JPH0786691A - Light emitting device - Google Patents

Abstract

PURPOSE:To propose electrode wiring structure to drive a light emitting device which uses a surface emitting laser and provide a light emitting device which is proper to a projection type display, for example. CONSTITUTION:A horizontal resonator type surface emitting laser 20 is laid out in two dimensions on an insulating board where a lower layer electrode 21 is formed in the shape of lines, extending in the direction of the length of a resonator of each surface emitting laser 20. An electrode insulation unit 16 is installed for each line where an upper layer electrode 24 is installed on a line-shaped pattern so that it may cross the lower layer electrode 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device formed by integrating a surface emitting laser.

[0002]

2. Description of the Related Art A so-called surface-emitting type laser which outputs a laser beam in a direction perpendicular to a substrate is arranged in a matrix, and is used as, for example, parallel information processing. Has been reported (for example, “ELECTRONICS LETTERS 27 (1991) 583”).

However, in the above completely independent wiring, the number and density of laser elements that can be driven are considerably limited in consideration of the wiring space and the number of electrode pads, and large scale integration is impossible.

Further, if a vertical cavity surface emitting laser, which is expected to have a relatively simple wiring structure, is used, the electric resistance between the terminals becomes large and causes heat generation, which is disadvantageous for high density arraying. .

[0005]

DISCLOSURE OF THE INVENTION The present invention proposes an electrode wiring structure for driving a surface emitting laser using the above-described surface emitting laser, and is suitable for application to, for example, a projection (projection type) display. A light emitting device is provided.

[0006]

According to the present invention, a horizontal cavity surface emitting laser 20 is two-dimensionally mounted on an insulating substrate 1 as shown in FIG. The lower layer electrodes 21 are arranged in a line and extend in the cavity length direction of each surface emitting laser 20, and the electrode insulating portion 16 is provided for each line, and the upper layer electrodes 24 are arranged in a line pattern orthogonal to the lower layer electrodes 21. Is provided.

Further, in the present invention, the upper layer electrode 24 of the surface emitting laser 20 in the above structure has an air bridge type structure. Furthermore, in the present invention, the electrodes are patterned on a substrate which is separate from the substrate 1 in the above-mentioned configuration, and both substrates are superposed so as to be connected to the upper layer electrode 24 of the surface emitting laser 20. Further, according to the present invention, the external reflecting mirror 25 of the surface emitting laser 20 is composed of a recrystallized growth layer.

[0008]

As described above, according to the present invention, since the lower layer electrode 21 is formed for each line of the two-dimensionally arranged surface emitting laser 20, it is possible to drive each line, and the line shape orthogonal to the lower layer electrode 21 can be obtained. By providing the upper electrode 24 of the pattern and stacking the electrodes formed on a separate substrate such as an air bridge type or a heat sink, a simple matrix type drive becomes possible, which allows various display devices such as a projection display. Can be applied to.

Further, in particular, the external reflection mirror 2 of the surface emitting laser 20.
By constituting 5 by the recrystallized growth layer, the surface property thereof can be made favorable and the angle control can be formed with high precision, so that light emission can be performed more efficiently.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Each embodiment of the present invention will be described in detail with reference to the drawings together with the manufacturing process in order to facilitate understanding thereof. In this example, AlG is formed on a GaAs insulating substrate.
The case where a light emitting device is obtained by forming an aAs-based surface emitting laser will be described.

