JP2000031592A - Semiconductor light emitting device - Google Patents

Abstract

(57) [PROBLEMS] To use an II-VI group compound semiconductor capable of reducing the oscillation threshold current density while keeping the operating voltage low, and improving the element life and reliability. Provided are a semiconductor light-emitting element and a semiconductor light-emitting element using a II-VI group compound semiconductor, which can improve element life and reliability by optimizing a structure. SOLUTION: ZnCdSe / ZnSSe / ZnMgS
In the gain guided semiconductor laser having the Se SCH structure, the effective band gap energy of the active layer is 2.
In the case of 49 eV or more, the stripe width is 10 μm or more and 50 μm or more, the resonator length is 800 μm or more, and the effective band gap energy of the active layer is 2.47 eV.
If not more than 3 μm and 10 μm
Hereinafter, the resonator length is set to be 500 μm or more and 1000 μm or less.

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 using a II-VI compound semiconductor, such as a semiconductor laser or a light emitting diode.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for semiconductor light emitting elements such as semiconductor lasers and light emitting diodes capable of emitting blue or green light in order to increase the recording / reproducing density and resolution of optical disks or magneto-optical disks. Research is being actively conducted to achieve this.

[0003] Materials used for manufacturing such a semiconductor light emitting device capable of emitting blue or green light include Zn and C.
Group II elements such as d, Mg, Hg, Be and S, Se, T
Group II-VI compound semiconductors comprising Group VI elements such as e and O are promising. In particular, quaternary mixed ZnMgS
Se has excellent crystallinity and can be easily grown on a GaAs substrate. For example, a cladding layer or an optical waveguide layer when a semiconductor laser capable of emitting blue light is manufactured using this GaAs substrate. (For example, Electronics Letters 28 (1992) 1798).

Conventionally, a semiconductor light emitting device using this II-VI group compound semiconductor, in particular, a ZnMgSSe
A semiconductor light emitting device using a layer is obtained by forming an n-type ZnMgSSe clad layer, an active layer, a p-type ZnMgSSe clad layer, a p-type ZnSe contact layer, etc. on an n-type GaAs substrate via a buffer layer by a molecular beam epitaxy (MBE) method. It is common to manufacture by sequentially growing and then forming a p-side electrode on the p-type ZnSe contact layer and forming an n-side electrode on the back surface of the n-type GaAs substrate. However, in such a semiconductor light emitting device, it is difficult to increase the carrier concentration of the p-type ZnSe contact layer, and the like.
It was difficult to make an ohmic contact of the p-side electrode on the contact layer.

In order to solve this problem, a p-type ZnSe / ZnTe superlattice layer is grown on a p-type ZnSe contact layer, and a p-type ZnTe contact layer having a high carrier concentration can be easily obtained thereon. A layer is grown, and a p-side electrode, in particular, a pd / Pt / Au p
A technique for improving ohmic contact characteristics by forming side electrodes has been proposed. And ZnCdSe
Is an active layer, ZnSSe is an optical waveguide layer, and ZnCdSe / ZnSSe / ZnMgS is a cladding layer.
Se SCH (Separate Confinement Heterostructur
e) In a gain-guided semiconductor laser having a structure,
It adopts a side-electrode contact structure and has achieved continuous oscillation at room temperature (for example, Jpn. J. Appl. Phy.
s. 33 (1994) L938 and Electron. Lett. 32 No. 6 (1996)
552).

[0006]

However, it has been confirmed that, in a semiconductor laser using the above-described p-side electrode contact structure, the operating voltage increases with the passage of time when current is applied. Therefore, in recent semiconductor lasers, the II that constitutes the p-side electrode contact structure is used.
-By optimizing the impurity concentration and the thickness of the group VI compound semiconductor layer, and suppressing the increase in the operating voltage during energization,
For example, operation is possible while maintaining a low operating voltage of 5 V or less, and a longer life of the p-side electrode is being realized.

[0007] However, according to the findings of the present inventors,
As described above, in the semiconductor laser in which the p-side electrode contact structure is optimized, a low voltage operation is possible, but a new problem that the oscillation threshold current is increased is confirmed. This increase in the oscillation threshold current promotes deterioration of the active layer and the like, and as a result, limits the life of the device and prevents improvement in reliability. In order to solve this problem, it is necessary to consider the oscillation threshold current from the viewpoint of the oscillation threshold current density and optimize the structure of the semiconductor laser so that the oscillation threshold current density is reduced.

Accordingly, an object of the present invention is to reduce the oscillation threshold current density while keeping the operating voltage low, and to realize a semiconductor using a II-VI group compound semiconductor which can achieve a long life. It is to provide a light emitting element.

Another object of the present invention is to realize a longer life by optimizing the structure.
An object of the present invention is to provide a semiconductor light emitting device using a group VI compound semiconductor.

[0010]

In order to achieve the above object, the present inventors have made intensive studies and have found that ZnCdSe / ZnS
In a gain-guided semiconductor laser having a Se / ZnMgSSe SCH structure, operating characteristics were measured with various structural parameters varied. The oscillation threshold current density depends on the stripe width and the resonator length. It has been found that there is an optimum range for each of the stripe width and the resonator length at which the density decreases. The present inventor further conducted experiments and studies, and found that ZnCdS
In a gain-guided semiconductor laser having an e / ZnSSe / ZnMgSSe SCH structure, it has been found that the optimum range of the stripe width and the resonator length for improving the device life differs depending on the effective band gap energy of the active layer. .

