JPH0548201A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a laser having a short wavelength, by using an AlGaP material having a large band gap for its clad layers. CONSTITUTION:Through an AlGaP based material having a large band gap is used, for a clad layer 3, an n-type AlaGa1-aP is used, and for a clad layer 7, a p-type AlaGa1-aP (where 0<=a<=1) is used. In confinement layers 4, 6, used is an AlcGa1-cP)m/AldGa1-dP)n superlattice having a plurality of periods (where 0<=c<=1, 0<=d<=1, and m, n are integers). In an active layer 5, used is an AlxGayIn1-x-yP distorted quantum well or an AlpGaqIn1-p-qP)k/AlxGayIn1-x-yP)h distorted superlattice (where 0<=x<=1, 0<=y<=1, 0<=x+y<=1, 0<=p<=1, 0<=q<=1, and k, h are integers). Thereby, a double heterostructure necessary for a semiconductor laser device can be obtained, and a laser beam having a short wavelength (600nm or less) is made obtainable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device using an AlGaP-based material having a large band gap as a cladding layer.

[0002]

2. Description of the Related Art FIG. 8 is a diagram showing an outline of the structure of a semiconductor laser device. In FIG. 8, 10 is an electrode (positive electrode),
Reference numeral 11 is a p-type cladding layer, 12 is an active layer, 13 is an n-type cladding layer, 14 is an electrode (negative electrode), and L is a direction perpendicular to the bonding surface. The basic structure of the semiconductor laser device is a pn junction. When a voltage is applied to the electrodes, holes are supplied from the p-type clad layer 11 to the active layer 12, and the n-type clad layer 13 to the active layer 12. The electrons are supplied and they recombine to emit laser light.

However, typical energy band structures suitable for emitting laser light, such as a small amount of current to be injected for emitting laser light, are a double hetero structure and a separate confinement structure. There is a heterostructure (Seperate Confinement Heterostructure, hereinafter referred to as "SCH structure").

FIG. 9 is a diagram showing a double hetero structure. The reference numerals correspond to those in FIG. 8, E is electron energy, E _B is the conduction band lower end energy level, E _T is the valence band upper end energy level, and Eg ₁ and Eg ₂ are band gaps. In this example, the same material is used for the cladding layers 11 and 13. Therefore, the conduction band lower end energy level E _B and the valence band upper end energy level E _T in the cladding layers 11 and 13 have the same energy level, and the band gap also has the same Eg ₁ .

In the active layer 12, the conduction band lower end energy level E _B is lower than that of the cladding layers 11 and 13, and the valence band upper end energy level E _T is higher than that of the cladding layers 11 and 13 (hence, Bandgap Eg ₂ <Bandgap Eg ₁ ) Material is selected. Its thickness is 0.1-
It is set to about 0.2 μm. When the electrons e confined in the conduction band of the active layer 12 due to the injection of a current fall into the valence band of the active layer 12 (recombine with holes) as indicated by an arrow in the figure, energy is emitted to emit light. Emit.

The active layer 12 having a double hetero structure functions as a "carrier confinement layer" for confining carriers such as electrons and holes, and does not leak generated light to the cladding layer side (that is, while confining it in the active layer 12). ) It plays a role as an "optical confinement layer" of guiding to the outside.

FIG. 10 is a diagram showing another typical structure, the SCH structure. In this semiconductor laser device, a confinement layer is provided on both sides of the active layer. Reference numerals correspond to those in FIG. 9, 15 and 16 are confinement layers, and Eg ₃ is a band gap. Lower energy level E _{B of} conduction band and upper energy level E of valence band
_{In the} confinement layers 15 and 16, the material is selected so that _T takes an intermediate value between the cladding layers 11 and 13 and the active layer 12. With such a value, the band gap Eg ₁ > the band gap Eg ₃ > the band gap Eg
It becomes ₂ .

In such an SCH structure, the active layer 12 plays a role of a carrier confinement layer, and the confinement layers 15 and 16 play a role of an optical confinement layer. The light generated when the electrons e trapped in the active layer 12 fall into the valence band is trapped so as not to leak to the outside (cladding layer) from the confinement layers 15 and 16 and becomes a laser beam to be guided to the outside. Get burned.

