JPS58131788A - Buried structure semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain the buried structure semiconductor laser having high reliability through crystal growth at a time by forming an active layer blanked on two parallel striped projections onto a semiconductor substrate with the projections and using the active layer of the upper section of a groove between the projections as a main light-emitting region. CONSTITUTION:The two parallel mesa stripes 2 are formed onto the n-InP substrate 1 through photoetching. It is adequate that height is 2-4mum and the width of upper sections is approximately 2mum or less. Buffer layers 4a, 4b made of n- Inp are grown onto the substrate 1. The active layers 5a, 5b are crystal-grown blanked in the upper sections of the stripes 2. A p type clad layer 6 made of p-InP is grown. It is adequate that thickness is 1-5mum. A cap layer 7 consisting of n-In1-x'.Gax'Asy'P1-y' is grown. A Zn diffusion layer 8 is formed. A p type electrode 9 and an n type electrode 10 are formed through a vacuum deposition method, and the manufacturing process of a wafer is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor lasers, particularly buried structure semiconductor lasers.

Buried structure semiconductor lasers are superior to conventional gray nurse drive semiconductor lasers in terms of low current oscillation performance and transverse mode stability, and are considered to be promising for use in original fiber communications.

However, although it has high performance, the manufacturing process is long and usually requires two crystal growth steps. As a result, the time required to keep the mother crystal of a semi-integrated laser at a high temperature doubles, which increases the probability of introducing defects, increases costs due to the long manufacturing process, and reduces productivity. there were.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser with an expanded structure that can be easily produced by one-time crystal growth, has high reliability, high productivity, and is low in cost.

According to the present invention, the active layer is formed on a semiconductor substrate having two stripe-like protrusions substantially parallel to each other and is missing on the two stripe-like protrusions; A buried semi-integrated laser is obtained, characterized in that the active layer formed above the groove serves as a growing region.

The present invention will be described in detail below with reference to the drawings.

Figure 1 shows the wavelength of 1.3 μm 1 nG in the first embodiment of the present invention.
aAaP/In)' is a cross-sectional view of a buried structure semiconductor laser. In the figure, 1 is an n-1n)' substrate, 2 is an n-1nP
The two mesa stripes 3 formed on the substrate 1 are the curved grooves S 4m and 4b of the two mesa stripes 2.
One layer of buffer consisting of P, 5 m and 5 b ij In
5-xGaxAsy)'t-y (X~0.24 Y
-0,6), 6 is p-1nP
type cladding layer, 7 is n fJj, 1al-x'Ga1
A cap layer consisting of AaIPI-)/(X, Y≠0), 8 is a Zn diffusion layer, 9.10 is a p sub-electrode,
It is an n-type electrode.

The main light emitting region of the augmented structure semiconductor laser of this example is the active jm5m. In order to improve the stability of the rage mode, the width of the active layer 5m is 5 μm or less, preferably 2 to 3 μm.
The thickness is preferably 0.5 μm or less, preferably 0.1 μm. The two mesa stripes 2 are for cutting off the active J@58 and 5b in the crystal hx, long time. As a result, the active layer 5a is sandwiched between two mesa stripes 2 in the horizontal direction, and in the vertical direction, the active layer 5a is sandwiched between two mesa stripes 2, and in the vertical direction, an n-shaped multi-layer 1° 1fit 4t.
* Since it is sandwiched between the p-type cladding layer 6 and the p-type cladding layer 6, the buried structure is actually damaged.

The manufacturing process and structure of the buried structure semiconductor laser of this example will be explained below. First, two mesa stripes 2 are formed on an n-1nP substrate 1 using a normal photoetching technique. The two mesa stripes are formed almost parallel to each other and have a height of 1 to 10 μm, preferably 2 to 4 μm.
m is appropriate. To avoid forming an active layer on the top of mesa stripe 2, the width of the top of mesa stripe is 5μ.
The appropriate thickness is about 2 μm or less, preferably about 2 μm or less. The cross-sectional shape of the mesa stripe does not necessarily have to be a complete mesa shape, but may have other shapes (for example, a section shape or an inverted mesa shape, or any striped protrusion that protrudes from a flat part). In this way, two mesa stripes 2t-shouldered n-1n)' substrate 1 are prepared, and crystal growth is performed to a large diameter using a liquid phase growth method.

