JPS6066890A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To contrive to reduce the bad influences of return noises, without losing the characteristic of small astigmatism, by a method wherein the thickness of a clad layer is varied along the direction of a groove stripe. CONSTITUTION:A clad layer 12 of n-conductivity type and, an active layer 13 and a clad layer 14 of p-conductivity type are successively grown on a semiconductor substrate 11 of n-conductivity type, resulting in the formation of a double hetero junction. Besides, a current block layer 15 of n-conductivity type grown and formed on the clad layer 14 provided with a stripe groove 16 reaching the layer 14, and a coat layer 17 of p-conductivity type grown and formed on the layer 15 by including the groove 16 are furnished. The layer 14 is formed so as to have at least two kinds of thicknesses to the direction of the stripe.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor laser device having the features of both a gain waveguide structure and a refractive index waveguide structure.

[Technical background of the invention and its problems]

In recent years, semiconductor lasers using III-V group compound central body materials such as a AtAl) have been developed.
Applications to information processing equipment such as optical disk files and digital audio disks are being advanced. In semiconductor lasers for optical disks, it is necessary to narrow down the laser beam to a great extent, and in order to simplify the optical system, fundamental transverse mode oscillation and small astigmatism are required. The IJJ has clarified that there are the following problems when applied to optical discs. That is, in an optical disk file, etc., a mechanism called u;l: protrusion 1 detects the intensity of the reflected light of the light that hits the dicta V and outputs information, and a part of the reflected light is converted into a 1" body laser. It is unavoidable that the semiconductor laser will return at both ends 1.
In addition to the resonator in which iIi is 1', there is also a resonator in which the laser end face and the disk face are separated by the shape of by, resulting in a laser having a 2-ri resonator. And -y=□f
When the mount 1 vibrates during rotation, the latter's resonator length becomes liquefied, which affects the suspension torque and light output (1).
1 is generated, 7 is returned to the original) and 1 is returned.

From the viewpoint of suppressing the 1° (1°) angle, the 4I surface of the semiconductor laser (1° 4j blue, , M
, i try whitening.

'11''') rt, II, to Lere q..., Cao and Lu (1°4 construction generally goes to gain)! Wave) Wi +i'+
structure and refractive index>, 17. Wave paths are roughly divided into two types: 41-I structures and 4) o These 41-J structures include: 1.・Astigmatism 7J
: to reduce the return yl-no1z2)
The thing is 1.1 node ono 1 mo 1 廿. That is, the force J (refractive index 77'I wave b'6 + 4 V←, the astigmatism rJ: 5 [ttm] is small as II-) is determined by L. Therefore, the longitudinal mode also oscillates in a single mode of 1"/), but because the line width of the sheath line is narrow, the amount of output fluctuation due to the return light nozzle is as large as 1") [63 or more. In the 111 harmonic V11 structure, the longitudinal mode becomes multi-mode and the linewidth is wide, so the output fluctuation due to return noise is less than J [%], but the astigmatism Q is less than 20 [μm1 6 Therefore, the astigmatism and the return light noise are 71h poor: times + 1j
In order to satisfy r, it must have the properties of both the refractive index waveguide structure and the force waveguide structure.

By the way, the city', which is related to the gain distribution! jii', the Rayleigh design of a structure in which the constriction structure and the refractive index waveguide structure are automatically formed;
Although it is called l・-za, especially 'current confinement 4'f#;'+'
Those in which L does not appear on the surface of the 11゛1 crystal are called internal stroke type 1/-za. This type of laser is manufactured by
The process is easy, and high yield and productivity are expected. At the same time, since the active layer can be formed inside the crystal, it is less susceptible to defects from the FFV surface, and is less susceptible to deterioration caused by mounting. If we can reduce the shadow W of
1% ill as all ii'i7 electric cedar; By reducing Jnot', it is possible to eliminate the need for zinc diffusion, etc., and the surface can be made flat, which is advantageous for mounting. It has certain advantages.

Conventional internal stringer If self-aligned [/- the u2 as
, V r:rt is applied to the +4°C flow prevention layer fc VS]
, S (V −L″b++ Kano clcd 5ubqLrn
A Le Inner Strip laser is known, and it is known that the laser is mode controlled and has good return light characteristics. (- However, the VSIS laser has crystal growth with good uniformity over a large area compared to the LPE method; Yes. During this time '+1'+x
It's big for optical disk led and L ~; +4. raw st
n, “Half-heart body-de-made pickled IC that has reached its first generation!:,-
This is a fatal flaw.