By the way, it is required to generate light having a short wavelength (light having a large energy, for example, a yellow beam) by a semiconductor laser device. In order to generate such light, the material of the active layer is used. Therefore, it is necessary to use a material having a large band gap Eg ₂ . If the bandgap Eg ₂ of the active layer is made large, the bandgap of the confinement layer or the cladding layer must be larger than that, so that these materials also need to have a large bandgap.

Therefore, it has been studied to manufacture a semiconductor laser device using an AlGaP-based material having a large band gap. For example, attempts have been made to fabricate a semiconductor laser device using AlP (aluminum-phosphorus), GaP (gallium-phosphorus) and their mixed crystals.

Since AlP and GaP are lattice-matched with each other, this point is convenient as a material for a semiconductor laser device.
However, the energy band structure of the hetero interface between GaP and AlP is such that the type II (where the conduction band lower end energy level E _B lowers, the valence band upper end energy level E _T also lowers as shown in FIG. , The type that changes in the same direction).

In order to realize a double hetero structure or an SCH structure suitable for a semiconductor laser device, the valence band upper end energy level E _T rises at the conduction band lower end energy level E _B (hetero interface), It is necessary to make a change such that it goes down when it goes up (hetero interface). However, in the case of type II, the opposite change occurs. Therefore, it has been conventionally impossible to create a double hetero structure or SCH structure using GaP or AlP.

Further, since GaP and AlP are indirect transition type semiconductors in which light is very difficult to be emitted, there is a situation in which laser oscillation cannot be obtained by current injection as in a normal semiconductor laser device. It was merely used for LED light emitting devices.

On the other hand, a semiconductor laser device using a strained superlattice for the active layer and an AlGaP-based material for the cladding layer has been proposed (Japanese Patent Laid-Open No. 63-197391). This is, for example, a strained superlattice (total thickness = 8) obtained by growing AlP and Al _0.3 In _0.7 P for 4 cycles of 10 Å each.
0Å) is used for the active layer and AlP is used for the cladding layer. In this semiconductor laser device, laser oscillation is caused by photoexcitation at room temperature to obtain light having a short wavelength of 540 nm.

[0015]

(Problem) The first problem of the semiconductor laser device of the above-mentioned proposal (Japanese Patent Laid-Open No. 63-197391) is that a large amount of power is required to perform laser oscillation by photoexcitation. The point is that the luminous efficiency is poor. The second problem is that the active layer cannot be made thick and light cannot be sufficiently confined.

(Description of Problems) First, the first problem will be described. Photoexcitation that irradiates a semiconductor laser device with strong light to cause laser oscillation consumes a large amount of power in the light source of the irradiation light, so that even if laser light is obtained, the light emission efficiency is poor.

Next, the second problem will be described. Figure 1
2 shows the energy band structure of the conventional example using a strained superlattice for the active layer. The reference numeral corresponds to that of FIG. 9, and D is the thickness of the active layer 12. Since the material used is a strained superlattice of AlP / Al _0.3 In _0.7 P, the thickness D cannot be made thick enough to act as an optical confinement layer. This is because when the strained layer has a large thickness, dislocations occur. That is, this active layer 12
Plays a role as a carrier confinement layer, but due to its insufficient thickness, does not fully serve as an optical confinement layer. Therefore, the light was not confined sufficiently.

An object of the present invention is to solve the above problems.

[0019]

In order to solve the above-mentioned problems, in the semiconductor laser device of the present invention, Al _a Ga _1-a
The cladding layer using P and (Al _c Ga _1-c P) _m / (Al _d Ga) of the type II energy band structure
A confinement layer using _1-d P) _n superlattice multiple cycles was assumed to comprise an active layer using _{Al x Ga y In 1-xy} P strained quantum well.

In addition, a cladding layer using Al _a Ga _1-a P and (Al _c G G of the type II energy band structure)
a _1-c P) _m / (Al _d Ga _1-d P) _n superlattice a confinement layer using a plurality of periods and (Al _p Ga _q I
n _1-pq P) _k / (Al _x Gay _y In _1-xy P) _h active layer using a strained superlattice.

Further, a p-type clad layer using Al _a Ga _1-a P and an n-type clad layer using Al _b Ga _1-b P having an AlP mixed crystal ratio higher than that of the n-type clad layer (provided that
a <b), type II energy band structure (Al _c
Ga _1-c P) _m / (Al _d Ga _1-d P) _n Confinement layer using a plurality of superlattice periods and Al _x Ga _y I
and an active layer using an n _1-xy P strained quantum well.

