JPS599991A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a laser device having excellent characteristics and a long life, by providing a semiconductor layers, whose impurity diffusing speeds are different to each other, between a connecting layer and a upper clad layer, thereby narrowing the width of effective stripe shaped current path with good reproducibility. CONSTITUTION:Between an N type Ga1-yAlyAs clad layer 4 and an N type GaAs connecting layer 5, N type GaAs 9 and N type Ga1-zAlzAs 10 (z>0) are laminated. With respect to GaAlAs, the larger the Al crystal mixing ratio, the faster the diffusion speed, in P type impurities such as Zn. When Zn is diffuzed from the upper side of the N type GaAs 5 and P layers 11a and 11b are formed, the are a of the P layer in the layer 10 becomes wider than the area of the P layer in the layer 5. The width of the remaining N layer becomes narrower in the layer 10, which is closer to an active layer than the layer 5. Thus the width of a current path becomes gradually smaller toward the inside. An Al crystal mixing ratio (z) of the layer 10 is hardly affected by the oscillating characteristics of the laser itself and can be adjusted to a desired value. In this constitution, a device, which is characterized by a small threshold level, a stable lateral mode, no degradation in crystal property, and a long life, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser device, and more particularly to a structure that can narrow the effective stripe width of a gain guide type stripe semi-enveloped V-laser device that oscillates in longitudinal multi-mode with good reproducibility. It is something.

In recent years, the development of semi-integrated laser devices has been remarkable, and in particular, not only transverse single mode oscillation but also slope single mode oscillation has been realized with various strut and wave structures using Mf refractive index guides. It is entering the period of practical use in the field of industrial use. However, laser devices with longitudinal single mode oscillation have problems such as the fact that noise is likely to occur due to light returning to the laser device itself, and mode competition noise occurs due to longitudinal mode transitions when temperature changes. Especially in the consumer field where video discs, audio discs, etc. are used over a wide temperature range, it is said that longitudinal multi-mode laser equipment is more suitable than longitudinal single-mode laser equipment because these phenomena do not occur. It is being said.

On the other hand, various gain guide type stripe laser devices without a refractive index guide are known as structures of semiconductor laser devices that emit longitudinal multimode oscillation. Figure 1 is a cross-sectional view showing the structure of one example of a conventional stripe laser device in which stripes are formed by ainlation diffusion of zinc (Zn), etc. (11 is a gallium arsenide made of p-film crystal). (GaAs) substrate, t2), (
3), p-type gallium aluminum=r7 moo arsenic (Ga1-yAtyAs) cladding layer, p-type Gal arsenic (Ga1-yAtyAs) cladding layer formed sequentially by, for example, liquid phase epitaxial growth on a GaAs substrate (11), respectively.

AlxAe active layer, n-type Ga1-yAtyAe layer 77
) fl -n-type GaAs contact layer (y ) x ).

A p-type impurity such as Zn is selectively diffused from the surface of the n-type contact layer (7) so as to leave a stripe-like region, and the diffusion front stops in the middle of the n-type rad layer (4). and two p-type diffusion regions (6a) +
(6b) (Dotted diagonal lines are applied to the figure to show the formation of 9. (7) and (8) are GaAs substrates) and p-type diffusion regions (6a) + (6t)), respectively. The n-type layer aA is a gold scrap electrode formed on the contact layer (5).

In this conventional device, electrode (8) Pi: versus electrode i
When a voltage is applied so that 71 has a positive potential, the pn junction Ja+Jb between the p-type scattering layers (6a), (6b) and the n-type contact layer (5) and n-type rad layer (4) becomes Being reverse biased, the current flows only through the striped regions of the n-type contact layer (5) and the n-type rad layer (4), sandwiched by the p-type diffusion regions (6a), (6b). flows. At this time, electrons are intensively injected from the n-type LAD layer (4) and holes are intensively injected from the p-type LAD layer (2) into the vicinity of the striped region of the active layer (3). Since recombination is formed, the injected carriers and light are confined in the active 1m(3)'4, and when the current is sufficiently increased, the laser beam is activated at a certain threshold current. Oscillation starts. If this winding is wide, the width of the current path through which the current flows (in other words, the width of the striped area 7J) is wide, the transverse mode of oscillation will not be in the fundamental mode (zero-order mode), but will have two in the near-field image. There is a problem in that bright spot peaks appear. According to fC, which has recently become clearer, the effective stripe width must be very narrow (
(For example, if the thickness is 5 μm or less), the transverse mode is stabilized to a considerable optical output level after the start of oscillation, and a semiconductor laser device with excellent characteristics without so-called kinks appearing in current and optical characteristics can be obtained.

