardly deteriorated, and the output of the semiconductor laser device can be increased. Although the active layer has a quantum well structure, the quantum well structure is not necessarily employed.
[0038]
  In addition to the increase in output, even when the wavelength is reduced to an ultraviolet region with an oscillation wavelength of 400 nm or less, a unit made of silicon oxide and titanium oxide is formed on the end face reflection film 13 for an ultraviolet semiconductor laser element. When the reflective film 130 is used, the semiconductor laser element is deteriorated due to light absorption of titanium oxide. On the other hand, in the first embodiment, even in the ultraviolet region, since the light absorption coefficient of niobium oxide is smaller than that of titanium oxide, it is possible to reduce the deterioration of the element due to the shorter wavelength.
[0039]
  Niobium oxide also functions as a protective film that prevents water or hydrogen entering from the outside from diffusing into the laser element. Group III-V nitride semiconductors, which are considered promising as semiconductor materials capable of obtaining blue-violet light with an oscillation wavelength of about 400 nm, have the property that their electrical characteristics are particularly susceptible to deterioration by hydrogen. In the semiconductor laser device according to the embodiment, since one of the end faces of the resonator is covered with niobium oxide that prevents hydrogen from entering, deterioration of the semiconductor laser device due to diffusion of impurities such as hydrogen from the outside can be prevented.
[0040]
  Hereinafter, a method for manufacturing the semiconductor laser device configured as described above will be described with reference to the drawings.
[0041]
  FIG. 2 is a method for manufacturing a semiconductor laser device according to the first embodiment of the present invention, and schematically shows a method for manufacturing an end face reflection film by sputtering. Here, for example, a magnetron sputtering apparatus is used as the sputtering film forming apparatus.
[0042]
  First, a schematic configuration of the film forming apparatus will be described.
[0043]
  As shown in FIG. 2, the magnetron sputtering apparatus 20 includes a film formation chamber 23 having a gas inlet 21 provided at the upper part of the wall surface and an exhaust port 22 provided at the lower part of the wall surface facing the gas inlet 21. have.
[0044]
  An anode 24 is installed at the bottom of the film forming chamber 23, and a laser element forming body 10 </ b> A that is a film forming target is held on the anode 24 with the reflection end face 10 b of each resonator 12 facing upward. . Here, the laser element forming body 10A is a strip-shaped semiconductor wafer in which a plurality of resonators 12 are formed in advance, and is cleaved in a direction substantially perpendicular to the resonator length direction to expose the reflection end face 10b. Yes.
[0045]
  In the upper part of the film formation chamber 23, niobium oxide (Nb₂O_FiveIs provided with a flat plate type magnetron electrode 26 held so that a plate-like target material 25 made of As a result, the exposed reflection end face 10 b of the laser element formation body 10 </ b> A faces the target material 25.
[0046]
  Next, a film forming method will be described.
[0047]
  First, a plasma generating gas containing argon (Ar) as a main component is introduced from the gas inlet 21 into the decompressed film forming chamber 23. Subsequently, high frequency power is applied to the target material 25 to generate plasma near the surface of the target material 25. At this time, the surface of the target material 25 is sputtered by argon ions that collide with the target material 25, thereby forming a dielectric film on the reflective end face 10 b of the laser element forming body 10 </ b> A held on the anode 24. The In the first embodiment, as an example, three sets of unit reflection films 130 each including a low refractive index film 13a made of silicon oxide and a high refractive index film 13b made of niobium oxide are formed.
[0048]
  The low refractive index film 13a is made of silicon (Si) as the target material 25, argon (Ar) as the plasma generating gas, and oxygen (O) as the reactive gas.₂ The reactive sputtering method is used.
[0049]
  On the other hand, when the target material 25 made of niobium oxide is sputtered by argon ions, the high refractive index film 13b is likely to have a composition of oxygen in the formed niobium oxide smaller than the stoichiometric ratio. Therefore, in order to prevent oxygen deficiency in niobium oxide, it is desirable to supply oxygen gas together with argon gas as an introduction gas during film formation.
[0050]
  In this embodiment, the supply amount of argon is about 10 sccm (standard cubic centimeter per minute), and the supply amount of oxygen is about 40 sccm. Further, the pressure in the film formation chamber 23 during film formation is set to about 0.1 Pa, and the high frequency power is set to about 1 kW. Under these conditions, the high refractive index film 13b made of niobium oxide having a deposition rate of about 8 nm / min and almost no oxygen deficiency can be formed.
