JPH10112565A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser structure driven with low voltage, in a bluish green semiconductor laser using a ZnSe 2-6 compound semiconductor. SOLUTION: A semiconductor laser possesses an n-type ZnSSe buffer layer 3, an n-type ZnMgSSe clad layer 4, a ZnCdSe active layer 6, a p-type ZnMgSSe clad layer 8, and a p-type ZnSSe layer 9 on an n-type GaAs substrate 1. The contact resistance becomes small, and the lowering of the drive voltage can be achieved with good reproducibility, by the constitution consisting of a semiconductor where the band off set of a valence band is 0.3eV or under to the n-type ZnSSe semiconductor 9, for example, a p-type ZnCdSSe semiconductor, a p-type ZnSe/ZnTe superlattice layer, and a p-type ZnTe contact layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device such as a semiconductor laser capable of emitting light in a wavelength range from green to blue.

[0002]

2. Description of the Related Art In recent years, there has been a demand for a short-wavelength semiconductor laser in order to increase the density of an optical disc and increase the resolution of a laser printer. Research on blue and green semiconductor lasers using ZnSe-based group 2-6 compound semiconductors has been required. Development is active. For a report on the development progress of semiconductor lasers using ZnSe-based Group 2-6, see Electronics Letters 31st March
1994, Vol. 30, Paragraphs 568 to 569, a gain-guided semiconductor laser, or Electronics Lett.
ers 9th December 1993 Vol.29, paragraphs 2192 to 21
As described in Item 93, continuous oscillation at room temperature has been achieved by a ridge refractive index type semiconductor laser in which an insulating film is embedded on the side surface of the ridge.

[0003] However, Electronics Letters 14th Marc
In the room temperature operation described in h 1996 Vol. 32, paragraphs 552 to 553, failure occurs at most for about 100 hours, and one of the major causes is a large operating voltage of 11V. For the reduction of operating voltage, for example, J. Vac.Sci.Technol.B 12 (4). Jul / Aug 19
94, a pseudo-gradient layer using a p-type ZnSe / ZnTe superlattice structure described in paragraphs 2480 to 2483 has been proposed to effectively reduce the voltage. Starting from a 3 nm p-type ZnTe and a 1.7 nm thick p-type ZnSe layer, each thickness is reduced to 0.1 nm.
A pseudo mixed crystal is formed by increasing or decreasing the amount by
No. 920, Japanese Patent Publication No. Hei 8-506694).

[0004]

However, in this conventional structure, the p-type ZnTe layer in the first stage of growth is an ultra-thin film of 1 to 2 atomic layers, so that the growth rate is different from usual and the thickness control is difficult. Also, the conditions for uniform two-dimensional growth on the substrate are severe, and island-like three-dimensional growth is likely to occur. If the p-type ZnTe layer in the first stage of growth cannot be successfully grown, it becomes a voltage barrier and the voltage cannot be reduced, which is a very important technical point. Therefore, it is hard to say that the voltage can be reduced with good reproducibility when considering mass productivity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor light emitting device which reduces the operating voltage with good reproducibility and a method for manufacturing the same.

[0006]

In order to achieve the above object, according to a first aspect of the present invention, after forming an n-type ZnSe or ZnSSe semiconductor layer on an n-type GaAs semiconductor substrate,
a first cladding layer made of an n-type ZnMgSSe-based semiconductor layer lattice-matched with an aAs substrate;
e-based light guide layer, ZnCdSe quantum well layer, and second Zn
A light emitting layer having an SSe-based light guide layer, and p-type ZnM
In a semiconductor laser having a second cladding layer made of a gSSe-based semiconductor and at least a p-type ZnSSe or p-type ZnSe layer, the p-type ZnSSe or p-type Z
p-type ZnSSe or p-type ZnSe on the nSe layer
The band offset ΔEv of the valence band is 0.3 e with respect to the layer.
A p-type compound semiconductor of V or less, a p-type ZnSe / ZnTe multilayer semiconductor layer, and a p-type ZnTe contact layer are formed.

With the above configuration, p-type ZnSe or Z
A voltage barrier generated between the nSSe semiconductor layer and the p-type ZnTe contact layer is suppressed, and the present semiconductor laser can be driven at a low voltage.

