JPH0964469A - Semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element whose controllability with reference to a structure is excellent and which comprises a p-type contact layer whose resistance is lower than that in conventional cases. SOLUTION: A contact structure 9 is formed on an isolated light confinement quantum well structure 11 which is formed on a GaAs substrate 2 and which is composed of a group II-VI compound in such a way that it contains at least three layers of ZnSe1-x Tex layers (where 0<=x<=1) whose conductivity is of a p-type and whose composition in the respective layers is different. Thereby, a p-type contact structure whose controllability with reference to a structure is excellent as compared with that in conventional cases and whose resistance is low is obtained. As a result, a low threshold voltage is realized, and it is possible to obtain a semiconductor light-emitting element whose characteristic is good as compared with that in conventional cases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a p-type contact structure for II-VI compound semiconductor lasers.

[0002]

2. Description of the Related Art As a key device for the next-generation high-density information processing technology, II-VI group compound semiconductors capable of shortening the wavelength of laser have attracted attention.

II conventionally produced on a GaAs substrate
As a p-type contact structure of a semiconductor light emitting device made of a —VI compound, as shown in FIG.
CH) single quantum well (SQW) structure 11 on top of p-type Zn
Se _1-x Te _x (0 <x <1) 73, for example, SCH-S
Alternating p-type ZnSe and p-type ZnTe on the QW structure 11 and gradually changing the mutual layer thickness (Y. Fan, et.al .; Appli.
ed Physics Letters (1992) 3160.)
Of the p-type ZnT
A contact structure in which the e contact layer 74 is laminated is known.

[0004]

According to the above-mentioned conventional technique, there are the following four problems.

The first is the SC as shown in FIG.
On the H-SQW structure, simply p-type ZnSe _1-x Te _x (0 <
It is difficult to relax the band offset of the valence band of 1.1 eV between the p-type ZnTe contact layer and the SCH-SQW structure with the structure in which only x <1) is stacked,
It has been difficult to reduce the operating voltage of the laser.

Second, when the contact structure shown in FIG. 14 is manufactured by alternately stacking p-type ZnSe and p-type ZnTe on the SCH-SQW structure, for example, ZnSe and ZnTe are alternately stacked. It was necessary to control the layer thickness of each of the layers accurately, and it was difficult to produce a layer having good characteristics.

Thirdly, the contact structure shown in FIG. 14 is not lattice-matched to the GaAs substrate, a structure having a layer thickness of 300 Å or more cannot be coherently grown on the GaAs substrate, and a contact structure having good crystallinity is obtained. It was difficult to make.

Fourthly, the structure shown in FIG.
There is a problem that the voltage drop between Te and ZnSe is large, and as a result, the contact resistance is large and the current-voltage characteristics of the light emitting element are deteriorated.

Therefore, the present invention has an object of obtaining a p-type contact structure having a resistance lower than that of the prior art and allowing ohmic contact with an electrode metal, thereby obtaining a semiconductor light emitting device having a low resistance.

[0010]

The present invention is based on p-type ZnTe.
Between the contact layer and the SCH-SQW structure, at least three layers of ZnSe _1-x Te having p-type conductivity are provided.
By growing the crystal of _x (0 ≦ x ≦ 1), the p-type Z
The band offset of the valence band between the nTe contact layer and the SCH-SQW structure was effectively alleviated, the operating voltage of the laser was lowered, and the layer thickness of the p-type contact structure was easily controlled.

Further, ZnS _y Te _1-y (0 <y <is lattice-matched to the GaAs substrate as shown in FIG.
1) or p-type ZnSe and ZnT having a large lattice constant
and p-type (ZnSe) _i (ZnTe) _j (ZnS) _k (i,
By using a superlattice such as j and k are natural numbers, Ga
A p-type contact structure, which is lattice-matched with the As substrate and has no crystal defects, was produced.

Further, in order to reduce a large voltage drop between ZnTe and ZnSe, a p-type contact layer for ZnSe is replaced by a ZnSe _1-x Te _x mixed crystal, and a p with a smaller band offset in the valence band is used. Type Zn _1-x Cd _x
S _y Se _1-y mixed crystal (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) or p-type (ZnSe) _i (CdSe) _j (ZnS) _k (ZnSe) _i (CdSe) _j (ZnS) _k ( i, j, k
Is a natural number), and a p-type contact layer having no crystal defects, which is lattice-matched to the GaAs substrate, was produced.

