JP2000022282A - Surface light-emitting-type light-emitting device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high reflection factor, and superior electric characteristics that can supply current to a compound semiconductor where electric resistance containing impurities is relatively low and having no need for supplying current to a first reflection film with large resistance. SOLUTION: A laser resonator 10 is provided with a first reflection film 14 where a plurality of dielectrics that are selectively provided on a GaN thin-film substrate 12 and are formed by a different material quality are laminated, a compound semiconductor layer that contains an n-type GaN spacer layer 16 being continuously formed at a part where the first reflection film 14 and the GaN thin-film substrate 12 are exposed, an activation layer 18, and a p-type GaN spacer layer 20, and a second reflection film 22 that is provided on the p-type GaN spacer layer 20 while the film 22 opposes the first reflection film 14. In this case, a dielectric layer is used for the first reflection film 14 where a higher reflection factor is required, thus providing a high reflection factor. Also, current flows in the n-type GaN spacer layer 16, the activation layer 18, and the p-type GaN spacer layer 20, and the current does not flow in the first reflection film 14 with relatively high electric resistance, thus providing superior electric characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface emitting light emitting device, and more particularly, to a surface emitting light emitting device having a reflection film formed of a dielectric.

[0002]

2. Description of the Related Art Surface-emitting type semiconductor lasers that emit light having a wavelength ranging from ultraviolet to green have attracted attention with the development of thin film fabrication techniques for gallium nitride based semiconductor materials. In a surface-emitting type semiconductor laser, laser oscillation is realized by a resonator in which a very thin active layer made of a laser medium is sandwiched between a pair of reflective films having high reflectivity.

Heretofore, several structures of surface emitting semiconductor lasers using a gallium nitride-based compound semiconductor have been proposed. For example, Japanese Patent Application Laid-Open No. 7-335975 discloses a structure using a gallium nitride-based semiconductor multilayer film or a gallium nitride-based semiconductor multilayer film and a metal thin film as a set of reflection films constituting a laser resonator. The combined structure is shown. Further, for example, Japanese Patent Application Laid-Open No. 8-307001
The publication discloses a structure in which a multilayer film of a gallium nitride-based semiconductor and a dielectric multilayer film are combined as one set of reflection films constituting a laser resonator.

[0004]

However, in the case of a multilayer reflective film composed of a gallium nitride based semiconductor, Japanese Patent Application Laid-Open No.
As described in Japanese Patent No. 35975, when a current is injected into a laser, the current is usually passed through a semiconductor multilayer reflective film having a relatively high electric resistance. For this reason, the electrical characteristics of the laser element deteriorate. Further, when a large amount of impurities contributing to conductivity are mixed into the reflective film in order to lower the electric resistance, free electrons (holes) existing in the mixed portion absorb light and the reflectance of the multilayer reflective film is reduced. Furthermore, when the multilayer reflective film is made of a semiconductor, the choice of materials is limited, so that the refractive index difference between the materials cannot be increased, and the reflection characteristics are restricted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a surface-emitting type light-emitting device having high reflectance and excellent electrical characteristics.

[0006]

According to the present invention, there is provided a first reflection film, which is a multilayer film selectively provided on a substrate and formed by laminating a plurality of dielectrics formed of different materials. A p-type and / or n-type compound semiconductor layer including an active layer continuously formed on an exposed portion of the substrate and the exposed portion of the substrate, and the first reflective film on a part of the compound semiconductor layer And a second reflection film provided so as to face the surface light-emitting device.

[0007] At least a part of the compound semiconductor can be formed by epitaxial growth. The second reflective film may be formed of any one of a multilayer film in which a plurality of dielectric layers formed of different materials are stacked, a multilayer film in which compound semiconductor layers having different compositions are stacked, and a metal thin film. Can be. The compound semiconductor layer,
The semiconductor device may further include a current confinement layer provided on the active layer and configured to flow a current only in a selected region. This current confinement layer can be formed by implanting ions into a compound semiconductor. Further, at least a part of the compound semiconductor layer can be formed using a semiconductor containing any of gallium nitride and a gallium arsenide compound in a part of a main composition.

Further, according to the present invention, a first reflection film is formed by stacking a plurality of dielectric layers formed of different materials on a main surface of a substrate, and the first reflection film is selectively removed. Forming a spacer layer on the exposed portion of the first reflective film and the substrate by using a compound semiconductor by epitaxial growth; forming an active layer on the spacer layer using the compound semiconductor; The present invention also provides a method for manufacturing a surface-emitting light emitting device, wherein a second reflection film is formed so as to face the first reflection film.