Next, in the second aspect of the present invention, n-type GaAs
After forming an n-type ZnSe or ZnSSe semiconductor layer on an s semiconductor substrate, a first cladding layer composed of an n-type ZnMgSSe-based semiconductor layer lattice-matched with a GaAs substrate, and a first ZnSSe-based light guide layer And ZnCdSe
In a semiconductor laser having a light emitting layer having a quantum well layer and a second ZnSSe-based light guide layer, a second cladding layer made of a p-type ZnMgSSe-based semiconductor, and at least a p-type ZnSSe or a p-type ZnSe layer, Type Z
On top of the nSSe or p-type ZnSe layer, p-type Zn1-
αCdαS1-βSeβ (0 ≦ α, β ≦ 1) compound semiconductor, p-type ZnSe / ZnTe multilayer semiconductor layer and p-type Zn
A Te contact layer is formed.

With the above structure, p-type ZnSe or Z
A voltage barrier generated between the nSSe semiconductor layer and the p-type ZnTe contact layer is suppressed, and the present semiconductor laser can be driven at a low voltage.

Next, in the third invention of the present invention, the p-type Zn1-αCdαS1-βSeβ (0 ≦ α, β ≦
1) In the composition of the compound semiconductor, when the Cd composition is 50% or less, the S composition is 30% or less, and the layer thickness is 6 nm or less, the lattice mismatch with the GaAs substrate is small, and the p-type Z
A valence band barrier difference between the semiconductor layer and the nSe or ZnSSe semiconductor layer can be increased, which greatly contributes to lowering the voltage of the semiconductor laser.

In the fourth invention, the p-type Zn1 of the second invention is used.
-ΑCdαS1-βSeβ (0 ≦ α, β ≦ 1) A plurality of compound semiconductors are formed with a p-type ZnSe or ZnSzSe1-z semiconductor layer interposed therebetween. Further, the layer thickness is configured to be sequentially increased. Then, the valence band becomes p-type ZnSe / Z
The energy increases toward the nTe multilayer semiconductor layer, so that a so-called pseudo-gradient layer is formed, and the voltage barrier is reduced. In the present invention, even if the growth of the first p-type ZnTe layer is insufficient, a plurality of p-type Zn1-αCdαS1-βSeβ (0
.Ltoreq..alpha., .Beta..ltoreq.1) The barrier difference in the valence band can be reliably reduced in the compound semiconductor.

In a fifth aspect of the present invention, after forming an n-type ZnSe or ZnSSe semiconductor layer on an n-type GaAs semiconductor substrate, the n-type ZnSe lattice-matched with the GaAs substrate is formed.
A first cladding layer made of a MgSSe-based semiconductor layer, a light-emitting layer having a first ZnSSe-based light guide layer, a ZnCdSe quantum well layer, and a second ZnSSe-based light guide layer;
In a semiconductor laser having a second cladding layer made of a p-type ZnMgSSe-based semiconductor and at least a p-type ZnSSe or a p-type ZnSe layer, p-type Zn1-αCdαS is formed on the p-type ZnSSe or the p-type ZnSe layer.
1-βSeβ (0 ≦ α, β ≦ 1) compound semiconductor and p-type Z
An nTe contact layer is formed. The p-type Zn1-αC
A plurality of dαS1-βSeβ (0 ≦ α, β ≦ 1) compound semiconductors are formed with a p-type ZnSe or ZnSSe semiconductor layer interposed therebetween. p-type Zn1-αCdαS1-βSeβ
(0 ≦ α, β ≦ 1) The compound semiconductor layer forms a pseudo-graded layer by sequentially reducing the layer thickness, and gradually reduces the valence band barrier difference with respect to the p-type ZnTe contact layer.
An effect contributing to lowering the voltage of the semiconductor laser can be expected.

In a sixth aspect, an n-type GaAs compound semiconductor substrate comprises an n-type ZnSe or ZnSSe compound semiconductor and an n-type Zn1-xMgS1-ySey compound semiconductor lattice-matched to the GaAs substrate. Cladding layer, ZnSSe-based light guide layer and ZnCdS
a light emitting layer having an e quantum well layer and a p-type ZnMgSS
a second cladding layer made of an e-based semiconductor and p-type ZnSz
A p-type ZnSe layer having a Se1-z (0 ≦ z ≦ 0.08) semiconductor layer, and a p-type ZnTe semiconductor layer is sequentially thicker and a p-type ZnSe semiconductor layer is sequentially thinner on the p-type ZnSzSe1-z semiconductor layer. In a semiconductor light emitting device having a ZnTe multilayer semiconductor layer, a plurality of p-type ZnTe semiconductor layers having the same thickness on the p-type ZnSzSe1-z semiconductor layer side are repeatedly formed. Since the p-type ZnTe semiconductor layer on the p-type ZnSzSe1-z semiconductor layer side is an ultra-thin film, it is easy to grow three-dimensionally and has poor in-plane uniformity. As a result, the non-uniform portion is complemented, and improvement in reproducibility of low-voltage driving of the semiconductor laser can be expected.