By the above technique, a p-type contact structure having a carrier density of about 10 ¹⁸ cm ^-3 and having a resistance lower than that of the prior art, which enables ohmic contact with an electrode metal, is obtained. I was able to get

Stacking faults caused by the Zn _1-x Cd _x Se mixed crystal having a wurtzite structure are CdSe and ZnSe.
Can be avoided by growing a few atomic layers each.

[0015]

The present invention is applicable to the p-type ZnTe contact layer and the SCH.
Since at least three layers of ZnSe _1-x Te _x (0 ≦ x ≦ 1) having p-type conductivity are used between the -SQW structure, the layer thickness is controlled better than before. A p-type contact structure with good characteristics can be obtained. As a result, a light emitting element having better characteristics than conventional ones can be obtained.

Furthermore, the lattice constant is
Of ZnSyTe1−y (0 <y <1) or lattice constant
Large p-type ZnSe and ZnTe as well as small lattice constant
P-type (ZnS
e)_i(ZnTe)_j(ZnS) _k(I, j, k are natural
Number) etc.
A p-type contact structure that is child-matched and has no crystal defects is obtained.
It is. As a result, a light emitting device with better characteristics than before can be obtained.
Can be

Further, the band offset of the valence band with respect to ZnSe is smaller than that of the p-type ZnSe _1-x Te _x mixed crystal,
And p-type Zn _1-x Cd _x S _y lattice-matched with the GaAs substrate
Se _{1 -y} mixed crystal (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) or p-type (Zn _1-x Cd _x Se) _i (ZnS _y Se _1-y ) _j (i and j are natural numbers) superlattice Therefore, it is possible to obtain a p-type contact structure having less crystal defects and lower resistance than the conventional one. As a result, a light emitting element having better characteristics than conventional ones can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor light emitting device of the present invention and a method for manufacturing the same will be described with reference to the drawings.

Example 1 The p-type contact structure 9 of FIG.
Of the p-type cladding layer 3 to the p-type cap layer 8 (collectively SCH-SQ) on the GaAs (001) substrate 2.
The W structure 11) is produced by the molecular beam epitaxial method using the molecular beam epitaxial apparatus shown in FIG. At that time, set the Zn beam flux to 5.0 ×
^10-2 7 Torr, a beam flux of Cd 1.0 × 1
0 ^over 7 Torr, a beam flux of Mg 5.0 × 10
^-7 Torr, Se beam flux 5.0 × 10 ^-7
The beam flux of Torr and ZnS is 7.0 × 10 ⁻⁸ Torr for the cladding layer and 3.0 × 1 for the guide layer.
0 ^over 8 Torr, a beam flux of ZnTe 1.67
× 10 advance to adjust the temperature of each cell 58-64 to be ^over 7 Torr, the active nitrogen as a dopant cell 66
The ZnCl ₂ cell 65 and the ZnCl ₂ cell 65 are adjusted so as to satisfy the optimum doping condition. Further, the growth rate at the time of producing the SCH-SQW structure 11 is set to 500 nm / h. The SCH-SQW structure 11 is a well-known structure (K. Ohkawa et al .; Japan Jounal of Applied).
Physics Vol.33 (1994) pp.L1673).

First, a Zn cell 58, a Mg cell 64, a Se cell 60, and a ZnS cell 5 for a cladding layer are formed on a GaAs (001) substrate 67 which has been subjected to a surface treatment such as removal of an oxide film.
9. Open the shutter of the ZnCl ₂ cell 65 and the shutter 68 in front of the substrate, and open the chlorine-doped n-type Zn for 2 hours.
_0.9 Mg _0.1 S _0.15 Se _{0.85 The} clad layer 3 having a thickness of 1.0 μm is formed. Next, the shutters of the Mg cell 63, the ZnS cell 59 for the clad layer and the ZnCl ₂ cell 65 are closed, and the shutter of the ZnS cell 63 for the guide layer is opened for 16 minutes 48.
Undoped ZnS _0.06 Se with a layer thickness of 1400Å over seconds
_0.94 Guide layer 4 is prepared.

