JPH08191170A - Semiconductor laser - Google Patents

Abstract

PURPOSE: To provide a semiconductor laser of long life wherein heat generation is restrained by making an operation voltage low, and electric power consumption is little. CONSTITUTION: A semiconductor laser is provided with at least a P-type Zna Mg1-a SbSe1-b clad layer 14 where 0<=a, b<=1, and an N-type clad layer 16 which clad layers are formed on a P-type semiconductor substrate 12, an active layer 15 positioned between the clad layers, and a P-type and an N-type electrodes 11, 17. A P-type semiconductor buffer layer 13 wherein lattice matching the substrate is obtained, and the energy level at the top of the valence band is positioned between that of the substrate and that of the clad layer is formed between the P-type semiconductor substrate and the P-type clad layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly to a semiconductor laser emitting blue to blue-green light.

[0002]

2. Description of the Related Art As a semiconductor laser that emits blue to blue-green light, for example, a ZnSe-based semiconductor laser has been conventionally known. Such a semiconductor laser is schematically shown in a sectional view in FIG. The semiconductor laser shown in FIG. 22 is a publication (for example, "Continuous-wave operation of 489.9").
nm blue laser diode at room temperature "N.Naka
yama et. al. Electrics Letters 29 (199
3) pp. 2194-2195) as a substrate.

In FIG. 22, 221 is an In electrode for an n-type GaAs substrate, 222 is an n-type GaAs substrate, 223 is an n-type ZnSSe buffer layer, 224 is an n-type ZnMgSSe cladding layer, 225 is an n-type ZnSSe optical guide layer, 226. Is an undoped ZnCdSe SQW (single quantum well) active layer,
227 is an undoped ZnSSe optical guide layer, 228 is a p-type ZnMgSSe cladding layer, 229 is a p-type ZnSSe layer, 2
Reference numeral 30 is a p-type ZnTe / p-type ZnSe MQW (multiple quantum active well layer), 231 is a p-type ZnTe contact layer, 232 is an insulating layer for current confinement, and 233 is a Pd / Pt / Au p-type electrode.

[0004]

In the semiconductor laser using the n-type semiconductor as a substrate as described above, electrons are supplied from the entire surface of the substrate, while holes are supplied through a current confinement layer having a width of about 10 μm. To be done. However, ZnMgSSe, Zn
In the case of crystals such as SSe and ZnSe, it is p
The p-type ZnMgSSe, ZnSSe, ZnSe layer and p-type crystal have a high resistivity and the carrier concentration cannot be increased.
Since there are some potential barriers between the mold electrode and the mold electrode, there are problems that the operating voltage of the semiconductor laser device increases and heat is generated. Further, there is a problem that the element is deteriorated due to the crystal defect in the active layer, which makes stable operation for a long time difficult.

Further, in the semiconductor laser, the Schottky barrier layer generated at the interface when forming the n-type electrode in the n-type cladding layer causes the contact resistance Rc when electrons are injected from the metal into the semiconductor. It is generally known that the value of the contact resistance Rc decreases as the Schottky barrier height φb decreases and the depletion layer width W on the semiconductor side decreases. Therefore, when manufacturing a semiconductor laser device, in order to reduce the contact resistance Rc, a contact layer having a high concentration of n-type doping is provided between the n-type electrode metal and the n-type cladding layer to reduce the depletion layer width. Reduced,
Also, the barrier height is divided.

As such a contact layer, a ZnSe layer doped with a high concentration of Cl having a carrier concentration of 10 ¹⁹ cm ^-3 to 10 ²⁰ cm ^-3 is usually used. It is not preferable in consideration of the influence of damage on the contact layer, and it is necessary to form the contact layer without using halogen. However, when a dopant other than halogen is used, it is difficult to dope ZnSe with a carrier concentration of 10 ¹⁹ cm ^-3 or more, and there is a problem that contact resistance increases.

The present invention has been made in order to solve the various problems described above, and suppresses heat generation by lowering the operating voltage of the laser, and also provides a laser with low power consumption and long life. The challenge is to achieve it. It is also an object of the present invention to provide a semiconductor laser having a low contact resistance Rc.

[0008]

According to the first aspect of the present invention, the present invention provides a semiconductor laser having a structure using a p-type semiconductor as a substrate, wherein a valence band peak is provided between the p-type substrate and the p-type ZnMgSSe cladding layer. Based on providing a buffer layer whose energy level is between that of the p-type substrate and that of the p-type ZnMgSSe layer.

That is, according to the first aspect, the present invention provides p
At least p-type Zn _a Mg formed on a p-type semiconductor substrate
_1-a S _b Se _1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ 1) clad layer and n-type clad layer, semiconductor laser having p-type and n-type electrodes located between clad layers A p-type semiconductor buffer layer between the p-type semiconductor substrate and the p-type cladding layer in lattice matching with the substrate, and the energy level at the top of the valence band is located between that of the substrate and that of the cladding layer There is provided a semiconductor laser characterized by being provided.

As described above, the p-type substrate and the p-type ZnMgSSe
By providing a p-type semiconductor buffer layer with the layer,
The valence band offset existing between the p-type substrate and the p-type ZnMgSSe layer is divided to relax the potential barrier, thereby lowering the operating voltage of the laser device.

In the above first aspect, in one preferred embodiment, the p-type semiconductor substrate is a p-type GaAs substrate,
The buffer layer is p-type ZnS _1-xy Se _x Te _y (0 <x <1,0
≦ y <1, 0 <x + y ≦ 1). By using such a buffer layer, the valence band offset existing between the p-type substrate and the p-type ZnMgSSe cladding layer is divided and the potential barrier is relaxed while preventing the occurrence of defects due to lattice misalignment. As a result, the operating voltage of the laser element becomes low.

In the above-mentioned preferred embodiment, the composition of the buffer layer may be such that x decreases and y increases from the substrate side toward the cladding layer side while lattice matching with the substrate. Such an increase in x and a decrease in y may be continuous, stepwise, or a combination thereof.

By changing x and y in this way, the energy level at the top of the valence band is brought closer to the level of the p-type ZnMgSSe cladding layer from the level of the substrate continuously or stepwise. Thus, the valence band offset existing between the p-type substrate and the p-type ZnMgSSe layer is divided, the potential barrier is relaxed, and the operating voltage of the laser element is lowered.

