JPH0191479A - Semiconductor light emitting element and its manufacture - Google Patents

Abstract

PURPOSE:To prevent laser oscillation at the time of low temperature or large current, by forming, in a double hetero junction structure body, an absorption layer having energy gap smaller than that of an active layer, and forming thinly a clad layer between the active layer and the absorption layer in thickness equal to or less than 1mum. CONSTITUTION:At least on one side of a double hetero structure body, is arranged an absorption layer 15 whose energy gap is smaller than that of an active layer 9. A clad layer 10 between the active layer 9 and the absorption layer 16 is thinly formed in thickness equal to or less than 1mum. Therefore a light oozing out from the active layer 9 passes through the thin clad layer 10 and reaches the absorption layer 15. Since this light is absorbed by the absorption layer 15, positive feed back of the light does not occur. As a result, laser oscillation becomes hard to occur it the time of low temperature or large current.

Description

DETAILED DESCRIPTION OF THE INVENTION - (Industrial Application Field) The present invention relates to a semiconductor light emitting device and a method for manufacturing the same, and more particularly to an edge-emitting type light emitting diode used for optical communication and the like and a method for manufacturing the same.

(Prior Art) Conventionally, a semiconductor laser is mainly used as a light source for optical communication. This semiconductor laser is used for long-distance, large-capacity optical communications due to its high output, single wavelength, and high response speed. However, semiconductor lasers are expensive and have poor temperature characteristics, making them unsuitable for short-distance, medium- and small-capacity optical communications, and edge-emitting light emitting diodes are used instead of LEDs for this purpose. This edge-emitting type light-emitting diode has a structure similar to that of a semiconductor laser, and only the length of the V-groove portion serving as the light-emitting region is shortened.

A method of manufacturing an edge-emitting type light emitting diode, which is an example of a conventional semiconductor light emitting device, will be described below with reference to the process diagram of FIG. First, as shown in Figure 4(a), Z
N-doped with medium concentration Np: 5XlO”ctIM-3
7. A P-type InP substrate (CP-InP substrate) 1 with a thickness of about 1 μm was grown by liquid phase epitaxial growth. Carrier concentration Np near x 1017cm-3 in n-dog
After forming a P-InP buffer layer 2 on it, a thickness of about 0.5 μm is formed thereon.

Carrier concentration Nn ''' 5 x 101 with Sn dogu
An N-1nP block layer 3 is formed on the top surface with a thickness of about 1.5 ttm and a gear layer concentration Np = s x l□
-InP block layer 4 is grown and formed @ When the above three layers are sequentially epitaxially grown, the thickness of the InP block layer 4 is approximately 600
Carry out at normal temperature of °C. Next, as shown in FIG. 4(b), immediately after the formation of the P-1nP block layer 4, a SiO film 5 is deposited at 350° C. to a thickness of about 1500° by CVD method, and then an IJ process is performed. After that, stripe-like notars with a width of about 1 μm are formed in the <oti> direction using the photoresist film 6, thereby forming an etching mask for the *5×02 film 5.

Next, as shown in FIG. 4(c), etching is performed at about 2° C. using a 3:1 mixed solution of Hα, H, and PO to form a V-groove that penetrates the N-InP block layer 3. form. Next, the Sin film 5 is removed using hydrofluoric acid, and immediately thereafter, as shown in FIG. 4(d), a second liquid phase epitaxial growth is performed by a liquid phase epitaxial growth method.

This liquid phase epitaxial growth was performed using a P-InP cladding layer as a lower cladding layer with a thickness of approximately 1 μm and a carrier concentration of Nlumi 5×1017 cm−”.
(However, λ? is the wavelength of light corresponding to the energy gap of the corresponding layer.), thickness approximately 0.15/jFFJ
P-InGaAsP active layer 9° thick, about 2 ttm wide, about 1.5 μm thick, carrier concentration Nn≧5XIO17 -3
N-InP cladding layer 10 as the upper cladding layer.
N-InGaA with a thickness of about 1 pm and λf=1.2 μm
The sP cap layer 11 is sequentially formed. Then %N −
Au Ge Ni on the InGaA+sP cap layer 11
The electrode 12 is placed on the P-InP substrate l side, and the Au Zn electrode 13 is placed on the P-InP substrate l side.
are each formed to a thickness of about 3000^. After that, Figure 4 (6
), the film 14 of, for example, AZtO is coated on both sides of the device where the optical output is located, using the S.9.
The film is applied to a thickness of 000λ to reduce the reflectance of both end faces.