The most J there! The first example of a similar internal stripe self-aligned laser that can be manufactured using the 'v10-CVI) method is shown above.
As shown in the figure, an internal stripe structure is formed on the upper part of the Sei 1 biolayer.
A semiconductor laser was proposed. In addition, 1 in the figure is N −
GaAs, '7t-plate, 2 is N-GaAtAs cladding layer, 3 is GaAtAs active layer, 4, F; l J
)-GaAlAs Kura.

layer, 514 N-GaAs electricity! 5ii: Closure i'j; l, t; 1. J, striped groove, 7
is l' -GaAtAs #substituteAe, 81j(P -G
aAs ry tough layer, 9.10 indicates metal shell, stem. ? In the structure of C, the current blocking layer 5 in which the strip-shaped sea part 6 is formed limits the injection of kI and current into the active layer 3 to a stone-shaped shape, and the waveguide in the active layer 3 is 1 seeps into the layer 4 and the chemical current blocking layer 5, and as a result, a guided mode is formed directly below the stripe. The wavepath structure is realized simultaneously.

However, the glaze's lack of laser abrasion caused the following problems. 1′, lb: bee, 1
511 Striped r of stop layer 5: "I Bl ~ Width of 6 -
(The widths of the 711111 distribution and refractive index distribution are temporarily determined;
1, and the width of each distribution is equal. This l
On the order of b, the refractive index difference is sufficiently large, and the 11゛4 characteristic of the 11'' special wave path does not appear. It was not possible to obtain a satisfactory result with respect to the return light characteristics (-).

[Purpose of the invention]

The object of the present invention is to: (11) be able to sufficiently reduce the adverse effects of return light noise without losing the feature of small astigmatism in transverse mode oscillation;
Semiconductor laser device b extremely useful as a C source: 1. 'Y
f 13.1.

[Summary of the invention]

The gist of the present invention is to realize a structure that combines the features of both a refractive index waveguide structure and a gain waveguide structure.

(See Figure 1 above) In the laser of J.
When the electromagnetic wave IL blocking layer 5 absorbs light and sound, an effect of a refractive index power wave path occurs, which increases the power factor difference in the layer direction. -Force, above 1/-The smell-C, If the thickness Jf of the cladding layer 4 is made thicker, the light emitted from the active knob 13 will be 11teυ1, and the difference in the refractive index of the double JFil due to the blocking layer 5 will not be felt. You can do it like this. In this case, the effect of the laser waveguide takes priority in the laser. In other words, the astigmatism is small, but the output fluctuation due to noise is
becomes larger.

Therefore, if the above 2 f'lli laser can be realized in one resonator, the t1 refractive index will be 2. The features of both the gain waveguide structure and the gain waveguide structure are expressed as ,Iljne(j!f
This means that a laser beam with high brightness can be obtained. Focusing on this point, the inventors of the present invention conducted extensive research, and found that the cladding layer 4
It has been found that the thickness of the groove can be varied along the groove stripe direction.

That is, the present invention includes a semiconductor substrate of a first conductivity type, and at least a first cladding layer of a first conductivity type 1E, an active layer, and a second cladding layer of a second conductivity type, which are grown on this substrate in a JtEi step. A striped groove 451 (17.1'?) is grown on the formed Twisted heterojunction and the second cladding layer 1, and is formed entirely on the second cladding layer 1.
- an electric current of the electric type (including the four blocking layers and the groove part)
In the semiconductor device including a covering layer of a second conductivity type grown on the stopping layer and f: the second conductive layer '<i; It was formed to have the thickness of God.

(Effects of the Invention) According to the present invention, an advantageous 4+ waveguide structure can be formed in the part where the second cladding layer is thick (generally at the center fXB), and the second cladding layer is thin. A refraction Tomape waveguide structure can be formed at the refraction section (generally near the resonance 2 and the ψl'h-th 5B). Gain distribution ζ in wave path structure
! It is possible to select all the parameters independently.Furthermore, the Ja
The ratio between the il j Jr index waveguide i'lt and the equal gain waveguide part can be changed arbitrarily by 1'+-. From the above, we were able to see the dependence of the two waveguide structures on the optical noise characteristics. Therefore, two ;';'
7 + The proportion of the wave path portion and the structure and V meter of each
Commercially set - Nono, possibly 1/- for optical discs
The fljr (4g, that is, the fundamental transverse mode oscillation, the astigmatism is sufficiently small, and the output fluctuation due to optical noise is also sufficiently small) can be achieved by the present inventors. According to the experiment, GaAtAs 'fr: Proportion of At in active layer as material
%1 f GaAs, the second cladding layer of the refractive index guide part) + 7 (a): 15 [μm], εf52 of the gain guide part, 0.5 [μm],
rj'j, ll'bX of the current stripe]2 μm
], and the refractive index of the end face τ111 in the cavity length is
The ratio of the A1 part is 5 to 45 [as an illusion, astigmatism is 5 to 10 [μm], longitudinal mode is 51: rnW]
The amount of output fluctuation due to multi-mode and return light noise is J [
1) This '141'l body is extremely suitable as a laser for optical disks 6. [Embodiments of the invention] Figures 2 (a) to (C) iqJ , respectively of the present invention -
General measures of semiconductor lasers related to '-13(li)fl 't:', ? (In Fig. 2 (a) kj in the direction of the resonator, W
! -1 (I+) is a sectional view taken along arrow A-A in the same figure (,).
2 (C) η'', 71 &y[N-GaAs substrate,
On this substrate JJ are an H,N-GaAtAs cladding layer (first cladding layer) 12, a Ga AAA 8 active layer 13, and a P-GnAtAs cladding layer (2iT 2 cladding layer) 14, all 11! A double heterojunction formed by +'1 and 3 is formed. Here, the second cladding layer 14 is thick at the center with respect to the striping direction of arbitrary 1Σ, and is thicker near the i2!2 portion.