In another preferred embodiment of the first aspect,
The buffer layer has p-type ZnTe / p-type ZnS _z Te whose average lattice constant in the interface direction is equal to that of the substrate.
It is composed of a _1-z (0 ≦ z ≦ 1) strained superlattice. By providing the strained superlattice in this way, the p-type substrate and the p-type ZnMgS
The valence band offset existing with the Se clad layer is divided, the potential barrier is relaxed, and the operating voltage of the laser element is lowered. Furthermore, an effect of preventing the propagation of dislocations from the substrate to the cladding layer is expected.

In still another preferred embodiment of the first aspect, the buffer layer is p-type In _w instead of p-type ZnSSeTe.
Ga _1-w N (0 ≦ w ≦ 1). From the band gap value and Harrison's common anion rule, it is obvious that the energy level at the top of the valence band of InGaN is on the low energy side compared to that of GaAs.
Therefore, in this case as well as in the case of ZnSSeTe, p
The valence band offset existing between the die substrate and the p-type ZnMgSSe layer is divided, the potential barrier is relaxed, and the operating voltage of the laser element is lowered.

In a second aspect, the present invention provides a semiconductor laser using p-type GaAs as a substrate, which has a highly n-type heavily doped contact layer between an n-type electrode and an n-type cladding layer. That is, the present invention provides at least p-type Zn _a Mg _1-a S _b Se formed on a p-type GaAs substrate.
_1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ 1) In a semiconductor laser having a cladding layer and an n-type cladding layer, an active layer between the cladding layers, and n-type and p-type electrodes, Provided is a semiconductor laser comprising a contact layer, such as a GaAs contact layer, which is heavily n-type doped with a mold electrode.

By using a high-concentration n-type doped layer as the n-type contact layer, the potential barrier generated in the conduction band is relaxed, and the laser element can be driven at a low voltage.
For example, GaAs is capable of high-concentration n-type doping on the order of 10 ¹⁹ cm ⁻³ , and by adopting this as an n-type contact layer, the potential barrier generated in the conduction band is relaxed,
It is possible to drive the laser element at a low voltage.

As described above, ZnSe doped with high concentration of Cl is considered as the n-type contact layer, but this contact layer is not always satisfactory. Such a problem is solved by providing, as a contact layer, a GaAs layer which is heavily doped with n-type under the electrode metal, for example, between the electrode metal and the clad layer, instead of the n-type ZnSe layer. As a result, the contact resistance is reduced, and a low-voltage operation semiconductor laser can be realized without using halogen.

In another aspect of the second aspect, an AlGaAs contact layer which is heavily n-type doped is provided in place of the GaAs contact layer. When the AlGaAs contact layer is provided, the contact resistance can be further reduced as compared with the GaAs contact layer.

In a third aspect, the present invention is based on the use of a metal having a work function smaller than In as an electrode for an n-type layer in a semiconductor laser having a p-type semiconductor substrate. That is, in the third aspect, the present invention relates to at least p-type Zn _a Mg _1-a formed on a p-type semiconductor substrate.
S _b Se _1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ 1) clad layer and n-type clad layer, active layer between clad layers, and p
A semiconductor laser having an n-type electrode and an n-type electrode, wherein the n-type electrode on the n-type cladding layer is formed of a metal or an alloy having a work function smaller than In. In which has been usually used so far as an electrode on the n-type cladding layer or the n-type contact layer
By using a metal or an alloy having a work function smaller than that of, a perfect ohmic contact can be obtained and a low voltage operation can be performed.

The metals having a work function smaller than In as described above include Y, La, Ce, Pr, Nd, Pm, Sm and E.
Examples thereof include u, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Hf, and these metals have an advantage that they can be easily formed as an electrode by a method such as vapor deposition. Further, an alloy composed of at least two of these metals can also be used as a metal having a work function smaller than In. By using such a metal (including alloy), low voltage operation can be performed by a simple method.

In a preferred mode, the invention of the second aspect is combined with the semiconductor laser of the third aspect. That is, in the semiconductor laser, the n-type contact layer is provided between the n-type electrode made of a metal (or alloy) having a work function smaller than In and the n-type cladding layer based on the second aspect.
By providing the contact layer in this way, it is possible to obtain the effect of reducing the contact resistance.

In a fourth aspect, the present invention relates to a hetero interface, for example, between a clad layer and an active layer, between a light guide layer and an active layer when a light guide layer is present, and a clad layer. It is based on providing a strained superlattice layer for preventing the propagation of dislocations in at least one position between the optical guide layer and the optical guide layer. That is, according to the fourth aspect, the present invention prevents the propagation of dislocations in a semiconductor laser formed on a compound semiconductor substrate and having at least p-type and n-type cladding layers, an active layer, and n-type and p-type electrodes. There is provided a semiconductor laser having at least one strained superlattice layer at a hetero interface portion for protection.

By providing the strained superlattice layer at the hetero interface, dislocations propagating from the substrate or dislocations generated at the hetero interface are prevented from propagating to the active layer, and the defect density in the active layer is reduced. The semiconductor laser can be stably operated for a long time.

In a preferred embodiment of the fourth aspect, in the semiconductor laser, the p-type cladding layer is p-type Zn _a Mg _1-a S _b Se.
_1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ 1), and the n-type cladding layer is Zn _c Mg _1-c S _d Se _1-d (0 ≦ c ≦ 1, 1 ≦ d
≦ 1), and at least 3 selected from Zn, Mg, S, Se and Te at least at one location between the p-type cladding layer and the active layer and between the n-type cladding layer and the active layer. A strained superlattice layer composed of a compound semiconductor composed of seeds is provided.

In the laser structure using ZnMgSSe as the cladding layer, Zn, between the active layer and the cladding layer,
By introducing a strained superlattice layer composed of a compound semiconductor composed of at least three kinds selected from Mg, S, Se and Te, it is particularly difficult to reduce the defect density II
It is possible to reduce the defect density in the active layer of a semiconductor laser composed of a -VI semiconductor, and to realize a semiconductor laser that operates stably for a long time.

In another preferred embodiment of the fourth aspect,
The semiconductor laser includes a p-type Zn _f Mg _1-f S _g Se _1-g (0 ≦ f ≦ 1, which is located between the active layer and the p-type cladding layer and between the active layer and the n-type cladding layer, respectively. 0 ≦ g ≦ 1) guide layer and n-type Zn _h Mg _1-h S _j Se _1-j (0 ≦ h ≦ 1, 0
≦ j ≦ 1) further having a guide layer (a <f, b <
g, c <h, d <j), between p-type cladding layer and p-type guide layer, between n-type cladding layer and n-type guide layer, between p-type guide layer and active layer and n-type A strained superlattice layer composed of a compound semiconductor composed of at least three kinds selected from Zn, Mg, S, Se and Te is provided at at least one position between the guide layer and the active layer.

