JP2001210916A - Semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the threshold current density and operating current of a light-emitting element and prolong the service life of the element, without having to use complicated structure such as GRIN structure. SOLUTION: In a ZnSe based semiconductor laser, an N-type ZnMgSSe clad layer 5, an N-type ZnSSe optical guide layer 6, an active layer 8, a P-type ZnSSe optical guide layer 10 and a P-type ZnMgSSe clad layer 11 are laminated in this order. Between the N-type ZnMgSSe optical guide layer 6 and the active layer 8, an N-type ZnSe intermediate layer 7, having a band gap and a refractive index which are intermediate between those of the layer 6 and the layer 8, is formed. Between the P-type ZnSSe optical guide layer 10 and the active layer 8, a P-type ZnSe intermediate layer 9, having a band gap and a refractive index which are intermediate between those of the layer 10 and the layer 8, is formed.

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, and more particularly, to a semiconductor light emitting device which is suitably applied to a semiconductor laser or a light emitting diode using a II-VI compound semiconductor.

[0002]

2. Description of the Related Art II-VI compound semiconductors, especially Z
A semiconductor light emitting device composed of II-VI group mixed crystal such as nSe, ZnTe, ZnS, etc.
It emits blue and green light and is expected to be applied to a light source for writing / reading of a high-density optical disk, a full-color display, and the like.

FIG. 8 shows a conventional ZnSe-based semiconductor laser. As shown in FIG. 8, in this ZnSe-based semiconductor laser, an n-type GaAs
s buffer layer 102, n-type ZnSe buffer layer 103,
n-type ZnSSe buffer layer 104, n-type ZnMgSSe
Cladding layer 105, n-type ZnMgSSe light guide layer 10
6, for example, an active layer 107 made of an undoped ZnCdSe layer, a p-type ZnMgSSe light guide layer 108, a p-type Z
An nMgSSe cladding layer 109, a p-type ZnSSe contact layer 110, a p-type ZnSe contact layer 111, a p-type ZnSe / ZnTe multiple quantum well (MQW) layer 112, and a p-type ZnTe contact layer 113 are sequentially stacked.

The upper layer of the p-type ZnSSe contact layer 110, the p-type ZnSe contact layer 111, and the p-type ZnSe /
The ZnTeMQW layer 112 and the p-type ZnTe contact layer 113 have a stripe shape extending in one direction.
An insulating layer 114 made of Al ₂ O ₃ is formed on the p-type ZnSSe contact layer 110 in a portion other than the stripe portion.
Are provided, whereby a current confinement structure is formed.

On the insulating layer 114 and the p-type ZnTe contact layer 113 having a stripe shape, for example, Pd /
A Pt / Au structure p-side electrode 115 is provided in ohmic contact with the p-type ZnTe contact layer 113. On the other hand, on the back surface of the n-type GaAs substrate 101, Pd
An n-side electrode 116 such as a / AuGe / Ti / Au electrode is provided in ohmic contact.

FIG. 9 shows an energy band diagram of the above-mentioned ZnSe-based semiconductor laser. Note that in FIG. 9, E _C is the bottom energy of the conduction band, E _V is the upper end of the energy of the valence band.

So far, various research institutes have reported on blue-green light emitting ZnSe-based light emitting devices.
As one method of achieving a further longer life, reduction of the threshold current density and the operating current is considered (23rd
Int. Conf.Physics of Semiconductors 1996, pp.311
5-3162).

In order to reduce the threshold current density and the operating current, measures taken near the active layer include:
There is a method of reducing carrier overflow by improving the confinement of light and carriers.

As a method for realizing this, a method in which the band gap of the cladding layer (ZnMgSSe layer) is made larger than that of the active layer can be considered, but this is naturally limited due to the problem of doping of p-type impurities. That is, when the band gap of the cladding layer is increased, the carrier concentration of the p-type cladding layer decreases, so that the band gap difference between the p-type cladding layer and the active layer can be increased only to a certain value.

Further, by increasing the Cd composition of the active layer, the band gap difference between the clad layer and the active layer can be increased. However, Ga
An increase in strain of the active layer 107 with respect to the As substrate 101,
Because of this, the thickness of the critical film may be reduced.
Not only is the degree of freedom of design severely restricted, but also the characteristics are deteriorated such as an increase in threshold current density.

Therefore, as a method for improving confinement,
Optimization of the thickness of the light guide layer has been performed. Furthermore, a structure in which the composition of the light guide layer is changed as it approaches the active layer to reduce the threshold current by improving the confinement of light and carriers, so-called GRIN (Graded)
Index) structure has been adopted. FIG. 10 shows an example in which the GRIN structure is employed in the ZnSe-based semiconductor laser shown in FIG.