[0051]
  Although niobium oxide is used for the target material 25 for generating the high refractive index film 13b, instead of this, reactive sputtering using metal niobium (Nb) as the target material 25 and oxygen gas as the reactive gas. Alternatively, the film may be formed.
[0052]
  Further, it is desirable that the end face reflection film 13 be formed by a vacuum partial process in order to prevent interface contamination between the low refractive index film 13a made of silicon oxide and the high refractive index film 13b made of niobium oxide. For this purpose, a sputtering apparatus having a multi-chamber configuration including a film formation chamber for silicon oxide and a film formation chamber for niobium oxide, or a single film formation chamber having a silicon oxide material and a niobium oxide material It is desirable to use a sputtering apparatus having a multi-source configuration.
[0053]
  Thus, niobium oxide (Nb₂O_Five) Is a laser that outputs laser light in other wavelength regions such as a red semiconductor laser element as well as a blue-violet semiconductor laser element because a dielectric film having a low light absorption and a high refractive index can be formed relatively easily. It can be easily applied to elements.
[0054]
  FIGS. 3A and 3B are evaluation results by a spectroscopic ellipsometer, in which the light absorption coefficient and refractive index wavelength dispersion of the high refractive index film made of niobium oxide according to the first embodiment are compared. It is shown for comparison with a high refractive index film made of titanium oxide by a reactive sputtering method.
[0055]
  As shown in FIG. 3A, the absorption coefficient of niobium oxide indicated by a solid line increases monotonously as the wavelength becomes shorter, but the value is significantly smaller than that of titanium oxide indicated by a broken line. For example, when comparing the absorption coefficient at a wavelength of 400 nm, titanium oxide is 2400 cm.^-1Whereas niobium oxide is 109cm^-1Is shown.
[0056]
  On the other hand, as shown in FIG. 3B, the refractive index of niobium oxide monotonously increases as the wavelength becomes shorter, but shows a slightly smaller value as compared with titanium oxide. Thus, the refractive index of titanium oxide is larger than that of niobium oxide. For example, when comparing the refractive index at a wavelength of 400 nm, titanium oxide is 2.95, whereas niobium oxide is Indicates 2.52.
[0057]
  In general, degradation of a laser element due to light absorption becomes a problem because the value of the light absorption coefficient is 10.^Three cm^-1-10^Four cm^-1This is the case. Absorption coefficient value is 10^Four cm^-1If the following region is a wavelength region that can be used as the material of the end face reflection film 13, in the case of titanium oxide, it is not possible to cope with a wavelength of about 370 nm or less, whereas in the case of niobium oxide, it is possible to cope up to around 340 nm. I know that there is.
[0058]
  As shown in FIG. 3B, the refractive index of niobium oxide is slightly smaller than the refractive index of titanium oxide, but silicon oxide (SiO 2) constituting the low refractive index film 13a.₂ ) Is sufficiently large compared to the refractive index of), a sufficient reflectance can be obtained for the end face reflecting film 13 by using the unit reflecting film 130 made of silicon oxide and niobium oxide.
[0059]
  FIG. 4 shows the film thickness dependence of the reflectance with respect to light having a wavelength of 400 nm in the end face reflection film of the semiconductor laser device according to the first embodiment. Here, the film thickness is λ / 4n₁ A low refractive index film 13a made of silicon oxide having a thickness of about 68 nm and a film thickness of λ / 4n₂ By stacking three units of the unit reflecting film 130 composed of the high refractive index film 13b made of niobium oxide of about 40 nm determined by the above, an end face reflecting film 13 having a reflectance of about 93.9% is obtained. ing. Where λ is 400 nm and n₁ Is the refractive index of silicon oxide at a wavelength of 400 nm, and n₂ Is the refractive index of niobium oxide at a wavelength of 400 nm.
[0060]
  In the first embodiment, the magnetron sputtering apparatus is used as the niobium oxide film forming method. However, the present invention is not limited to this, and an ECR sputtering apparatus, a high-frequency sputtering apparatus, a helicon sputtering apparatus, or the like may be used.
