JPH07142765A - Semiconductor light-emitting element and semiconductor laser and manufacture of semiconductor light emitting diode - Google Patents

Abstract

PURPOSE:To provide a semiconductor light-emitting element which ensures good reproducibility in control of doping amount of p-type impurity and good characteristics. CONSTITUTION:There is provided a semiconductor light-emitting element comprising an n-type clad layer 2 and a p-type clad layer 4 which are arranged on an InP substrate 1 and are formed of II-VI compound semiconductors and an active layer 3 which is sandwitched between the p-type and n-type clad layers to have a forbidden band narrower than that of the clad layers and emits the light when electrons and holes are injected there and forming the p-type clad layer with a compound semiconductor including Mg as the group II element and Se or combination of Se and Te as the group VI element which are respectively contained as the principal structural element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, a short wavelength semiconductor light emitting device such as a light emitting diode, a semiconductor laser and a method for manufacturing a semiconductor light emitting device.

[0002]

2. Description of the Related Art A conventional semiconductor laser using a II-VI group semiconductor is, as shown in FIG.
On the GaAs substrate 18, n-type Zn _0.9 Mg _0.1 S _0.14 S
e _0.86 clad layer 19, n-type ZnS _0.07 Se _0.93 guide layer 20, Cd _0.3 Zn _0.7 Se active layer 21, p-type ZnS
_0.07 Se _0.93 guide layer 22, p-type Zn _0.9 Mg _0.1 S _0.14
Se _0.86 clad layer 23, p-type ZnSe cap layer 24
Was grown to form a polyimide resin 25, and a gold electrode 9 was formed on the stripe-shaped hole 8 (Applied Physics Letters, Vol. 62, 2).
462 (1993) (Applied physics)
sletters vol. 62 (1993) 2
462P)).

[0003]

In the above-mentioned prior art, it is difficult to control the concentration of p-type impurities in ZnMgSSe, which is the material for the p-type and n-type cladding layers, and the composition of Mg and S is required to obtain a large band offset. However, there is a problem that it is more difficult to dope such a crystal with p-type impurities.

It is a first object of the present invention to provide a semiconductor light emitting device having good reproducibility of p-type impurity doping control and good characteristics. The second object of the present invention is p
It is an object of the present invention to provide a semiconductor laser having good reproducibility of control of the doping amount of type impurities and excellent characteristics. Third of the present invention
The purpose of is to provide a method for manufacturing such a semiconductor light emitting device.

[0005]

In order to achieve the above first object, a semiconductor light emitting device of the present invention comprises a substrate and a group II and group VI compound semiconductor disposed on the substrate. It is composed of an n-type clad layer and a p-type clad layer, and an active layer sandwiched by the n-type and p-type clad layers, having a narrower forbidden band than the clad layer, and emitting light when electrons and holes are injected. , P-type clad layer as group II element with M
g is a compound semiconductor containing Se or a combination of Se and Te as a main constituent element, respectively, as a Group VI element.

This p-type cladding layer has a general formula of Zn _x Mg _1-x Te _y Se _1-y (where x is a value in the range of 0 to 0.5 and y is in the range of 0 to 0.23). It is preferably composed of a compound semiconductor represented by

Further, the n-type cladding layer is M as a group II element.
It is preferable that g is a compound semiconductor containing Se or a combination of Se and Cd as Group VI elements as main constituent elements. Such n-type cladding layer, the general formula _{(Zn a Cd 1-a)} 1-b Mg b Se ( where, a is a value in the range from 0.2 to 1.0, b is 0.
There is a compound semiconductor represented by a value ranging from 5 to 1.0).

The design of such a semiconductor light emitting device is facilitated if the substrate on which the semiconductor layer is crystal-grown has a lattice constant of more than 5.63Å and not more than 6.10Å. As such a substrate, InP (lattice constant 5.88Å),
InAs (lattice constant 6.10Å), ZnTe (lattice constant 6.10Å) and the like can be mentioned.

In order to achieve the second object,
The semiconductor laser of the present invention is configured by the semiconductor light emitting device described in any one of the above.

Further, in order to achieve the third object, the method for manufacturing a semiconductor light emitting device of the present invention comprises forming an n-type clad layer made of a compound semiconductor of group II and group VI on a substrate, On this n-type clad layer, an active layer having a narrower bandgap than the clad layer and emitting light by injection of electrons and holes is formed.
It consists of a group VI compound semiconductor and contains Mg as a group II element.
The p-type clad layer is made of a compound semiconductor containing Se or a combination of Se and Te as a main constituent element as a group VI element. This n-type clad layer contains Mg as a group II element and S as a group VI element.
It is preferably composed of a compound semiconductor containing e or a combination of Se and Cd as main constituent elements.

