JPS5952894A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To avoid the surface recombination of an injection carrier preventing an end breakdown from happening to secure high output restraining leakage current to be concentrated in active layers by a method wherein an end forming a resonator is formed into a part made of a crystalline material making the forbidden band width of the material wider than that of the active layers. CONSTITUTION:An N type Al0.35Ga0.65As layer 111, a GaAs layer 112, a P type Al0.35Ga0.65As layer 113, a P type GaAs layer 114 are successively grown on an N type GaAs substrate crystal 10. A P type GaAs layer 114 is coated with An Si3N4 film 16 removing all parts excluding the width W and the length L further removing all the layers down to the surface of the N type GaAs substrate crystal 10 by etching process utilizing the residual Si3N4 film as a mask. Secondly, an N type Al0.5Ga0.5As layer 12 is grown and then the Si3N4 film 16 is removed forming another Si3N4 film 17 again all over the surface while Zn etc. is diffused through the intermediary of a hole opened centering on a strip mesa 11 forming a P<+> type layer 114a and a P type Al0.5Ga0.5As region 121 respectively on the surface of the P type GaAs layer 114 and the N type Al0.5Ga0.5As region 12. Finally after forming a P side electrode 14 and an N side electrode 15, a laser oscillating surface may be formed completing the element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser that can withstand high-power operation and has high reliability.

It is well known that one of the major factors that limits the high output operation of semiconductor laser devices is that the laser end face (cavity face) is destroyed due to high optical output density. The injected carriers stored in the active layer flow out due to the fracture FiV of this end face, the -e plane recombination current, etc., and even if population inversion is realized inside the active layer, population inversion occurs at the end face. However, light absorption occurs, and part of the oscillated light is absorbed near this end face, causing local heat generation. Then, as the temperature rises, the forbidden band narrows, the absorption coefficient becomes larger, and more light is absorbed and heat is generated. Therefore, when trying to obtain high optical output, measures such as providing a separate optical waveguide layer in order to increase the cross-sectional area of the light beam near the end face of the semiconductor laser, and pn Trough (
A possible solution is to create a Trough structure. conventionally,
As an unavoidable method of creating a pn junction on this end face, a crank-type TJS laser [13th Rotating Body Element Conference
: 3-4-2 (1981)" and Wind Strike Gray's (IF; I; E Journal of Qua
ntum Electron QE-17 (1981)
P.

As seen in examples such as 2112), the diffusion process can be devised to create a structure in which there are only 1 and 2 pn junctions on the surface through which light passes or is reflected, or a thin film of each citron-based TFI material can be coated after the end faces are formed. The method used is not used. In addition to the examples described here, most of the currently known h-C semiconductor lasers having a structure including a no-applied resonator have the expanded plane of the crystal as the resonant plane. Therefore, not only is it impossible to know the laser characteristics at the wafer stage, but it is also necessary to go through the process of opening the valve, which has not yet been developed.
It was disadvantageous in terms of mass production. Of course, attempts have been made to form a resonant surface consisting of a pair of parallel planes by chemical etching and eliminate the external process, but a practical technique has not yet been perfected. This is thought to be due to the fact that at least the active layer constituting the laser and the two cladding layers sandwiching it are chemically etched, resulting in poor flatness.

In this invention, the end faces forming the resonator are 1. By forming one crystal with two conductivity types in the area where it exists, it is possible to form a good end face even by chemical etching. ) By making 11t°i wider than that of the viscous layer, the coiling of the injected carrier 11) is avoided to avoid bonding and prevent the end face ff and breakage, thereby achieving high output, and by adding an ingenuity to the configuration of one bond. The aim is to suppress leakage current to the crystal material at the end face of the resonator and to concentrate the current in the oily layer to obtain a semiconductor laser with a high Zu Hi factor.

