JP2021027086A - Surface light emitting laser, surface light emitting laser device, light source device, and detection device - Google Patents

Abstract

To provide a rear reflection type surface light emitting laser that can emit light from a resonator mirror surface on the opposite side of an emission side, a surface light emitting laser device, a light source device, and a detection device.SOLUTION: A surface light emitting laser has a substrate, a first surface light emitting laser element that is formed on the substrate and emits first light, and a second surface light emitting laser element that is formed on the substrate and emits second light. The first surface light emitting laser element includes, in order from a substrate side, a first lower reflection mirror, a first active layer, and a first upper reflection mirror. The second surface light emitting laser element includes, in order from the substrate side, a second lower reflection mirror, a second active layer, and a second upper reflection mirror. The reflectance of the second upper reflection mirror is smaller than the reflectance of the first upper reflection mirror. The first light is output from the substrate side, and the second light is output from the second upper reflection mirror side.SELECTED DRAWING: Figure 2

Description

The present invention relates to a surface emitting laser, a surface emitting laser device, a light source device, and a detection device.

A vertical cavity surface emitting laser (VCSEL) is a semiconductor laser that oscillates laser light in a direction perpendicular to a substrate. The surface emitting laser is superior to the end surface emitting type semiconductor laser that irradiates light in a direction parallel to the substrate, such as low threshold current oscillation, single longitudinal mode oscillation, and two-dimensional array. Has the characteristics.

The surface emitting laser includes a surface emitting laser that emits laser light to the side where the active layer of the substrate is provided and a back surface that emits laser light to the side opposite to the side where the active layer of the substrate is provided. There is an emission type surface emitting laser. In the back-emission type surface-emitting laser, a laminate including an active layer is formed on a semiconductor substrate, and light is emitted from the substrate side (Patent Document 1).

So far, there has been no technical idea of emitting light from the resonator mirror surface on the opposite side of the emission side in the back emission type surface emitting laser.

An object of the present invention is to provide a back surface reflection type surface emitting laser, a surface emitting laser device, a light source device, and a detection device capable of emitting light from a resonator mirror surface on the opposite side to the emitting side.

According to one aspect of the disclosed technique, the surface emitting laser is formed on a substrate, a first surface emitting laser element formed on the substrate and outputting a first light, and a second surface emitting laser element formed on the substrate. The first surface emitting laser element has a second surface emitting laser element for outputting the light of the above, and the first surface emitting laser element has a first lower reflecting mirror, a first active layer, and a first surface emitting laser element in order from the substrate side. The second surface emitting laser element includes an upper reflecting mirror, and the second surface emitting laser element includes a second lower reflecting mirror, a second active layer, and a second upper reflecting mirror in order from the substrate side, and the second upper reflecting mirror is provided. The reflectance of the mirror is smaller than the reflectance of the first upper reflector, the first light is output from the substrate side, and the second light is output from the second upper reflector side. Laser.

According to the disclosed technique, in the back surface reflection type surface emitting laser, it is possible to provide a surface emitting laser that emits light from a resonator mirror surface on the side opposite to the emitting side.

It is a figure which shows the layout of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 1) which shows the internal structure of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 2) which shows the internal structure of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 3) which shows the internal structure of the surface emitting laser which concerns on embodiment. It is a schematic diagram which shows the use example of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 1) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 2) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 3) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 4) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 5) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (the 6) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (7) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (8) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (9) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (10) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (11) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (12) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (13) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (14) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is sectional drawing (15) which shows the manufacturing method of the surface emitting laser which concerns on embodiment. It is a figure which shows the example of the planar shape of a dielectric multilayer film reflector. It is a figure which shows the outline of the ranging device as an example of a detection device.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration may be designated by the same reference numerals to omit duplicate explanations. In the following description, the laser oscillation direction (the emission direction of the laser beam) is defined as the Z-axis direction, and the two directions orthogonal to each other in the plane perpendicular to the Z-axis direction in the right-handed system are defined as the X-axis direction and the Y-axis direction. In addition, the positive Z-axis direction is downward. In the present disclosure, the plan view means the view from the Z-axis direction, that is, the direction perpendicular to the substrate. However, the surface emitting laser element or the like can be used in an upside-down state, and can be arranged at an arbitrary angle.

(First Embodiment)
First, the first embodiment will be described. The first embodiment relates to a surface emitting laser including a back surface emitting type surface emitting laser element.