[0061]
  Further, the unit reflection film 130 composed of the low refractive index film 13a and the high refractive index film 13b is provided with a refractive index between the semiconductor layer in contact with the low refractive index film 13a when the low refractive index film 13a is provided on the end face side. A difference occurs in the reflection rate and the reflectance increases. However, although the reflectivity is lowered, a configuration in which the high refractive index film 13b is provided on the end surface side, or a configuration in which the outer film of the unit reflection film 130 is terminated with only one of the pair of films, that is, the end surface side and the outer side. Even if the low refractive index film 13a or the high refractive index film 13b is provided on both sides, the effect of the present invention is not impaired.
[0062]
  In addition, although silicon oxide is used for the low refractive index film 13a, aluminum oxide (Al₂O_Three) May be used.
[0063]
  Moreover, you may provide the silicon oxide or aluminum oxide which is a low refractive index also in the output end surface 10a on the opposite side to the reflective end surface 10b in the resonator 12 as a protective film.
[0064]
  In addition, although a group III-V nitride semiconductor mainly composed of gallium nitride is used as a semiconductor material of a blue-violet semiconductor laser device having an oscillation wavelength of about 400 nm, the present invention is not limited to this, but zinc selenide (ZnSe), sulfide A II-VI group compound semiconductor such as zinc (ZnS) or zinc oxide (ZnO) may be used.
[0065]
  (Reference example)
  Hereinafter, the present inventionReference exampleWill be described.
[0066]
  In the first embodiment described above, niobium oxide is used for the high reflectivity film that can cope with shorter wavelengths.Reference exampleIn this case, it is possible to cope with the increase in output of a semiconductor laser element having a long wavelength whose oscillation wavelength is infrared to red.
[0067]
  For example, in a 16 × speed CD-R laser element capable of writing once at a speed 16 times the standard, an optical output of 150 mW when pulse driving with a duty ratio of 50% and 110 mW when driving CW Therefore, a conventional end face reflection film composed of a low refractive index film made of silicon oxide and a high refractive index film made of amorphous silicon cannot provide sufficient reliability.
[0068]
  Therefore,Reference exampleIn the present invention, the first dielectric layer and the second dielectric layer used for the end face reflection film are each made of silicon oxide (SiO 2).₂ ) And niobium oxide (Nb)₂O_FiveThe long-term reliability of an infrared or red semiconductor laser device for 16 × CD-R can be obtained.
[0069]
  FIG. 5 illustrates the present invention.Reference example1 shows an infrared or red semiconductor laser device having an oscillation wavelength of about 780 nm.
[0070]
  As shown in FIG. 5, the semiconductor laser element 30 includes at least a quantum well active layer 31 composed of, for example, a barrier layer made of aluminum gallium arsenide (AlGaAs) and a well layer made of gallium arsenide (GaAs). A resonator 32 is formed which is sandwiched from above and below between light guide layers made of n-type and p-type aluminum gallium arsenide (AlGaAs). In addition,Reference exampleIn FIG. 1, the active layer has a quantum well structure, but the quantum well structure is not necessarily employed.
[0071]
  An end face reflection film 33 is provided on the reflection end face 30 b opposite to the emission end face 30 a of the laser beam 100 in the resonator 32.
[0072]
  The end face reflection film 33 is formed of a low refractive index film 33a made of silicon oxide as a first dielectric layer and a high layer made of niobium oxide as a second dielectric layer, which are sequentially formed from the end face side of the resonator 32. A plurality of unit reflection films 330 including the refractive index film 33b are included.
[0073]
  The film thicknesses of the low refractive index film 33a and the high refractive index film 33b and the number of unit reflection films 330 can be set to appropriate values depending on the specifications of the semiconductor laser element. For example, the film thickness is λ / 4n on the reflection end face 30b.₁ And the film thickness is λ / 4n₂ By forming two pairs of niobium oxide determined by the above, a reflectance of about 85% can be obtained in the end face reflecting film 33.
[0074]
  Reference exampleAccording to the above, since niobium oxide is used for the high refractive index film 33b of the end face reflection film 33 formed on the reflection end face 30b of the resonator 32, the light absorption coefficient of the niobium oxide is smaller than that of amorphous silicon. Temperature rise near the end face of the vessel 33 is suppressed. As a result, the crystallinity of the quantum well active layer 31 and its peripheral part is hardly deteriorated, and the output of the semiconductor laser device can be increased.
[0075]
  This is because the light absorption coefficient value of amorphous silicon with respect to light having a wavelength of 780 nm is 4 × 10.^Four cm^-1On the other hand, the value of the light absorption coefficient of niobium oxide is 10^-3cm^-1This is because the light absorption in the end face reflection film 33 can be greatly reduced because it is substantially zero as follows.