Figure 1 shows the skin 11 of the first implementation tCU of this issue 1111.
Perspective view showing i configuration, Fig. 2 and Fig. 31XI Vi-
In the detailed cross-sectional views taken along the lines ■-■ and In-1 [[ of Figure 1, respectively, αQ is an n-type GaAs substrate, (1 is a strip mesa portion, and its details will be described later. (1-1) is n-type k
lo, 5Gao, 5A 8 region, (12A),
(12B) is an n-type AZO, 5Gao, 5As region (1
2) The planes that are parallel to each other and that constitute the Noah Appreault resonator are insulating layers, (14) and (I5)
is an electrode.

Then, the strip mesa part (1 inch type AtO, 3
5GaO; 65A8 layer (111), p-type or undoped GaAs activity) ilj (112).

p-type AZo, 35Gao, 6sA 8 layers (113), p
It consists of a +P type layer (114a) formed by diffusing p-type impurities such as GaAe ff4 (114) and Zn, and (121) is an n-type AZo4Ga (1,5A8 region ( p-type Ato, 5Gao formed on the surface of I21,
It is a 5A8 area. The width of this strip mesa portion is w and L (the width is L).

The operation of this laser is as follows. When a forward current is applied by applying a busy voltage so that the electrode (14) is positive and the electrode (15) is negative, K holes and electrons in the active region (112) are confined in a high concentration and recombine by luminescence. The active layer (112) is formed by the n-type At0.35'' 0.65 A8 layer (11
1) and the upper p-type AZo; 3sGaO, esAa layer (
Since the forbidden band width is narrower and the refractive index is larger than that of 113),
Light is guided and amplified along the active layer (112). Then, this light is reflected by iJ 0.0856 at the interface with the n-type AZo, s Ga o, s A8 region (12), but most of it spreads out a little and enters this region (12) and enters the air. interfaces (12A) and (12B) are reached.

Here, the difference in refractive index is large, so about 29% is reflected.
The rest can be released outside. Most of the reflected light then returns to the active layer (112) again and is amplified. In this way, oscillation occurs with the wave light whose amplitude of the reciprocated light is equal to or greater than the original amplitude and whose phase is the same. 'As shown in Problem 31, the viscosity 7@(11
2) and n Ilg AZ o, 5 (Ja o, s A
B From the interface with the g area (12) to the end surface (12A),
Letting the distance 1g IL to (12B) be tA and tB, respectively, n-type Atu, sGag, 5As itt region (l4
The aperture loss caused by the lack of a waveguide mechanism is tA, tB
and also the thickness of (112). However, the thickness of the viscous layer (112) of ) IIN is 0.1
For ~0.2 μm, if tB is expanded to blJm or less, the aperture loss can be reduced to an almost negligible degree. Although not related to the essence of this invention, the length -gL of the striped mesa portion (n) is approximately 300 μm.
One width W is approximately 1 μm. Then, the p-type AZo, sGao, sA day region (12
1) is n-type AZo, sGao, 5A 8 region (
Since a p'n junction with a high diffusion potential is formed at the interface with
Shape, AZo45Gao, 65AB M(113) -n
It flows through the A7-o, a5Gao, and asAB layers (111) and contributes to laser oscillation. Therefore, the laser oscillation efficiency can be increased. Next, the manufacturing process of the first embodiment will be summarized.