FIG. 1 shows Ga which is a semiconductor as a multilayer reflection film.
The relationship between the number of laminated pairs of multilayer films and the reflectance at a wavelength of 410 nm when a multilayer film of N and AlN is used and when a multilayer film of SiO ₂ and ZrO ₂ as dielectric materials is used is shown. . As can be seen from the figure, when the reflection film is made of a dielectric, a high reflectance can be obtained with a smaller number of pairs as compared with the case where the reflection film is made of a semiconductor.

FIG. 2 shows a case where a multilayer film of 22 pairs of GaN and AlN is used as a multilayer reflective film,
4 shows a reflection spectrum when a laminated film of iO ₂ and ZrO ₂ is used. From this figure, at 410 nm which is the center wavelength, a reflectance of 99.5% or more can be obtained in any case.
It can be seen that the wavelength width in which a high reflectance is maintained is much wider when the reflection film is made of a dielectric.

As described above, the surface emitting type light emitting element in which the reflection film, particularly the reflection film (first reflection film) on the substrate which requires a higher reflectivity, is made of a dielectric has a higher reflection film. It can be seen that a high reflectance can be maintained over a wide range with a smaller number of pairs than a surface emitting light emitting element formed of a semiconductor.

Further, according to the present invention, on the compound semiconductor layer (on the lowermost layer and the uppermost layer when there are two or more compound semiconductor layers, and on the active layer when the compound semiconductor layer is formed only of the active layer) In the case where the second reflective film is formed of metal, an electrode is provided on the lowermost layer of the compound semiconductor layer and the second reflective film is used as an electrode. As a result, current can be passed only to the compound semiconductor having a relatively low electric resistance containing impurities or the second reflective film formed of a metal having a relatively low electric resistance, and the first reflective film having a high electric resistance Since it is not necessary to supply a current to the device, excellent electrical characteristics can be obtained.

Several light emitting devices using a dielectric multilayer film have been proposed so far. However, since a semiconductor is not usually epitaxially grown on a dielectric multilayer reflective film, in these light-emitting elements, as described in JP-A-8-307001, the dielectric multilayer film Is also used as a surface layer that is not formed. For this reason, the structure of the laser was restricted, and there were many steps for fabricating the element.

According to the present invention, a method of forming a compound semiconductor layer on an exposed portion of a substrate and a first reflective film is used, wherein the dielectric layer is used as a first reflective film between the substrate and the active layer. As a method, a technique called selective growth is used. Selective growth is described, for example, in the Apol published by Kapolnek et al.
plied Physics Letters Vo
l. 71, p. 1204, 1997 (This paper discloses that a GaN crystal is exposed on the surface by controlling crystal growth conditions when GaN is epitaxially grown on a GaN single crystal thin film partially covered with a SiO ₂ film. It is disclosed that the GaN single crystal can be grown not only on the upper surface but also on the lateral direction, so that a GaN single crystal can be produced on the SiO ₂ ). This technique can be used for gallium arsenide as well as gallium nitride.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, Ga is used as a substrate.
N, sapphire, SiC, Si, and GaAs, and combinations thereof can be used.

As the dielectric material of the first reflection film, SiO ₂ , ZrO ₂ , Al ₂ O ₃ or the like can be used.

The compound semiconductor layer on the first reflection film can include a spacer layer, a current confinement layer, an electron block layer, and the like, if necessary, in addition to the active layer. The material of the compound semiconductor layer is GaN, GaAs, InGaN, AlGaN,
InGaAs and AlGaAs can be used. Silicon and selenium can be used as the n-type dopant, and carbon, zinc, and magnesium can be used as the p-type dopant.

The second reflection film is any one of a multilayer film in which a plurality of dielectric layers formed of different materials are laminated, a multilayer film in which compound semiconductor layers having different compositions are laminated, and a metal thin film. Can be. As the dielectric that can be used for the second reflection film, the above-described dielectric can be used. As the compound semiconductor that can be used for the second reflection film, the above-described compound semiconductor can be used. Metals that can be used for the second reflective film include:
Those having high reflectivity, for example, gold and AuNi alloy can be used.

To manufacture this light emitting device, first, the first
Is formed on the main surface of the substrate. As a film forming method, MOCVD, MBE, epitaxial growth, or the like can be used. Next, unnecessary portions of the first reflective film are removed by using photolithography and etching such as wet etching, plasma etching, reactive ion etching, and light-assisted etching.

Next, a compound semiconductor layer is formed by selective growth. The crystal growth conditions at this time can be determined as appropriate by experiments and the like. When there are two or more compound semiconductor layers, the lowermost layer can be formed by selective growth, and the layers above the lowermost layer can be formed by a method similar to the method of forming the first reflective film. Note that the current confinement layer can be formed by implanting hydrogen ions into the compound semiconductor after forming the compound semiconductor layer or oxidizing a part of the compound semiconductor.

