JP2001007399A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element capable of efficiently emitting light generated in a light emitting layer. SOLUTION: Among light generated in an active layer 106, light traveling downward in the drawing is reflected by an electrode 103 acting as a reflection layer, travels upward and is radiated to the outside. The electrode 103 is made of a metal and hence reflects approximately all of the light, irrespective to their incident angles, thus enabling the element to extract light at high efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor light emitting device.

[0002]

2. Description of the Related Art In recent years, semiconductor light-emitting elements have been widely used in outdoor display devices, display devices for automobiles, and the like.

FIG. 9 shows a configuration of a conventional semiconductor light emitting device. On the surface of an n-type GaAs substrate 201, an n-type GaAs
Buffer layer 202, n-type DBR made of InGaAlP and GaAs and reflecting light using Bragg reflection effect
(Distributed Bragg Reflector) Reflective layer 203, InG
n-type cladding layer 204 made of aAlP, active layer 20
5. p-type cladding layer 206 made of InGaAlP, A
p-type window layer 207 made of 1GaAs, p-type Ga
As contact layers 208 are sequentially formed.

Then, an n-type electrode 209 is formed on the back side of the n-type GaAs substrate 201 and a p-type electrode 210 is formed on the p-type GaAs contact layer 208 to supply power to the light emitting element.
Light emission is realized in the active layer 205. Light generated from the active layer 205 in the downward direction in the figure is reflected by the reflective layer 203, and together with the light generated in the upward direction, the window layer 2 is formed.
It is radiated above the element via 07.

[0005]

However, the conventional semiconductor light emitting device has the following problems.

[0006] Of the light generated downward from the active layer 205, the light traveling vertically toward the reflective layer 203 is reflected by the reflective layer 203 without being absorbed by the substrate 201, and is effectively extracted to the outside. be able to.

However, the reflectivity of the reflective layer 203 is extremely low with respect to light traveling at an oblique angle toward the reflective layer 203, and all the light emitted from the active layer 205 cannot be extracted to the outside.

The present invention has been made in view of the above circumstances, and has as its object to provide a semiconductor light emitting device capable of efficiently extracting light generated from a light emitting layer to the outside.

[0009]

According to the present invention, there is provided a semiconductor light emitting device formed of a semiconductor substrate, a metal material on the semiconductor substrate, a reflective layer for reflecting light, and a reflective layer formed on the reflective layer. A light-emitting layer that emits light, formed on the light-emitting layer,
A light-transmitting electrode having a light-transmitting property.

Here, the translucent electrode may be formed using an ITO film.

It is preferable that the light emitting layer has a double hetero structure in which both surfaces of an active layer are sandwiched by cladding layers.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration of a semiconductor light emitting device according to a first embodiment of the present invention.

Au on the surface of the p-type silicon substrate 101
Electrodes 102 and 103 made of / Zn, p-type GaAs
s contact layer 104, In (x ') Ga (y') Al
A p-type cladding layer 105 made of (1-x'-y ') P,
In (x ") Ga (y") Al (1-x "-
y ") P active layer 106, In (x"") G
a (y "") Al (1-x ""-y "") P n-type clad layer 107, n-type GaAs contact layer 108, ITO translucent electrode 109, bonding Cr
/ An electrode 110 is formed in order. Then, a p-type electrode 111 is formed on the back side of the substrate 101 and the electrode 110 is formed.
And 111, a voltage is applied to supply power to the light emitting element, and light emission is realized in the active layer 106.

According to such a configuration, of the light generated from the active layer 106, the light emitted in the upward direction in the figure passes through the light-transmitting cladding layer 107 and the thin GaAs contact layer 108. Then, the light is transmitted to the outside through the translucent electrode 109.

Light emitted downward from the active layer 106 is applied to the cladding layer 105 and the thin contact layer 104.
, Is reflected by the electrode 103 acting as a reflective layer, is radiated upward from the element, and is extracted to the outside.

Here, unlike the conventional reflection layer, the electrode 103 is formed of a metal material. For this reason, the change in reflectance with respect to the incident angle is extremely small, and almost total reflection can be performed, so that light can be extracted efficiently.

The n-type and p-type contact layers are made of InGaP.
Alternatively, by changing to an InGaAlP material, the band gap difference with the cladding layer is reduced, and the operating voltage can be further reduced.

Further, by providing the electrode 110 made of metal on the upper surface of the translucent electrode 109, the stress distortion applied to the active layer 106 by the translucent electrode 109 can be reduced, so that the reliability is improved.

Further, when the p-type electrode 103 has a layer structure of a transparent conductive film and a metal containing Al or Ag, the reflectance can be increased, and the light output of the light emitting element increases.