[0076]
  In addition,Reference exampleAs a modified example, hydrogenated amorphous silicon (α-Si: H), which is amorphous silicon containing hydrogen, may be used instead of niobium oxide in the second set of high refractive index films 33b in the end face reflecting film 33. . In this way, the reflectance of the end face reflection film 33 can be set to about 90%.
[0077]
  From the above, in order to increase the output of the infrared or red semiconductor laser device, niobium oxide may be used for all the high refractive index films 33b of the two sets of unit reflection films 330, and further three sets. What is necessary is just to provide the end surface reflecting film 33 which consists of the above unit reflecting films 330.
[0078]
  Further, when such a high output is not required, for example, in the case of a laser device for quadruple speed CD-R, the reflection end faces 30b of the plurality of unit reflection films 330 are obtained so that a high reflectance can be obtained with a predetermined injection current amount. A dielectric having a refractive index higher than that of niobium oxide may be used for the outer high refractive index film 33b excluding the first set on the side.
[0079]
  (SecondEmbodiment)
  Hereinafter, the present inventionSecondEmbodiments will be described with reference to the drawings.
[0080]
  FIG. 6 shows the present invention.Second1 schematically illustrates a configuration of an optical disc device according to an embodiment. In FIG.SecondThe optical disk apparatus according to the embodiment uses the semiconductor laser element of the present invention, that is, the blue-violet semiconductor laser element according to the first embodiment, for the light emitting unit 41 of the optical disk apparatus.
[0081]
  As shown in FIG. 6, in the optical disc apparatus, the emission end face of the semiconductor laser element constituting the light emitting unit 41 and the data holding surface of the optical disc 50, which is a recording medium on which desired data is recorded, face each other. A condensing optical unit 40 is provided between the light emitting unit 41 and the optical disc 50.
[0082]
  The condensing optical unit 40 includes a collimator lens 42 which is provided in order from the light emitting unit 41 side and makes the emitted light 51 emitted from the light emitting unit 41 parallel light, and three beams (not shown) of the parallel light. A diffraction grating 43 that divides into two, a half prism 44 that transmits the outgoing light 51 and changes the optical path of the reflected light 52 from the optical disk 50, and a condenser lens 45 that condenses the three beams on the optical disk 50. Have. Here, laser light having a wavelength of about 400 nm is used as the emitted light 51.
[0083]
  The three beams collected on the optical disc 50 have a spot shape with a diameter of about 0.4 μm. A drive system circuit 46 is provided for correcting the displacement in the radial direction of the optical disc 50 detected by the positions of the three spots by appropriately moving the condenser lens 45.
[0084]
  On the optical path of the reflected light 52 from the half prism 44, a light receiving lens 47 for focusing the reflected light 52, a cylindrical lens 48 for detecting a focal position shift, and light detection for converting the collected reflected light 52 into an electric signal. A photodiode element 49 as a part is provided.
[0085]
  As described above, the semiconductor laser element constituting the light emitting unit 41 of the optical disc apparatus including the condensing optical unit 40 that guides the emitted light 51 to the optical disc 50 and the photodiode element 49 that receives the reflected light 52 reflected by the optical disc 50. Uses niobium oxide, which has a light absorption coefficient smaller than that of amorphous silicon or titanium oxide, for the high refractive index film of the end face reflecting film which is the end face opposite to the exit end face. For this reason, when the oscillation wavelength is shortened to about 400 nm or 400 nm or less, the long-term reliability of the light emitting unit 41 and, in turn, the long-term reliability of the optical disc apparatus can be obtained.
[0086]
  Also,SecondAs a modification of the embodiment, a semiconductor laser element constituting the light emitting unit 41 is used.Reference example mentioned aboveIf the infrared or red semiconductor laser device according to the above is used, long-term reliability can be obtained as a 16 × CD-ROM drive device.
[0087]
【The invention's effect】
  According to the semiconductor laser device and the method of manufacturing the same according to the present invention, the absorption of laser light in the reflective film is reduced, so that the temperature rise of the reflective film is suppressed. Deterioration of the laser beam can be prevented, and the output of the laser element can be increased or the wavelength can be shortened.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a blue-violet semiconductor laser device according to a first embodiment of the present invention.