Further, a p-type clad layer using Al _a Ga _1-a P and an n-type clad layer using Al _b Ga _1-b P having a higher AlP mixed crystal ratio than the n-type clad layer (provided that
a <b), type II energy band structure (Al _c
Ga _1-c P) _m / (Al _d Ga _1-d P) _n superlattice a confinement layer using a plurality of periods, and (Al _p Ga _q
In _1-pq P) _k / (Al _x Gay _y In _1-xy P) _h active layer using a strained superlattice.

However, in any case, 0 ≦ a ≦ 1,
0 ≦ b ≦ 1,0 ≦ c ≦ 1,0 ≦ d ≦ 1,0 ≦ p ≦ 1,0
≤q≤1,0≤x≤1,0≤y≤1,0≤x + y≤1, and m, n, k, and h are natural numbers.

[0024]

[Work] (Al _c Ga _1-c P) _m / (Al _d Ga
_{The 1-d} P) _n superlattice has a type II energy band structure. However, when a plurality of periods are formed, the conduction band lower end energy level is (Al _c G 2
a _1-c P) _m conduction band bottom energy level and (Al _d
It is a value between Ga _{1 -d} P) _n and the lower energy level of the conduction band.

On the other hand, (Al _c Ga _1-c P) _m / (Al _d
The upper valence band energy level of a Ga _{1 -d} P) _n superlattice formed in a plurality of cycles is (Al _c Ga _{1 -c} P) _m valence band upper end energy level and (Al _d Ga _{1 -d} P) _n
The value is between the upper valence band energy level of and.

Therefore, (Al _c Ga _1-c P) _m / (A
If a plurality of l _d Ga _1-d P) _n superlattices are formed in the confinement layer and Al _a Ga _1-a P having _a larger bandgap is used in the cladding layer,
A double heterostructure is obtained which is convenient for semiconductor laser devices. These have a large band gap among the materials used for the semiconductor laser device. Therefore, when an SCH structure is formed by further sandwiching the active layer, a material having a large band gap (eg,
_{Al x Ga y In 1-xy} P strained quantum well) can be used, it is possible to obtain a laser beam of short wavelength (600 nm or less).

Al _a G used as a cladding layer
If the mixed crystal ratio of a _1-a P (depending on a) is not made the same and the mixed crystal ratio of the n-type cladding layer is made larger than that of the p-type cladding layer (the value of a is made large), The energy barrier that dams the injected carriers becomes high, and it becomes possible to effectively prevent the overflow of carriers.

Further, since the SCH structure can be formed by providing the confinement layers on both sides of the active layer composed of the strained layer, light can be sufficiently confined.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of a semiconductor laser device according to the first embodiment. Figure 1
In the figure, 1 is a substrate, 2 is a buffer layer, 3 and 7 are cladding layers, 4 and 6 are confinement layers, 5 is an active layer, and 8
Is a cap layer.

In this embodiment, AlGaP having a large band gap is used as a material for the semiconductor laser device.
An n-type Al _a Ga is used for the clad layer 3 although a base material is used.
_1-a P is used, and p-type Al _a Ga _1-a P is used for the cladding layer 7.
Is used (however, 0 ≦ a ≦ 1). The confinement layers 4 and 6 have a plurality of periods of (Al _c Ga _{1 -c} P) _m / (A
l _d Ga _1-d P) _n superlattice (where 0 ≦ c ≦ 1, 0 ≦ d
≤1, m, n are natural numbers). Then, in the active layer 5, Al _x Ga _y In _1-xy P strained quantum well or (Al _p Ga _q In _1-pq P) _k / (Al _x Gay _y In) is formed.
_1-xy P) _h strained superlattice is used (where 0 ≦ x ≦ 1,
0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1, 0 ≦ p ≦ 1, 0 ≦ q ≦
1, k and h are natural numbers).

First, (Al _c Ga _1-c P) _m / (Al _d Ga _1-d P) _n used for the confinement layers 4 and 6 is used.
The superlattice will be described. FIG. 4 shows one cycle of (Al _c
It is a diagram illustrating a _{Ga 1-c P) m /} (Al d Ga 1-d P) n superlattice. Reference numeral 21 is (Al _c Ga _{1 -c} P) _m , 22 is (Al _d Ga _{1 -d} P) _n , and 20 is a superlattice consisting of 21, 22 for one period.

