JPH02275689A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain lateral mode characteristic and emitting light of high quality with excellent noise characteristic by a method having small number of steps by providing a mesa shape in a region substantially coincident with a region on a stripe, and forming a second conductivity type light absorption layer on a second conductivity type clad layer. CONSTITUTION:A mesa stripe 7 is formed in a region substantially coincident with a stripe region 10 on a substrate 1. After a mesa stripe is formed, a cap layer 6 is grown on a p-type clad layer 5, and a p-type electrode 8 and an n-type electrode 9 are further formed. Thus, crystal growths may be only twice, a current narrowing is conducted by an inverted layer 2 formed of the surface of the substrate, and lateral mode control of laser oscillation light is performed with the layer 6s at both side of the stripe 7 as light absorption layers. Thus, a structure for obtaining a laser light of lateral mode characteristic and excellent noise characteristic, high quality can be easily realized in a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a semiconductor laser, and more particularly to a device structure for manufacturing a device that oscillates high-quality laser light using a manufacturing method with a small number of man-hours.

[Conventional technology]

Semiconductor lasers used as light sources for optical discs, laser printers, and the like are required to have a basic mode in which the shape of the emitted light beam is stable and to be able to focus the light onto a minute spot. For this purpose, several structures have been adopted especially to control the transverse mode in the horizontal direction of the junction. An example of a structure that has traditionally been adopted as one of the best (IEICE, 1982 Semiconductor and Materials Division National Conference (Kumamoto) Lecture Proceedings Paper No. 297) is shown in Figure 3, A1
FIG. 2 is a schematic structural diagram of a light emitting end face of an example of a Ga I nP visible light semiconductor laser. (Al2.), 4 Ga(,,6)0.5Ino, on the n-type GaAs substrate 101
5P cladding layers 102, 104, Ga (1,5Ino5
A double heterostructure consisting of a P active layer 103 is formed, p (Alo, b GaO, 4)0.9 I n
Both sides of the o5P cladding layer mesa stripe portion 107 are n-GaAs light absorption layers 106 which also serve as current blocking layers. Furthermore, a p-Q a As cap layer 108 for forming a p-electrode is formed on these. 109 is a p-type electrode, and 110 is an n-type electrode.

[Problem to be solved by the invention]

In the conventional structure shown in FIG. 3, the conductivity type must be reversed to that of the p-type cladding layer in order to perform current confinement using GaAs light absorption N106. Further, the cap layer, which is a contact layer with the electrode, must be of the same conductivity type as the p-type cladding layer. Thus, the n-type GaAs light absorption layer must be selectively formed avoiding the p-type cladding layer mesa stripe 107, and the p-type cap M108 must be formed so as to be in contact with the p-type cladding layer mesa stripe 107. . For this purpose, a double heterostructure growth process up to the p-type cladding layer, a GaAS absorption layer selective growth process,
Conventional structures require a complex manufacturing process and require many man-hours, as they require three crystal growth processes, such as the GaAs cap layer growth process, and selective growth with strict growth condition constraints. There was a drawback.

Furthermore, since the current confinement region is uniquely determined by the light absorption layer, it is difficult to independently control the current injection width and the refractive index waveguide structure, making it difficult to provide a structure with excellent noise characteristics. It has the disadvantage of being

The purpose of the present invention is to solve these problems and provide a semiconductor laser that can produce a structure that provides high-quality emitted light with excellent transverse mode characteristics and noise characteristics using a manufacturing method that requires fewer man-hours. It's about doing.

