JPS5988889A - semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To facilitate the liquid epitaxial growth of a clad layer and an active layer by a method wherein a Ga1-xAlxAs current block layer and a GaAs photo absorption layer are laminated and grown on a GaAs substrate, a groove in band form coming into the substrate from the surfaces of the layers is bored, and, while it is filled, a Ga1-yAlyAs clad layer and a Ga1-xAlxAs active layer are provided over the entire surface. CONSTITUTION:The P type Ga0.7Al0.3As current block layer 22 and the P type or N type GaAs photo absorption layer 23 are laminated and grown on the N type GaAs substrate 21, and the V-groove in band form coming into the substrate 21 from the surfaces thereof is formed. Next, while this groove is filled, the first clad layer 24 of N type Ga0.65Al0.35As, the non doped Ga0.95Al0.05As active layer 25, the second clad layer 26 of P type Ga0.65Al0.35As, and a P type GaAs cap layer 27 are laminated and grown over the entire surface. Thereafter, a P-side electrode 28 and an N-side electrode 29 are provided respectively on the front and back surfaces.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a semiconductor light emitting device, and in particular, to a semiconductor light emitting device, in particular, a refractive index light guide and a light absorption layer that selectively provide loss to harmonics by changing the thickness of an active layer. Accordingly, the present invention relates to a semiconductor laser in which stable substrate transverse mode oscillation can be obtained.

(b) Background of the Technology In the technology of using light as an information signal medium in optical fiber communication and various industrial and consumer fields, the laser diode is the most essential and fundamental component. When using semiconductor lasers in these various fields,
Progress has been made in many aspects of semiconductor lasers, such as linearity of current-optical output characteristics, directivity of output light, increase in output, and stability of axial mode and transverse mode.

For example, in order to maintain the waveform during transmission, and also from the viewpoint of coupling efficiency between the light source and the fiber, the fundamental principle of optical fiber use is that volume modes are required, and semiconductor lasers require a stable fundamental transverse mode. Achieving this has become a serious issue.

(C) Conventional technology and problems In order to stabilize the oscillation transverse mode of a semiconductor laser, pn
It is effective to form a so-called refractive index waveguide mechanism, which gives an equally constrained refractive index distribution also in the direction parallel to the junction, in the laser active region 6.

One method of forming such a refractive index waveguide mechanism is to increase the thickness of the active layer of the laser by 1' in the width direction of the resonator. In other words, it is already known that 1st IJI, 1st 4th, and 1st 4th century, in which the origin of the crab was shaped like a lens.

, Figure 451 (a) is a single view showing the active layer i of the conventional lens, Figure 51 (b) is the distribution of the equivalent refractive index] Figure 1, 1 (a) ]・6, is a chart shown as follows.

In Figure 11 (a), 1 is n-type or p;! ! i! !
Ga+ -xAM The thickness at the central part A of the two layers 1 of living oranges is 120 cr 1 m) and the thickness at the end H is 50 cr (
nm).

The wavelength λ of the oscillation light in the previous example is 7so (nml), and the refractive index is Ga+-xAP, xA, which constitutes the entire active layer 1.
s is nx==3.592; cladding J@2 and 3 constitute Ga+-yAQyAs are ny=3. As shown in the chart of FIG. 1(b), the isolateral refractive index of the active layer L is maximum in the middle heat section A, which is the thickest part of the boat, and the thickness and the end B! At H, nB=3°370.

A force-1 refractive index waveguide mechanism is established by the distribution of the equivalent refractive index in this way, but in order to oscillate only the fundamental transverse mode in this conventional j′Jll 9ζ, the active Jfft
The width W of the lens-shaped portion of 1 is about 1 [μm''1 or (
It is necessary to reduce σL to a value lower than that, which is extremely difficult to realize industrially.

A semiconductor light emitting device provided with a light absorbing layer, which will be described below, is already known as a means to avoid this problem and realize the basic bucket mode. Figure 2 (a) is a cross-sectional view showing the main part of a semiconductor laser provided with a light absorption layer, and Figure 2 (b)
is a diagram showing the electric field strength distribution of oscillation light, 2nd] [C]
is a chart showing the isolateral refractive index distribution of the active layer, Figure 2(d)
is a diagram showing the distribution of loss due to the light absorption layer, and the second
The horizontal axis of the chart in Figure (b) and Perfection (d) is the cross section of Figure 2 (a).
Corresponds to the figure.

