JPS6173388A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To give even an optical extracting window an effective electrode function, to increase longitudinal currents in currents flowing through a light- emitting layer consisting of a double hetero-junction and to improve luminous efficiency by forming a GaAlAs layer having low resistance and low Al concentration onto the light-emitting layer and using the GaAlAs layer as the optical extracting window. CONSTITUTION:An n-type GaAs layer 22 as a current constriction layer is deposited on a p-type GaAs substrate 21, a p-type GaAs layer 23 is diffused and formed at the central section of the layer 22, and a p-type GaAlAs clad layer 24 constituting a light-emitting layer consisting of a double hetero-junction, a p-type GaAlAs active layer 25, and an n-type GaAlAs clad layer 26 are laminated and grown on the whole surface containing the layer 23. An n-type GaAlAs layer 27, the composition ratio of Al therein is approximately twice as large as the active layer 25 and impurity concentration thereof extends over 1X10<18>/cm<3> or more, is deposited onto the layer 26, an n<+> type GaAs cap layer 28 and an electrode 29 are shaped onto the layer 27, and an optical extracting window 31 is bored to expose one part of the layer 27. An electrode 30 is also provided onto the back of the substrate 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface-emitting type semiconductor light emitting device having a double heterojunction.

[Technical background of the invention and its problems]

Many GaAgAs/GaAs double heterojunction optical devices have been developed so far. In particular, by narrowing down the current path flowing inside the light emitting element, high f4 can be achieved with a point light source.
The development of light-emitting devices that provide high performance is active.

For example, a light emitting device as shown in Figure 2 has been announced (I
EEE Transactions On Compo
nents Hybrid And Manufacture
Aring Technology: Vol.
CHMT-3, No. 4 Dec, 198(J)
. 11 is a p-type GaAs substrate, on which an n-type GaAs layer 12 (=current confinement layer) is selectively formed. GaAj!Aa life fs
A light emitting j- is formed by a double heterojunction in which an H4, n-type GaAAAs cladding layer 15 is laminated one by one. The surface of the n-type Qa IJ As clad fg415 is coated with n-type GaAs for good ohmic contact.
A first electrode 17 is formed on the cap layer 16, and a second plate electrode 18 is formed on the back surface of the substrate 11. The cap layer is removed from above the cladding layer 15, which serves as a light extraction portion, and a light extraction window 19 made of a mouse silicon gland is formed there. The value-added silicon film has a refractive index lower than that of GaAlAs, and therefore can efficiently extract light from the light emitting layer.

However, such surface emitting type light emitting elements have the following problems. In order to obtain a high brightness point source light emitting device,
It is necessary to sufficiently constrict the current path of the element, that is, to make the diameter of the light extraction window 19 sufficiently small (= the diameter of the light extraction window 19) and the current path formed by the first confinement layer 12. tM, the current flowing through the cladding layer 15 and the active layer 1 is
4. The current flow diagonally across the cladding layer 13 (=). Therefore, the current path becomes longer, the series resistance becomes larger, and the operating heart pressure of the light emitting element becomes higher.
Magnetic power consumption increases and effective luminous efficiency decreases.

[Purpose of the invention]

The present invention was made in consideration of the above-mentioned problem, and an object of the present invention is to provide a surface-emitting type semiconductor light-emitting device that shortens the current path, lowers the operating voltage, and thereby realizes a high-intensity point light source. do.

[Summary of the invention]

The present invention is characterized in that a GaAlAs layer with low resistance (l x IQ 17 cm3 or less) and low uaaro is formed on the light emitting layer consisting of a double heterojunction, and the GaAlAs layer is used as a light extraction window. .

〔Effect of the invention〕

Main departure! According to At2, the light extraction window (GaAlAs layer)
s acts as an effective electrode, and therefore the current flowing through the light emitting j- flows not only in the conventional way but also in the slope, effectively shortening the power path. That is, since the series resistance of the element is small, the magnetic actuation pressure is low and there is no unnecessary consumption of magnetic force, thereby controlling the luminous efficiency and obtaining a high brightness point source. In addition, the light absorption is smaller than when the light extraction window is formed of a GaAs shield, and there is almost no reduction in the effective luminous efficiency. Furthermore, since the GaAlAs layer used as the original extraction window can be used as a stopper during etching of the GaAsf layer (catch layer), it is also advantageous in the mounting process.

[Sequence of implementation of the invention] A detailed explanation of the invention will be given below. FIG. 1 shows the construction of an example element. 21 is a p-type GaAs substrate, on which a p-type GaAs 1822 layer that becomes a peek current constriction layer is formed, and a part of it is formed with, for example, Zn diffusion (=therefore, a p-type GaAs layer that becomes a current path). On this substrate (=, as a light emitting layer constituting a double heterojunction,
Type GaAlAs clad + I24. p-type GaAA! As
Active layer 5゜n-type GaAj! As cladding 1ii26 is sequentially laminated.

The k1m ratio of both cladding layers 24.26 is about 6 of that of the active layer 5.
~10 times. Above this light emitting layer (- is n-type GaAlA
The first layer is formed through the s layer and the n+ type GaAs cap layer
4. &4 is formed, and the light extraction part is this nm Ga
A light extraction window 31 made of the same n-type GaA7As thin film as AlAs@2'1 is formed. This n-type GaA
The A1 composition ratio of lAs@27 is about twice that of the active layer, and Ga
When expressed as l-X AIX A3, X is 0.15 or less and its impurity concentration is I x 10"/Cm3 or more. Note that a second electrode force is formed on the back surface of the substrate 21. .

