JP5100407B2 - Semiconductor light emitting element and semiconductor light emitting device using the same - Google Patents

Description

  The present invention generally relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device improved so as to suppress defects due to an increase in operating voltage. The present invention also relates to a semiconductor light emitting device equipped with such a semiconductor light emitting element.

  The group III nitride semiconductor laser element has a wide oscillation wavelength from ultraviolet to visible light, and has attracted attention as a short wavelength light source corresponding to a high-density optical recording medium. Further, it is expected not only as an optical recording medium but also as a visible light source such as an illumination or a backlight. Further, in order to expand the usage applications, technological development for stabilizing the operation while improving the light emission output of the nitride semiconductor laser element is being studied.

  FIG. 11 is a cross-sectional view of a conventional semiconductor laser light source (see, for example, Patent Document 1). The conventional semiconductor laser light source includes a semiconductor laser chip 91 that emits laser light. The semiconductor laser chip 41 is attached to a heat sink 92. A heat sink 92 is joined to the bottom surface of the stem 93. The light detection element 94 is disposed on the back surface of the stem 93 in order to monitor the intensity of the laser light emitted from the semiconductor laser chip 91. An electrode lead wire 95 for GND, for driving a semiconductor laser, and for a light detection element is attached to the opposite surface of the stem 93. The electrode for GND is connected to the stem 93, and the electrodes for driving the semiconductor laser and the light detecting element are connected to the semiconductor laser chip 91 and the light detecting element 94 by wire bonding (not shown), respectively.

  The semiconductor laser light source shown in FIG. 11 has a structure in which a semiconductor laser chip 91, a heat sink 92, and a light detection element 94 are sealed with a stem 93 and a cap 96. There is also described a mode in which the internal atmosphere 97 of the cap 96 is an inert gas atmosphere, which makes it possible to install the semiconductor laser device in a vacuum environment or a high-pressure environment.

In the patent document 2, the inventors sealed the inside of the cap with an atmosphere containing oxygen, not an inert gas, but a component that suppresses hydrogen diffusion, so that the semiconductor laser chip is being driven. It was shown that the voltage rise that occurs can be suppressed and the operation can be stabilized. Although the detailed model is not yet clear, when oxygen is contained in the cap sealing atmosphere, hydrogen diffusion from the members constituting the semiconductor laser chip into the semiconductor layer of the chip is suppressed. As a result, an increase in resistance of the p-type semiconductor layer constituting the semiconductor laser chip is suppressed, and an increase in operating voltage during operation can be suppressed.
JP 10-313147 A Japanese Patent Application No. 2006-346520

  However, as the output of a nitride semiconductor laser increases, if the cap sealing atmosphere contains a large amount of oxygen, depending on the configuration of the semiconductor laser chip, the chip is locally oxidized, which adversely affects the characteristics. It has become clear that it may affect

  For example, if the metal used for the electrode is oxidized, the operating voltage of the semiconductor laser device gradually increases during long-term energization. Further, in a high-power semiconductor laser device of 200 mW class or higher, when a part of the light emitting end face is oxidized, the laser light is absorbed at that part and generates heat, resulting in COD and laser oscillation being stopped.

  For this reason, in particular, in a laser package corresponding to a high-power laser device exceeding 200 mW, there has been a restriction that the oxygen concentration in the cap sealing atmosphere cannot be increased so much. Specifically, it has been empirically found that the local oxidation problem cannot be avoided unless the oxygen concentration is suppressed to about 30% or less.

  However, when the oxygen concentration in the cap sealing atmosphere is lowered, the effect of suppressing the diffusion of hydrogen into the semiconductor layer of the semiconductor laser chip, which is the original effect of oxygen, is also reduced, and an element that exhibits an abnormal operating voltage is generated. I came to do. Furthermore, to spur this problem, in the case of a high-power laser, the drive current value inevitably increases, and as a result, the amount of heat generated during the operation of the element also increases, so that the suppression of hydrogen diffusion is further suppressed. It becomes difficult.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an improved semiconductor light-emitting device so that the operating voltage of the device does not increase during long-time driving.

  Another object of the present invention is to provide a semiconductor light emitting device improved so that the operating voltage of the element does not increase during long-time driving even when the concentration of oxygen contained in the cap sealing atmosphere is low. is there.

A semiconductor light emitting device according to the present invention includes a p-type semiconductor layer and an n-type semiconductor layer having a ridge stripe structure, which are joined with an active layer interposed therebetween. A first p-type electrode formed in substantially the same shape as the top of the convex portion of the ridge stripe structure is provided so as to be in electrical contact only with the top of the convex portion of the ridge stripe structure . Provided on the p-type semiconductor layer so as to sandwich and cover the convex portion of the ridge stripe structure from both sides, and to form a current confinement structure, a current path is formed on the surface of the first p-type electrode An insulating layer having an opening is provided. A second p-type electrode is provided on the first p-type electrode and the insulating layer. A hydrogen adsorption layer including a metal that adsorbs hydrogen is provided between the second p- type electrode and the p-type semiconductor layer in a region outside the opening . According to the present invention, the hydrogen adsorbing layer suppresses the diffusion of hydrogen existing in the insulating layer to the active layer by the force of sucking the hydrogen. Therefore, for example, in the case of a group III nitride semiconductor light-emitting device using Mg as a p-type dopant, it is possible to suppress the formation of a composite of Mg and hydrogen, and to reduce the hole concentration and the accompanying resistance of the p-type semiconductor layer. Therefore, the increase in the operating voltage of the element can be avoided and the operating voltage of the element can be kept stable without increasing.

  The semiconductor light emitting element includes a semiconductor laser, a light emitting diode (LED), and a super luminescent diode.