The outline of the experiment conducted by the present inventors will be described below. That is, ZnCdSe / ZnSSe /
In a gain guided semiconductor laser with a ZnMgSSe SCH structure, samples were prepared in which the stripe length was varied while the resonator length was fixed, and the oscillation threshold current density J _th and oscillation threshold voltage V _th were determined to be stripe width dependent. Examined.
FIG. 1 is a graph showing the results. In the sample used for this measurement, the active layer was formed of Zn _0.74 Cd _0.26 S
The active layer had an effective band gap energy of 2.49 eV. The resonator length is 10
It was set to 00 μm.

FIG. 1 shows that the oscillation threshold current density J _th decreases as the stripe width increases. When the stripe width is 20 μm or less, the degree of change in the oscillation threshold current density J _th with respect to the change in the stripe width is large. However, when the stripe width is 20 μm or more, the oscillation threshold current density J _{th with} respect to the change in the stripe width. Becomes small, and the oscillation threshold current density J _th becomes substantially constant. When the stripe width is 50 μm or more, the oscillation threshold current density J _th is almost constant at a low value of about 300 A / cm ² , but the oscillation threshold current becomes large and laser oscillation becomes difficult. Inconvenience occurs. FIG. 1 also shows that the oscillation threshold voltage _Vth decreases as the stripe width increases. In this case, however, the change is more significant as the oscillation threshold current density _Jth changes with respect to the change in the stripe width. Did not.
From these results, for example, in order to realize an oscillation threshold voltage V _th of 5 V or less and an oscillation threshold current density J _th of 400 A / cm ² or less and obtain a semiconductor laser capable of easily oscillating,
It can be seen that the stripe width may be set to 20 μm or more and 50 μm or less.

The sample used for measuring the oscillation threshold current density J _th and the oscillation threshold voltage V _th , that is, the effective band gap energy of the active layer is 2.49 e.
V, the resonator length was set to 1000 μm, the sample manufactured by changing the stripe width was operated at a constant optical output (1 mW), and the device life at that time was measured. Examined. FIG.
It is a graph which shows the result. In FIG. 2,
The dependence of the operating current density J _{op on} the stripe width is also shown. The operating current density J _op indicates a value (initial value) at the start of energization. The operating current density J _op substantially corresponds to the oscillation threshold current density J _th of each sample.

FIG. 2 shows that the oscillation threshold voltage V _th and the oscillation threshold current density J _th are both low and the stripe width is determined so that a semiconductor laser capable of easily oscillating can be obtained, that is, the stripe width is 20 μm. It can be seen that when the thickness is not less than 50 μm, the life of the element is improved. Therefore, the oscillation threshold voltage V _th and the oscillation threshold current density J
_It can be seen that in order to obtain a semiconductor laser having both a low _th and a long life, the stripe width may be set to 20 μm or more and 50 μm or less. It is also possible to optimize the stripe width only from the viewpoint of extending the life of the semiconductor laser. In this case, for example, in order to obtain a semiconductor laser having a long lifetime of about 200 hours or more, the stripe width should be 10 μm or more and 50 μm or less.
When the stripe width is 10 μm, the oscillation threshold voltage V _th is about 5 V, and the oscillation threshold current density J _th is about 600 A /
cm ² .

Next, ZnCdSe / ZnSSe / ZnM
In a gSSe SCH structure gain-guided semiconductor laser, samples were prepared in which the stripe width was fixed and the resonator length was varied, and these samples were subjected to a constant optical output (1 m).
W), the device life at that time was measured, and the resonator length dependence of the device life was examined. FIG.
Is a graph showing the results. FIG. 3 also shows the dependence of the operating current density J _{op on} the resonator length. The operating current density J _op indicates a value (initial value) at the start of energization. The operating current density J _op substantially corresponds to the oscillation threshold current density J _th of each sample. In addition,
In the sample used for this measurement, the active layer was Zn _0.74 C
constituted by d _0.26 Se layer, and the effective band gap energy of the active layer and 2.49EV. The stripe width was 20 μm.

FIG. 3 shows that the longer the resonator length, the lower the operating current density J _op (therefore, the oscillation threshold current J _th ), and the longer the element life. In addition, for example, in order to obtain a semiconductor laser having a long life of about 200 hours or more, the resonator length should be about 800 μm or more.

As described above, ZnCdSe / Zn with the effective band gap energy of the active layer being 2.49 eV.
In the gain-guided semiconductor laser having the SSe / ZnMgSSe SCH structure, it is found that optimizing the stripe width and the resonator length so that the oscillation threshold current density is low is effective for improving the element life. .

The above description is based on ZnCdSe / ZnSSe / Zn
This is a case where the effective bandgap energy of the active layer is set to 2.49 eV in the gain-guided semiconductor laser having the MgSSe SCH structure. When the voltage was 2.49 eV or more, the oscillation threshold voltage, the oscillation threshold current density, and the device life exhibited the same stripe width dependence and resonator length dependence as described above.

On the other hand, ZnCdSe / ZnSSe / ZnM
In a semiconductor laser having a gSSe SCH structure, when the effective band gap energy of the active layer is 2.47 eV or less, the dependence of the oscillation threshold voltage, the oscillation threshold current density, and the device life on the stripe width and the resonator length are reduced. The effective band gap energy of the active layer is 2.
This is different from the case of 49 eV or more.

That is, ZnCdSe / ZnSSe / Z
In the gain-guided semiconductor laser having the nMgSSe SCH structure, the active layer is formed of a Zn _0.69 Cd _0.31 Se layer, and the effective band gap energy of the active layer is set to 2.
Samples of 45 eV were prepared by changing the stripe width and the resonator length variously, and the same experiment as above was carried out. The following results were obtained.

