JPH05335625A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To obtain a semiconductor light emitting element the output per one chip of which can be increased by forming light emitting elements having p-n or pin junctions on both surfaces of a conductive substrate and causing the p-n or pin junctions to emit light. CONSTITUTION:A p-type GaAs buffer layer 2, p-type AlGaAs clad layer 3, i-type AlGaAs active layer 4, n-type AlGaAs clad layer 5, and n-type GaAs contact layer 6 are successively grown by an MOCVD method on both surfaces of a p-GaAs substrate 1. Then a ridge structure 7 having a 5mum width and step 8 for forming electrodes on the substrate 1 are formed by chemical etching and an SiO2 film 9 constituting an insulating layer is formed by a sputtering method. In addition, an AuGe film which becomes an n-type electrode 10 and AuCr film which becomes a p-type electrode 11 are formed by a vacuum deposition method. Therefore, when this product is applied to an LD, a semiconductor light emitting element which can outputs a higher optical output as compared with the conventional element having the same size can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection type semiconductor light emitting device.

[0002]

2. Description of the Related Art A light emitting diode (LED) and a semiconductor laser (LD) are known as typical light emitting elements. LEDs and LDs are compound semiconductors (GaAs, Ga)
A pn or pin junction is formed in (P, AlGaAs, etc.), and a forward voltage is applied to the junction to inject carriers into the junction, and a light emission phenomenon that occurs in the process of recombination thereof is utilized. Conventionally, such LEDs and LDs have been
GaAs, AlG on a single crystal substrate such as GaAs or InP
Compound semiconductors lattice-matched to the respective substrates such as aAs, InP, InGaAsP, etc. are subjected to liquid phase epitaxy (LP
E), metal-organic vapor phase epitaxy (MOCVD), vapor phase epitaxy (VPE), molecular beam epitaxy (MBE method), etc. It was That is, in an LED or LD, a pn junction or a pin junction is formed on one surface of an n-type or p-type single crystal substrate by sequentially epitaxially growing a semiconductor material having the same conductivity type as that of the substrate and a semiconductor material having a conductivity type different from that of the substrate. Was there. Then, light is emitted by passing a current between the substrate and the electrodes provided on the surface of the epitaxial growth film.

[0003]

In recent years, LDs have been used for pumping solid-state lasers such as Nd: YAG lasers. The optical output is required as the characteristic of this LD. Since a single laser cannot obtain the output required for this, LD
An LD array in which is arranged or a two-dimensional array of LD arrays is used. As described above, a large number of LDs are required to excite the solid-state laser.

On the other hand, a multi-color display using LEDs has LEDs of different emission wavelengths as shown in FIG.
It is manufactured by lining up. The figure shows the case where surface emitting LEDs of two colors, red and green, are used. The red LED 51 and the green LED 52 as a pair are die-bonded on the X wiring 53 on the alumina multilayer wiring board 50, and the other electrodes of the LED are bonded to the Y _R wiring 54 and the Y _G wiring 55, respectively. FIG. 6 shows this matrix wiring. For example, when a forward voltage is applied between X _{2 and} Y _1G , green LE
D: D _21G lights up. Also X ₃ -Y _2R and X ₃ -Y _2G
When an electric field is applied at the same time, it is observed that D _32R and D _32G simultaneously emit light and emit yellow light. However, in this display, two elements are required to form one dot.

The first object of the present invention is to provide a semiconductor light emitting device which solves the above problems of the prior art and achieves the same total output with a smaller number of devices, in other words, a high light output per chip. A second object is to provide a semiconductor light emitting device capable of outputting multiple wavelengths.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor light emitting device which emits light by passing a current through a pn junction or a pin junction.
forming a light emitting element having an n-junction or a pin junction,
A current is caused to flow between the electrode provided on the surface of the substrate and the electrode provided on the surface of the element to form a pn junction or pi provided near both sides of the substrate.
It is characterized in that light is emitted at an n-junction.

According to another aspect of the semiconductor light emitting element of the present invention, the band gap of the semiconductor material forming the pn junction or the pin junction on both surfaces of the substrate is different, and the emission wavelength is different between the light emitting elements provided on both surfaces of the substrate. To do.

In the present invention, a light emitting device using the substrate as a common electrode can be obtained by performing epitaxial growth on both surfaces of the substrate to form a pn junction or a pin junction and processing the same. As the process technology including the structure of the light emitting device and the epitaxial growth, the conventionally known technology can be applied as it is.

In the semiconductor light emitting device according to the present invention, a light output twice as large as that of the conventional one can be taken out from a chip having substantially the same size. Also, by applying it to an LD array, it is possible to extract the same optical output with a bit number of ½, that is, with a width of ½.