[Basic structure of surface emitting laser]
FIG. 1 is a diagram showing a layout of a surface emitting laser according to an embodiment. 2 to 4 are cross-sectional views showing the internal structure of the surface emitting laser according to the embodiment. FIG. 2 corresponds to a cross-sectional view taken along the line I-I in FIG. FIG. 3 corresponds to a cross-sectional view taken along line II-II in FIG. FIG. 4 corresponds to a cross-sectional view taken along the line III-III in FIG.

As shown in FIG. 1, the surface emitting laser 100 according to the embodiment has, for example, nine surface emitting laser elements 151. The nine surface emitting laser elements 151 are arranged three by three in the X-axis direction and three in the Y-axis direction to form the laser element array 153. The surface emitting laser element 151 includes, for example, one surface emitting laser element 152. For example, the surface emitting laser element 152 is arranged outside the laser element array 153. As shown in FIG. 2, the surface emitting laser element 151 emits laser light LA toward the back surface 101A of the substrate 101. As shown in FIG. 3, the surface emitting laser element 152 emits laser light LA to the back surface 101A side of the substrate 101, and outputs spontaneous emission light or laser light LB to the front surface 101B side (−Z side) of the substrate 101. To do. The number of surface emitting laser elements 151 and the number of surface emitting laser elements 152 included in the laser element array 153 are not limited. The surface emitting laser element 151 is an example of the first surface emitting laser element. The surface emitting laser element 152 is an example of the second surface emitting laser element.

A p-side contact region 155 for connecting the p-side electrode 112 to the electrode of the mounting substrate is provided in the vicinity of the surface emitting laser element 152. Further, n-side contact regions 156 for connecting the n-side electrodes 113 to the electrodes of the mounting substrate are provided at a plurality of locations, for example, four locations around the laser element array 153. The number of n-side contact regions 156 is not limited.

The surface emitting laser 100 is a surface emitting laser having an oscillation wavelength in the 940 nm band. As shown in FIGS. 2 to 4, the surface emitting laser 100 includes a substrate 101, a lower semiconductor multilayer film reflector 102, a lower spacer layer 103, an active layer 104, an upper spacer layer 105, and an upper semiconductor multilayer film. It has a reflecting mirror 106, an insulating film 111, a p-side electrode 112, an n-side electrode 113, a dielectric multilayer film reflecting mirror 114, and an antireflection film 115.

As an example, the normal direction of the mirror-polished surface (main surface) of the surface of the substrate 101 is 15 degrees (θ = 15 degrees) in the crystal orientation [111] A direction with respect to the crystal orientation [100] direction. It is an inclined n-GaAs single crystal semiconductor substrate. That is, the substrate 101 is a so-called inclined substrate. The substrate is not limited to the above.

The lower semiconductor multilayer film reflector 102 is laminated on the −Z side (upper side) of the substrate 101 via a buffer layer (not shown), and has a low refractive index layer composed of _{n—Al 0.9} Ga _{0.1 As.} It has about 26 pairs with a high refractive index layer made of n—Al _0.1 Ga _{0.9 As.} In order to reduce the electrical resistance, a composition gradient layer (not shown) having a thickness of 20 nm, in which the composition is gradually changed from one composition to the other, is provided between the refractive index layers. There is. Each refractive index layer contains 1/2 of the adjacent composition gradient layer and is set to have an optical thickness of λ / 4 with an oscillation wavelength of λ. When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n (where n is the refractive index of the medium of the layer). For example, the reflectance of the lower semiconductor multilayer film reflector 102 is about 99.6%.

The lower spacer layer 103 is a layer laminated on the −Z side (upper side) of the lower semiconductor multilayer film reflector 102 and made of non-doped Al _0.15 Ga _0.85 As. The material of the lower spacer layer 103 _{is not limited to the non-doped Al 0.15} Ga _0.85 As, and may be, for example, the non-doped Al GaInP.

The active layer 104 is an active layer having a multiple quantum well structure, which is laminated on the −Z side (upper side) of the lower spacer layer 103 and has a plurality of quantum well layers and a plurality of barrier layers. The quantum well layer is made of InGaAs, and each barrier layer is made of AlGaAs.

The upper spacer layer 105 is a layer laminated on the −Z side (upper side) of the active layer 104 and composed of non-doped Al _0.15 Ga _0.85 As. _{The material of the upper spacer layer 105 is not limited to the non-doped Al 0.15} Ga _0.85 As as in the lower spacer layer 103, and may be, for example, a non-doped AlGaInP.