First, in this example, as shown in one manufacturing process diagram of FIG. 2, a substrate 1 made of semi-insulating GaAs or the like is used.
On the n-type GaAs buffer layer 2, n-type Al
First clad layer 3 made of _0.35 Ga _0.65 As, active layer 4 made of intrinsic GaAs, p-type Al _0.35 Ga
The second cladding layer 5a made of _0.65 As or the like is sequentially epitaxially grown by, for example, MOCVD (chemical vapor deposition method using organic metal). Then, for example, n-type A
Similarly, after the current confinement layer 6 made of _0.45 Ga _0.55 As or the like is epitaxially grown, pattern etching is performed by applying photolithography or the like so as to remove the current passage portion 7, and the current passage portion is further embedded on this. Second cladding layer 5b made of p-type Al _0.35 Ga _0.65 As, etc.
Is epitaxially grown, and a cap layer 7 made of p-type GaAs or the like is also epitaxially grown to form SA
An N (Self Aligned Narrow-Stripe) type semiconductor laser structure is formed. In FIG. 2A, the arrow a indicates the direction in which the current passage portion 7 extends, for example, the [001] crystal axis direction of the <001> crystal axis direction, and the arrow b indicates the direction orthogonal to the main surface of the substrate 1, <100>. > For example, in the crystal axis direction [1
00] indicates the crystal axis direction.

FIG. 3A is a sectional view taken along the <011> crystal axis direction indicated by arrow a at this time. Then, as shown in FIG. 3B, in the case of AlGaAs based on an anisotropic dry etching technique such as RIE (reactive ion etching), for example, a mixed gas of SiCl ₄ and He is used to make a vertical direction with respect to the main surface of the substrate 1. Etching is performed in different directions to form the end faces 9A and 9B that regulate the resonator, and the laser portion 10 having the regulated resonator structure is formed on both end faces.
FIG. 4 shows a schematic linear enlarged perspective view in this state. 4, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 5A, a material transparent to the emission wavelength is used so as to cover the entire surface including the end faces 9A and 9B constituting the resonator mirror, like the cladding layers 3 and 5, for example. A window portion growth layer 11 made of Al _0.35 Ga _0.65 As is epitaxially grown by MOCVD or the like. As a result, the end surfaces 9A and 9B formed by etching are further flattened, and the effect of reducing the end surface light density and the like can be obtained by forming the window portion. Even if the light density increases when applied, it is possible to prevent the reliability of the element from decreasing.

Then, in the case where coatings having different reflectances are applied to both resonator end faces 9A and 9B, dielectric layers 12a and 12b for high reflection coating are obliquely applied by sputtering or electron beam evaporation. . That is, as shown by an arrow c in FIG. 5A, first, for example, a dielectric layer 12a of SiO ₂ , Si or the like is formed on the end surface 9A side, for example.
Apply layer by layer. Then, as shown by an arrow d in FIG. 5B, a dielectric layer 12b of SiO ₂ , Si or the like is provided on the end face 9B side.
Are laminated in plural layers, for example.

Further, a dielectric layer 12c such as SiN _x or SiO _{2 is} deposited on the entire surface by plasma CVD (chemical vapor deposition method) or the like, and both end surfaces 9A and 9A when the oscillation wavelength is λ. The total thickness of the dielectric layer deposited on 9B is adjusted to be λ / 2, for example. This plasma CVD aims to cover all the vertical surfaces formed in FIG. 3C described above, and serves to insulate electrodes formed in a later step and to protect elements in the etching process. When facet reflectivity control is not performed, λ / 2 is obtained by plasma CVD.
It is also possible to simply provide a dielectric layer having a thickness of.

Then, as shown in FIG. 6A, the dielectric layers 12 (12a-12c) other than the portions on the vertical end faces are removed by etching. In this case, by performing anisotropic dry etching such as RIE over the entire surface as shown by an arrow e, the dielectric layer 12 in the other part can be removed in a self-aligned manner while leaving only the vertical end face part. .

Then, as shown in FIG. 6B, the MO
For example, p-type GaAs of the same material as the cap layer 8 is grown by CVD, and the regrown layer 13 is selectively formed in the portion where the dielectric layer is removed. In this case, the upper portion of the laser portion restricted by the both end surfaces 9A and 9B is previously etched by applying, for example, photolithography, the window growth layer 11 is removed, and the upper portion of the cap layer 8 is further etched.

