JPS60239079A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a laser having a large output by growing a laminate, in which double hetero-junction structure is held doubly by a guide layer and a clad layer, to a substrate with a projecting section in uniform film thickness along a projecting surface and forming a striped electric conduction layer to the upper section of the projecting section. CONSTITUTION:The (100) face of N-GaAs 10 is etched to form a projecting section 12, each layer of an N-Al0.38Ga0.62As clad 13, an N-Al0.25Ga0.75As guide 14, an N-Al0.5Ga0.5As clad 15, a non-added Al0.15Ga0.85As active layer 16 in predetermined thickness, a P-Al0.5Ga0.5As clad 17, a P-Al0.35Ga0.75As guide 18, an Al0.38Ga0.62As insulating clad 19 and a P-GaAs cap 20 is grown in the vapor phase in uniform thickness, a Zn diffusion layer 12 reaching to the guide layer 18 is shaped to the upper section of the projecting section, and the insulating layer 19 is converted into a P layer and used as a carrier injecting region. Injecting carriers are injected concentrically to the active layer from the diffusion layer 21 and the projecting section of substrate 10, and confined in the layer, thus enabling laser oscillation having high efficiency at a low threshold, then obtaining a large output.

Description

[Detailed Description of the Invention] Technical Field> The present invention relates to a semiconductor laser, particularly a high optical output semiconductor laser. <Prior Art> A visible light semiconductor using a crystal material such as AA()aAs/GaA-s. Since lasers are small and can perform continuous oscillation at room temperature with low power consumption and high efficiency, they are suitable as light sources for optical digital audio discs (I) AD) and are being put into practical use. The demand for this visible light semiconductor laser as a light source for optical writing in optical printers and the like is increasing, and in order to meet this demand, research and development of visible light semiconductor lasers that can withstand large optical output oscillations is underway.

Recently, in order to meet the rapidly increasing demand for these visible light semiconductor lasers, mass production has begun. AA' (JaAs/GaAs Visible Light Semiconductor Laser Manufacturing Method) Liquid phase epitaxy has traditionally been used in this field.In contrast, vapor phase epitaxy using organic metals has been used.
,Metalorganic ChemicalVap
our Deposition (abbreviated as MOOVD)6
1. It is now one of the most important technologies for manufacturing original devices because it combines mass production and precision film thickness control. Special D Peace (R4゜T),
1) upuis) and Davicus (L', D,
Dapkus) and Applied Physics Letter magazine (Applied Physics, 1r.
etter) 1977, Vol. 31, 47.466-4
Since it was announced on page 68, its practicality has attracted attention and MOOV
Research on GaAs/GaAs visible semiconductor lasers using the D method has been carried out6). Among them, AjGaAs with transverse mode controlled wavelength λ = 0.78 μm.
/GaAs visible light semiconductor laser device, for example, by Nakatsuka, Ono, Itamura, and Nakamura in the 44th Academic Conference of the Society of Applied Chemistry, 1983, p. 109, 26 p-P-1.
As typified by a paper published under the title ``Controlled Semiconductor Laser'', it is possible to provide absorption layers on both sides of a striped region adjacent to the active layer. The current plan is to absorb the light leaking from the active layer into the absorption layer and create a loss region, and to create a gain-loss step between the striped region without the absorption layer and perform transverse mode control. It is being prototyped.

However, in the above structure, fundamental transverse mode oscillation occurs only up to an optical output of 5 to 7 mW, and although an absorption region is built in to provide a gain-loss step, the threshold current becomes high in this absorption region because the source becomes a loss. In addition, it has drawbacks such as the asymmetrical emission beam, making it impractical as a light source for DAD, and making it impossible to oscillate a large optical output.

<Object of the Invention> The object of the present invention is to eliminate the above-mentioned drawbacks, fully utilize the features of the MOOVI (MOOVI) method, and achieve not only low-threshold, high-efficiency laser oscillation, but also stable fundamental transverse mode oscillation, which enables large optical output oscillation. Therefore, it is possible to provide a semiconductor laser which can be produced relatively easily by one-time growth and has excellent reproducibility and reliability using a concentric light source and a γ-light source.