  The hydrogen adsorption layer may be provided between the insulating layer and the p-type semiconductor layer, the hydrogen adsorption layer may be provided so as to be sandwiched between the insulating layers, It may be provided so as to contact the surface of the insulating layer.

  The hydrogen adsorption layer and the insulating layer may be composed of a single integrated layer. In this case, the concentration of the metal that adsorbs hydrogen in the integrated layer is on the p-type electrode side. It is preferable that the height be higher on the p-type semiconductor layer side. In this case, the concentration of the metal that adsorbs hydrogen is particularly preferably increased in a gradation as it approaches the p-type semiconductor layer. With this configuration, when hydrogen that has started to diffuse from the insulating layer toward the semiconductor layer reaches the hydrogen adsorption layer, it is strongly attracted to the metal element contained in the hydrogen adsorption layer, and the diffusion phenomenon stops on the spot. It is.

The metal that adsorbs hydrogen is preferably a metal having a smaller heat of formation of hydride than the heat of formation of Mg hydride. With this configuration, when hydrogen that has started to diffuse in the semiconductor layer direction from the insulating layer reaches the hydrogen adsorption layer, it is strongly attracted to the metal element contained in the hydrogen adsorption layer.
In the case of a structure in which the hydrogen adsorption layer is in contact with the surface of the insulating layer, hydrogen exists in the insulating layer and does not pass through the hydrogen adsorption layer. Is attracted to the hydrogen adsorption layer, so that hydrogen diffusion is suppressed.

  The film thickness of the hydrogen adsorption layer is 1 nm or more, preferably 5 nm or more where a continuous film is formed. However, even a discontinuous film has an effect of hydrogen adsorption.

The insulating layer contains hydrogen at a concentration of 1 × 10 ¹⁷ atoms / cm ³ or more.

According to a preferred embodiment of the present invention, the semiconductor light emitting device is provided with a ridge stripe structure on the surface side, and one electrode is formed so as to be in electrical contact only with the top of the convex portion of the ridge stripe structure. A convex portion of the ridge stripe structure, wherein the hydrogen adsorption layer and an insulating layer containing hydrogen at a concentration of 1 × 10 ¹⁷ atoms / cm ³ or more are provided outside the convex portion of the ridge stripe structure. It is provided so that it may be inserted.

A semiconductor light emitting device according to another preferred embodiment of the present invention includes a p-type semiconductor layer and an n-type semiconductor layer having a ridge stripe structure, joined via an active layer, and a top of a convex portion of the ridge stripe structure. The p-type semiconductor so as to sandwich and cover the first ridge electrode of the ridge stripe structure from both sides so as to be in electrical contact only with the first p-type electrode formed in substantially the same shape as the top of the protrusion of the ridge stripe structure. A different polarity with the same composition and different polarity as the p-type semiconductor layer, which is provided on the layer and has an opening serving as a current path on the surface of the first p-type electrode in order to form a current confinement structure A semiconductor layer, a second p-type electrode provided on the first p-type electrode and the heteropolar semiconductor layer, and a region outside the opening between the second p-type electrode and the p-type semiconductor layer. Located in It was, and a hydrogen adsorption layer containing a metal adsorbing hydrogen.

  The metal adsorbing hydrogen is Li, Na, K, Ca, Sc, Ti, Rb, Sr, Y, Zr, Cs, Ba, La, Hf, Ta, Ce, Pr, Nd, Sm, Eu, Gd, It is a metal selected from the group consisting of Tb, Dy, Ho, and Er, and the hydrogen adsorption layer is made of the metal, an oxide thereof, a nitride thereof, or a fluoride thereof. When Ti, Zr, and Hf are contained, the process problems, the refractive index, the insulating properties, and the adhesion to others are particularly excellent.

The insulating layer is selected from the group consisting of SiO ₂ , TiO ₂ , ZrO ₂ , HfO ₂ , CeO ₂ , In ₂ O ₃ , Nd ₂ O ₅ , Sb ₂ O ₃ , SnO ₂ , Ta ₂ O ₅ and ZnO. Including dielectrics.
When SiO ₂ or TiO ₂ is used, it is particularly excellent in process problems, refractive index, insulation, and adhesion with others.

  The present invention is effective when hydrogen is contained in the semiconductor layer structure of the semiconductor light emitting device.

  The present invention is effective when the semiconductor light emitting element is a group III nitride semiconductor light emitting element such as BN, AlN, InN, GaN, or TlN. These mainly oscillate at wavelengths of 350 nm to 550 nm. Wavelengths of 350 nm or more and 550 nm or less have high energy, and when such light is output, hydrogen is easily activated and diffused, and light deterioration is likely to occur. In such a case, the present invention is particularly effective. In the case of a group III nitride semiconductor light emitting device, the dopant of the p-type semiconductor layer is Mg, and the present invention is particularly effective.

  The present invention is also effective when the semiconductor light emitting device is a III-V compound semiconductor light emitting device such as GaAs. These mainly oscillate at a wavelength of 550 nm or more.

A semiconductor light emitting device according to another aspect of the present invention is provided with a stem, a heat sink installed in the stem, at least one semiconductor light emitting element provided in the heat sink, and installed in the stem from the semiconductor light emitting element. a light detecting element for detecting light, provided on said stem, said heat sink, the semiconductor light emitting device that includes a cap for sealing therein the semiconductor light emitting element and the light detecting element, the semiconductor The light emitting device includes the p-type semiconductor layer and the n-type semiconductor layer having a ridge stripe structure joined through an active layer, and the ridge stripe so as to be in electrical contact only with the top of the convex portion of the ridge stripe structure. The first p-type electrode formed in substantially the same shape as the top of the convex part of the structure and the convex part of the ridge stripe structure sandwiched from both sides As described above, the p-type semiconductor layer is provided on the p-type semiconductor layer and has an opening serving as a current path on the surface of the first p-type electrode in order to form a current confinement structure. A heteropolar semiconductor layer having a different composition and polarity; a second p-type electrode provided on the first p-type electrode and the heteropolar semiconductor layer; and the second p-type electrode in a region outside the opening. and the provided located between the p-type semiconductor layer, and a hydrogen adsorption layer containing a metal adsorbing hydrogen, the atmosphere inside the cap, the diffusion of the hydrogen contained in the semiconductor light emitting element The component which suppresses is contained, It is characterized by the above-mentioned.