FIG. 4 shows ZnCdSe / ZnS in which the effective band gap energy of the active layer is 2.45 eV.
FIG. 5 is a graph showing the stripe width dependence of the oscillation threshold current density and the oscillation threshold voltage in the gain-guided semiconductor laser having the Se / ZnMgSSe SCH structure. FIG. 5 shows the case where the effective band gap energy of the active layer is 2.45 eV. Certain ZnCdSe / ZnSSe / ZnMgSSe SC
6 is a graph showing the stripe width dependence of the device life and operating current density in a gain guided semiconductor laser having an H structure. In these cases, the resonator length of the sample used for the measurement was 800 μm. FIG. 6 shows ZnCd in which the effective band gap energy of the active layer is 2.45 eV.
4 is a graph showing the resonator length dependence of device life and operating current density in a gain-guided semiconductor laser having a Se / ZnSSe / ZnMgSSe SCH structure. In this case, the stripe width of the sample used for the measurement was 5 μm.

FIG. 4 shows that the oscillation threshold current density and the oscillation threshold voltage when the effective band gap energy of the active layer is 2.45 eV are obtained when the effective band gap energy of the active layer is 2.49 eV. It can be seen that the same stripe width dependence is exhibited.

On the other hand, from FIGS. 5 and 6, when the effective bandgap energy of the active layer is 2.45 eV,
The optimum range of the stripe width and the resonator length that can improve the device life is different from the optimum range of the stripe width and the resonator length when the band gap energy of the active layer is 2.49 eV. When the effective band gap energy of the layer is 2.45 eV, the band gap energy of the active layer is 2.49 eV.
It can be seen that making the stripe width narrower is more effective for improving the device life than the case where Specifically, FIG.
As shown in the figure, when the stripe width is 10 μm or less, the element life is significantly improved as compared with the case where the stripe width is 20 μm or more.

Here, the present inventor considers that the oscillation threshold current is desirably 50 mA or less in order to realize the improvement of the device life in this semiconductor laser.
This is based on findings obtained based on experiments and studies conducted by the present inventors so far. From the viewpoint of the oscillation threshold current, the result shown in FIG. 4 requires a stripe width of 10 μm to realize an oscillation threshold current of 50 mA or less.
It is understood that the following should be performed. Further, from FIG. 5, when the stripe width is determined so that the oscillation threshold current is 50 mA or less as described above, that is, when the stripe width is 10
When the thickness is not more than μm, a device life of 50 hours or more is obtained. Although not shown in FIG. 5, according to the study of the present inventor, even when the stripe width is 3 μm, a device life of about 50 hours can be obtained. From the above, it is understood that the stripe width should be 3 μm or more and 10 μm or less in order to obtain a semiconductor laser having an element lifetime of 50 hours or more and an oscillation threshold current of 50 mA or less. FIG. 6 shows that it is desirable to set the cavity length to be 500 μm or more and 1000 μm or less in order to extend the life of the semiconductor laser.

Thus, ZnCdSe / ZnSSe /
In the gain guided semiconductor laser having the ZnMgSSe SCH structure, the case where the effective band gap energy of the active layer is 2.49 eV or more and the case where the effective band gap energy of the active layer is 2.47 eV or less. It is considered that the reason why the optimum stripe width and resonator length for improving the life of the element are different is that the state of deterioration related to the determination of the life of the element is different. That is, the effective band gap energy of the active layer is 2.49 eV.
In the case of the above, the carrier confinement between the active layer and the cladding layer is weak, and it is considered that the deterioration of the cladding layer is a main cause for determining the device life. In this case, the stripe width is, for example, 10 μm or more, Preferably 20 μm or more and 50
It is considered preferable to have a wide stripe structure of μm or less. On the other hand, when the effective bandgap energy of the active layer is 2.47 eV or less, carrier confinement between the active layer and the cladding layer is strong, and deterioration of the active layer is the main factor that determines the device life. In this case, the stripe width is, for example, 10 μm or less, preferably 3 μm.
It is considered that a narrow stripe structure of not less than μm and not more than 10 μm is desirable.

The present invention has been made based on the results of the above-mentioned experiments conducted by the present inventors.

In order to achieve the above object, a first aspect of the present invention provides a substrate, a first cladding layer of a first conductivity type on the substrate, an active layer on the first cladding layer, A second cladding layer of a second conductivity type on the layer, wherein the first cladding layer, the active layer and the second cladding layer are made of Zn, Cd, M
II-VI consisting of one or more group II elements selected from the group consisting of g, Hg and Be and one or more group VI elements selected from the group consisting of S, Se, Te and O
In a gain-guided semiconductor light emitting device composed of a group III compound semiconductor and having an effective band gap energy of an active layer of 2.49 eV or more, the stripe width is 10 μm.
m or more and 50 μm or less, and the resonator length is 800 μm or more.

According to a second aspect of the present invention, there is provided a substrate, a first conductive type first cladding layer on the substrate, an active layer on the first cladding layer, and a second conductive type on the active layer. The second cladding layer, the first cladding layer, the active layer, and the second cladding layer are formed of one or more group II elements selected from the group consisting of Zn, Hg, Cd, Mg, and Be, and S, Se, The active layer has an effective bandgap energy of 2.47 e, which is made of a II-VI group compound semiconductor comprising at least one group VI element selected from the group consisting of Te and O.
In a gain-guided semiconductor light emitting device having a V or less, the stripe width is 3 μm or more and 10 μm or less, and the cavity length is 500 μm or more and 1000 μm or less.