Next, a second embodiment of the present invention will be described with reference to FIG. On the surface of the Al substrate 301, Sn
P-type electrode 303 made of solder layer 302, Au / Zn consisting Pb, thickness 500 Å, a p-type GaAs contact layer 304 having a carrier concentration 1E19 cm ^-3, thickness of 2 [mu] m, an In carrier concentration 5E18cm ^-3 (x ') Ga
(Y ') Al (1-x'-y') P (0 = <(x ',
y ′) = p-type cladding layer 305 composed of <1), In
(X ") Ga (y") Al (1-x "-y")
Active layer 3 composed of P (0 = <(x ″, y ″) = <1)
06, thickness 1.5 μm, carrier concentration 3E18 cm ^-3
n (x "") Ga (y "") Al (1-x ""-
n-type cladding layer 307 made of y '''') P (0 = <(x '''', y '''') = <1), n-type GaAs contact layer 308 having a thickness of 500 angstroms and a carrier concentration of 1E19 cm- ^3. , An ITO (Indium Tin Oxide) translucent electrode 309 and a bonding Cr / An electrode 310 are formed.

According to the structure of this embodiment, Al
A light emitting layer having a double hetero structure including an active layer 306 and clad layers 305 and 307 is provided on a substrate 301. Therefore, heat generated in the active layer 306 is radiated through the Al substrate 301. As a result, even at a high temperature of 100 degrees Celsius, operation can be performed without a decrease in light emission output.

Here, the composition (x ', x "", y', y "") of the cladding layers 305 and 307 and the active layer 30
6 (x ″, y ″) with the cladding layers 305 and 3
By adjusting the band gap of 07 to be larger than the band gap of the active layer 306, the density of electrons and holes contributing to light emission can be sufficiently increased, and the light output can be improved. Further, when the active layer 306 has a single quantum well structure or a multiple quantum well structure including a well layer of several tens angstroms and a barrier layer of several tens angstroms, a low current and high optical output can be obtained. Further, by changing the composition of the active layer 306, light emission from red to green can be achieved. Further, the n-type and p-type contact layers are made of InGaP or InGaAs.
By setting to 1P, light can be extracted without being absorbed by the contact layer.

Next, a third embodiment of the present invention will be described with reference to FIG. The n-type electrodes 411 and 402 made of Au / Ge are formed on the lower surface and the upper surface of the n-type silicon substrate 401.
P-type electrode 403 made of Ni / Au, p-type GaN contact layer 404, p-type clad layer 40 made of AlGaN
5, active layer 406 made of InGaN, n-type clad layer 407 made of AlGaN, n-type GaN contact layer 4
08, ITO translucent electrode 409, Cr /
An electrode 410 is formed.

According to this embodiment, since the current is spread by the ITO translucent electrode 409 and injected into the entire active layer 406, the entire area of the active layer 406 can emit light. Light generated above the active layer 406 is transmitted through the light-transmitting cladding layer 407, further transmitted through the contact layer 408 and the electrode 409, and emitted to the outside. Light generated below the active layer 406 passes through the cladding layer 405 and the contact layer 404, is totally reflected by the p-type electrode 403, is emitted upward, and is extracted to the outside.

Since the electrode 403 serving as the reflective layer is made of metal, the light is totally reflected without being internally absorbed, and the light can be efficiently extracted to the outside. The electrode 403
By using a metal containing l and Ag, the reflectance is further increased and the light output is improved.

Here, the cladding layer is made of In (x1) Ga.
(Y1) Al (1-x1-y1) N material may be used, and the band gap can be controlled by changing the compositions x1 and y1. Further, similarly, the active layer 406 has In (x
2) Ga (y2) Al (1-x2-y2) N material may be used, and light emission from infrared to ultraviolet can be realized by changing the compositions x2 and y2. In particular, by setting the lattice constants of the cladding layer and the active layer to be the same, high luminance can be realized with a low current. In the ultraviolet, the ITO transparent electrode 409
The light output can be further increased by reducing the thickness of the substrate to several hundred angstroms or using a thin film metal of several tens of amperes.

Next, as a fourth embodiment of the present invention,
A method of manufacturing the semiconductor light emitting device according to the first embodiment will be described with reference to FIGS.

As shown in FIG. 4, a GaAs buffer layer 11, an InGaAlP selective etching layer 12, and a n-type GaAs buffer layer 11 are formed on a GaAs substrate 10 by MOCVD or MBE.
-GaAs contact layer 108, n-InGaAlP cladding layer 107, active layer 10 made of InGaAlP
6, an InGaAlP cladding layer 105 and a p-GaAs contact layer 104 are sequentially grown and formed.

Next, as shown in FIG. 5, after the p-type electrode 103 is formed on the surface of the contact layer 104, the p-type electrode 103 is formed beforehand on the upper and lower surfaces. S to the p-type silicon substrate 101
The bonding is performed via a solder layer 13 such as nPb.