  The component that suppresses the diffusion of hydrogen is preferably oxygen. In addition to the action of the hydrogen adsorption layer, when oxygen is contained in the cap sealing atmosphere, hydrogen in the semiconductor layer moves so as to be attracted toward the oxygen. The direction of movement of hydrogen and the direction of hydrogen diffusion are balanced in opposite directions. As a result, the diffusion of hydrogen is remarkably suppressed in synergy with the action and effect of the hydrogen adsorption layer.

  The concentration of oxygen contained in the atmosphere is preferably 30% or less. This is because local oxidation is prevented.

  It is preferable that the concentration of water contained in the atmosphere is less than 1000 ppm. More preferably, it is 500 ppm or less.

  The pressure of the atmosphere is preferably 0.1 Pa or more and 200 kPa or less.

  It is preferable that carbon dioxide is contained in the atmosphere.

  Argon is preferably contained in the atmosphere.

  When a semiconductor light emitting device according to the present invention is created, a hydrogen adsorption layer containing a metal that adsorbs hydrogen is disposed between the p-type electrode and the p-type semiconductor layer, so that the cap sealing atmosphere is provided. Even when the concentration of hydrogen contained in the element, typically oxygen, is low, even if the element is energized, hydrogen in the insulating layer is prevented from diffusing into the semiconductor layer. Rarely does not reach the semiconductor layer. Therefore, for example, when applied to a group III nitride light-emitting device, Mg, which is a p-type impurity in the semiconductor layer, is not compensated by hydrogen, and the acceptor concentration and thus the hole concentration is not reduced. As a result, the crystal does not increase in resistance, and the operating voltage does not increase even if the current is injected at a high density and driven for a long time. As a result, it is possible to suppress the occurrence of defects due to an increase in element operating voltage when current is applied.

  Even if the concentration of oxygen contained in the cap sealing atmosphere is low, the object is to obtain an improved semiconductor light emitting device so that the operating voltage does not increase even when driven for a long time. This is realized by mounting a semiconductor light emitting element provided with a hydrogen adsorption layer containing a metal that adsorbs hydrogen, which is provided between the two types of semiconductor layers. Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram of a nitride semiconductor laser device equipped with a nitride semiconductor device according to Example 1 of the present invention. The nitride semiconductor device according to the present invention includes a stem 40. The heat sink 20 is installed on the stem 40. At least one nitride semiconductor laser chip 10 that emits laser light is bonded to the heat sink 20. The nitride semiconductor laser chip 10 includes a hydrogen adsorption layer 221 containing a metal that adsorbs hydrogen, which will be described later. A light detection element 30 for observing the intensity of light from the nitride semiconductor laser chip 10 is installed on the stem 40. A cap 50 for sealing the heat sink 20, the nitride semiconductor laser chip 10, and the photodetecting element 30 therein is joined to the stem 40.

  The stem 40 is provided with an electrode lead wire 70, and the cap 50 is provided with a window 60 for taking out light emitted from the nitride semiconductor laser chip 10. An enclosed atmosphere 80 is sealed in the space inside the cap 50. The sealed atmosphere 80 contains a component that suppresses diffusion of hydrogen contained in the nitride semiconductor laser chip 10, typically oxygen. As gas components other than oxygen, carbon dioxide is mixed in addition to inert gases such as nitrogen, rare gases such as argon. The diameter of the cap 50 is 3 to 6 mm, for example. The nitride semiconductor laser chip 10 has, for example, a length of 0.4 to 0.8 mm, a width of 0.1 to 0.3 mm, and a thickness of 0.1 to 0.2 mm. Such a nitride semiconductor laser device is used, for example, in a pickup device for a large-capacity optical disk.

  The upper limit of the oxygen concentration is set to 30% or less in order to suppress local oxidation of the nitride semiconductor laser chip 10. In the case of the present embodiment, since the nitride semiconductor laser chip 10 including the hydrogen adsorption layer 221 is mounted, the hydrogen adsorption layer 221 suppresses diffusion of hydrogen into the active layer by the force of sucking the hydrogen. Even if the oxygen concentration is, for example, 0%, a considerable effect can be obtained.

Moreover, the pressure of the said enclosed atmosphere should just be in the range of 0.1 Pa or more and 200 kPa or less.
Moreover, the water concentration contained in the enclosed atmosphere is suppressed to less than 1000 ppm, and more preferably, the effect of the present invention is easily exhibited by suppressing the concentration to 500 ppm or less.

The group III nitride semiconductor laser used in this example is B _v Al _w Ga _x In _y Tl _z N (0 ≦ v ≦ 1, 0 ≦ w ≦ 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, It is made of a nitride semiconductor crystal represented by the formula of 0 ≦ z ≦ 1, v + w + x + y + z = 1). Here, B represents boron, Al represents aluminum, Ga represents gallium, In represents indium, Tl represents thallium, and N represents nitrogen. Further, v represents the content ratio of boron, w represents the content ratio of aluminum, x represents the content ratio of gallium, y represents the content ratio of indium, and z represents the content ratio of thallium. In the present specification, for example, a nitride semiconductor layer made of a nitride semiconductor crystal represented by an equation of Al _w Ga _x N (0 <w <1, 0 <x <1, w + x = 1) is abbreviated as an AlGaN layer. To do.