In FIG. 2(a), 11 is an active layer with forbidden band width E+ and Mi refractive index n1, and 12 is forbidden band width JjE2+refractive index n2.
13 is the forbidden band width E3 + no 1)
(Second cladding layer with refractive index n3, 14 is yarn control band iME
4, a light absorption layer having a refractive index of n4. The above-mentioned 3-E4 and the refractive indexes n and n4 of the 1st corner E and 14 of the 3-Tanishi body layers 11 to 14 fully satisfy the relationship shown in the following equation.

PJ2 + EB > 1! :1>I'E4n+
> nt > n2* ns As shown in FIG. 2(a), the active layer 11 is located in the resonator width direction,
That is, it has a lens-shaped cross section with the maximum thickness at the center l'i 0M in the left-right direction of the non-sectional view, and the thickness gradually decreases as it moves away from the center. With this shape, the active layer 110 has an equivalent refractive index of 14 (Fig. 2(C)).
As shown in Figure 2 (b), the solid line I is the maximum at the center of the instep.
The wave is guided as the fundamental mode shown by , and the primary mode shown by heartbeat 1. In other words, the 11th first! X1(a) and (b)
The resonator width is set to be wider than the resonator width W at which the four fish modes become a single fundamental mode as described with reference to .

The light absorption layer 14 is formed by completely excluding the vicinity of the center of the active layer 11 and the left and right ends of this cross-sectional view. It is located close to i1~ and via 4-rathod N112'. That is, as shown in FIG. 2(b) K, the energy of the fundamental mode is almost concentrated near the center, and the energy of the higher-order mode has a higher density on the left and right sides than near the center. The higher-order modes can be selectively attenuated by providing a loss distribution as shown in FIG. 2(d) by providing an interval between the peak positions of or a slightly larger interval. In addition, in the region giving this loss, the thickness of the cladding layer 12 interposed between the active layer 11 and the light absorption layer 14 is set within the width of the light seeping out from the active layer 11.

The above configuration suppresses the oscillation of higher-order modes and stably excavates the fundamental transverse mode, but in semiconductor lasers that effectively absorb this light, the back layer
It's not easy to do. That is, according to the structure shown in FIG. 2(a), the light absorption layer 14 is made of GaAa, and the active layer 11.
Is it possible to form the first cladding layer 12 and the second cladding layer 13 by setting the selected composition ratio of GaAAAs? A s , 4 - G made in the form j) y, in contact with I in 枦 or GaAs no.
An aAs epitaxially grown layer.

A band-shaped groove with a v'4-shaped cross section 14B is formed on this by anisotropic etching, It is difficult to limit the shape of the boar in the area to the area where the light absorption effect is shown in the M diagram, and the change in the cross-sectional shape of the groove!
l! 7I, which results in variations in the shape and dimensions of the cladding layer and the host layer, making it extremely difficult to industrially manufacture a semiconductor laser in which this light absorption layer functions effectively.

(d) Object of the Invention The present invention is based on the invention. G a A s /C a in which an active layer, etc. is formed on a band-shaped nodal circle formed on a glass substrate.
The overall purpose is to provide a semiconductor laser W1 in which a single fundamental transverse mode oscillation is realized by providing an optical absorption layer that can be easily applied industrially to the AItA a optical semiconductor laser.

(e) Structure of the Invention The object of the present invention is to generate a GaAs current of the second conductivity type [51
One stop ivy and Ga in contact with the Ga+-zAItzAs layer
and an As light absorption layer are disposed in sequence, and a band-shaped part extending from the upper surface of the GaAg light absorption layer to the GaAs substrate is provided;
A first conductor t B in contact with the groove surface and the GaAs light absorption layer.
9. This is achieved by a semiconductor light emitting device in which a Ga+-xMxAs (0≦X(y,z) active layer is provided via a Ga1-y1'JLyAs cladding h4).

(f) Embodiments of the Invention The present invention will be explained in detail below with reference to embodiments shown in FIG.

In the figure, 21 is nu, GaAs substrate, 22 is p-type Ga o, y A! o, sAs 4 flow blocking layer, 23 is p
or naGaAs light absorption layer, 24 is n-type GaO,a
sMo, a sAs first cladding layer, 25 is undoped Ga0.95"0.05A, s active layer, 26 is p-type Gao, asAgo3sAs second cladding layer, 27 is p
Type Q a, A s cap, 28 is the p-side electrode, 29
indicates the n-side electrode.