The portion composed of the lower spacer layer 103, the active layer 104, and the upper spacer layer 105 is also called a resonator structure, and the thickness thereof is set to be the optical thickness for one wavelength. The active layer 104 is provided in the center of the resonator structure, which is a position corresponding to the antinode in the standing wave distribution of the electric field so that a high stimulated emission probability can be obtained. Preferably, the thickness of each of the lower spacer layer 103, the active layer 104, and the upper spacer layer 105 is set so that single longitudinal mode oscillation can be obtained at the oscillation wavelength of 940 nm. Further, preferably, the relative relationship (detuning) between the resonance wavelength and the emission wavelength (composition) of the active layer 104 is adjusted so that the oscillation threshold current of the surface emitting laser element 151 becomes the smallest at room temperature.

The upper semiconductor multilayer film reflector 106 is laminated on the −Z side (upper side) of the upper spacer layer 105, and has a low refractive index layer composed of _{p—Al 0.9} Ga _{0.1 As and p—Al 0.1} Ga _{0. It} has about 30 pairs with a high refractive index layer made of 9.9 As. Between each refractive index layer, a composition gradient layer (not shown) is provided in which the composition is gradually changed from one composition to the other in order to reduce the electric resistance. Each refractive index layer includes 1/2 of the adjacent composition gradient layer and is set to have an optical length of λ / 4 (λ: oscillation wavelength). A GaAs contact layer (not shown) for achieving ohmic conduction is provided on the upper surface of the upper semiconductor multilayer film reflector 106. The reflectance of the upper semiconductor multilayer film reflector 106 is about the same as the reflectance of the lower semiconductor multilayer film reflector 102, for example, about 99.6%.

_{A selected oxide layer 108 made of p-Al 0.98} Ga _0.02 As is inserted into one of the low refractive index layers in the upper semiconductor multilayer film reflector 106 with a thickness of about 30 nm. The insertion position of the selected oxide layer 108 is, for example, a position corresponding to the second node from the active layer 104 in the standing wave distribution of the electric field. The selected oxide layer 108 includes a non-oxidized region 108b and an oxidized region 108a around the region 108b.

The antireflection film 115 is formed on the + Z side (lower side) surface (back surface 101A) of the substrate 101. The antireflection film 115 is a non-reflective coating film for an oscillation wavelength of 940 nm.

[Structure of surface emitting laser element 151]
In the surface emitting laser element 151, as shown in FIG. 2, the upper semiconductor multilayer film reflector 106 has a mesa structure. The non-oxidized region 108b is located in the center of the mesa structure in plan view. The dielectric multilayer film reflector 114 is laminated on the −Z side (upper side) of the upper semiconductor multilayer film reflector 106 so as to overlap the non-oxidizing region 108b in a plan view. In plan view, the dielectric multilayer reflector 114 is smaller than the upper semiconductor multilayer reflector 106. The dielectric multilayer film reflector 114 has at least one pair of a titanium oxide (TiOx) film and a silicon nitride (SiN) film. The reflectance of the dielectric multilayer film reflector 114 is higher than the reflectance of the lower semiconductor multilayer film reflector 102 and the reflectance of the upper semiconductor multilayer film reflector 106. In a plan view, the reflectance of the portion where the dielectric multilayer film reflector 114 and the upper semiconductor multilayer film reflector 106 overlap, that is, the central portion of the mesa structure is, for example, about 99.9%. That is, the reflectance of the upper semiconductor multilayer reflector 106 and the dielectric multilayer reflector 114 in the portion where the dielectric multilayer reflector 114 and the upper semiconductor multilayer reflector 106 overlap in a plan view is the lower semiconductor. It is higher than the reflectance of the multilayer film reflector 102 and the reflectance of the upper semiconductor multilayer film reflector 106. The lower semiconductor multilayer film reflector 102 included in the surface emitting laser element 151 is an example of the first lower reflector. The active layer 104 included in the surface emitting laser element 151 is an example of the first active layer. The upper semiconductor multilayer film reflector 106 included in the surface emitting laser element 151 is an example of the first partial reflector. The dielectric multilayer film reflector 114 is an example of a second partial reflector. The upper semiconductor multilayer film reflector 106 and the dielectric multilayer film reflector 114 included in the surface emitting laser element 151 constitute an example of the first upper reflector.

