JPS594185A - Semiconductor light emitting device and manufacture thereof - Google Patents

Abstract

PURPOSE:To increase the light output of a semiconductor light emitting device by providing a layer structure including a layer made of one conductive type aluminum gallium arsenide having aluminum mixed crystal ratio larger than aluminum gallium arsenide forming an active layer, a current blocking unit containing a reverse bias junction to a light emitting unit in such a manner that the contacting surface between the active layer and a clad layer is raised at the clad layer side and the reverse bias junction surface is coincident to the surface for partitioning between the active layer and a guide layer. CONSTITUTION:A lower clad layer 8 made of N type aluminum gallium arsenide including up to 1X10<18>/cm<3> of Te as an N type impurity, and a layer 9 made of N type aluminum gallium arsenide including up to 1X10<17>/cm<3> of Te as an N type impurity are sequentially formed in a hole 7. The end face of a current blocking unit 3 is covered with aluminum (Al) oxidized film, and since a semiconductor layer is hardly grown on the end face, the upper surface of the layer 8 and the upper surface of the layer 9 can be accurately coincident at the reverse bias junction surface. Then, an upper clad layer 11 made of P type aluminum gallium arsenide including up to 1X10<18>/ cm<3> of Mg as a P tye impurity is formed to the region covering the current blocking unit.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a semiconductor optical device having a multilayer structure made of aluminum gallium arsenide. Specifically, it is a semiconductor light emitting device with a double heterostructure, which is formed in a region sandwiched between current blocking parts having a reverse bias junction, and has a light emitting part in which an active layer and a guide layer are sandwiched between upper and lower crat layers. The present invention relates to an improvement of the device and a method of manufacturing a semiconductor light emitting device having such a structure.

(2) Background of the Technology The optical output of a semiconductor optical device is determined depending on the product of the current exceeding the threshold current and the voltage.

Therefore, in order to increase the optical output of a semiconductor light emitting device, it is effective to reduce the threshold current and increase the active layer volume.

On the other hand, there is a relationship between the threshold current density and the active layer thickness.
A proportional relationship exists within a certain range, and there is a thickness of the active layer that minimizes the threshold current density. Therefore, the thickness of the active layer is generally selected to minimize this threshold current density, for example 0 in the case of aluminum gallium arsenide (Alo, +(3a o, 9 As)). The thickness is selected to be about .08 (μm).

Further, increasing the thickness of the substantial light emitting region is effective in increasing the light output of the semiconductor light emitting device.

In order to realize this requirement, the concept of a guide layer has been introduced, and it is known that a large optical output can be obtained while maintaining a low threshold current density.

Furthermore, one of the factors that determines the threshold current is a current that does not directly contribute to light emission (hereinafter referred to as reactive current), and efforts have been made to reduce this reactive current for some time.

In the prior art, a method has been proposed in which the optical path of the active layer is sandwiched between current blocking parts including reverse bias junctions.
It has been confirmed that it is sufficiently effective.

(3) Prior Art and Problems As mentioned above, there are optimum conditions for the thickness of the active layer in a semiconductor light emitting device. However, since the demand for increasing the optical output of semiconductor-based optical devices has become increasingly urgent in recent years, it is natural that efforts to find solutions by increasing the width of the active layer has been done.

However, a so-called Veri-rad heterostructure (Ruried heterostructure) in which the active layer is embedded within the cladding layer
(terostructure) In a laser, when the width of the active layer is increased, the optical output increases until the width reaches 2.5 [μIn], but when the width exceeds 2.5 [μIn], it becomes a higher order mode and is no longer suitable for practical use. .

Furthermore, there is a limit to the effectiveness of the current blocking section, which is effective in reducing the threshold current, and there is still room for further improvement.

(4) Object of the Invention The object of the present invention is to meet these demands for improvement, and to provide a structure in which an active layer and a guide layer having a thickness that minimizes the threshold current density are sandwiched between upper and lower cladding layers. A semiconductor light-emitting device comprising: a light-emitting part having a layered structure; a current blocking part including at least one reverse bias junction surface on both sides of the light-emitting part; both end faces not used by the current blocking part are light-emitting end faces; In the device, it is possible to increase the total effective current value without causing higher-order modes of current, and as a result, the optical output is increased, and the current blocking effect is large, and the reactive current is reduced, resulting in Another object of the present invention is to provide a structure of a semiconductor-based optical device having a large optical output, and a method of manufacturing a semiconductor light-emitting device having such a structure.

