JP2001320128A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser having a pin structure which is high in efficiency electrically and optically. SOLUTION: An Si doped n-type Al0.15Ga0.32In0.53As buffer layer 2 of 0.2 μm and an Si doped n-type Al0.48In0.52As layer 3 of 1 μm are grown on an n-type InP substrate 1. After a non-doped Al0.27-0.34Ga0.20-0.13In0.53As inclined layer of 50 nm is grown, a quantum well active layer 4 composed of an Al0.07 Ga0.25In0.68As layer of 8 nm and an Al0.27Ga0.20In0.53As layer of 10 nm 5, and a non-doped Al0.27-0.34Ga0.20-0.13In0.53As inclined layer of 50 nm, are grown. Successively, A carbon doped p-type AlAs0.56Sb0.44 layer 5 of 1 μm and a carbon doped p-type GaAs0.51Sb0.49 layer 6 of 50 nm are grown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor laser, and more particularly, to a pin having a high electrical and optical efficiency.
The present invention relates to a semiconductor laser having a structure.

[0002]

2. Description of the Related Art In general, a long-wavelength semiconductor laser in the 1.55 μm band is formed by growing a semiconductor layer on an InP substrate. The semiconductor material is GaInAsP.
System, AlGaInAs system, and AlGaAsSb system. In addition, these include Group III (B, Al, Ga, I
n, Tl) or a system in which an element of group V (N, P, As, Sb, Bi) is added. When the group III or group V is used, it is limited to an active layer or a special layer. Is the case. In addition, as the number of elements increases, growth becomes extremely difficult.

A conventional continuously grown laser uses a quaternary material of the same system and has a composition near the lattice constant of the substrate.
It forms a mold layer, an active layer, and a p-type layer. GaInAsP
In the system material, there are two kinds of group V elements, and there is a disadvantage that composition control is difficult. In addition, there is a disadvantage that the temperature characteristics are small because the difference (ΔEc) between the conduction bands cannot be made large. Further, in the AlGaInAs system, the group V element is 1
Although it is a kind, particularly in the case of metalorganic vapor phase epitaxy, it is difficult to form a good film due to the influence of oxygen and impurities in the case of AlGaInAs having a group III Al composition of 90% or more. Also, by increasing ΔEc,
In order to improve the temperature characteristics, it was necessary to increase the Al composition and strain the lattice.

[0004] In general, Zn is used as a p-type dopant. However, Zn has a disadvantage that it requires a large amount of Zn material because of its high vapor pressure, and it is difficult to obtain a steep p-layer because of its large diffusion constant. is there. In doping with carbon having a small diffusion constant, GaInAsP or AlGaIn
The material system of As has a drawback that it is easy to enter a group III site containing a large amount of In, which has a weak bond, and is unlikely to be p-type. on the other hand,
In the AlGaAsSb system, the dopant is Sb having a weak bond.
Group-dopant is likely to be p-type with a group IV dopant, and Si, which is generally used as an n-type dopant and has a small diffusion constant, also enters the group V and has n
There was a drawback that it was difficult to become a mold.

[0005] In addition, group VI dopants of S, Se, and Te are also used as n-type dopants, but they have problems in that they have a large diffusion constant, making it difficult to do steep doping, and have a high vapor pressure and a large memory effect. Therefore, when a pin type laser is continuously grown in the same material system, there is a problem in growth such as a memory effect when growing either conduction type, or a film having low dopant activation efficiency is grown. Due to the factors, the laser became electrically or optically inefficient. In the metalorganic chemical vapor deposition method, a film having good crystallinity is easily obtained, and the mass productivity is excellent. However, the properties of the dopant tend to be particularly remarkable.