In the surface emitting laser element 151, the insulating film 111 covers the upper semiconductor multilayer film reflector 106 and the upper spacer layer 105. The insulating film 111 is, for example, a silicon nitride (SiN) film. An opening 111A is formed in the insulating film 111 to expose a part of the upper surface of the upper semiconductor multilayer film reflector 106 in the surface emitting laser element 151. In a plan view, the non-oxidized region 108b is located inside the opening 111A, and the dielectric multilayer reflector 114 is inside the opening 111A and is in contact with the upper surface of the upper semiconductor multilayer reflector 106. The p-side electrode 112 is formed on the insulating film 111. The p-side electrode 112 is in contact with the upper surface of the upper semiconductor multilayer film reflector 106 between the opening 111A and the dielectric multilayer film reflector 114. The p-side electrode 112 has, for example, a titanium (Ti) film, a platinum (Pt) film, and a gold (Au) film that are sequentially laminated on the −Z side (upper side). By flip-chip mounting, the p-side electrode 112 of the surface emitting laser element 151 is connected to the p-side electrode such as a driver IC or a submount.

[Structure of surface emitting laser element 152 and p-side contact region 155]
In the surface emitting laser element 152, as shown in FIG. 3, the upper semiconductor multilayer film reflector 106 has a mesa structure. The non-oxidized region 108b is located in the center of the mesa structure in plan view. Unlike the surface emitting laser element 151, the dielectric multilayer film reflector 114 is not provided. The lower semiconductor multilayer film reflector 102 included in the surface emitting laser element 152 is an example of the second lower reflector. The active layer 104 included in the surface emitting laser element 152 is an example of the second active layer. The upper semiconductor multilayer film reflector 106 included in the surface emitting laser element 152 is an example of the second upper reflector.

In the surface emitting laser element 152, the insulating film 111 covers the upper semiconductor multilayer film reflector 106 and the upper spacer layer 105. An opening 111B is formed in the insulating film 111 to expose a part of the upper surface of the upper semiconductor multilayer film reflector 106 in the surface emitting laser element 152. In plan view, the non-oxidized region 108b is located inside the opening 111B. The p-side electrode 112 is formed on the insulating film 111. The p-side electrode 112 is in contact with the upper surface of the upper semiconductor multilayer film reflector 106 inside the opening 111B. The p-side electrode 112 is formed with an opening 112B that exposes a part of the upper surface of the upper semiconductor multilayer film reflector 106 inside the opening 111B. In the surface emitting laser element 152, a part of the upper surface of the upper semiconductor multilayer film reflector 106 is exposed to the outside through the opening 112B.

The p-side electrode 112 in contact with the upper semiconductor multilayer film reflector 106 of the surface emitting laser element 152 extends to the p-side contact region 155, and the −Z side (upper side) of the upper semiconductor multilayer film reflector 106 within the p-side contact region 155. ) Has a part located. By flip-chip mounting, the p-side electrode 112 of the surface emitting laser element 152 is connected to the p-side electrode such as a driver IC or a submount within the p-side contact region 155.

[Structure of n-side contact region 156]
In the n-side contact region 156, as shown in FIG. 4, a groove 121 is formed in the upper semiconductor multilayer film reflector 106. Further, inside the groove 121, a groove 122 is formed in the upper spacer layer 105, the active layer 104, the lower spacer layer 103, the lower semiconductor multilayer film reflector 102, and the surface layer portion of the substrate 101.

In the n-side contact region 156, the insulating film 111 covers the upper semiconductor multilayer film reflector 106, the upper spacer layer 105, the active layer 104, the lower spacer layer 103, the lower semiconductor multilayer film reflector 102, and the substrate 101. An opening 111C is formed in the insulating film 111 at the bottom of the groove 122 to expose a part of the surface 101B of the substrate 101. The n-side electrode 113 is formed on the insulating film 111. The n-side electrode 113 is in contact with the surface 101B of the substrate 101 inside the opening 111C. The n-side electrode 113 has a portion located on the −Z side (upper side) of the upper semiconductor multilayer film reflector 106 in the n-side contact region 156. The n-side electrode 113 has, for example, a gold germanium alloy (AuGe) film laminated in order on the −Z side (upper side), a nickel (Ni) film, and a gold (Au) film. By flip-chip mounting, the n-side electrode 113 is connected to the n-side electrode such as a driver IC or a submount within the n-side contact region 156.

[Implementation of surface emitting laser 100]
The surface emitting laser 100 is used by being mounted on a submount, for example. FIG. 5 is a schematic view showing a usage example of the surface emitting laser 100. The submount and the surface emitting laser 100 mounted on the submount are included in the surface emitting laser apparatus.