As an application of this technique, an LD or an LED that oscillates at two wavelengths can be obtained by changing the composition of the light emitting layer or the added impurities on both sides of the substrate. For example, a GaP-LED emits light through a deep level, and emits light of wavelengths from green to red depending on the process of recombination of the levels or carriers. Therefore, an n-type GaP substrate is used to epitaxially grow GaP doped with Zn and O on one surface and p-type GaP doped with N on the other surface. When a common electrode is taken out from n-GaP and a forward voltage is applied between this electrode and the electrode provided in the former growth layer, light is emitted in red, and a forward voltage is applied between the electrode provided in the latter material. This makes it possible to emit green light. Since the band gap of GaP has energy larger than that of light of any of these wavelengths, when a forward voltage is applied to the elements on both sides at the same time, yellow light is emitted as light to the end face and both faces of the substrate with the naked eye. I can observe. When this diode is applied to an LED display, it is possible to reduce the number of elements to 1/2 even if the number of pixels is the same.

In the present invention, GaAs, InP, Ga
P, AlGaAs, InGaAs, InGaAsP, A
III-V group compound semiconductors such as lGaInP, ZnS, ZnSe, ZnTe, CdS, CdSe,
Any material such as a binary or more II-VI group compound semiconductor including CdTe and a group IV semiconductor such as Si, Ge, or SiC can be used. In the application to the LD, it is possible to make the oscillation wavelengths of both surfaces of the substrate the same, and it is also possible to oscillate at different wavelengths. In the present invention, even in the case of multicoloring of LEDs, the present invention has described the combination of red and green using GaP, but the present invention is not limited to this, and various combinations of the above, such as a combination of an AlGaAs red LED on a GaAs substrate and a ZnSe blue LED, are possible. It is possible to use the above materials.

[0012]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of an LD according to the first embodiment of the present invention. FIG. 2 is a perspective view of an LD according to a second embodiment of the present invention that also uses diffusion. FIG. 3 shows a third embodiment of the present invention.
It is a perspective view of LD concerning. FIG. 4 is a perspective view schematically showing a multicolor display using the surface-emitting type LED of the present invention. Example 1 Hereinafter, as an example of the present invention, AlG was formed on both surfaces of a GaAs substrate.
An example of producing aAs-LD will be described. The structure of the LD was a ridge waveguide type as shown in FIG. On both surfaces of the 100 μm-thick p-GaAs substrate 1 polished on both sides, MO
The p-GaAs buffer layers 2 and p are respectively formed by the CVD method.
-AlGaAs clad layer 3, i-AlGaAs active layer 4, n-AlGaAs clad layer 5 and n-GaAs
The contact layer 6 was sequentially grown. Subsequently, a ridge structure 7 having a width of 5 μm and step 8 for providing an electrode on the substrate were formed by chemical etching. The SiO ₂ film 9 serving as an insulating layer is sputtered, and the AuGe film serving as the n-type electrode 10 and the p-type electrode 1 are formed.
The AuCr film to be No. 1 was formed by the vacuum evaporation method. When this LD was die-bonded to a Cu heat sink and the light emission characteristics were evaluated, the oscillation threshold value was 4 for any element on any surface.
It was around 0 mA. The maximum output of the element on the heat sink side was about 35 mW per one end face, and the maximum output of the element on the side not on the heat sink side was about 30 mW per one end face. This difference is due to heat. Further, when current was simultaneously injected into the elements on both sides, an output of about 60 mW was obtained. At this time, the end surface is not coated.
In the above embodiment, the ridges on both sides of the substrate are aligned on the vertical line of the substrate, but by shifting them, the thermal diffusion efficiency at the time of simultaneous lighting is improved and the total power can be increased. Example 2 As an example of application of the present invention to another LD, an example in which the GaAs substrate is formed on both sides will be described. The structure of the LD was a ridge waveguide type as shown in FIG. Double side polished p-G
Both sides of the aAs substrate 1 were p-typed by the MOCVD method.
A GaAs buffer layer 2, a p-AlGaAs cladding layer 3, an i-AlGaAs active layer 4, an n-AlGaAs cladding layer 5 and an n-GaAs contact layer 6 were sequentially grown. In order to take out the common electrode, Zn was diffused into a part of the substrate by a closed tube method to form a Zn diffusion region 13. Then, in order to separate the ridge structure 7 having a width of 5 μm and the Zn diffusion region 13, a separation etching groove 14 reaching the substrate was formed. This can prevent the semiconductor laser from acting as a lateral junction type semiconductor laser. The SiO2 film 9 serving as an insulating layer was formed by sputtering, and the AuGe film serving as the n-type electrode 10 and the AuCr film serving as the p-type electrode 11 were formed by vacuum deposition. Book LD
When die was bonded to a Cu heat sink and the light emitting characteristics were evaluated, the oscillation threshold value was about 40 mA for the devices on any surface. The maximum output of the element on the heat sink side is about 35 mW per one end face, and the maximum output of the element on the side not on the heat sink side is about 30 mW per one end face.
Met. This difference is due to heat. Further, when current was simultaneously injected into the elements on both sides, an output of about 60 mW was obtained. At this time, the end surface is not coated. Example 3 As an example of the present invention, an LED using GaP will be described with reference to FIG. As shown in FIG. 3A, n−
An SiO ₂ film was formed on a part of the surface of the GaP substrate 20 and used as a film for selective growth in a post process. Te-doped n-GaP layer 2 on the remaining surface of the n-GaP substrate 20
1, the GaP layer 22 added with Zn and O is selectively
It was grown by the PE method. Then, on the back surface of the substrate, N-doped G
The aP layer 23 and the Zn-doped GaP layer 24 were grown by the LPE method. After removing the SiO ₂ film for selective growth, an n-type common electrode 25 and a p-type electrode 26 were formed. See also FIG.
As shown in (b), a p-type polka dot electrode 27 was formed on the rear surface portion facing the n-type common electrode 25 on the front surface. When a forward bias was applied between the n-type common electrode 25 and the p-type electrode 26, red light was emitted from the opening 28 through the substrate. On the other hand, between the n-type common electrode 25 and the p-type polka dot electrode 27, green light was emitted from the spaces 29, 29, 29 between the p-type polka dot electrodes 27.