After that, the shutter of the ZnS cell 63 for the guide layer is closed, the shutter of the Cd cell 61 is opened, and the undoped Zn _0.8 Cd _0.2 Se active layer 5 having a layer thickness of 60 Å is formed over 43 seconds. After that, the shutter of the Cd cell 61 is closed, and the shutter of the ZnS cell 63 for the guide layer is opened.
Undoped ZnS with a layer thickness of 1400Å over 6 minutes 48 seconds _.
06 Se _0.94 Guide layer 6 is prepared. Then, the shutter of the ZnS cell 63 for the guide layer is closed and the ZnS cell 63 for the clad layer is closed.
The shutters of the S cell 59, the Mg cell 64, and the active nitrogen cell 66 were opened, and the nitrogen-doped p-type Zn was taken for 1 hour and 24 minutes.
_{The 0.9} Mg _0.1 S _0.15 Se _0.85 clad layer 7 is formed to 0.7 μm.

Thereafter, the Mg cell 64 and Z for the cladding layer are formed.
The shutter of the nS cell 59 is closed, the shutter of the ZnS cell 63 for the guide layer is opened, and the layer thickness is 3000 Å in 36 minutes.
Of p-type ZnS _0.06 Se _0.94 cap layer 8 of
The H-SQW structure 11 is completed.

Next, the p-type contact structure 9 shown in FIG. 1 of the present invention is manufactured. The shutter of the ZnS cell 63 for the guide layer is closed, and the shutters of the Zn cell 58, the Se cell 60 and the active nitrogen cell 66 are opened as they are, and the p-type ZnSe layer 12 is exposed for 2 minutes and 15 seconds while performing nitrogen doping.
00Å Stack.

Next, the shutter of the Te cell 62 is opened and 2
The p-type ZnSe _0.75 Te _0.25 layer 13 is stacked 200 Å over a period of time. After that, the shutter 68 in front of the substrate is once closed to stop the growth, and the temperature of the Se cell 60 is lowered and the temperature of the Te cell 62 is raised until the beam flux of Se and Te becomes 3.0 × 10 ⁻⁷ Torr. When the beam flux of Se and Te reaches 3.0 × 10 ⁻⁷ Torr, the shutter 68 in front of the substrate is opened to restart crystal growth, and the p-type ZnSe _0.5 Te _0.5 layer 14 is heated to 200 Å in 2 minutes and 15 seconds.
Stack.

Thereafter, the shutter 68 in front of the substrate is closed again to stop the growth, and the beam flux of Se is 1.67 ×.
Beam flux of 10 ^-7 Torr and Te is 5.0 × 1
The temperature of the Se cell 60 is lowered to 0 ^-7 Torr, and T
e Increase the temperature of the cell 62. If the beam flux of Se is 1.67 × 10 ⁻⁷ Torr and the beam flux of Te is 5.0 × 10 ⁻⁷ Torr, the shutter 6 in front of the substrate 6
Opening No. 8 and restarting the crystal growth, the p-type Z takes 2 minutes and 15 seconds.
The nSe _0.25 Te _0.75 layer 15 is laminated to 200 Å.

Finally, the shutter of the Se cell 60 is closed and Z
The shutters of the n-cell 58, the Te cell 62, and the active nitrogen cell 66 are opened for 3 minutes and 20 seconds, the p-type ZnTe contact layer 16 is laminated to 300Å, all the shutters are closed to complete the crystal growth, and the p-type contact structure 9 is formed. Complete the laser structure including.

After that, as shown in FIG. 16, the laser structure 76 is etched by using a saturated aqueous bromine solution or the like to form a ridge or mesa stripe structure 77, and an insulator 78 such as ZnO (or SiO 2) 78 is formed. The side surface of the ridge is filled with and the current confinement structure 79 is manufactured.

After that, Au and P are added to the p-type contact structure.
The Au / Pt / Pd electrode 10 is completed by depositing t and Pd. On the back surface of the n-type GaAs substrate, Au, G
e and Ni are vapor-deposited to prepare an Au / Ge / Ni electrode. A laser wafer is manufactured as described above. Finally,
The laser wafer is cleaved and mounted to manufacture a laser element.

Laser device manufactured by the above method
The characteristics of are described below. P-type contact of the above laser device
Figure 1 shows the band diagram of the valence band for the structure 9
Represented in 5. In FIG. 15, the horizontal axis represents the contact structure.
Position, the vertical axis shows the position of the band edge of the valence band, and the solid line
The graph shows the p-type contact structure for the light emitting device of the present invention.
9 band diagram, broken line is conventional SCH-SQ
ZnSe on top of W structure _1-xTe_xChange the composition x of
The band diagram of the contact structure
However, the one-dot chain line is the most p-type contact structure in the past.
Shows the band diagram of the one produced under ideal conditions.
You.