In this usage example, as shown in FIG. 5, the surface emitting laser 100 is mounted on the driver IC 300 by flip-chip mounting. The p-side electrode 112 of the surface emitting laser element 151 is electrically connected to the p-side electrode provided in the driver IC 300 via the conductive material 301. The p-side electrode 112 of the surface emitting laser element 152 is electrically connected to the p-side electrode provided in the driver IC 300 via the conductive material 302 in the p-side contact region 155. The n-side electrode 113 of the surface emitting laser element 152 is electrically connected to the n-side electrode provided in the driver IC 300 via a conductive material. The surface emitting laser 100 is driven by the driver IC 300. A photodetection element 310 such as a photodiode is monolithically formed in the driver IC so as to face the surface emitting laser element 152. The photodetection element 310 detects the amount of light LB output from the surface 101B side of the substrate 101 by the surface emitting laser element 152. The driver IC 300 can obtain information for correcting the output change when the output change of the surface emitting laser element 151 occurs due to a change in the temperature environment or the like based on the amount of light of the light LB. The photodetector 310 is an example of a light receiving element, and the driver IC 300 is an example of a surface emitting laser control device.

The target on which the surface emitting laser 100 is mounted is not limited to the driver IC 300. For example, the surface emitting laser 100 may be mounted on the submount.

[Action and effect of surface emitting laser 100]
In the surface emitting laser element 151, the basic transverse mode has a mode distribution in the central portion of the surface emitting laser element 151, and the higher-order transverse mode orthogonal to this has a mode distribution mainly in the peripheral portion of the surface emitting laser element 151. It has a distribution. Further, the reflectance of the dielectric multilayer film reflector 114 is about 99.6%, and the central portion of the mesa structure in a plan view in which the dielectric multilayer film reflector 114 and the lower semiconductor multilayer film reflector 102 overlap each other. The reflectance of is, for example, about 99.9%. That is, the reflectance of the central portion where the dielectric multilayer film reflector 114 is provided is higher than the reflectance of the peripheral portion around the central portion. Therefore, the reflection loss of the basic transverse mode element having the mode distribution in the central portion of the surface emitting laser element 151 is smaller than the reflection loss of the higher-order transverse mode having the main mode distribution in the peripheral portion. As a result, the oscillation of the higher-order transverse mode is suppressed, the basic transverse mode oscillates selectively, and the laser beam LA is output from the back surface 101A side of the substrate 101. Further, the oscillation in the higher-order transverse mode causes a kink and a wider divergence angle in the current-light output characteristic, but since the surface-emitting laser element 151 suppresses the oscillation in the higher-order transverse mode, the current-light output characteristic. The linearity of the light is excellent, and the divergence angle is suppressed very narrowly. For example, the laser light emitted from each surface emitting laser element 151 at the time of output of 3 mW can realize a very narrow divergence angle within 5 ° in full width at half maximum. Therefore, the basic transverse mode oscillation is maintained up to a high injection level, and a narrow beam emission angle with a single peak can be realized in the laser beam LA.

Further, the surface emitting laser element 152 is not provided with the dielectric multilayer film reflector 114, and the reflectance of the upper semiconductor multilayer film reflector 106 is equivalent to the reflectance of the lower semiconductor multilayer film reflector 102. That is, the reflectance for all modes is lower than the reflectance of the central portion of the surface emitting laser element 151. Therefore, the extraction efficiency of the optical LB is increased, and the optical LB having a sufficient amount of light for detection can be output from the surface 101B side of the substrate 101.

Generally, the output of a laser changes due to changes in environmental temperature, deterioration over time, and the like. In particular, the output changes greatly depending on the environmental temperature, and the output decreases by about 20% to 30% when the temperature rises by about 60 ° C. Therefore, in order to obtain a stable light output, it is preferable to monitor the environmental temperature or the laser output and compensate for the change in the light output by increasing or decreasing the amount of drive current. Since the direction of laser resonance is parallel to the submount in the end face laser, the light from the cleavage plane opposite to the output end is received, the amount of light is monitored, and feedback is performed. On the other hand, in the conventional back-emission type surface emitting laser, it is difficult to monitor the amount of light because the resonator mirror surface on the opposite side to the emitting side has high reflection and is mounted on a submount or the like.

In the present embodiment, since the surface emitting laser element 152 outputs the light LB to the side opposite to the emission side of the laser light LA, the light amount can be easily detected by the photodetector element 310. Since the surface emitting laser element 152 is arranged in the vicinity of the surface emitting laser element 151 and the temperature of the surface emitting laser element 152 is about the same as the temperature of the surface emitting laser element 151, the change in the amount of light of the surface emitting laser element 152 is monitored. As a result, the fluctuation of the laser output due to the temperature change of the surface emitting laser element 151 can be corrected by adjusting the drive current, and the operation can be performed with a constant amount of light.