By applying this multi-LED to an LED display, if the number of pixels is the same, the number of elements is halved.
It becomes possible to FIG. 4 is a perspective view schematically showing a multicolor display using the surface-emitting type LED of the present invention. This multi-LED 31 is die-bonded onto the X wiring 32 and the Y _R wiring 33 on the alumina multilayer wiring board 30, and the upper electrode is the bonding wire 3
5 electrically connects to the Y _G wiring 34. This matrix wiring is equivalent to that shown in FIG. When a forward voltage is applied between, for example, X ₂ -Y _1G , the green LED: D _21G is turned on as in the case shown above. Also X ₃ −
When an electric field is applied simultaneously to Y _2R and X ₃ -Y _2G , D _32R and D _32G emit light at the same time, and it is observed that they emit yellow light.

[0015]

When the present invention is applied to the LD, it becomes possible to take out a higher optical output than that of the conventional one. It is also possible to oscillate at a plurality of different wavelengths by changing the composition of the light emitting layer on both surfaces of the substrate or by using materials having different light emitting mechanisms. When the light emitting device according to the present invention is applied to, for example, a multi-color display, the number of devices can be reduced to 1/2.

[Brief description of drawings]

FIG. 1 is a perspective view of an LD according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an LD according to a second embodiment of the present invention that also uses diffusion.

FIG. 3A is a perspective view of an LD according to a third embodiment of the present invention. (B) is the figure which looked at (a) from the back.

FIG. 4 is a perspective view schematically showing a multi-color display using surface emitting LEDs of the present invention.

FIG. 5 is a perspective view of a conventional LED display.

FIG. 6 is a matrix wiring diagram of the LED display.

[Explanation of symbols]

1 p-GaAs substrate 2 p-GaAs buffer layer 3 p-AlGaAs clad layer 4 i-AlGaAs active layer 5 n-AlGaAs clad layer 6 n-GaAs contact layer 7 ridge structure 8 step 9 SiO ₂ film 10, 12 n-type electrode 11, 26 p-type electrode 13 Zn diffusion region 14 isolation etching groove 20 n-GaP substrate 21 Te-doped GaP layer 22 Zn, O-doped GaP layer 23 N-doped GaP layer 24 Zn-doped GaP layer 25 n-type common electrode 27 p-type water drop Electrode 28 Opening 29 Between p-type dot electrodes 30, 50 Alumina multilayer wiring board 31 Multi LED 32, 53 X wiring 33, 54 Y _R wiring 34, 55 Y _G wiring 35 Bonding wire 51 Red LED 52 Green LED

Claims (2)

[Claims] 1. A semiconductor light-emitting device that emits light by passing a current through a pn junction or a pin junction, in which light-emitting devices having a pn junction or a pin junction are formed on both surfaces of a conductive substrate, and electrodes provided on the surface of the substrate and the device surface. A semiconductor light-emitting device characterized in that a current is caused to flow between the electrodes provided on the substrate to emit light at a pn junction or a pin junction provided near both surfaces of the substrate. 2. The semiconductor according to claim 1, wherein the band gaps of the semiconductor materials forming the pn junction or the pin junction on both sides of the substrate are different, and the emission wavelength is different between the light emitting elements provided on both sides of the substrate. Light emitting element.