Ideally, it would be ideal if a contact structure capable of obtaining a band diagram such as the one-dot chain line could be produced, but in order to produce such a contact structure, the layer thickness of each layer in the structure is set in units of one atomic layer. It must be controlled accurately. Due to the difficulty of controlling the layer thickness, the band diagram of the conventional p-type contact structure obtained actually becomes a step-like graph having a barrier height of about 1 eV as shown by a broken line.

On the other hand, the barrier height of the band diagram of the p-type contact structure 9 of the present invention shown by the solid line is about 0.3 eV.
The shape does not change even if the layer thickness of each layer in the structure deviates by about 100Å. This means that the change in the characteristics due to the layer thickness is small as described in FIG. 8 below.

FIG. 7 shows the IV characteristics of the above laser device.
Shown in FIG. 7 shows the IV characteristics of the laser device having the contact structure of the present invention and the conventional one, in which the horizontal axis represents the bias voltage applied to the device and the vertical axis represents the current density flowing in the device. In FIG. 7, the solid line indicates the IV characteristics of the light emitting device of the present invention, and the broken line indicates the ZnSe on the conventional SCH-SQW structure.
Suitably changing the composition x of _{1 over x} Te _x represents a graph relating the I-V characteristic of the light emitting device having a stacked contact structure. From FIG. 7, it is apparent that the light emitting device of the present invention is
It can be seen that the −V characteristic is good.

The threshold voltage of the light emitting device of the present invention is 3.0 V as shown in FIG. 8 below, and the operating voltage is remarkably reduced as compared with the conventional light emitting device. As can be seen from FIG. 15, in the p-type contact structure 9 of the present invention, the band offset of the valence band between the p-type ZnTe contact layer 16 and the SCH-SQW structure 11 is effectively relaxed, This is because the barrier height of the band of the valence band is actually smaller than that of the conventional contact structure.

The p-type ZnSe layer 12 and p-type ZnTe
FIG. 8 shows the relationship between the number of p-type ZnSe _1-x Te _x layers and the threshold voltage when the layer thickness of the p-type ZnSe _1-x Te _x layer sandwiched between the layer 16 and the layer 16 is variously changed. Show. In FIG. 8, the horizontal axis represents the number of p-type ZnSe _1-x Te _x layers, the vertical axis represents the threshold voltage, and the black squares represent the total layer thickness of the p-type ZnSe _1-x Te _x layers of 500Å. The triangle is 1000Å and the black circle is 200Å
The graph in the case of is shown.

From FIG. 8, the p-type ZnTe contact layer and S
ZnSe between CH-SQW structure _1-xTe_xNumber of layers
It can be seen that the characteristics are still improved when the number of layers increases to 4 or 5.
You. Also, the threshold value depends on the layer thickness of the p-type contact structure.
It can be seen that the voltage does not change significantly. In fact, the layer thickness
If the total is over 500Å, there is almost no difference. This is subordinate
It is characterized by layer thickness more than the known p-type contact structure.
Thickness is small when the contact structure is manufactured.
It is shown that it is easy to control.

From the above results, at least three layers of ZnSe _1-x Te _x (0 ≦ x ≦) having p-type conductivity are provided between the p-type ZnTe contact layer and the SCH-SQW structure.
By crystallizing 1), the band offset of the valence band between the p-type ZnTe contact layer and the SCH-SQW structure is effectively relaxed, the operating voltage of the laser is sufficiently lowered, and the layer thickness is controlled. It was revealed that an easy p-type contact structure can be obtained.

The contact structure is shown in FIG.
P-type ZnSe _1-x Te _x (x = 0.25, 0.5, 0.
75) instead of (ZnSe) _m (ZnTe) _n (m, n
Is a natural number) and similar results are obtained. Specifically, 13 in FIG. 1 is (ZnSe) 3 (ZnTe) 1, 14 is (ZnSe) 1 (ZnTe) 1, 15 is (ZnSe) 1
It may be (ZnTe) 3.