[0012]

As shown in FIG.
In the GRIN structure, it is necessary to change the composition ratio of the mixed crystal during growth. Therefore, in addition to the need for high reproducibility in the crystal growth technique associated with changing the composition ratio of the mixed crystal, the only method for evaluating the manufactured device is to observe it with a TEM (transmission electron microscope). Because there is no simple method, there are many difficulties not only in mass production technology but also in research and development.

Accordingly, an object of the present invention is to provide a semiconductor light emitting device which can achieve a reduction in threshold current density, a reduction in operating current and a long life without using a complicated device structure or manufacturing method. To provide.

[0014]

In order to achieve the above object, the present invention provides a first cladding layer of a first conductivity type, a first optical guide layer on the first cladding layer, An active layer on the optical guide layer, a second optical guide layer on the active layer, and a second cladding layer of the second conductivity type on the second optical guide layer. A first light guide layer, an active layer,
The second light guide layer and the second cladding layer are made of Zn, B
at least one group II element selected from the group consisting of e, Mg, Cd and Hg and at least one type V selected from the group consisting of Se, S, Te and O
In a semiconductor light emitting device composed of a II-VI compound semiconductor comprising a group I element, the semiconductor light emitting device has a band gap between a band gap of a first light guide layer and a band gap of an active layer, and A first having a refractive index between the refractive index of the light guide layer and the refractive index of the active layer;
An intermediate layer is provided between the first light guide layer and the active layer, and has a band gap between the band gap of the second light guide layer and the band gap of the active layer;
A second intermediate layer having a refractive index between the refractive index of the second light guide layer and the refractive index of the active layer is provided between the second light guide layer and the active layer. It is assumed that.

In the present invention, preferably, a first strain canceling layer is provided between the first intermediate layer and the active layer so as to compensate for the strain in the active layer. Further, in the present invention, a second strain canceling layer is provided between the active layer and the second intermediate layer so as to compensate for the distortion of the active layer.

In the present invention, typically, the first intermediate layer is a non-doped ZnSe layer or a first conductivity type ZSe layer.
It is an nSe layer.

In the present invention, typically, the second intermediate layer is a non-doped ZnSe layer or a second conductivity type ZSe layer.
It is an nSe layer.

In the present invention, typically, the first light guide layer is a non-doped ZnSSe layer, a first conductivity type ZnSSe layer, a non-doped ZnMgSSe layer, or a first conductivity type ZnMgSSe layer. In the present invention, typically, the second optical guide layer is a non-doped ZnSSe layer, a second conductivity type ZnSSe layer, a non-doped ZnMgSSe layer, or a second conductivity type ZnMgSSe layer.
e layer.

In the present invention, typically, the active layer is a non-doped ZnCdSe layer, a first conductivity type ZnCdSe layer.
It is a dSe layer, a non-doped ZnCdSSe layer, or a ZnCdSSe layer of the first conductivity type.

In the present invention, typically, the first conductivity type is n-type and the second conductivity type is p-type, but the first conductivity type is p-type and the second conductivity type is n-type. Is also good.

According to the semiconductor light emitting device of the present invention configured as described above, between the light guide layer and the active layer,
An intermediate layer having a band gap between the band gap of the light guide layer and the band gap of the active layer, and having a refractive index between the refractive index of the light guide layer and the refractive index of the active layer is provided. Thus, a structure similar to the GRIN structure can be obtained without using the GRIN structure.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIG. 1 shows the ZnS according to the first embodiment.
It is sectional drawing which shows the structure of e type semiconductor laser. This semiconductor laser has an SCH structure.

As shown in FIG. 1, in this ZnSe-based semiconductor laser, an n-type GaAs buffer layer 2 and an n-type ZnSe buffer are provided on an n-type GaAs substrate 1 doped with, for example, silicon (Si) as an n-type impurity. Layer 3, n
-Type ZnSSe buffer layer 4, n-type ZnMgSSe cladding layer 5, n-type ZnSSe optical guide layer 6, n-type ZnSe intermediate layer 7, for example, active layer 8 of SQW structure using undoped ZnCdSe layer as quantum well layer, p-type ZnSe intermediate Layer 9, p-type ZnSSe light guide layer 10, p-type ZnMgSS
e-clad layer 11, p-type ZnSSe contact layer 12,
p-type ZnSe contact layer 13, p-type ZnSe / ZnT
An e multiple quantum well (MQW) layer 14 and a p-type ZnTe cap layer 15 are sequentially stacked.