Next, a second reflection film is formed so as to face the first reflection film. Second with dielectric layer or compound semiconductor
When the reflection film is formed, the same method as the method of forming the first reflection film can be used. In the case where the second reflective film is formed of a metal, a lift-off method or the like can be used.

In order to extract a laser beam from the second reflection film, it is desirable that the reflectance of the first reflection film is higher than that of the second reflection film.
And the material, thickness, laminated structure, and the like of the second reflective film are prepared.

[0023]

The present invention will be described below with reference to examples. (Embodiment 1) FIG. 3 is a sectional view schematically showing the structure of a laser resonator 10 according to the present invention. FIG. 4 shows a perspective view of the laser resonator 10 of FIG.

As shown in FIG. 3 and FIG. 4, the laser resonator 10 of this device is provided on a surface of a (0001) GaN thin film substrate 12 formed on a (0001) sapphire substrate. Formed first reflection film 14
An n-type GaN spacer layer 16 having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ formed on an exposed portion of the GaN thin film substrate 12 and the first reflection film 14;
6 and a p-type Ga having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ formed on the active layer 18.
An N spacer layer 20, a second reflective film 22 formed on the p-type GaN layer spacer 20 so as to face the first reflective film 14, and a second reflective film 22 on the p-type GaN spacer layer 20. And a p-type electrode 24 formed so as to surround
And an n-type electrode 26 formed on a part of the N spacer layer 16.

In the first reflection film 14, S having different refractive indexes is used.
The two dielectric films of iO ₂ and ZrO ₂ each have an optical film thickness of approximately ほ ぼ of the oscillation wavelength (722 in the case of SiO _2).
7 cycles are alternately laminated so as to have Angstroms and 46.4 Angstroms in the case of ZrO ₂ , and further, an SiO ₂ film having an optical thickness of about の of the oscillation wavelength is further laminated.

The active layer 18 is a quadrupole well having In _0.08 Ga _0.92 N having a thickness of 105 Å and In _0.15 Ga _0.85 N having a thickness of 35 Å, and having a carrier concentration of 1 × 10 ¹⁸ cm ^-3 . And an active region formed of p-type Al _0.2 Ga _0.8 N having a thickness of 200 Å.

In the p-type GaN spacer layer 20,
A current confinement layer 28 is formed in order to narrow the flow path of the current flowing from the electrode into the element by reducing the conductivity to an opening and to efficiently emit laser light.

In the second reflection film 22, S having different refractive indexes is used.
Nine periodic dielectric films of iO ₂ and ZrO ₂ are alternately laminated so as to have an optical film thickness of approximately ほ ぼ of the oscillation wavelength.

In this laser resonator 10, the oscillation wavelength of the laser light is 410 nm, and the laser light is
2 from the upper part. The distance between the first reflection film 14 and the second reflection film 22, that is, the thickness of each compound semiconductor layer is adjusted so that the optical thickness becomes twice the oscillation wavelength.

This laser resonator 10 was manufactured by the method shown in FIGS.

First, on the surface of the (0001) plane GaN thin film substrate 12 formed on the (0001) plane sapphire substrate, the optical film thickness is reduced to 1/4 of the laser oscillation wavelength by electron beam evaporation. As described above, SiO ₂ and ZrO ₂ are alternately stacked for seven periods, and further, an SiO ₂ film having an optical film thickness substantially equal to １ ／ of the oscillation wavelength is formed to form the first reflection film 14 (FIG. 5A )).

Next, by photolithography and wet etching using buffered hydrofluoric acid, unnecessary portions of the first reflection film 14 are striped (for example, 10 μm in width) in the <1-100> direction (perpendicular to the paper). To expose a part of the GaN thin film substrate 12 (FIG. 5).
(B)).

Next, an n-type GaN spacer layer 16 is formed from the exposed portion of the GaN thin film substrate 12 at a growth temperature of 1050 ° C.
Growth pressure 50 Torr, atmosphere gas H ₂ 3 liter /
Min, trimethylgallium (source gas) 20 μmol / min,
Epitaxial growth was performed under the condition of 1.5 liters / minute of ammonia, and selective growth was also performed in the lateral direction, that is, on the first reflection film 14 (FIG. 5C).

Further, an n-type GaN spacer selectively grown
On top of layer 16 is In with a thickness of 105 Å._0.08
Ga_0.92N and In with a film thickness of 35 Å_0.15
Ga _0.85Quadrupole well containing N and 200 angstrom thickness
ROHM's p-type Al_0.2Ga_{0. 8}MOCV with N active region
The active layer 18 was formed by the method D (FIG. 5).
(D)).