ZnMgS as clad layer and guide layer
In a laser structure using Se, by introducing a strained superlattice layer composed of Zn, Mg, S, and Se into at least one location between the active layer and the cladding layer and between the cladding layer and the guide layer. In particular, it becomes possible to reduce the defect density in the active layer of a semiconductor laser composed of a II-VI group semiconductor in which it is difficult to reduce the defect density, and it is possible to realize a semiconductor laser that operates stably for a long time.

In a particularly preferred embodiment of the fourth aspect, GaAs is used as the compound semiconductor substrate material. By using GaAs which is easily available as a compound semiconductor substrate and has a lattice constant close to that of ZnSe, it is possible to supply a semiconductor laser at a low price. Further, as crystals forming the strained superlattice, ZnTe / ZnSTe, ZnSe / ZnSSe, ZnS
Examples include e / ZnMgSSe and the like.

The present invention described in the above first to fourth aspects is
Where possible, any of the inventions may be used in combination with at least one other invention. For example, the invention of the first gist of providing a buffer layer,
It may be combined with at least one of the invention of the second aspect of providing a contact layer, the invention of the third aspect of providing an n-type electrode made of a specific metal, and the invention of the fourth aspect of providing a strained superlattice layer. The same applies to the inventions of other gist other than the invention of the first gist.

Unless otherwise specified, substrate material, buffer layer material, clad layer material, guide layer material,
Any material known to those skilled in the art may be used as the active layer material and the electrode material. Further, the method of forming the layer of such a material can be carried out by a method obvious to those skilled in the art, such as the MBE method. However, in a particularly preferred embodiment of the invention, GaAs is used as the substrate, ZnMgSSe is used as the cladding layer, and ZnCdSe / ZnSe is used as the active layer. Further, the specific composition of various layers, the thickness of layers, and the like disclosed by the present invention are appropriately determined by those skilled in the art based on the concept of the present invention according to the intended performance of the semiconductor laser. You can choose.

Further, in the semiconductor laser of the present invention, if necessary, the substrate, the active layer, the guide layer, the clad layer, and the buffer layer may be layers which are obvious to those skilled in the art as additional layers if necessary. You may have. For example, the substrate is
A mixed crystal buffer layer may be provided thereon (that is, on the side opposite to the electrodes).

[0033]

In the first aspect of the present invention, the p-type substrate and the p-type substrate
By providing the p-type semiconductor buffer layer between the p-type ZnMgSSe layer and the p-type ZnMgSSe layer, the valence band offset existing between the p-type substrate and the p-type ZnMgSSe layer is divided, and the potential barrier is relaxed. According to the second aspect of the present invention, the potential barrier generated in the conduction band is relaxed by using a highly n-doped layer as the n-type contact layer. In the third aspect of the present invention, by using a metal or an alloy having a work function smaller than that of In, which has been conventionally used, as an electrode on the n-type cladding layer or the n-type contact layer, A good ohmic contact can be obtained.

In a fourth aspect of the present invention, a strained superlattice layer composed of a compound semiconductor composed of at least three kinds selected from Zn, Mg, S, Se and Te is provided between the active layer and the cladding layer. It becomes possible to reduce the defect density in the active layer of the semiconductor laser composed of the II-VI group semiconductor in which it is difficult to reduce the defect density. Hereinafter, the first to fourth aspects of the present invention will be described in more detail with reference to examples of preferred embodiments.

[0035]

【Example】

Example 1 FIG. 1 is a sectional view schematically showing a semiconductor laser according to an example of the first gist of the present invention. In FIG. 1, 11 is p
Ohmic electrode for the mold substrate, 12 for p-type GaAs substrate, 13 for p-type ZnSSeTe buffer layer, 14 for p-type Zn
MgSSe cladding layer, 15 is an active layer composed of ZnCdSe / ZnSe single quantum well, 16 is an n-type ZnMgSSe cladding layer, and 17 is an electrode for the n-type layer. That is, as can be easily understood, in this embodiment, the p-type buffer layer 13 is provided between the p-type substrate 12 and the p-type cladding layer 14.

In order to explain this example in more detail, FIG. 2 shows the valence band energy levels (hereinafter referred to as Ev) and conduction bands of ZnSe, ZnS, ZnTe and GaAs based on the vacuum level. Energy level (hereinafter referred to as Ec)
Indicates. The Ev of ZnMgSSe used as the cladding layer is
Since it depends on the composition ratio of S and Se (the effect of Mg can be ignored), it exists at any position shown by the dotted line between Ev of ZnSe and Ev of ZnS. Therefore, p-type G
When a heterojunction is formed between the aAs layer and the p-type ZnMgSSe layer, a large band offset corresponding to the difference between the Ev of GaAs and the Ev of ZnMgSSe occurs on the valence band side, which causes the substrate to shift to the cladding layer. It acts as a barrier layer when injecting holes, which increases the operating voltage of the semiconductor laser.

Therefore, in the present invention, a p-type GaAs substrate and a p-type GaAs substrate are used.
By providing a ZnSSeTe layer having a high concentration of p-type doping with the ZnMgSSe layer, a reduction in operating voltage is realized. ZnTe has a carrier concentration of 10
^It is possible to perform high-concentration p-type doping on the order of ²⁰ cm ⁻³ , and therefore it is considered that the ZnSSeTe layer can be similarly highly-concentrated p-type doping. In addition, II-V shown in FIG.
As is clear from the relationship between the lattice constant and band gap of the I / III-V group semiconductor, it is possible to obtain lattice matching with GaAs by adding S and Se to ZnTe to form a mixed crystal. Moreover, as is clear from FIG.
It is possible to get closer to the GaAs side than that of MgSSe.

Therefore, Zn is p-type-doped at such a high concentration that the lattice matching with GaAs is achieved and the position of Ev exists between the Ev of ZnMgSSe and the Ev of GaAs.
It is possible to form the SSeTe crystal as a buffer layer, and by providing this as a buffer layer on the substrate, the barrier is divided and the operating voltage can be lowered. FIG. 4 shows the relationship between Ec and Ev in the portion from the p-type substrate to the p-type cladding layer in the case where such a ZnSSeTe buffer layer is provided. As is clear from FIG. 4, the band offset of the valence band between the p-type ZnMgSSe cladding layer 41 and the p-type GaAs substrate 43 is divided by the p-type ZnSSeTe buffer layer 42, and it can be seen that the operating voltage can be reduced.