  When the nitride semiconductor crystal constituting the nitride semiconductor layer is a hexagonal crystal, 10% or less of the nitrogen element in the nitride semiconductor layer is at least one element of arsenic, phosphorus, and antimony May be substituted. Further, the nitride semiconductor layer is doped with at least one of silicon, oxygen, chlorine, sulfur, selenium, carbon, germanium, zinc, cadmium, magnesium and beryllium, and the nitride semiconductor layer is p-type, n-type, It has any i-type conductivity.

  The nitride semiconductor crystal is manufactured by a metal organic chemical vapor deposition method (MOCVD method). In the MOCVD method, since hydrogen is contained in the carrier gas or the group V source gas, hydrogen is also taken into the nitride semiconductor crystal. A molecular beam epitaxy method (MBE method) is sometimes used as a method for growing a nitride semiconductor crystal. In this case, too, when ammonia or the like is used as a group V material, hydrogen is taken into the nitride semiconductor crystal. It is.

  The oscillation wavelength of group III nitride semiconductor laser device 10 is mainly in the wavelength range of 350 nm to 550 nm. In the above description, the group III nitride semiconductor laser is used as the light emitting element. However, the effects of the present invention can be obtained in the same way even when the light emitting element is replaced with a nitride semiconductor superluminescent diode or a nitride semiconductor light emitting diode.

  Hereinafter, the structure of the group III nitride semiconductor laser device 10 mounted in the present embodiment will be described in more detail.

  FIG. 2A is a schematic cross-sectional view of a semiconductor laser chip used in the semiconductor laser device according to the first embodiment of the present invention. FIG. 2B is a perspective view thereof.

This semiconductor laser device 10 includes an n-type GaN layer 201 having a thickness of 0.5 μm, an n-type Al _0.05 Ga _0.95 N lower cladding layer 202 having a thickness of 2 μm, and an n-type GaN layer 201 having a thickness of 0.1 μm. GaN guide layer 203, GaN lower adjacent layer 204 having a thickness of 20 nm, active layer 205 (details will be described later), GaN upper adjacent layer 206 having a thickness of 50 nm, p-type Al _0.2 Ga _0.8 N layer 207 having a thickness of 20 nm, A p-type Al _0.1 Ga _0.9 N upper clad layer 208 having a thickness of 0.6 μm and a p-type GaN contact layer 209 having a thickness of _0.1 μm are sequentially formed. On the back surface of the substrate, a negative electrode 220 and a positive electrode 230 (details will be described later) are formed in contact with the p-type GaN contact layer 209. Further, the upper clad layer 208 and the contact layer 209 are formed in a stripe shape having a convex structure extending in the resonator direction, and constitute a ridge stripe waveguide.

  A hydrogen adsorption layer 221 that suppresses hydrogen diffusion and an insulating film 222 are embedded outside the convex portion of the ridge stripe structure, and one electrode is formed so as to be in electrical contact only with the top of the convex portion. In this way, current confinement is realized by limiting the portion through which current flows. The shape of the output light spot can be generally controlled by the current confinement structure. By passing a current between the positive electrode 230 and the negative electrode 220, light is output as shown in the figure.

The hydrogen adsorption layer 221 was formed of a dielectric layer made of HfO ₂ .
The insulating layer 222 is formed of a dielectric layer made of SiO ₂ containing hydrogen at a concentration of 1 × 10 ¹⁷ atoms / cm ³ or more.

  The width of the convex portion of the ridge stripe was about 1.6 μm, and the resonator length was 600 μm. An AR (anti-reflective) coating was applied to the front surface of the device, and an HR (high reflection) coating was applied to the rear surface.

The layer exhibiting the p-type conductivity is doped with magnesium (Mg) as a dopant at a concentration of 1 × 10 ¹⁹ to 1 × 10 ²⁰ atoms / cm ³ . The upper cladding layer 208 and the contact layer 209 are typically doped at 4 × 10 ¹⁹ atoms / cm ³ . In this embodiment, the p-type GaN contact layer 209 may be omitted, and the upper cladding layer 208 may also serve as the contact layer.

The active layer 205 includes an undoped In _0.15 Ga _0.85 N well layer (thickness: 4 nm) and an undoped GaN barrier layer (thickness: 8 nm). The active layer 205 includes a well layer, a barrier layer, a well layer, a barrier layer, and a well layer. It is a multiple quantum well structure (3 wells) formed in order. Well layer and the barrier _{layer, In x Ga 1-x N} (0 ≦ x <1), Al x Ga 1-x N (0 ≦ x <1), In x Ga 1-xy Al y N (0 ≦ x <1, 0 ≦ y <1), GaN _1-x As _x (0 <x <1), GaN _1-x P _x (0 <x <1), or a nitride semiconductor such as these compounds. . The barrier layer has a composition such that the band gap energy is larger than that of the well layer. For the purpose of lowering the oscillation threshold of the device, the active layer is preferably a multiple quantum well structure (MQW structure) having 2 to 4 wells, but excludes the single quantum well structure (SQW structure). is not. In this case, there is no barrier layer sandwiched between well layers as used in this specification.

  The positive electrode 230 includes a first layer 231 (Pd layer / Mo layer), a second layer 232 (barrier layer), and a third layer 233 (pad) from the side in contact with the p-type GaN contact layer 209. Here, the layer above the barrier layer is also formed on the insulating film 222. Therefore, the barrier layer preferably has good adhesion to the insulating film and also has a function for improving adhesion. The Pd layer is a layer for making ohmic contact with the p-type nitride semiconductor.