[Means to solve the problem]

In the semiconductor laser of the present invention, on the upper surface of the substrate of the first conductivity type,
A second conductivity type inversion layer is formed except for a part of the stripe area, and a first conductivity type cladding layer, an active layer of the first conductivity type or an intrinsic type or a second conductivity type, and a second conductivity type inversion layer are formed on this substrate. A double heterostructure is formed by sequentially forming cladding layers, and the cladding layer of the second conductivity type has a mesa shape in an area that almost matches the striped area on the substrate, and a second cladding layer is formed on the cladding layer of the second conductivity type. It is characterized by the formation of a conductive type light absorption layer. In order to obtain an A, &GaInP visible light semiconductor laser with this configuration, the substrate of the first conductivity type is made of GaInP.
As, the cladding layer of the first conductivity type (AρyGax-y
) s-y I no, 5 P (0<y≦1) the active layer of the first conductivity type or the intrinsic type or the second conductivity type (AJ7
x Ga1-X ) 0.5 I no5P (0≦x
< 1) + second conductivity type cladding layer (AiyG
a+-y') 0.5 I no, P (0<y'≦1
), the absorption layer of the second conductivity type is made of GaAs.

Note that it is not limited to ApGaInP-based visible light semiconductor lasers,
GaInPAs system, AllGaAs system, AI Ga
Sb-based or Zn5eS-based materials may also be used.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. FIG. 3 is a schematic side view seen from the light emission direction. A, ff An example of a GaInP visible light semiconductor laser is shown.

Leaving a striped region of about 7 μm wide on the surface of the n-type GaAs substrate 1, zinc (Zn) is selectively applied to the other regions.
is diffused to form a p-type GaAs region 2. ρ-type GaA
In order to form the s-region 2, impurities other than Zn, such as beryllium or cadmium, may be used regardless of the type of impurity. Further, the formation method is not limited to the method, such as ion implantation method other than diffusion. The thickness of p-GaAs region 2 is 1 μrn
degree. On this substrate, a 1 μm thick n-(Affl
O,4Ga0.6) a,s I no5P cladding layer 3, 0.1 μm thick Ga,),5 I nO,5P
Active layer 4, 1 μm thick p (Afflo4Gao6)
o, s I nO, and 5P cladding layers 5 are sequentially formed to form a double heterostructure. Suitable forming methods include metal organic pyrolysis vapor phase epitaxial method (MOVPE method) and molecular beam epitaxial method (MBE method), or any other method may be used. Next, p(A
, Ro4Ga0.6)0. A mesa stripe 7 of 5P is formed. The formation method is a photolithography method. 4Ga. 6) o,s I no5P
By masking only the stripe forming region on the cladding layer 5 with a resist film, the other portions are etched using a mixture of hydrochloric acid and hydrogen peroxide as an etching solution to reduce the thickness of the cladding layer to about 0.3 μm. After forming the mesa stripe, a p-GaAs cap layer 6 is grown to a thickness of about 2 μm on the p-cladding N5. The growth method is MOVPE method,
In addition to the MBE method, any method such as a liquid phase epitaxial method (LPE method) or a halogen transport vapor phase epitaxial method (HT-VPE method) may be used. Further, an n-type electrode 8 and an n-type electrode 9 are formed by a vapor deposition method or the like. In this way, crystal growth only takes two steps. Current confinement is performed by the inversion layer 2 formed by the Zn diffusion formed on the substrate surface, and the transverse mode control of the laser oscillation light is performed by the p-GaAs on both sides of the mesa stripe 7.
This is done by using the cap layer 6 as a light absorption layer.