(5) Prior structure The structure of the present invention is (a) formed on the first (lower) cladding layer made of -conductivity type aluminum gallium arsenide (AlxGa1-xAs), and -conductivity type aluminum gallium arsenide. (Al y Ga I=yAs), an active layer formed on the guide layer and made of aluminum gallium arsenide (Al z Qa 1-z As ), and an active layer formed on the active layer. Aluminum gallium arsenide of opposite conductivity type (AlxGa1-x, As)
x representing the mixed crystal ratio of the aluminum (A1),
y% z (1) There is a relationship of x>y>z≧0, and aluminum gallium hy% (
It has a layer structure including a layer of aluminum gallium arsenide X (Alv(ja+-vAs)) of conductivity type, which has a larger aluminum (81) mixed crystal ratio than Alz(ia+ -zA, s). , a current blocking part including a reverse bias junction with respect to the light emitting part, and a contact surface between the active layer and the second cladding layer has a shape convex toward the second cladding layer, A semiconductor optical device; 9; On a substrate made of gallium oxide ((↑aAs)), an aluminum wire (Alu(3)) of the opposite conductivity type is
A current blocking lower layer made of aluminum gallium arsenide (AlxGa1-
Aluminum gallium arsenide (At via
1-vA,s) to form an Ichihara blocking intermediate layer,
Aluminum gallium arsenide (1-1-(3a+-vA
Aluminum gallium arsenide (A, Iw (ton νv1~S
) or a current blocking part upper layer made of 1 um of arsenide, and forming a light emitting part by combining the current blocking part upper layer, the current limiting part intermediate layer, the current blocking part lower layer, and the upper layer part of the substrate. Aluminum gallium arsenide (A, 1xQa + -x As ) having a -
Aluminum gallium arsenide (1yG) having one conductivity type is formed on the lower cladding layer.
A guide layer made of aluminum gallium arsenide (A, 1zGa+-) is formed on the guide layer.
An active layer made of aluminum gallium arsenide (A, IxGat-xAs) having an opposite conductivity type is formed on the active layer, and an upper cladding layer made of aluminum gallium arsenide (A, IxGat-xAs) having an opposite conductivity type is formed on the active layer. forming positive and negative electrodes on the lower surface of the substrate, respectively, and a bonding surface between the current blocking lower layer and the current limiting intermediate layer is a surface separating the active layer and the guide layer. x, y, z, representing the mixed crystal ratio of aluminum (A1),
The method of manufacturing a semiconductor light emitting device is characterized in that the values of u, v, and W are selected so as to satisfy the following relationships: x>y>z≧Q, uSv≧Z1, and w<z.

Furthermore, in the configuration (a) above, (c) setting the width of the active layer to 5 [μIn] or less is effective for preventing the generation of higher-order modes. Furthermore, the above (a) and ()
In the configuration of 1), (d) the thickness of the guide layer is 0.5~
It is more advantageous to set the thickness of the upper and lower cladding layers to 0.8 [μm1 or more.

In the configuration of -1- (b), (e) the thickness of the current limiter intermediate layer is made extremely small and the opening for forming the light emitting dish is formed, and then the opening of the current limiter intermediate layer is Forming a slight recess in the region is more effective for making the upper surface of the active layer upwardly convex and for aligning the lower surface of the active layer with the reverse bias junction surface of the current blocking section.

The present invention provides a method for manufacturing a semiconductor light emitting device, in which a substrate"
It is better to form the light emitting part after forming the current blocking part at -.
This method takes advantage of the well-known fact that the yield and reliability of equipment are better than the process, and that semiconductors with a high aluminum (A1) content are easily oxidized, and such semiconductor layers It is said that a thin film of aluminum oxide (A, l 203) tends to be easily formed on the end face of the aluminum (A, l 203), while it is difficult to grow a compound semiconductor on the end face covered with such aluminum (A1) oxide. Based on known laws of nature, in a semiconductor light emitting device having the basic structure as described above, the current blocking portion is formed in at least three layers, and only the middle layer is made of aluminum (
A1) The mixed crystal ratio is large, the aluminum (A1) mixed crystal ratio in the lower layer is relatively small, the aluminum (AI) mixed crystal ratio in the upper layer is particularly small, including zero, and the intermediate layer and the active layer are If the layers are made to face each other and the lower surface of the intermediate layer becomes a reverse bias junction surface, the current stop intermediate layer made of a semiconductor with a high aluminum (A1) mixed crystal ratio on the inner surface of the opening for forming the light emitting section It is difficult for the semiconductor forming the active layer to grow on the end face of the opening, so when the guide layer and active layer are successively grown in this opening, the interface between the guide layer and the active layer must be exactly aligned with the reverse bias junction surface. It was completed by embodying the idea that the active layer has an upwardly convex shape. Then, x, y, zSu, v, which represent the mixed crystal ratio of aluminum,
The value of w is x)y)z≧0.1'', V≧Z and w<z
It has been experimentally confirmed that it is most effective when selected to satisfy the following relationship.

(6) Embodiments of the Invention Hereinafter, a method for manufacturing a semiconductor device according to an embodiment of the present invention will be explained with reference to the drawings, and the structure and unique effects of the present invention will be clarified.