In this embodiment, p-type and n-type ZnMgSSe are used.
The electrode stripe type laser structure composed of the clad layers (14, 16) and the CdZnSe / ZnSe single quantum well active layer (15) has been exemplified. As the active layer, CdZnSe / Zn is used.
A structure using Se multiple quantum wells, a structure in which an optical guide layer is provided between the cladding layer and the active layer, a lateral current and a light confining structure in the upper n-type layer or the upper n-type layer and the active layer are provided. The same effect can be expected with the structure.

Example 2 In Example 1 above, ZnSS was provided between the p-type GaAs substrate (12, 43) and the p-type ZnMgSSe cladding layer (14, 41).
Although only one eTe buffer layer (13, 42) was provided, in Example 2, the single buffer layer (13, 4) of Example 1 was used.
Instead of 2), three ZnS _1-xy Se _x Te _y buffer layers are provided between the p-type GaAs substrate and the p-type ZnMgSSe cladding layer (the other layers are substantially the same as in Example 1).
A schematic view of the energy band of such a semiconductor laser is shown in FIG.

In FIG. 5, the composition ratios x and y of the p-type ZnS _1-xy Se _x Te _y buffer layer are sequentially x 1, y 1, and x from the p-type substrate 55 side toward the p-type clad layer 51 side.
If 2, y2, x3, y3, then x1>x2> x3, y
P-type ZnSSeTe satisfying the relation of 1 <y2 <y3
Buffer layer third layer 54, p-type ZnSSeTe buffer layer second layer 53 and p-type ZnSSeTe buffer layer first layer 52
Have. That is, the composition of the buffer layer changes stepwise. In this structure, the valence band offset generated between the p-type ZnMgSSe cladding layer 51 and the p-type GaAs substrate 55 is divided into four steps to reduce the offset generated at each hetero interface, resulting in a reduction in the operating voltage. A reduction is realized.

Example 3 In Example 1 or 2, the p-type GaAs substrate and the p-type ZnMgS were used.
ZnS _1-xy Se _x Te _y buffer composition ratio of layer x provided between the Se cladding layer, y is is a semiconductor laser which has a constant or stepwise, in this embodiment, in place of such a buffer layer ZnS _1-xy Se _x Te _y buffer layer composition ratio x,
y is continuously changed (substantially the same as in Example 1 for other layers).

FIG. 6 shows a schematic view of the energy band between the p-type cladding layer 61 and the p-type GaAs substrate 63 of the semiconductor laser of this embodiment. By continuously decreasing the composition ratio x of the p-type ZnSSeTe buffer layer 62 from the substrate 63 side toward the cladding layer 61 side and continuously increasing the composition ratio y, lattice matching with the GaAs substrate is achieved, Ev can be continuously approached from that of the GaAs substrate 63 to that of the ZnMgSSe clad layer 61, and the operating voltage can be lowered.

Example 4 The semiconductor laser of this example is the p-type ZnS of Examples 1-3.
Instead of the SeTe buffer layer, as shown in FIG. 7, a p-type ZnSTe / p-type ZnTe strained superlattice buffer layer 72 is provided between the p-type GaAs substrate 73 and the p-type ZnMgSSe cladding layer 71.
(Substantially the same as in Examples 1 to 3 for other layers). The lattice constants a (ZnS) and a of ZnS and ZnTe
(ZnTe) are 5.41Å and 6.10Å, respectively, and therefore, the lattice constant a (GaAs) of GaAs (= 5.65).
Å) is located between a (ZnS) and a (ZnTe). Therefore, the combination of ZnS _x Te _1-x and ZnTe having a composition ratio x smaller than the lattice constant of GaAs makes the average lattice constant in the interface direction equal to the lattice constant of GaAs p-type ZnSTe / p-type ZnTe. It is possible to fabricate strained superlattices.

At this time, the ZnSTe layer is a barrier layer of a strained superlattice,
ZnTe acts as a well layer, and when the thicknesses thereof are L _b and L _w , respectively, (L _b × a (ZnSxTe _1-x ) + L _w × a (ZnTe)) / (L _b +
L _w ) = a (GaAs) is satisfied, and by selecting the values of x, L _b and L _w at which misfit dislocations are not formed, p-type doping is performed at a high concentration and the average lattice constant in the interface direction is selected. Is G
It is possible to form a strained superlattice buffer layer that is equal to that of aAs.

For example, when x = 0.8, that is, when ZnS _0.8 Te _0.2 is selected as the barrier layer, the lattice constant of ZnS _0.8 Te _0.2 becomes 5.55Å, and L _b : L for lattice matching with the GaAs substrate. _It is necessary that _w = 9: 2. Therefore,
For example, L _w = 0.3 nm (1 atomic layer), L _b = 1.4 nm
(5 atomic layers), it is substantially lattice-matched with GaAs,
In addition, a strained superlattice free from misfit dislocations can be formed. By adopting such a strained superlattice buffer layer 72, in addition to the effect of reducing the valence band offset described in Examples 1 to 3, dislocations originally present on the surface of the GaAs substrate and II- on the GaAs substrate are present. The effect of preventing the propagation of defects such as dislocations generated when forming the group VI semiconductor layer into the group II-VI semiconductor can be expected.

Example 5 Example 5 shown in FIG. 8 is a p-type GaAs substrate 82 and a p-type Z.
This is a semiconductor laser in which a p-type InGaN buffer layer 83 is provided between the nMgSSe cladding layer 84. FIG. 8 also shows a p-type ohmic electrode 81, an active layer 85, an n-type cladding layer 86 and an n-type electrode 87. In this structure, as in the case where the p-type ZnSSeTe buffer layer is provided, the p-type ZnMgSSe cladding layer 84 and the p-type GaAs are formed.
By dividing the valence band offset generated with the substrate 82, the operating voltage of the semiconductor laser is reduced.

Embodiment 6 FIG. 9 is a sectional view schematically showing a semiconductor laser according to an embodiment of the second gist of the present invention. In FIG. 9, 91 is p
Ohmic electrode for the mold substrate, 92 p-type GaAs substrate, 93 p-type ZnSSeTe buffer layer, 94 p-type Zn
MgSSe cladding layer, 95 is an active layer composed of ZnCdSe / ZnSe single quantum well, 96 is an n-type ZnMgSSe cladding layer, 97 is an n-type GaAs contact layer, and 98 is an In electrode.

