JP3869663B2 - Nitride semiconductor laser device and semiconductor optical device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitride semiconductor laser element having a long laser oscillation lifetime and a semiconductor optical device using the nitride semiconductor laser element.
[0002]
[Prior art]
Conventionally, SiO on a GaN substrate ₂ A mask pattern of the mask is formed, and the SiO ₂ Above the mask and the SiO ₂ A GaN layer is stacked above a window portion where no mask is formed, and a nitride semiconductor laser device is formed on the GaN layer. J. et al. Appl. Phys. Vol. 39 (2000) pp. L647-650 and the like.
[0003]
[Problems to be solved by the invention]
However, in the above disclosure, the SiO ₂ A detailed description has not been given of the formation position of the nitride semiconductor laser element formed on the GaN substrate having the mask.
[0004]
In the present specification, there is a nitride semiconductor layer laminated on a nitride semiconductor substrate, or a mask substrate in which a mask and a window are formed on the nitride semiconductor substrate, and the nitride manufactured on the mask substrate. The formation position of the current confinement portion of the semiconductor laser element will be described in detail. An object of the present invention is to provide a nitride semiconductor laser device having a long laser oscillation lifetime by optimizing the formation position of the current confinement portion.
[0005]
[Means for Solving the Problems]
Book Departure Clearly In the nitride semiconductor laser device according to the present invention, the nitride semiconductor layer laminated on the nitride semiconductor substrate Up Or nitride semiconductor substrate Nikko on From growth-suppressing films in which semiconductors suppress epitaxial growth Na Striped mask And before There is a mask substrate having a striped window portion on which no mask is formed, The width of the window is set to 5 μm or more and 20 μm or less, A light-emitting element structure having a nitride semiconductor film covering the mask substrate and a well layer sandwiched between at least an n-type layer and a p-type layer or a light-emitting layer composed of a well layer and a barrier layer; But Growing sequentially on the mask substrate Is , in front A region above the window portion and toward the stripe direction of the window portion. Width A current confinement portion of the light emitting element structure is formed in a region of 1 μm or more from the center to the left and right.
With the above features, the lifetime of the laser oscillation of the nitride semiconductor laser device, which is the subject of the present invention, can be extended.
[0006]
Here, the growth suppressing film described in this specification is defined as a film in which a nitride semiconductor is difficult to be epitaxially grown. For example, the growth suppression film can be composed of a dielectric film or a metal film. More specifically, the growth suppressing film is made of SiO. ₂ , SiN _x , Al ₂ O _Three TiO ₂ , Tungsten or molybdenum.
[0007]
The window portion described in this specification refers to a portion in which a mask composed of the growth suppression film is formed on a certain layer and the certain layer is not covered with the mask (a certain layer is exposed). Part).
[0008]
The nitride semiconductor substrate described in this specification means at least Al. _x Ga _y In _z It is a substrate composed of N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1). In the nitride semiconductor substrate, about 10% or less of the nitrogen element constituting the nitride semiconductor substrate (provided that the nitride semiconductor substrate is hexagonal) is at least one of the element group of As, P, or Sb. It may be replaced with an element. The nitride semiconductor substrate may be doped with at least one of an impurity group of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be. The total amount of impurities added is 5 × 10 ¹⁷ / Cm ^Three 5 × 10 or more ¹⁸ / Cm ^Three The following is preferred. The impurity for allowing the nitride semiconductor substrate to have n-type conductivity is particularly preferably Si, O, or Cl in the impurity group.
[0009]
The nitride semiconductor layer stacked on the nitride semiconductor substrate described in this specification means at least Al. _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1). In the nitride semiconductor layer, about 10% or less of the nitrogen element constituting the nitride semiconductor layer (provided that the nitride semiconductor layer is hexagonal) is at least one of the element groups of As, P, and Sb. It may be replaced with an element. The nitride semiconductor layer may be doped with at least one of the impurity groups of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be. The total amount of impurities added is 5 × 10 ¹⁷ / Cm ^Three 5 × 10 or more ¹⁸ / Cm ^Three The following is preferred. The impurity for allowing the nitride semiconductor layer to have n-type conductivity is particularly preferably Si, O, or Cl in the impurity group.
[0010]
The mask substrate described in this specification refers to a nitride semiconductor layer stacked on the nitride semiconductor substrate, or a mask formed of the growth suppressing film and the window portion on the nitride semiconductor substrate. (See FIG. 2). The width of the mask and the width of the window portion may have a constant period or may have different widths.
[0011]
The nitride semiconductor film grown on the mask substrate described in this specification is at least Al. _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1). In the nitride semiconductor film, about 10% or less of the nitrogen element constituting the nitride semiconductor film (provided that the nitride semiconductor film is hexagonal) is at least one of the element group of As, P, or Sb. It may be replaced with an element. The nitride semiconductor film may be doped with at least one of the impurity groups of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be. The impurity for allowing the nitride semiconductor film to have n-type conductivity is particularly preferably Si, O, or Cl in the impurity group.
[0012]
The film-coated mask substrate described in this specification is defined as a substrate in which the nitride semiconductor film is coated on the mask substrate (see FIG. 3).
[0013]
The light emitting layer described in this specification refers to a general term for a well layer or a layer composed of a well layer and a barrier layer. For example, a light emitting layer having a single quantum well structure is composed of only one well layer, or is composed of a barrier layer / well layer / barrier layer. The light emitting layer having a multiple quantum well structure includes a plurality of well layers and a plurality of barrier layers.
[0014]
The light emitting element structure described in this specification is defined as a structure in which the light emitting layer is sandwiched between an n-type layer and a p-type layer.
[0015]
The current confinement portion described in this specification is defined as a portion where current is substantially injected into the light emitting layer through the p-type layer. The current confinement width is defined as the width of the current confinement portion. Specifically, the current confinement portion will be described with reference to FIG. For example, in the case of a nitride semiconductor laser element having a ridge stripe structure, the current confinement portion corresponds to the ridge stripe portion shown in FIG. Thus, the current confinement width of the nitride semiconductor laser element having the ridge stripe structure corresponds to the ridge stripe width shown in FIG.
[0016]
Similarly, for example, in the case of a nitride semiconductor laser element having a current confinement layer, the current confinement portion corresponds to a portion sandwiched between two current blocking layers shown in FIG. Thus, the current confinement width of the nitride semiconductor laser element having the current confinement layer corresponds to the current blocking layer width shown in FIG.
[0019]
In the present invention, when the mask width is 5 μm or more and 30 μm or less, a current confinement portion can be formed in a region where the laser oscillation lifetime can be extended.
[0020]
In the present invention, the width of the window portion is 5 It is preferable that it is not less than μm and not more than 20 μm. In the present invention, since the mask width is wider than the window width, the crystal distortion is effectively relieved, and the laser oscillation lifetime can be further extended.
[0021]
In the present invention, the nitride semiconductor film is at least A. _x Ga _1-x By being composed of N (Al composition ratio x is 0.01 or more and 0.15 or less), it is possible to further improve the laser oscillation lifetime characteristics and to suppress the occurrence rate of cracks.