Here, the n-type GaAs buffer layer 2 has
For example, Si is doped as an n-type impurity and n-type ZnS
e-buffer layer 3, n-type ZnSSe buffer layer 4, n-type Z
The nMgSSe cladding layer 5 and the n-type ZnMgSSe optical guide layer 6 are each doped with, for example, chlorine (Cl) as an n-type impurity, and the p-type ZnSSe optical guide layer 1 is formed.
0, p-type ZnMgSSe cladding layer 11, p-type ZnSS
e contact layer 12, p-type ZnSe contact layer 13,
The p-type ZnSe layer, the p-type ZnTe layer, and the p-type ZnTe contact layer 15 of the p-type ZnSe / ZnTe MQW layer 14 are each doped with, for example, N as a p-type impurity. In addition, to give an example of the carrier concentration of each layer, the n-type GaAs buffer layer 2 is 2 × 10 ¹⁸ cm.
^-3 , the n-type ZnSe buffer layer 3 is 2 × 10 ¹⁸ cm
^-3 , n-type ZnSSe buffer layer 4 is 1 × 10 ¹⁸ cm
^-3 , the n-type ZnMgSSe cladding layer 5 is 2 × 10 ¹⁷
cm ⁻³ , the p-type ZnMgSSe cladding layer 11 is 1 × 1
0 ¹⁷ cm ⁻³ , the p-type ZnSSe contact layer 12 is 6
× 10 ¹⁷ cm ⁻³ , the p-type ZnSe contact layer 13 is 1 × 10 ¹⁸ cm ⁻³ , and the p-type ZnTe cap layer 15 is 1 × 10 ¹⁹ cm ⁻³ .

As an example of the thickness of each layer forming the laser structure, the n-type GaAs buffer layer 2 has a thickness of 250 nm.
m, n-type ZnSe buffer layer 3 is 30 nm, ZnSSe
The buffer layer 4 has a thickness of 260 nm, the n-type ZnMgSSe cladding layer 5 has a thickness of 0.9 μm, and the n-type ZnSSe light guide layer 6 and the p-type ZnSSe light guide layer 10 have a thickness of 100 nm.
m, the p-type ZnMgSSe cladding layer 11 is 1.1 μm,
The p-type ZnSSe contact layer 12 is 1.8 μm
The thickness of the nSe contact layer 13 is 120 nm.

The n-type ZnSe intermediate layer 7 and the p-type Z
The thickness of the nSe intermediate layer 9 is determined as follows. That is, according to the knowledge of the present inventor, the critical thickness of the ZnSe layer continuously grown on the GaAs substrate is estimated to be about 150 nm. If the thickness exceeds the critical thickness of the ZnSe layer, lattice relaxation accompanied by misfit dislocations starts, which is not desirable from the viewpoint of device life. Therefore, the active layer 8, the n-type ZnSSe optical guide layer 6 and the p-type ZnSSe
The thickness of the n-type ZnSe intermediate layer 7 and the p-type ZnSe intermediate layer 9 provided between the n-type ZnSSe light guide layer 10 and the p-type ZnSe intermediate layer 9 are typically 0.28 (one monolayer, 1ML).
To 100 nm, preferably 0.56 to 75 nm, more preferably 0.84 to 33.3 nm.

Further, the upper layer of the p-type ZnSe contact layer 12, the p-type ZnSe contact layer 13, and the p-type ZnSe
/ ZnTe MQW layer 14 and p-type ZnTe cap layer 15 have a stripe shape extending in one direction. An insulating layer 16 made of, for example, Al ₂ O ₃ is provided on the p-type ZnSSe contact layer 12 in a portion other than the stripe portion, thereby forming a current confinement structure.

The insulating layer 16 and the stripe-shaped p
On the type ZnTe cap layer 15, for example, Pd / Pt /
The p-side electrode 17 having the Au structure is formed of the p-type ZnTe cap layer 1.
5 in ohmic contact. on the other hand,
On the back surface of the n-type GaAs substrate 1, for example, Pd / AuGe
An n-side electrode 18 having a / Ti / Au structure is provided in ohmic contact.

Further, the ZnSe according to the first embodiment
The resonator length of the system semiconductor laser is, for example, 1 mm, and has a resonator end face composed of a cleavage plane.

Next, a method of manufacturing the ZnSe-based semiconductor laser according to the first embodiment configured as described above will be described.