  The semiconductor laser chip having the above structure can be manufactured by a known nitride semiconductor crystal growth method. Each semiconductor layer is stacked by MOCVD or MBE, and a ridge stripe structure is formed by etching using dry etching. For the lamination of the layers constituting the positive and negative electrodes, a general vacuum film forming method such as a high frequency sputtering method is used in addition to an electron beam (EB) vacuum vapor deposition method.

The semiconductor laser chip of Example 1 manufactured as described above was mounted in a semiconductor laser device (laser package) and an energization test was performed.
The gas atmosphere enclosed by the cap was a mixed gas of 20% oxygen and 80% nitrogen. At that time, the water concentration contained in the mixed gas was suppressed to 100 ppm (dew point of about −40 ° C.). The test conditions were a constant light output drive with a pulse of 210 mW at a high temperature of 80 ° C., and the operating voltage was monitored.

As a result, the semiconductor laser device of this example continued to run stably at a constant operating voltage (about 4.6 V) even after 200 hours had passed. The resulting graph is shown in FIG. FIG. 3 shows the results of driving three semiconductor laser device samples with different symbols. As described above, the semiconductor laser device of this example showed stable voltage characteristics even under a high current density driving condition of about 17 kA / cm ² .
(Comparative example)

As a comparison with this example, a semiconductor laser device was manufactured using a semiconductor laser chip having the same configuration as that of this example except that the hydrogen adsorption layer was omitted, and the same energization test as described above was performed.
FIG. 4 shows the results of driving five semiconductor laser device samples with different symbols. As a result of pulse 210 mW constant light output driving at 80 ° C., the operation voltage increased frequently as shown in FIG.

  (Consideration)

  A model in which the increase in operating voltage as seen in the comparative example is suppressed in the first embodiment is considered as follows.

  As shown in Patent Document 2 by the inventors, referring to FIG. 5, the cause of the increase in operating voltage is considered to be the diffusion of hydrogen indicated by an arrow into the semiconductor laser chip. The diffused hydrogen forms a complex with Mg, which is a dopant of the p-type semiconductor layer of the semiconductor laser chip, and decreases the activation rate. As a result, the hole concentration decreases and the resistance of the p-type semiconductor layer increases. This is presumed to be a mechanism for increasing the operating voltage of the element.

The main origin of this hydrogen is presumed to be the insulating layer 222 which constitutes a part of the element structure. As a result of SIMS analysis conducted by the inventors on the SiO ₂ film that is often used as the insulating layer 222 and used in Example 1, the hydrogen concentration contained reaches a high level of the order of 10 ²¹ atoms / cm ^{3 in} some cases. I understood that. The measured film was formed using an electron beam type vacuum deposition apparatus often used in the manufacturing process of a semiconductor laser. However, even if another film forming method such as a sputtering apparatus is used, depending on the film forming conditions, it is 10 ^19. It is quite possible that hydrogen is contained in the film on the order of -10 ²¹ atoms / cm ³ .

  As described above, when a current is applied to the laser chip provided with the insulating layer containing hydrogen at a high concentration, hydrogen contained in the insulating layer 222 tends to diffuse toward the semiconductor layers 208, 207, and 206. However, the oxygen component contained in the cap sealing atmosphere stops the diffusion of hydrogen in the semiconductor layer and fixes the hydrogen. Although the mechanism is not clear, referring to FIGS. 2 and 5 again, when the cap sealing atmosphere 80 contains oxygen, that is, the atmosphere gas surrounding the nitride semiconductor laser element 10 contains oxygen. Thus, hydrogen in the semiconductor layer moves so as to be attracted toward this oxygen. The direction of hydrogen movement and the hydrogen diffusion direction typically indicated by arrow 1 in the figure are balanced in opposite directions, and as a result, it is considered that hydrogen diffusion apparently stops.

  As described above, when the cap sealing atmosphere contains a component that suppresses hydrogen diffusion, typically oxygen, diffusion of hydrogen to the semiconductor layer side is suppressed. In Example 1, since oxygen is contained in the cap sealing atmosphere, diffusion of hydrogen to the semiconductor layer side is thereby suppressed. However, as mentioned above, since the problem of local oxidation becomes conspicuous as the output of the semiconductor laser increases, the concentration of oxygen, which plays a role in suppressing hydrogen diffusion, cannot be increased too much.

Therefore, in Example 1, not only the effect of oxygen contained in the cap sealing atmosphere but also a new hydrogen adsorption layer 221 is provided on the semiconductor laser chip as a means for suppressing the diffusion of hydrogen from the insulating layer to the semiconductor layer. It was. In Example 1, HfO ₂ was used as the hydrogen adsorption layer 221, but when the inventors examined various materials, it was found that the same effect as in Example 1 could be obtained with TiO ₂ or ZrO _2. It was. When the examination range was further expanded, in order to obtain the effect of suppressing the diffusion of hydrogen, not only Hf, Ti, Zr but also Li, Na, K, Ca, Sc, Rb, Sr, Y, Cs, Ba, La It has been found that elements such as Ta, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er may be contained in the hydrogen adsorption layer. The hydrogen adsorption layer may be a film made of these elements, oxides of these elements, nitrides, or fluorides.

  A common feature of these metal elements is that the heat of formation of the hydride is extremely small. The value is smaller than the heat of hydride generation of the p-type dopant Mg of the semiconductor laser chip where the diffused hydrogen is expected to form a composite. For this reason, when hydrogen that has started to diffuse from the insulating layer toward the semiconductor layer reaches the hydrogen adsorption layer, it is presumed that the diffusion phenomenon stops because it is strongly attracted to the metal element contained in the hydrogen adsorption layer. Accordingly, it is possible to suppress the formation of a composite of Mg and hydrogen, avoid a decrease in the hole concentration and an accompanying increase in the resistance of the p-type semiconductor layer, and keep the device stable without increasing the operating voltage. It is.

