JP2990009B2 - Semiconductor laser and method of manufacturing semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser, and more particularly to a method for manufacturing a semiconductor laser capable of high-power operation.

[0002]

2. Description of the Related Art In recent years, semiconductor lasers have been widely used in information equipment, optical communications, and the like. In particular, a semiconductor laser used for an information storage device such as a magneto-optical disk requires a high output operation. The high output operation of the semiconductor laser involves deterioration due to light absorption at the end face, and it is necessary to suppress this.
To realize a semiconductor laser capable of high output operation, for example, Arimoto et al. (IEJ Journal of Quantum Electronics (IEEE Jour)
nal of Quantum Electronic
s) Magazine Vol. 29, No. 6, pp. 1874-1879) proposes the manufacture of window lasers by impurity diffusion.

FIG. 3 is a structural diagram of a semiconductor laser having a window structure obtained by disordering a natural superlattice on an end face. In this figure, 1 is an n-GaAs substrate, 2 is n-AlGaInP
Clad layer, 3 a GaInP active layer, 4 a p-AlGa
InP cladding layer, 5 is a GaInP etching stopper layer, 6 is a p-AlGaInP cladding layer, 7 is n-Ga
As current blocking layer, 8 is a p-GaAs cap layer, 9
Is a p-electrode, 10 is an n-electrode, 15 is a window region, 20
Is the end face of the resonator.

First, the operation will be described. p electrode 9,
When a voltage is applied to the n-electrode 10 in the forward bias direction, light emission recombination of the injected carriers occurs in the active layer 3. The resonator end faces 20 facing in parallel form an optical resonator, and emitted laser light is emitted from the resonator end faces 20. By the way, the active layer 3 is GaInP in which the ordered state of the natural superlattice is maintained, whereas the window region 15 near the end face is GaInP in which the natural superlattice is disordered.
It is. Therefore, in the window region 15, the band gap energy of the active layer is larger than that of the emitted laser light, and the light absorption of the emitted laser light at the cavity end face 20 is reduced. As a result, deterioration of the resonator end face 20 can be prevented, and high-output operation can be performed.

FIG. 6 is a cross-sectional view showing a method of manufacturing this conventional window structure semiconductor laser as viewed from the lateral direction. In this figure, the same reference numerals as those in FIG. 3 denote the same components, 16 is a SiN mask, 17 is a Zn diffusion source ZnO: S
iO ₂ and 18 are SiO ₂ caps, and 19 is an opening.

Next, the manufacturing method will be described. First, as shown in the cross-sectional view of FIG.
N-cladding layer 2, active layer 3, p-cladding layer 4, etching stopper layer 5, p-cladding layer 6 by PE method
Are sequentially formed. Next, a SiN mask 16 is formed on the p-cladding layer 6, a stripe-shaped opening 19 is partially formed by photolithography and etching, and a Zn diffusion source 17 and a SiO ₂ cap 18 are sequentially formed thereon. I do. Further, by annealing this in a sealed tube, Zn is diffused from the opening 19 to form the window region 15 in FIG. Next, the SiO ₂ cap 18, Z
After removing the n-diffusion source 17 and the SiN mask 16, the mesa 21 is selectively etched to remove the n-current blocking layer 7, p
Forming the cap layer 8; Further, an n-electrode 10 and a p-electrode 9 are formed, cleaved at the window region 15, and separated into chips. Thus, a semiconductor laser having window regions 15 at both ends of the laser is obtained.

[0007]

As described above, in the conventional window laser, the natural superlattice is disordered by diffusion of impurities. By the way, when the impurity concentration in the active layer is insufficient, GaInP in an ordered state remains and the light absorption does not decrease. Conversely, as the impurity concentration increases, light absorption increases due to free carrier absorption and band tail increase, and the threshold current increases and the slope efficiency decreases seriously. In other words, the formation of the window due to the disorder of the natural superlattice causes the deterioration of the oscillation characteristics of the semiconductor laser.

On the other hand, for example, in J. E. FIG. Zucker et al. (Applied Physics Letter (Applied Ph)
ysics Letters), Vol. 60, No. 24, 30
36-3038 (1992), the ion implantation of P ions and subsequent annealing
Disordering the As / InP quantum well to increase the band gap energy, and reducing the light absorption due to free carrier absorption by setting the implanted ion species to P ions which are the same group III or V elements as the constituent elements of the quantum well. It is shown to be.

However, when a window structure semiconductor laser is manufactured by implanting P ions into a general multiple quantum well structure (superlattice structure), it must be implanted with a large energy. 360
At a keV dose of 2.5 to 10 × 10 ¹⁴ cm ⁻² , many crystal defects are caused in the window region, resulting in deterioration of the semiconductor laser.

It is an object of the present invention to provide a highly reliable semiconductor laser having a window structure which does not absorb light in a window region.