[0011]

Most of II-VI group semiconductors are likely to have n-type conductivity, and a special crystal growth method is required to obtain p-type conductivity. However, it is known that among the II-VI group semiconductors, Te and Se-based materials, especially Te-based materials, tend to be p-type. Therefore, if a material containing Te or Se is used for the p-type cladding layer, p-type conductivity control becomes easy. In this case, the p-type cladding layer needs to be formed of a semiconductor containing Mg in order to obtain a sufficient electron confinement effect. At this time, if the lattice constant of the substrate is larger than that of a GaAs substrate which is normally used, that is, larger than 5.63Å, T with a large atomic radius
Since the composition with a high concentration of e and Se is lattice-matched with the substrate, p-type conductivity control becomes easier. Moreover, T
Since the work functions of the e and Se-based semiconductors are smaller than those of semiconductors using other VI group atoms, it is possible to suppress the electrical barrier between the II-VI group semiconductor and the electrode metal, which is likely to be a problem.

In the n-type cladding layer, it is preferable that n-type conductivity be easily controlled and that the active layer has a large barrier on the valence band side.
If a ZnMgCdSe-based semiconductor is used instead of the MgSeTe-based semiconductor, this requirement can be satisfied at the same time.

[0013]

[Embodiment 1] A first embodiment of the present invention will be described with reference to FIG. First, Cl-doped Mg _0.5 Zn _0.26 Cd _0.24 was formed on the InP substrate 1 by the molecular beam epitaxy method.
N-type clad layer 2 made of Se (n = 1 × 10E18)
(Thickness 1.5 μm), undoped ZnTe _0.46 Se _0.54
Active layer 3 (thickness: 0.04 μm), nitrogen-doped Z
n _0.5 Mg _0.5 Te _0.23 Se _0.77 (p = 7 × 10E17)
A p-type cladding layer 4 (thickness: 1.5 μm) and a cap layer 5 (thickness: 0.01 μm) made of nitrogen-doped ZnTe _0.46 Se _0.54 (p = 1 × 10E18) were sequentially grown. After completely stopping the molecular beams of Zn and Se, ZnTe
A Te electrode 6 having a thickness of about 0.1 μm was formed on a _0.46 Se _0.54 crystal in the same growth tank.

[0014] Next, cover the surface of the wafer by the SiO ₂ film 7, the SiO ₂ through a conventional photoresist process
A stripe-shaped hole 8 having a width of about 10 μm was formed in the film 6, and a gold electrode 9 was vapor-deposited thereon by a vacuum vapor deposition method. Further, after forming a gold electrode (not shown) also on InP on the back surface, it was cleaved to a length of about 1 mm to obtain a laser chip. The cross-sectional shape of the chip in this state is shown in FIG.

In this structure, since the interface between the Te electrode 6 and the cap layer 5 is formed in the same molecular beam epitaxy apparatus without being exposed to the outside air, there is no interface level generated by oxidation. A good ohmic electrode can be easily formed due to advantages such as having a lattice-matched cap layer containing a high concentration of p-type impurities and having the Te electrode functioning as an alloy layer.

The band structure of this structure is as shown in FIG. 2, and large band offsets of 300 meV and 550 meV can be formed for electrons and holes, respectively. The semiconductor laser of this structure continuously oscillated at room temperature with a threshold current of about 50 mA. Oscillation wavelength is about 540nm
Met.

<Second Embodiment> A second embodiment of the present invention is shown in FIG.
Will be explained. First, a Cl-doped MgZnCdSe-based superlattice (n
= 1 × 10E18), an n-type cladding layer 10 (thickness: 1.5 μm), an active layer 11 (thickness: 0.04 μm) made of an undoped MgZnTeSe-based multiple quantum well, and a nitrogen-doped ZnMgTeSe-based superlattice (p = 7 ×). 10E17)
A p-type cladding layer 12 (thickness: 1.5 μm) and a cap layer 5 (thickness: 0.01 μm) made of nitrogen-doped ZnTe _0.46 Se _0.54 (p = 1 × 10E18) were sequentially grown. Next, after completely stopping the molecular beams of Zn and Se,
ZnTe _0.46 Se _0.54 Te with a thickness of about 0.1 μm on the crystal
The electrode 6 was formed in the same growth tank.