In the first and second aspects of the invention, the first cladding layer and the second cladding layer are
Typically, it is composed of ZnMgSSe, and the active layer is typically composed of ZnCdSe. Further, a first optical waveguide layer and a second optical waveguide made of II-VI group compound semiconductor are provided between the first clad layer and the active layer and between the active layer and the second clad layer, respectively. It may have a wave layer. In this case, the first optical waveguide layer and the second optical waveguide layer are typically made of ZnSSe.

In the first and second aspects of the present invention, a second conductive type contact layer may be provided on the second cladding layer. In this case, typically the first
Is an n-type cladding layer, the second cladding layer is a p-type cladding layer, and the contact layer is a p-type contact layer. Further, in this case, the p-type contact layer is preferably, for example, a p-type ZnSS on the p-type cladding layer.
e, a second p-type contact layer made of p-type ZnSe on the first p-type contact layer, and one or more p-type layers on the second p-type contact layer. A superlattice layer composed of a p-type ZnSe layer and one or more p-type ZnTe layers;
e of a third p-type contact layer. This p
In the type contact layer, from the viewpoint of reducing the oscillation threshold voltage of the semiconductor light emitting device and enabling low-voltage operation,
The thickness of the p-type contact layer is, for example, 1 atomic layer or more and 1
The thickness is selected to be less than 0 nm, preferably, for example, 1 atomic layer or more and 5 nm or less.
P-type ZnS selected to be 5 μm or more and constituting the first p-type contact layer, the second p-type contact layer, and the superlattice layer.
The impurity concentration of the e-layer is selected from, for example, 1 × 10 ¹⁸ / cm ³ or more and 2 × 10 ¹⁸ / cm ³ or less in N _A -N _D (N _A : acceptor concentration, N _D : donor concentration).

According to the first aspect of the present invention configured as described above, in the gain-guided semiconductor light emitting device in which the effective band gap energy of the active layer is equal to or greater than 2.49 eV, the stripe width is reduced. By setting the oscillation threshold voltage and the oscillation threshold current density to 10 μm or more and 50 μm or less and the resonator length to 800 μm or more, the stripe width and the resonator length are optimized so that the device life is improved. Have been. Thus, the oscillation threshold current density can be reduced while the operating voltage is kept low, and the life and reliability of the semiconductor light emitting device can be improved.

According to the second aspect of the present invention, in a gain-guided semiconductor light emitting device in which the effective band gap energy of the active layer is 2.47 eV or less, the stripe width is 3 μm or more and 10 μm or less, and , Resonator length is 5
The stripe width and the resonator length are each optimized so that the device life is improved by setting the thickness to be not less than 00 μm and not more than 1000 μm. Thereby, the life and reliability of the semiconductor light emitting device can be improved.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described. FIG. 7 is a sectional view of the semiconductor laser according to the first embodiment. This semiconductor laser is made of ZnCdS
e as an active layer, ZnSSe as an optical waveguide layer, and ZnMgSSe as a cladding layer. ZnCdSe / ZnSSe / ZnMg
It has an SSe SCH structure and is of a gain waveguide type. In the first embodiment, the ZnCdS
A case where the effective band gap energy of the active layer is 2.49 eV or more in a gain-guided semiconductor laser having an e / ZnSSe / ZnMgSSe SCH structure will be described.

As shown in FIG. 7, in this semiconductor laser, an n-type impurity doped with, for example, Si is used.
N-type GaAs buffer layer 2, n-type
-Type ZnSe buffer layer 3, n-type ZnSSe buffer layer 4, n-type ZnMgSSe cladding layer 5, n-type ZnSSe
An optical waveguide layer 6, for example, an active layer 7 having an SQW structure using an undoped Zn _1-x Cd _x Se layer as a quantum well layer, p-type ZnS
Se optical waveguide layer 8, p-type ZnMgSSe clad layer 9, p
-Type ZnSSe cap layer 10, p-type ZnSe contact layer 11, one or more p-type ZnSe layers and one or more p-type Z
p-type ZnSe / ZnTe in which nTe layers are alternately stacked
A superlattice layer 12 and a p-type ZnTe contact layer 13 are sequentially stacked.

The n-type GaAs buffer layer 2 is doped with, for example, Si as an n-type impurity. The n-type ZnSe buffer layer 3, the n-type ZnSSe buffer layer 4, and the n-type ZnMgS
The Se cladding layer 5 and the n-type ZnSSe optical waveguide layer 6 are each doped with, for example, Cl as an n-type impurity, and the p-type ZnSSe optical waveguide layer 8, the p-type ZnMgSSe cladding layer 9, the p-type ZnSSe cap layer 10, the p-type Zn
The Se contact layer 11, the p-type ZnSe layer and the p-type ZnTe layer of the p-type ZnSe / ZnTe superlattice layer 12, and the p-type ZnTe contact layer 13 are each doped with, for example, N as a p-type impurity.

An upper layer portion of the p-type ZnSSe cap layer 10,
p-type ZnSe contact layer 11, p-type ZnSe / ZnT
e superlattice layer 12 and p-type ZnTe contact layer 13
Have a stripe shape extending in one direction. An insulating layer 14 made of, for example, a polyimide film is provided on the p-type ZnSSe cap layer 10 in a portion other than the stripe portion, thereby forming a current confinement structure. As a material of the insulating layer 14, for example, Al ₂ O ₃ may be used instead of polyimide.

The insulating layer 14 and the stripe-shaped p
For example, Pd / Pt is formed on the type ZnTe contact layer 13.
A p-side electrode 15 having an / Au structure 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 1, an n-side electrode 16 such as an In electrode is provided in ohmic contact.

In the semiconductor laser according to the first embodiment, a pair of resonator end faces perpendicular to the length direction of the resonator are provided.
Each has an end face coating. In this case, of the pair of resonator end faces, the reflectance of the front end face from which laser light is extracted is 60%, and the reflectance of the rear end face from which laser light is not extracted is 96%.