In the seventh invention, the semiconductor laser manufactured according to the above invention can be driven at a low voltage, so that it can be applied to an optical recording device such as an optical disk which requires a low voltage drive.

In the eighth invention, the semiconductor laser manufactured according to the above invention can be driven at a low voltage, so that it can be applied to an optical recording apparatus such as an optical disk which requires a low voltage drive.

According to the ninth aspect, the semiconductor laser manufactured according to the above aspect of the present invention can be driven at a low voltage, so that the reliability and the output can be increased. Of medical equipment.

In the tenth aspect, the semiconductor laser manufactured according to the above aspect of the invention can be driven at a low voltage, so that it can be applied to an optical communication device such as an optical fiber communication which requires a low voltage drive.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the semiconductor laser according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a semiconductor multilayer film structure obtained by epitaxial growth of a semiconductor laser of the present invention. n-type GaAs wafer Bu Ffa layer 2 ^{(n = 1 × 10 18 cm} -3) was 0.5μm grown on the n-type GaAs substrate ^{1 (n = 1 × 10 18} cm -3), n -type chlorine at a growth temperature 280 ° C. Doped ZnSe or ZnS _0.06 Se buffer layer 3 (thickness 10
nm, n = 1 × 10 ¹⁸ cm ⁻³ ) and n-type chlorine-doped Zn _0.9 Mg _0.1 S _0.13 Se _0.87 clat layer 4 (n = 1 × 1 cm ⁻³ )
0 ¹⁸ cm ^-3 ), n-type ZnS _0.06 Se _0.94 light guide layer 5
(Thickness 100 nm), ZnCdSe active layer 6 (thickness 6 n
m), ZnS _0.06 Se light guide layer 7 (thickness 100 nm)
To form a light emitting region. And p-type nitrogen-doped Z
n _0.9 Mg _0.1 S _0.13 Se _0.87 ct layer 8 (p = 1 × 10
¹⁷ cm ^-3 ), p-type nitrogen-doped ZnS _0.06 Se layer 9 (p =
5 × 10 ¹⁷ cm ⁻³ ), p-type nitrogen-doped Zn _0.6 Cd _0.4 S
_{0. 06} Se _0.94 superlattice layer ^{10 (p = 1 × 10 17} cm -3, thickness 3 nm), a p-type nitrogen doped ZnSe / ZnTe superlattice pseudo gradient layer 11, and forms a p-type nitrogen doped ZnTe contact layer 12 .

P-type nitrogen-doped Zn _0.6 Cd _0.4 S _0.06 Se
_The band gap of the _0.94 superlattice layer 10 is about 2.34 eV, and the valence band offset ΔEv is about 0.1 eV with respect to the p-type nitrogen-doped ZnS _0.06 Se layer 9. p-type nitrogen doped ZnSe / Z
The structure of the nTe superlattice pseudo-gradient layer 11 is ZnS as a unit.
The sum of the thicknesses of the e-layer and the ZnTe layer is assumed to be 2 nm and the pseudo Z
An nSeTe mixed crystal was formed. The first layer is p-type ZnSe
1.6 nm, p-type ZnTe 0.4 nm, followed by p-type ZnSe 1.5 nm and p-type ZnTe 0.5 nm, thus decreasing p-type ZnSe by 0.1 nm and increasing p-type ZnTe by 0.1 nm I let it. Finally, p-type Z
nSe 0.1 nm and p-type ZnTe 1.9 nm, which are connected to the p-type ZnTe contact layer 12 (FIG. 3).

Here, a conventional p-type nitrogen-doped ZnSe /
A structure using a ZnTe superlattice pseudo-gradient layer will be described with reference to FIG. (A) shows p-type ZnSe and p-type ZnTe
P-type ZnSe is p-type ZnSe as shown in FIG.
It has a type II heterojunction structure in which both Ec and Ev are lower than Te. (B) shows a band diagram in a thermal equilibrium state, in which the valence band offset ΔEv at the heterojunction interface is about 0.5.
It is known that 7 eV exists. This offset hinders the movement of the hole, and the resistance increases when the offset amount is large. To mitigate this, p-type Z
p-type Z having a forbidden band width between nSe and p-type ZnTe
A method of inserting an nSeTe layer is used. As a method for realizing the structure, a p-type ZnSe 11b as shown in FIG.
Using a / p-type ZnTe11a superlattice, the thickness of each layer is gradually changed to form a pseudo gradient band gap. In this structure, the ZnSe layer 11b and the ZnTe layer 1 are used as units.
Assuming that the sum of the film thicknesses of 1a is constant at 2 nm, a pseudo ZnSeTe mixed crystal is formed. Specifically, p-type Z having a thickness of 0.2 nm
Starting with nTe11a and p-type ZnSe11b with a thickness of 1.8 nm, the thickness of each is increased or decreased by 0.1 nm. However, a layer having a thickness of about 0.2 to 0.4 nm has a thickness of about 1 to 2 atomic layers, and it is very difficult in practice to form the layer uniformly on the wafer surface.