In the present embodiment, both the surface emitting laser element 151 and the surface emitting laser element 152 are formed so that the p-side electrode 112 is connected to the uppermost portion of the upper semiconductor multilayer film reflector 106, and the n-side electrode 113 is connected to the substrate. It is formed to do. As a result, the electrical resistance between the p-side electrode 112 and the n-side electrode 113 of the surface-emitting laser element 151 and the electrical resistance between the p-side electrode 112 and the n-side electrode 113 of the surface-emitting laser element 152 are made substantially the same. This makes it possible to facilitate simultaneous driving of the light emitting element and the monitor element.

It should be noted that the reflectance of the central portion of the surface emitting laser element 151 does not necessarily have to be higher than the reflectance of the peripheral portion of the surface emitting laser element 151. For example, even if the reflectance of the central portion of the surface emitting laser element 151 and the reflectance of the peripheral portion of the surface emitting laser element 151 are about the same, the operation of a constant amount of light is performed through the monitoring of the light amount change of the surface emitting laser element 152. It can be carried out. Therefore, for example, the dielectric multilayer film reflector 114 may be arranged at both the central portion and the peripheral portion.

[Manufacturing method of surface emitting laser 100]
Next, a method of manufacturing the surface emitting laser 100 will be described. In addition, as described above, a structure in which a plurality of semiconductor layers are laminated on a substrate 101 is hereinafter also referred to as a "laminated body" for convenience. 6 to 20 are cross-sectional views showing a method of manufacturing the surface emitting laser 100 according to the embodiment. 7 to 11 show a portion corresponding to the surface emitting laser element 151. 12 to 15 show a portion corresponding to the surface emitting laser element 152 and the p-side contact region 155. 16 to 20 show a portion corresponding to the n-side contact region 156.

First, as shown in FIG. 6, the laminate is formed by crystal growth by a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method.

Here, in the case of the MOCVD method, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as group III raw materials, and phosphine (PH ₃ ) and arsine are used as group V raw materials. (AsH ₃ ) is used. raw material is tetrabromide nitrogen of the p-type dopant _(CBr 4), dimethyl used zinc (DMZn), the raw material is used as an n-type dopant, hydrogen selenide _(H 2 Se).

Next, as shown in FIGS. 7 and 12, the upper semiconductor multilayer film reflector 106 including the selected oxide layer 108 is etched to correspond to the region corresponding to the surface emitting laser element 151 and the surface emitting laser element 152. In the region, a mesa structure is formed on the upper semiconductor multilayer reflector 106. As the etching, for example, inductively coupled plasma (ICP) dry etching, electron cyclotron resonance (ECR) dry etching and the like can be performed. At this time, as shown in FIG. 16, a groove 121 is formed in the upper semiconductor multilayer film reflector 106 in the region corresponding to the n-side contact region 156.

Then, as shown in FIGS. 8, 13 and 17, the laminate is heat-treated in steam. As a result, Al (aluminum) in the selected oxide layer 108 is selectively oxidized from the outer peripheral portion of the mesa structure, and the non-oxidized region 108b surrounded by the oxidized region 108a of Al is formed in the central portion of the mesa structure. Remains. That is, a so-called oxidative constriction structure is formed, which limits the path of the drive current of the light emitting portion only to the central portion of the mesa structure. The non-oxidized region 108b is a current passing region.

Subsequently, as shown in FIG. 18, the n side is formed by etching the upper spacer layer 105, the active layer 104, the lower spacer layer 103, the lower semiconductor multilayer film reflector 102, and the surface layer portion of the substrate 101. In the region corresponding to the contact region 156, a groove 122 is formed in the upper spacer layer 105, the active layer 104, the lower spacer layer 103, the lower semiconductor multilayer film reflector 102, and the surface layer portion of the substrate 101. By performing the etching for forming the groove 122 after the selective oxidation of the selected oxide layer 108, it is possible to prevent damage to the selected oxide layer 108 before the selective oxidation. In the region corresponding to the surface emitting laser element 151 and the region corresponding to the surface emitting laser element 152, the upper spacer layer 105, the active layer 104, the lower spacer layer 103, the lower semiconductor multilayer film reflector 102, and the like. The surface layer portion of the substrate 101 is maintained as it is (FIGS. 8 and 13).

