JPH0697598A - Semiconductor light-emitting device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a semiconductor laser emitting green or blue light capable of continuous oscillation at room temperature. [Structure] For example, between p-GaAs and p-ZnSe,
A superlattice composed of GaAs and ZnSe is introduced. Alternatively, In between the p-GaAs and p-ZnSe
An intermediate layer of _y (Ga _1-x Al _x ) _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is introduced. [Effects] According to the present invention, since the series resistance can be greatly reduced, room temperature continuous oscillation of a semiconductor laser emitting green or blue light becomes possible. This makes it possible to provide a semiconductor laser device that can be applied to a light source for a high density optical disk, an alternative light source for green or blue LEDs, a light source for a high-sensitivity laser printer, a light source for a display, or the like.

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 laser emitting green or blue light.

[0002]

2. Description of the Related Art Conventionally, semiconductor lasers are In _x Ga _{1 -x} P
_y As _1-y / GaAs, Ga _x Al _1-x As / GaAs and In _x Al _1-x P / In _y Ga _1-y P (0 <x, y <1)
It is composed of a double heterojunction structure made of a III-V group compound semiconductor material, and the oscillation wavelength thereof is limited to the infrared to red visible region.

On the other hand, if a semiconductor laser having an oscillation wavelength in the short-wavelength visible region or ultraviolet region of yellow-orange, green, and blue is put to practical use, there are many advantages. For example, a blue semiconductor laser can increase the recording density when it is used for an optical disk, and a semiconductor laser from ultraviolet to green enables high sensitivity of an optical printer. Further, since the plastic optical fiber, which is attracting attention for short-distance communication, has a strong loss in the infrared region and the low-loss region exists near 550 nm, the green semiconductor laser is also attracting attention as a light source for short-distance communication. ing. Further, the ultraviolet semiconductor laser may be applied as a phosphor excitation light source, a process technology using a photosensitive material, or a research light source. As described above, the visible light semiconductor laser having a shorter wavelength than the 0.5 μm band has many advantages, and its practical application is strongly desired.

In a carrier injection type semiconductor laser having a II-VI group compound semiconductor in the active layer, Z is formed on GaAs.
The structure that directly forms nSe is applied physics
Letters 59 (No. 11) pp. 1272-1274 (1991).

Further, in an avalanche photodiode (APD) using a III-V group compound semiconductor, in order to prevent carrier pile-up, an InP / InGaAs superlattice in which the band gap is gradually changed between InP and InGaAs. The structure for providing is described in Applied Physics Letters, Vol. 45 (No. 11), pages 1193 to 1195 (1984).
Year).

Similarly, in order to prevent pile-up in APD, an intermediate layer of In _1-x Ga _x As _y P _1-y having a forbidden band width intermediate between the two is provided between InP and InGaAs. Structure is Applied Physics Letters No. 5
Volume 1 (No. 18) pp. 1454-1456 (1987)
Has been reported in.

[0007]

In the injection type II-VI group semiconductor laser in which p-ZnSe or p-ZnSSe is directly formed on the p-type GaAs substrate, the series resistance becomes extremely high. This is because the band offset ΔE _V on the valence band side between GaAs / ZnSe or between GaAs / ZnSSe is large.

An object of the present invention is to solve the above problems and provide a II-VI group semiconductor laser capable of continuous operation at room temperature.

[0009]

In order to achieve the above object, at least a p-type conduction type III-V group compound semiconductor 1 and a p-type conduction type II-VI group compound semiconductor 2 are provided,
In a structure in which the semiconductor 1 is in contact with the p-type electrode, a superlattice is provided between the semiconductor 1 and the semiconductor 2 so that the effective band gap gradually changes between the semiconductor 1 and the semiconductor 2. We devised a semiconductor light emitting device.

[0012] Further, the present invention aims to use GaA as the first semiconductor.
s, the second semiconductor is ZnS _x Se _1-x (0 ≦ x ≦ 1), and the superlattice is GaAs and ZnS _x Se _1-x (0 ≦ _x ).
It can be effectively achieved by configuring x ≦ 1).