However, in the semiconductor laser device with the conventional structure shown in Fig. 1, it is difficult to narrow down the effective stripe width with good reproducibility (sufficient).
A) and (6b) are formed by diffusing p-type impurities such as ZN from the surface of the contact layer (5) using silicon nitride [(Si3N4) etc. as a mask. The diffusion shape of the active layer (3) is determined by the diffusion front caused by lateral diffusion. The effective stripe width also depends on the position of the vertical diffusion front of the p-type diffusion regions (6a) and (6b) in the n-type rad layer (4). However, since the diffusion rate of p-type impurities such as zn in the n-type rad layer (4) is high, it is difficult to control their position so that they are in the same place with good reproducibility. This is especially possible by setting the oscillation wavelength to visible light, and by setting the ht
If the content ratio is increased, the diffusion rate of Zn etc. becomes even faster, which becomes a problem. Furthermore, in the conventional structure shown in FIG. 1, the diffusion front is relatively close to the active layer (3), so that distortion and deterioration of crystallinity caused during diffusion may adversely affect the life of the device.

This invention was made in view of the problems described above in the conventional stripe laser device in which stripes were formed by isolation diffusion.
The purpose of the present invention is to provide a structure in which the effective stripe width can be narrowed with good reproducibility without causing the problem of υ crystallinity deterioration by forming a conductor layer for a semiconductor layer.

FIG. 2 is a sectional view showing one embodiment of the present invention.

Portions equivalent to those of the conventional example in FIG. 1 are designated by the same reference numerals. In this example, n-type Ga 1-yAlyAθ
Between the cladding layer (4) and the n-type GaA3 contact layer (5), an n-type aAs layer (91 and an n-type Ga1-ft
zAθ layer (IQ is formed. (However, z>0) As is well known, for tg-Ga-A7-As crystal, p-type impurities such as zn are not present in a layer with a large At mixed crystal ratio. , the diffusion rate is faster than in a layer with a small ht mixed crystal ratio.

Therefore, in FIG. 2, the n-type layer aAθ contact 1m F5
Zn is diffused from the surface of J to form a p-type diffusion region (lla
).

(nb), n-type Ga 1-ZAtZ AS
Since the diffusion rate of the four sides of the layer is faster than that of the n-type layer aA contact layer (5), the n-type Ga 1-2A7zAS layer [11
The area of the p-type diffusion region formed within the n-type GaAe contact layer (5) is larger than the area of the p-type diffusion region formed within the n-type GaAe contact layer (5). Therefore, in the structure of FIG. 2, the width of the remaining n-type robust region is closer to the active layer than the n-type GaAs contact layer (5).
The width of the current path becomes narrower toward the inside than the surface.The n-type Ga1-2AtzAB layer (I
Since the A7 mixed crystal ratio of Q has almost no effect on the oscillation characteristics of the laser device itself, it can be adjusted to a desired value depending on the diffusion conditions and the stripe width of the diffusion mask.

Next, the role π of the n-type aAs layer (9) will be described. When manufacturing a semiconductor laser device by a diffusion process, there is a problem that if the diffusion front gets too close to the active J# (3) VC, the crystallinity deteriorates and the characteristics and lifespan are impaired. Therefore, in this embodiment shown in FIG. 2, in order to avoid this effect, the diffusion front is extended from the active layer (3) to the n-type Ga1-
The VCC is designed to remain at a distance equal to or more than the thickness of the yAtyAS cladding layer (4). Furthermore, in the case where there is no n-type aAs layer (9) in FIG. 2, the diffusion front is controlled to reach the n-type Ga 1-yAtyAS layer (4) during diffusion, and to bring it as close as possible. makes it steeper. tj ze nara n type Ga l-2A7ZA
The diffusion rate of Zn at 8Jd +10 is faster than that of the n-type GaAs contact layer (5), so it passes through the n-type GaAs contact layer (5) and becomes the n-type Ga, -2AtzAB.
) gi (It will be difficult to expand sales to stay within lfJ, and reproducibility will be poor. Therefore, in this example, Ga
1-2AtzA6 note tu), zn than this
A GaAe layer +9) with a diffusion rate of n-type Gal-y
gyA 1117271m [41 and GallAAzAs
By arranging V between the layer ut), the diffusion front becomes n-type Ga1-yAtyA8 cladding Jf414] 1
NoqK people 9 I tried not to get in 7 Hi.