[0022]
In the present invention, the nitride semiconductor film is made of In. _x Ga _1-x N (In composition ratio x is 0.01 or more and 0.18 or less) is that the difference in the laser oscillation lifetime is small due to the difference in the region where the current confinement part is formed, and the element defect rate can be reduced. .
[0023]
According to the present invention, the lifetime of laser oscillation can be further increased by including at least one element of the element group of As, P, or Sb in the well layer.
[0024]
According to the present invention, the nitride semiconductor substrate is doped with at least one of the impurity groups of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be. Total addition amount is 5 × 10 ¹⁷ / Cm ^Three 5 × 10 or more ¹⁸ / Cm ^Three It is preferable that:
[0025]
The present invention relates to a semiconductor optical device using the nitride semiconductor laser element of the present invention. Since the semiconductor optical device uses the high-power laser (30 mW) having a long laser oscillation lifetime according to the present invention, a highly reliable product can be manufactured.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
The present invention relates to a nitride semiconductor layer laminated on a nitride semiconductor substrate, or a mask substrate having a mask and a window formed on the nitride semiconductor substrate, and comprising the nitride semiconductor film and the light emitting element structure. And a region excluding less than 1 μm left and right from the center of the mask toward the stripe direction of the mask, and a region excluding less than 1 μm left and right from the center of the window toward the stripe direction of the window In addition, the lifetime of the laser oscillation of the nitride semiconductor laser device, which is the subject of the present invention, can be increased by forming the current confinement portion of the light emitting device structure.
[0027]
The optimum position of the present invention where the current confinement portion of the nitride semiconductor laser element is formed on the mask substrate with a film is limited to the case where the substrate constituting the mask substrate is a nitride semiconductor substrate. This is for the following reason.
[0028]
A nitride semiconductor film grown on a mask substrate using a substrate other than a nitride semiconductor substrate (hereinafter referred to as a heterogeneous substrate) is compared with that grown on a mask substrate using a nitride semiconductor substrate. It receives strong stress strain. This is because the difference in thermal expansion coefficient between the dissimilar substrate and the nitride semiconductor film is very large as compared with that between the nitride semiconductor substrate and the nitride semiconductor film. Therefore, even if the nitride semiconductor substrate is replaced with a different substrate and the current confinement portion of the nitride semiconductor laser element is formed so as to belong to the optimum position of the present invention, the nitride semiconductor film coated on the mask substrate And the crystal distortion in the light emitting element structure cannot be relaxed as in the present invention. In addition, since the difference in thermal expansion coefficient between the dissimilar substrate and the nitride semiconductor film is very large compared to that between the nitride semiconductor substrate and the nitride semiconductor film, the dissimilar substrate itself warps. If the substrate including the light emitting element structure is warped, it becomes difficult to produce a current confinement portion of the nitride semiconductor laser element at a target position with good reproducibility.
[0029]
(About the optimal position where the current confinement portion of the nitride semiconductor laser device is manufactured) The present inventors have described that the current confinement portion of the nitride semiconductor laser device is a mask substrate with a film (the mask substrate is covered with a nitride semiconductor film It has been found as a new finding that the laser oscillation lifetime varies depending on the position of the substrate, which is a nitride semiconductor substrate.
[0030]
In the following, the optimum position of the current confinement portion will be described by taking a nitride semiconductor laser element (FIG. 4A) having a ridge stripe structure as an example. Here, as described above, the current confinement portion of the nitride semiconductor laser device having the ridge stripe structure corresponds to the ridge stripe portion of the laser device. The current confinement width of the nitride semiconductor laser element having the ridge stripe structure corresponds to the ridge stripe width of the laser element.
[0031]
First, the relationship between the formation position of the ridge stripe part and the laser oscillation lifetime will be described with reference to FIG.
[0032]
In FIG. 5, the horizontal axis represents the distance from the mask center c of the film-coated mask substrate to the ridge stripe end a, and the vertical axis represents the laser oscillation lifetime under the conditions of a laser output of 30 mW and an ambient temperature of 60 ° C. . Here, the distance from the mask center c to the ridge stripe end a (hereinafter referred to as “ca distance”) is expressed as positive on the right side and negative on the left side from the mask center c. Further, the laser oscillation lifetime described in this specification including FIG. 5 was estimated as follows. The laser oscillation lifetime is the time when a threshold current value 1.5 times the initial threshold current value when the nitride semiconductor laser element is set in the lifetime test apparatus is reached. The structure and manufacturing method of the nitride semiconductor laser element used in FIG. 5 are manufactured in the same manner as in the second embodiment described later. The ridge stripe width used in FIG. 5 was 2 μm, the mask width was 18 μm, the window width was 8 μm, and the mask thickness was 0.1 μm.
[0033]
(When the ridge stripe part is formed above the mask)
First, the case where the ridge stripe part is formed above the mask will be described. Referring to FIG. 5, the lasing lifetime of the nitride semiconductor laser device in which the ridge stripe portion was formed above the mask tended to be longer than that in which the ridge stripe portion was formed above the window portion. When the ridge stripe portion of the nitride semiconductor laser device is produced above the mask, the ridge stripe portion is produced in a region where the ca distance is larger than −3 μm and smaller than 1 μm. It has been found that the lasing lifetime is dramatically reduced (several hundred hours to less than 1000 hours). Here, considering that the width of the ridge stripe portion (hereinafter referred to as ridge stripe width) is 2 μm, the distance of −3 μm of the c−a distance is the distance from the mask center c to the ridge stripe end b ( (Hereinafter referred to as “cb distance”), the cb distance is −1 μm. That is, when the ridge stripe portion of the nitride semiconductor laser element is fabricated so as to be included at least in a region less than 1 μm on the left and right sides from the mask center c in the mask stripe direction (FIG. 2B), laser oscillation It has been found that the lifespan decreases dramatically. The region where the laser oscillation lifetime is dramatically reduced will be referred to as region III. Therefore, the ridge stripe portion of the nitride semiconductor laser element is preferably fabricated so that the entire region of the ridge stripe portion (a-b width in FIG. 5) is included in the region above the mask excluding the region III. .
[0034]
For the region III, it is more preferable from the viewpoint of laser oscillation lifetime characteristics to select the range described below in addition to the range less than 1 μm on the left and right from the mask center c. The region III is a region less than 2 μm on the left and right from the mask center c in the stripe direction of the mask (corresponding to a region larger than −4 μm and smaller than 2 μm when expressed by the ca distance in FIG. 5), The entire ridge stripe portion (width ab in FIG. 5) is included above the mask so as to exclude the III region. This makes it possible to obtain a laser oscillation lifetime of at least about 3000 to 5000 hours or longer. Further, the region III is a region less than 3 μm on the left and right sides of the mask center c in the stripe direction of the mask (corresponding to a region larger than −5 μm and smaller than 3 μm when expressed by the ca distance in FIG. 5). If the entire ridge stripe portion (width ab in FIG. 5) is included above the mask so as to exclude the III region, the laser oscillation lifetime is about 10,000 hours or more. It is possible to obtain a lifetime.
[0035]
Here, the region above the mask and excluding region III will be referred to as region I. This region I is a region in which a nitride semiconductor laser element having a longer laser oscillation lifetime than that of region II shown below can be manufactured.