[0006]

In a long-wavelength surface emitting laser, a DBR (Distributed Bragg®) having a high reflectance is used.
A method in which an eflector (distributed black reflector) is formed on a GaAs substrate, and a portion including an active layer formed later on an InP substrate is bonded, and a method in which all structures are grown on the InP substrate. There is. The former bonding method can produce a p-type DBR in which a GaAs substrate is doped with carbon. However, since the bonding interface is close to the active layer, there is a problem in element life and reliability due to impurities and defects. The latter, which is continuously grown, is easy to manufacture and has no impurities, defects, etc. near the active layer, but still has inferior characteristics to the former. As a factor, a thick film must be grown, and good growth is difficult, and the efficiency of either the p-type or the n-type dopant is poor as described above, and an electrically and optically good film can be obtained. It is conceivable that no structure having a high ΔEc is formed, an oxide confined structure is not formed, or the like.

At present, a surface emitting laser of AlGaAsSb is disclosed in, for example, F. Genty et al. J. Crystal. Growth 201/202.
(1999) pp. 1024-1027. This is a result of inferior crystallinity by molecular beam epitaxy, and the laser oscillation is caused by low-temperature optical excitation. Also,
For AlGaInAs, JPDebray et al. IEEE Photon
ics Technol. Lett. 11 (1999) pp. 770-772. Growing by MOVPE and oscillating by current injection pulse. , The properties are inferior.

Accordingly, the present invention provides a method of growing a good p-type and n-type film, and a semiconductor laser having a pin structure with high electrical and optical efficiency, particularly, low cost and good device characteristics.
The issue is how to manufacture a long-wavelength surface emitting laser on an InP substrate with high device life and high reliability.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a semiconductor laser having a pin structure that is electrically and optically highly efficient.

[0010]

SUMMARY OF THE INVENTION The present invention provides such an eye.
In order to achieve the target, the invention described in claim 1
_1-xyGa_yIn_xAs (x> 0.4) or Ga_1-xI
n_xAs_yP_1-y(X> 0.4) is an n-type layer and contains Sb.
Mu Al_xGa_1-xAs_1-ySb_y(Y> 0.4) with the p-type layer
The active layer.

Further, in the first aspect of the present invention, the n-type layer and the p-type layer further include an AlGaAsSb layer which is oxidized and confined.

Further, in the first or second aspect, the n-type layer and the p-type layer are DBRs.

Further, in the first, second or third aspect, the p-type layer contains any one of C, Si, Ge and Sn as an impurity.

Further, in any one of the first to fourth aspects, the n-type layer contains a C element as an impurity.

[0015] That is, the present invention is, Al _1-xy Ga _y In containing In in a laser structure is grown on an InP substrate
_x As _(x> 0.4) or _{Ga 1-x In x As y} P 1-y
(X> 0.4) is an n-type layer, and Al _x Ga _{1 -x} containing Sb
As _1-y Sb _y with (y> 0.4) characterized in that it is constructed as a p-type layer, also, DBR and p-type AlGaAs consisting of a n-type AlGaInAs or GaInAsP
It features a surface emitting laser structure including a DBR made of Sb, and has an AlGaAsS which is oxidized and confined in the vicinity of the active layer.
b, and as a p-type or n-type dopant, a group IV C, Si, Ge,
A semiconductor laser characterized by using Sn and capable of continuous growth by metal organic chemical vapor deposition.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a semiconductor laser for explaining a first embodiment of the present invention.
This semiconductor laser is formed on an n-type InP (100) substrate.
Buffer layer 2 (band gap wavelength: λg = 1.3 μm) of Si-doped n-type Al _0.15 Ga _0.32 In _0.53 As and Si-doped n-type Al _0.48 In _0.52 As layer 3
_Is grown to 1 μm, and non-doped Al _0.27-0.34 Ga
_0.20-0.13 In _0.53 As graded layer (λg = 1.0-1.1
μm) after growing 50 nm, 1% compressive strain Al _0.07
Ga _0.25 In _0.68 As layer (λg = 1.55 _μm ) 8 nm
/ Al _0.27 Ga _0.20 In _0.53 As layer (λg = 1.1 μm
m) Quantum well active layer 4 composed of 5 pairs of 10 nm, non-doped Al _{0.27 -0.34} Ga _{0.20 -0.13} In _0.53 As gradient layer (λg = 1.1-1.0 μm) is grown to a thickness of 50 nm, and subsequently carbon-doped p-type AlAs _0.56 1μ of Sb _0.44 layer 5
m, carbon doped p-type GaAs _0.51 Sb _0.49 layer 6 of 50 n
m is grown.