In this embodiment, as shown in FIG. 3, the p-type nitrogen-doped ZnCdSSe-based superlattice layer 10 is
And the pseudo-gradient layer 11, and the film thickness is 3 nm, so that the thickness can be sufficiently controlled by molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOVPE). In contrast to the use of the pseudo-ZnSeTe mixed crystal layer at the beginning of Example 11, it is possible to form the layer with good uniformity. Valence band offset ΔEv of concern
In this embodiment, the value is about 0.1 eV, which is almost equivalent to the value of the first pseudo ZnSeTe mixed crystal layer. Although the lattice mismatch with GaAs is as large as about 1.5%, since it is a superlattice thin film, a defect-free crystal structure without lattice relaxation is obtained.

Further, since it is a quaternary mixed crystal, the effect of improving the crystal hardness and increasing the resistance to the occurrence of defects can be expected. It is needless to say that the same effect can be expected in the case of ZnCdSe ternary mixed crystal. This ZnCdS
By sandwiching Se10, p-type ZnSe / p-type ZnTe
Since the thickness of the p-type ZnTe layer at the beginning of the superlattice layer can be made relatively thick at 0.4 nm, it is possible to uniformly control the crystal growth in the plane.

The composition of the ZnCdSSe-based superlattice layer 10 will be described. In the superlattice layer 10, it is necessary to consider the magnitude of the band offset ΔEv of the valence band and the critical film thickness. The hetero barrier ΔEv that allows hole carriers to travel sufficiently in the semiconductor is preferably about 0.1 eV or less. Therefore, as a composition having a ΔEv value equivalent to the initial layer structure of the pseudo ZnSeTe mixed crystal layer, the Cd composition is 50% or less, and Good results can be obtained when the composition is 30% or less and the film thickness is 6 nm or less. The hetero barrier must be at least 0.3 eV or less. At this time, the composition was almost 60% or less for the Cd composition, 50% or less for the S composition, and the film thickness was 10n.
m or less.

In the above embodiment, the p-type ZnCdSSe
Although the single superlattice layer is formed, more effects can be expected if a plurality of layers are formed.

FIG. 6 shows a p-type ZnCdSSe-based superlattice layer 10.
Shows a band diagram of a two-layer structure. The compositions of the first layer and the second layer are the same, and are p-type nitrogen-doped Zn _0.6 Cd _0.4 S _0.06 Se _0.94
(P = 1 × 10 ¹⁷ cm ⁻³ ), but the film thickness is p-ZnS
From the e side, they are 2 nm and 3 nm, respectively. The forbidden band widths are about 2.4 eV and 2.34 eV, and the ΔEv values are about 0.07 eV and 0.1 eV, respectively. Note that two-layer p-type Zn
2 nm thick p-type ZnSe between CdSSe-based superlattice layers
A layer was formed. When a plurality of layers are formed in a stepwise manner as described above, the barrier becomes small, and the holes flow more easily. Similarly, p
It is also possible to use three or more ZnCdSSe-based superlattice layers or to gradually change the composition of the p-type ZnCdSSe-based superlattice layer to reduce ΔEv so that a hole can easily flow.

FIG. 7 shows a multilayer structure 7 composed of a p-type ZnCdSSe-based superlattice layer 72 composed of six layers and a p-type ZnSe layer 71.
00 and a p-type ZnTe contact layer 73. p
Although the composition of each of the type ZnCdSSe-based superlattice layers 72 is the same, the film thickness is 1 nm sequentially from the ZnSe 70 side.
The thickness is gradually increased to 2 nm, 3 nm, 4 nm, 5 nm, and 6 nm, and the band gap changes sequentially from 2.5 eV to 2.3 eV. The film thickness of p-type ZnSe71 is 1 nm
And constant. Regarding the magnitude of the band offset ΔEv of the valence band of the p-type ZnCdSSe-based superlattice layer 72,
By introducing a composition that generates a compressive strain, ΔEv of the p-type ZnCdSSe-based superlattice layer of the final layer can be increased by 0.4 e
It is possible to take up to V. This structure is simple to fabricate because a superlattice layer of a p-type ZnTe layer is not used in the multilayer structure 700.