Then, a regrowth layer 13 is epitaxially grown on the entire surface including the above with the same material as that of the cap layer 8 in the region where the dielectric layer 12 is removed. At this time, GaAs, AlGaA is formed by MOCVD, MBE (molecular beam epitaxy), low pressure MOCVD, or the like.
When the regrowth layer 13 made of GaAs such as s, InP, InAlGaP, etc. in this case is epitaxially grown, crystal planes equivalent to the {001} crystal planes constituting the dielectric layer 12, that is, (001) (00-1), (010 ), (0-10)
Once the {110} crystal face is generated from the edge of each crystal face of, the regrowth layer 13 is {0} because the epitaxial growth is relatively slow on the {110} crystal face.
The crystal is grown while forming an inclined surface composed of a {110} crystal plane that forms an angle of 45 ° with the 01} crystal plane and the main surface of the substrate 1.

Therefore, this {110} crystal plane is externally 45 °.
By using it as a reflecting mirror, it is possible to obtain a surface emitting laser which extracts the laser light emitted from the active layer 4 in a direction substantially perpendicular to the substrate 1. In this case, since the reflecting mirror is formed by crystal growth, the crystallinity is good, the flatness and surface are excellent, and the angle control can be performed accurately.

At this time, if the etching depth of the upper portion of the cap layer 8 is not sufficient, eave-shaped protrusions 13a may be formed at both ends of the regrown layer 13 on the cap layer 8 as shown in FIG. Therefore, it is necessary to select the depth appropriately. In FIG. 7, parts corresponding to those in FIGS. 6A and 6B are designated by the same reference numerals, and redundant description will be omitted.

Next, the structure of the lower layer electrode and the upper layer electrode for the surface emitting laser thus formed will be described together with its manufacturing method. In FIG. 8A, portions corresponding to those in FIGS. 6A and 6B are designated by the same reference numerals, and duplicate description will be omitted.

Here, the regrown layer 13 is, for example, p-type GaAs made of the same material as the cap layer, and the window grown layer 11 is AlGa.
Since it is an As layer, for example, by performing wet etching with an etching solution of 4 ° C. in which NH ₄ OH and H ₂ O ₂ are mixed at 1:30, the window portion growth layer 11 is used as an etching stop layer for the laser portion. The regrowth layer 13 other than the external reflecting mirror that has been regrown on both sides of 10 can be selectively removed as shown in FIG. 8B. Then, the exposed window growth layer 11 is removed, and, for example, Au, Ni and A are removed.
A lower electrode 15 is formed by sequentially stacking uGe.

As a method of depositing the lower layer electrode 15, for example, coating is performed so that the edge of the resist has an inverse taper shape,
It is possible to form an electrode pattern by patterning by pattern exposure and development, evaporating an electrode metal, removing the resist, and then lifting off.

Alternatively, in the case of plating, for example, the lower layer resist is patterned in a forward taper shape, then the lower layer metal is vapor-deposited as a whole, a resist pattern is further formed, and the resist is removed after plating. The electrode 15 can be patterned by removing the metal portion thinly deposited by milling or the like by etching and finally removing the lower layer resist. When this plating is used, the number of process steps is slightly increased, but the controllability of the electrode thickness and shape is superior to the lift-off method described above.

Further, as shown in FIG. 8C, the electrode insulating portion 16 which electrically separates the surface emitting lasers 20 is formed in a stripe shape parallel to the lower layer electrode 21 with a depth reaching the insulating substrate 1. It is formed by applying photolithography or the like.

Then, as shown in FIG. 9A, for example, polyimide 22 is deposited so as to embed the lower layer electrode 21 to planarize the entire surface. In FIG. 9, parts corresponding to those in FIGS. Then, the contact hole 23 is formed by exposing the upper part of the surface-emitting laser 20 on the regrown layer 13.