[0036]
(When the ridge stripe part is made above the window part)
Next, the case where the ridge stripe part is formed above the window part will be described. The case where the ridge stripe portion is formed above the window portion can be described in the same manner as described above. When the ridge stripe portion of the nitride semiconductor laser element is fabricated in a region where the ca distance is larger than 10 μm and smaller than 14 μm, the laser oscillation lifetime of the nitride semiconductor laser element is dramatically reduced. . Here, considering that the ridge stripe width is 2 μm, 10 μm of the ca distance is converted into a distance from the window center d to the ridge stripe end b (hereinafter referred to as db distance). Then, the db distance becomes 1 μm. Similarly, when the distance c-a of 14 μm is converted into the distance from the window center d to the ridge stripe end a (hereinafter referred to as da), the distance da is 1 μm. That is, when the nitride semiconductor laser device is fabricated so that the ridge stripe portion of the nitride semiconductor laser element is included within a range of less than 1 μm on the left and right from the window center d along the width direction of the window portion, the laser oscillation lifetime is dramatically increased. It turns out that it decreases. The region where the laser oscillation lifetime is drastically reduced (the region less than 1 μm on the left and right from the window center d) will be referred to as region IV.
[0037]
Therefore, it is preferable that the ridge stripe portion of the nitride semiconductor laser device is manufactured so that the entire region of the ridge stripe portion (a-b width in FIG. 5) is included in the region excluding the region IV. Here, a region above the window portion and having a width of 1 μm or more from the window center d in the stripe direction of the window portion (corresponding to a region excluding the region IV) is referred to as a region II. To. Although the laser oscillation lifetime of the nitride semiconductor laser device fabricated in this region II is shorter than that fabricated in the aforementioned region I, it could have a laser oscillation lifetime of several thousand hours. The above results are summarized in the schematic diagram of FIG.
[0038]
FIG. 6 is a schematic diagram showing the region I to the region IV on the mask substrate with a film. The ridge stripe portion of the nitride semiconductor laser device fabricated on the film-coated mask substrate is most preferably included in the region I from the viewpoint of laser oscillation lifetime, and then the entire region is included in the region I and the region II. It is preferable that it is included in the region II, and it is preferable that the entire region is subsequently included in the region II. The reason why the longer laser oscillation lifetime, which is the subject of the present invention, differs depending on the position where the ridge stripe portion is formed, is probably because the crystal strain is relaxed differently in the mask substrate with a film. In addition, considering the above results, the nitride semiconductor film formed above the mask of the mask substrate is more likely to have crystal distortion in the nitride semiconductor film than that formed above the window of the mask substrate. It seems that the mitigation effect is large.
[0039]
According to the detailed examination by the present inventors, when the entire ridge stripe portion is formed so as to straddle the region I and the region II, in addition to the improvement of the laser oscillation lifetime, a crack occurs in the ridge stripe portion and the laser element It was preferable because it was possible to suppress a decrease in the yield rate.
[0040]
In the above-mentioned “About the optimum position where the current confinement portion of the nitride semiconductor laser device is manufactured”, the case where the ridge stripe width is 2 μm has been described. However, the case where other ridge stripe widths are used is also described above. A similar trend as in FIG. 5 can be observed.
[0041]
The relationship between the formation position of the ridge stripe portion and the laser oscillation lifetime shown above is not limited to the nitride semiconductor laser element (for example, FIG. 4A) having the ridge stripe structure. For example, in the case of a nitride semiconductor laser device having a current blocking layer, the ridge stripe portion described above corresponds to a portion sandwiched between two current blocking layers, and the ridge stripe width described above corresponds to the current blocking layer width (FIG. 4 ( see b)). In more general terms, if the current confinement portion of the nitride semiconductor laser element exists above the region I and / or the region II shown in FIG. 6, the effect of the present invention can be sufficiently obtained. It is done. Needless to say, the current confinement portion of the nitride semiconductor laser element may be formed so as to straddle region I and region II.
[0042]
(About mask width)
The mask width of the mask formed on the mask substrate is 5 μm or more and 30 μm or less, more preferably 9 μm or more and 25 μm or less. The lower limit value and the upper limit value of the mask width were estimated as follows.
[0043]
When the current confinement portion of the nitride semiconductor laser element is formed above the mask, the lower limit value of the mask width of the mask depends on the width (current confinement width) of the current confinement portion of the nitride semiconductor laser element. From the viewpoint of extending the lifetime of the laser oscillation described above, it is most preferable that the current confinement portion (for example, the ridge stripe portion) of the nitride semiconductor laser element is formed in the region I (see FIG. 6). Therefore, the lower limit value of the mask width needs to be wider than at least the current confinement width. Since the current confinement width can be formed with a width of about 1.5 μm to 3 μm, the lower limit value of the mask width is eventually 2 μm of the region III (the region III is less than 1 μm left and right from the mask center c toward the mask stripe direction). And the stripe width (1.5 μm) × 2 are estimated to be at least 5 μm or more. More preferably, the lower limit value of the mask width is a width of the region III of 6 μm (when the region III is a region less than 3 μm on the left and right sides of the mask center c in the mask stripe direction) and the stripe width (1.5 μm) × 2 is estimated to be 9 μm or more.
[0044]
On the other hand, the upper limit value of the mask width is not particularly limited. However, in order for the mask formed on the mask substrate to be completely covered with the nitride semiconductor film, the mask width needs to be 30 μm or less, more preferably 25 μm or less.
[0045]
The mask width is preferably wider than the window width of the window formed on the mask substrate. This is because many nitride semiconductor laser elements can be formed in the most preferable region I where the current confinement portion of the present invention can be formed. In addition, it is preferable because the element defect rate of the nitride semiconductor laser element is reduced.
[0046]
(About window width)
When the entire current confinement portion of the nitride semiconductor laser element is included above the window (produced in the region II), the lower limit value of the window width of the window is the same as the above-mentioned “Regarding the mask width” Is estimated to be 5 μm or more. On the other hand, when at least a part of the current confinement portion of the nitride semiconductor laser element is included above the mask, the lower limit value of the window width is 2 μm or more corresponding to the width of the region IV. There is no particular limitation on the upper limit of the window width. However, the wider the window width, the smaller the crystal strain relaxation effect, so the upper limit of the window width is 20 μm or less, more preferably 10 μm or less.
[0047]
(About mask stripe direction)
The stripe direction of the mask formed in a stripe shape will be described below. A stripe growth direction of a mask formed on a nitride semiconductor substrate having a {0001} C plane as a crystal growth surface, or a nitride semiconductor layer having a {0001} C plane as a crystal growth plane stacked on the nitride semiconductor substrate. The stripe direction of the mask was most preferably the <1-100> direction with respect to the nitride semiconductor substrate, followed by the <11-20> direction. Even if these directions had an opening angle of about ± 5 degrees in the {0001} C plane, the above relationship did not change.