Figures 4(a), (c), (e), fg) are partial perspective views at its main stages, and Figures 4fb), (d)
r ff) and fh) are IVB-IVB H, respectively.
#! , IVD-IVD 1tilj, IV F
-IVFN, is an enlarged partial sectional view taken along IVH-IVB line. - First, n-type GaA3 substrate crystal 0
0 on n-type ALo, a5Gao, a5A8 Jt'i
(11,1), GaAs layer (11,2,), p-type At
O,35GaO,'85A8 layer (1+, l, ]) type Ga
Next, on the p-type (yaAB layer (114) [S'1
3N411ffl tlllJ k Temporarily attached and photo-engraved to width W1. The remaining 8i3N4 film is removed at the surface of the n-type GaAs substrate crystal Oq by chemical etching using the remaining 8i3N4 film as a mask.
Figures (c) and (d)]. In this case, the end faces of each layer have different chemical properties and often have a step difference of about 0.1-1 Am. Next, by liquid phase epitaxial growth method, n-type Ato, 5
Grow Gao5AF3 to ρ4. In this case, the strip mesa part (513N4 film on the rice field)
15), no crystal will grow on it, and n-type AZO, 5Gag, 5AB layers 02) will be formed in other parts.
μm + L+ 10) A window with a μm diameter is placed, and p-type impurities such as Zn are introduced through this window at a humidity of 65°C.
After 0 minutes of diffusion, p+ type Jj7 (11-4a) and n-type ALo, 5 were added to the surface of the p-type GaAs layer (114).
On the surface of the Ga, 5As region (12), p-type AZo,
5GEL o , s A e region (12!l) is formed [Fig. 4 (g) and (h)]. Next, p II! is applied using a vacuum deposition method. I electrode (14) and n-side electrode (+57
After forming (omitted in Figure 4), 2 is shown in Figure 4 (g).
A laser resonant surface is formed using X--X lines and Y--Y lines shown by dashed dotted lines, and a semiconductor laser device is completed.

In the first embodiment described above, at the stage of FIG. 4(c) j fdl, the surface of the n-type GaAs substrate crystal QO is etched away, and then the n-type AZo, 5Gao, s AB region B is grown. This is because it is generally difficult to epitaxially grow on the ALaA8 crystal once exposed to air, and the above n-type AZo, 5Gao, and sA8 regions (12)
In the growth process, the oxide film on the AtGaAs layer can be removed by introducing an etching gas such as mci, and epitaxial growth can also be performed on the AtQaAs layer.

FIG. 5 is a perspective view showing the second embodiment of the present invention using this, and FIG. 6 is a cross-sectional view taken along the line ■-■.
Parts equivalent to those in the embodiment are indicated by the same reference numerals. In this second embodiment, the etching for forming the strip forming part (11) was performed using n-type AtO, 35GaO, 65AEI In (I
In addition, in the first embodiment, the n-type Ato, asGELo, 6s A8 layer (1
11), the GaAs active layer (112) was formed directly on E, but in this second example, n-type AZa,
s s Ga o + a s A8 nozu < 1 (115)
This layer D15) acts as a light waveguide layer, and as a result of expanding the beam, the radiation angle is narrowed and the end face (1
2A).

It is possible to improve the efficiency when the light is reflected by the strip mesa portion (12B) and re-enters the strip mesa portion (11). In the first embodiment, a p-type GaAs layer (114) and an n-type AZ'o, sGao, sA8 region (with a Si3N4 film (i-field masked) for diffusion of p-type impurities to the surface area) are used. However, in the second example, Zn was used without using a mask.
By diffusing p-type impurities such as p-type #(l14a)
and n-type AZ. , 5Gao, sA8
'1 iJl area (IZ) p-type AZO, s G
ao,s As N (121) is formed. This is n-type AZo, 5Gao, sA 8 region (12
) The diffusion potential of the p11 junction formed within the pn? , is higher than the diffusion potential of the first embodiment, so that the effect of reducing leakage current in the first embodiment can also be achieved in the second embodiment.

Also, I+! of the first embodiment! The resonant end faces (12A) and (12B) were formed using a good technique, but by selecting the plane orientation of the crystal, for example, a strip mesa was formed in the [010) direction on a crystal with (Joo)]. Part (lI
), Br −C! (A plane perpendicular to the surface can be easily formed using a 30H-based etchant. In this case, if the crystal composition or conductivity type differs, the etching rate will differ and a step will occur at the interface. However, in this invention, both embodiments An extended surface (1) of the active layer (112) from which light is reflected
2A) and (12B) do not have such a portion and have a single composition, so an optical plane can be obtained without creating a step.