Here, the n-type clad layer 10 is a 1 nm MgSe layer 13 and a 1 nm Zn _0.52 Cd _0.48 Se layer 14.
Are alternately laminated to form the active layer 11.
5 nm MgSe barrier layer 15 and 3 nm ZnTe _0.3
Se _0.7 well layer 16 is formed by stacking,
The p-type clad layer 12 includes a 1 nm MgSe layer 13 and a 1 n layer.
m ZnTe _0.46 Se _0.54 layer 17 is laminated.

Next, cover the surface of the wafer by the SiO ₂ film 7, the SiO ₂ through a conventional photoresist process
A stripe-shaped hole 8 having a width of about 10 μm was formed in the film, and a gold electrode 9 was vapor-deposited thereon by a vacuum vapor deposition method. Further, after forming a gold electrode (not shown) also on InP on the back surface, it was cleaved to a length of about 1 mm to obtain a laser chip. The cross-sectional shape of the chip in this state is shown in FIG.

In this structure, since the interface between the Te electrode 6 and the cap layer 5 is formed in the same molecular beam epitaxy apparatus without being exposed to the outside air, there is no interface state and high concentration. A good ohmic electrode can be easily formed because of the advantages of having a lattice-matched cap layer containing a p-type impurity and the Te electrode acting as an alloy layer.

The band structure of this structure is as shown in FIG. 4, and large band offsets of 300 meV and 550 meV can be formed for electrons and holes, respectively. The semiconductor laser of this structure continuously oscillated at room temperature with a threshold current of about 70 mA. Oscillation wavelength is about 480nm
Met.

<Embodiment 3> A third embodiment of the present invention is shown in FIG.
Will be explained. First, on the InP substrate 1, Cl-doped MgSe (n = 1 × 10 4) was formed by a molecular beam epitaxy method.
E18) n-type clad layer 26 (thickness 1.5 μm
m), Cl-doped ZnMgSeTe superlattice (n = 1 × 1)
0E18) guide layer 27 (thickness 0.25μ
m), an active layer 28 (thickness 0.04 μm) made of undoped ZnTeSe strained superlattice, nitrogen-doped ZnMgSeT
Guide layer 29 made of e superlattice (p = 7 × 10E17)
(Thickness 0.25 μm), nitrogen-doped MgSe (p = 7 ×
10E17) a p-type cladding layer 30 (thickness: 1.5
μm), nitrogen-doped ZnTe _0.46 Se _0.54 (p = 1 × 1)
0E18) cap layer 5 (thickness 0.01 μm)
Were successively grown. Further, when forming the cap layer 5 on the p-type clad layer 30, the composition was gradually changed.

The guide layers 27 and 29 are both made of ZnTe.
_0.46 Se _0.54 layer 31 (thickness 4 nm) and MgSe layer 32
(Thickness 5 nm) are laminated to form the active layer 2
8 is a ZnTe layer 34 of 4 layers (thickness 5 nm) and Z of 5 layers
The nSe layer 33 (4 nm) is formed by stacking.

Next, after processing up to the p-type clad layer 30 into a stripe shape through a normal photoresist process, MB
P-ZnTe _0.46 Se _0.54 (p = 1 × 1
0 ¹⁹ ), a contact layer 35 (thickness: 1.2 μm) is grown, and a gold electrode 9 is further deposited by a vacuum deposition method.
A gold electrode (not shown) is formed also on the back surface of InP,
The laser chip was cleaved to a length of about 1 mm. The cross-sectional shape of the chip in this state is shown in FIG.

In this structure, the contact layer 35 made of ZnTe _0.46 Se _{0.54 having} a high impurity concentration is used.
And the cap layer 5 form a good ohmic contact with each other, but the contact layer 35 of ZnTe _0.46 Se _0.54 and MgS
At the contact interface of the p-type clad layer 30 of e, the impurity concentration of MgSe is relatively low, the surface of the p-type clad layer 30 is once exposed to the outside air and oxidized, and the band offset of the interface is large. For this reason, it has a large interfacial resistance, and almost no current flows through this surface. That is, the current confinement is performed in a self-aligned manner by providing the layer for improving the contact resistance only in the stripe portion.

The band structure of this structure is as shown in FIG. 7, which is 700 meV for electrons and holes, respectively.
And a large band offset of 400 meV can be formed. The semiconductor laser of this structure continuously oscillated at room temperature with a threshold current of about 50 mA. Oscillation wavelength is about 490n
It was m.