[0048]
The advantage that the mask is formed along the <1-100> direction of the nitride semiconductor substrate is that the effect of suppressing crystal distortion and occurrence of cracks is very high. When the nitride semiconductor film was coated on the mask formed in such a direction, the nitride semiconductor film covered the mask while mainly forming a {11-20} facet surface on the mask. The {11-20} facet plane is perpendicular to the surface of the nitride semiconductor substrate, and the mask is formed of a growth suppressing film that is difficult to epitaxially grow. For this reason, a nitride semiconductor has grown from the {11-20} facet plane (see FIG. 7A). This growth is considered to have a very high effect of suppressing crystal distortion and crack generation because it grows in the horizontal direction with respect to the substrate surface (hereinafter referred to as lateral growth). Further, by using the configuration in which the stripe direction of the mask is the <1-100> direction and the optimum position of the current confinement portion of the present invention, it is possible to further improve the lifetime of the laser oscillation and to prevent defective elements due to crack suppression. The rate can be reduced.
[0049]
On the other hand, the advantage that the mask is formed along the <11-20> direction of the nitride semiconductor substrate is that the nitride located above the mask when the mask is filled with the nitride semiconductor film. The surface morphology of the semiconductor film is good. Further, when the hollow portion shown in FIG. 7B was viewed from above the substrate, it was covered with the nitride semiconductor film with almost no meandering. A nitride semiconductor having a current confinement portion formed in the region I of the present invention when the surface morphology of the nitride semiconductor film is good and the recess is covered with the nitride semiconductor film with almost no meandering The element failure rate of the element could be reduced. This is thought to be due to the following reasons. When the nitride semiconductor film is coated on the mask formed in such a direction, the nitride semiconductor film covers the mask while mainly forming a {1-101} facet surface on the mask. It was. The {1-101} facet plane was very flat, and the edge portion where the facet plane and the crystal growth plane were in contact was also very steep (FIG. 7B). This is considered to have contributed to the surface morphology of the nitride semiconductor film.
[0050]
The masks (or windows) described above are all striped, but the masks (or windows) are preferably striped in the following respects. The current confinement portion of the nitride semiconductor laser element is mainly in a stripe shape, and the optimum position (region I and / or region II) of the current confinement portion is also in a stripe shape. Therefore, it becomes easy to build the current confinement portion at the optimum position.
[0051]
(Nitride semiconductor film covering mask substrate)
In the configuration of the nitride semiconductor film covering the optimum position of the current confinement portion and the mask substrate of the present invention, the following effects can be obtained when the nitride semiconductor film is a GaN film, an AlGaN film, or an InGaN film. Here, the nitride semiconductor film may be doped with at least one of the impurity groups of Si, O, Cl, S, C, Ge, Zn, Cd, Mg, or Be.
[0052]
The nitride semiconductor film is preferably a GaN film in the following points. Since the GaN film is a binary mixed crystal, the control of crystal growth is good and the manufacturing method is easy. Further, since the surface migration length of GaN is longer than that of the AlGaN film and shorter than that of the InGaN film, an appropriate lateral growth can be obtained while covering the mask completely and flatly. When this lateral growth is promoted, crystal distortion in the nitride semiconductor film coated over the mask can be relaxed. The impurity concentration of the GaN film used as the nitride semiconductor film is 1 × 10 ¹⁷ / Cm ^Three 8 × 10 or more ¹⁸ / Cm ^Three The following is preferred. When an impurity is added in such a concentration range, the surface morphology of the nitride semiconductor film is improved, the thickness of the light emitting layer is made uniform, and the device characteristics can be improved.
[0053]
Next, the nitride semiconductor film is preferably an AlGaN film in the following points. When the AlGaN film covers the mask substrate, voids are hardly formed above the mask, and the occurrence rate of cracks is suppressed. In addition, the laser oscillation lifetime characteristics were improved. This is thought to be due to the following reasons.
[0054]
Since the AlGaN film contains Al in at least the nitride semiconductor film, the surface migration length is shorter than that of the GaN film or InGaN film. The short surface migration length means that the AlGaN film is easily attached to the mask as compared with other nitride semiconductor films not containing Al. This is considered to make it difficult to form voids above the mask and to suppress the generation of cracks from the voids. Further, since the surface migration length is short, the nitride semiconductor film is likely to grow from the side wall of the facet described with reference to FIG. 7, the lateral growth becomes more prominent, crystal distortion is relieved, and as a result, the laser It is thought that the oscillation lifetime characteristics have improved.
[0055]
Furthermore, when the AlGaN film was investigated, Al _x Ga _1-x The Al composition ratio x of the N film is preferably 0.01 or more and 0.15 or less, and more preferably 0.01 or more and 0.07 or less. If the Al composition ratio x is smaller than 0.01, it may be difficult to suppress the generation of voids. On the other hand, if the Al composition ratio x is greater than 0.15, the surface migration length described above may be too short (insufficient lateral growth), making it difficult to obtain a crystal strain relaxation effect above the mask. There is.
[0056]
The present invention is not limited to the AlGaN film, and effects similar to the above can be obtained as long as at least the nitride semiconductor film contains Al. The impurity concentration of the AlGaN film used as the nitride semiconductor film is 3 × 10. ¹⁷ / Cm ^Three 8 × 10 or more ¹⁸ / Cm ^Three The following is preferred. When impurities are added together with Al in such a concentration range, the surface migration length of the nitride semiconductor film is preferably shortened. This makes it possible to further reduce crystal distortion.
[0057]
Next, the nitride semiconductor film is preferably an InGaN film in the following points. When the InGaN film covers the mask substrate, the difference in laser oscillation lifetime is reduced due to the difference in the region (region I or region II) where the current confinement portion is formed. This reduced the element defect rate. This is thought to be due to the following reasons.
[0058]
Since the InGaN film contains In at least in the nitride semiconductor film, the InGaN film has elasticity compared to the GaN film and the AlGaN film. Therefore, the InGaN film can fill the mask and propagate crystal strain from the nitride semiconductor substrate to the entire nitride semiconductor film. This is considered to work to alleviate the difference between the crystal strain above the mask and the crystal strain above the window.
[0059]
Further, when the InGaN film was investigated, In _x Ga _1-x The In composition ratio x of the N film is preferably 0.01 or more and 0.18 or less, more preferably 0.01 or more and 0.1 or less. If the In composition ratio x is smaller than 0.01, it may be difficult to obtain the effect of elastic force due to the inclusion of In. Further, if the In composition ratio x is larger than 0.18, the crystallinity of the InGaN film may be lowered.
[0060]
The present invention is not limited to an InGaN film, and effects similar to those described above can be obtained if at least a nitride semiconductor film contains In. The impurity concentration of the InGaN film used as the nitride semiconductor film is 1 × 10 ¹⁷ / Cm ^Three 4 × 10 or more ¹⁸ / Cm ^Three The following is preferred. It is preferable to add an impurity together with In in such a concentration range because the surface morphology of the nitride semiconductor film is good and elasticity can be retained.