In the second cladding layer 14, a striped groove fi 1516 is formed with a flow prevention layer 15 (tC is the depth reaching the second cladding layer 14). p-GaA/-As Km fit layer 1
7 and P-GaAs contacts! - Layer 18 is formed. The numbers 19 and 20 in the figure indicate four criminals, respectively.

Next, the manufacturing process of ``Niki-Naraba+'l/--Li'' will be explained with reference to FIGS. 3(a) to 3(f).

First, in Fig. 3(a), 73<sη11<N−, u
As 茫枳 (S+ dope.

n2J~2XlOcm) IIJ2 first cladding layer 1
2 as N'-Ga g, 55A16.45A 11
Layer (n-1, XI O'%-3 + thickness 1., 5 z7m
), undoped GaO as i-occupancy no so 13, 85
AtO, 1sAs layer (j corner (1,08μ+nLffi
P-Ga o, 5sA as zclad jp'H14
to, <5A81(i (n-1(118~1.019
0η-3, thickness 1.5 μm) was sequentially grown and formed [-/ko.

This f'PjJ-th crystal growth K ('J, MO-C
Using the VD method, 4* conditions &': J: lagoon, p'5
1750 [°C], V/III = 2 o, flow rate of Koyaria Sosu (H2) ~] OLl/1ninl, J
J31.1:1 is trimethyl gallium ('l''MG:
(CI)3Ga), I-remethylaluminum (T
MA: (CH3)! , AL), arunone (AsI1
3), pl' ”n): ” 工”J-ru!llj
Lead (DEZ: (C2)]-5)2Zn), ndoz
e71-: Hydrogen selenide (H2Se), the growth rate is (1,25Lμm7'rn I11) and 6-Z
is. Note that the first crystal growth 'Ct is not necessarily Δ40.
- No need to use CVD method trJ: No, large surface Uf
hhJ-CVT capable of uniform crystal growth of 1"
) method is more advantageous than the 1st and circle C method, which takes into account emotionalization.

Then, (U]],'
) direction with a width of 200 [μIrl] 4 (10j/n+
Form a first Renost mask (shown in Figure 1) using a phosphoric acid etchant, and apply a 31st Lennost mask (shown in Figure 1) using a phosphoric acid etchant. 2nd Kun
・ Tono fj 1 4 y): B,! Saku J, '5
tf μ+n] (・I erased it until it turned out. After removing the earth pressure resist mask iLl':i?, the second time) I did the crystal IJ and length", l? NO-CVI
There are 11 in the J method. That is, as shown in FIG. 3(c), a current blocking layer 15 is formed on the second cladding layer I4, and N-Ga is formed on the second cladding layer I4.
As layer (n == 1018~1019cm-3゜J/
, 0.51 part m ) was formed. After that, to block the current, apply a Jl-resist mask (1 shown in the figure) to the XQ 15 soil.
A trench of [μm], V, 30 (l [1uII]) was formed, and using this as a mask, a phosphorus Aj7-based etchant was used. The current blocking layer I5 was etched by this iL.
A striped groove portion 16 having a groove width of 3 [ttI]1 is formed at the bottom.

Next, the upper resist mask was removed, and the second crystal growth was performed using the MO-CVD method, as shown in Fig. 3(e).
, 55"0.45As) a (p = I 018cr
n-', thickness 1.1lrn), and the contact layer 18 is P-GaAo (p = 1019on-' +
2 μm thick) were sequentially grown. Here, for the second and subsequent crystal growth, 1. Because the crystal growth is on a layer with a sieve ALa exposed to the atmosphere, it cannot be grown using the conventional LPE method, and the MO-CVD method is required. Ru.