(Al _c Ga _1-c P) _m 21 is Al _c G
a _1-c P consisting of m atomic layers, (Al _d G
a _1-d P) _n 22 is composed of n atomic layers of Al _d Ga _1-d P. Composed of these two (Al _c
It has recently been found that the energy band structure of the Ga _1-c P) _m / (Al _d Ga _1-d P) _n superlattice 20 is of type II as shown in FIG.

FIG. 3 shows (Al _c Ga _{1 -c} P) _m / (Al
FIG. 3 is an energy band structure diagram when a plurality of _d Ga _1-d P) _n superlattices are formed. Reference numerals correspond to those in FIGS. 4 and 9, 23 is an arrow, Eg ₄ is a band gap, S ₁ ,
S ₂ is a subband energy level. Since the energy band structure is type II, the conduction band bottom energy level E _B and the valence band top energy level E _T both repeat high and low values corresponding to the superlattice formation period,
Quantum well can be created. In FIG. 3, it is assumed that c <d,
The value of (Al _c Ga _1-c P) _m 21 is higher. On the other hand, if d> c, (Al _d Ga _{1 -d} P) _n 22 has a higher value.

(Al _c Ga _1-c P) _m / (Al _d Ga
_When the thickness of the _1-d P) _n superlattice is reduced and the thickness of the quantum well layer is reduced, carriers (electrons, holes) in the quantum well layer behave quantumly (quantum size effect). .. That is, a quantum level is formed in the quantum well layer, and the carriers are present at an energy level higher than that level. The subband energy level S _{1 in} FIG. 3 indicates the lowest level of the quantum levels in the quantum well layer for electrons. The portion where the energy level E _{B of the} bottom of the conduction band is high ((Al _c Ga _{1 -c} P) _m 21 in this example)
Since the portion () is thin, electrons can move as shown by arrow 23 due to the tunnel effect. Therefore, in effect,
The subband energy level S ₁ becomes the conduction band lower end energy level.

The same applies to the quantum well layer for holes. Subband energy level S in FIG.
₂ indicates the lowest level among the quantum levels in the quantum well layer. In effect, this is the upper valence band energy level. Therefore, the band gap in this superlattice is the difference E between the subband energy levels S ₁ and S _2.
It becomes g ₄ . The values of S ₁ and S ₂ are (Al _c Ga _{1 -c} P)
It can be changed by appropriately changing the values of c, d, m and n of the _m / (Al _d Ga _{1 -d} P) _n superlattice.

Therefore, the subband energy level S
_{1 is set} to be lower than the conduction band lower end energy level E _{B of} Al _a Ga _{1 -a} P used for the clad layer in FIG. 1, and the subband energy level S ₂ is set to Al _a Ga _{1 -a}
It can be made higher than the valence band upper end energy level E _{T of} P. As a result, as described below,
It is possible to design an energy band structure that is convenient for lasing.

FIG. 5 shows that (Al _c Ga _{1 -c} P) _m / (Al
with _d Ga _1-d P) _n superlattice is a diagram for explaining that may produce a double heterostructure. E in Fig. 5 (a)
_B is the conduction band minimum energy level of the material used for the cladding layer, E _T is a valence band maximum energy level of the same material. For such E _B and E _T , c, d, m, n
By adjusting the value of (Al _c Ga _{1 -c} P) _m /
The subband energy level S ₁ of the (Al _d Ga _{1 -d} P) _n superlattice is lower than E _B , and the subband energy level S
_2, it can be higher than E _T. W ₁ and W ₂ are
This is the energy level difference in this case.

So adjusted (Al _c Ga _1-c P)
_{If the m} / (Al _d Ga _{1 -d} P) _n superlattice is sandwiched by cladding layers, the energy band structure becomes a double hetero structure as shown in FIG. However, since this superlattice is an indirect transition type material rather than a direct transition type, laser oscillation cannot be obtained. Therefore, in order to make a device for laser oscillation, it is necessary to sandwich a direct transition type layer in the center to form an active layer. That is, that is, the first embodiment. The energy band structure is the SCH structure as described below.

FIG. 2 shows the energy band structure of the first embodiment. The reference numerals correspond to those in FIGS. 1, 3 and 10, and W ₁ is the conduction band bottom energy level E _B in the cladding layers 3 and 7 and the conduction band bottom energy level E in the confinement layers 4 and 6. Energy level difference from _B ,
W ₂ is an energy level difference between the valence band maximum energy level E _T in the valence band upper energy level E _T and confinement layers 4 and 6 in the cladding layers 3 and 7.