[0061]
(About film thickness of nitride semiconductor film covering mask substrate)
In order for the mask substrate to be completely covered with the nitride semiconductor film, the thickness of the nitride semiconductor film covering the mask substrate is preferably about 2 μm to 30 μm. Here, the coating thickness is defined as the thickness of the nitride semiconductor film when the nitride semiconductor film is directly grown on a flat nitride semiconductor substrate. If the coating thickness is less than 2 μm, it will be difficult to completely and evenly cover the mask substrate with a nitride semiconductor film, although it depends on the mask width and window width formed on the mask substrate. obtain. On the other hand, when the coating film thickness is greater than 30 μm, the growth in the vertical direction (perpendicular to the substrate surface) gradually becomes stronger than the lateral growth by the mask substrate, and the crystal strain relaxation effect is sufficiently enhanced. It becomes difficult to be demonstrated.
[0062]
(Embodiment 2)
In the second embodiment, a method for manufacturing a nitride semiconductor laser device having a ridge stripe structure manufactured on a mask substrate with a film will be described. Here, the mask substrate with a film is a substrate in which a nitride semiconductor film is coated on the mask substrate as defined above. Other matters relating to the present invention are the same as those in the first embodiment.
[0063]
(Method for producing mask substrate with film)
A method for manufacturing a mask substrate with a film will be described with reference to FIGS. The schematic diagram of FIG. 3 shows a mask substrate composed of a mask 200 fabricated on a GaN substrate 101 (an example of a nitride semiconductor substrate), and n-type Al on the mask substrate. _0.03 Ga _0.97 The figure shows a mask substrate with a film coated with an N film 102 (an example of a nitride semiconductor film).
[0064]
First, the mask substrate is manufactured as follows. On the surface of the GaN substrate 101 whose plane direction is the (0001) plane, ₂ A growth inhibiting film composed of the following was deposited with a thickness of 0.1 μm. The growth suppressing film was deposited by an electron beam deposition method (EB method) or a sputtering method. Thereafter, a stripe-shaped mask 200 was formed along the <1-100> direction of the GaN substrate 101 using a conventional lithography technique. The striped mask 200 was formed with a mask width of 13 μm and a window width of 7 μm. In this way, the mask substrate of the second embodiment was completed.
[0065]
Next, the mask substrate was sufficiently organically cleaned and transferred to an MOCVD (metal organic chemical vapor deposition) apparatus. Then, the group V raw material NH is formed on the mask substrate under the condition of a growth temperature of 1050 ° C. _Three (Ammonia), Group III raw material TMGa (trimethylgallium) and Group III raw material TMAl (trimethylaluminum) are supplied. _Four (Si impurity concentration 1 × 10 ¹⁸ / Cm ^Three N-type Al with a thickness of 15 μm _0.03 Ga _0.97 An N film 102 (an example of a nitride semiconductor film) was stacked. Thus, the film-coated mask substrate 100 of the second embodiment was completed (FIG. 3).
[0066]
The growth suppression film described above is SiO. ₂ Besides SiN _x , Al ₂ O _Three TiO ₂ , Tungsten or molybdenum may be used.
[0067]
The stripe direction of the stripe-shaped mask described above is formed along the <1-100> direction with respect to the GaN substrate 101 (an example of a nitride semiconductor substrate), but <11 with respect to the GaN substrate 101. It may be formed along the −20> direction.
[0068]
As the nitride semiconductor substrate described above, the GaN substrate 101 having the (0001) plane is used, but other plane orientations and other nitride semiconductor substrates may be used. As for the plane orientation of the nitride semiconductor substrate, the C plane {0001}, A plane {11-20}, R plane {1-102}, M plane {1-100}, {1-101} plane, etc. should be used. Is preferred. In addition, the surface morphology is good if the substrate has an off angle within 2 degrees from the plane orientation. Further, as another nitride semiconductor substrate, for example, in the case of a nitride semiconductor laser, a layer having a refractive index lower than that of the cladding layer is in contact with the outside of the cladding layer in order to make the vertical transverse mode unimodal. And an AlGaN substrate is preferably used.
[0069]
(Crystal Growth Method for Nitride Semiconductor Laser Device Having Ridge Stripe Structure) Next, the nitride semiconductor laser device manufactured on the mask substrate with the film is “crystal growth method for nitride semiconductor laser device having a ridge stripe structure”. The “process steps” and the “package mounting” will be described in order.
[0070]
FIG. 1 shows a nitride semiconductor laser device chip after the nitride semiconductor laser device grown on the film-coated mask substrate is divided into chips.
[0071]
1 includes a mask substrate 100 with a film, an n-type In _0.07 Ga _0.93 N crack prevention layer 103, n-type Al _0.1 Ga _0.9 N-clad layer 104, n-type GaN light guide layer 105, light-emitting layer 106, p-type Al _0.2 Ga _0.8 N carrier block layer 107, p-type GaN light guide layer 108, p-type Al _0.1 Ga _0.9 N clad layer 109, p-type GaN contact layer 110, n-electrode 111, p-electrode 112, SiO ₂ It consists of a dielectric film 113 and an n-type electrode pad 114. However, the film-coated mask substrate 100 includes a GaN substrate 101, a mask 200, and an n-type Al. _0.03 Ga _0.97 An N film 102 is used.
[0072]
Hereinafter, a method for manufacturing a nitride semiconductor laser device will be described in detail. Using a MOCVD apparatus, the film-coated mask substrate 100 is coated with NH as a group V raw material. _Three TMGa or group III raw material TMGa or TEGa (triethylgallium), TMIn (trimethylindium) group III raw material and SiH _Four N-type In at a growth temperature of 800 ° C. _0.07 Ga _0.93 The N crack prevention layer 103 was grown to 40 nm. Next, the substrate temperature is raised to 1050 ° C., and a group III raw material of TMAl or TEAl (triethylaluminum) is used to form an n-type Al having a thickness of 1.2 μm. _0.1 Ga _0.9 N clad layer 104 (Si impurity concentration 1 × 10 ¹⁸ / Cm ^Three ) Is grown, followed by n-type GaN light guide layer 105 (Si impurity concentration 1 × 10 ¹⁸ / Cm ^Three ) Was grown to 0.1 μm.
[0073]
After that, the substrate temperature was lowered to 800 ° C., and 3 cycles of 4 nm thick In _0.15 Ga _0.85 N well layer and 8nm thick In _0.01 Ga _0.99 A light emitting layer (multiple quantum well structure) 106 composed of an N barrier layer was grown in the order of barrier layer / well layer / barrier layer / well layer / barrier layer / well layer / barrier layer. At that time, SiH is formed on both the barrier layer and the well layer. _Four (Si impurity concentration is 1 × 10 ¹⁸ / Cm ^Three ) Was added. A growth interruption between 1 second and 180 seconds may be performed between the barrier layer and the well layer or between the well layer and the barrier layer. This is preferable because the flatness of each layer is improved and the half width of light emission is reduced.
[0074]
When As is added to the light emitting layer, AsH _Three (Arsine) or TBAs (tertiary butyl arsine), PH when P is added to the light emitting layer _Three (Phosphine) or TBP (tertiarybutylphosphine), and when Sb is added to the light emitting layer, TMSb (trimethylantimony) or TESb (triethylantimony) is preferably added. Further, when the light emitting layer is formed, NH is used as an N raw material. _Three Besides N ₂ H _Four (Dimethylhydrazine) may be used.