First, a buffer layer 41 and 4bt consisting of n-1n)' is grown on the n-1n)' substrate l. Since this material (sofa-1 is n-In)' has a four-composition with substrate 1, it is not necessary, but the n-In
This is to avoid forming an active layer on the damaged layer formed on the surface of the 1nP substrate l. It also has a machine hL for flattening the bottom of the buffer layer 4a/d tiles 3. w, In Figure 1, the buffer layer grows with defects on the top of mesa stripe 2, but it is not necessarily necessary for the crystals to grow with defects, and the buffer layer grows on the top and sides of mesa stripe 2. Crystal growth may be continued. In mesa stripe 2, whether or not to grow a single buffer layer is a matter of decision! It can be controlled using tc conditions. Also, in this embodiment, one buffer layer is made of n-1nP, but it does not necessarily have to be made of n-1nP, and l! has a forbidden band width wider than that of the active layer. 11-X"GaxNAsy"l'l-y"<
X//Y//+o>. In this case, it is necessary to cut out the mesa stripe 2 and form a single buffer layer. This is because when one buffer layer is formed on mesa stripe 2, 1m1-x of one buffer layer
#(jm/~, //P, -, " is sandwiched between lnP) Since the H structure is formed on the mesa stripe 2, light emission and laser oscillation occur in the buffer layer, and light is transmitted to the active layer 5m. Therefore, when forming a single buffer layer of 1nl-x (as shown in the figure). or,
In this case, since the buffer layer also functions as a guide layer, there is an advantage that the degree of freedom in designing the active layer 4m and its thickness increases.

In this case, the active layers 5a and 5b are grown next to the buffer layer. In this case, crystal growth must occur with defects in the upper part of the mesa stripe 2. Rihaku is 1IIt-x “Gas” Aa
As in the case of a single buffer layer consisting of y "Pl-1", when an active layer is formed on the upper part of the mesa stripe 2, light emission and laser imaging there are reduced, and the current injected into the main active layer 5a is reduced. This is because efficiency deteriorates. Therefore, it is necessary to select growth conditions so that the active layer does not grow into Mesa Stripe 2 soil. Therefore, the active layer is grown separately into the active layer 5a formed on the upper buffer layer 4a of #I3 and the active layer 5b formed on the flat part.

The thickness of the active layer 5a is 0.5 μm or less, typically 0.1 to
The p-type cladding layer 6 consisting of 0.2 μm 8tL is grown. Next, the p-type cladding layer 6 consisting of p-1n)' is grown. If the op-type cladding layer 6 is thin, the leakage current flowing to the active layers 5b on both sides can be reduced, so it has a low threshold value. Current is realized. Also, the thicker the surface, the more flat the surface, which has the advantage of reducing problems when fixing the pellet to the stem. The appropriate dryness is 0.5 to 10 μm, typically 1 to 5 μm.

Next, a cap layer 7 consisting of n-1ax-x'Ga1Any'Pi-7' is grown. This layered layer is intended to improve the ohmic contact between the electrodes, but is not absolutely necessary. The crystal growth process is completed when the thickness is 0.5 to 3 μm, typically about 1 μm.

Next, in order to form a w flow path to active) fli5m, Z
An n-diffusion layer 8 is formed. In this formation method, the impurity used for diffusion by the selective diffusion method using a 5iO1 film or the like as a selective mask is limited to Zn; other impurities (for example, dCd0M9) may also be used. The Zn diffusion layer 8 formed in this manner does not serve as a current path for the active layer 5m, and no rounding current flows in other regions where Pnl&combination is reverse biased. In this way the current can be limited to only the upper part of the active@5a. The current limiting structure is not limited to the one using the Pn junction of this embodiment, and other current limiting structures may be used. For example, the active layer 51
It is possible to use a method in which an insulating film such as 81 (J), in which only the upper part of the cap layer is missing, is interposed between the cap layer and the cap layer.
The fourth type of the cap layer can be made p-type without Zn diffusion.

Next, a sill-type electrode 9 and an n-type 1[&10] are formed by vacuum evaporation to complete the wafer fabrication process.

After ilk, laser pellets are extracted from the wafers made as described above using J! Cut out using #- etc. After that, a semiconductor laser is mounted on the stem, and the entire manufacturing process is completed.

As is clear from the above-mentioned manufacturing process, the embedded floating half-body laser of the present invention can be manufactured in a single crystal growth process, and there are no troublesome parts in the crystal growth and manufacturing process, resulting in high productivity. Has a high % length. Therefore, the yield is high and production is possible at low cost. Moreover, the characteristics were at least as good as those of a buried structure semiconductor laser grown twice.