In order to manufacture this ZnSe-based semiconductor laser, first, an n-type GaAs substrate 1 is placed in a substrate holder in a vacuum vessel evacuated to an ultra-high vacuum of a not-shown MBE apparatus for growing a III-V compound semiconductor. Attach. Next, after heating the n-type GaAs substrate 1 to a predetermined growth temperature,
The n-type GaAs is formed on the n-type GaAs substrate 1 by the MBE method.
The s buffer layer 2 is grown. In this case, doping of Si, which is an n-type impurity, is performed using a Si molecular beam source (Knudsen cell). The growth of the n-type GaAs buffer layer 2 is performed by heating the n-type GaAs substrate 1 to a temperature of, for example, about 580 ° C. and thermally etching the surface to remove a surface oxide film and clean the surface. May be done after

Next, the n-type GaAs substrate 1 on which the n-type GaAs buffer layer 2 has been grown as described above is transferred via a vacuum transfer path (not shown) to the above-described III-V compound semiconductor growth. It is transported from the MBE apparatus to an MBE apparatus (not shown) for growing a II-VI group compound semiconductor. And
In this MBE apparatus, each II forming a laser structure
Growing a group VI compound semiconductor layer; In this case, the surface of the n-type GaAs buffer layer 2 is kept clean because it is not exposed to the air during its transportation to the MBE apparatus after its growth.

In the MBE apparatus for growing a II-VI group compound semiconductor, a substrate holder is provided in a vacuum vessel evacuated to an ultra-high vacuum by an ultra-high vacuum evacuation apparatus, and growth is performed on the substrate holder. The substrate to be held is held. A plurality of molecular beam sources (Knudsen cells) are mounted in the vacuum vessel so as to face the substrate holder. In this case, as a molecular beam source, Zn, Se, Mg, ZnS,
Molecular beam sources such as Te, Cd and ZnCl ₂ are provided. A shutter (not shown) is provided in front of each of these molecular beam sources so as to be openable and closable. Further, a plasma cell using electron cyclotron resonance (ECR) or radio frequency (RF) is mounted in the vacuum vessel so as to face the substrate holder.

Now, in order to grow each II-VI group compound semiconductor layer forming a laser structure on the n-type GaAs buffer layer 2, the n-type GaAs buffer layer 2 is placed on a substrate holder in a chamber of the MBE apparatus. Has grown
The GaAs substrate 1 is mounted. Next, the n-type GaAs
The substrate 1 is set at a predetermined growth temperature, for example, about 250 ° C., and growth by the MBE method is started. That is, n-type GaAs
On the s buffer layer 2, an n-type ZnSe buffer layer 3, an n-type ZnSSe buffer layer 4, an n-type ZnMgSSe cladding layer 5, an n-type ZnMgSSe light guide layer 6, an n-type ZnSe
Intermediate layer 7, active layer 8, p-type ZnSe intermediate layer 9, p-type Zn
MgSSe optical guide layer 10, p-type ZnMgSSe cladding layer 11, p-type ZnSSe contact layer 12, p-type Zn
Se contact layer 13, p-type ZnSe / ZnTe MQW
The layer 14 and the p-type ZnTe cap layer 15 are sequentially grown.

The above-described growth of the n-type ZnSe intermediate layer 7 is performed by using an openable and closable shutter provided in front of the molecular beam source of S during the growth sequence of the n-type ZnSSe light guide layer 6 according to the conventional method. Close and do. Also, p-type ZnSe
The intermediate layer 9 is grown by growing the active layer 8, closing the shutter of the Cd molecular beam source, and growing the p-type ZnSe intermediate layer 9 to a desired thickness. Then, the shutter of the molecular beam source of S is opened, and p-type ZnSS
e Grow the light guide layer 10. These n-type ZnSe
In controlling the film thickness of the intermediate layer 7 and the p-type ZnSe intermediate layer 9, for example, by using an SEM (scanning electron microscope),
The growth rate is measured by measuring the thickness of another ZnSe layer. Then, the growth film thickness is calculated by measuring the growth time based on the growth rate.

As described above, it can be seen that the thicknesses of the n-type ZnSe intermediate layer 7 and the p-type ZnSe intermediate layer 9 can be easily controlled. In addition, since the correlation with the half-value width of the PL spectrum has been confirmed, it is not necessary to fabricate a laser device structure. For example, in a sample in which a structure near the active layer is embedded on a ZnSSe layer, the PL
It is also possible to perform spectrum optimization.