[0075]
Next, the substrate temperature was raised again to 1050 ° C., and p-type Al having a thickness of 20 nm. _0.2 Ga _0.8 N carrier block layer 107, 0.1 μm p-type GaN light guide layer 108, 0.5 μm p-type Al _0.1 Ga _0.9 An N clad layer 109 and a 0.1 μm p-type GaN contact layer 110 were sequentially grown. Mg (EtCP) as the p-type impurity ₂ Mg: bisethylcyclopentadienylmagnesium) is 5 × 10 ¹⁹ / Cm ^Three ~ 2x10 ²⁰ / Cm ^Three Added at. The p-type impurity concentration of the p-type GaN contact layer 110 is preferably increased in the direction of the p-electrode 112. This reduces the contact resistance due to p-electrode formation. Further, a small amount of oxygen may be mixed during the growth of the p-type layer in order to remove residual hydrogen in the p-type layer that hinders the activation of Mg, which is a p-type impurity.
[0076]
After the p-type GaN contact layer 110 is grown in this way, the reactor inside the MOCVD apparatus contains all nitrogen carrier gas and NH. _Three The temperature was reduced at 60 ° C./min. When the substrate temperature reaches 800 ° C., NH _Three Was stopped at the substrate temperature for 5 minutes and then lowered to room temperature. The holding temperature of the substrate is preferably between 650 ° C. and 900 ° C., and the standby time is preferably 3 minutes or more and 10 minutes or less. Further, the rate of arrival of the temperature drop is preferably 30 ° C./min or more. As a result of the evaluation of the grown film thus prepared by Raman measurement, the above-described technique has already shown p-type characteristics after growth even when conventional p-type annealing is not performed (Mg). Was activated). In addition, the contact resistance due to the formation of the p electrode has also been reduced. In addition to the above, if the conventional p-type annealing was combined, it was preferable because the Mg activation rate was further improved.
[0077]
In described above _0.07 Ga _0.93 The N crack prevention layer 103 may have an In composition ratio other than 0.07, or may not have the InGaN crack prevention layer itself. However, when the lattice mismatch between the cladding layer and the GaN substrate becomes large, it is more preferable in terms of prevention of cracks to insert the InGaN crack prevention layer.
[0078]
The light-emitting layer 106 described above has a configuration that starts with a barrier layer and ends with a barrier layer, but may have a configuration that starts with a well layer and ends with a well layer. Further, the number of well layers is not limited to the above-described three layers, and if it is 10 layers or less, the threshold current density is low, and continuous oscillation at room temperature is possible. In particular, when the number of layers is 2 or more and 6 or less, the threshold current density is preferably low. Further, the light emitting layer described above may contain Al.
[0079]
The light emitting layer 106 described above includes Si (SiH) in both the well layer and the barrier layer. _Four ) Is 1 × 10 ¹⁸ / Cm ^Three Although added, Si may not be added. However, the emission intensity was stronger when Si was added to the light emitting layer. As the impurity added to the light emitting layer, at least one of the impurity groups of O, C, Ge, Zn, or Mg may be added in addition to the Si. The total amount of the impurity group added is about 1 × 10. ¹⁷ ~ 8x10 ¹⁸ / Cm ^Three The degree was favorable. Furthermore, the layer to which the impurity is added is not limited to both the well layer and the barrier layer, and the impurity may be added to only one of the layers.
[0080]
P-type Al described above _0.2 Ga _0.8 The N carrier block layer 107 may have an Al composition ratio other than 0.2, or the carrier block layer itself may not be present. However, the threshold current density was lower when the carrier block layer was provided. This is because the carrier block layer has a function of confining carriers in the light emitting layer. Increasing the Al composition ratio of the carrier block layer is preferable because carrier confinement is strengthened. Further, it is preferable to reduce the Al composition ratio to such an extent that carrier confinement is maintained, because the carrier mobility in the carrier block layer increases and the electrical resistance decreases.
[0081]
In the above description, as the p-type cladding layer and the n-type cladding layer, Al _0.1 Ga _0.9 An N crystal is used, but an AlGaN ternary crystal having an Al composition ratio other than 0.1 may be used. When the mixed crystal ratio of Al increases, the energy gap difference and the refractive index difference with the light emitting layer increase, carriers and light are efficiently confined in the light emitting layer, and the laser oscillation threshold current density is reduced. Further, if the Al composition ratio is reduced to such an extent that the confinement of carriers and light is maintained, the carrier mobility in the cladding layer increases, and the operating voltage of the device can be lowered.
[0082]
The thickness of the AlGaN clad layer described above is preferably 0.7 μm to 1.5 μm. As a result, the unimodal vertical transverse mode and the light confinement efficiency are increased, so that the optical characteristics of the laser can be improved and the laser threshold current density can be reduced.
[0083]
The cladding layer described above is an AlGaN ternary mixed crystal, but may be a quaternary mixed crystal such as AlInGaN, AlGaNP, and AlGaNAs. Furthermore, the p-type cladding layer has a superlattice structure composed of a p-type AlGaN layer and a p-type GaN layer or a superlattice structure composed of a p-type AlGaN layer and a p-type InGaN layer in order to reduce electrical resistance. You may do it.
[0084]
In the above description, the crystal growth method using the MOCVD apparatus has been described. However, molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE) may be used.
[0085]
(Process process)
Subsequently, a description will be given of the process steps for removing the epi-wafer produced by the above-mentioned “crystal growth method of nitride semiconductor laser element having ridge stripe structure” from the MOCVD apparatus and processing it into a nitride semiconductor laser element chip. . Here, the surface of the epi-wafer after the fabrication of the nitride semiconductor laser device was flat, and the mask and window formed on the mask substrate were completely buried with the nitride semiconductor film and the light-emitting device structure.
[0086]
The n-type electrode 111 is formed from the front side of the epi-wafer by using a dry etching method. _0.03 Ga _0.97 After the N film 102 was exposed, it was formed in the order of Hf / Al. Then, Au was deposited as an n-type electrode pad 114 on the n-electrode 111. In addition to the n-electrode material, Ti / Al, Ti / Mo, Hf / Au, or the like may be used. It is preferable to use Hf for the n electrode because the contact resistance of the n electrode is lowered. Since the mask substrate is composed of a nitride semiconductor substrate, an n-electrode may be formed from the back side of the mask substrate (see FIG. 8). However, the nitride semiconductor substrate needs to be doped with impurities so as to have n-type polarity.
[0087]
The p-electrode portion was etched in a stripe shape along the same direction as the stripe direction of the mask to form a ridge stripe portion (FIG. 1). The ridge stripe portion was formed so as to exclude the region III at a position 4 μm away from the center of the mask. The ridge stripe portion had a width of 1.7 μm. Then SiO ₂ A dielectric film 113 was deposited, the p-type GaN contact layer 110 was exposed, and a p-electrode 112 was deposited in the order of Pd / Mo / Au. In addition to the p-electrode material, any of Pd / Pt / Au, Pd / Au, or Ni / Au may be used.