Next, as shown in FIG. 3(f),
9 is Cr/A u, lower electrode 20 is A, 13G
+! /AIJ was deposited and ohmic contact was made. Thereafter, by dividing this sample by cleavage, a laser as shown in FIG. 2 is completed.

In the thus created laser, when we tried to vary the ratio of the refractive index guide part to the cavity length, we found that the refractive index guide part (the thinner part of the second cladding layer 14)
When is 45 C13 or higher, astigmatism is 3 [μrr+),
Below, the characteristics of a power II/1 ratio guided laser are shown in a longitudinal single mode with output fluctuation due to return light of more than 10 [cycles]. M
! , Jar"$ force id tour de force 41 part 45 [%], astigmatism 5 ~] 0 [/1 m], vertical multi-mode, output fluctuation due to return light, H ↑ J [%] or less and refractive index・1゛t′f is shown for 1 of the gain type ・f1゛.

In addition, when the refractive index (G) is less than 5 [mirror], astigmatism is more than 20 [μm3, longitudinal multimode, and output fluctuation due to returned light h', J [correspondence] or less, showing the property of gain guide type. . Therefore, for example, the cavity length is 260[7ZITl:
] If the refractive index guide portions at both ends are each 30 [μm], then the refractive index guide? ~The proportion of IS is 23 [persons]
Therefore, it is suitable as a semiconductor laser for a C7'' disk in terms of astigmatism and output fluctuation due to returned light (1:
,) Sexuality will be violated.

It is said that astigmatism is small if the ItC is actually implemented like this! 1j1 Without losing the length, the adverse effect due to the return light noise'f3. '-1 minute smaller, the light beam'
It is for zusufu use, 0 yen, and 0°C, and 1 for 1. It is sweet, because the MO-CVD method can produce IJk, and it is also extremely effective for producing TA+(j).

It should be noted that the present invention is not limited to the specific embodiments. For example, t:J:, the growth method of each layer is MO-C
The method is not limited to the VD method, but may be the MBE method. Moreover, the composition ratio QJ of each layer is not limited to the example, and can be changed as appropriate according to the specifications.

For example, if the At composition of the second cladding layer is "hl=O-
35, and can function as a light guide layer.

In this case, the leakage of light increases, so that it is necessary to thicken the second cladding layer in the gain guide part to 2 [μm] or more so that the light does not feel the difference in refractive index in the gain guide part. In this way, it is possible to improve the beam spread angle and aspect ratio, and to increase the output power.

As the semiconductor material t1, in addition to GaAtAs, a compound semiconductor rod 1 such as aInAsP or GaAtAsSb can be used. Furthermore, it is also possible to use a P-type substrate instead of an N-type substrate and reverse the conductivity type of each layer. Further, the tanohedero junction structure of the active layers f, -/h is not limited to a symmetrical three-layer structure, but may be asymmetrical or multilayered with three or more layers. In addition, it is possible to make various modifications and implement ten without departing from the gist of the minor invention.

[Brief explanation of drawings]

Figure 1 shows a schematic diagram t'I of an internal stripe self-aligned laser.
Figures 1 and 2 (aJ-(c) are cross-sectional views showing the schematic structure of a 1-piece laser according to an embodiment of the present invention, respectively. Figure 31:'4+ (aJ-( f) is a cross-sectional view and a plan view showing the manufacturing process of the above example laser. J l =-N-GaAs substrate, “ ”・N-GaO
,5! l”[1,45A8 first cladding layer, 13...
And-fGao, 8μ. , 1≠8 active layers, 14·=
P-Gatl, 55"4], 45A' m2 crasito layer, 1.5-N-GaAs'iJi: flow blocking layer, I6-stripe groove, 17"-P-Gao,
55Aja0.45AR ω layer, 18...P-GaAa
Contact layer, 19.20... electrode. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 11-31-1

Claims (2)

[Claims] (1) In a conductor laser device, the first conductor f is made of a compound conductor material and has a double heterojunction structure.
n-type 21 (conductor substrate, and at least a first
a double heterojunction formed by sequentially growing a 7-layer J cladding layer, an active layer, and a second conductivity type second cladding layer; and a double heterojunction formed on the second cladding H; And the 4′i electrotype 奄υir, i!, in which a strife 0-shaped groove extending to the second cladding layer is formed. Ill stop layer;
The above box includes the groove>SB and the metal fitting (+
iii I,,i'+iJ second cladding layer is 1)11
It has at least two types of thickness in the direction of
Formed like this 1 f: Characteristic semiconductor 1/
-de equipment. (2) A patent characterized in that the i4IJ IJt second and seventh layers are formed thickly at the center with respect to the stripe direction, and thinly formed at least on one end side of the resonator. A semiconductor laser device according to claim 1.