In the semiconductor laser according to the first embodiment, the Cd composition ratio x in the Zn _{1 -x} Cd _x Se layer constituting the active layer 7 is selected to be 0.26 or less, and the effective Band gap energy is 2.49e
V or more. Here, the effective bandgap energy of the active layer 7 refers to the Zn that constitutes the active layer 7.
_{This is} the sum of the band gap energy in the bulk state of the _1-x Cd _x Se layer and the shift amount due to the quantum effect. In this case, specifically, Zn constituting the active layer 7
The Cd composition ratio x in the _1-x Cd _x Se layer is, for example, 0.2
6. Zn _1-x Cd having a Cd composition ratio x = 0.26
The effective band gap energy of the active layer 7 composed of the _x Se layer is 2.49 eV, and the emission wavelength of this semiconductor laser is 497 nm.

In the first embodiment, the p-type ZnSe layer constituting the p-type ZnSSe cap layer 10, the p-type ZnSe contact layer 11, and the p-type ZnSe / ZnTe superlattice layer 12 has an impurity concentration of N _A − N _D (N _A:
(Acceptor concentration, N _D : donor concentration)
¹⁸ / cm ^{3 to} 2 × 10 ¹⁸ / cm ³ , and p-type Zn
The impurity concentration of the Te contact layer 13 is, for example, about 1 × 10 ¹⁹ / cm ^{3 in} N _A -N _D. Also, p-type ZnSS
The thickness of the e-cap layer 10 is selected to be 1.5 μm or more,
The thickness of the type ZnTe contact layer 13 is one atomic layer (approximately 0.
28 nm) to less than 10 nm, preferably 1 atomic layer or more and 5
nm or less. In this semiconductor laser, the p-type ZnSSe cap layer 10, the p-type ZnSe contact layer 11, and the p-type ZnS
Since the e / ZnTe superlattice layer 12 and the p-type ZnTe contact layer 13 are configured as described above, the p-side electrode contact structure is optimized with respect to reduction of the oscillation threshold voltage. The operation is realized, and the increase in the operating voltage during energization is suppressed.

Here, as an example of the thickness of each semiconductor layer constituting the semiconductor laser, the thickness of the n-type GaAs buffer layer 2 is 0.5 μm, the thickness of the n-type ZnSe buffer layer 3 is 10 nm, The thickness of the n-type ZnSSe buffer layer 4 is 300 nm, the thickness of the n-type ZnMgSSe cladding layer 5 is 1 μm, and the thickness of the n-type ZnSSe optical waveguide layer 6 is 100 n.
m, the thickness of the active layer 7 is 3 to 4 nm, the thickness of the p-type ZnSSe optical waveguide layer 8 is 100 nm, the thickness of the p-type ZnMgSSe cladding layer 9 is 1 μm, and the p-type ZnSSe cap layer 10.
Has a thickness of 1.5 to 2 μm and a p-type ZnSe contact layer 1
1 has a thickness of 150 nm and a p-type ZnTe contact layer 13
Has a thickness of 3 nm.

In the first embodiment, the active layer 7
ZnCdSe / ZnSSe / ZnMgSSe SC whose effective band gap energy is 2.49 eV
In the gain-guided semiconductor laser having the H structure, the upper portion of the p-type ZnSSe cap layer 10 and the p-type ZnSe contact layer 11 are formed so that the oscillation threshold voltage and the oscillation threshold current density are reduced and the device life is improved. , P-type ZnSe
The width of the stripe portion composed of the / ZnTe superlattice layer 12 and the p-type ZnTe contact layer 13, that is, the stripe width and the resonator length are optimized based on the experimental results. Specifically, in the same semiconductor laser as described above, samples were prepared in which the stripe width and the cavity length were variously changed, and from these samples, the dependence of the oscillation threshold voltage, the oscillation threshold current density, and the device life on the stripe width were determined. And resonator length dependence, and based on these results,
The stripe width and the resonator length are respectively optimized so as to obtain desired oscillation threshold voltage, oscillation threshold current density and element life. In this case, for example, the stripe width is 10 μm so that a device life of 200 hours or more is obtained.
The cavity length is selected to be at least 800 μm. More preferably, for example, when the operating voltage is 5 V or less, the oscillation threshold current density is 400 A / cm ² or less,
The stripe width is selected to be 20 μm or more and 50 μm or less, and the resonator length is set to 80 μm or more so as to obtain a device life of 0 hour or more.
It is selected to be 0 μm or more. For example, the stripe width is 20 μm, and the cavity length is 1000 μm. However, in the above description, the element life corresponds to the life when the optical output is operated at a constant light output of 1 mW.

The semiconductor laser according to the first embodiment configured as described above is manufactured as follows.

First, the n-type GaAs substrate 1 is mounted on a substrate holder in a vacuum vessel evacuated to an ultra-high vacuum in an MBE apparatus for growing a group III-V compound semiconductor, not shown.
Next, after heating the n-type GaAs substrate 1 to a predetermined growth temperature, n-type GaAs substrate 1
A type GaAs 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 n-type GaAs
The growth of the buffer layer 2 is performed by forming the n-type GaAs
The heating may be performed after heating to a temperature of about 80 ° C. and thermal etching the surface to remove the surface oxide film and the like and clean the surface.