[0088]
Finally, the epi-wafer was cleaved in a direction perpendicular to the ridge stripe direction to produce a Fabry-Perot resonator having a resonator length of 500 μm. The resonator length is generally preferably 300 μm to 1000 μm. The cavity facet of the nitride semiconductor laser element in which the stripe direction of the mask is formed along the <1-100> direction is the M plane ({1-100} plane) of the nitride semiconductor crystal. The cleavage for forming the cavity end face and the chip division of the nitride semiconductor laser element were performed by a scriber from the back side of the mask substrate. However, the cleavage was not performed after the scriber was scratched on the entire surface of the wafer, but was cleaved by the scriber only on a part of the wafer, for example, both ends of the wafer. . As a result, the yield is improved because the sharpness of the end face of the resonator and the scrap due to scribing do not adhere to the epi surface. In addition to the laser resonator feedback method, a generally known DFB (Distributed Feedback) or DBR (Distributed Bragg Reflector) may be used. After the resonator end face of the Fabry-Perot resonator is formed, SiO having a reflectivity of 70% is formed on the end face. ₂ And TiO ₂ The dielectric films were alternately deposited to form a dielectric multilayer reflective film. In addition to the dielectric material, SiO ₂ / Al ₂ O _Three May be used as a dielectric multilayer reflective film. The nitride semiconductor laser device chip shown in FIG. 1 was produced as described above.
[0089]
(Package mounting)
Next, a method for mounting the semiconductor laser element chip on a package will be described. High power (30 mW or more) nitride semiconductor laser device chips must pay attention to heat dissipation measures. For example, the high-power nitride semiconductor laser element chip is preferably connected to the package body by junction down using an In solder material. In addition, the high-power nitride semiconductor laser device chip is not directly attached to the package body or the heat sink, but is a sub-substance of any one of Si, AlN, diamond, Mo, CuW, BN, Fe, Cu, SiC, or Au. It may be connected via a mount.
[0090]
As a result, the current confinement portion of the nitride semiconductor laser element was produced at the optimum position of the present invention, and a laser oscillation lifetime of about 13000 hours was achieved under conditions of a laser output of 30 mW and an ambient temperature of 60 ° C.
[0091]
The formation position, mask width, and window width of the ridge stripe portion described in the second embodiment may be manufactured with other numerical values as long as the conditions described in the first embodiment are satisfied. Absent.
[0092]
(Embodiment 3)
In the third embodiment, the nitride semiconductor laser element having the ridge stripe structure described in the second embodiment is replaced with a nitride semiconductor laser element having a current blocking layer (FIG. 4B). This is the same as the first embodiment or the second embodiment.
[0093]
A nitride semiconductor laser device having a current blocking layer will be described below with reference to FIG.
[0094]
FIG. 9 shows a mask substrate 100 with a film, n-type In _0.07 Ga _0.93 N crack prevention layer 103, n-type Al _0.1 Ga _0.9 N-clad layer 104, n-type GaN light guide layer 105, light-emitting layer 106, p-type Al _0.2 Ga _0.8 N carrier block layer 107, p-type GaN light guide layer 108, p-type Al _0.1 Ga _0.9 N first cladding layer 109a, current blocking layer 120, p-type Al _0.1 Ga _0.9 The N second cladding layer 109b, the p-type GaN contact layer 110, the n-electrode 111, and the p-electrode 112 are included.
[0095]
The current blocking layer 120 may be a layer that blocks current so that the current injected from the p-type electrode 112 can pass only through the width of the current blocking layer shown in FIG. For example, as the current blocking layer 120, n-type Al _0.25 Ga _0.75 An N layer may be used. The Al composition ratio of the current blocking layer is not limited to 0.25, and other values may be used.
[0096]
In the third embodiment, the mask formed on the mask substrate is 10 μm wide, the window is 5 μm wide, the mask is 0.1 μm thick, and the current blocking interlayer width is 1.8 μm. Also, one end of the portion sandwiched between the two current blocking layers 120 is formed at a position 3 μm away from the center of the mask, and the portion sandwiched between the two current blocking layers 120 does not include the upper portion of the mask center. (Position corresponding to region I of the present invention).
[0097]
(Embodiment 4)
The fourth embodiment is the same as any one of the first to third embodiments except that a mask is formed on the nitride semiconductor layer stacked on the nitride semiconductor substrate.
A method for manufacturing a film-coated mask substrate according to the fourth embodiment will be described below.
[0098]
First, a GaN substrate (an example of a nitride semiconductor substrate) having a (0001) plane orientation was loaded into the MOCVD apparatus. And at a growth temperature of 550 ° C., NH _Three And TMGa were supplied to the GaN substrate to form a low-temperature GaN buffer layer. Next, the growth temperature is raised to 1050 ° C. and NH _Three , TMGa and SiH _Four Was supplied, and an n-type GaN layer (an example of a nitride semiconductor layer) was formed on the low-temperature GaN buffer layer. After the n-type GaN layer was formed, the substrate was taken out from the MOCVD apparatus.
[0099]
Subsequently, on the surface of the n-type GaN layer of the substrate taken out from the MOCVD apparatus, SiN _x A growth inhibiting film composed of the following was deposited with a thickness of 0.15 μm. SiN _x Was deposited by sputtering. Thereafter, using conventional lithography technology, stripe-like SiN is formed along the <1-100> direction of the GaN substrate. _x The mask was formed. The mask was formed with a mask width of 8 μm and a window width of 2 μm. In this way, the mask substrate according to the fourth embodiment was completed.
[0100]
Next, the mask substrate was sufficiently organically cleaned and transferred to an MOCVD (metal organic chemical vapor deposition) apparatus. Then, the group V raw material NH is formed on the mask substrate under the condition of a growth temperature of 1050 ° C. _Three Group III raw materials TMGa and SiH _Four (Si impurity concentration 1 × 10 ¹⁸ / Cm ^Three ), And a GaN film (an example of a nitride semiconductor film) having a thickness of 20 μm was laminated. Thus, the film-coated mask substrate according to the fourth embodiment was completed.
[0101]
The low-temperature GaN buffer layer described in the fourth embodiment is made of low-temperature Al. _x Ga _1-x The N buffer layer (0 ≦ x ≦ 1) may be used, and the low temperature buffer layer itself may not be formed. However, currently supplied GaN substrates have unfavorable surface morphology, so low temperature Al _x Ga _1-x It is preferable that the N buffer layer (0 ≦ x ≦ 1) is inserted because the surface morphology is improved. Here, the low temperature buffer layer refers to a buffer layer formed at a growth temperature of about 450 ° C. to 600 ° C. The buffer layer manufactured in these growth temperature ranges is polycrystalline or amorphous.
[0102]
The mask width and the window width formed on the mask substrate described in the fourth embodiment may be manufactured with other numerical values as long as the conditions described in the first embodiment are satisfied.
[0103]
Other matters relating to the method of manufacturing the film-coated mask substrate of the fourth embodiment are the same as those of the first embodiment.
[0104]
(Embodiment 5)
In the fifth embodiment, any one of the first to fourth embodiments described above except that at least one element of the element group of As, P, or Sb is contained in the light emitting layer of the nitride semiconductor laser element. It is the same.