Further, as another structure for achieving the above object, at least a p-type conduction type III-V group compound semiconductor 1 and a p-type conduction type II-VI group compound semiconductor 2 are provided,
In the structure in which the semiconductor 1 is in contact with the p-type electrode, the forbidden band width E _{g1 of the} semiconductor 1 and the forbidden band width E _{g2 of the} semiconductor 2 are
A semiconductor light-emitting device comprising one or more semiconductor intermediate layers having a forbidden band width E _g3 (that is, E _g1 <E _g3 <E _g2 ) between the semiconductor 1 and the semiconductor 2. Devised.

[0012] Further, for the purpose of the present invention, the semiconductor intermediate layer is made of In
_This can be effectively achieved by a semiconductor light emitting device characterized in that _y (Ga _1-x Al _x ) _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1).

[0013]

FIG. 3 is a schematic sectional view of a conventional II-VI group semiconductor laser. In this structure, the p-type electrode 39 of Au is directly provided on the p-ZnSe 37. However, ZnSe
Since the forbidden band width is as large as 2.67 eV, ohmic contact is not obtained and the contact resistance is extremely high. Therefore, the amount of heat generated by current injection is large and continuous oscillation at room temperature is difficult.

On the other hand, FIG. 4 is a schematic sectional view of a conventional II-VI group semiconductor laser using a p-type GaAs substrate.
In this structure, the p-type GaAs substrate 1 and the p-type electrode 11
Because of the provision of, an ohmic contact is obtained. However, between the p-GaAs buffer layer 2 and the p-ZnSe layer 4, the band discontinuity value Delta] E _V of the valence band side of about 1eV
Therefore, the injection of holes is hindered. That is,
Since an extremely large resistance exists between the p-GaAs buffer layer 2 and the p-ZnSe layer 4, the amount of heat generated by the current injection is large, as in the case of FIG. 3, and room temperature continuous oscillation is difficult.

In the structure of the present invention, as shown in FIG. 1, in order to reduce the resistance between the p-GaAs buffer layer 2 and the p-ZnSe layer 4, a superlattice 3 is introduced between both layers. ing. As shown in the energy band diagram of FIG. 2, this superlattice is formed by alternately forming p-GaAs 21 and p-ZnSe 22 for 8 periods. The film thickness of each layer is p-Ga
From the side in contact with the As buffer layer 2 (left side in the figure), p-
It is determined that the forbidden band width gradually changes toward the side in contact with ZnSe4 (right side in the figure). In this example, the thickness of one cycle was fixed at 45Å, and the thickness was changed at a pitch of 5Å between 5Å and 40Å. Therefore, this superlattice is
And ZnSe can be regarded as a pseudo mixed crystal. In the structure of the present invention, holes can be smoothly injected from the p-GaAs buffer layer 2 to the p-ZnSe layer 4,
Low series resistance enables continuous oscillation at room temperature.

FIG. 5 shows the p-GaAs buffer layer 2
And the p-ZnSe layer 4 between the p-GaInP layer 51 and the p-ZnSe layer 4.
In this example, two intermediate layers of the AlInP layer 52 are provided.
Here, the mixed crystal ratio is set so that both GaInP and AlInP are lattice-matched with GaAs. In this case, Ga
Band discontinuity value Δ on the valence band side of the As / GaInP interface
E _V is 0.30 eV, ΔE of GaInP / AlInP interface
_V is 0.32 eV, and Δ of AlInP / ZnSe interface
E _V can be estimated to be 0.38 eV. Thus, in the conventional structure (FIG. 4), a single interface of GaAs / ZnSe had a ΔE _V of 1.0 eV, whereas in this structure, the band discontinuity values were dispersed at three interfaces. There is. Therefore, from the p-GaAs buffer layer 2 to p-ZnS
Since holes are easily injected into the e-layer 4, series resistance is low, and continuous oscillation at room temperature is possible.

[0017]

EXAMPLE 1 A first example of the present invention will be described with reference to FIGS. 1 and 2. First, a method for manufacturing the semiconductor laser of the present invention will be described.