The n-type ZnSe buffer layer 3 and the n-type ZSe
The doping of the nSSe buffer layer 4, the n-type ZnMgSSe cladding layer 5, and the n-type ZnMgSSe light guide layer 6 with Cl as an n-type impurity is performed using, for example, ZnCl ₂ as a dopant. Also, a p-type ZnMgSSe optical guide layer 10, a p-type ZnMgSSe cladding layer 11, a p-type ZnMgSSe
N doping of the nSSe contact layer 12, the p-type ZnSe contact layer 13, the p-type ZnSe / ZnTe MQW layer 14, and the p-type ZnTe cap layer 15 with N as a p-type impurity is performed by a plasma of an MBE apparatus for growing a II-VI group compound semiconductor. In the cell, N ₂ gas introduced from a gas introduction pipe (not shown) is turned into plasma, and the N ₂ plasma generated thereby is irradiated onto the substrate surface.

Next, a stripe-shaped resist pattern (not shown) extending in one direction is formed on the p-type ZnTe cap layer 15 by lithography, and the resist pattern is used as a mask to form p-type resist by, for example, wet etching. Etching is performed to an intermediate depth in the thickness direction of the type ZnSSe contact layer 12. Thereby, the p-type Z
The upper layer portion of the nSSe contact layer 12, the p-type ZnSe contact layer 13, the p-type ZnSe / ZnTe MQW layer 14, and the p-type ZnTe cap layer 15 are patterned in a stripe shape.

Next, an Al ₂ O ₃ film is formed on the entire surface by a CVD method or the like while leaving the resist pattern used for the etching as it is. Thereafter, the resist pattern is removed together with the Al ₂ O ₃ film thereon (lift-off). Thereby, the upper layer portion of the p-type ZnSSe contact layer 12 patterned in a stripe shape,
p-type ZnSe contact layer 13, p-type ZnSe / ZnT
An insulating layer 16 is formed on both sides of the eMQW layer 14 and the p-type ZnTe cap layer 15.

Next, a Pd film, a Pt film, and an Au film are sequentially formed on the entire surface of the stripe-shaped p-type ZnTe cap layer 15 and the insulating layer 16 on both sides thereof by, for example, a vacuum deposition method to form Pd / Pt / Au. A p-side electrode 17 having a structure is formed. Thereafter, heat treatment is performed as necessary,
The side electrode 17 is brought into ohmic contact with the p-type ZnTe cap layer 15. On the other hand, an n-side electrode 18 having a Pd / AuGe / Ti / Au structure is formed on the back surface of the n-type GaAs substrate 1.

Next, the n-type GaAs substrate 1 on which the laser structure has been formed as described above is cleaved into a bar shape to form both cavity end faces, and, if necessary, end face coating. The bar is cleaved into chips. The laser chip thus obtained is mounted on a heat sink, packaging is performed, and the intended ZnSe
Based semiconductor laser is manufactured.

FIG. 2 shows an energy band diagram of the ZnSe-based semiconductor laser according to the first embodiment manufactured as described above. Incidentally, in FIG. 2, E _C is the bottom energy of the conduction band, E _V is the upper end of the energy of the valence band.

As shown in FIG. 2, the n-type ZnSe intermediate layer 7
Band gap _{E g7} in has a band gap between band gaps _{E g8} and n-type ZnSSe optical guide layer bandgap _{E g6} 6 of the active layer 8, p-type Zn
The band gap E _g9 of the Se intermediate layer 9 is different from the band gap E _g8 of the active layer 8 and the p-type ZnSSe light guide layer 10.
_Has a band gap between the band gap E _g10 and the band gap E _g10 . The refractive index of the n-type ZnSe intermediate layer 7 is a refractive index between the refractive index of the active layer 8 and the refractive index of the n-type ZnSSe light guide layer 6, and the refractive index of the p-type ZnSe intermediate layer 9 is
This is a refractive index between the refractive index of the active layer 8 and the refractive index of the p-type ZnSSe light guide layer 10.

Here, FIG. 3A shows the measurement result of the active layer peak spectrum by PL measurement of a conventional ZnSe-based semiconductor laser in which the n-type ZnSe intermediate layer 7 and the p-type ZnSe intermediate layer 9 are not provided. FIG. 3B shows a result of measuring an active layer peak spectrum by PL measurement of a ZnSe-based semiconductor laser according to the first embodiment in which the thickness of each of the n-type ZnSe intermediate layer 7 and the p-type ZnSe intermediate layer 9 is 5 nm. Show.