Next, as shown in FIGS. 9, 14 and 19, an insulating film 111 is formed on the entire surface of the substrate 101 on the surface 101B side. The insulating film 111 can be formed, for example, by a chemical vapor deposition (CVD) method. After that, the openings 111A, 111B and 111C are formed in the insulating film 111. The openings 111A, 111B and 111C can be formed, for example, by wet etching with buffered hydrofluoric acid (BHF).

Subsequently, as shown in FIG. 10, in the region corresponding to the surface emitting laser element 151, the upper semiconductor multilayer film is formed so as to overlap the non-oxidized region 108b in a plan view while leaving a gap between the surface emitting laser element 151 and the opening 111A. A dielectric multilayer film reflector 114 is formed on the reflector 106.

Next, as shown in FIGS. 11 and 15, the p-side electrode 112 is formed in the region corresponding to the surface emitting laser element 151, the region corresponding to the surface emitting laser element 152, and the region corresponding to the p-side contact region 155. .. Further, as shown in FIG. 20, the n-side electrode 113 is formed in the region corresponding to the n-side contact region 156. The p-side electrode 112 and the n-side electrode 113 can be formed by, for example, a lift-off method. Either the p-side electrode 112 or the n-side electrode 113 may be formed first. In the formation of the p-side electrode 112 and the formation of the n-side electrode 113, after film formation, heat treatment is performed in a reducing atmosphere or an inert atmosphere, and ohmic conduction is achieved by eutecticization of the semiconductor material and the electrode material.

After that, the back surface 101A of the substrate 101 is polished and mirrored to form an antireflection film 115 on the back surface 101A (see FIGS. 2 to 4).

In this way, the surface emitting laser 100 can be manufactured.

The planar shape of the dielectric multilayer film reflector 114 is not particularly limited. FIG. 21 is a diagram showing an example of the planar shape of the dielectric multilayer film reflector 114.

For example, as shown in FIG. 21A, the planar shape of the dielectric multilayer film reflector 114 may be circular. As shown in FIG. 21B, the planar shape of the dielectric multilayer film reflector 114 may be square.

The planar shape of the dielectric multilayer film reflector 114 may be an anisotropic shape. In the present disclosure, the anisotropic shape means a shape that does not overlap with the original shape when rotated by 90 degrees. That is, it is sufficient that the planar shapes of the dielectric multilayer film reflector 114 are different in the two directions orthogonal to each other, and it is preferable that the widths of the dielectric multilayer film reflector 114 are different in the two directions orthogonal to each other. For example, as shown in FIG. 21C, the planar shape of the dielectric multilayer film reflector 114 is a circular portion, a portion extending from the circular portion to the + Y side, and a circular portion to the −Y side. It may have an extending portion. As shown in FIG. 21 (d), the planar shape of the dielectric multilayer film reflector 114 extends from the square portion to the + Y side and from the square portion to the −Y side. It may have a portion to be used. As shown in FIG. 21E, the planar shape of the dielectric multilayer film reflector 114 may be an ellipse with the Y-axis direction as the semimajor axis. As shown in FIG. 21 (f), the planar shape of the dielectric multilayer film reflector 114 may be a rectangle with the Y-axis direction as the longitudinal direction.

When the planar shape of the dielectric multilayer film reflector 114 is anisotropy, anisotropy is introduced into the optical loss of the surface emitting laser element 151, the loss of the mode having a specific polarization component becomes large, and oscillation is suppressed. Will be done. As a result, it becomes possible to obtain a laser output in which the polarization directions are aligned.

Further, when performing deflection control, the substrate 101 is preferably an inclined substrate. In this case, it is preferable that any of the anisotropic directions in the dielectric multilayer film reflector 114 is parallel to the tilting direction of the tilted substrate.

In the present embodiment, the dielectric multilayer film reflector 114 is used as the second partial reflector, but a semiconductor multilayer film reflector may be used as the second partial reflector.

(Second Embodiment)
Next, the second embodiment will be described. The second embodiment relates to a light source device and a detection device including the surface emitting laser 100 according to the first embodiment. FIG. 22 shows an outline of the distance measuring device 10 as an example of the detecting device.

The distance measuring device 10 includes a light source device 11 as an example of the light source device. The distance measuring device 10 projects (irradiates) pulsed light from the light source device 11 to the detection object 12, receives the reflected light from the detection object 12 by the light receiving element 13, and before receiving the reflected light. This is a TOF (time of flight) type distance detection device that measures the distance to the detection object 12 based on the required time.