  Note that the thickness of the hydrogen adsorption layer 221 needs to be 5 nm or more in order to form a continuous film. However, the combination of the elements contained and the oxygen concentration contained in the cap sealing atmosphere has the effect of suppressing hydrogen diffusion at 1 nm or more. There is no particular upper limit, but if it is too thick, the influence on the design of the optical characteristics of the semiconductor laser element becomes large, so it is preferable to set it to 10 nm or more, and generally 50 nm at the most.

  The moisture concentration contained in the cap sealing atmosphere is preferably less than 1000 ppm. More desirably, the moisture concentration should be suppressed to 500 ppm or less.

  The pressure of the sealing atmosphere is also preferably 0.1 Pa or more and 200 kPa or less.

  Further, the gas species enclosed as a mixed gas simultaneously with oxygen is not limited to an inert gas such as nitrogen, or a rare gas such as argon, but the effect of the present invention can be obtained even when carbon dioxide is selected. Or it cannot be overemphasized that these mixed gas may be sufficient.

Further, regarding the relationship between the hydrogen concentration inside the insulating layer and the device operating voltage rise, when the hydrogen concentration inside the insulating layer is higher than 10 ¹⁷ atoms / cm ³ , the phenomenon that the device operating voltage rises frequently occurs. It was found that the phenomenon was sufficiently suppressed by including oxygen in the cap sealing atmosphere as in Example 1 and providing a hydrogen adsorption layer between the insulating layer and the semiconductor layer.

  1 shows a schematic diagram in which the nitride semiconductor laser chip 10 and the heat sink 20 are directly joined, but the nitride semiconductor laser chip 10 and the heat sink 20 may be joined via a submount. Absent.

  Also, in the same best example 1, a group III nitride semiconductor laser is used as the light emitting element, but it is considered that the cause of the operating voltage rise is the hydrogen inside the element as already explained in the model. The present invention is effective even when an element made of a group III-V compound semiconductor of aluminum, indium, gallium, arsenic, or phosphorus is used as a substitute. In the case of a III-V compound semiconductor, hydrogen is simultaneously taken into the crystal when doping Mg as a p-type impurity, or hydrogen contained in an insulating film formed as a part of the element structure is transferred to the semiconductor side. Since a phenomenon of diffusion occurs, there is a case where hydrogen is contained inside the element structure. By introducing oxygen into the cap sealing atmosphere and providing a hydrogen adsorption layer between the insulating layer and the semiconductor layer, it is possible to suppress the hydrogen from compensating for the p-type impurity Mg.

In the first embodiment, the SiO ₂ film is described as an example of the insulating film 222. In addition to this, TiO ₂ , ZrO ₂ , HfO ₂ , CeO ₂ , In ₂ O ₃ , Nd ₂ O ₅ , Sb ₂ O are used. ₃ It was confirmed that the effects of the present invention can be obtained with respect to SnO ₂ , Ta ₂ O ₅ , ZnO, or a mixture thereof.

In the first embodiment, the semiconductor light emitting device having the current confinement structure in which the hydrogen adsorption layer 221 and the insulating layer 222 are formed so as to sandwich the convex portion of the ridge stripe is illustrated. However, the present invention is not limited to this. Instead of the insulating layer, a semiconductor layer having approximately the same composition and polarity as the convex portion of the ridge stripe and containing hydrogen at a concentration of 1 × 10 ¹⁷ atoms / cm ³ or more is formed on the convex portion of the ridge stripe. A semiconductor light emitting device having a current confinement structure provided outside the portion has the same effect.

The present invention can be applied to a nitride semiconductor laser, particularly a semiconductor laser emitting a high light output of 200 mW or more. Such devices typically require driving at high current densities, such as exceeding 15 kA / cm ² . Also, a semiconductor laser device using a nitride semiconductor, for example, a single semiconductor laser device, a hologram laser device having a hologram element, and an optical package packaged integrally with an IC chip for processing such as driving or signal detection. The present invention is applicable to an electronic IC device, a waveguide or a composite optical device packaged integrally with a micro optical element. In addition, the present invention can be applied to an optical recording system, an optical disk system, a light source system in the ultraviolet to green region, etc. provided with these devices.

  In the above, oxygen is exemplified as a component for suppressing hydrogen diffusion, but the present invention is not limited to this, and any gas can be used as long as hydrogen diffusion is stopped.

  FIG. 6 is a cross-sectional view of the semiconductor light emitting device according to the second embodiment. The same parts as those of the semiconductor light emitting device shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The difference from the first embodiment is that the hydrogen adsorption layer 221 is provided so as to be sandwiched between the insulating layers 222. Even in such a structure, hydrogen is attracted to the hydrogen adsorption layer 221 and the diffusion of hydrogen is suppressed. In addition, this embodiment is effective when the hydrogen adsorption layer 221 is inferior in insulation. The metal that adsorbs hydrogen can be added not in the form of oxide, nitride, or fluoride, but in the form of a metal element.

  FIG. 7 is a cross-sectional view of the semiconductor light-emitting device according to Example 3. The same parts as those of the semiconductor light emitting device shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The difference from the first embodiment is that the hydrogen adsorption layer 221 is provided in contact with the surface of the insulating layer 222. In the case of such a structure, the hydrogen that exists in the insulating layer 222 and moves toward the active layer does not pass through the hydrogen adsorbing layer 221, but hydrogen is attracted to the hydrogen adsorbing layer 221; Is suppressed.