This embodiment is characterized in that the contact layer 97 is a GaAs layer which is heavily n-type doped. FIG. 10 shows a case where an In electrode is directly formed on the ZnMgSSe clad layer (on the left side of FIG. 10) and ZnMgSS.
The schematic diagram which compares the energy band at the time of providing an n-type GaAs contact layer between an e clad layer and an In electrode (right side of FIG. 10) is shown. When the In electrode is directly formed on the ZnMgSSe cladding layer, as is clear from the schematic diagram on the left side of FIG. 10, there is a band barrier Δφ due to the difference in Fermi energy between ZnMgSSe and In, and Zn
The difference between the Fermi energies of MgSSe and In is approximately 1
There is a depletion layer having a width of W that is proportional to the / 2 power and is inversely proportional to the 1/2 power of the carrier concentration Nd of the ZnMgSSe layer.

However, when a GaAs layer heavily doped with n-type is formed as a contact layer between the cladding layer and the electrode, as can be seen from the schematic diagram on the right side of FIG. 10, the Fermi quasi of n-type GaAs can be understood. Since the position is located between that of ZnMgSSe and that of In, Δφ is divided, and since G is highly doped, G
The width of the depletion layer formed on the In electrode side of aAs is also small. Therefore, the barrier when electrons are injected from the In electrode into the ZnMgSSe layer by the tunnel is relaxed, and ZnMg
As compared with the case where the In electrode is directly formed on SSe, the current-voltage characteristics having excellent ohmic characteristics can be obtained.

Example 7 Although n-type GaAs was used as the contact layer in the above-mentioned Example 6, as shown in FIG. 11, in this example, the n-type AlGaAs layer 117 and the n-type cladding layer 116 were used as the contact layers.
And the In electrode 118.
The value of conduction band offset between GaAs and ZnMgSSe is ZnM.
Although it depends on the composition ratio of the gSSe layer, an n-type AlGaAs layer is provided as a contact layer as in this embodiment, and the Al composition ratio is appropriately selected according to the ZnMgSSe composition ratio to efficiently divide the barrier layer. You can do it. FIG.
1, the ohmic electrode 111 with respect to the p-type substrate,
p-type GaAs substrate 112, p-type ZnSSeTe buffer layer 1
13, p-type ZnMgSSe cladding layer 114 and ZnCd
An active layer 115 consisting of a Se / ZnSe single quantum well is also shown.

Example 8 FIG. 12 is a sectional view schematically showing a semiconductor laser of Example 8 as a specific example of the second gist of the present invention, in which 121 is an ohmic electrode for a p-type substrate and 122 is p. Type GaAs
Substrate, 123 p-type ZnSSeTe buffer layer, 124 p-type ZnMgSSe clad layer, 125 ZnCdSe / Zn
Active layer composed of Se multiple quantum wells, 126 is n-type ZnMg
SSe clad layer, 127 is an n-type GaAs contact layer,
128 is an AuGeNi electrode.

As is known, the AuGeNi electrode is an n-type GaAs.
A good ohmic characteristic with a small contact resistance can be obtained by heat treatment at about 450 ° C. after the above formation. In this embodiment, the structure shown in FIG. 12 is subjected to a heat treatment after formation to reduce the contact resistance between GaAs and AuGeNi, and Ga in the GaAs layer diffuses to the ZnMgSSe side to act as an n-type dopant, and ZnMgSSe. Carrier concentration near the GaAs interface of the layer increases and ZnMgSSe
The width of the depletion layer spreading in the layer is reduced, and ZnMgSSe and GaAs are reduced.
The contact resistance at the interface is reduced.

Example 9 FIG. 13 shows a semiconductor laser of Example 9 as still another specific example of the present invention. In this embodiment shown in FIG. 13, the GaAs layer 97 in a portion other than directly under the stripe electrode 98 in the structure shown in FIG. 9 is removed by etching or the like, and the portion is covered with an insulating film. That is, the semiconductor laser of this embodiment has a p-type electrode 131 and a p-type GaAs substrate 13.
2, p-type ZnSSeTe buffer layer 133, p-type ZnMgS
Se clad layer 134, active layer 135 consisting of ZnCdSe / ZnSe single quantum well, n-type clad layer 136,
It has an n-type GaAs contact layer 137, an n-type ohmic electrode 138 and an insulating film 139.

In the semiconductor laser of the sixth embodiment, when a current is injected from the stripe electrode 98, the current may spread laterally in the GaAs layer because the resistance of the GaAs contact layer is low. Since the GaAs layer 137 is left only just under the electrode portion 138, the spread of current is prevented.

Embodiment 10 FIG. 14 is a sectional view schematically showing a semiconductor laser of Embodiment 10 as a specific example of the third gist of the present invention.
41 is an ohmic electrode for a p-type substrate, 142 is a p-type GaAs substrate, 143 is a p-type ZnSSeTe buffer layer, 1
44 is a p-type ZnMgSSe cladding layer and 145 is ZnCdSe.
/ ZnSe Active layer consisting of single quantum well, 146 is n-type Z
The nMgSSe cladding layer and 147 are Pd electrodes. That is,
In this embodiment, n is a metal whose work function is smaller than In.
It is used as a mold electrode.

Conventionally, In is mainly used as an electrode for the n-type ZnMgSSe layer, but since the value of the work function of In is larger than the Fermi energy of ZnMgSSe, a Schottky barrier layer can be formed. Therefore, in this embodiment, the barrier height and the depletion layer width formed in the ZnMgSSe layer are reduced by using Pd having a work function smaller than In as an electrode. The band diagram (Fermi energy E _F ) of ZnMgSSe / Pd changes depending on the composition of Mg, but becomes as shown in FIG. In FIG.
The left side shows the case where the Mg composition is large, and the right side shows the case where the Mg composition is small. It can be seen that the barrier height and the depletion layer width are reduced, as is clear from a comparison of the drawings on the left side of FIG. 15 and FIG.

Example 11 FIG. 16 is a sectional view schematically showing a semiconductor laser of Example 11 as a specific example of the fourth gist of the present invention.
161 is an ohmic electrode for the p-type substrate, 162 is p
Type GaAs substrate, 163 is a p-type ZnMgSSe cladding layer,
164 is a p-type ZnTe / ZnSTe strained superlattice layer, 165 is Z
nCdSe / ZnSe single quantum well layer, 166 is n-type ZnSe
/ ZnSSe strained superlattice layer, 167 is an n-type ZnMgSSe cladding layer, and 168 is an electrode for the n-type layer. That is, in this embodiment, the active layer 164 and the cladding layers 163 and 1
Strained superlattice layers 164 and 166 are provided at the hetero interface with 67.

