JPH01268179A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser element of a structure having simple and excellent manufacturing yield by forming each clad layer in a 2-layer structure of a layer made of (AlyGa1-y)etaIn1-etaP (eta=approx. 0.5, x<y) on the side in contact with an active layer and a layer made of AlzGa1-zAs at the other side. CONSTITUTION:In a visible semiconductor laser element, a crystal layer is formed by a liquid crystalline growth method of an active layer 21 of approx. 0.1mum of thickness made of a material of P-type GazetaIn1-zetaP (zeta=approx. 0.5) corresponding to 670nm of oscillation wavelength, a carrier enclosure layer 22 made of a P-type (AlyGa1-y)eta In1-etaP (eta=approx. 0.5) layer of approx. 0.02mum of thickness, a light confining layer 23 made of a P-type Al0.6Ga0.4As layer of approx. 0.3mum of thickness, a lower clad layer 24 made of the layers 23, 22, a carrier enclosure layer 25 made of an N-type (AlyGa1-y)eta In1-etaP (eta= approx. 0.5) layer of approx. 0.02mum of thickness, a light enclosure layer 26 made of an N-type Al0.6Ga0.4As layer of approx. 0.3mum of thickness, an upper clad layer 27 made of the layers 25, 26, and an ohmic contact layer 28 made of a material of N-type GaAs for obtaining an ohmic electrode.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a semiconductor laser device.

(Prior Art) Conventionally, a crystal layer for laser operation in a semiconductor laser device is formed by epitaxial growth on a substrate crystal, and therefore a substrate crystal that is lattice-matched with the epitaxial crystal layer is required. Furthermore, compound semiconductor crystals of sufficient quality to be used as substrates are currently GaA
In order to manufacture a semiconductor laser device, it is necessary to use a crystal that is lattice-matched to GaAs or InP.

From this, 600nI11 to 700nI11
Conventionally, the active layer material of a visible light semiconductor laser that outputs light in the wavelength band of (AβG al-x ) g In P (ξ=
approximately 0.5)xl-cage crystals are chosen. By changing the composition parameter This is because it can be adjusted to leV.

In order to obtain practical characteristics, a so-called DH structure (Double Heterostructure
Is it necessary to form a ure? This requirement regarding the band gap of the cladding layer is such that excess carriers in the active layer obtained by current injection can be efficiently confined in the active layer.
This is to create a large energy inversion state necessary for laser oscillation. In order to obtain a semiconductor laser device that operates continuously at room temperature, the difference in band gap must be △Eg≧about 0.3 eV...
...■ is necessary. On the other hand, the refractive index requirement for the cladding layer is to confine the laser light in the active layer, and Δn/n = 5 to 10%...
... A relative refractive index difference of ■ is required. This value is
This is because the slab type optical waveguide formed by the active layer and the cladding layer satisfies the single mode condition.

The material of the cladding layer that satisfies these conditions is made of the same element as the material of the active layer (A J2 Ga 1, ) g I n
It is a Pyl-η (η-about 0.5, y<x) crystal. In this material, E g (y) = 1.9+〇, 52y (
eV) =■1'or(AJ2 Ga1.
)y) I n Py
1-wa (0≦y≦0.83, η=about 05) n (y) -3,65-0,4y ・・
...■for(AJ2 Gaty)r) In
The following approximate expression holds true: Py''-ri (η=about 0.5)

In addition, the bandgap giving formula 1 is the bandgap of direct transition necessary for laser oscillation.
agap) and 2.33 at Y = 0.83
Take the maximum value of eV. In addition, when 0,83<y≦1, the band gear t”7 is of indirect transition type (Indirect
t bandgap) and takes a maximum value of 2.35 eV at y=J, which is not used as an active layer material but can be used as a cladding layer material. On the other hand, from the above equations ■ and ■ regarding the refractive index, y−x≧0.4
5～0.90・・・・・・・・・■
The following conditions are obtained.

An example of the structure of a visible semiconductor laser device manufactured satisfying the above conditions is shown in Fig. 3 (IEICE technical research report 0QE87-30-46, (June 22, 1987
p, 11.5, Ishikawa).

As shown in the figure, n-GaAs substrate 1 is coated with n-GaAs.
As buffer layer 2, n-A, gInP first cladding layer 3
, Ga1nP active layer 4, p-A,9InP second cladding layer 5, n-GaAs current blocking layer 6, p-GaAsc
An ap layer 7 and a p-GaAs contact layer 8 are formed.

The active layer 4 is made of G a g I n 1-g P corresponding to x=O. The cladding layers 3 and 5 are made of Air, In1-, and P corresponding to y=1. The oscillation wavelength is about 680 nm. be.

The epitaxial layer including the active layer 4 of this semiconductor laser device is formed using the MOCVD method (IIetal organic
-5=Chemical Vaper Deposits
) is made by. In the crystal obtained by the current MOCVD method, if the composition ratio of easily oxidized Ai is high,
There are many problems related to crystal quality such as high electrical resistance. Therefore, as in this example, the composition of the active layer 4 that does not contain Ai is close to practical application, and the composition of the active layer 4 that contains A and 12, that is, the practical application of semiconductor laser devices with an oscillation wavelength in the early 800 nm range. There are many difficulties.