On the substrate 1 of p-GaAs (100) plane,
P-GaAs buffer layer 2 (acceptor concentration N _A = 1 × 10 ¹⁸ [/ cm ³ ], by organometallic molecular beam epitaxy),
Thickness 2.0 μm) and p-GaAs / p-ZnSe8
Superlattice 3 consisting period, p-ZnSe layer 4 (N _A = 5 ×
10 ¹⁷ [/ cm ³ ] and a thickness of 0.04 μm) are sequentially formed. Here, the structure of the superlattice is as shown in FIG.
The acceptor concentration N _A of p-GaAs 21 is 1 × 10.
¹⁸ [/ cm ³ ], N _{A of} p-ZnSe22 is 5 × 10 ¹⁷ [/
cm ³ ]. The thickness of each layer is measured from the side in contact with the p-GaAs buffer layer 2 (left side in the figure) to p-ZnSe.
It is decided that the forbidden band width gradually changes to the side that contacts 4 (right side of the figure). In this example, the thickness of one cycle is 4
The thickness was fixed to 5Å, and the thickness was changed at a pitch of 5Å between 5Å and 40Å. That is, in FIG. 2, ZnSe / Ga
From the left side, the thickness of As is (5Å / 40Å), (10Å /
35Å), (15Å / 30Å), (20Å / 25Å),
(25Å / 20Å), (30Å / 15Å), (35Å /
10Å) and (40Å / 5Å).

Subsequently, p-ZnS _0.07 Se _0.93 layer 5 (N
_A = 5 × 10 ¹⁷ [/ cm ³ ], thickness 2.0 μm), Cd _0.2 Zn
_0.8 Se active layer 6 (undoped, thickness 100Å), n−
ZnS _0.07 Se _0.93 layer 7 (donor concentration N _D = 1 × 10 ¹⁸
[/ Cm ³ ], thickness 2.0 μm), n-ZnSe layer 8 (donor concentration N _D = 1 × 10 ¹⁸ [/ cm ³ ], thickness 0.04 μm)
m) are sequentially formed. As the dopant, p
Nitrogen was used for the mold layer and chlorine was used for the n-type layer. Next, SiO
_{The second} insulating film 9 is provided by the CVD method, and a stripe having a width of 15 μm is formed by the usual etching method. Finally, the n-type electrode 10 and the p-type electrode 11 are formed by the vapor deposition method to manufacture the semiconductor laser device of the embodiment shown in FIG.

In the device of the above embodiment, continuous oscillation at 40 ° C. is possible and an optical output of 10 mW is obtained. In the past, only pulse operation was possible, and the maximum operating temperature was limited to a low temperature of about 5 ° C.

Second Embodiment A second embodiment of the present invention will be described with reference to FIG. First,
A method of manufacturing the semiconductor laser of the present invention will be described.

On the substrate 1 of p-GaAs (100) plane,
P-GaAs buffer layer 2 (acceptor concentration N _A = 1 × 10 ¹⁸ [/ cm ³ ], by organometallic molecular beam epitaxy),
Thickness 2.0 μm) and p-Ga _0.5 In _0.5 P layer 51
^{_{(N A = 1 × 10 18}} [/ cm 3], 0.1μm thickness), p-
Al _0.5 In _0.5 P layer _{52 (N A = 1 × 10} 18 [/ c
m ³ ], and a thickness of 0.1 μm) are sequentially formed. Then p-
ZnSe layer _{4 (N A = 5 × 10} 17 [/ cm 3], thickness 0.0
_{4μm), p-ZnS 0.07 Se} 0.93 layer 5 (N _A = 5 × 10
¹⁷ [/ cm ³ ], thickness 2.0 μm), Cd _0.2 Zn _0.8 Se active layer 6 (undoped, thickness 100 Å), n-ZnS _0.07
Se _0.93 layer 7 (donor concentration N _D = 1 × 10 ¹⁸ [/ cm ³ ],
Thickness 2.0 μm), n-ZnSe layer 8 (donor concentration N _D =
1 × 10 ¹⁸ [/ cm ³ ] and a thickness of 0.04 μm) are sequentially formed. Next, an insulating film 9 of SiO ₂ is provided by a CVD method, and a stripe having a width of 15 μm is formed by a usual etching method. Finally, the n-type electrode 10 and the p-type electrode 1 are formed by using the vapor deposition method.
By forming No. 1, the semiconductor laser device of the embodiment shown in FIG. 5 is manufactured.