For each strained superlattice layer, the composition and the film thickness of the well layer and the barrier layer are selected so that the average lattice constant in the interface direction matches GaAs. For example, ZnTe / Zn
Regarding STe, as in the case of the fifth embodiment, L _b and L
You may choose _w . Regarding ZnSe / ZnSSe, for example, if ZnS _0.12 Se _0.88 is selected as the barrier layer and L _w = L _b = 5 nm, the strained superlattice is substantially lattice-matched with GaAs and does not contain misfit dislocations. Layers can be formed.

In this structure, the substrate 162 or p
The dislocations propagating from the clad layer 163 to the active layer 165 are strained by the p-type ZnTe / ZnSTe strained superlattice layer 164, and the dislocations propagating from the n-type clad layer 167 to the active layer 165 side are n-type ZnSe / ZnSSe strained. The superlattice layer 166 prevents propagation into the respective active layers and reduces the defect density in the active layer 165 which causes deterioration of the semiconductor laser device.

Example 12 FIG. 17 is a sectional view showing a semiconductor laser of Example 12 as a specific example of the fourth gist of the present invention. In FIG. 17, 1 is an electrode for the p-type layer, 2 is a p-type GaAs substrate,
3 is a p-type ZnMgSSe cladding layer, 4 is a p-type ZnSe / Zn
SSe strained superlattice layer, 5 ZnCdSe / ZnSe single quantum well layer, 6 n-type ZnSe / ZnSSe strained superlattice layer, 7 n-type Z
nMgSSe cladding layer, 8 is an electrode for the n-type layer. That is, the point that ZnSe / ZnSSe is used as the p-type superlattice layer is different from the case of FIG. For each strained superlattice layer, the composition and the film thickness of the well layer and the barrier layer are selected so that the average lattice constant in the interface direction matches GaAs.
Also in this embodiment, the same effect as that of the eleventh embodiment can be obtained.

Example 13 FIG. 18 is a sectional view showing a semiconductor laser of Example 13 as a specific example of the fourth gist of the present invention. In FIG. 18, 181 is an electrode for the p-type layer, and 182 is a p-type Ga.
As substrate, 183 is p-type ZnMgSSe clad layer, 184
Is a p-type ZnSe / ZnMgSSe strained superlattice layer, 185 is ZnC
dSe / ZnSe single quantum well layer, 186 is n-type ZnSe / Z
The nMgSSe strained superlattice layer, 187 is an n-type ZnMgSSe cladding layer, and 188 is an electrode for the n-type layer. That is, the point that ZnSe / ZnMgSSe is used as the p-type strained superlattice layer is different from the case of FIG. For each strained superlattice layer, the composition and the film thickness of the well layer and the barrier layer are selected so that the average lattice constant in the interface direction matches GaAs. Also in this embodiment, the same effect as that of the eleventh embodiment can be obtained.

Example 14 FIG. 19 is a sectional view schematically showing a semiconductor laser of Example 14 as another specific example of the fourth gist of the present invention. In FIG. 19, 191 is an electrode for the p-type layer, 1
92 is a p-type GaAs substrate, 193 is a p-type ZnMgSSe cladding layer, 194 is a p-type ZnSSe guide layer, and 195 is Zn.
Te / ZnSTe strained superlattice layer, 196 is ZnCdSe / ZnSe
Single quantum well layer, 197 is n-type ZnSe / ZnSSe strained superlattice layer, 198 is n-type ZnSSe guide layer, and 199 is n-type Z
nMgSSe clad layer, 200 is an electrode for the n-type layer. That is, a guide layer is added to the semiconductor laser shown in FIG.

For each strained superlattice layer, the composition and the thickness of the well layer and the barrier layer are selected so that the average lattice constant in the interface direction matches GaAs. In this structure, dislocations propagating from the substrate 192, the p-type cladding layer 193, or the p-type guide layer 194 to the active layer 196 are converted into p-type Zn.
In the Te / ZnSTe strained superlattice layer 195, 19 from the n-type cladding layer 199 or the n-type guide layer 198 to the active layer side.
6 The dislocations returning to 6 are prevented from propagating in the active layer in the n-type ZnSe / ZnSSe strained superlattice layer 197, respectively, and the defect density in the active layer which causes deterioration of the device is reduced.

Fifteenth Embodiment FIG. 20 is a sectional view schematically showing a semiconductor laser of a fifteenth embodiment as a specific example of the fourth gist of the present invention. In FIG. 20, 201 is an electrode for the p-type layer, 202 is a p-type GaAs substrate, 203 is a p-type ZnMgSSe cladding layer, 204 is a p-type ZnSSe guide layer, and 205 is ZnSe.
/ ZnS strained superlattice layer, 206 is a ZnCdSe / ZnSe single quantum well layer, 207 is an n-type ZnSe / ZnSSe strained superlattice layer,
208 is an n-type ZnSSe guide layer, 209 is n-type ZnMg
SSe cladding layer, 210 is an electrode for the n-type layer. That is, the semiconductor laser shown in FIG. 17 is provided with a guide. For each strained superlattice layer, the composition and the film thickness of the well layer and the barrier layer are selected so that the average lattice constant in the interface direction matches GaAs. Also in this embodiment, the same effect as that of the fourteenth embodiment can be obtained.

Embodiment 16 FIG. 21 is a sectional view schematically showing a semiconductor laser of Embodiment 16 as a specific example of the fourth gist of the present invention. In FIG. 21, 211 is an electrode for the p-type layer, 212 is a p-type GaAs substrate, 213 is a p-type ZnMgSSe cladding layer, 214 is a p-type ZnSSe guide layer, and 215 is ZnSe /
ZnMgSSe strained superlattice layer, 216 ZnCdSe / ZnSe single quantum well layer, 217 n-type ZnSe / ZnMgSSe strained superlattice layer, 218 n-type ZnSSe guide layer, 219 n-type ZnMgSSe cladding layer, 220 n-type layer Is an electrode for. That is, the semiconductor laser shown in FIG. 18 is provided with a guide. For each strained superlattice layer, the composition and the film thickness of the well layer and the barrier layer are selected so that the average lattice constant in the interface direction matches GaAs. Also in this embodiment, the same effect as that of the fourteenth embodiment can be obtained.