<Structure of the Invention> Structure of the semiconductor laser of the present invention A first cladding layer is provided on a semiconductor substrate having a convex shape, and a first cladding layer is provided adjacent to the cladding layer and has a refractive index lower than that of the cladding layer. Adjacent to the active layer is a second active layer having a layer thickness of approximately several times the wavelength in the tube or less, and second and third layers having a thickness approximately the same as the active layer and made of a material with a wider band gap than the active layer. The double heterostructure sandwiched between the cladding layers of No. 3 and No. 3 has a refractive index smaller than that of the active layer. Second. A multilayer structure further sandwiched between first and second guide layers made of a material with a refractive index higher than that of the third cladding layer is provided, and adjacent to the multilayer structure is electrically insulated and is higher than the kite layer. It has an I@groove structure in which a fourth cladding layer made of a material with a low refractive index is provided, and each growth layer has a form in which it is grown with a uniform layer thickness along the convex portion of the convex substrate, and The fourth cladding layer is characterized in that a striped electrically conductive region is formed on the convex region of the convex substrate.

<Example> The following is a detailed explanation of the present invention with reference to the drawings. is a cross-sectional view of this example during manufacturing. The manufacturing method of this embodiment is as shown in FIG.
The S r 02 film is left in the form of a stripe with a width of 2 μm in the direction, and an outer window is opened, and etched to a depth of 1.0 μm using a mixed solution of Br2 and methyl alcohol. At this time, in the [OH] direction ζ, a convex region 12 having a convex normal mesa structure is formed in the remaining region of the 5in2 film 117i.

Next, after removing this 5102 film 11, the n-type AlO,3
8GaO, 62A s first cladding layer 135:0.5
μm, t1 type AA O, 25G a O, 75As
The thickness of the first kite layer 14 is 1.0 μm.

n-type Alo, s Ga o, sAs second cladding layer 15 at 0.051 tm, undoped A lo, +s
QaO, 85As active layer I6f 0.04 μm
, p-type A# 0. +i Ga O, 5As third cladding layer 1'I0.05 μm, I) Type A 140.25 G
a O, 75A, s Second guide layer 18 1.0μ
m, AA o, as Ga 0.62AS insulating fourth cladding layer 197i-0,511m, p-type Ga
A cap layer is continuously grown to a thickness of 0.5 μm using the M O [3V D method.

Regarding the above growth ζ, the conventional liquid phase growth method is a method in which a melt with controlled composition is prepared for each growth layer and the substrate is moved to grow each layer. Not only is the growth of such a multilayer structure extremely difficult, but also 4! It is impossible to control the thickness of each layer of the r composition. On the other hand, the MOOV TJ method is a vapor phase growth method using organic metals, so by changing the composition of the mixed gas, it is possible to easily grow pigeons of any composition into any multilayer structure. The growth of the structure can be easily and easily controlled.

Moreover, the M U OV D method allows thin 11Q growth and has precise film thickness controllability. can be grown with good control of layer thickness. M
As mentioned above, the OOVD method is one of the vapor phase growth methods, so when forming the fourth cladding layer 19, it is easier to mix a small amount of oxygen gas than Al0138Ga0062.
Asp edge layer 19 can be formed, and MOOVD
In this method, fine particles of each composition grow while bonding, so there is no dependence on the plane orientation of the growth, and the growth is uniform in thickness in all directions. Therefore, as in the structure of the present invention, the number I on the convex substrate is
Even if the i1 layer is grown, a layer with a large thickness will continue to grow along the shape of the convex portion.

Then p-type () a A s cap layer 20 is grown on the surface
After forming the SIO2 ridges, a convex shape 4 is formed using a photoresist method.
The width of the 5i02 film 2H is 2 μm to match the convex area of &.
Open the window and spread the zinc inside the second guide.
It diffuses in a dense manner (diffusion region 21). The fourth insulating cloud layer in the region where zinc has been diffused is converted to p-type to form a striped carrier injection region. Next 5i
By removing the O2 cavity, forming a p-type ohmic contact 22 on the entire surface of the GaAs cap layer, and attaching ζn-type ohmic contacts 2 and 3 on the substrate side, a semiconductor laser having the structure of the present invention can be obtained (No. Figures 1 and 2).