Next, the n-type GaAs substrate 1 on which the n-type GaAs buffer layer 2 has been grown as described above is transferred to the above-mentioned MBE apparatus for growing a III-V compound semiconductor through a vacuum transfer path (not shown). From the substrate to an MBE apparatus for growing II-VI group compound semiconductors shown in FIG. Then, in the MBE apparatus shown in FIG. 8, each II-VI group compound semiconductor layer forming the laser structure is grown. In this case, the surface of the n-type GaAs buffer layer 2 is kept clean since it is not exposed to the air during its transfer to the MBE apparatus shown in FIG. 8 after its growth.

As shown in FIG. 8, in this MBE apparatus, a substrate holder 22 is provided in a vacuum vessel 21 evacuated to an ultra-high vacuum by an ultra-high vacuum exhaust device (not shown). Is held. A plurality of molecular beam sources (Knudsen cells) 23 are mounted in the vacuum vessel 21 so as to face the substrate holder 22. In this case, as the molecular beam source 23, Z
n, Se, Mg, ZnS, Te, Cd and ZnCl ₂
Molecular beam sources such as are provided. In the vacuum chamber 21, a plasma cell 24 by electron cyclotron resonance (ECR) or radio frequency (RF) is further provided with a substrate holder 22.
It is attached to face.

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 chamber 2 of the MBE apparatus shown in FIG.
The n-type GaAs substrate 1 on which the n-type GaAs buffer layer 2 has been grown is mounted on the substrate holder 22 in 1. Next, the n-type GaAs substrate 1 is set at a predetermined growth temperature, for example, about 250 ° C., and growth by the MBE method is started.
That is, on the n-type GaAs buffer layer 2, n-type ZnS
e-buffer layer 3, n-type ZnSSe buffer layer 4, n-type Z
nMgSSe cladding layer 5, n-type ZnSSe optical waveguide layer 6, active layer 7, p-type ZnSSe optical waveguide layer 8, p-type ZnM
gSSe clad layer 9, p-type ZnSSe cap layer 1
0, p-type ZnSe contact layer 11, p-type ZnSe / Z
nTe superlattice layer 12 and p-type ZnTe contact layer 1
3 is grown sequentially.

N-type ZnSe buffer layer 3, n-type ZnSS
e buffer layer 4, n-type ZnMgSSe clad layer 5, n
The doping of the type ZnSSe optical waveguide layer 6 with Cl as an n-type impurity is performed using, for example, ZnCl ₂ as a dopant. The p-type ZnSSe optical waveguide layer 8 and the p-type ZnM
gSSe clad layer 9, p-type ZnSSe cap layer 1
0, p-type ZnSe contact layer 11, p-type ZnSe / Z
nTe superlattice layer 12 and p-type ZnTe contact layer 1
The doping of N as a p-type impurity of No. 3 was generated by converting N ₂ gas introduced from a gas introduction pipe (not shown) into plasma in the plasma cell 24 of the MBE apparatus shown in FIG. This is performed by irradiating the substrate surface with N ₂ plasma.

Next, a stripe-shaped resist pattern (not shown) having a predetermined width extending in one direction is formed on the p-type ZnTe contact layer 13 by lithography. P-type ZnSSe cap layer 10 by etching
Is etched to an intermediate depth in the thickness direction. Thereby, the upper layer portion of the p-type ZnSSe cap layer 10 and the p-type ZnSSe
The nSe contact layer 11, the p-type ZnSe / ZnTe superlattice layer 12, and the p-type ZnTe contact layer 13 are patterned into a stripe shape having a predetermined width.

Next, a polyimide film is deposited on the entire surface while the resist pattern used for the etching is left as it is. Thereafter, the resist pattern is removed together with the polyimide film thereon (lift-off). Thereby, p-type Zn patterned in a stripe shape
An insulating layer 14 made of polyimide is formed on both sides of the upper layer portion of the SSe cap layer 10, the p-type ZnSe contact layer 11, the p-type ZnSe / ZnTe superlattice layer 12, and the p-type ZnTe contact layer 13.

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 contact layer 13 and the insulating layer 14 on both sides thereof by, for example, a vacuum deposition method to form Pd / Pt / Au. A p-side electrode 15 having a structure is formed. Thereafter, a heat treatment is performed as needed to bring the p-side electrode 15 into ohmic contact with the p-type ZnTe contact layer 13. On the other hand, an n-side electrode 16 such as an In electrode 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 is formed as described above is cleaved into a bar shape so as to have a predetermined resonator length to form both resonator end faces.
After applying the end face coating, the bar is cleaved into chips. The laser chip thus obtained is mounted on a heat sink, packaged,
The target semiconductor laser is manufactured.

According to the first embodiment configured as described above, ZnCdSe / ZnSS in which the effective band gap energy of the active layer 7 is 2.49 eV or more.
In a gain guided semiconductor laser having an e / ZnMgSSe SCH structure, a stripe width is 10 μm or more and 50 μm or more.
And the resonator length is 800 μm or more, the oscillation threshold voltage and the oscillation threshold current density are reduced, and the stripe width and the resonator length are optimized so that the element life is improved. ing. As a result, the oscillation threshold current density can be reduced while the operating voltage is kept low, and the life and reliability of the semiconductor laser can be improved.

Next, a second embodiment of the present invention will be described. This semiconductor laser uses ZnCdSe / ZnSSe / ZnMgSSe with an active layer of ZnCdSe, an optical waveguide layer of ZnSSe, and a cladding layer of ZnMgSSe.
It has an SCH structure and is of a gain waveguide type. In the second embodiment, the ZnCdSe / Zn
A case in which the effective band gap energy of the active layer is 2.47 eV or less in a gain-guided semiconductor laser having the SSe / ZnMgSSe SCH structure will be described.