  FIG. 8 is a cross-sectional view of the semiconductor light emitting device according to Example 4. The same parts as those of the semiconductor light emitting device shown in FIG. The difference from the first embodiment is that the hydrogen adsorbing layer and the insulating layer are integrated into one layer, and the concentration of the metal 221a that adsorbs hydrogen in the integrated layer 222a is p. The height is higher on the p-type semiconductor layer side, that is, on the active layer side than on the mold electrode 230 side. More preferably, the concentration of the metal 221a that adsorbs hydrogen is graded so as to gradually increase as it approaches the p-type semiconductor layer. Such a structure has an advantage that it can be formed in a single process by an electron beam vacuum deposition method having two deposition sources. Hydrogen is adsorbed at a portion where the concentration of the metal 221a that adsorbs hydrogen is high, and its diffusion is stopped. In the present embodiment, the case where the density is changed in a gradation is illustrated, but the density may be changed in a step shape.

  FIG. 9 is a cross-sectional view of the semiconductor light-emitting device according to Example 4. The same parts as those of the semiconductor light emitting device shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The difference from the first embodiment is that an electrode stripe structure is used instead of the ridge structure. Even in such a structure, hydrogen in the insulating layer 222 toward the active layer 205 is attracted to the hydrogen adsorption layer 221 and fixed. Therefore, diffusion of hydrogen into the active layer 205 is suppressed.

  A method and an apparatus for manufacturing the nitride semiconductor laser device shown in FIG. 1 will be described.

  Referring to FIG. 10, the assembling apparatus has a front chamber 101 and a work chamber 102. The front chamber 101 allows members necessary for assembly to be introduced into the work chamber 102 without opening the work chamber 102 to the atmosphere. For this purpose, the front chamber 101 has a mechanism 103 for introducing a purge gas. The working chamber 102 has an assembling mechanism 104 capable of assembling the nitride semiconductor laser device inside, and the assembling work can be performed in a sealed space cut off from the outside. Between the front chamber 101 and the work chamber 102, a transport means for transporting members necessary for assembly (not shown) is provided, and is blocked by a door 109.

  The working chamber 102 has a vacuum mechanism 105 for evacuating the working chamber 102 so that the inside can reach a desired pressure, a desired kind of atmospheric gas, a desired oxygen concentration, and a desired dew point temperature. A gas introduction mechanism 106 for filling the inside of the working chamber with a desired atmospheric gas, a gas discharge mechanism 107 for exhausting the gas from the inside of the apparatus to the outside, and an oxygen concentration and a dew point temperature inside the working chamber 102 are provided. Is provided with a measuring mechanism 108.

  Next, the operation will be described. First, a semiconductor laser element including a hydrogen adsorption layer containing a metal that adsorbs hydrogen and other members necessary for assembly are carried into the front chamber 101 from the outside. The door 109 is closed and the inside of the front chamber 101 is replaced with a purge gas. The door 109 is opened, and members necessary for assembly are moved from the front chamber 101 to the work chamber 102 by using a transfer means (not shown). As a result, members necessary for assembly are introduced into the work chamber 102 without opening the work chamber 102 to the atmosphere. Next, the door 109 is closed, and the inside of the work chamber 102 is sealed. The pressure inside the working chamber 102, the type of atmospheric gas, the oxygen concentration or the dew point temperature are made the same as the sealing pressure, the type of sealed atmospheric gas, the oxygen concentration or the dew point temperature of the nitride semiconductor laser device described above. The semiconductor light emitting device is assembled using the assembly mechanism 104 in the work chamber 101 and in the above atmosphere. As a result, the atmosphere in the cap described above can be achieved simply by assembling the nitride semiconductor laser device inside the working chamber 102.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to a semiconductor laser device, a hologram laser device, an optoelectronic IC device, a composite optical device, and the like, and can suppress the occurrence of defects due to an increase in element operating voltage when current is applied.

1 is a conceptual diagram showing a nitride semiconductor laser device according to Example 1. FIG. 1 is a schematic cross-sectional view of a nitride semiconductor laser element used in Example 1. FIG. 3 is a graph showing a result of an energization test of the nitride semiconductor laser element shown in FIG. It is a graph which shows the result of the electricity supply test of the comparative element which does not contain a hydrogen adsorption layer. It is the figure which modeled the mode of hydrogen diffusion in a comparison element. 6 is a conceptual diagram showing a nitride semiconductor laser element according to Example 2. FIG. 7 is a conceptual diagram showing a nitride semiconductor laser element according to Example 3. FIG. 7 is a conceptual diagram showing a nitride semiconductor laser element according to Example 4. FIG. 7 is a conceptual diagram showing a nitride semiconductor laser element according to Example 5. FIG. FIG. 10 is a conceptual diagram of an assembling apparatus for a nitride semiconductor laser device in Example 6. It is sectional drawing of the conventional semiconductor laser light-emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nitride semiconductor laser chip 20 Heat sink 30 Photodetection element 39 Internal atmosphere 40 Stem 91 Semiconductor laser chip 92 Heat sink 93 Stem 94 Photodetection element 95 Electrode lead wire 96 Cap 97 Internal atmosphere 50 Cap 60 Window 70 Electrode lead wire 80 Enclosed atmosphere 200 Substrate 201 n-type GaN layer 202 lower clad layer 203 n-type GaN guide layer 204 lower adjacent layer 205 active layer 206 upper adjacent layer 207 p-type Al _0.2 Ga _0.8 N layer 208 p-type upper clad layer 209 p-type contact layer 220 negative electrode 221 Hydrogen adsorbing layer 222 Insulating film 221a Metal adsorbing hydrogen 222a Layer in which hydrogen adsorbing layer and insulating layer are integrated 230 Positive electrode 231 First layer 232 Second layer 233 Third layer

Claims (23)