<Function of the invention/A result> In the structure of the present invention, the current injected from the entire surface electrode spreads over the entire surface of the cap layer 20 and flows, but there is an insulating fourth cloud layer 19 adjacent to the cap layer 201. Therefore, the p-type second guide plate 18 is injected from the strip-shaped carrier injection region, which is blocked there and converted to p-type by zinc diffusion. The current flows from the second guide layer 18 to the second
The active layer 161 is implanted through the cladding layer 17. The gear 11a injected into the active layer 16 diffuses in the horizontal and lateral directions of the active layer, and because the gain distribution is relatively thin, it originally spreads widely in the vertical direction from the active layer. Fourth, in the structure of the present invention, the active layer has a thin second layer. 3rd Clad Shizu [Continued from the 1st part]
．． Since the light is sandwiched between the second guide layers, the light passes through the first guide layer, which has a relatively large refractive index. It is drawn into the second guide layer and widely spreads in the vertical direction centering on the active layer. In this case, as in this embodiment, the second cladding layer 15 and the third cladding layer 1i
! If the layer thicknesses of the first guide layer 14 and the second guide layer 18 are made equal (and the layer thicknesses of the first guide layer 14 and the second guide layer 18 are made equal), the composition and thickness of each layer will be symmetrical with respect to the active layer in the vertical direction, so that the light will spread. is more encouraged.

(9) In the structure of the present invention, as shown in FIG. 2, the active layer is sandwiched between the third cladding layer 17ζ and the second guide layer 1 in the horizontal direction O.

Therefore, the light of the active layer has a different refractive index in the horizontal and lateral directions, and a positive refractive index guiding mechanism that focuses the light on the active layer and creates a positive refractive index distribution cannot be created. In general, when both ends of the active − are sandwiched between cladding layers with a low refractive index and are rubbed together, the positive refractive index distribution becomes thicker than 1, and as a result, the −-order transverse mode oscillation may be caused by +h ll+ . Therefore, in order to suppress this, it is necessary to narrow the width of the active layer. In contrast, in the structure of the present invention, the third cladding layer adjacent to both ends of the active layer is thin, so that light is influenced by the second guide layer. Since the refractive index of the second guide layer is higher than that of the cladding layer and the difference in refractive index with the active layer is relatively small, the height of the positive refractive index distribution created in the horizontal and lateral directions of the active layer can be made relatively small and stable. Fundamental transverse mode oscillation can be maintained over a wide range of current injection regions.

As in the structure of the present invention, the active layer is the second and third (10) Being sandwiched between cladding layers has the following effects.

In other words, as mentioned above, when the original seepage in the vertical direction of the active layer is large, the light confinement coefficient (fil
A large amount of injected carriers is required to cause telelaser oscillation with a small ling factor. At this time, when the active layer is sandwiched between cladding layers with a wide bandgap as in the structure of the present invention, the injected carriers are confined within the active layer and effectively recombine, resulting in laser oscillation at a relatively low threshold. Start. In particular, in the structure of the present invention, current is injected into the second guide layer adjacent to the third cladding layer only from the striped carrier injection region. By putting the front of the diffusion region 21 deep into the second kite layer, the lateral spread of the current in the second guide layer and the third cladding layer can be reduced, so that the injected current effectively contributes to laser oscillation, resulting in a low threshold value and a high Performs efficient laser oscillation. The structure of the present invention, which is traditionally sandwiched between an active layer and a cladding layer with a wide band gap, can reduce the product of carriers leaking vertically from the active layer even when the temperature rises, making it suitable for high-temperature operation. It can withstand the force of the vehicle and improve the reliability of the device.

As in the present invention, by increasing the seepage of light from the active layer, the light confinement coefficient (fillingfa) in the direction perpendicular to the active layer is increased.
Reducing ctor ) has a significant effect on high optical output laser oscillation. Ordinary AlGaAs/GaA,s
When a semiconductor laser is caused to oscillate with a large optical output, a phenomenon occurs in which the reflective surface is destroyed. This phenomenon has long been known as optical damage, and its level is ~I in OW laser oscillation.
Occurs at MW/lii. Normally A 1t (3a A s
/G a As semiconductor laser, the optical output P at which the reflective surface is destroyed is determined by the layer thickness of the active layer being d and the confinement coefficient (fil
ling factor) is r, and the spot size of 1)z mode is W and l, and pM increases in inverse proportion to F.

