JPS63198388A - Semiconductor laser and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a stable oscillation in the transverse mode by a method wherein a ridge structure or a V-groove structure is formed and a p-n junction part is incorporated in the ridge structure or the V-groove structure. CONSTITUTION:The following two are provided on a semiinsulating GaAs substrate 1: a laminate composed of an n<->.AlxGa1-xAs clad layer 2, an n<+>.AlyGa1-yAs active layer 3 (where x>y), an n.AlxGa1-xAs clad layer 4 and an n<+>.GaAs cap layer 5; a p<+> region 6 formed in the laminate. A p-n junction which has been formed in the n<+>.GaAs cap layer 5 is separated; a ridge structure or a V-groove structure which has been formed along the p-n junction is formed. That is to say, the p<+> region 6 is formed in the laminated film; on the other hand, the ridge structure or the V-groove structure is formed; the p-n junction part is incorporated into the ridge structure or the V-groove structure; the difference in a refractive index in the transverse direction is caused by a contact part of the p<+> region 6 with an air part or a GaAs layer where the ridge structure or the V-groove structure is formed on one side of the clad part. By this setup, a stable transverse mode is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a lateral junction semiconductor laser that has a brainer electrode that can be applied to optoelectronic integrated circuits and that can be formed without using a high-temperature process, and a method for manufacturing the same. .

[Conventional technology]

A lateral junction semiconductor laser conventionally has a structure as shown in Figure 4 (H. Kumabe et al., Journal of Japan Applied Physics (J, J.
, A, P, ) Ai (1979) Subliment 18-
1, pp 371-375), i.e., an n-AuGaAs cladding layer 2 on a semi-insulating (SI) substrate 1.
, an n-4p-GaAs active layer 3, an n-AuGaAs cladding layer 4, and an n''-GaAs cap layer 5 are sequentially epitaxially grown, and the SI substrate 1 is grown from above the cap layer 5.
After vapor phase diffusion of Zn to form p+++++6 until reaching , high temperature annealing at 900 to 950°C is performed to drive a diffusion front of about 2- to form a Zn high concentration P+ diffusion layer 9, and then form a GaAs It has a structure in which a p ++ p + n+ region is formed in the lateral direction of the active layer 3, and 7 and 8 in FIG. 1 indicate a p electrode and an n electrode, respectively, and is called a TJS laser.

[Problem to be solved by the invention l The lateral junction laser according to the above-mentioned prior art has p++
A high-temperature process is performed to thermally diffuse the ends of ++6 to form a p+ diffusion layer 9 and form a p light emitting region.

There are problems such as lowering the yield of elements and damaging the SI substrate 1 when integrating with FETs and the like.

An object of the present invention is to provide a new lateral junction semiconductor laser in which a lateral refractive difference is formed without using a high-temperature process that causes the above-mentioned problems, and a method for manufacturing the same.

[Means for solving problems]

The above object is achieved by forming a ridge structure or a V-groove structure and incorporating a pn junction into the ridge structure or V-groove structure.

[For production]

The present invention does not use indentation diffusion using a high-temperature process that has been conventionally used in the fabrication of lateral bonding lasers.
A p-region is formed in the laminated film, and a ridge structure or a V-groove structure is formed, and a pn junction is incorporated into the ridge structure or the groove structure, and the ridge structure or V-groove structure is provided on one side of the cladding part. Air part or GaAs layer and the above p
A transverse refractive index difference is caused by the contact portion with the region, and a stable transverse mode can be obtained.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a structural sectional view showing a first embodiment of a semiconductor laser according to the invention, FIG. 2 is a structural sectional view showing a second embodiment of the invention, and FIG. 3 is a structural sectional view showing a third embodiment of the invention. It is a structural sectional view. In FIG. 1 showing the first embodiment, 1 is GaAs.
5I substrate, 2 is n-・AQXQ ax -X As cladding layer, 3 is n''# A11.Ga1-yAs active layer (x)y), 4 is n-AllGaAs cladding layer, 5 is n+・GaAs Cap layer, 6 is Zn, B
In the region where 2 to 3×101sa11-3 of p such as e and Cd are diffused, the broken line in the figure indicates a pn junction.

7 is a p-electrode, and 8 is an n-electrode. When manufacturing the above semiconductor laser, liquid phase epitaxial method (LPE method), molecular beam epitaxial method (MBE method) is applied on semi-insulating SI substrate 1.
method), metal organic vapor phase epitaxial method (MOVPE method)
etc. by.

The above-mentioned cladding layer 2, active layer 3, cladding layer 4° and cap layer 5 are epitaxially grown in this order.

. Si, Ss, Sn, etc. are used as a type dopant, and the thickness of the cladding layer 2 and the cladding layer 4 is controlled to be about 1 to 1.5-1, and the thickness of the active layer 3 is controlled to about 0.05 to 0.4. Next, in order to diffuse Zn or Cd, approximately 0.2 to 0.3p of SiN or 5in2 is deposited by p-CVD or sputtering, a diffusion region is defined by photolithography, and a 50% film is deposited by RIE or wet etching.
The insulating film in the diffusion part is made thinner by about 0 people, and the diffusion concentration during Zn diffusion is controlled to be 2 to 3 x 10 "am-". Next, Zn is diffused at 600 to 700° C. and controlled so that the diffusion front reaches the SI substrate 1. The above p+ diffusion can also be achieved by implanting Be or other ions.