[0018] That _{is, Al 1-xy Ga y In} x As (x>
0.4) or _{Ga 1-x In x As y} P 1-y (x> 0.
4) is the n-type layer 3, and Al _x Ga _{1 -x} As _{1 -y} containing Sb
Has a configuration sandwiching the active layer 4 sb _y a (y> 0.4) as the p-type layer 5.

FIG. 2 is a diagram showing an energy band in the vicinity of the active layer during oscillation, in which undoped AlGaInAs and p
In this configuration, carriers are efficiently confined in the active layer due to a high ΔEc caused by a difference in electron affinity of the material system between -AlAsSb. The grown epi layer is formed by depositing AuZnNi / Au as a p-type electrode and etching it in a stripe shape with a hydrogen peroxide / sulfuric acid aqueous solution, and then etching the surface with Si.
Protected with O ₂ and AuGeNi / A on the back as n-type electrode
u was deposited. The end face was cleaved to produce a reflector, and the measurement was performed.

FIG. 3 is a diagram showing a current-light output curve. AlGaAsSb has a high ΔEc, so that carriers are efficiently confined. The carbon dopant is not diffused to the active layer during crystal growth, so that the active layer has better characteristics than Zn-doped one. Since the activation rate of the dopant is high and the influence of absorption by impurities is small, the conventional GaInAsP
It can be seen that both the threshold current and the differential efficiency are improved as compared with the system laser. It was also confirmed that the temperature characteristics were as high as AlGaAs laser due to the high ΔEc. Also, p
Similar effects were obtained even when a laser was fabricated by growing the substrate from AlGaAsSb on a substrate. Similar effects were obtained when the n-type layer and the active layer were made of GaInAsP.

(Embodiment 2) FIG. 4 is a structural view of a surface emitting laser for explaining a second embodiment of the present invention. This surface emitting laser is mounted on an n-type InP (311) B substrate 11. Al _0.15-0.34 Ga _0.32-0.13 In _0.53 with gradient composition in the middle
Optical length λ / 4 of low refractive index sandwiching As intermediate layer 10 nm
(Λ = 1550 nm) n-Al _0.15 Ga _0.32 In _0.53
As and n-Al _0.48 In _0.52 with a high refractive index and an optical length of λ / 4
After growing an n-type DBR 12 of 50.5 pairs of As, a spacer layer 13 of AlGaInAs including an active layer 13a having an optical length λ is grown, and subsequently, a graded composition of Al _0.16-0.9
Ga _0.84-0.1 As _0.52-0.56 Sb _{0 .48-0.44} intermediate layer 10n
p-Al _0.9 Ga having an optical length of λ / 4 with a low refractive index sandwiching m
_0.1- As _0.56 Sb _0.44 and p- of optical length λ / 4 with high refractive index
25 pairs of p-type D of Al _0.16 Ga _0.84 As _0.52 Sb _0.48
The structure is such that BR14 is grown. In addition, 14a is an oxidation constriction layer.

Here, a low-refractive-index layer several pairs from the active layer
AlGaAsSb with higher Al composition than other layers
In this case, selective oxidation is possible.
The third layer from Al_0.98Ga_0.02As_0.56Sb_0.44As layers
Was. After producing a circular pattern of 20 μmφ of SiNx,
Dry etching to the active layer, hydrogen peroxide, sulfuric acid
Etching with an acid aqueous solution
Al_0.98Ga_0.02As _0.56Sb_0.44The layer was selectively oxidized.
The diameter of the current constriction formed by selective oxidation was 5 μmφ.
Was.