On the confinement layers 4 and 6, (Al _c
Ga _1-c P) _m / (Al _d Ga _1-d P) _n superlattice is used, and by adjusting the values of c, d, m, and n, the energy level between the cladding layers 3 and 7 is Add the difference W ₁ , W ₂ . Then, as the material of the active layer _{5, Al x Ga y In 1} -xy P strained quantum well or having a band gap Eg ₄ smaller than the band gap of the confinement layers _{4,6 (Al p Ga q In 1} -pq P) _k / (Al _x G
a _y In _1-xy P) _h strained superlattice is used.

Next, a specific example of manufacturing the semiconductor laser device as described above will be described. Solid raw materials Al, G
A laser structure layer is produced by the following procedure by a gas source molecular beam epitaxy method using a, In and PH ₃ as a gas raw material. Si is doped on the n-type GaP substrate 1 to grow an n-type GaP buffer layer 2 of about 1000 Å to improve the crystallinity. On top of that, Si-doped n-type Al _0.5 Ga _0.5 P (Al _a Ga _{1 -a} P, where a =
Clad layer 3 having a thickness of 1.
Grow to 0 μm. (AlP) ₅ / (GaP) ₅ superlattice ((Al _c Ga _1-c P) _m / (Al _d Ga _1-d P)
_n superlattice with c = 1, d = 0, m = n = 5) is grown to a thickness of 0.1 μm to form one confinement layer 4. A Ga _0.65 In _0.35 P strained quantum well layer (Al _x Ga _y In _1-xy P strained quantum well layer, where x = 0 and y = 0.65) was used.
Å The layer is grown to form the active layer 5. On top of that, (Al
P) ₅ / (GaP) ₅ superlattice ((Al _c Ga _{1 -c} P) _m
/ (Al _d Ga _{1 -d} P) _n superlattice, c = 1, d = 0,
(when m = n = 5) is grown to a thickness of 0.1 μm to form the other confinement layer 6.
Be-doped p-type Al _0.5 Ga _0.5 P (Al _a Ga
_1-a P, where a = 0.5), thickness 1.
The clad layer 7 is grown to a thickness of 0 μm. Finally, in order to make ohmic contact with the electrodes, Be-doped GaAs is grown to a thickness of 0.1 μm to form the cap layer 8.

(Second Embodiment) FIG. 6 is a schematic sectional view of a semiconductor laser device according to the second embodiment. The reference numerals correspond to those in FIG. The difference from the first embodiment is that the n-type cladding layer 3 and the p-type cladding layer 7 are
This is the point that the mixed crystal ratio of the AlP layer was increased for the n-type. That is, in the first embodiment, all are Al _a Ga _{1 -a} P, but in the second embodiment, the p-type cladding layer 3 is made of Al.
_a Ga _1-a P, and the n-type cladding layer 7 is Al _b Ga
_1-b P and a <b (where 0 ≦ a ≦ 1, 0 ≦ b
≦ 1).

FIG. 7 is an energy band structure diagram of the second embodiment. Reference numerals correspond to those in FIG. 2 and are W ₃ to W.
₆ is an energy level difference, and 26 is a hole. Since the relationship of the coefficients that determine the mixed crystal ratio of the clad layers 3 and 7 is a <b, in which the coefficient b of the n-type is larger, the conduction band in the n-type clad layer 3 of the larger coefficient is larger. The values of the lower end energy level E _B and the valence band upper end energy level E _T are higher than those of the p-type cladding layer 7.

[0044] Thus, the conduction band minimum energy level E _B of the cladding layers 7,3, the conduction band minimum energy level E _B (which is in confinement layers 4 and 6, the sub-band energy described in FIG. 3 If the energy level difference with the level S ₁ ) is W ₃ and W ₄ , respectively, then W ₃ > W _{4 as} shown in FIG.

When a voltage is applied to the semiconductor laser device, electrons e, which are carriers in the conduction band, are injected from the n-type cladding layer 3 into the confinement layer 4 as indicated by arrow 24, and eventually become a carrier confinement layer. It is confined in the active layer 5. At this time, the energy level difference W _{3 at} the hetero interface between the confinement layer 6 and the p-type clad layer 7 is such that the electrons e flow into the p-type clad layer 7 as indicated by the arrow 25 ( Overflow) acts as an energy barrier. Therefore, in the second embodiment in which the energy barrier (W ₃ ) is large, the overflow of the injected electrons e is prevented.