Refer to FIG. 1. First, current blocking portions 2.3.2', 3', 4.5 form. This step can be carried out using a liquid phase epitaxial growth method, with Mg as an n-type impurity at -1,X 1018/c
p-type aluminum gallium arsenide (p-A,
Layer 2 consisting of Io, aQao7A, s) is 0.5 [μ
m] thickness, and then an n-type aluminum gallium arsenide (rr A, I O, 5Qao, 5As) containing Te as an n-type impurity (RR A, I O, 5Qao, 5As)
Form a layer 3 with a thickness of about 0.2 [μIn],
Next, Mg is added as an n-type impurity to ~IXIO18/cm
3 containing p-type aluminum gallium arsenide (p-Al o3
Qa Q,? The layer 2' consisting of As) is 1.5 [μ+n)
Then, Te is added as an n-type impurity to ~1
Layer 3 made of n-type aluminum gallium arsenide (n-Al o,s Qao6As) containing ×1018/c1n3
Next, a layer 4 made of p-type gallium arsenide (p-0aAs) containing ~5 x 10 / cm of Mg as an n-type impurity is formed to a thickness of 0.5 [μm].
Finally, as an n-type impurity,
A layer 5 made of n-type gallium arsenide (n-Qa A,s) containing ~5 × 10 / can of 0.5 [μIn
] Thickness is sequentially formed.

Refer to FIG. 2. A light emitting portion formation lower layer reaching the upper layer of the substrate 1 is formed in a part of the current blocking portions 2.3.2', 3', and 4.5. In this process, a silicon dioxide (Si02) film 6 formed on the entire surface of the substrate 1 is used as a protective film and a mask.
SO4: H2O2: H2O= 1: 6: 1
(25° C.) as the etching solution.

Refer to FIG. 3. A light-emitting HIS 8.9.10.11 is formed in the open lower part described above. This step can be carried out using a liquid phase epitaxial growth method, starting with Te as an n-type impurity.
A lower cladding layer 8 consisting of n-type aluminum gallium arsenide (n −, AI o, s Qao5As) containing ~IXIO/c+, followed by an n-type aluminum gallium arsenide ( A layer 9 consisting of n-A, IO, 7Qao, 5As) is formed. Here, the end face of 3 is aluminum (A
Since it is covered with the oxide film I) and it is difficult for a semiconductor layer to grow on this end face, the growth of the cladding layer 8 is first stopped at the end faces 3 at both ends of the opening. As the growth continues, the upper surface of cladding layer 8 becomes the reverse bias junction surface (junction surface between 2 and 3).
The line will be exactly aligned with the line. Subsequently, the guide layer 9 is grown, and the guide layer 9 has a thickness of 1.5 [μ+n
), this guide layer covers the end face of 3 and 2'
After covering, growth stops at the 3' end face. As the growth continues further, the upper surface of the guide layer 9 becomes the reverse bias junction surface (2 and 3
It coincides exactly one point with the joint surface) and becomes a - line. After that, when the active layer 10 begins to grow, the active layer 10 takes on an upwardly convex shape. Further, the active layer 10 is of p type or n type.
Either type is fine. The thickness of the convex active layer at its thickest point is 0.05 [μmn:] −Q, 2[μ+n
], so it does not grow up to region 4. After that, Mg is added as a p-type impurity to ~l X 10/can
containing p-type aluminum gallium arsenide (p-AIO
, 5Qao, sAs)
1 is formed up to the area covering the current blocker part, and the light emitting part 8.9
．． Complete 10.11.

See Figure 4 Positive and negative electrodes 12 and 13 are formed on the light emitting section.

In this step, titanium/platinum/gold (Ti/Pt/Au) is deposited on the upper cladding layer 11 using a sputter growth method.
) This can be carried out by forming a triple layer to form the positive electrode 12, and forming a gold germanium (AuQe) alloy layer on the lower surface of the substrate 1 using a vacuum evaporation method to form the negative electrode 13.

According to the above process, first, it is possible to form the active layer in an upwardly convex shape. is effective in increasing the total effective current value, and as a result, it becomes possible to increase the optical output. Furthermore, since the interface between the active layer and the guide layer can be aligned with the reverse bias junction surface in the current blocking section, the current blocking effect is increased and it becomes possible to suppress reactive current to a minimum. However, if the width of the active layer is further increased beyond 5 [μm], there is a risk of causing higher-order modes, so it is effective to keep the increase in the width of the active layer to about 5 [μm] or less. . This is because the flat region of the upper surface of the active layer is about 2.5 [n].