FIG. 3A shows that the conventional ZnSe-based semiconductor laser has a half width of 4.7 nm (25 meV). FIG. 3B shows that the ZnSe-based semiconductor laser according to the first embodiment has a half width of 3.
It turns out that it is 9 nm (20 meV). Therefore, the n-type ZnSe intermediate layer 7 is provided between the n-type ZnSSe light guide layer 6 and the active layer 8, and the p-type ZnSe intermediate layer 9 is
It can be seen that the half width can be reduced by providing between the active layer 8 and the type ZnSSe light guide layer 10. This reflects improved light confinement. Further, according to the knowledge of the present inventor, the half width shown in FIG. 3B is the narrowest half width of the laser device structure manufactured so far. Although not shown, the same measurement was performed when the thickness of each of the n-type ZnSe intermediate layer 7 and the p-type ZnSe intermediate layer 9 was set to 33.3 nm.
m (22 meV), and it was confirmed that the half-value width could be narrowed as compared with the related art.

Further, the conventional ZnSe-based semiconductor laser 3
The IVL characteristics after assembly were measured for the four samples. FIG. 4 shows the average of the measurement results. Similarly, the n-type ZnSe intermediate layer 7 and the p-type ZnSe
The IVL characteristics after assembly were measured for 34 samples of the ZnSe-based semiconductor laser according to the first embodiment in which the thickness of the intermediate layer 9 was 5 nm.
FIG. 5 shows the average of the measurement results. Similarly, the n-type ZnSe intermediate layer 7 and the p-type ZnSe intermediate layer 9
The I-V-L characteristics after assembly were measured for 28 samples of the ZnSe-based semiconductor laser according to the first embodiment, each having a thickness of 33.3 nm. FIG. 6 shows the average of these measurement results. The cavity length of the ZnSe-based semiconductor laser used for this measurement was 1
mm, the stripe width is 10 μm, and the end face of the resonator is non-coated. 4 to 6, the horizontal axis represents operating current (mA), one vertical axis represents optical output (mW), the other vertical axis represents operating voltage (V), and a curve a represents a graph of optical output. Curve b is a graph of the operating voltage.

FIG. 4 shows that the average threshold current I _{th av.} Is 68.1m
It turns out that it is A. This average threshold current I
_{thav .} Threshold current density J corresponding to
_thav. Is 681 A / cm ² . Also, the minimum threshold current I in 34 samples
_thmin. Was found to be 67.2 mA.
This minimum threshold current I _thmin. , The minimum threshold current density J _thmin. Is 672 A / cm ²
It is. The variance σ was 0.53 mA.

FIG. 5 shows that the average threshold current I _{thav. In} the ZnSe-based semiconductor laser according to the first embodiment in which the ZnSe intermediate layer has a thickness of 5 nm _. Is 6
It turns out that it is 6.7 mA. This average threshold current I _thav. Threshold current density J corresponding to
_thav. Is 667 A / cm ² . Also, the minimum threshold current I in 34 samples
_thmin. Was 65.1 mA.
This minimum threshold current I _thmin. , The minimum threshold current density J _thmin. Is 651 A / cm ²
It is. The variance σ was 1.17 mA.

FIG. 6 shows that in the ZnSe-based semiconductor laser according to the first embodiment in which the thickness of the ZnSe intermediate layer is 33.3 nm, the average threshold current I
_thav. Is 69.1 mA. This average threshold current I _thav. Average threshold current density J _thav. Is 691 A / cm ² .
Further, the minimum threshold current I _thmin. Was found to be 66.0 mA. This minimum threshold current I _thmin. , The minimum threshold current density J _thmin. Is 660 A / c
a m ^2. The variance σ was 1.88 mA.

As described above, according to the first embodiment, the band gap and the refractive index between the band gap and the refractive index of the n-type ZnSSe light guide layer 6 and the band gap and the refractive index of the active layer 8 are determined. An n-type ZnSe intermediate layer 7 having a refractive index is provided between the n-type ZnSSe light guide layer 6 and the active layer 8, and the band gap and the refractive index of the p-type ZnSSe light guide layer 12 and the band gap of the active layer 8 By providing the p-type ZnSe intermediate layer 7 having a band gap and a refractive index between the n-type ZnSSe light guide layer 6 and the active layer 8 between the n-type ZnSSe light guide layer 6 and the active layer 8, the GRIN structure is complicated and difficult to manufacture. Since the structure similar to the GRIN structure can be simulated without using the structure, it is difficult to form the GRIN structure. No, it is possible to obtain the same effect as in the GRIN structure. This makes it possible to satisfactorily confine light and carriers in a semiconductor light emitting device using a II-VI compound semiconductor, to reduce threshold current density in laser oscillation and to reduce reactive current in operating current. And the luminous efficiency can be increased. Therefore, it is possible to reduce the operating current in the constant light output operation, to reduce the power consumption, and to suppress the thermal and micro-deterioration caused by point defects at the core. Therefore, the life of the device can be significantly extended. In addition, since low power consumption can be achieved, the degree of freedom in using a full-color display device or a magneto-optical medium as a light source increases, so that application to consumer and portable devices can be easily performed. .