Figure 2 shows the wavelength of 1.3 μm 1 nG in the second embodiment of the present invention.
aAs)', /In)' is a cross-sectional view of a buried structure semiconductor laser. In the figure, n-1n)' substrate 1, two mesa stripes 2, 1113 between the mesa stripes. n-1n
The buffer layer 48 and the 4b% active layers 5a and 5b made of P are exactly the same as in the first embodiment.
6 is the first Opm consisting of p-1nP2/iI#1
7 is a 11R blocking layer consisting of n-1n)', 18 is p-1
Second p-type cladding layer made of nP, 19 is 1e1-x
In this example, Unlike the first embodiment, the leakage '#LtIrt flowing to the active layers 5b on both sides is blocked because the Pn junction between the current blocking layer 17 and the first p-type cladding layer 160 is in a reverse bias state. A current path to the active layer 5m is formed by Zn diffusion 1-20.

Therefore, Zn is diffused so that the diffusion front of Zn diffusion 1-20 is located in the middle of the first p-type cladding layer 16. Leakage current flowing laterally through the first p-type cladding layer 16 and injected into the active layer 5b can be reduced by making the first p-type cladding layer thin.

In the case of this embodiment, since the second p-type cladding layer 18 is provided, the surface can be made flat even if the first p-type cladding layer 16 is made very thin. Therefore, in this example h,
*The p-type rad layer 16 of x can be thinned, so the threshold value is low! The flow is good. First p-type cladding layer 1
Thickness of 6 J/'i 0.3-3μm typically 1-2μm
is unreasonable.

The current blocking layer 17 does not necessarily have to be made of n-1n)' (n-1nGaA@P, which has a very good thickness, may be relatively thin, with a thickness of 0.3 to 5 μm A type). Target is 0.5
~l11m. If the current blocking layer 17 is made thicker, the surface becomes flat, so the second p-type cladding layer 18 can be omitted. Furthermore, by making the - of the mesa stripe 2 relatively narrow and controlling the liquid phase growth conditions, the current blocking layer can be grown as a crystal with defects in the upper part of the mesa stripe 2. This takes advantage of the fact that the growth rate decreases on narrow protrusions in liquid phase growth. This case is considered as a third embodiment, and a sectional view thereof is shown in FIG.

In the third embodiment, since the current blocking layer 21 grows with defects on the mesa stripe 2 during crystal growth, the active layer 5a
A current path is automatically created.

Therefore, there is no need to diffuse Zn and form a current path as in the case of the second embodiment, which reduces the number of steps by 8u and steps*1.
The second p-shaped rad wall 18 is very effective in making the surface flat and has a thickness of 1 to 5 μm.
m form. Further, the cap layer 19 is provided to improve ohmic contact and is not necessarily required.

In the above Th4 example, the material is 1nGaAsP/
in)', but other materials such as Ga
AA! As/GaAs, GaAlSb/(iasb, etc.) may be used as a gold phase.Also, although an n-type group & was used as the substrate, p
It is also possible to use a pattern board in which all the pigeons' Toden types are reversed.

In addition, although the resonator surface was formed using @open, it is also possible to form the resonator surface by etching.Although the active layer is a single layer, it is not limited to this, and may include a light guide layer, etc. It may have a multilayer structure.

Finally, to summarize the features of the present invention, it is possible to manufacture a buried porridge-forming semiconductor laser by one-time crystal growth, resulting in high productivity and low cost. It lies in being served.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the buried structure semiconductor laser of the embodiment of Series 1, Fig. 2 is a cross-sectional view of the embedded structure semiconductor laser of the FiM2 embodiment, and Fig. 3 is a cross-sectional view of the embedded structure semiconductor laser of the embodiment of FiM2. In Figure 0, which is a cross-sectional view of the structural half-body laser, l...n-
1n)' Substrate, 2...Two mesa stripes,
3...Habit, 4th and 4b...Buffer layer, 5m and 5b...Active layer, 6...
・P-type cladding layer, 7... Cap layer, 8...
...Zn diffusion layer, 9 ... ... p tl 1-1 pole, 1 0 ...----n W'1
1. (4 taku, 1 1...Zn diffusion layer, 1
6...First p-shaped rad pigeon, 17...
- Load blocking layer, 18... Second p-type cladding layer, 19... Cap layer, 20... Zn
Diffusion layer, 21... is a current blocking layer. #1 Diagram ρ Sheep 2 diagram π

Claims (1)

[Scope of Claims] A buried structure semiconductor laser in which the active layer formed on the upper part of the groove between the two stripe-like protrusions is used as the emission habitus region. (2) A cladding layer of 5141 on the shaved active layer, 1. A buried phosphor half laser according to claim 1 of the Patent Application Claim, characterized in that a current blocking layer and a second cladding layer are provided.