Therefore, the diffusion method V is therefore the p-type diffusion daughter area (lla), (
When forming nb), the diffusion front is reproducibly converted into n-type G.
a1-yA ZyA e It can be stopped just before the cladding layer (4), and characteristic deterioration due to a decrease in crystallinity can also be prevented. By keeping the thickness of the rough VCn-type GaAs layer (91) to the necessary minimum, the effective stripe width can also be controlled with good reproducibility.

In addition, in the above description, the GaAs contact layer 15J
and Ga 1-yAl-yA B Clad M (VcL between pieces) az g3A7zA B square (Z) 0)
and the GaAs layer (9), but the contact) d
(If 5J is ()al-JAt4A8 layerg VCIi
, Ga1-m"m"5)d(1(J (where m > t) and GallAtnA day layer (9) (where n < m) are arranged, the contact layer (5) is similarly directed toward the inside. Of course, a semiconductor laser device having a structure in which the width of the current path is narrow can be obtained with good reproducibility.Also, a structure in which the conduction type of each part of the above embodiment is reversed and sulfur (S) is used as the diffusion impurity can be obtained. It is clear that the object of the present invention can also be achieved in this case.

As detailed above, in this invention, two wavenumber control semiconductor layers with different impurity diffusion rates are provided between the contact layer and the upper cladding layer to control the formation of striped regions due to impurity diffusion. The effective width of this striped region, which serves as a current path, can be narrowed with good reproducibility, and the width of the striped region, which serves as a current path, can be narrowed with good reproducibility. A semiconductor laser device with a long lifetime can be realized with good reproducibility.

[Brief explanation of drawings]

Does Figure 1 show an example of the structure of a conventional semiconductor laser device? Sectional drawing: FIG. 2 is a sectional drawing showing a four-piece construction according to an embodiment of the present invention. In the figure, January is the semiconductor substrate, (February; lt 1st glue 2rad half-coated body no, (3) fat active active body 4j is 42 clad half-metal 4 bodies) ar, L5J is the contact half. The normal body layer, (9) is the first wave number control half body layer, 0 is the wave number control half body layer of the conduit 2, (dana), (
ub) is an impurity 1 diffusion robust region. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent: S Field 1 (1 other person) Figure 1 Figure 2-4, 18-

Claims (1)

[Scope of Claims] (11) A first cladding semiconductor layer of a first conductivity type on a semiconductor substrate of a first conductivity type; A gruple heterojunction structure is formed in which an active semiconductor layer having a narrower bandgap and a second cladding semiconductor layer having a second conductivity type and a bandgap wider than the active semiconductor layer are sequentially in contact with each other. , a first diffusion anti-saliva semi-quadruple layer of a second conductivity type, which is formed sequentially in contact with the second cladding semiconductor layer and has a relatively slow diffusion rate of impurities in the W crystal; a second diffusion semiconductor layer of a relatively fast second conductivity type and a contact semiconductor layer of a second conductivity type, the contact semiconductor layer and the first and second diffusion If11 semiconductor layers; An impurity diffusion region is provided in which a first conductivity type impurity is diffused from the surface of the contact semiconductor layer except for a striped hard region extending over the area so that the C diffusion front is within the first diffusion control semiconductor layer. (2) The semiconductor substrate is made of GaAs, and the first cladding semiconductor layer and the second cladding semiconductor layer are made of Ga1-yAZyA.
θ, the active semiconductor layer is Ga, -xA7xAs, the first diffusion control semiconductor layer is Ga1-nAtnAs,
2 (D diffusion side - semiconductor layer is Gal-mA 4nA s
2. The semiconductor laser device according to claim 1, wherein: (y)x, n, >m.