Next, Z according to the second embodiment of the present invention will be described.
An nSe-based semiconductor laser will be described. FIG. 7 is a sectional view showing the structure of the ZnSe-based semiconductor laser according to the second embodiment. This semiconductor laser has an SCH structure.

As shown in FIG. 7, in the ZnSe-based semiconductor laser according to the second embodiment, n-type ZnSe
Between the intermediate layer 7 and the active layer 8, an n-type ZnSSe strain canceling layer 21 for compensating the distortion of the active layer 8 is provided, and the active layer 8 is provided between the active layer 8 and the p-type ZnSe intermediate layer 9. 8 is provided with a p-type ZnSSe strain canceling layer 22 that compensates for the strain of FIG. The S composition in the n-type ZnSSe strain canceling layer 21 and the p-type ZnSSe strain canceling layer 22 is such that the ZnC
While the Cd composition in the dSe layer is about 6%,
For example, it is selected to be about 20%.

The n-type ZnSe intermediate layer 7 hardly affects the effectiveness of the n-type ZnSSe strain canceling layer 21, and the p-type ZnSe intermediate layer 9 hardly affects the efficiency of the p-type ZnSSe strain canceling layer 22. Do not give. In addition, since the lattice constant of ZnSe is known, the shift in the degree of distortion cancellation when the n-type ZnSe intermediate layer 7 is provided between the active layer 8 and the n-type ZnSSe light guide layer 6 is reduced by the n-type ZSe.
By changing the film thickness and composition (particularly, S composition) of the nSSe strain canceling layer 21, it is possible to easily correct it. The same applies to the p-type ZnSSe strain canceling layer 22 provided between the active layer 8 and the p-type ZnSe intermediate layer 9.

The other configuration of the ZnSe-based semiconductor laser is the same as that of the ZnSe-based semiconductor laser according to the first embodiment, and the description is omitted. The method for manufacturing the ZnSe-based semiconductor laser is the same as that in the first embodiment.

According to the ZnSe-based semiconductor laser according to the second embodiment, the same effect as that of the first embodiment can be obtained, and n-type ZnSe intermediate layer 7 and n-type active layer 8 By providing the p-type ZnSSe strain canceling layer 21 and the p-type ZnSSe strain canceling layer 22 between the active layer 8 and the p-type ZnSe intermediate layer 9, the strain of the active layer 8 is compensated. In addition, the stress generated in the active layer 8 can be reduced, and a ZnSe-based semiconductor laser having higher quality and excellent operating characteristics can be realized.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications based on the technical concept of the present invention are possible.

For example, the structures and materials of the semiconductor lasers according to the first and second embodiments are merely examples, and different structures and materials may be used as needed.

Further, for example, in the first embodiment described above, a non-doped ZnCdSe layer is used as the active layer 8, but the active layer 8 is made of a non-doped ZnCdSe layer.
An SSe layer may be used, or an n-type ZnCdSe layer or an n-type ZnCdSSe layer may be used.

Also, for example, instead of the active layer 8 having the SQW structure in the first and second embodiments, the MQW
An active layer having a structure may be used. Further, for example, the light guide layers in the first and second embodiments may be non-doped. Also, for example, the n-type ZnSSe light guide layer 6 and the p-type ZnSSe light guide layer 6 in the first and second embodiments are used.
Instead of the type ZnSSe light guide layer 10, n
-Type ZnMgSSe optical guide layer and p-type ZnMgSSe
A light guide layer may be used. In addition, for example, the first
In the second embodiment, the structure may be such that the n-type ZnSSe buffer layer 4 is omitted.

In the first and second embodiments, the MBE is used for growing the II-VI group compound semiconductor layer.
Although the method is used, the metal-organic chemical vapor deposition (MOCVD) method may be used for growing the II-VI group compound semiconductor layer.

Further, in the first and second embodiments described above, the case where the present invention is applied to a semiconductor laser has been described. However, the present invention can be applied to a light emitting diode. Further, the present invention can be applied to a semiconductor light emitting device using a p-type semiconductor substrate.