In the semiconductor laser according to the second embodiment, the Cd composition ratio x in the Zn _{1 -x} Cd _x Se layer constituting the active layer 7 is selected to be 0.28 or more, and the effective layer 7 Bandgap energy is 2.47e
V or less. In this case, specifically, the active layer 7
Composition ratio x in Zn _1-x Cd _x Se layer constituting
Is, for example, 0.31. This Cd composition ratio x = 0.31
The effective bandgap energy of the active layer 7 composed of the Zn _1-x Cd _x Se layer is 2.45 eV. At this time, the emission wavelength of this semiconductor laser is 506 nm.

In the second embodiment, the active layer 7
ZnCdSe / ZnSSe / ZnMgSSe SC whose effective band gap energy is 2.45 eV
In a gain-guided semiconductor laser having an H structure, a stripe width and a resonator length are optimized based on experimental results so that an oscillation threshold current is reduced and a device life is improved. Specifically, in a semiconductor laser similar to that described above, samples with variously changed stripe widths and resonator lengths were prepared, and from these samples, oscillation threshold voltage, oscillation threshold current density, oscillation threshold current, and device lifetime were measured. The stripe width dependency and the resonator length dependency are examined, and based on these results, the stripe width and the resonator length are optimized so as to obtain desired oscillation threshold current and device life. In this case, for example, the oscillation threshold current is 50 mA.
Hereinafter, the stripe width is selected from 3 μm to 10 μm, and the resonator length is selected from 500 μm to 1000 μm so that the device life of 50 hours or more can be obtained. For example, the stripe width is 5 μm, and the resonator length is 800 μm. However, in the above description, the element life corresponds to the life when the optical output is operated at a constant light output of 1 mW.

The configuration other than that of the semiconductor laser according to the second embodiment is the same as that of the semiconductor laser according to the above-described first embodiment, and a description thereof will be omitted.

The method of manufacturing the semiconductor laser according to the second embodiment is the same as the method of manufacturing the semiconductor laser according to the first embodiment, and a description thereof will not be repeated.

According to the second embodiment configured as described above, the effective band gap energy of the active layer is ZnCdSe / ZnSSe of 2.47 eV or less.
In a gain-guided semiconductor laser having a / ZnMgSSe SCH structure, the lasing width is 3 μm to 10 μm and the resonator length is 500 μm to 1000 μm, so that the oscillation threshold current is reduced and the element life is improved. As described above, the stripe width and the resonator length are respectively optimized. Thereby, the life and reliability of the semiconductor laser can be improved.

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. Specifically, the active layer 7 described in the first and second embodiments
The composition of the Zn _{1 -z} Cd _z Se layer constituting
The effective band gap energy of the active layer 7 is 2.4
In the case of 9 eV or more, it is a typical value in the case of 2.47 eV or less, and a Zn _1-z Cd _z Se layer having a composition different from the exemplified one may be used as necessary.

Also, for example, instead of the active layer 7 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 optical waveguide layers in the first and second embodiments may be undoped. Further, for example, in the above-described first and second embodiments, the n-type ZnSSe buffer layer 4 is used.
May be omitted.

In the above-described first and second embodiments, the growth of the II-VI compound semiconductor layer is performed by MBE.
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.

Furthermore, 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.

[0066]

As described above, according to the first aspect of the present invention, in the gain-guided semiconductor light emitting device in which the effective band gap energy of the active layer is 2.49 eV or more, the stripe width is reduced. Is 10 μm or more and 50 μm or less and the resonator length is 800 μm or more, the oscillation threshold current density can be reduced while the operating voltage is kept low, and the life and reliability of the semiconductor light emitting element are improved. Can be achieved.

According to the second aspect of the present invention, in a gain-guided semiconductor light emitting device in which the effective band gap energy of the active layer is 2.47 eV or less, the stripe width is 3 μm or more and 10 μm or less, and , Resonator length is 5
When the thickness is from 00 μm to 1000 μm, the life and reliability of the semiconductor light emitting device can be improved.

[Brief description of the drawings]

FIG. 1 shows ZnCdSe / ZnSSe / Zn in which the effective band gap energy of the active layer is 2.49 eV.
5 is a graph showing the stripe width dependence of the oscillation threshold current density and the oscillation threshold voltage in the gain-guided semiconductor laser having the MgSSe SCH structure.

FIG. 2 shows ZnCdSe / ZnSSe / Zn in which the effective band gap energy of the active layer is 2.49 eV.
4 is a graph showing the stripe width dependence of device life and operating current density in a gain-guided semiconductor laser having an MgSSe SCH structure.

FIG. 3 shows ZnCdSe / ZnSSe / Zn in which the effective band gap energy of the active layer is 2.49 eV.
4 is a graph showing the resonator length dependence of device life and operating current density in a gain-guided semiconductor laser having a MgSSe SCH structure.

FIG. 4 shows ZnCdSe / ZnSSe / Zn in which the effective band gap energy of the active layer is 2.45 eV.
5 is a graph showing the stripe width dependence of the oscillation threshold current density and the oscillation threshold voltage in the gain-guided semiconductor laser having the MgSSe SCH structure.

FIG. 5 shows ZnCdSe / ZnSSe / Zn in which the effective band gap energy of the active layer is 2.45 eV.
4 is a graph showing the stripe width dependence of device life and operating current density in a gain-guided semiconductor laser having an MgSSe SCH structure.

FIG. 6 shows ZnCdSe / ZnSSe / Zn in which the effective band gap energy of the active layer is 2.45 eV.
4 is a graph showing the resonator length dependence of device life and operating current density in a gain-guided semiconductor laser having a MgSSe SCH structure.

FIG. 7 shows II-VI according to the first embodiment of the present invention.
1 is a cross-sectional view of a semiconductor laser using a group III compound semiconductor.