Next, a p-type GaN spacer layer 20 is epitaxially grown on the active layer 18 (FIG. 5E), and hydrogen ions are implanted into a part of the p-type GaN spacer layer 20 to partially Then, a current constriction layer 28 having an opening (a circular opening of 4 μm) was formed (FIG. 6A).

Next, an N layer is formed on the p-type GaN spacer layer 20.
A p-type electrode 24 was formed by a lift-off method using an alloy of i and Au (FIG. 6B). Next, by photolithography and dry etching using a chlorine compound, p
The p-type GaN spacer layer 20, the current confinement layer 28, the active layer 18, the n-type GaN spacer layer 16 and a part of the first reflection film 14 in the region where the type electrode 24 is not formed are removed, and then the n-type GaN Ti on the exposed portion of the spacer layer 16
Electrode 2 by a lift-off method using an alloy of
6 was formed (FIG. 6C).

Next, the optical film thickness in the region surrounded by the p-type electrode 24 is reduced to １ ／ of the laser oscillation wavelength by electron beam evaporation.
The second reflective film 22 was formed by alternately laminating nine periods of SiO ₂ and ZrO ₂ so as to obtain (FIG. 6D).

In the above manufacturing method, the distance between the first reflection film 14 and the second reflection film 22 was adjusted so that, for example, the optical film thickness was twice the oscillation wavelength.

In the laser resonator 10, since a dielectric is used for the first reflection film 14 and the second reflection film 22, the reflectance is high, and the current flows through the n-type GaN spacer layer 16 and the active layer. Layer 18, opening in current confinement layer 28, and p-type G
Since the semiconductor layer flows through the compound semiconductor layer including the impurity and having a relatively low electric resistance and does not flow through the dielectric layer having a high electric resistance, excellent electric characteristics can be obtained.

[0040]

According to the present invention, a high reflectance can be provided because a dielectric is used for the first reflection film which requires a higher reflectance. Further, the present invention provides excellent electric characteristics because current can flow in a compound semiconductor having a relatively low electric resistance including impurities and there is no need to flow current in the first reflective film having a large resistance. be able to.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of laminated pairs of multilayer reflective films and the reflectance.

FIG. 2 shows reflection spectra of a dielectric multilayer reflective film and a semiconductor multilayer reflective film.

FIG. 3 is a sectional view schematically showing the structure of a laser resonator according to an embodiment of the present invention.

FIG. 4 is a perspective view of the laser resonator shown in FIG. 3;

FIG. 5 is a sectional view showing a manufacturing process of the laser resonator of FIG. 3;

FIG. 6 is a sectional view showing a manufacturing process of the laser resonator of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 laser resonator 12 GaN thin film substrate 14 first reflective film 16 n-type GaN spacer layer 18 active layer 20 p-type GaN spacer layer 22 second reflective film 24 p-type electrode 26 n-type electrode 28 current confinement layer

Claims (7)

[Claims] A first reflection film selectively provided on a substrate and being a multilayer film in which a plurality of dielectrics made of different materials are laminated; and exposing the first reflection film and the substrate. A p-type and / or n-type compound semiconductor layer including an active layer, which is formed continuously at the portion where the first reflection film is provided, on a part of the compound semiconductor layer; A surface-emitting light-emitting device comprising: a second reflective film; 2. The surface emitting light emitting device according to claim 1, wherein at least a part of the compound semiconductor is formed by epitaxial growth. 3. The second reflection film is one of a multilayer film in which a plurality of dielectric layers formed of different materials are laminated, a multilayer film in which compound semiconductor layers having different compositions are laminated, and a metal thin film. The surface-emitting light-emitting device according to claim 1 or 2, wherein 4. The surface-emitting device according to claim 1, wherein the compound semiconductor layer further includes a current confinement layer provided on the active layer and flowing a current only to a selected region. Type light emitting element. 5. The surface emitting light emitting device according to claim 4, wherein the current confinement layer is formed by implanting ions into a compound semiconductor. 6. The semiconductor device according to claim 1, wherein at least a part of said compound semiconductor layer is formed of a semiconductor containing at least one of gallium nitride and a gallium arsenide compound.
The surface-emitting light-emitting device according to any one of the above. 7. A first reflection film is formed by laminating a plurality of dielectric layers formed of different materials on a main surface of a substrate, and the first reflection film is selectively removed. Forming a spacer layer on the exposed portion of the reflective film and the substrate by using a compound semiconductor by epitaxial growth; forming an active layer on the spacer layer using a compound semiconductor; forming the first layer on the active layer; A method for manufacturing a surface-emitting type light emitting device, wherein a second reflective film is formed so as to face the reflective film.