FIG. 2 is a schematic view showing a method for manufacturing a reflection end face of the blue-violet semiconductor laser device according to the first embodiment of the present invention.
FIGS. 3A and 3B show the wavelength dependence of the high refractive index film in the end face reflection film of the blue-violet semiconductor laser device according to the first embodiment of the present invention, and FIG. It is a graph which shows a coefficient, (b) is a graph which shows a refractive index.
FIG. 4 is a graph showing the film thickness dependence of the reflectance with respect to light having a wavelength of 400 nm in the end face reflection film of the blue-violet semiconductor laser device according to the first embodiment of the present invention.
FIG. 5 shows the present invention.Reference exampleIt is a perspective view which shows the infrared or red semiconductor laser element which concerns on.
FIG. 6 of the present inventionSecond1 is a schematic configuration diagram showing an optical disc device according to an embodiment.
[Explanation of symbols]
  10 Semiconductor laser device
  10a Output end face
  10b Reflective end face
  10A Laser element forming body
  11 Quantum well active layer
  12 Resonator
  13 End face reflection film
  13a Low refractive index film (first dielectric layer)
  13b High refractive index film (second dielectric layer)
  130 Unit reflection film
  20 Magnetron sputtering equipment
  21 Gas inlet
  22 Exhaust port
  23 Deposition chamber
  24 Anode
  25 Target material
  26 Flat-type magnetron electrode
  30 Semiconductor laser device
  30a Output end face
  30b Reflective end face
  31 Quantum well active layer
  32 Resonator
  33 End face reflection film
  33a Low refractive index film (first dielectric layer)
  33b High refractive index film (second dielectric layer)
  330 unit reflective film
  100 laser light
  40 Condensing optics
  41 Light emitting part
  42 Collimator lens
  43 Diffraction grating
  44 half prism
  45 condenser lens
  46 Drive system circuit
  47 Light receiving lens
  48 Cylindrical lens
  49 Photodiode element (light detector)
  50 optical disc
  51 Light emission
  52 Reflected light

Claims (9)

an n-type semiconductor layer;
a p-type semiconductor layer;
A resonator comprising an n-type semiconductor layer and an active layer sandwiched between the p-type semiconductor layers, and comprising a group III-V nitride semiconductor ;
Before SL is disposed on the end face of the resonator and a reflecting film including a dielectric layer made of niobium oxide,
A semiconductor laser element whose oscillation wavelength is 0.4 μm or shorter than 0.4 μm.   The semiconductor laser device according to claim 1, wherein the active layer contains In.   The semiconductor laser device according to claim 1, wherein the reflective film covers an end face of the resonator.   2. The semiconductor laser device according to claim 1, wherein the reflective film includes a first dielectric layer and a second dielectric layer made of niobium oxide.   The semiconductor laser device according to claim 4, wherein a refractive index of the second dielectric layer is larger than a refractive index of the first dielectric layer.   The semiconductor laser device according to claim 4, wherein the first dielectric layer is made of silicon oxide or aluminum oxide. A method of manufacturing a semiconductor laser device having an oscillation wavelength shorter than 0.4 μm or 0.4 μm,
Growing an n-type semiconductor layer, a p-type semiconductor layer, and an active layer made of a group III-V nitride semiconductor sandwiched between the n-type semiconductor layer and the p-type semiconductor layer on a substrate;
Forming an end face of the resonator by cleaving or etching the substrate on which the n-type semiconductor layer, the p-type semiconductor layer, and the active layer are grown;
Forming a reflective film including a dielectric layer made of niobium oxide on an end face of the resonator.   The method of manufacturing a semiconductor laser device according to claim 7, wherein the reflective film is formed by a sputtering method or a reactive sputtering method. A light emitting unit including a semiconductor laser element;
A condensing optical unit for condensing the laser beam emitted from the light emitting unit on a recording medium on which data is recorded;
A light detection unit for detecting light reflected by the recording medium,
The semiconductor laser device includes an n-type semiconductor layer, a p-type semiconductor layer, an active layer sandwiched between the n-type semiconductor layer and the p-type semiconductor layer, and a resonator made of a III-V nitride semiconductor . If, prior SL is disposed on the end face of the resonator and a reflecting film including a dielectric layer made of niobium oxide, a short optical disk device than the oscillation wavelength is 0.4 .mu.m or 0.4 .mu.m.

Images