(Embodiment 2) A gain guided laser was manufactured using the structure of Embodiment 1. FIG. 4 shows a sectional structural view of the manufactured semiconductor laser. In addition, about the number in a figure, the same number is attached | subjected about the thing equivalent to FIG.

In FIG. 4, the depth is 0.3 in the (011) direction.
A mesa stripe having a width of 10 μm and a width of 10 μm was formed, and both sides of the mesa were buried with a ZnO insulating film 13.
Then, the n-type GaAs substrate 1 has an n-type electrode 14 such as AuGeNi, and the p-type ZnTe contact layer 12 has a AuP
The d electrode 15 was formed by vacuum evaporation. Resonator length is 750
μm, end face coat made of TiOx / SiO2, 70%
(Front end face) / 95% (rear end face), and the current / voltage / light output characteristics during continuous operation at room temperature were measured. One example of the result is shown in FIG. Good values were obtained with a threshold current of about 40 mA and a threshold voltage of about 5 V. At the same time, the normally obtainable characteristics of the conventional structure are also shown. While the threshold voltage was 11 V in the conventional structure, it could be reduced to about half in the present embodiment.

(Embodiment 3) In this embodiment, the first p-type ZnTe of the p-type ZnTe / ZnSe pseudo-gradient layer is used.
A plurality of layers are formed to form a layer having the same structure.
This will be described with reference to FIG.

FIG. 8 shows an epi-structure of the semiconductor laser of the present invention, wherein n-type GaAs substrate 1 (n = 1 × 10 ¹⁸ cm ⁻³ )
Type GaAs buffer layer 2 (n = 1 × 10 ¹⁸ cm ⁻³ )
grown at 280 ° C. and n-type chlorine-doped ZnS
e or ZnS 0.06 Se buffer layer 3 (thickness 10 n
m, n = 1 × 10 ¹⁸ cm ⁻³ ) After growth, n-type chlorine-doped Z
n _0.9 Mg _0.1 S _0.13 Se _0.87 ct layer 4 (n = 1 × 10
¹⁸ cm ^-3 ), n-type ZnS _0.06 Se light guide layer 5 (thickness 1
00 nm), ZnCdSe active layer 6 (thickness 6 nm), Z
An nS _0.06 Se light guide layer 7 (thickness: 100 nm) is grown to form a light emitting region. And p-type nitrogen doped Zn _0.9 Mg
_0.1 S _0.13 Se _0.87 ct layer 8 (p = 1 × 10 ¹⁷ c
m ^-3 ), p-type nitrogen-doped ZnS 0.06 Se layer 9 (p =
^{5 × 10 17 cm - 3)} , p -type nitrogen-doped ZnSe / ZnT
e-superlattice pseudo-gradient layer 11 and p-type nitrogen-doped ZnT
An e-contact layer 12 is formed. p-type nitrogen doped ZnS
The structure of the e / ZnTe superlattice pseudo-gradient layer 11 was a unit, and a pseudo ZnSeTe mixed crystal was formed with the sum of the thicknesses of the ZnSe layer and the ZnTe layer being constant at 2 nm. The detailed configuration is shown in FIG.

The first layer of the pseudo-gradient layer 11 is p-type ZnSe
The layer 20 is 1.9 nm, and the p-type ZnTe layer 21 is 0.1 nm.
And the thickness is sequentially increased or decreased by 0.1 nm. Specifically, two pairs of p-type ZnSe layers 20 (1.9 n thick)
m), p-type ZnTe layer 21 (0.1 nm thick), p-type Z
nSe layer 22 (1.8 nm in thickness) and p-type ZnTe layer 23
(Thickness: 0.2 nm) to form two layers of pseudo mixed crystals. This is the first layer configuration of the p-type nitrogen-doped ZnSe / ZnTe superlattice pseudo-gradient layer 11 with respect to a ZnTe layer having a thickness of 1 to 2 atomic layers, and the Zn layer which is non-uniform in the plane is formed.
By forming a plurality of pairs on the Te layer, an effect of alleviating non-uniformity can be expected. In this embodiment,
Although two pairs were used, three or more pairs were used, and two types having a pseudo-mixed crystal composition were described. However, it goes without saying that more effects can be expected with three or more types.