FIG. 8 shows II-VI according to the first embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating an example of a configuration of an MBE apparatus used for manufacturing a semiconductor laser using a group III compound semiconductor.

[Explanation of symbols]

1 ... n-type GaAs substrate, 5 ... n-type ZnMgSS
e-clad layer, 6... n-type ZnSSe optical waveguide layer, 7.
..Active layer, 8... P-type ZnSSe optical waveguide layer, 9.
-P-type ZnMgSSe cladding layer, 10 ... p-type Zn
SSe cap layer, 11 ... p-type ZnSe contact layer, 12 ... p-type ZnSe / ZnTe superlattice layer, 13
... p-type ZnTe contact layer, 14 ... insulating layer,
15 ... p-side electrode, 16 ... n-side electrode

Continued on the front page (72) Inventor Satoru Kijima 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term within Sony Corporation (reference) 5F041 CA05 CA14 CA41 CA43 CA44 CA99 CB36 5F073 AA45 AA61 CA22 CB10 DA30

Claims (18)

[Claims] 1. A substrate, a first cladding layer of a first conductivity type on the substrate, an active layer on the first cladding layer, and a second cladding of a second conductivity type on the active layer The first cladding layer, the active layer and the second cladding layer each include one or more group II elements selected from the group consisting of Zn, Cd, Mg, Hg and Be, and S, Se, T
The active layer is formed of a II-VI compound semiconductor comprising at least one group VI element selected from the group consisting of e and O, and the effective band gap energy of the active layer is 2.
A gain-guided semiconductor light emitting device having a frequency of 49 eV or more, wherein the stripe width is 10 μm or more and 50 μm or less, and the cavity length is 800 μm or more. 2. The semiconductor light emitting device according to claim 1, wherein said first cladding layer and said second cladding layer are made of ZnMgSSe. 3. The semiconductor light emitting device according to claim 1, wherein said active layer is made of ZnCdSe. 4. Between the first cladding layer and the active layer and between the active layer and the second cladding layer,
2. The semiconductor light emitting device according to claim 1, further comprising a first optical waveguide layer and a second optical waveguide layer each made of the II-VI compound semiconductor. 5. The optical waveguide according to claim 4, wherein the first optical waveguide layer and the second optical waveguide layer are made of ZnSSe.
The semiconductor light-emitting device according to claim 1. 6. The method according to claim 1, wherein the second clad layer is provided on the second clad layer.
A second conductivity type contact layer made of a group VI compound semiconductor, wherein the first cladding layer is an n-type cladding layer, the second cladding layer is a p-type cladding layer, and the contact layer The semiconductor light emitting device according to claim 1, wherein is a p-type contact layer. 7. The p-type contact layer comprises: a first p-type contact layer made of p-type ZnSSe on the p-type cladding layer; and a p-type ZnSe on the first p-type contact layer.
A second p-type contact layer, a superlattice layer composed of one or more p-type ZnSe layers and one or more p-type ZnTe layers on the second p-type contact layer, 7. The semiconductor light-emitting device according to claim 6, comprising a third p-type contact layer made of p-type ZnTe. 8. The thickness of the third p-type contact layer is 5
The semiconductor light-emitting device according to claim 7, wherein the diameter is not more than nm. 9. The semiconductor light emitting device according to claim 7, wherein said first p-type contact layer has a thickness of 1.5 μm or more. 10. A substrate, a first cladding layer of a first conductivity type on the substrate, an active layer on the first cladding layer, and a second cladding of a second conductivity type on the active layer. The first cladding layer, the active layer and the second cladding layer are formed of one or more group II elements selected from the group consisting of Zn, Hg, Cd, Mg and Be, and S, Se, T
The active layer is formed of a II-VI compound semiconductor comprising at least one group VI element selected from the group consisting of e and O, and the effective band gap energy of the active layer is 2.
A gain-guided semiconductor light-emitting device having a voltage of 47 eV or less, wherein the stripe width is 3 μm or more and 10 μm or less, and the cavity length is 500 μm or more and 1000 μm or less. 11. The first cladding layer and the second cladding layer.
11. The semiconductor light emitting device according to claim 10, wherein said cladding layer is made of ZnMgSSe. 12. The semiconductor light emitting device according to claim 10, wherein said active layer is made of ZnCdSe. 13. A first semiconductor made of the II-VI group compound semiconductor, between the first cladding layer and the active layer and between the active layer and the second cladding layer, respectively. The semiconductor light emitting device according to claim 10, further comprising an optical waveguide layer and a second optical waveguide layer. 14. The semiconductor light emitting device according to claim 13, wherein said first optical waveguide layer and said second optical waveguide layer are made of ZnSSe. 15. The method according to claim 15, further comprising:
A contact layer of a second conductivity type made of a Group VI compound semiconductor, wherein the first cladding layer is an n-type cladding layer, the second cladding layer is a p-type cladding layer, The semiconductor light emitting device according to claim 10, wherein the layer is a p-type contact layer. 16. The p-type contact layer comprises: a first p-type contact layer made of p-type ZnSSe on the p-type clad layer; and a p-type ZnS on the first p-type contact layer.
e, a second superlattice layer composed of at least one p-type ZnSe layer and one or more p-type ZnTe layers on the second p-type contact layer, and the superlattice layer 16. The semiconductor light emitting device according to claim 15, comprising a third p-type contact layer made of p-type ZnTe. 17. The semiconductor light emitting device according to claim 16, wherein said third p-type contact layer has a thickness of 5 nm or less. 18. The semiconductor light emitting device according to claim 16, wherein said first p-type contact layer has a thickness of 1.5 μm or more.