When using the structure of the present invention, r≦0. υ11kopspM″>
100 mW becomes possible, and high optical output laser oscillation becomes possible.

By increasing the seepage of light from the active layer as in the present invention, the spread angle θ1 in the direction perpendicular to the active layer can be sharply reduced. In particular, as in this embodiment, if the set W of the cladding layer and the guide layer sandwich the active layer in the vertical direction ζ of the active layer, and if the layer thicknesses are equal, the light will be broadly symmetrical in the vertical direction ζ with the active layer as the center. It can be expanded to As a result, using this embodiment, it is possible to set θ±≦15 degrees.

This 11. On the other hand, in the horizontal and lateral directions of the active layer, a relatively strong positive refractive index guiding mechanism is built-in, so the spot size of the lateral mode is narrowed and the spread angle θ//l of the active layer in the horizontal and lateral directions is set to θ, , = 12 to 15 degrees.

Therefore, it is possible to obtain a concentric light source, and in practical use, the coupling efficiency with an external optical system can be significantly increased.

As mentioned above, the structure of the present invention is similar to that of the laser described in the 44th Japan Society of Applied Physics Academic Conference Proceedings, 1983, p. 109, 26 p-1'-16, by Nakatsuka, Ono, Kajimura, and Nakamura. This is completely different from the mechanism that controls the transverse mode (13) by providing a loss region, and since there is no loss region, laser oscillation can be performed with a low threshold and high efficiency.

Furthermore, it can be manufactured with a growth of 1 mm, the manufacturing method is relatively easy, such as using an electrode on the entire surface, and it can be manufactured with good reproducibility by taking advantage of the good controllability of layer thickness peculiar to the MOOVT method.

As mentioned above, the embodiments have been described with respect to the A, /GaAs/GaAs double heterojunction crystal material, but other crystal materials such as InGaAsP/InGaP, InGa
P/AA! InP.

InGaAs'P/1nP, AA! GaAs8b/Ga
Many crystalline materials such as AsSb can be applied.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a cross-sectional view of FIG. 1, and FIG. 3 is a cross-sectional view when a convex region is formed on a substrate in the process of manufacturing this embodiment. Figure 10--n-type GaAs substrate, 1]--8i 0
．． Film, 12... Convex region, 13-- n-type At
! 0.380B O,62AS first cladding layer, 14
・”-n-type Alo, 250a0.75ks 1st force (14) id layer, 15 ・=-n-type Alo, s Ga o
, s AsSecond Clad Mausoleum, 16-=-Undoped A
l o, +s Q30, 75 As active layer, 17...
...p-type AlO, 5()a o, s As third cladding layer, 18...p-type Al 0025 Qa o
, 7Asi2 '77 t' N, 19-- A/
o, ss Ga 0062 As p-type fourth cladding layer, 20... p-type Ga As key 91 layer,
21... Zinc diffusion region, 22... P type ohmic contact, 23-- N type ohmic contact. (15)

Claims (1)

[Claims] A cladding layer of ml is provided on a semiconductor substrate having a convex shape, and an active layer having a refractive index higher than that of the cladding layer and a layer thickness not more than several times the tube wavelength is adjacent to the cladding layer. A double heterostructure sandwiched between second and third cladding layers made of materials with a band gap wider than that of the active layer and having a thickness similar to that of the active layer is formed. 1st. Second. The third cladding layer is made of a material having a higher refractive index than each of the third cladding layers. A multilayer structure further sandwiched between the first and second guide layers is provided, and a fourth layer is provided adjacent to the multilayer structure and is electrically insulated and made of a material having a refractive index smaller than that of the guide layer. The layer structure has a layer structure in which each growth layer has a uniform layer thickness along the convex portion of the convex substrate, and the convex region of the convex substrate within the fourth cladding layer. A semiconductor laser characterized in that a stripe-shaped electrically conductive region is formed in a region corresponding to the upper part of the semiconductor laser.