A semiconductor laser having the above-described structure was prototyped with a structure similar to that shown in FIG. In terms of characteristics, it was confirmed that the driving voltage of about 11 V was reduced to about 5 V as in the first embodiment of FIG.

(Embodiment 4) A specific configuration of an optical disk apparatus using a semiconductor laser will be described with reference to the drawings.

FIG. 14 shows an application of this semiconductor laser to an optical disk device. 520n wavelength from can-type semiconductor laser 801 with laser chip in can
The laser beam 802 of m is collimated by a collimator lens 803, then split into three beams (not shown) by a diffraction grating 804, passes through a half prism 805, and is condensed by a condenser lens 806. Diameter 1 on
Connect a μm spot. The reflected light on the disk 807 passes through the condenser lens 806 again and passes through the half prism 8.
The light is reflected at 05, passes through a cylindrical lens 809 narrowed by a light receiving lens 808, enters a photodiode 810, and is converted into an electric signal.

At this time, the displacement of the optical disc 807 in the radial direction is detected by the divided three beams, and the displacement of the focal point is detected by the cylindrical lens 809. This deviation is corrected by fine adjustment of the optical system by the drive system 811.

As described above, an optical disk device can be realized with a simple configuration by applying the present invention to an optical disk device provided with a condensing optical system for guiding laser light from a semiconductor laser to an optical disk and a photodetector for reading light reflected by the optical disk. .

(Embodiment 5)
Compared with the first embodiment, the laser chip is arranged on the silicon substrate, and the laser chip, the photodiode for detecting the optical signal, and the micromirror that reflects the laser light from the laser chip are configured at once, so that the size is reduced. It is designed to be lighter and lighter.

The schematic structure is shown in FIGS. The laser chip, the photodiode, and the micromirror are collectively referred to herein as a laser unit. The laser light emitted from this laser unit is divided into three beams by a grating pattern formed on the lower surface of the hologram element, and further focused on an information track on the surface of the optical disk by an objective lens through a ４λ plate.

Then, the reflected beam from the optical disk is
The light again passes through the objective lens and the ４λ plate, and is diffracted by the hologram pattern formed on the upper surface of the hologram element, as a ± 1st-order light to the left and right, with the addition of a condensing and diverging action. That is, as shown in FIG.
The diffracted light diffracted to the left becomes a beam having a focal point in front of the light receiving surface of the photodiode, and the diffracted light diffracted to the right becomes a beam having a focal point behind the light receiving surface.

The photodiodes for receiving the reflected beam are formed directly on the silicon substrate on the left and right sides of the concave portion in which the laser chip is arranged, and are each divided into five. FIG.
As described above, the middle three parts of the photodiode are used to detect the focus error signal. FIG. 13 shows a case of just focus, and FIG. 13 shows a case of defocus. The equation for calculating the focus error signal is FES = (1 + 3 + 5) − (2 + 4 +
6), the actuator is driven so that the FES becomes zero, and the objective lens follows the information track of the optical disk.

Similarly, the detection of the tracking error signal becomes TES = (T1−T2) + (T3−T4).
The information signal indicating the recorded content of the optical disc is RFS
= (1 + 3 + 5) + (2 + 4 + 6).

FIG. 12 shows a configuration diagram of the laser unit. As described above, the laser unit forms the concave portion on the silicon substrate, and arranges the semiconductor laser chip in the concave portion. Light emitted from the laser is emitted upward by a micromirror formed on the silicon substrate and having an angle of 45 degrees with respect to the surface of the silicon substrate. The micromirror is formed using the (111) plane of silicon. This is because the (111) plane is easily obtained by anisotropic etching and is a chemically stable plane, so that an optically flat surface is easily obtained.

However, when the silicon (100) plane is used, the (111) plane is at an angle of 54 degrees with the (100) plane, so that the (100) plane is oriented in the <110> direction by 9 degrees.
By using a substrate inclined at an angle of 45 degrees, an angle of 45 degrees can be obtained. The angle of the surface facing the micromirror is 63 degrees, and a monitoring photodiode for monitoring the light output from the laser chip is formed on this surface.

Although the surface of the micromirror is flat silicon, it does not absorb laser light and, in order to increase the light use efficiency, deposits a metal such as gold which has high reflection efficiency and does not absorb laser light. Is preferably reduced.

As described above, the use of the laser unit makes it possible to reduce the size of the optical disk and make it thinner, and also to manufacture the laser in the concave portion on the surface of the silicon substrate on which the photodiodes and micromirrors are formed. Since it is only necessary to arrange the chips, the process can be simplified and the yield can be increased.