Furthermore, if the thickness of the lower cladding layer is less than 0.8 [μIn], the light from the active layer will seep into the substrate and be absorbed, resulting in a large loss of light, resulting in a causes a significant increase in

In addition, in order to reduce the radiation angle of light in the direction perpendicular to the junction, the thickness of the guide layer must be 0.5 [μ11] or more, but if the thickness exceeds 2.0 [μIn] (then the active layer The proportion of light that enters the window becomes smaller, resulting in a significant increase in the threshold current density.Therefore, the thickness of the lower cladding layer is reduced to 0.8
[μIn] or more, the thickness of the guide layer is 0.5 [μIn) ~
2.0 [μIn] is appropriate.

Furthermore, on the inner surface of the current-limiting intermediate layer provided opposite to the active layer, that is, the layer made of a semiconductor having a high aluminum (Al) mixed crystal ratio, the light-emitting portion is formed.
Providing a recessed portion is more effective in accurately aligning the lower surface of the current-limiting intermediate layer with the interface between the active layer and the guide layer.

(7) Effects of the Invention As explained above, according to the present invention, the active layer and the guide layer have a thickness that minimizes the threshold current density.
A light emitting part having a layered structure sandwiched by lower cladding layers, and a current blocking part including at least one reverse bias junction surface on both sides of the light emitting part, and both end faces not covered by the current blocking part. In a semiconductor light emitting device in which the light emitting edge is a light emitting facet, it is possible to increase the total effective current value without causing a higher order mode of current, and as a result, the optical output is increased. It is possible to provide a structure of a semiconductor light emitting device in which current is reduced and a large optical output can be obtained as a result, and a method of manufacturing a semiconductor light emitting device having such a structure.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views of a substrate after completion of main steps in a method of manufacturing a semiconductor light emitting device according to an embodiment of the present invention. 1--- ・One substrate (I+-(,'laA,s), 2
．． 3.2; 3', 4.5...Bending current blocking part (, I)-8lo, a QaO, 7A, s, n-Al 0.5
(iao6As, p-A, Io3Qao7As, n
-AIo, 5Qao, sAs, p-Q; IA, s, n
-GaA, s16...Silicon dioxide (Si
(J) Film, 7... Opening for forming light emitting part, 8...
...lower cladding layer (n-Al o5Qao, sA
, s), 9-...-guide layer (n-A, lo
3QaO,7As), 1Q-・--active layer (n
or p-Alo, +(3ao9As), 11...
... Upper cladding layer (p-AIo5Qao5As
), 12...Positive current 4m (Ti/Pt/A
n), 13... Negative electrode (,AuGe). Figure 3 Figure 4

Claims (1)

[Claims] Aluminum gallium arsenide (AlxGa+
-xAs) formed on the first cladding layer, -
Conductive type aluminum gallium arsenide (xtyGa r
-yAs ) and aluminum gallium arsenide (Al zQa 1- ) formed on the guide layer.
an active layer consisting of aluminum gallium arsenide (AlxQa+
-xAs) and a light-emitting part made of a second cladding layer made of
There is a relationship between x > y > and z≧0, and aluminum gallium arsenide (AlzG
Aluminum gallium arsenide (A I
The current blocking part has a layer structure including a layer made of (vGal-vAs) and includes a reverse bias junction with respect to the light emitting part, and the contact surface between the active layer and the second cladding layer is 2. A semiconductor light emitting device having a convex shape on the cladding layer side of No. 2, and wherein the reverse bias junction surface coincides with a surface separating the active layer and the guide layer. (Aluminium gallium arsenide of the opposite conductivity type (AluQax
- uAs), and on the current blocking lower layer, an aluminum gallium arsenide of one conductivity type and having a higher aluminum mixed crystal ratio than aluminum gallium arsenide constituting the current blocking lower layer is formed. (Alv.
forming a current limiting intermediate layer made of (Ga+-vAs);
Aluminum gallium arsenide (A, IwGa+-wA) having a lower aluminum mixed crystal ratio than aluminum gallium arsenide constituting the current limiting intermediate layer is disposed on the current limiting intermediate layer.
s) or forming a current blocking part upper layer made of gallium arsenide, and forming the current blocking part upper layer, the current limiting part intermediate layer, the current blocking part lower layer, and the upper layer part of the substrate into a region where the hollow part is to be formed. Aluminum gallium arsenide (Al
A lower cladding layer made of aluminum gallium arsenide (AlyGa+ - (AIzQa+-zA,s) is formed in an upwardly convex shape, and aluminum gallium arsenide (A-1xGal-XA) having an opposite conductivity type is formed on the active layer.
forming an upper cladding layer consisting of S), forming positive and negative electrodes on the upper cladding layer and the lower surface of the substrate, respectively, and bonding the current blocking lower layer and the current blocking lower layer; The plane corresponds to the plane separating the active layer and the guide layer, and x represents the mixed crystal ratio of the aluminum,
The values of y, z, u, v, and w are x>y>z≧0.1
1,■≧2. and w < z.