In the device of the above embodiment, continuous oscillation at 30 ° C. is possible and an optical output of 10 mW is obtained.

The present invention is also effective for structures other than those shown in the embodiments. For example, in addition to GaInP and AlInP which are the intermediate layers shown in the second embodiment, In _y (Ga
A quaternary compound of _1-x Al _x ) _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is also applicable. Further, it is not always necessary to perform lattice matching with the GaAs substrate, and a strain system may be used. Further, a structure in which the mixed crystal ratio is changed to graded in the thickness direction is also effective. Furthermore, a structure combining the first and second embodiments, for example, in the second embodiment, GaInP /
A superlattice composed of GaInP and AlInP can also be used at the AlInP interface.

The present invention is not limited to the laser structure shown in the embodiments, but various semiconductor lasers such as distributed feedback lasers, Bragg reflection lasers, wavelength tunable lasers, lasers with external resonators, and surface emitting lasers. It is also applicable to lasers and the like.

Furthermore, the present invention is not limited to semiconductor lasers, but can be applied to various semiconductor devices that require current injection, such as light emitting diodes (LEDs), optical modulators, and optical switches.

[0027]

According to the present invention, since the series resistance can be greatly reduced, room temperature continuous oscillation of a semiconductor laser emitting green or blue light becomes possible. This makes it possible to provide a semiconductor laser device that can be applied to a light source for a high density optical disk, an alternative light source for green or blue LEDs, a light source for a high-sensitivity laser printer, a light source for a display, or the like.

[Brief description of drawings]

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

FIG. 2 is an energy band diagram of the superlattice in FIG.

FIG. 3 is a cross-sectional view of a conventional laser.

FIG. 4 is a cross-sectional view of a conventional laser.

FIG. 5 is a sectional view of a semiconductor laser according to an embodiment of the present invention.

[Explanation of symbols]

1 ... p-GaAs substrate, 2 ... p-GaAs buffer layer,
3 ... GaAs / ZnSe superlattice, 4,37 ... p-ZnS
e, 5, 36 ... p-ZnSSe cladding layer, 6, 35 ...
CdZnSe active layer, 7,34 ... n-ZnSSe cladding layer, 8,33 ... n-ZnSe, 9,38 ... Insulating film, 1
0,40 ... n electrode, 11,39 ... p electrode, 21 ... pG
aAs, 22 ... p-ZnSe, 31 ... n-GaAs substrate, 32 ... n-GaAs buffer layer, 51 ... p-GaI
nP, 52 ... n-AlInP.

Claims (4)

[Claims] 1. A structure comprising at least a p-type conduction type III-V group compound semiconductor 1 and a p-type conduction type II-VI group compound semiconductor 2, the structure being effective when the semiconductor 1 is in contact with a p-type electrode. 2. A semiconductor light emitting device, wherein a superlattice is provided between the semiconductor 1 and the semiconductor 2 so that the forbidden band width gradually changes between the semiconductor 1 and the semiconductor 2. 2. The first semiconductor is GaAs, the second semiconductor is ZnS _x Se _1-x (0 ≦ x ≦ 1), and the superlattice is GaAs and ZnS _x Se _1-x (0 ≦ x). The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is constituted by ≦ 1). 3. A structure comprising at least a p-type conduction type III-V group compound semiconductor 1 and a p-type conduction type II-VI group compound semiconductor 2, wherein the semiconductor 1 is in contact with a p-type electrode. A semiconductor intermediate layer having a forbidden band width E _g3 (E _g1 <E _g3 <E _g2 ) between the forbidden band width E _g1 of the semiconductor 1 and the forbidden band width E _g2 of the semiconductor 2 is provided between the semiconductor 1 and the semiconductor 2. A semiconductor light-emitting device, characterized in that one or more layers are provided between. 4. The semiconductor intermediate layer comprises In _y (Ga _{1 -x} A
4. The semiconductor light emitting device according to claim 3, wherein l _x ) _1-y P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1).