After the end face of the wafer is covered with wax while leaving the selective etching layer 12, as shown in FIG. 6, the selective etching layer 12 is removed by etching using phosphoric acid or sulfuric acid. Here, by increasing the temperature of phosphoric acid or sulfuric acid, etching can be easily performed.

Next, as shown in FIG. 7, a light transmitting electrode 109 and a bonding electrode 110 are formed on the surface of the contact layer 108. Then, the wafer is divided into a plurality of chips by performing scribing or dicing.

As shown in FIG. 8, an LED chip 2 is formed on a frame 1 or a substrate by using an Ag paste 4 or the like.
Is mounted, bonding is performed between the LED chip 2 and the frame 1 or the substrate using the Au wire 3. Then, a resin mold 5 is formed so as to cover the LED chip 2 and the Au wire 3.

The above-described embodiments are merely examples, and do not limit the present invention. For example, a substrate other than a p-type silicon or n-type silicon substrate may be used. When a substrate made of a metal material such as Cu, Fe, Al, or stainless steel is used, the heat radiation effect is extremely large, and even when a large current of several tens of amperes or the like flows, the light output does not generate saturation due to heat generation. Operation is possible even at an ambient temperature of 100 degrees.

In the above embodiment, the electrode 102 and the electrode 103 are in direct contact. However, both electrodes 1
An intermediate layer using a material such as In, Ag, Ni, or Cr may be interposed between 02 and 103. In this case, the thermal strain of the active layer can be reduced, so that the reliability can be improved.

By providing a strain relaxation layer located between the p-type contact layer and the p-type cladding layer in the middle of the band gap between them, dislocation generated from the hetero interface due to current injection is prevented. be able to. in this case,
By including In in the strain relaxation layer, the crystal structure is softened and the growth of dislocations can be suppressed.

[0037]

As described above, according to the present invention,
By using a reflective layer made of a metal material, a high reflectance can be obtained without depending on the angle of incident light on the reflective layer, and light generated inside the element can be efficiently extracted to the outside. It is.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of a semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a configuration of a semiconductor light emitting device according to a third embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a longitudinal section of a device in a step of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing a longitudinal section of the device in a step that follows the step shown in FIG. 4 in the method for manufacturing the semiconductor light-emitting element.

FIG. 6 is a longitudinal sectional view showing a longitudinal section of the element in a step following the step shown in FIG. 5 in the method for manufacturing the semiconductor light emitting element.

FIG. 7 is a longitudinal sectional view showing a longitudinal section of the element in a step following the step shown in FIG. 6 in the method for manufacturing the semiconductor light emitting element.

FIG. 8 is a longitudinal sectional view showing a longitudinal section of the element in a step that follows the step shown in FIG. 7 in the method of manufacturing the semiconductor light-emitting element.

FIG. 9 is a longitudinal sectional view showing a configuration of a conventional semiconductor light emitting device.

[Explanation of symbols]

Reference Signs List 1 frame 2 LED chip 3 Au wire 4 Ag paste 5 resin mold 10 GaAs substrate 11 GaAs buffer layer 12 InGaAlP etching layer 101 p-type silicon substrate 102, 103, 111, 303 p-type electrode 104, 304 p-type made of Au / Zn GaAs contact layers 105, 305 In (x ') Ga (y') Al (1-
x-y ') P-type cladding layer 106, 306 In (x'') Ga (y'') Al
Active layer 107,307 In (x "") Ga (y "") A made of (1-x "-y") P
n-type cladding layer 108, 308 made of l (1-x ""-y "") n-type GaAs contact layer 109, 309, 409 ITO translucent electrode 110, 310, 410 Cr / An electrode for bonding 13, 302 Solder layer 401 n-type silicon substrate 402, 411 n-type electrode 404 p-type GaN contact layer 408 n-type GaN contact layer 403 p-type electrode 405 p-type cladding layer made of AlGaN 406 Active layer made of InGaN 407 made of AlGaN n-type cladding layer

Continuing on the front page (72) Inventor Yukio Watanabe 1-Front Term, Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa F-term (Reference) 5F041 AA03 CA04 CA33 CA34 CA35 CA46 CA65 CA74 CA77 CA82 CA88 CA92

Claims (3)

[Claims] A semiconductor substrate; a reflective layer formed on the semiconductor substrate using a metal material to reflect light; a light emitting layer formed on the reflective layer to emit light; and formed on the light emitting layer. And a light-transmitting electrode having a light-transmitting property. 2. The method according to claim 1, wherein the translucent electrode is made of indium tin oxide (ITO).
2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is formed using a film. 3. The semiconductor light emitting device according to claim 1, wherein said light emitting layer has a double hetero structure in which both surfaces of an active layer are sandwiched between cladding layers.