An overview of the method for producing and preparing 7-1 practical examples will be explained. No change, n-type G
The (]00) plane of the aAs crystal is the upper surface of the substrate 21, and p-type Gao7A is grown on the surface by liquid phase epitaxial growth.
The Ao3As' current blocking layer 22 has a thickness of, for example, 0.5 [μ
[pain], then p! The 8νGaAs original absorption layer 23 is formed to have a jψ of e4IN, for example, 0.5 to 1 [μm].

The GaAs light absorption layer 23 and QaO, 7A1o
, and reaches the substrate 21 through the aAs current limiting current blocking layer 22.

■It has one shape lock and is fully formed in the <011> direction of the crystal. The width of this groove is about 3 [μm] in the example of the GaAs light absorption layer 230'.

Next, a second liquid phase epitaxial growth was carried out,
n-type GaO,6s All o3s As first clad Jso24, GaO,95AI', o, o sAs activity &25) P-type Ga o,65Aj! o,s sA
s second cladding) ¥126 and l) type GaAs#Yanobu layer 27) are formed as a primary layer. n-type Gao with, s s/
uo, 55As During the liquid phase epitaxial growth of the first cladding layer 24, the GaO, 7AQo, and aAs backs lowered under the GaAs light absorption layer 23 are actively utilized, and Gao, asAI! o, asAs The inner groove part of the first cladding layer and the part above the GaAs original absorption layer 23 are continuous,
Moreover, the shape of the groove does not change on the sloped portion of the GaAs original absorption layer 23 when the thickness is less than about 0.3 μm.

'! fc-, Gao, esAAo, osAs activity I@2
5 is Ga o, a s Al! o, asAsvgl In contact with the cladding layer 24, the central thickness is, for example, 80 to 15
By completing the liquid phase epitaxial growth close to 0 [nm], the cross section becomes lens-shaped, but the width of the GaA
The growth of the above-mentioned type 27 of s-element absorption J\j23 is similar to the conventional technique, and steps such as electrode formation and inter-fold formation are also performed according to the conventional technique.

The embodiment described above has a cladding layer (J), (J'), and (6) formed in the groove having a V-shaped cross section.
The present invention can be implemented in the same manner even if the shape of T is other shapes such as a U-shape or an inverted trapezoid.

(g) Effects of the invention As described above, according to the present invention, GaAs/Ga
911L is extremely difficult for MAs type half-body sensors.
The liquid phase epitaxial growth of the cladding layer and the active (:'F) layer became easier, improving reproducibility and productivity.
It becomes possible to industrially produce a semiconductor generator canopy that provides stable fundamental transverse mode oscillation.

[Brief explanation of the drawing]

Figure 1 (a) is a cross-sectional RFF1 diagram showing the main parts of a semiconductor laser according to the prior art, Figure 1 (b) is a diagram showing an example of the isolateral refractive index distribution, and Figure 2 (a) is the original absorption layer. Section Ifj diagram showing the main wall portion of a semiconductor laser having
(b) is a diagram showing the distribution of oscillated light;
C) is a diagram showing the distribution of isolateral refractive index, 2nd:, ゛+
(d) is a chart showing the loss distribution, and the 31st chart is a chart showing one example of the center 1iit of the present invention.
, 7Mo, s A s ′+ as flow blocking layer, 23 as GaA
s light absorption layer, 24 is Gao, a s A11), a
sA s% #1 cladding layer, 25 is Gao, g5uO
, OFI As active layer, 26 is Gao, asAAo,
an asAs second cladding layer, 27 a GaAs cap layer,
28 and 29 indicate electrodes. f 1 illustration 2 illustration///3

Claims (1)

[Claims] On the GaAs substrate of the first conductivity type, the second conductivity type. ! 4 electric type ■a1
- z Al z A s as a flow prevention layer and the Ga1-z
A GaAs light absorption layer in contact with the AQzAs layer is sequentially disposed, and a strip-shaped tile is provided that reaches the GaAs substrate from the upper surface of the GaAs original absorption layer, and a 14th electric type in contact with the groove surface and the GaAs light absorption layer is provided. Ga+-xAAxAs (0≦X<y, z
) A semiconductor light emitting device comprising an active layer.