[0067]

According to the first aspect of the present invention, since the valence band offset existing between the p-type substrate and the p-type ZnMgSSe layer is divided and the potential barrier is relaxed, the operating voltage of the semiconductor laser device is reduced. Will be lower. According to the second aspect of the present invention, the potential barrier generated in the conduction band is relaxed, so that the semiconductor laser device can be driven at a low voltage. According to the third aspect of the present invention, since perfect ohmic contact is obtained, the semiconductor laser can be operated at a low voltage. According to the fourth aspect of the present invention, it is possible to reduce the defect density in the active layer of a semiconductor laser composed of a II-VI group semiconductor in which it is particularly difficult to reduce the defect density. A laser can be realized.

[Brief description of drawings]

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

FIG. 2 ZnTe, ZnSe, Zn based on vacuum level
The schematic diagram which shows the energy level of the valence band and conduction band of S and GaAs.

FIG. 3 is a schematic diagram showing a relationship between a lattice constant and a band gap of a II-VI / III-V group semiconductor.

FIG. 4 is a band schematic diagram of the semiconductor laser of Example 1.

5 is a band schematic diagram of the semiconductor laser of Example 2. FIG.

FIG. 6 is a band schematic diagram of the semiconductor laser of Example 3;

FIG. 7 is a band schematic diagram of the semiconductor laser of Example 4.

FIG. 8 is a schematic cross-sectional view of a semiconductor laser of Example 5.

FIG. 9 is a schematic cross-sectional view of a semiconductor laser of Example 6.

FIG. 10 is a schematic band diagram showing the influence of the presence or absence of a GaAs contact layer.

FIG. 11 is a schematic cross-sectional view of a semiconductor laser of Example 7.

FIG. 12 is a schematic cross-sectional view of a semiconductor laser of Example 8.

FIG. 13 is a schematic cross-sectional view of a semiconductor laser of Example 9.

FIG. 14 is a schematic sectional view of a semiconductor laser according to an example 10.

FIG. 15 is a schematic band diagram of n-type ZnMgSSe and Pd.

FIG. 16 is a schematic cross-sectional view of a semiconductor laser of Example 11.

FIG. 17 is a schematic cross-sectional view of the semiconductor laser of Example 12.

FIG. 18 is a schematic cross-sectional view of a semiconductor laser of Example 13.

FIG. 19 is a schematic sectional view of a semiconductor laser of Example 14.

FIG. 20 is a schematic cross-sectional view of a semiconductor laser of Example 15.

FIG. 21 is a schematic cross-sectional view of a semiconductor laser of Example 16.

FIG. 22 is a schematic cross-sectional view of the structure of a conventional semiconductor laser.

[Explanation of symbols]

Ohmic electrode for 11 p-type substrate, 12 p-type G
aAs substrate, 13 p-type ZnSSeTe buffer layer, 14
p-type ZnMgSSe cladding layer, 15 ZnCdSe / ZnSe
Active layer consisting of single quantum well, 16 n-type ZnMgSSe
Clad layer, electrode for 17 n-type layer, 41 p-type Z
nMgSSe clad layer, 42 p-type ZnSSeTe buffer layer, 43 p-type GaAs substrate, 51 p-type ZnMgSSe clad layer, 52 p-type ZnSSeTe buffer layer first layer,
53 p-type ZnSSeTe buffer layer second layer, 54 p-type ZnSSeTe buffer layer third layer, 55 p-type GaAs substrate, 61 p-type ZnMgSSe clad layer, 62 p-type Zn
SSeTe buffer layer, 63 p-type GaAs substrate, 71 p
Type ZnMgSSe clad layer, 72p type ZnSTe / ZnT
e strained superlattice buffer layer, 73 p-type GaAs substrate, 81
Ohmic electrode for p-type substrate, 82 p-type GaAs substrate, 83 p-type InGaN buffer layer, 84 p-type ZnMg
SSe clad layer, active layer consisting of 85 ZnCdSe / ZnSe single quantum well, 86 n-type ZnMgSSe clad layer, electrode for 87 n-type layer, ohmic electrode for 91 p-type substrate, 92 p-type GaAs substrate, 94 p-type ZnMgSSe clad layer Layer, 95 ZnCdSe / ZnSe single quantum well active layer, 96 n-type ZnMgSSe cladding layer, 97 n-type GaAs contact layer, 98 In electrode, 111 ohmic electrode for p-type substrate, 112
p-type GaAs substrate, 114 p-type ZnMgSSe cladding layer, 115 ZnCdSe / ZnSe single quantum well active layer, 116 n-type ZnMgSSe cladding layer, 117
n-type AlGaAs contact layer, 118 In electrode, 12
Ohmic electrode for 1 p-type substrate, 122 p-type G
aAs substrate, 124 p-type ZnMgSSe cladding layer, 12
5 Active layer composed of ZnCdSe / ZnSe single quantum well,
126 n-type ZnMgSSe clad layer, 127n-type GaAs
s contact layer, 128 AuGeNi electrode, 131 electrode for p-type substrate, 132 p-type GaAs substrate, 134
p-type ZnMgSSe cladding layer, 135 ZnCdSe / Zn
Active layer consisting of Se single quantum well, 136 n-type ZnMg
SSe clad layer, 137 n-type GaAs contact layer,
138 Ohmic electrode for n-type GaAs, 141
Ohmic electrode for p-type substrate, 142 p-type GaAs
Substrate, 144 p-type ZnMgSSe cladding layer, 145
ZnCdSe / ZnSe single quantum well active layer, 14
6 n-type ZnMgSSe cladding layer, 147 Pd electrode, 1
61 Ohmic electrode for p-type substrate, 162 p-type GaAs substrate, 163 p-type ZnMgSSe cladding layer, 16
4 p-type ZnTe / ZnSTe strained superlattice layer, 165 ZnCd
Se / ZnSe single quantum well active layer, 166 n
Type ZnSe / ZnSSe strained superlattice layer, 167 n-type ZnMgS
Se cladding layer, electrode for 168 n-type layer, 171
Ohmic electrode for p-type substrate, 172 p-type Ga
As substrate, 173 p-type ZnMgSSe cladding layer, 174
p-type ZnSe / ZnSSe strained superlattice layer, 175 ZnCdS
Active layer composed of e / ZnSe single quantum well, 176 n-type ZnSe / ZnSSe strained superlattice layer, 177 n-type ZnMgSS
e clad layer, electrode for 178n type layer, 181 p
Ohmic electrode for mold substrate, 182 p-type GaAs substrate, 183 p-type ZnMgSSe clad layer, 184 p
Type ZnSe / ZnMgSSe strained superlattice layer, 185 ZnCdSe
/ ZnSe Active layer consisting of single quantum well, 186 n-type Z
nSe / ZnMgSSe strained superlattice layer, 187 n-type ZnMgS
Se cladding layer, electrode for 188 n-type layer, 191
Ohmic electrode for p-type substrate, 192 p-type Ga
As substrate, 193 p-type ZnMgSSe cladding layer, 194
p-type ZnSSe optical guide layer, 195 p-type ZnTe / ZnS
Te strained superlattice layer, 196 ZnCdSe / ZnSe single quantum well active layer, 197 n-type ZnSe / ZnSSe strained superlattice layer, 198 n-type ZnSSe optical guide layer, 199 n-type ZnMgSSe cladding layer, electrode for 200 n-type layer , 201 ohmic electrode for p-type substrate, 202
p-type GaAs substrate, 203 p-type ZnMgSSe cladding layer, 204 p-type ZnSSe optical guide layer, 205 p-type Zn
Se / ZnSSe strained superlattice layer, 206ZnCdSe / ZnSe single quantum well active layer, 207 n-type ZnSe / Zn
SSe strained superlattice layer, 208 n-type ZnSSe optical guide layer,
209 n-type ZnMgSSe clad layer, 210 electrode for n-type layer, 211 ohmic electrode for p-type substrate, 212 p-type GaAs substrate, 213 p-type ZnMgSS
e clad layer, 214p type ZnSSe optical guide layer, 215
p-type ZnSe / ZnMgSSe strained superlattice layer, 216 ZnC
Active layer consisting of dSe / ZnSe single quantum well, 217 n
Type ZnSe / ZnMgSSe strained superlattice layer, 218 n-type ZnS
Se optical guide layer, 219 n-type ZnMgSSe cladding layer,
220 Electrode for n-type layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Otsuka Inventor Kenichi Otsuka 8-1, 1-1 Tsukaguchihonmachi, Amagasaki City, Hyogo Sanryo Electric Co., Ltd. Semiconductor Research Laboratories (72) Toshiro Isu Inoue, Tsukaguchimotocho, Amagasaki City, Hyogo Prefecture 1-1-1 Sanryo Electric Co., Ltd. Semiconductor Basic Research Laboratory