The method for manufacturing this element is as follows. First, a GaAs substrate 21 f=n type GaAa layer n is grown to a thickness of about 5 μm.

The growth method may be either a liquid phase epitaxial growth method or a vapor phase epitaxial growth method. For example, in the case of a liquid phase, a Ga melt containing To and GaAs is spread over the substrate 21 at a concentration of 830 Cm and kept cool.

Using the well-known PEP technology, a mask with openings is formed in the portion that is to become the current path, and Zn is selectively diffused to form a part of the n-type GaAa shield U (=p W GaAa deposit). As a result, a predetermined substrate on which a light-emitting element is formed is obtained.A light-emitting layer is formed by this pseudo-liquid phase emissive growth.In other words, an epitaxial boat equipped with a plurality of semiconductor melt reservoirs is prepared, and The melts for growing the necessary crystals are sequentially arranged in the liquid reservoir.For example, the first melt g
, the reservoir contains Ga100y, GaAs 7.5P,
kl 15LJ u'? , prepare Ge3t,
Second melt reservoir (=, Ga IIJQ f, GaAs
7.5 f, AJ 15 da, Ge3g prepared,
The third melt 1 contains GalυUt + GaAa7.
5f, Al15071+9. 6m9 of Te was charged, and the fourth melt reservoir (Y, Ga 1tlOy, Ga
Aa 7.5t, kl 35"Si' + To
5++19 is charged, and the fifth melt layer (= is Ga 10
0y.

GaAs 25y, Te 61119 are charged.

After raising the temperature of these melt reservoirs and the substrate to approximately 850°C (=), crystal growth was performed by repeating contact and separation for each during slow cooling at a cooling rate of 7 minutes, as shown in Figure 2 (= p
Type GaAlAs clad 7'J 24 , P m-G
aAAAs activity 7m25. n-type GaAlAs +ci where the layer is 1 light extraction layer.
27 + n-type GaAs cap layer 28 (impure!# roughness is 1 x 10"7 m" or more) is completed.

As mentioned above, GaAJAs Norad 24, 24's AA
When the composition ratio is about 6 to 10 times that of the GaAlAa active layer 5, a double heterogeneous layer is formed. In addition, when Al of n M GaAJAs Its which becomes the light extraction layer (0 m composition is expressed as Ga1-, A4 As,
Impurity of W GaAlAs layer, a degree is I x 10”/
In this example, it was 5 x 10"/3 solders.

After this, a TI+ type GaAs cap;
Using PEP technology, a patterned mask pattern is formed in the light extraction area, and selective etching is performed using a mixture of ammonia water, water, and hydrogen peroxide to remove only the n+ type GaAs layer, which is exposed to light. It is assumed that the extraction window 31 is used. The first electrode 14 is made of AuGe, and the second electrode 30 is made of AuGe.
Each is formed from a uZn alloy.

The light emitting device configured in this way has the following structure. A voltage of approximately 2V is applied between the second magnetic poles 4 and 30, and a point light source (=
The reason for the high luminance emission is that the n-type Ga which becomes the light extraction layer
The roughness of the AlAs layer is I x 10”/cIrL3
Because the height is set as above, it is unlikely that the current will flow diagonally (= across) the n-type GaAlA3 cladding layer, and the negative current path will be in the vertical direction, making it possible to lower the excitation rate of the light-emitting element. It is thought that the light extraction window was made of GaAl.
Since the station constructed with As j-axis absorbs less light than the one constructed with GaAs, it is thought that the actual luminous efficiency will not decrease. Ga used as a light extraction window
When the Al composition of AAAs itl< is increased, Al
Since various other problems such as oxidation of aluminum occur, it is preferable that the composition of AI is X≦0.15 when expressed as Ga1- and AJ-As.

In the above, a GaAs substrate was used, but GaAlAs M
A plate can also be used. In addition, the active layer is made of nuGaAs.
Alternatively, the magnetic current confinement layer may be made of GaAlAs. In addition, the present invention can be modified in various ways without departing from its spirit.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a light emitting device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a surface emitting light emitting device using a conventional double heterojunction. 21 ・-p-type GaAs substrate n...n W GaAs layer (magnetic current confinement layer)...p
Type GaAa layer 24...p type GaAlAs cladding layer δ...p type G
aAlAs active layer 26...n-type GaAAAs cladding layer 27...n
Type GaAlAs itA...N-type GaAs cap layer 4...First electrode (capital)...Second electrode 31...Light extraction window (n-type GaAlA, a) Agent Patent attorney Nori Chika Ken, right (and 1 other person) Figure 1 3θ Figure 2

Claims (1)

[Claims] A current confinement layer is selectively provided on a first conductivity type GaAs or GaAlAs substrate, a light emitting layer having a double heterojunction is formed thereon, a GaAlAs layer with a low Al concentration is formed on the surface of this light emitting layer, and Ga on its surface
A first electrode is formed through an As cap layer, a second electrode is formed on the back surface of the substrate, and an A cap layer is formed on the first electrode side.
In a semiconductor light emitting device using a Ga_1_-_xAl_xAs layer with a low l concentration as a light extraction window, the Al ratio of the Ga_1_-_xAl_xAs layer of the light extraction window is set to x≦0.
15 and an impurity concentration of 1×10^1^8/cm^3 or more.