[0047]

As described above, according to the present invention, p-type Zn
A semiconductor having a valence band offset of 0.3 eV or less, for example, p-type ZnCdSSe
-Based semiconductor, p-type ZnSe / ZnTe superlattice layer and p-type ZnT
e-contact layer or p-type ZnSSe
Band offset of valence band is 0.3
eV or lower semiconductors, for example, a structure composed of a p-type ZnCdSSe-based semiconductor and a p-type ZnTe contact layer, or a p-type ZnSe / ZnTe superlattice layer formed of a plurality of p-type ZnSeTe pseudo-mixed crystal layers in which the first p-type ZnTe layer is thin. In any of the configurations having a period, the band offset of the valence band is reduced, holes easily flow, and the contact resistance between the electrode and the semiconductor layer can be reduced. Low driving voltage can be achieved with good reproducibility.

Further, when the semiconductor laser manufactured by the structure of the present invention is applied to an optical disk, a laser printer, a medical device, and a display, it can be practically used sufficiently.

[Brief description of the drawings]

FIG. 1 is a structural sectional view of an epitaxial layer of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 shows a conventional semiconductor laser and a band diagram.

FIG. 3 shows a semiconductor laser according to Embodiment 1 of the present invention;
p-type contact structure

FIG. 4 is a structural diagram of a semiconductor laser according to the first embodiment of the present invention;

FIG. 5 is a diagram showing current / light output / voltage characteristics of the semiconductor laser according to the first embodiment of the present invention;

FIG. 6 shows a semiconductor laser according to the first embodiment of the present invention;
p-type contact structure

FIG. 7 shows a semiconductor laser according to the first embodiment of the present invention;
p-type contact structure

FIG. 8 is a structural diagram of a semiconductor laser according to a second embodiment of the present invention.

FIG. 9 shows a semiconductor laser according to a second embodiment of the present invention;
p-type contact structure

FIG. 10 is a configuration diagram of an optical disk device including a semiconductor laser manufactured by using the present invention.

FIG. 11 is a configuration diagram of an optical disk device including a semiconductor laser manufactured by using the present invention.

FIG. 12 is an optical diagram of a hologram integrated module including a semiconductor laser manufactured by using the present invention.

FIG. 13 is a chip configuration diagram of a hologram integrated module including a semiconductor laser manufactured by using the present invention.

FIG. 14 is a diagram showing an optical system of an optical disk device including a semiconductor laser manufactured by using the present invention.

[Explanation of symbols]

 Reference Signs List 1 n-type GaAs substrate 6 ZnCdSe active layer 9 p-type ZnSSe layer 10 p-type ZnCdSSe superlattice layer 11 p-type ZnSe / ZnTe pseudo-gradient layer 12 p-type ZnTe contact layer 13, 22 p-type ZnSe superlattice layer 14, 23 p-type ZnTe superlattice layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Ayumu Tsujimura 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Koji Nishikawa 1006 Okadoma Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (16)