Note that 813N4 was used as a mask material in the production of the above examples.
Although a film is used, it goes without saying that a SiO□ or At203 film may also be used. Cd or the like may be used instead of Zn as the p-type impurity, and ion implantation may be used instead of diffusion.

However, reactive ion etching or ion milling may be used for etching, and vapor phase growth or molecular beam epitaxial growth may be used instead of liquid phase growth for crystal growth. Furthermore, although Ga and As-based semiconductors have been described, other compound semiconductors such as nP-based semiconductors may also be used.

As detailed above, in the semiconductor laser according to the present invention, since the third cladding layer is provided in contact with the side peripheral surface of the strip mesa part, there is no layer for absorbing oscillation light on the laser resonant end facet, and the end facet on the optical path Since there is no pn junction in the optical fiber, there is little deterioration of the end face, and the device operates stably with a higher optical output density than conventional devices. still,
A conductive type inversion region is formed in a region of the surface portion of the third cladding layer that is in contact with the side peripheral surface of at least a part of the strip mesa portion (
~, so the leakage current through this third cladding layer is reduced,
Oscillation efficiency also increases. -! Another advantage is that the end face can be formed by etching instead of the process of forming creases, which is difficult for mass production.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic configuration of a first embodiment of the present invention, and FIGS. 2 and 3 are U-U# in FIG. 1, respectively.
and 1) one-view view along line 1■-III, FIG. 4(a). (c), (e), and (g) are partial perspective views of this first embodiment at the main stages of sled construction;
di, (fl, (h) are IVB-IV, respectively
Blli! 3! , 1VD-IVJ) Mori, IVF
-IVF Ia, +vu -IVH, y, rc enlarged partial cross-sectional view, day! FIG. 5 is a perspective view schematically showing the construction of a second embodiment of the present invention, and FIG. 6 is a sectional view taken along the line v1--■ in FIG. In the figure, 0Ill-I'n type GaAs substrate (semiconductor crystal substrate LiI is a strip mesa part, (1?J is 11
type At0.5Ga AS region (third cladding layer),
(111) is no, 5 type 0.350a0.65 As layer (first cladding layer), (112) is GaAs N (active layer), (11
3) is p-type "fl, 35GaO, 65As N (second
cladding layer), (114) is a p-type GaA three layer (cross-layer semiconductor layer), and (121) is a p-type GaAs region (second conductivity type region). In addition, the same reference numerals in the diagram indicate the same or equivalent parts. No. 165512/1971 2 Name of the invention Semiconductor laser 3, 1ili+l(4 and yl(Relationship with patent 71 temporary lji person's representative right side) 111 Jin 8 l'l♂4 agent's address To the east [city f -Yo UU + Marunouchi, I'
+ 12m: 3c; 5. Details of the invention in the specification to be amended! 52. Mei no Kusunoki U6, the details of the amendment are as follows: 1. 'Make a big one.

Claims (1)

[Claims] (1) At least a first
A conductive type first cladding layer, an active layer having a larger optical refractive index than this first cladding layer and a narrower forbidden band width, and a second conductive type optical layer having a smaller refractive index and wider forbidden band width than this active layer. the second of
A cladding layer and a surface semiconductor layer of a second conductivity type having a narrower forbidden band width than the second cladding layer are sequentially stacked,
A portion of the surface semiconductor layer, the second cladding layer, the active layer, and at least the first cladding layer in the annular direction is shaped so that a region of a predetermined width W and a predetermined length −JL remains. A third ground layer of the first conductivity type having a wider forbidden band width than the active layer is formed so as to be in contact with the side peripheral surface of the strip mesa part, and the length L of the active layer is In a semiconductor laser whose optical resonant surfaces are two parallel end surfaces of the third cladding layer on an extension of the direction, at least the area of the surface portion of the third cladding layer that is in contact with the side circumferential surface of the lip mesa portion. A semiconductor device characterized in that a second conductivity type region is provided in the semiconductor device.