JPH03116795A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent deterioration and optical damages at an edge side and to enable formation of a semiconductor laser of high reliability and high output with good yield at a low cost by forming an active layer of ternary or more III-V compound mixed crystal whose combination length between III-group atom and V-group atom in crystal differs each other and by introducing a specified or more carrier density of silicon (Si) as impurity to at least an active layer near the edge side which becomes a reflection face or a projection face of light. CONSTITUTION:Si is introduced as impurity about 1X10<17>cm<-3> or more to ternary or more III-V compound mixed crystal whose combination length between III-group atom and V-group atom differs each other; then, a value of energy gap is recovered which is decided by composition rate of mixed crystal. By using this, Si is introduced to a reflection face or a projection face of light of a semiconductor laser to enlarge energy gap; thereby, a semiconductor laser having a window construction can be acquired. An n-type (Al0.4Ga0.6)0.5In0.5P clad layer 2, a Ga0.85In0.5P active layer 3, a p-type (Al0.4Ga0.6)0.5In0.5P clad layer 4, and a p<+>-type GaAs cap layer 9 are formed one by one on an N-type GaAs substrate 1 by MOVPE method. A V/III rate is made 400 and non-dope. Si is ion-implanted as impurity only to an area near an edge side 8 and annealing is carried out. Thereby, an active layer part at an area near the edge side is allowed to have a carrier concentration of 2X10<7>cm<-3>.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a highly reliable and high output semiconductor laser.

(Prior Art) It has been conventionally believed that the energy gap of a III+V compound mixed crystal is uniquely determined by its composition.

However, for example, metal organic pyrolytic vapor phase epitaxy (MOVPE)
Like GaInP and AIGaInP grown by
Growth temperature, group V raw material to group III raw material ratio in gas phase (V/II
It has been shown that even if the mixed crystal composition is constant, the energy gap can vary depending on impurity doping, etc. (for example, the 34th Spring 1987 Applied Physics Conference Lecture Proceedings Volume 1, Lecture). Number 28p-ZA
-4 and 28p-ZA-5 (1987)). That is, using a certain combination of growth temperature and V/III ratio value, the energy gap of GaInP or AIGaInP is at most 50 to 80 meV smaller than the value normally known for mixed crystals. Also, 5X1017~
When impurities (n-type or p-type may be used) are introduced in an amount of 8 cm -3 or more per cut, the reduced energy gap value is restored to the original value of the mixed crystal. This is due to Ga-P in GaInP and In-P or AI in AIGaInP.
This occurs in association with immiscible regions due to different bond lengths between -P and In-P, and between Ga-P and In-P. Therefore, Al-As in AlGaAs and Ga-
This phenomenon was not observed significantly in materials with almost equal bond lengths, such as As. GaInAs and AlGaInAs
, or GaAsSb, etc., in which group III-
■A similar phenomenon occurs in structures composed of groups with different bond lengths.

Using this phenomenon, GaInP and AIGaInP
In a semiconductor laser whose active layer is a ternary or more III+V compound mixed crystal in which the bond lengths between group III atoms and group II atoms are different from each other in a crystal such as Add impurities to the active layer at a carrier concentration of 5
×1017cm=A patent application was made in 1983 for a semiconductor laser with a diameter of
-171525 (Japanese Unexamined Patent Publication No. 64-014986). The structure of this conventional semiconductor laser is shown in FIG. In this semiconductor laser, zinc (Zn) is deposited at 1.5 x 1018 cm-3 in the active layer near the end facet.
It has been introduced to some extent. This Zn is Ga□ in the diffusion region 11
, 5In□, 5P active layer has a band gap of 1.85 eV after crystal growth, which is a value determined by the composition ratio of the mixed crystal 1,
It recovers to 92eV. The active layer of the continuous Zn diffusion region 5 has a larger band gap than the active layer of the light emitting part, and does not absorb oscillated light. In other words, it is a semiconductor laser with a window structure.

(Problem to be Solved by the Invention) In the prior art described above, in order to form a window structure,
Impurities were introduced into the semiconductor laser end face in an amount of 5×10 17 cm −3 or more. A typical example is zinc (Zn) as an impurity.
It is doped with 1.5 x 1018 cm-3.

The carrier concentration of an undoped active layer into which impurities are not introduced is usually on the order of 1.times.10.sup.16 cm.sup.-3. Therefore, there is a concentration difference of about 10 times at the interface between the impurity diffusion region and the active layer of the light emitting part, and when the semiconductor laser is operated for a long time,
There is a concern that impurities may diffuse into the active layer of the light emitting section, causing deterioration of laser characteristics and reliability. Also usually 1.5
Since impurities of X 10''cm-3 or more are introduced, defects caused by the impurities are likely to occur on the end facets, and there is a concern that the long-term reliability and high output characteristics of the semiconductor laser will be deteriorated.

An object of the present invention is to overcome the above-mentioned problems and provide a highly reliable and high output semiconductor laser.

(Means for Solving the Problems) The semiconductor laser of the present invention has a multilayer structure including an active layer, and is a ternary or more III + V compound mixed crystal in which the bond lengths between group III atoms and group II atoms are different from each other in the crystal. is the active layer,
It is characterized in that silicon (Si) is introduced as an impurity into at least the active layer in the vicinity of the end face, which serves as a light reflection surface or an emission surface, to have a carrier density of I.times.10.sup.17 cm.sup.-3 or more.