FIG. 2 shows a second embodiment of the invention. FIG. 3 is a schematic side view seen from the light emission direction. Only the stripe region 10 with a width of 3 μm is left on the n-GaAs substrate, and beryllium (Be) is ion-implanted into the other regions to form a p-inverted Be ion implantation [11] with a thickness of 0.5 μm. As described in the first embodiment, in order to form a p-inversion layer, other elements and other formation methods may be used, but in order to form narrow stripes and a deep high concentration layer, Ion implantation of a light element such as Be is suitable. Next, 1.0 μm thick n-Al1.5 I
no, 5 P cladding layer 12, undoped active layer 4 with a thickness of 0.06 μm, p-(AJlo4G
ao, 6) o, s I no, s P first cladding layer 13, p-Affl with a thickness of 0.5 μn, ), 5In. ,
P second cladding layer 14, p-Ga with a thickness of 0.1 μm)
, 5 I no, 5 P 15 are sequentially formed. Next, pGa(1
, 5I no, 5 P layer 15, P-AJI (1,5In
The 05P layer 14 is removed by etching. By using double cladding layers 13 and 14 with different A4 compositions,
Etching can be selective, and mesa structures can be easily formed with good reproducibility. Furthermore, by making the compositions of the cladding layers A1 on the p-side and n-side asymmetrical, the light intensity distribution in the direction perpendicular to the junction is optimized, and high-output operation is also possible. Subsequently, a p-GaAs cap layer 6 is applied over the entire surface with a thickness of about 2
Formed with a thickness of μm. Further, an n-type electrode 8 and an n-type electrode 9 are formed to form an element structure. By making the stripe width 10 on the substrate, which defines the current injection width, narrower than the mesa stripe width 7, a low-noise device that does not cause self-pulsation operation can be realized. pGaQ,5I
The n09P layer 15 is made of GaAs and Al0.5I nQ,
5 P has the role of surface antioxidant layer. This structure can be realized by growing the crystal twice in the same way as described in the first embodiment.

Because the device process centered on growth is simplified,
The time required to manufacture the device can be reduced by about one-fourth compared to conventional structures without impairing device performance. Further, in the second embodiment, the noise can be reduced by the return light compared to the conventional structure, and the RIN value at the time of 2% return sales is reduced by about 10 dB/Hz.

It goes without saying that the present invention can also be applied to the above embodiments in which the n-type and p-type are replaced. Also, Aj
! Materials other than GaInP-based materials, GaInPAs
system, A, RGaSb system, A, RGaAs system, Zn5eS
The present invention can be applied to any type of material, such as HgCdTe type, HgCdTe type, or other materials.

〔Effect of the invention〕

As described above, according to the present invention, a semiconductor laser having a structure capable of obtaining high-quality laser light with excellent transverse mode characteristics and noise characteristics can be easily realized in less time than before.

[Brief explanation of drawings]

FIG. 1 is a schematic side view of the first embodiment of the present invention viewed from the light output direction, FIG. 2 is a schematic side view of the second embodiment of the present invention, and FIG. 3 is a conventional structure for light output. It is a schematic side view seen from the direction. 1.101-...n-GaAs substrate, 2-...-Z n diffusion layer, 3,102-n-(A, Ro4Ga(,,6)0
゜In(,, 5P cladding layer, 1, 1.03... undoped GaO, 5I nO, 5P active layer, 5, 104...
p-(AJo,sGa,),6) 0.51 n
o, 5P cladding layer, 6,108-p-GaAs key +
r Tube layer, 7... Mesa stripe region, 8, 10
9...p-type electrode, 9,110...n-type electrode, l
O... Stripe region on substrate, 11... Be ion implantation layer, 12... Affl, ), 5 I no, 5
P cladding layer, 13-p-(Ajo, 4 Ga,), 6
) 0.5 I no, 5 P first cladding layer, 14
=-p-Af□, 5 I n. , 5 P second cladding layer, 15.105...p Ga0.5 I nO, 5
P layer, 106 =-n-GaAs light absorption layer, 1
07-p - (Afo, a Ga, ), 4) o, s
I na, +s P mesa stripe.

Claims (1)

[Claims] A second conductivity type inversion layer is formed on the top surface of the first conductivity type substrate except for a part of the striped area, and a first conductivity type cladding layer, the first conductivity type or intrinsic type or the second conductivity type inversion layer is formed on the substrate. A double heterostructure is formed in which an active layer of a conductivity type and a cladding layer of a second conductivity type are sequentially formed, and the cladding layer of the second conductivity type has a mesa shape in a region that almost coincides with the striped region on the substrate; Furthermore, a semiconductor laser characterized in that a second conductivity type light absorption layer is formed on the second conductivity type cladding layer.