Claims (14)

[Claims] 1. At least p-type Zn _a Mg _1-a S _b Se _1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ formed on a p-type semiconductor substrate.
1) In a semiconductor laser having a clad layer, an n-type clad layer, an active layer located between the clad layers, and p-type and n-type electrodes, a lattice match is made between the p-type semiconductor substrate and the p-type clad layer. And a p-type semiconductor buffer layer whose energy level at the top of the valence band is located between that of the substrate and that of the cladding layer. 2. The p-type semiconductor substrate is a p-type GaAs substrate, and the buffer layer is p-type ZnS _1-xy Se _x Te _y (0 <x <
The semiconductor laser according to claim 1, wherein the semiconductor laser is constituted by 1, 0 ≤ y <1, 0 <x + y ≤ 1). 3. The semiconductor laser according to claim 2, wherein the composition of the buffer layer is lattice-matched with the substrate, and x decreases and y increases from the substrate side toward the cladding layer side. 4. The p-type semiconductor substrate is a p-type GaAs substrate, and the buffer layer has a p-type ZnTe / p-type ZnS _z whose average lattice constant in the interface direction is equal to the lattice constant of the substrate.
2. The semiconductor laser according to claim 1, wherein the semiconductor laser comprises a Te _{1 -z} (0≤z≤1) strained superlattice. 5. The p-type semiconductor substrate is a p-type GaAs substrate, and the buffer layer is made of p-type In _w Ga _1-w N (0 ≦ w ≦ 1). Semiconductor laser. 6. At least p-type Zn _a Mg _1-a S _b Se _1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ formed on a p-type GaAs substrate.
1) In a semiconductor laser having a cladding layer and an n-type cladding layer, an active layer between the cladding layers, and n-type and p-type electrodes, high-concentration n-type doping is performed between the n-type cladding layer and the n-type electrode. A semiconductor laser having a GaAs contact layer as described above. 7. The semiconductor laser according to claim 6, wherein an AlGaAs contact layer which is heavily n-type doped is provided in place of the GaAs contact layer. 8. At least p-type Zn _a Mg _1-a S _b Se _1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ formed on a p-type semiconductor substrate.
1) In a semiconductor laser having a clad layer and an n-type clad layer, an active layer between the clad layers, and p-type and n-type electrodes, the n-type electrode on the n-type clad layer is made of a metal or an alloy having a work function smaller than In. A semiconductor laser characterized by being formed by. 9. The metal or alloy is Y, La, Ce, P
d, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
9. The semiconductor laser according to claim 8, wherein the semiconductor laser is selected from m, Yb, Lu and Hf and combinations thereof. 10. Between the n-type cladding layer and the n-type electrode,
Highly n-type doped GaAs or AlGaA
10. The semiconductor laser according to claim 8, wherein an s contact layer is present. 11. A p-type and n-type clad layer, an active layer, and an n layer formed on a compound semiconductor substrate.
A semiconductor laser having a p-type electrode and a p-type electrode, wherein at least one strained superlattice layer is provided at a hetero interface portion to prevent dislocation propagation. 12. The p-type cladding layer comprises p-type Zn _a Mg _1-a S _b.
Se _1-b (0 ≦ a ≦ 1, 0 ≦ b ≦ 1), and the n-type cladding layer is Zn _c Mg _1-c S _d Se _1-d (0 ≦ c ≦ 1, 0 ≦
d ≦ 1), and at least at one location between the p-type cladding layer and the active layer and between the n-type cladding layer and the active layer, at least one selected from Zn, Mg, S, Se and Te. The semiconductor laser according to claim 11, further comprising a strained superlattice layer composed of a compound semiconductor composed of three kinds. 13. A p-type Zn _f Mg _1-f S _g Se _1-g (0 ≦ f ≦ 1) located between the active layer and the p-type cladding layer and between the active layer and the n-type cladding layer, respectively. , 0 ≦ g ≦ 1) guide layer and n-type Zn _h Mg _1-h S _j Se _1-j (0 ≦ h ≦ 1, 0
≦ j ≦ 1) guide layer (a <f, b <g, c <h, d <
j), further comprising: a p-type clad layer and a p-type guide layer, an n-type clad layer and an n-type guide layer, a p-type guide layer and an active layer, and an n-type guide layer. 13. The semiconductor laser according to claim 12, further comprising a strained superlattice layer at at least one position between the active layer and the active layer. 14. The semiconductor laser according to claim 11, wherein GaAs is used as the compound semiconductor substrate.