When a semiconductor light emitting device having such a configuration is energized with the AuZn electrode 13 made of glass and the AuGeNi 11 electrode 12 made negative, the N-InP Glock layer 3 and the P-InP
A reverse bias state occurs at the interface of the block layer 4, and the current is N
- The current flows only through the V-groove etched portion of the InP block J-3, creating a current constriction, and radiative recombination occurs to emit light.

(Problems to be Solved and Attempted by the Invention) However, even with the semiconductor light emitting device and its manufacturing method described above, if the ambient temperature becomes lower and the luminous efficiency of the semiconductor light emitting device improves, or When the current becomes a large current, M, 0.
If only the film 14 allows the light to be emitted to the outside as much as possible, the suppressing power for laser oscillation will be insufficient, and the laser oscillation will start.
The problem is that it has all of the above-mentioned drawbacks, such as the various drawbacks of semiconductor lasers, such as poor temperature characteristics.

The present invention eliminates the problem that the antireflection film alone has insufficient suppressive power for laser oscillation, and provides a highly stable semiconductor light emitting device that does not oscillate even at low temperatures or large currents, and a method for manufacturing the same. The purpose is to provide.

(Means for Solving the Problems) The semiconductor light emitting device according to the present invention is provided with an absorption layer having a smaller energy gap than the active layer on at least one side of the double heterojunction structure, so that the active layer and the absorption layer are connected to each other. The cladding layer in between is thinned to approximately 1 μm or less.

A method for manufacturing a semiconductor light emitting device according to the present invention includes forming a current blocking layer and a V-groove penetrating the current blocking layer on a semiconductor substrate, and forming a double heterojunction structure and at least one side of the double heterojunction structure by filling the grooves. The thickness of the cladding layer in contact with the absorption layer is approximately 1 μm by sequentially growing the absorption layer provided on the
m or less, then a cap layer is grown, and then an alloy metal is formed on the semiconductor substrate side and the cap layer side, respectively.

(Function) According to the present invention, light leaking from the active layer passes through the thin cladding layer, reaches the absorption layer, and is absorbed by the absorption layer, resulting in a positive feed/? No damage occurs, and laser oscillation is less likely to occur even at low temperatures or at high currents.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a process diagram according to an embodiment of the present invention. 1st
In the figure, the parts with the same symbols as in FIG. 4 are the same as those in the conventional one, and each process shown in FIG. 1 (IL) to FIG. Corresponding to the conventional steps in (c), the steps from (1) to removing the 810.degree. film 5 after forming the grooves 7 are the same as the conventional steps, so their explanation will be omitted. As shown in FIG. 2, the chip appearance is schematically shown. The groove 7 is thick and has a length of Ls=l 50 ttm with respect to the total length of the chip, which is 100 μm, and is 350 μm.

Next, as shown in FIG. 1(d), the contactor temperature 59
A second liquid phase epitaxial growth is performed at 5°C. This liquid phase epitaxial growth fills the V-groove 7 to a thickness of approximately 1 μm and a carrier concentration of Nlumi 7×1.
0 "an-" P-InP cladding layer 8. Thickness approx. 0
．． 15 μm, λP=1.3 μm P-InGaAsP active layer 9° thickness about 0.2 μm, carrier concentration Nn≧7X1
017 side-3ON-InP cladding layer 10. Thickness approximately 0.
N-I as upper absorption layer with 5pm, λ2=1.5μm
nGaAsP absorption layer 15, thickness approximately 1 jam, λf=
1.211m of N-1nGaAsP cap layer 1lt-
Grow sequentially. Note that %P-InGaAsP active layer 9
The formation position of the N-InP block layer 3 is inside the V-groove 7.
The location should be on the floor plan.

Further, in this embodiment, N-InP is formed from the P-InP cladding layer 8.
The GaAsP absorption skin 15 is provided so as to fill up to one groove of the absorption tube. After that, N-In was deposited by resistance heating vacuum evaporation.
Au Ge Ni electrode 1 on the GaAsP cap layer 11 side
2f, 3000^ thickness, Au Zn on P-InP substrate 1 side
The electrode 13 is deposited to a thickness of 3000λ and heat treated at about 420° C. in a nitrogen atmosphere to form alloy N. The subsequent step is to perform interosseous surgery to form elements, but since this is well known, the explanation thereof will be omitted.

Next, the operation will be explained. When energized, P-InGa
Light is generated in the AsP active layer 9 as in the conventional case.

A part of this light oozes out to the N-InP cladding layer 10 formed relatively thin and is transmitted to the N-InGaAsP absorption layer 15.
reach. The N-InGaAsP absorption layer 15 is made of P-In
GaAsP has an energy gap lower than that of active N 9 and absorbs the light that reaches it. As a result, the P-InGaAsP active layer 9
Laser oscillation within the double heterojunction structure containing the double heterojunction structure is suppressed.