A p-type semiconductor layer and an n-type semiconductor layer having a ridge stripe structure joined via an active layer;
A first p-type electrode formed in substantially the same shape as the top of the ridge stripe structure so as to make electrical contact only with the top of the ridge stripe structure;
Provided on the p-type semiconductor layer so as to sandwich and cover the convex portion of the ridge stripe structure from both sides, and to form a current confinement structure, a current path is formed on the surface of the first p-type electrode An insulating layer having an opening;
A second p-type electrode provided on the first p-type electrode and the insulating layer ;
A semiconductor light emitting element comprising: a hydrogen adsorption layer containing a metal that adsorbs hydrogen, and is provided between the second p- type electrode and the p-type semiconductor layer in a region outside the opening . 2. The semiconductor light emitting element according to claim 1, wherein the hydrogen adsorption layer is provided in contact with the p-type semiconductor layer so as to sandwich the p-type semiconductor layer having the ridge stripe structure from both sides .   The semiconductor light emitting element according to claim 1, wherein the hydrogen adsorption layer is provided so as to be sandwiched between the insulating layers.   The semiconductor light emitting element according to claim 1, wherein the hydrogen adsorption layer is provided in contact with a surface of the insulating layer.   The hydrogen adsorption layer and the insulating layer are composed of one integrated layer, and the concentration of the metal that adsorbs hydrogen in the integrated layer is higher than that of the p-type electrode side. The semiconductor light-emitting element according to claim 1, wherein the semiconductor light-emitting element is higher on the p-type semiconductor layer side.   6. The semiconductor light emitting element according to claim 5, wherein the concentration of the metal that adsorbs hydrogen is increased in a gradation shape as it approaches the p-type semiconductor layer.   7. The semiconductor light emitting element according to claim 1, wherein the metal that adsorbs hydrogen includes a metal having a smaller heat of formation of hydride than heat of formation of Mg hydride.   The semiconductor light emitting element according to claim 1, wherein the hydrogen adsorption layer has a thickness of 1 nm or more. The semiconductor light-emitting element according to claim 8, wherein the thickness of the hydrogen adsorption layer is 5 nm or more . The semiconductor light emitting device according to claim 1, wherein the first p-type electrode includes Pd . A p-type semiconductor layer and an n-type semiconductor layer having a ridge stripe structure joined via an active layer;
A first p-type electrode formed in substantially the same shape as the top of the ridge stripe structure so as to make electrical contact only with the top of the ridge stripe structure;
Provided on the p-type semiconductor layer so as to sandwich and cover the convex portion of the ridge stripe structure from both sides, and to form a current confinement structure, a current path is formed on the surface of the first p-type electrode A heteropolar semiconductor layer having an opening and having the same composition and different polarity as the p-type semiconductor layer;
A second p-type electrode provided on the first p-type electrode and the heteropolar semiconductor layer ;
A semiconductor light emitting element comprising: a hydrogen adsorption layer containing a metal that adsorbs hydrogen, and is provided between the second p- type electrode and the p-type semiconductor layer in a region outside the opening .   The metal that adsorbs hydrogen is Li, Na, K, Ca, Sc, Ti, Rb, Sr, Y, Zr, Cs, Ba, La, Hf, Ta, Ce, Pr, Nd, Sm, Eu, Gd, The metal selected from the group consisting of Tb, Dy, Ho, and Er, and the hydrogen adsorption layer is made of the metal, an oxide thereof, a nitride thereof, or a fluoride thereof. The semiconductor light-emitting device according to any one of 1 to 11.   The metal adsorbing hydrogen is Li, Na, K, Ca, Sc, Rb, Sr, Y, Zr, Cs, Ba, La, Hf, Ta, Ce, Pr, Nd, Sm, Eu, Gd, Tb, The metal selected from the group consisting of Dy, Ho, and Er, and the hydrogen adsorption layer is made of the metal, an oxide thereof, a nitride thereof, or a fluoride thereof. The semiconductor light emitting element as described. The insulating layer _is selected from _{SiO 2, TiO 2, ZrO 2} , HfO 2, CeO 2, In 2 O 3, Nd 2 O 5, Sb 2 O 3, SnO 2, Ta 2 O 5 and the group consisting of ZnO the semiconductor light-emitting device according to any one of claims 1 to 13 including a dielectric was. Wherein the hydrogen in the semiconductor layer structure of the semiconductor light emitting element is contained, the semiconductor light-emitting device according to any one of claims 1-14. The semiconductor light emitting device, characterized in that it is a group III nitride semiconductor light-emitting device, the semiconductor light-emitting device according to any one of claims 1 to 15. Stem,
A heat sink installed on the stem;
At least one semiconductor light emitting element provided on the heat sink;
A light detecting element installed on the stem for detecting light from the semiconductor light emitting element;
A cap provided on the stem, for sealing the heat sink, the semiconductor light emitting element, and the light detecting element therein;
Semiconductor atmosphere inside the cap, the includes a diffusion suppressing components of the hydrogen contained in the semiconductor light-emitting device, further said semiconductor light emitting device, comprising a semiconductor light-emitting device according to claim 1-16 Light emitting device. The semiconductor light-emitting device according to claim 17 , wherein the component that suppresses diffusion of hydrogen includes oxygen. 19. The semiconductor light emitting device according to claim 18 , wherein the concentration of oxygen contained in the atmosphere is 30% or less. 20. The semiconductor light-emitting device according to claim 17 , wherein a concentration of water contained in the atmosphere is less than 1000 ppm. 21. The semiconductor light emitting device according to claim 17 , wherein the pressure of the atmosphere is 0.1 Pa or more and 200 kPa or less. The semiconductor light-emitting device according to claim 17 , wherein carbon dioxide is contained in the atmosphere. The semiconductor light-emitting device according to claim 17 , wherein argon is contained in the atmosphere.