After that, p+n+ formed in the GaAs cap layer 5
The junction is separated by wet etching, and a ridge is formed by RIE or wet etching so that the p+n+ junction shown by the broken line is included in the ridge portion as shown in FIG. In the structure formed in this way, P+・G
The width of the aAs light emitting layer is determined by the bridge guide width (d=2 to 5 tones), and a refractive index waveguide structure is realized to effectively confine light.

In other words, if the depth of the ridge recess extends to the active layer 3, the light confinement force 1 can be achieved more efficiently.
If the active W3 is exposed, the characteristics will deteriorate due to the instability of the surface, so in the present invention, the depth is limited to reach the cladding layer 4 in contact with the active layer 3.

Even with the above method, the leaking portion of light can be sufficiently confined in the cladding layer 4, so that as a result, the confinement efficiency of the active layer 3 is also improved. When a current is injected from the p-electrode 7 and drawn to the n-electrode 8, laser oscillation occurs in the active layer below the ridge defined by the width d, and a stable transverse mode is obtained.

A second embodiment of the present invention shown in FIG. 2 is a case where the ridge depth tR on the n+ side in the first embodiment is set to zero, and when n=p)2 to 3X10"ai-', the p-type The waveguide structure is realized by taking advantage of the fact that the refractive index of the N-type is higher than that of the N-type and the effective bandgap of the P-type is smaller.Depending on the doping, tR varies from zero to the thickness of the cladding layer. Optimum lateral light confinement can be achieved by setting within the range of .

A third embodiment of the present invention shown in FIG.
It is realized inside the substrate 1 and has a rib waveguide shape. The refractive index in the lateral direction can be considered in the same way as in the first embodiment.

However, in the first embodiment, the lateral refractive index difference was achieved by providing an air layer in the cladding layer on the front surface side, whereas in this embodiment, the cladding layer 2 on the back surface (substrate) side was provided with a G
The difference is that a refractive index difference is provided between a As and the Zn doped layer. In addition, in the first embodiment, since the machining is performed on a portion close to the surface, it is possible to form a vertical ridge wall surface, but in this embodiment, the only difference is that a 7-shaped groove is formed due to processing constraints. 0 The manufacturing method of this example is first S
After forming a V-groove in the I-substrate 1 by wet etching, a laser epitaxial film is sequentially grown in the same manner as in the above embodiment.

The p+ region is formed by Zn diffusion, etc., and the p+n+ junction formed in the GaAs cap layer 5 is separated by wet etching to form the p-electrode 7. ``The n-electrode 8 is formed to obtain a lateral junction semiconductor laser.The operation of the semiconductor laser according to this embodiment is similar to that of the above embodiment.

〔Effect of the invention〕

As described above, the semiconductor laser according to the present invention and the method for manufacturing the same include n-・AQx Ga
l−x A s cladding layer, n ” ” A+1yG
a1-yAs active layer (where x>y), n-AD, x
Ga 1- xA 9 cladding layer and n+ GaA
A laminated layer consisting of an s cap layer and a p layer formed on the laminated layer.
The pn junction formed in the n+ GaAs cap layer is separated, and the ridge structure or V-groove structure provided along the pn junction eliminates the problem of high temperatures in the past. By minimizing the yield loss and damage to the semi-insulating substrate due to Zn diffusion, we incorporated a ridge waveguide into the laser emitting part, realized a more complete waveguide structure with good reproducibility, and achieved stable transverse mode oscillation. It has the advantage of being

Furthermore, since a high-temperature process is not used, the semiconductor light source can be suitable for integration with MESFETs.

[Brief explanation of the drawing]

FIG. 1 is a structural sectional view showing a first embodiment of a semiconductor laser according to the invention, FIG. 2 is a structural sectional view showing a second embodiment of the invention, and FIG. 3 is a structural sectional view showing a third embodiment of the invention. Structural cross section,
FIG. 4 is a cross-sectional view of a conventional lateral junction laser. 1... Semi-insulating GaAs substrate 2-n --AaXGal-XAs cladding layer 3 =-n'' ・AQyGat-yAs active layer 4-n
-MxGal-yAs cladding layer 5...n+・G a
A sCharap layer 6...p+territory

Claims (1)

[Claims] 1. On a semi-insulating GaAs substrate, n^-・Al_xGa
_1_-_xAs cladding layer and n^+・Al_yGa
_1_-_yAs active layer (where x>y) and n・Al
_xGa_1_-_xAs cladding layer and n^+・Ga
The pn junction formed in the n^+ GaAs cap layer is separated and the pn junction is provided along the pn junction. A semiconductor laser having a ridge structure or a V-groove structure. 2. The above ridge structure has the above n・Al_xGa_1_-
The semiconductor laser according to claim 1, characterized in that the semiconductor laser is provided in a _xAs cladding layer. 3. The semiconductor laser according to claim 1, wherein the V-groove structure is provided within the semi-insulating substrate. 4. On the semi-insulating GaAs substrate, n^-・Al_xGa
_1_-_xAs cladding layer and n^+・Al_yGa
_1_-_yAs active layer (where x>y) and n・Al
_xGa_1_-_xAs cladding layer and n^+・Ga
After sequentially stacking an As cap layer and forming a diffused p^+ region in the stacked layers, the pn junction formed in the n^+ GaAs cap layer is separated, and a ridge structure is formed along the pn junction. manufacturing method for semiconductor lasers. 5. The method for manufacturing a semiconductor laser according to claim 4, wherein the ridge structure is a V-groove structure formed in a semi-insulating substrate prior to the formation of the laminated layer.