Meanwhile, the valence band maximum energy level E _T in the cladding layer 7,3, valence band maximum energy level E _T (which is in confinement layers 4 and 6, the sub-described in FIG. 3 The energy level difference between the band energy level S ₂ and the band energy level S ₂ is W ₅ and W ₆ , respectively.
As above, W ₆ > W ₅ . Therefore, the increased energy level difference W ₆ acts as an energy barrier that prevents the holes 26 injected from the p-type cladding layer 7 from overflowing.

As described above, in the second embodiment, the overflow of injected carriers is prevented, and the number of carriers confined in the active layer 5 is increased.

In the present invention, the active layer 5 is made of Al _x Ga _y.
In _1-xy P strained quantum well or (Al _p Ga _q In
_1-pq P) _k / (Al _x Gay _y In _1-xy P) _h strained superlattices are used, but these strained layers are subject to compressive stress in the direction parallel to the interface with the adjacent layers. , The effective mass of “heavy holes” decreases, and the density of states decreases. That is, the number of electrons is relatively larger than that of holes. Therefore, "inversion distribution" in which the number of electrons in the conduction band is larger than the number of holes in the valence band is likely to occur, and the threshold current becomes low. This contributes to facilitating laser oscillation.

Next, a specific example of manufacturing the semiconductor laser device as described above will be described. Solid raw materials Al, G
A laser structure layer is produced by the following procedure by a gas source molecular beam epitaxy method using a, In, Si, Be and PH ₃ and AsH ₃ which are gas raw materials. An n-type GaP buffer layer 2 is formed by doping Si on the n-type GaP substrate 1.
Is grown to about 1000Å to improve the crystallinity. On top of that, n-type Al _0.8 Ga _0.2 P (A
The clad layer 3 of _a Ga _1-a P (where a = 0.8) is grown to a thickness of 1.0 μm. (Al
P) ₅ / (GaP) ₅ superlattice ((Al _c Ga _{1 -c} P) _m
/ (Al _d Ga _{1 -d} P) _n superlattice, c = 1, d = 0,
(when m = n = 5) is grown to a thickness of 0.1 μm to form one confinement layer 4. G
a _0.65 In _0.35 P strained quantum well layer (Al _x Ga _y In
_{A 1-xy} P strained quantum well layer (where x = 0 and y = 0.65) is grown as 50 Å to form the active layer 5.
On top of that, (AlP) ₅ / (GaP) ₅ superlattice ((AlP
_c Ga _1-c P) _m / (Al _d Ga _1-d P) _n superlattice,
(when c = 1, d = 0, m = n = 5) is grown to a thickness of 0.1 μm to form the other confinement layer 6. Be-doped p-type Al _0.5 Ga
_0.5 P (Al _a Ga _1-a P, where a = 0.5) is grown to a thickness of 1.0 μm to form the cladding layer 7. Finally, in order to make ohmic contact with the electrodes, Be-doped GaAs is grown to a thickness of 0.1 μm to form the cap layer 8.

[0050]

As described above, according to the present invention, (A
l _c Ga _1-c P) _m / (Al _d Ga _1-d P) _n superlattice is used as a confinement layer, and Al _a Ga _1-a P
Is used for the clad layer, a double heterostructure required for a semiconductor laser device is obtained. Since these are materials having a large band gap, the band gap of the active layer can be increased accordingly. Therefore, a laser beam having a short wavelength (600 nm or less) can be obtained.

Al _a G used as a cladding layer
If the mixed crystal ratio of a _1-a P (depending on a) is not made the same and the value of a in the n-type cladding layer is made larger than that of the p-type cladding layer, the energy barrier that blocks the injected carriers And the carrier overflow can be prevented.

Even if a strained superlattice is used for the active layer, since the SCH structure has the confinement layers on both sides thereof, light can be sufficiently confined.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a semiconductor laser device according to a first embodiment.

FIG. 2 is an energy band structure diagram of the first embodiment.

FIG. 3 (Al _c Ga _1-c P) _m / (Al _d Ga _1-d
P) Energy band structure diagram when multiple periods of _n superlattice are formed

FIG. 4 shows one cycle of (Al _c Ga _{1 -c} P) _m / (Al
Diagram for explaining _d Ga _1-d P) _n superlattice

FIG. 5: (Al _c Ga _1-c P) _m / (Al _d Ga _1-d
P) A diagram illustrating that a double heterostructure can be fabricated using an _n superlattice

FIG. 6 is a schematic sectional view of a semiconductor laser device according to a second embodiment.