FIG. 3 is a process diagram showing another embodiment of the present invention, in which the priest portions in FIG. 1 are given the same reference numerals. Structurally P −
A double heterojunction structure in which an InGaAsP active layer 9 is sandwiched between a P-InP cladding layer 8 and an N-InP cladding layer 10 is used as an N-InGaAsP absorption layer 15 and a P-InGaAsP absorption layer 16 as a lower absorption layer. You can get something sandwiched between them. The manufacturing method is the same as the first embodiment until the entire V-groove 7 is formed as shown in FIG. 3(a), and the difference from the first embodiment is as shown in FIG. 3(b)K. Immediately before forming the P-1nP cladding layer 8 and taxially growing the P-InGaAs
Pe, epitaxially grow the condensation layer 16. Other steps are the same as in the first example, except that P-InGaA
The sP absorption layer 16 has a thickness of approximately 0.0 mm. Sμm, λt=1.5
Am, the P-InP cladding layer 8 has a thickness of about 0.1 μmK.
, P-InGaAsP active layer 9 has λF=1,3/
Jmi thickness of about 0.15μm, width of about 2Am, N-InP
The cladding layer 10 has a thickness of approximately 0.1 μm and is made of N-InGa.
AsP absorption layer 15 is λ? =1.5/J? tl, thickness approximately 0
．． 5 μm, N-InGaAsP cap layer 11 is λ
It is formed to have F=1.2 μm and a thickness of about 1 μm.

Further, the growth of the P-InP cladding layer 8 is performed in a state where the degree of supersaturation at the time of contact is 14° C. or higher.

Thereby, meltback of the P-InGaAsP absorption layer 16 can be prevented. In this example, two absorbent layers are used.
The layered structure absorbs light more effectively and suppresses oscillation.

〔Effect of the invention〕

As described above in detail, according to the present invention, an absorption layer having an energy gap smaller than the energy gap of the active layer is formed on at least one side of the double heterojunction structure, and a cladding layer between the active layer and the absorption layer is formed. 1μm thin
Since K is formed as below, a part of the light leaking from the active layer in the vertical direction is absorbed by the absorption layer, making it difficult for laser oscillation to occur, and it is expected that the stability of the semiconductor light emitting device will be improved. .

[Brief explanation of the drawing]

FIG. 1 is a process diagram of a semiconductor light emitting device according to an embodiment of the present invention, FIG. 2 is a schematic diagram of the appearance of a chip according to the above embodiment,
FIG. 3 is a process diagram of a semiconductor light emitting device according to another embodiment of the present invention, and FIG. 4 is a process diagram of a conventional semiconductor light emitting device. In the figure, 1...P-InP substrate, 3...N-InP block layer, 4...P-InP block layer, 7...V
S, S...P-InP cladding layer, 9 = P-I
nGaAsP active layer, 1O---N-InP cladding layer, l 1 =-N-InGaAsP cap layer, l
2- AuGeNi electrode, 13 ・= AuZn electrode,
15-N-InGaAsP absorption layer, l6-P-I
nGaAsP absorption layer ・ Fig. 1 One-shot stop n+,,7゛outerial ffi/), R, ala Fig. 2 Fig. 3 f,i
Figure 4

Claims (3)

[Claims] (1) In a semiconductor light emitting device having a double heterojunction structure in which an active layer is sandwiched between both cladding layers, an absorption layer having a smaller energy gap than the active layer is provided on at least one side of the double heterojunction structure, and the above-mentioned A semiconductor light emitting device characterized in that a cladding layer sandwiched between an active layer and an absorption layer has a thickness of approximately 1 μm or less. (2) a first step of forming a current blocking layer on the semiconductor substrate; a second step of forming a V-groove penetrating the current blocking layer; a lower cladding layer and an active layer filling the V-groove; ,
An upper cladding layer and an absorption layer provided under at least one of the lower cladding layer and the upper cladding layer and having a smaller energy gap than the active layer are sequentially grown epitaxially, and the cladding layer sandwiched between the active layer and the absorption layer is formed. A method for manufacturing a semiconductor light emitting device, comprising: a third step of forming an alloy layer to a thickness of approximately 1 μm or less and epitaxially growing a cap layer; and a fourth step of forming an alloy layer on the semiconductor substrate side and the cap layer side, respectively. (3) When the lower cladding layer is formed next to the lower absorption layer by liquid phase epitaxial growth, the degree of supersaturation of the melt in the lower cladding layer is set at a predetermined temperature that prevents melt-packing of the lower absorption layer. A method for manufacturing a semiconductor light emitting device according to claim 2, characterized in that the above steps are performed.