[0063]

As described above, according to the present invention, the gap between the band gap of the first light guide layer and the band gap of the active layer is provided between the first light guide layer and the active layer. A first layer having a band gap and a refractive index between the refractive index of the first light guide layer and the active layer;
Is provided, and between the second light guide layer and the active layer,
A second light guide layer having a band gap between the band gap and the active layer;
By providing the second intermediate layer having a refractive index between the refractive index of the light guide layer and the refractive index of the active layer, the vicinity of the active layer can be reduced without using a complicated element structure or a manufacturing method. Can be simulated to have a structure similar to the GRIN structure, so that the threshold current density, the operating current, and the life of the semiconductor light emitting device can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a ZnSe-based semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is an energy band diagram of the ZnSe-based semiconductor laser according to the first embodiment of the present invention.

FIG. 3 shows a PL of a ZnSe-based semiconductor laser according to the related art.
The measured active layer peak spectrum and the first spectrum of the present invention
13 is a graph showing an active layer peak spectrum by PL measurement of the ZnSe-based semiconductor laser according to the embodiment.

FIG. 4 is a graph showing IVL characteristics of a ZnSe-based semiconductor laser after assembly according to a conventional technique.

FIG. 5 is a graph showing the IVL characteristics of the assembled ZnSe-based semiconductor laser according to the first embodiment of the present invention.

FIG. 6 is a graph showing IVL characteristics after assembling in the ZnSe-based semiconductor laser according to the first embodiment of the present invention.

FIG. 7 is a sectional view of a ZnSe-based semiconductor laser according to a second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a ZnSe-based semiconductor laser according to the related art.

FIG. 9 is a band gap diagram of the ZnSe-based semiconductor laser shown in FIG.

10 shows a GRI applied to the ZnSe-based semiconductor laser shown in FIG.
It is a band gap figure of the example which adopted the N structure.

[Explanation of symbols]

1 ... n-type GaAs substrate, 5 ... n-type ZnMgSS
e-clad layer, 6... n-type ZnSSe light guide layer, 7
... n-type ZnSe intermediate layer, 8 ... active layer, 9 ...
p-type ZnSe intermediate layer, 10 ... p-type ZnSSe optical guide layer, 11 ... p-type ZnMgSSe cladding layer, 21
... n-type ZnSSe strain canceling layer, 22 ... p
Type ZnSSe strain canceling layer

Claims (8)

[Claims] A first conductive type first clad layer; a first light guide layer on the first clad layer; an active layer on the first light guide layer; And a second conductive type second clad layer on the second light guide layer, wherein the first clad layer, the first light guide layer, and the active The layer, the second light guide layer, and the second cladding layer each include at least one or more group II elements selected from the group consisting of Zn, Be, Mg, Cd, and Hg;
a semiconductor light-emitting device comprising a group II-VI compound semiconductor comprising at least one or more group VI elements selected from the group consisting of e, S, Te and O, wherein the band of the first light guide layer is A first intermediate layer having a band gap between the gap and the band gap of the active layer, and having a refractive index between the refractive index of the first light guide layer and the refractive index of the active layer; A second light guide layer provided between the first light guide layer and the active layer, having a band gap between a band gap of the second light guide layer and a band gap of the active layer; A second intermediate layer having a refractive index between the refractive index of the guide layer and the refractive index of the active layer is provided between the second optical guide layer and the active layer. Semiconductor light emitting element . 2. The semiconductor device according to claim 1, further comprising a first strain canceling layer provided between said first intermediate layer and said active layer so as to compensate for a strain in said active layer. Semiconductor light emitting device. 3. A structure according to claim 1, wherein a second strain canceling layer is provided between said active layer and said second intermediate layer so as to compensate for distortion of said active layer. Semiconductor light emitting device. 4. The method according to claim 1, wherein the first intermediate layer is made of non-doped Zn.
2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is an Se layer or a ZnSe layer of a first conductivity type. 5. The method according to claim 1, wherein the second intermediate layer is made of non-doped Zn.
2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is a Se layer or a ZnSe layer of a second conductivity type. 6. The first light guide layer is a non-doped ZnSSe layer, a first conductivity type ZnSSe layer, a non-doped ZnMgSSe layer, or a first conductivity type ZnMgSSe.
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is a layer. 7. The second light guide layer is a non-doped ZnSSe layer, a second conductivity type ZnSSe layer, a non-doped ZnMgSSe layer, or a second conductivity type ZnMgSSe.
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is a layer. 8. The method according to claim 1, wherein the active layer is non-doped ZnCdSe.
Layer, first conductivity type ZnCdSe layer, undoped ZnC
2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is a dSSe layer or a first conductivity type ZnCdSSe layer.