As shown in FIG. 22, the light source device 11 has a light source 14 and an optical system 15. The light source 14 includes a surface emitting laser 100 according to the first embodiment, and a current is sent by a light source driving circuit 16 to control light emission. The light source drive circuit 16 transmits a signal to the signal control circuit 17 when the light source 14 emits light. The optical system 15 has an optical element (for example, a lens, a DOE, a prism, etc.) that adjusts the divergence angle and direction of the light emitted from the light source 14, and irradiates the detection object 12 with the light.

The reflected light projected from the light source device 11 and reflected by the detection object 12 is guided to the light receiving element 13 through the light receiving optical system 18 having a condensing action. The light receiving element 13 includes a photoelectric conversion element, and the light received by the light receiving element 13 is photoelectrically converted and sent to the signal control circuit 17 as an electric signal. The signal control circuit 17 calculates the distance to the detection object 12 based on the time difference between the light projection (light emission signal input from the light source drive circuit 16) and the light reception (light reception signal input from the light receiving element 13). Therefore, in the distance measuring device 10, the light receiving optical system 18 and the light receiving element 13 function as a detection system in which the light emitted from the light source device 11 and reflected by the detection object 12 is incident. Further, the signal control circuit 17 may be configured to acquire information on the presence / absence of the detection target object 12, the relative speed with the detection target object 12, and the like based on the signal from the light receiving element 13. The light receiving element 13 is an example of the second light receiving element.

In the present embodiment, since the surface emitting laser 100 that emits high-power light with a single transverse mode is used, more accurate detection and measurement can be performed.

Although the preferred embodiments and the like have been described in detail above, the embodiments are not limited to the above-described embodiments and the like, and various embodiments and the like described above are used without departing from the scope of the claims. Modifications and substitutions can be added.

10 Distance measuring device 11 Light source device 13 Light receiving element 15 Optical system 18 Light receiving optical system 100 Surface emitting laser 102 Lower semiconductor multilayer film reflector 104 Active layer 106 Upper semiconductor multilayer film reflector 108 Selected oxide layer 108a Oxidized region 108b Non-oxidized Region 114 Dielectric multilayer film reflector 151, 152 Surface emitting laser element 153 Laser element array

Japanese Unexamined Patent Publication No. 2014-007293

Claims (11)

With the board
A first surface emitting laser element formed on the substrate and outputting the first light,
A second surface emitting laser element formed on the substrate and outputting a second light,
Have,
The first surface emitting laser element includes a first lower reflector, a first active layer, and a first upper reflector in order from the substrate side.
The second surface emitting laser element includes a second lower reflector, a second active layer, and a second upper reflector in order from the substrate side.
The reflectance of the second upper reflector is smaller than the reflectance of the first upper reflector.
A surface emitting laser in which the first light is output from the substrate side and the second light is output from the second upper reflector side. The surface emitting laser according to claim 1, wherein the first upper reflecting mirror includes a first partial reflecting mirror and a second partial reflecting mirror. The second partial reflector is provided in the central portion of the first upper reflector in a plan view from a direction perpendicular to the substrate, and the reflectance in the central portion is measured by the first upper reflector. The surface emitting laser according to claim 2, wherein the reflectance is higher than that of a peripheral portion that is not provided. The surface emitting laser according to claim 2 or 3, wherein the second partial reflector is smaller than the first partial reflector in a plan view from a direction perpendicular to the substrate. The surface emitting laser according to any one of claims 2 to 4, wherein the second partial reflector has an anisotropic shape with respect to two directions parallel to the substrate and orthogonal to each other. The surface emitting laser according to any one of claims 2 to 5, wherein the first partial reflector has the same configuration as the second upper reflector. The surface according to any one of claims 2 to 6, wherein the first partial reflector has a semiconductor multilayer film reflector, and the second partial reflector has a dielectric multilayer film reflector. Luminous laser. The second surface emitting laser element further includes an electrode capable of injecting a current into the second upper reflector, and the electrode includes an opening for outputting the second light. 7. The surface emitting laser according to any one of 7. The surface emitting laser according to any one of claims 1 to 8.
A light receiving element that receives the second light output by the second surface emitting laser element, and a light receiving element that receives the second light.
Have,
A surface emitting laser device in which the output of the light receiving element is input to the surface emitting laser control device. The surface emitting laser apparatus according to claim 9,
A drive device for driving the surface emitting laser device and
With
A light source device that emits light from the surface emitting laser to the outside. The light source device according to claim 10 and
A second light receiving element capable of detecting light emitted from the surface emitting laser to the outside and reflected by an object, and
A detection device.

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