[Claims] An n-type ZnSe or ZnSS is provided on a substrate.
e-compound semiconductor and n-type Zn _1-x Mg _x S
_1-y Se cladding layer consisting of _y-based compound semiconductor, ZnS
A light-emitting layer having a Se-based light guide layer and a ZnCdSe quantum well layer, a second clad layer made of a p-type ZnMgSSe-based semiconductor, and a p-type ZnS _z Se _1-z (0 ≦ z ≦ 0.0
8) a semiconductor layer, and the p-type ZnS _z Se _{1 -z} semiconductor layer is provided with the p-type ZnS _z
A p-type semiconductor having a valence band offset of 0.3 eV or less and a p-type ZnSe / ZnTe with respect to the Se _1-z semiconductor layer.
A semiconductor light emitting device comprising a multilayer semiconductor layer and a p-type ZnTe contact layer. 2. An n-type ZnSe or ZnSS on a substrate.
e-compound semiconductor and n-type Zn _1-x Mg _x S
_1-y Se cladding layer consisting of _y-based compound semiconductor, ZnS
A light-emitting layer having a Se-based light guide layer and a ZnCdSe quantum well layer, a second clad layer made of a p-type ZnMgSSe-based semiconductor, and a p-type ZnS _z Se _1-z (0 ≦ z ≦ 0.0
8) a semiconductor layer, and p-type Zn ₁ -αCd is formed on the p _- type ZnS _z Se ₁ -z semiconductor layer.
A semiconductor light emitting device comprising an αS ₁ -βSeβ (0 ≦ α, β ≦ 1) compound semiconductor, a p-type ZnSe / ZnTe multilayer semiconductor layer, and a p-type ZnTe contact layer. 3. The Cd composition α is 50% or less, and the S composition β is 30%.
The semiconductor light emitting device according to claim 2, wherein the thickness is 6 nm or less. 4. A p-type ZnS_zSe_1-z(0 ≦ z ≦ 0.08)
P-type Zn on the semiconductor layer _1-αCdαS_1-βSeβ (0 ≦
α, β ≦ 1) Compound semiconductor and p-type ZnS_zSe_1-zsemiconductor
Layer and p-type Zn_1-α‘Cdα'S_1-β‘Seβ '(0 ≦ α
‘, Β '≦ 1) A multilayer film structure in which a compound semiconductor is repeated
3. The semiconductor light emitting device according to claim 2, comprising:
Child. 5. An n-type ZnSe or ZnSS on a substrate
e-compound semiconductor and n-type Zn _1-x Mg _x S
_1-y Se cladding layer consisting of _y-based compound semiconductor, ZnS
A light-emitting layer having a Se-based light guide layer and a ZnCdSe quantum well layer, a second clad layer made of a p-type ZnMgSSe-based semiconductor, and a p-type ZnS _z Se _1-z (0 ≦ z ≦ 0.0
8) a semiconductor layer, and p-type Zn ₁ -αCd is formed on the p _- type ZnS _z Se ₁ -z semiconductor layer.
_{αS 1- βSeβ (0 ≦ α,} β ≦ 1) multilayer semiconductor layer and the p-type ZnTe formed of a compound semiconductor and a p-type ZnS _z Se _1-z
A semiconductor light-emitting device comprising a contact layer. 6. An n-type ZnSe or ZnSS on a substrate.
e-compound semiconductor and n-type Zn _1-x Mg _x S
_1-y Se cladding layer consisting of _y-based compound semiconductor, ZnS
A light-emitting layer having a Se-based light guide layer and a ZnCdSe quantum well layer, a second clad layer made of a p-type ZnMgSSe-based semiconductor, and a p-type ZnS _z Se _1-z (0 ≦ z ≦ 0.0
8) and a semiconductor layer, the p-type ZnS _z Se _1-z semiconductor layer, a p-type ZnTe semiconductor layer gradually decrease the sequential thick p-type ZnSe semiconductor layer and the p-type ZnSe / ZnTe multilayer semiconductor layer 1. A semiconductor light emitting device comprising: a plurality of p-type ZnTe semiconductor layers having the same thickness on the side of the p-type ZnS _z Se _1-z semiconductor layer; 7. A semiconductor laser according to claim 1, a condensing optical system for converging laser light emitted from said semiconductor laser on a recording medium, and receiving reflected light from said recording medium. An optical disc device provided with a photodetector. 8. The semiconductor laser chip is disposed in a concave portion formed in the silicon, and a laser beam emitted from the laser is reflected by a micro mirror formed in the silicon and substantially reflected by the silicon. The optical disk device according to claim 7, wherein the optical disk device travels in a vertical direction. 9. An optical storage device applied to optical recording of an optical disk or the like using the semiconductor laser according to claim 1. 10. An information recording apparatus using the semiconductor laser according to any one of claims 1 to 6 for printing plate making of a printer or the like. 11. A medical device using the semiconductor laser according to claim 1 for blood analysis or disease treatment. 12. A display device applied to a display such as a laser pointer using the semiconductor laser according to claim 1. 13. A communication device applied to optical information communication such as optical fiber communication using the semiconductor laser according to claim 1. 14. A p-type semiconductor and a p-type ZnSe having a valence band band offset of 0.3 eV or less with respect to the p-type ZnS _z Se _1-z semiconductor layer on the p-type ZnS _z Se _1-z semiconductor layer.
/ A semiconductor device having a ZnTe multilayer semiconductor layer and a p-type ZnTe contact layer. 15. A p-type semiconductor of 0.3 eV or less is a p-type Z
The semiconductor device according to claim 14, wherein the semiconductor device is a compound semiconductor of n ₁ -αCdαS ₁ -βSeβ (0 ≦ α, β ≦ 1). 16. A p-type semiconductor of 0.3 eV or less is p-type Z
_{n 1- αCdαS 1- βSeβ (0 ≦} α, β ≦ 1) compound semiconductor and a p-type ZnS _z semiconductor device according to claim 14 Se consisting _1-z multilayer film is a semiconductor layer.