[0105]
In the present invention, at least one element of the element group of As, P, or Sb is contained in at least the well layer in the light emitting layer constituting the nitride semiconductor light emitting laser element. At this time, when the total composition ratio of the element group contained in the well layer is X and the N element composition ratio of the well layer is Y, X is smaller than Y and X / (X + Y) is 0.3 (30%) or less, preferably 0.2 (20%) or less. The lower limit of the sum of the element groups is 1 × 10 ¹⁸ / Cm ^Three That's it. When the total composition ratio X of the element groups becomes higher than 20%, concentration separation with different composition ratios of the elements gradually starts to occur for each region in the well layer. Further, when the total composition ratio X of the element groups becomes higher than 30%, this time, the concentration separation starts to shift to the crystal separation in which a hexagonal system and a cubic system are mixed, and the crystallinity of the well layer starts to deteriorate. On the other hand, the total addition amount of the element group is 1 × 10 ¹⁸ / Cm ^Three When it becomes smaller than this, the effect by containing the said element in a well layer becomes difficult to be acquired.
[0106]
The effect of the fifth embodiment is that the effective mass of electrons and holes in the well layer is small by containing at least one element of the element group in the well layer. Increases mobility. In the case of a semiconductor laser device, the former means that a carrier inversion distribution for laser oscillation can be obtained with a small amount of current injection, and the latter means that even if electrons and holes disappear in the light emitting layer due to light emission recombination, It means that holes are injected at high speed by diffusion. That is, the nitride semiconductor laser device of the present invention has a threshold current density higher than that of the currently reported InGaN-based nitride semiconductor laser device that does not contain any element group of As, P, or Sb in the light emitting layer. It is possible to manufacture a semiconductor laser that is low and has excellent self-oscillation characteristics (excellent noise characteristics).
[0107]
(Embodiment 6)
In the sixth embodiment, a case where the nitride semiconductor laser element according to the present invention is applied to a semiconductor optical device will be described.
[0108]
The blue-violet (oscillation wavelength of 380 to 420 nm) nitride semiconductor laser element according to the present invention is preferable in the following points when used in a semiconductor optical device, for example, an optical pickup device. The nitride semiconductor laser device operates stably in a high output (30 mW), high temperature atmosphere (60 ° C.), and has a long laser oscillation life. It is most suitable for the device (the shorter the oscillation wavelength, the higher the recording / reproduction is possible).
[0109]
FIG. 10 shows a schematic diagram of an optical disk apparatus (an apparatus having an optical pickup, such as a DVD apparatus) as an example in which the nitride semiconductor laser element of the present invention is used in a semiconductor optical apparatus. The laser light in FIG. 10 is modulated by an optical modulator in accordance with input information and recorded on a disk through a lens. At the time of reproduction, the laser beam optically changed by the pit arrangement on the disc is detected by the photodetector through the splitter and becomes a reproduction signal. These operations are controlled by a control circuit. The laser output is normally about 30 mW during recording and about 5 mW during reproduction.
[0110]
The present invention can be used for, for example, a laser printer, a bar code reader, a projector using three primary colors of light (blue, green, red) laser in addition to the optical disk device having the optical pickup device.
[0111]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. 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.
[0112]
【The invention's effect】
According to the present invention, a nitride semiconductor laser element having a long laser oscillation lifetime and a semiconductor optical device using the nitride semiconductor laser element can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a state in which a nitride semiconductor film is coated on a mask substrate (n electrode and p electrode are arranged in the same direction).
2A and 2B are schematic views showing an example of a mask substrate, in which FIG. 2A shows a cross section of an example of a mask substrate, and FIG. 2B shows an upper surface of an example of a mask substrate.
FIG. 3 is an example of a mask substrate with a film.
FIG. 4 is a schematic diagram of a nitride semiconductor laser structure, in which (a) is an example of a nitride semiconductor laser element having a ridge stripe structure, and (b) is a diagram of a nitride semiconductor laser element having a current blocking layer. It is an example.
FIG. 5 is a diagram showing a relationship between a position where a ridge stripe portion is formed and a laser oscillation lifetime of a nitride semiconductor laser device fabricated on a film-coated mask substrate.
FIG. 6 is a schematic view showing a preferable manufacturing region in which a current confinement portion of a nitride semiconductor laser element can be formed on a film-coated mask substrate.
FIG. 7 is a view showing a state where a nitride semiconductor film is coated on a mask substrate, in which (a) shows a state in which a nitride semiconductor grows from a {11-20} facet plane; ) Is a view showing a state in which a hollow portion is covered with a nitride semiconductor film.
FIG. 8 is a nitride semiconductor laser device chip having a ridge stripe portion (n electrode and p electrode are arranged at positions facing each other).
FIG. 9 is an example of a nitride semiconductor laser element chip having a current blocking layer.
FIG. 10 shows an example of a semiconductor optical device using the present invention (optical pickup device).
[Explanation of symbols]
100 Mask substrate with film, 101 GaN substrate, 102 n-type Al _0.03 Ga _0.97 N film, 103 n-type In _0.07 Ga _0.93 N crack prevention layer, 104 n-type Al _0.1 Ga _0.9 N clad layer, 105 n-type GaN light guide layer, 106 light emitting layer, 107 p-type Al _0.2 Ga _0.8 N carrier block layer, 108 p-type GaN light guide layer, 109 p-type Al _0.1 Ga _0.9 N clad layer, 110 p-type GaN contact layer, 111 n electrode, 112 p electrode, 113 SiO ₂ Dielectric film, 114 n-type electrode pad, 120 current blocking layer, 200 mask.

Claims (8)

Have nitride stripe mask before Symbol mask configured nitride stacked on the semiconductor substrate a semiconductor layer or Oite nitride semiconductor nitride semiconductor substrate from the growth inhibiting film is suppressed epitaxial growth is formed There is a mask substrate having no striped window,
The width of the window is set to 5 μm or more and 20 μm or less,
A nitride semiconductor film covering the mask substrate;
A light emitting device structure having a light-emitting layer comprising at least an n-type layer and the p-type layer and the well layer sandwiched by or well and barrier layers are provided are sequentially grown on the mask substrate,
Are current confinement portion of the light emitting device structure comprising a top region and from the middle of the width of toward the stripe direction of the window portion said window portion 1μm or more areas to the right and left front Kimado portion produced Tei Rukoto A nitride semiconductor laser device characterized by the above. The nitride semiconductor laser device according to claim 1, wherein the width of the mask is 5 μm or more and 30 μm or less. The nitride semiconductor laser device according to claim 1 or 2 width of the mask is equal to or wider than the window width. The nitride semiconductor film at least _{A x Ga 1-x N (} Al composition ratio x is 0.01 to 0.15) nitride according to any one of claims 1 to 3, which comprises a semiconductor Laser element. The nitride semiconductor laser according to any one of claims 1 to 3 wherein the nitride semiconductor film, characterized in that the _{In x Ga 1-x N (} In composition ratio x is 0.01 or more 0.18 or less) containing element. As, at least one element selected from the element group consisting of P or Sb is, the nitride semiconductor laser device according to any one of claims 1 5, characterized in Tei Rukoto be contained in the well layer. The nitride semiconductor laser device according to any of claims 1 to 6, characterized in that the n-type electrode on the back side of the mask substrate is formed. The semiconductor optical device comprising any Kano nitride semiconductor laser device of claims 1 7.

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