[0011]

SUMMARY OF THE INVENTION The present invention comprises a step of forming a semiconductor layer including an active layer of a III-V compound semiconductor having a natural superlattice structure on a semiconductor substrate; Implanting group-V or group-V ions, disordering the natural superlattice structure of the active layer in the portion implanted by annealing, and fabricating a laser cavity end face in the ion-implanted portion. A method for manufacturing a semiconductor laser.

Or III-V having a natural superlattice structure
AlGaInP or GaIn as the group III compound semiconductor
A method for manufacturing a semiconductor laser as described above, wherein P is formed.

Alternatively, in the above-described method for manufacturing a semiconductor laser, the ions to be implanted are N ions or B ions.

Alternatively, III- having a natural superlattice structure
An active layer made of a group V crystal is provided, and group III or group V ions are implanted only in the laser cavity facet region which becomes a light reflection or emission surface, and that the natural superlattice structure of the implanted portion is disordered. It is a semiconductor laser characterized by the following.

Alternatively, the natural superlattice structure is AlGaInP
Alternatively, the semiconductor laser is a GaInP natural superlattice.

[0016]

In the present invention, since the natural superlattice layer is disordered by ion implantation, damage to the window region can be reduced. In particular, when ion implantation is performed using N ions lighter than P ions, damage to the window region can be further reduced. For example, in order to perform ion implantation into the active layer through 0.2 μm of (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P clad, energy of 180 keV is required for P ions, but energy of 100 keV is sufficient for N ions. This enables a highly reliable operation of the semiconductor laser. The degree of disorder depends on the amount of implanted ions.

Conventionally, for example, Hirayama et al. (Japanese Journal of Applied Physics (Japanese)
nice Journal of Applied P
physics, Vol. 24, No. 11, pp. 1498-150
According to page 2 (1985), no disordering of the GaAs / AlAs multiple quantum well was observed in the ion implantation of B ions. It has also been considered that N ions, which have substantially the same mass as B ions and are III-V elements as well as the constituent elements of the crystal, do not show disorder.

However, regarding the disorder of the natural superlattice, N
Ion implantation and annealing are effective. This is considered to be because the natural superlattice is composed of one atomic layer and a sufficiently thin unit as compared with a general multiple quantum well (superlattice). For this reason, a window-structure semiconductor laser can be realized by ion implantation of N ions and annealing. The same applies to B ions.

Even when P ions are used, when the natural superlattice is disordered, a smaller amount of ion implantation is required as compared with a normal superlattice, and damage to the ion implantation region can be reduced.

[0020]

An embodiment of the present invention will be described below with reference to FIGS. 1A to 1C are cross-sectional views viewed from a lateral direction for explaining an embodiment of a method for manufacturing a semiconductor laser according to the present invention, and FIG. 2 illustrates an embodiment of a method for manufacturing a semiconductor laser according to the present invention. FIG.

First, the manufacturing method will be described. First, Figure 1
1A, an n-AlGaInP cladding layer 2, a GaInP active layer 3, a p-AlGaInP cladding layer 4, a GaInP etching stopper layer 5, and a GaAs cap layer 11 are formed on an n-GaAs substrate 1 by, for example, MOVPE. Form sequentially. Next, as shown in FIG. 1B, an SiO ₂ film 12 and a photoresist 13 are formed on the cap layer 11, and a stripe-shaped opening 14 is partially formed by a photolithography technique and an etching technique. SiO ₂ film 12 and photoresist 13
Is used as a mask to implant N ions from the upper surface.

Next, as shown in FIG. 1C, the photoresist 13, the SiO ₂ film 12, and the cap layer 11 are removed.
A P-AlGaInP cladding layer 6 is formed thereon by MOVPE.
Grow by law. The growth of this cladding layer also serves as annealing after ion implantation. However, the annealing can be performed separately from the growth.

Next, as shown in FIG. 2, a mesa 21 is formed by a mesa forming process. As shown in the structural diagram of FIG. 3, the n-GaAs current blocking layer 7 and the p-GaAs
An s cap layer 8 is formed. Further, an n-electrode 10 and a p-electrode 9 are formed, cleaved at the window region 15, and separated into chips. Thus, a semiconductor laser having a window structure at both end surfaces is completed.

FIG. 4 is a diagram showing the effect of the present invention. The horizontal axis is the dose, and the vertical axis is the photoluminescence peak wavelength. By performing annealing after ion implantation of N ions, the PL peak wavelength shifts to the high energy side of 60 meV, and the band gap energy increases.

The semiconductor laser obtained according to the present invention does not contain any element other than the group III or V element in the window region, so that there is no free carrier absorption, so that an increase in threshold current and a decrease in slope efficiency can be suppressed. In addition, light N
Since the window region can be formed by ion implantation of ions, operation of the semiconductor laser with less damage in the window region, that is, highly reliable, can be realized.