Also, regarding the cladding layer, it is customary to lower the AJ2 concentration than in this example (set η = 0.3 to 0.7) for the purpose of lowering the electrical resistance, even at the cost of weakening carrier confinement. .

On the other hand, liquid phase crystal growth (LPE) is used in a wide range of fields from mass production to research of semiconductor laser devices.
d Phase Epitaxy), it has been difficult to manufacture visible semiconductor laser devices due to the following reasons. That is, in LPE (Ai G a L-x ) 5 1 n P
In order to obtain x L-g (ξ=about 0.5), use In as a solvent, AJ2, Ga.

A solution containing As as a solute is used; in this case, the segregation coefficient of A and 9 is extremely large. That is, 1'Ax = X5olb+ / Xlt, Iru
id ~10' ・---------・-■P
or the growth of (An2 Ga1-x8 ■n P(ξ=approx. 0.5)
xl-color. However, X is the mole fraction of A° C. in the same phase, and Xl+1 μmd is the mole fraction of A° C. in the liquid phase. This value is the value in the case of LPE of An2GaAs, see F=X5ol+d/Xl+%t+jcl
~102 ・・・・・・・・・■for
the growth of A 12 G a
It is one order of magnitude larger than A sz l-z. Therefore, as the crystal growth progresses, the depletion of 8λ in the liquid phase progresses more rapidly.

Therefore, since the composition of the resulting crystal is also depleted in A more rapidly, the thickness of the crystal that can be considered to have a uniform composition is (AN G
at I n P is better
l- is also about two orders of magnitude smaller than that of An2GaAs.

z 1-z The thickness of the crystal that can be considered to have a uniform composition obtained by LPE is A
In the case of β Ga As, at most 3~z 1-
Since z is 5 μm, (ANG at □) (In the case of In P, o, oa to X 1-color 0.
05 μm. This thickness is not sufficient for the active layer, but is completely insufficient for the cladding layer. A cladding layer with a thickness of at least 1 μm is required to form an optical waveguide. Therefore, LPE is not suitable for manufacturing such visible semiconductor laser devices.

However, manufacturing a visible semiconductor laser device using LPE is not only because the LPE device is much cheaper, simpler, and safer than the MOCVD device, but also because the structure for stabilizing the transverse mode of the semiconductor laser device, i.e. It has the appeal of being easy to create refractive index type optical waveguides, so it is hard to abandon it. As an example of a visible semiconductor laser device proposed to meet this requirement, the structure shown in FIG. 4 is known (IEICE technical research report 0QE87-30~4 [i,
987/6/22, p. 91, Kishino et al.).

The semiconductor laser device of this example has on an n-GaAs substrate 9,
n-AJ2GaAs first cladding layer 10, Ga1nAs
P active layer 11, p-A, fiGaAs second cladding layer 1
2. A p-GaAs contact layer 13 is formed.
, the cladding layer 10.12 is made of AnGaAs. According to this report, the refractive index of this 0.7, 0.3 cladding layer is at a wavelength of 670 nm.
3.29 for light of m, and the above-mentioned 0 regarding the refractive index
meets the requirements of the formula.

However, another requirement for the cladding layer, the requirement of the above-mentioned equation 0 regarding the bandgap, is not met as explained below. An2G
The bandgap of aAs is approximated by the following equation.

E g (Z) ~1.424 +1.247z(fo
r O≦z<0.40) -1,900+0.125z+0.143z 2(fo
r 0.40≦2≦1)...0 In this example, z=0.7, so E g = 2.
It becomes 06e■. On the other hand, the band gap of the active layer is 1, 9, which corresponds to the oscillation wavelength of 670 nm. Since it is OeV, the difference is 0.16 eV, which does not satisfy the requirement of the above-mentioned formula 0. Therefore, the semiconductor laser device of this example has poor temperature characteristics and cannot operate continuously at room temperature.

(Problems to be Solved by the Invention) In this way, visible semiconductor laser devices with conventional structures are capable of continuous operation at room temperature using a liquid phase crystal growth method, which is relatively inexpensive, simple, and safe as a crystal growth method. On the other hand, even if produced using the MOCVD method, (1!, Qat-y) I I n, ,
There was a problem in that the quality of the P crystal was unstable and the manufacturing yield decreased.

The present invention was made to solve the above-mentioned problems, and the present invention has been made to solve the above-mentioned problems.
A semiconductor laser with a structure that is simple and has an excellent manufacturing yield by having a structure that minimizes the thickness of Ga)'1'In1-, Py1-y (y≠0, η-about 0.5) The purpose is to provide an element.

[Structure of the Invention] (Means for Solving the Problems) A semiconductor laser probe of the present invention includes a substrate made of GaAs, and (Aβ Ga 1-x) 5 I n P ′.
(ξ - about 0.5); and a cladding layer formed on the upper and lower surfaces of the active layer and made of a semiconductor material with a smaller refractive index and a larger band gap than the active layer. , the side of each cladding layer in contact with the active layer is (AJ2 Gaty)q In P
z
l-z.