Thereafter, an upper layer electrode 24 in which, for example, Au, Pt, and Ti are sequentially laminated is patterned by lift-off or plating similarly to the above-mentioned lower layer electrode 21, and the polyimide 22 is removed as shown in FIG. 9B. Thus, the air bridge type upper layer electrode 24 can be formed.

With this manufacturing method, as shown in FIG. 1, the surface-emitting laser 20 provided with the external reflecting mirror 25 by recrystallization growth is arranged two-dimensionally so as to face each resonator end face, and the lower layer electrode thereof. A simple matrix in which 21 is formed in a line shape extending in the resonator length direction, the electrode insulating portion 16 is provided for each line, and the upper layer electrode 24 is provided in a line shape extending in a direction orthogonal to the lower layer electrode 21. A light-emitting device that can be driven can be obtained.

Thus, basically by using the metal wiring as the electrode wiring, the resistance can be reduced as compared with the case where the semiconductor layer is used, and by forming the air bridge type upper layer electrode by wiring, The capacitance between the lower layer electrode and the upper layer electrode can be reduced. Also, by properly selecting the thickness and width of these electrodes,
The wiring resistance can be further reduced.

In the above-mentioned example, the upper electrode 24 has an air bridge structure, but as shown in the plan view of one manufacturing process thereof in FIG. 1 is formed by patterning the electrode 31 on the substrate 30 having the structure shown in FIG.
As shown in FIG. 1, these two substrates 1 and 30 may be superposed on each other as shown by an arrow f, and in this case, the electrode forming process can be further simplified. Further, in this case, heat dissipation can be improved by using the substrate 30 as a heat sink material. 10 and 11
9A and 9B, parts corresponding to those in FIGS.

Various changes can be made in the process of selective growth of the regrown layer 13 described above. For example, after the steps described in FIGS. 5A to 5C described above are performed, as shown in FIG.
As indicated by an arrow g, anisotropic etching such as RIE is performed to remove the dielectric layer 12 on the cap layer 8 and the regions having a predetermined distance from the resonator end faces 9A and 9B. After this,
When the regrowth layer 13 is epitaxially grown as shown in FIG. 12B, it is possible to control the distance between the end faces 9A and 9B and the external reflecting mirror formed by the inclined surface of the regrowth layer 13. Further, in this case, there is no possibility that an eave-shaped projection as described with reference to FIG. 7 is formed on the upper portion of the cap layer 8. In FIG. 12, parts corresponding to those in FIGS. 9A and 9B are designated by the same reference numerals, and redundant description will be omitted.

Further, as shown in FIG. 13, only the region which covers the entire surface of the laser resonator and faces the end faces 9A and 9B is selectively removed by anisotropic etching such as RIE as shown by an arrow h. You can also FIG. 14 shows a schematic linear enlarged perspective view in this case. Also in this example, the distance between the resonator end face and the external reflecting mirror can be controlled. Further, for example, by removing the current passage portion and depositing the upper layer electrode on the dielectric layer 12 on the cap layer 8 in a later step, the SAN structure as described in FIG. It can be applied to a laser structure without layers.

Furthermore, even if the lower layer wiring is deposited on the upper surface of the regrowth layer 13 on both sides of the surface emitting laser 20 in the step of FIG. 8A, for example, conduction with the substrate side can be obtained. However, since it is difficult to keep a space from the upper layer wiring, it is desirable to remove the regrowth layer and attach the lower layer wiring in this case.

Needless to say, the present invention is not limited to the above-described embodiments, but various modifications and changes can be made in the semiconductor material and structure of the surface emitting laser.

[0035]

As described above, according to the present invention, it is possible to easily drive a large-scale and high-density two-dimensional surface emitting laser, and it is possible to apply it to a display, and particularly to a projection display. By
For example, it is possible to construct a stereoscopic display using the polarization direction of laser light.