Next, a ring-shaped p-electrode 23 having a diameter of 15 μm and made of AuZnNi / Au is formed on the wafer surface, the surface is protected with SiNx22, and Cr / A is formed on the upper side.
An n-electrode 21 made of AuGeNi / Au was formed below the wiring electrode made of u.

FIG. 5 is a diagram showing the fabricated surface emitting laser, and FIG. 6 is a diagram showing current-light output characteristics of the surface emitting laser shown in FIG. A surface-emitting laser with a light output of 1 mW or more at room temperature, a low threshold current, and a high efficiency was fabricated.

[0025]

As described above, according to the present invention, A
_{l 1-xy Ga y In x} As (x> 0.4) or Ga _1-x
In _x As _y P _1-y and (x> 0.4) and n-type layer, active layer _{Al x Ga 1-x As 1} -y Sb y (y> 0.4) containing Sb as a p-type layer , That is, n-type AlG
aInAs or GaInAsP and p-type AlGaAs
Since sSb is grown on the InP substrate, a dopant of C or Si having a small diffusion constant can be used efficiently, and a large difference in conduction band between AlGaAsSb and the active layer can be obtained. A highly efficient semiconductor laser is realized.

In particular, AlGaAsSb can increase the Al composition, and can achieve higher efficiency due to the oxide confinement structure. In addition, since a surface emitting laser structure having good characteristics can be continuously grown by the metal organic chemical vapor deposition method, it is possible to provide a laser device with low cost, high device life, and high reliability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a semiconductor laser of the present invention.

FIG. 2 is a diagram showing an energy band near an active layer.

FIG. 3 is a diagram showing current-light output characteristics.

FIG. 4 is a configuration diagram of a surface emitting laser of the present invention.

FIG. 5 is a diagram showing a manufactured surface emitting laser.

FIG. 6 is a diagram showing current-light output characteristics of the surface emitting laser shown in FIG. 5;

[Explanation of symbols]

Reference Signs List 1 n-type InP substrate 2 Si-doped n-type Al _0.15 Ga _0.32 In _0.53 As buffer layer 3 Si-doped n-type Al _0.48 In _0.52 As layer 4 Al _0.07 Ga _0.25 In _0.68 As layer / Al _0.27 Ga
_0.20 In _0.53 As quantum well active layer 5 As layer 5 Carbon-doped p-type AlAs _0.56 Sb _0.44 layer 6 Carbon-doped p-type GaAs _0.51 Sb _0.49 layer 11 n-type InPB substrate 12 n-type DBR 13 AlGaInAs spacer layer 13a active layer 14 p-type DBR 14a oxidation confinement layer 21 n-electrode 22 SiNx 23 p-electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F073 AA46 AA51 AA65 AA74 AB17 CA07 CA12 CA15 CA17 CB07 CB08 CB19 DA23 DA24 DA27 DA35 EA23

Claims (5)

[Claims] [Claim 1] _{Al 1-xy Ga y In x} As (x> 0.
4) or _{Ga 1-x In x As y} P 1-y and (x> 0.4) and n-type layer, Al containing _{Sb x Ga 1-x As 1} -y Sb y (y
> 0.4) with a p-type layer sandwiching the active layer. 2. The semiconductor laser according to claim 1, wherein said n-type layer and said p-type layer further sandwich an oxidation-constricted AlGaAsSb layer. 3. The semiconductor laser according to claim 1, wherein said n-type layer and said p-type layer are DBRs. 4. The semiconductor laser according to claim 1, wherein said p-type layer contains one of C, Si, Ge, and Sn as an impurity. 5. The semiconductor laser according to claim 1, wherein the n-type layer contains a C element as an impurity.