<Embodiment 4> The above embodiments relate to a semiconductor laser using a II-VI group semiconductor, but a similar structure can be applied to a light emitting diode.
Such an example will be described as the fourth embodiment of the present invention with reference to FIG. First, Cl-doped MgSe (n = 1 × 10E1) was formed on the InP substrate 1 by the molecular beam epitaxy method.
8) n-type cladding layer 26 (thickness: 1.5 μm),
Active layer 35 made of undoped ZnTe _0.46 Se _0.54
(0.4 μm), nitrogen-doped MgSe (p = 7 × 10E
17) p-type clad layer 30 (thickness: 1.5 μ)
m), nitrogen-doped ZnTe _0.46 Se _0.54 (p = 1 × 10
A cap layer 5 (thickness 0.01 μm) made of E18) was sequentially grown. After completely stopping the molecular beams of Zn and Se, a Te electrode 6 having a thickness of about 0.1 μm was formed on the ZnTe _0.46 Se _0.54 crystal in the same growth tank.

Next, a gold electrode 9 is deposited on the surface of this wafer by a vacuum deposition method, and then the diameter from the gold electrode 9 to the cap layer 5 is about 100 μm by an ordinary photoresist process.
Holes 36 are provided. Further, a gold electrode (not shown) was formed also on the back surface of InP. The cross-sectional shape in this state is shown in FIG.

In this structure, since the interface between the Te electrode 6 and the cap layer 5 is formed in the same molecular beam epitaxy apparatus without being exposed to the outside air, there is no interface level generated by oxidation. A good ohmic electrode can be easily formed due to advantages such as having a lattice-matched cap layer containing a high concentration of p-type impurities and having the Te layer functioning as an alloy layer. The oscillation wavelength of the light emitting diode of this structure was about 540 nm.

<Embodiment 5> As a fifth embodiment of the present invention, an example of a semiconductor laser formed on an InAs substrate will be described with reference to FIG. Cl-doped MgTe _0.4 Se _0.6 (n = 1 ×) was formed on the InAs substrate 37 by the molecular beam epitaxy method.
10E18) n-type clad layer 38 (thickness: 1.5
μm), an active layer 39 (thickness 0.04 μm) made of undoped ZnTe _0.9 Se _0.1 , and nitrogen-doped MgTe _0.4 S.
e _0.6 (p = 7 × 10E17) p-type cladding layer 40 (thickness: 1.5 μm), nitrogen-doped ZnTe _0.9 Se
Cap layer 41 made of _0.1 (p = 1 × 10E18)
(Thickness 0.01 μm) were sequentially grown. After completely stopping the molecular beams of Zn and Se, a Te electrode 6 having a thickness of about 0.1 μm was formed on the ZnTe _0.9 Se _0.1 crystal in the same growth tank.

Next, cover the surface of the wafer by the SiO ₂ film 7, the SiO ₂ through a conventional photoresist process
A stripe-shaped hole 8 having a width of about 10 μm was formed in the film 7, and a gold electrode 9 was vapor-deposited thereon by a vacuum vapor deposition method. Further, after forming a gold electrode (not shown) also on the InAs on the back surface, it was cleaved into a laser chip having a length of about 1 mm. The cross-sectional shape of the chip in this state is shown in FIG.

In this structure, since the interface between the Te electrode 6 and the cap layer 41 is formed in the same molecular beam epitaxy apparatus without being exposed to the outside air, there is no interface level generated by oxidation. A good ohmic electrode can be easily formed because of the advantages such as having a lattice-matched cap layer containing a high concentration of impurities and the Te layer acting as an alloy layer. The semiconductor laser of this structure continuously oscillated at room temperature with a threshold current of about 50 mA. The oscillation wavelength was about 570 nm.

In the above embodiments, examples using InP and InAs as the substrate are shown, but the lattice constant is
Greater than the lattice constant of GaAs (5.63Å), ZnT
In the case of a substrate having a lattice constant of e (6.10 Å) or less, the similar improvement effect was observed as compared with the device using the conventional GaAs substrate.

[0034]

According to the present invention, since a compound semiconductor which can easily obtain a low-resistance p-type semiconductor is used as the p-type cladding layer, the conductivity can be easily controlled and a sufficiently large confinement effect on electrons and holes can be obtained. A semiconductor light emitting device that maintains the above was obtained. Also, the reproducibility of the doping amount of the p-type cladding layer was easy.

[Brief description of drawings]

FIG. 1 is a structural diagram of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a band structure diagram of the semiconductor laser according to the first embodiment of the present invention.

FIG. 3 is a structural diagram of a semiconductor laser according to a second embodiment of the present invention.

FIG. 4 is a band structure diagram of a semiconductor laser according to a second embodiment of the present invention.

FIG. 5 is a structural diagram of a conventional semiconductor laser.

FIG. 6 is a structural diagram of a semiconductor laser according to a third embodiment of the present invention.

FIG. 7 is a band structure diagram of a semiconductor laser according to a third embodiment of the present invention.