Further, since the horizontal cavity type laser is used, the inter-terminal resistance can be made smaller than that of the vertical cavity type laser and the like, and the heat generation can be suppressed, which is advantageous for the high density array. .

Further, by using the electrode metal as the lower layer wiring, the resistance can be reduced as compared with the case where the semiconductor layer is used. Further, by forming the upper layer electrode in the air bridge structure, the capacitance between the upper layer electrode and the lower layer electrode can be reduced.

The electrode manufacturing process can be simplified by wiring the upper layer electrode with the electrode formed on a substrate separate from the substrate on which the laser is grown. By using a heat sink material that is transparent to the emission wavelength and has high thermal conductivity, heat dissipation can be improved and heat generation of the laser can be further suppressed.

In particular, the wiring resistance can be further reduced by making the thickness and width of these wiring electrodes as large as possible.

Furthermore, in the manufacturing process of the surface emitting laser, an end face window structure can be formed by epitaxially growing a semiconductor layer over the entire surface after forming the end facet of the cavity, and thereby flattening the end facet of the resonator and end face light. The density can be reduced, and it can be used as an etching stop layer for the wiring of the lower layer electrode in the subsequent manufacturing process, and the manufacturing process can be further simplified.

[Brief description of drawings]

FIG. 1 is a schematic enlarged perspective view of an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of an example of the present invention.

FIG. 3A is a manufacturing process diagram of an embodiment of the present invention.
B is a manufacturing process drawing of one example of the present invention.

FIG. 4 is a manufacturing process diagram of an example of the present invention.

FIG. 5A is a manufacturing process diagram of an embodiment of the present invention.
B is a manufacturing process drawing of one example of the present invention. C is a manufacturing process diagram of an example of the present invention.

FIG. 6A is a manufacturing process diagram of an embodiment of the present invention.
B is a manufacturing process drawing of one example of the present invention.

FIG. 7 is a manufacturing process diagram of the reference example.

FIG. 8A is a manufacturing process diagram of an embodiment of the present invention.
B is a manufacturing process drawing of one example of the present invention. C is a manufacturing process diagram of an example of the present invention.

FIG. 9A is a manufacturing process diagram of an embodiment of the present invention.
B is a manufacturing process drawing of one example of the present invention.

FIG. 10A is a manufacturing process drawing of another embodiment of the present invention. B is a manufacturing process drawing of another embodiment of the present invention.

FIG. 11 is a manufacturing process drawing of another embodiment of the present invention.

FIG. 12A is a manufacturing process drawing of another embodiment of the present invention. B is a manufacturing process drawing of another embodiment of the present invention.

FIG. 13 is a manufacturing process drawing of another embodiment of the present invention.

FIG. 14 is a manufacturing process drawing of another embodiment of the present invention.

[Explanation of symbols]

 1 substrate 2 buffer layer 3 first clad layer 4 active layer 5 second clad layer 6 current confinement layer 7 current passage part 8 cap layer 9A end face 9B end face 10 laser part 11 window part growth layer 12 dielectric layer 13 re-growth Layer 16 Electrode insulation 21 Lower layer electrode 24 Upper layer electrode

Claims (4)

[Claims] 1. A horizontal cavity surface emitting laser is two-dimensionally arranged on an insulating substrate, and a lower layer electrode is formed in a line extending in the cavity length direction of the surface emitting laser. 2. A light emitting device, comprising: an electrode insulating portion; and an upper layer electrode provided in a linear pattern orthogonal to the lower layer electrode. 2. The light emitting device according to claim 1, wherein an upper electrode of the surface emitting laser has an air bridge structure. 3. The electrode is patterned on a substrate separate from the substrate, and the two substrates are superposed so as to be connected to the upper layer electrode of the surface emitting laser. The light-emitting device according to. 4. The external reflection mirror of the surface emitting laser is constituted by a recrystallized growth layer.
Alternatively, the light emitting device according to 2 or 3.