In the above embodiment, the window region is formed by ion implantation of N ions and subsequent annealing. However, the same applies to the ion implantation of B ions which are group III elements having the same mass as N ions. effective.

FIG. 5 is a diagram showing the effect of the present invention. III
FIG. 4 is a comparison of the case where the GaInP natural superlattice structure is disordered with group V or group V ions and the case of a normal GaAs / AlGaAs superlattice. The horizontal axis represents the atomic number of the implanted ions, and the vertical axis represents the implanted ion density required for shifting the band gap to the high energy side of 60 meV. In the figure, a GaAs / AlGaAs quantum well (well thickness 3 n
The data of m. Leier (Journal of Applied Physics)
ied Physics, Vol. 67, No. 4, pp. 1805-1813, 1990).
Ne (atomic number 10), Mg (12), Ar (1)
8), white circles appeared for Zn (30). As an example of ion implantation into the natural superlattice according to the present invention, the case where the ions are N (atomic number 7), P (15), and Ga (31) are shown by black circles in the figure. The implanted ion density required for shifting the band gap to the high energy side of 60 meV is at least two orders of magnitude smaller in the case of a natural superlattice which is a monoatomic layer superlattice than in a quantum well having a well thickness of 3 nm. Therefore, if a natural superlattice is used, a window structure can be realized with a small amount of ion implantation.

The semiconductor laser obtained by the present invention has no free carrier absorption since the window region does not contain any element other than the group III or V element, so that the threshold current increases.
A decrease in slope efficiency can be suppressed. Further, since the window region can be formed with a smaller injection amount than in the multiple quantum well, it is possible to realize the operation of the semiconductor laser without deterioration due to damage in the window region, that is, with high reliability.

In the above embodiment, the window region is formed by ion implantation of N ions, P ions, and Ga ions and subsequent annealing.
A similar effect can be obtained with a group V or group V ion.

[0030]

As described above, in the semiconductor laser obtained by the present invention, the natural superlattice of the active layer in the window region is disordered by ion implantation of a group III-V element. In this case, the damage was small by more than two orders of magnitude and the window region contained no element other than the group III or V element, so that there was no free carrier absorption and the increase in threshold current and the decrease in slope efficiency could be suppressed. Further, when the window region is formed by ion implantation of N ions or B ions having a small mass, operation of the semiconductor laser with less damage in the window region, that is, more reliable operation can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method for manufacturing a semiconductor laser according to the present invention, as viewed from a lateral direction.

FIG. 2 is a diagram illustrating a method for manufacturing a semiconductor laser according to the present invention.

FIG. 3 is a structural diagram of a window-structure semiconductor laser obtained by disordering a natural superlattice on an end face.

FIG. 4 is a diagram for explaining the effect of the present invention.

FIG. 5 is a diagram for explaining an effect of the present invention.

FIG. 6 is a cross-sectional view showing a method for manufacturing a conventional window-structure semiconductor laser as viewed from the lateral direction.

[Explanation of symbols]

Reference Signs List 1 n-GaAs substrate 2 n-AlGaInP cladding layer 3 GaInP active layer 4 p-AlGaInP cladding layer 5 GaInP etching stopper layer 6 p-AlGaInP cladding layer 7 n-GaAs current blocking layer 8 p-GaAs cap layer 9 p electrode 10 n Electrode 11 GaAs cap 12 SiO ₂ mask 13 Photoresist 14 Opening 15 Window area 16 SiN mask 17 Zn diffusion source ZnO: SiO ₂ 18 SiO ₂ cap 19 Opening 20 Resonator end face 21 Mesa 22 Ion implantation

Continuation of the front page (72) Inventor Yoshiyasu Ueno 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-5-152675 (JP, A) JP-A-60-62179 (JP, A) JP-A-5-129721 (JP, A) JP-A-1-319981 (JP, A)

Claims (5)

(57) [Claims] 1. A semiconductor substrate having a natural superlattice structure on a semiconductor substrate.
A step of forming a semiconductor layer including an active layer of an IV group compound semiconductor; a step of implanting a group III or group V ion into a part of the active layer; A method for manufacturing a semiconductor laser, comprising: disordering a natural superlattice structure; and fabricating a laser cavity facet in the ion-implanted portion. 2. The method according to claim 1, wherein AlGaInP or GaInP is formed as the group III-V compound semiconductor having a natural superlattice structure. 3. The method according to claim 1, wherein the ions to be implanted are N ions or B ions. 4. An active layer comprising a group III-V crystal having a natural superlattice structure, wherein a group III or group V ion is implanted only into a laser cavity facet region which becomes a light reflection or emission surface. Wherein the natural superlattice structure of the semiconductor laser is disordered. 5. A natural superlattice structure having AlGaInP or G
5. A natural superlattice of aInP.
A semiconductor laser as described in the above.