FIG. 8 is a structural diagram of a light emitting diode according to a fourth embodiment of the present invention.

FIG. 9 is a structural diagram of a semiconductor laser according to a fifth embodiment of the present invention.

[Explanation of symbols]

1 ... InP substrate 2, 10, 26, 38 ... N-type clad layer 3, 11, 28, 39 ... Active layer 4, 12, 30, 40 ... P-type clad layer 5, 41 ... Cap layer 6 ... Te electrode 7 ... SiO ₂ film 8 ... Striped holes 9 ... Gold electrode 13 ... MgSe layer 14 ... Zn _0.52 Cd _0.48 Se layer 15 ... MgSe barrier layer 16 ... ZnTe _0.3 Se _0.7 well layer 17 ... ZnTe _0.46 Se _0.54 18 ... GaAs substrate 19 ... n-type Zn _0.9 Mg _0.1 S _0.14 Se _0.86 clad layer 20 ... n-type ZnS _0.07 Se _0.93 guide layer 21 ... Cd _0.3 Zn _0.7 Se active layer 22 ... p-type ZnS _0.07 Se _0.93 guide layer 23 ... p-type Zn _0.9 Mg _0.1 S _0.14 Se _0.86 cladding layer 24 ... p-type ZnSe cap layer 25 ... polyimide resin 27, 29 ... guide layer 31 ... ZnTe _0.46 Se _0.54 layer 32 ... MgSe layer 33 ... Zn e layer 34 ... ZnTe layer 35 ... contact layer 36 ... holes 37 ... InAs substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Oya 1-280, Higashi Koikekubo, Kokubunji City, Tokyo Metropolitan Institute of Hitachi, Ltd. (72) Masato Ueda 1-280, Higashi Koikekubo, Kokubunji, Tokyo Hitachi Ltd. Central Research Center

Claims (9)

[Claims] 1. A substrate and a group II and a layer disposed on the substrate.
N-type cladding layer and p made of Group VI compound semiconductor
Between the n-type cladding layer and the n-type and p-type cladding layers,
In a semiconductor light emitting device having a narrower band gap than the clad layer and having an active layer that emits light when electrons and holes are injected, the p-type clad layer has Mg as a group II element and a VI group element. A semiconductor light emitting device comprising a compound semiconductor containing Se or a combination of Se and Te as main constituent elements. 2. The semiconductor light emitting device according to claim 1, wherein
The p-type cladding layer has the general formula Zn _x Mg _1-x Te _y Se _1-y (where x is a value in the range of 0 to 0.5 and y is a value in the range of 0 to 0.23). A semiconductor light emitting device comprising a compound semiconductor represented by. 3. The semiconductor light emitting device according to claim 1 or 2, wherein the substrate has a lattice constant of more than 5.63Å and 6.10Å or less. 4. The semiconductor light emitting device according to claim 1, wherein the n-type cladding layer is mainly composed of Mg as a group II element, Se as a group VI element, or a combination of Se and Cd. A semiconductor light-emitting device comprising a compound semiconductor containing a constituent element. 5. The semiconductor light emitting device according to claim 4,
The n-type cladding layer has the general formula (Zn _a Cd _1-a ) _1-b Mg _b Se (where a is a value in the range of 0.2 to 1.0 and b is 0.
A semiconductor light-emitting device comprising a compound semiconductor represented by the formula (5 to 1.0). 6. A semiconductor laser comprising the semiconductor light emitting device according to claim 1. 7. A first step of forming an n-type clad layer made of a II-group and VI-group compound semiconductor on a substrate, wherein a band gap narrower than that of the clad layer is formed on the n-type clad layer. And a second step of forming an active layer that emits light by injecting holes, comprising a Group II and Group VI compound semiconductor on the active layer, wherein Mg is a Group II element and Se is a Group VI element. Alternatively, the method for manufacturing a semiconductor light emitting device includes a third step of forming a p-type clad layer made of a compound semiconductor containing a combination of Se and Te as main constituent elements, respectively. 8. The method for manufacturing a semiconductor light emitting device according to claim 7, wherein the n-type clad layer comprises Mg as a group II element.
Is a compound semiconductor containing Se or a combination of Se and Cd as a main constituent element, respectively, as a Group VI element. 9. The method for manufacturing a semiconductor light emitting device according to claim 7, wherein a cap layer and an electrode of a desired material are further formed on the p-type cladding layer after the third step. The method of manufacturing a semiconductor light emitting device, characterized in that the cap layer and the electrode of the desired material are continuously formed in the same growth chamber by the molecular beam epitaxy method.