(Function) Si is added as an impurity to a ternary or more III+V compound mixed crystal in which the bond lengths between group III atoms and group V atoms are different from each other.
When it is introduced at a level of about 1017 cm-3 or more, the energy gap recovers to the value determined by the composition ratio of the mixed crystal. For example, Ga
When Si is introduced as an impurity into o, 5In□, and 5P, the energy gap recovers from 1.85 eV to 1.92 eV, which is determined by the composition, at a concentration of 1.0 cm -3 and 5P. Taking advantage of this, a semiconductor laser having a window structure can be obtained by introducing Si into the light reflection surface or emission surface of the semiconductor laser and increasing the energy gap there. Unlike the conventional method, the concentration is as low as 1×10170 m-3, so the diffusion of Si from the region where Si is introduced into the active layer of the light emitting part is very small, and there is no deterioration of the active layer.
Furthermore, defects caused by the introduction of Si at the end faces do not occur. Therefore, optical damage at the end face can be suppressed, allowing high output operation. In this way, GaInP and AIGa
In materials such as InP, I
A high output and highly reliable semiconductor laser can be obtained by introducing a semiconductor laser with a diameter of about 1017 cm to 5 x 1017 cm.

(Example) Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional side view of a semiconductor laser according to an embodiment of the present invention. An AIGaInP visible light semiconductor laser with a wavelength band of 600 nm is shown as an example. First, we will discuss the manufacturing process. An n-type (Alo, 4Gao, s) is formed on an n-type GaAs substrate 1 by metal organic vapor phase epitaxy (MOVPE).
o, 5Ino, 5P cladding layer 2, Gao, 5In□,
5P active layer 3, p type (A10.4G80.6) 0.51
A 1'10.5P cladding layer 4 and a p+ type GaAs cap layer 9 are grown in this order. The growth conditions for active layer 3 are a temperature of 650°C.
The C1V/III ratio was 400 and non-doped. Si is ion-implanted as an impurity only in the vicinity of the end face 8, and so
Anneal at o'c for about 1 hour. In this way, the active layer portion near the end face has a carrier concentration of 2×10 17 cm. The ion implantation front is n-(Alo, 4G
a□, 6) 0.5In□, 5P cladding layer 2 may be slightly penetrated. The total length of the resonator was 200 to 300 μm, and the Si ion implantation region 5 near the end face was approximately 20 pm inside from the end face. The end face 8 is made between the folds. The n-type electrode 7 is connected to the substrate 1.
On the side, p + -GaAs above the Si ion implantation region 5
Only the surface of the cap layer 9 is insulated with a 5i02 film 10, and p
A type electrode 6 is formed on the p+-GaAs cap layer 9.

The oscillation threshold of the thus obtained semiconductor laser increased by 5% or less compared to a semiconductor laser without an impurity implanted region. In the semiconductor laser of the present invention, end face deterioration is reduced, so reliability is significantly improved. Furthermore, since optical damage to the end face is prevented, the maximum optical output is improved several times. Furthermore, when creating this structure, the depth of Si insertion is not strictly controlled and the manufacturing process is easy. Therefore, the manufacturing yield is high and it can be manufactured at low cost.

The concentration of the Si ion implantation region is set to 1×1017 cm”~5 to fully demonstrate the effect and maintain high crystal quality.
Approximately X 1017 cm-3 is appropriate. Furthermore, since Si is effective at a low concentration of 7 cm -3 per cutting, there are no restrictions on the introduction method, control is easy, and the quality of the area around where Si is introduced will not be degraded. The introduction method may be diffusion, crystal growth doping, or other methods.

The present invention relates to GaInAs, AlGaInAs, GaA
Other materials such as sSb and InGaAsP may also be used. Further, the laser structure is not limited to the structure of this embodiment, and any structure such as a buried laser or a DFB laser having a diffraction grating can be applied.

(Effects of the Invention) As described above, according to the present invention, deterioration and optical damage at the end face can be prevented, and a semiconductor laser with higher reliability and higher output than conventional semiconductor lasers can be realized at a higher yield and at a lower cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a semiconductor laser according to an embodiment of the present invention as seen from the side, and FIG. 2 is a sectional view of a conventional example as seen from the side. In each figure, 1-n-GaAs substrate, 2--.n-(AIo, 4Ga□, 6)0.5In□,
5P cladding layer, 3-Ga□, 5In□, 5P active layer, "・p-(AIo, 4Ga□, 6)o, 5In□, 5P
Cladding layer, 5...Si ion implantation region, 6...p
type electrode, 7... n-type electrode, 8... end surface, 9... p
”-GaAs cap layer, 10...5i02 film, 1
1...Zn diffusion region.

Claims (1)

[Claims] It has a multilayer structure including an active layer, and contains group III atoms and V atoms in the crystal.
The active layer is a ternary or more III-V compound mixed crystal with different bond lengths between group atoms, and the carrier concentration is increased by impurity silicon (Si) in at least the active layer near the end face, which is the reflection surface or emission surface of light. 1 x 10^1^7cm^-^3
A semiconductor laser characterized by the above introduction.