(Function) The minimum thickness of the carrier confinement layer necessary to ignore the amount of carriers injected into the active layer escaping due to tunneling effect is several hundred angstroms at most, and it can also be fabricated by liquid phase crystal growth. It is thick. Also, if the thickness is around this level, (Ai Ga 1y ) q
The electrical resistance of I n P is high
1-η Even if it is at least high, it can be ignored in terms of device design. Therefore, it becomes possible to manufacture a visible semiconductor laser device using the liquid phase crystal growth method. Further, a semiconductor laser device can be manufactured by MOCVD without causing a decrease in manufacturing yield due to an increase in electrical resistance.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a visible semiconductor laser device of an example manufactured by a liquid phase crystal growth method.

An active layer 21 with a thickness of about 0.1 μm made of p-GaBI-ξP (ξ=about 0.5) corresponding to an oscillation wavelength of 670 nm, and a p-GaBI-ξP with a thickness of about 0.02 μm.
Kitwayaria confinement layer 22 consisting of Aj2+) I n P (77=about 0.5) layer, pAJ'G with a thickness of about 0.3 μm
a An optical confinement layer 23 consisting of an As layer, a lower cladding layer 24 consisting of two layers, the optical confinement layer 23 and the carrier confinement layer 22, with a thickness of about 0.0
Yaria confinement layer 25 of 2 μm, n-AJ2 approximately 0.3 μm thick
Optical confinement consisting of Ga As layer 0.6 0
．． 4 layer 26, an upper cladding layer 27 consisting of two layers, carrier confinement layer 25 and optical confinement layer 26, and an ohmic contact layer 28 made of n-GaAs for obtaining an ohmic electrode, are made by liquid phase crystal growth. It is a crystal layer formed by

The substrate 29 includes a p-GaAs plate 30 with a thickness of about 100 μm and a current blocking layer 3 made of an n-GaAs layer with a thickness of about 1 μm.
It is composed of 1.

Grooves 32 with a width of approximately 3 μM run in stripes on the surface of the substrate 29
is provided to stabilize the transverse mode to the lowest order. Note that since this groove 32 penetrates the current blocking layer 31, the excitation current injected from the metal electrodes 33, 34 is limited to the vicinity of the upper part of the groove 32. This is called an internal stripe structure, and it is an excellent structure with low reactive current that has been put into practical use in near-infrared semiconductor laser devices made of (AJ2Ga)As. It is a structure that can only be manufactured by In the figure, numerals 35 and 36 are cleavage planes perpendicular to the striped grooves 32, which are mirror surfaces for the laser resonator. The semiconductor laser device thus manufactured was continuously operated at room temperature at an oscillation wavelength of B70 nm, and desired results were obtained.

The embodiment shown in FIG. 2 is a visible semiconductor laser device manufactured by the MOCVD method. The difference from the conventional example is the structure of the cladding layers on both sides of the active layer 40. That is, the cladding layers 41 and 42 are each composed of a carrier confinement layer 42 and a light confinement layer 45 and 476. Reference numeral 47 is an n-GaAs substrate.

According to this example, even though the Aβq In P used for the carrier confinement layers 43 and 44 had a high long-term electrical resistance, the thickness of the layer was extremely thin, so it did not adversely affect the manufacturing yield.

In the above two examples, the material of the active layer was either Ga3InP (ξ=about 0.5), or (Aj2Ga1-x)IInP(ξ-about 0). .5) xl-! Even if this happens, the effects of the present invention will not be lost. In addition, Ga of the substrate
Although lattice matching is achieved with the As crystal, the effects of the present invention are not lost.

[Effects of the Invention] As explained above, according to the present invention, it is possible to manufacture a semiconductor laser device using a liquid phase crystal growth method,
Furthermore, a semiconductor laser device can be manufactured by MOCVD without decreasing the manufacturing yield due to an increase in electrical resistance.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a semiconductor laser device according to an embodiment, FIG. 2 is a sectional view showing the structure of another embodiment of the present invention, and FIG. 3 is a structure of a conventional semiconductor laser device. 4 is a sectional view showing the configuration of another conventional device. 21... Active layer 22.25... Carrier confinement layer 23.24... Optical confinement layer 24... Lower cladding layer 27...
. . . Upper cladding layer 29 . . . Substrate 40 . . . Active layer 41 . . . Lower cladding layer 42 .
...Top cladding layer 43,44...Carrier confinement layer 45,46...Light confinement layer 47...Substrate applicant Toshiba Corporation Patent attorney Suyama Sa -

Claims (1)

[Claims] A substrate made of GaAs, (Al_xGa_1_-_x)_ξIn_1_-_ξP
(ξ=about 0.5); and a cladding layer formed on the upper and lower surfaces of the active layer and made of a semiconductor material having a smaller refractive index and a larger band gap than the active layer. , the side of each cladding layer in contact with the active layer is (Al_
A semiconductor laser device characterized in that it has a two-layer structure in which one layer is made of yGa_1_-_y)_ηIn_1_-_ηP (η=approximately 0.5, x<y) and the other side is a layer made of Al_ZGa_1_-_ZAs.