FIG. 7 is an energy band structure diagram of the second embodiment.

FIG. 8 is a diagram showing a schematic structure of a semiconductor laser device.

FIG. 9 is a diagram showing an energy band structure of a double hetero structure.

FIG. 10 is a diagram showing an energy band structure of an SCH structure.

FIG. 11 is an energy band structure diagram near the junction between GaP and AlP.

FIG. 12 is an energy band structure diagram of a conventional example using a superlattice in the active layer.

[Explanation of symbols]

1 ... Substrate, 2 ... Buffer layer, 3, 7 ... Clad layer, 4,
6 ... Confinement layer, 5 ... Active layer, 8 ... Cap layer, 10 ... Electrode, 11, 13 ... Clad layer, 12 ... Active layer, 14 ... Electrode, 15, 16 ... Confinement layer,
20 ... 1 period superlattice, 21 ... (Al _c Ga
_1-c P) _m , 22 ... (Al _d Ga _1-d P) _n , 23 to 2
5 ... arrows 26 ... hole, D ... thickness, E ... electron energy, E _B ... bottom of the conduction band energy level, Eg ₁ ~Eg ₄
... band gap, E _T ... valence band upper end energy level, L ... junction surface vertical direction, S ₁ , S ₂ ... subband energy level, W _{1 to} W ₄ ... energy level difference

Claims (4)

[Claims] 1. A clad layer using Al _a Ga _{1 -a} P and (Al _c Ga of a type II energy band structure).
_1-c P) _m / (Al _d Ga _1-d P) _n Confinement layer using a plurality of periods and an Al _x Ga _y In layer.
_1-xy P strained quantum well active layer and 0 ≦
a ≦ 1,0 ≦ c ≦ 1,0 ≦ d ≦ 1,0 ≦ x ≦ 1,0 ≦ y
A semiconductor laser device characterized in that ≦ 1,0 ≦ x + y ≦ 1, and m and n are natural numbers. 2. A clad layer using Al _a Ga _1-a P and (Al _c Ga of a type II energy band structure).
_1-c P) _m / (Al _d Ga _1-d P) _n superconducting confinement layer using a plurality of cycles, and (Al _p Ga _q In
_{1-pq P) k / (} Al x Ga y In 1-xy P) comprising an active using _h strained superlattice layer, 0 ≦ a ≦ 1,0 ≦ c ≦
1,0 ≦ d ≦ 1,0 ≦ p ≦ 1,0 ≦ q ≦ 1,0 ≦ x ≦
1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, and m, n, k, h
Is a semiconductor laser device characterized by being a natural number. 3. A p-type clad layer using Al _a Ga _{1 -a} P and an Al having _a higher AlP mixed crystal ratio than the n-type clad layer.
An n-type cladding layer using _b Ga _1-b P and (Al _c Ga _1-c P) _m / (A of the type II energy band structure
a confinement layer using _{l d Ga 1-d P)} n superlattice multiple cycles, and an active layer using _{Al x Ga y In 1-xy} P strained quantum well comprises, 0 ≦ a ≦ 1,0 ≦ b ≦
1,0≤c≤1,0≤d≤1,0≤x≤1,0≤y≤
A semiconductor laser device characterized in that 1,0 ≦ x + y ≦ 1, a <b, and m and n are natural numbers. 4. A p-type clad layer using Al _a Ga _{1 -a} P and Al having _a higher AlP mixed crystal ratio than the n-type clad layer.
An n-type cladding layer using _b Ga _1-b P and (Al _c Ga _1-c P) _m / (A of the type II energy band structure
_{l d Ga 1-d P)} n and confinement layer using a superlattice multiple _{cycles, (Al p Ga q In 1} -pq P) k /
_{(Al x Ga y In 1-} xy P) comprises a _h strained superlattice active layer using, 0 ≦ a ≦ 1,0 ≦ b ≦ 1,0 ≦ c ≦
1,0 ≦ d ≦ 1,0 ≦ p ≦ 1,0 ≦ q ≦ 1,0 ≦ x ≦
1,0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1, a <b, and m,
A semiconductor laser device in which n, k, and h are natural numbers.