Example 2 First, the same method as in Example 1
The SCH-SQW structure 11 is produced by a procedure. Next, a p-type contact structure for the light emitting device shown in FIG. 2 of the present invention is manufactured. First, the shutter 68 in front of the substrate is closed to interrupt the crystal growth, and the ZnS beam flux is adjusted so that the ZnS beam flux becomes 5 × 10 ⁻⁷ Torr.
Raise the temperature of the S cell 59. If the beam flux of ZnS becomes 5 × 10 ⁻⁷ Torr, the Zn cell 58, S
The shutter of the e-cell 60 is closed, the shutters of the ZnS cell 59 for the cladding layer and the active nitrogen cell 66 are opened, and the p-type ZnS6 atomic layers 18 and 30Å are stacked for 20 seconds while performing nitrogen doping. After that, Zn for the cladding layer
The shutter of the S cell 59 is closed, and instead of the Zn cell 58,
The shutter of Te cell 62 is opened, and p-type Zn is taken for 6 seconds.
Te1 atomic layers 19 and 6Å are laminated. Such ZnS
The structure of 6 atomic layers / ZnTe 1 atomic layer is repeatedly laminated three times to form a p-type layer ((ZnS) ₆ (ZnTe) ₁ ) having a layer thickness of 144 Å.
_{The four} layers 28 are produced.

P-type ((ZnS) ₆ (ZnTe) ₁ ) ₄ layer 2
8 was manufactured, and then p-type ((ZnS) was formed by the same method as above.
₄ (ZnTe) ₃ ) ₄ layer 29, and p-type ((Z
An nS) ₁ (ZnTe) ₄ ) ₅ layer 30 is produced. Finally Z
The shutters of the n-cell 58, the Te cell 62, and the active nitrogen cell 66 are opened for 6 minutes and the p-type ZnTe contact layer 27 is set to 50.
After stacking 0Å, closing all the shutters to complete the crystal growth, the laser structure including the p-type contact structure 31 is completed.

Then, as in the first embodiment, as shown in FIG. 16, the laser structure 76 is etched using a saturated aqueous bromine solution or the like to form a ridge or mesa stripe structure 77, and insulation of ZnO or the like is performed. The side surface of the ridge is filled with the object 78 to form the current constriction structure 79. Then p
Au, Pt, and Pd are vapor-deposited on the mold contact structure to form Au.
The / Pt / Pd electrode 10 is produced. In addition, n-type GaAs
Au, Ge, and Ni are vapor-deposited on the back surface of the substrate to form an n-type electrode. A laser wafer is manufactured as described above.
Finally, the laser wafer is cleaved and mounted to manufacture a laser element.

The characteristics of the laser structure and the characteristics of the laser device manufactured by the above method will be described below. First, regarding the characteristics of the laser structure, when observing the cross section of the laser structure with a scanning electron microscope, the defects in the p-type contact structure that have been conventionally observed are not seen. This indicates that the light emitting device of the present invention has better crystallinity than before.

Next, the characteristics of the laser device will be described.
FIG. 9 shows the IV characteristics of the laser device. FIG.
Represents the IV characteristics of the laser device having the present invention and the conventional contact structure, the horizontal axis represents the bias voltage applied to the device, and the vertical axis represents the current density flowing in the device. In FIG. 9, a solid line indicates an IV characteristic of the light emitting device of the present invention, and a broken line indicates a conventional light emitting device having a contact structure in which the composition x of ZnSe 1 -xTex is laminated on the SCH-SQW structure by appropriately changing the composition x. It is an IV characteristic. From FIG. 9, it is apparent that the light emitting device of the present invention has much better IV characteristics.

The threshold voltage of the light emitting device of the present invention is 3.0 V, which is lower than that of the conventional light emitting device.
This is because the contact structure of the light emitting device of the present invention has better crystallinity than before, and the operating voltage does not rise due to the deterioration of crystallinity.

From the above results, p-type ZnTe having a large lattice constant and Zn having a small lattice constant with respect to the GaAs substrate are obtained.
P-type (ZnTe) _j (Z
By using a superlattice such as nS) _k (j and k are natural numbers), there is no crystal defect that is lattice-matched with the GaAs substrate,
It has been clarified that a p-type contact structure having a sufficiently lowered operating voltage can be obtained.

The contact structure is shown in FIG.
Of p-type _{((ZnS) k (ZnTe)} m) j (j, k, m is a natural number) p-type ZnS _x T as shown in FIG. 2 (b) in place of
Similar results are obtained using e _1-x (0 <x <1).

(Embodiment 3) First, the same method as in Embodiment 1,
The SCH-SQW structure 11 is produced by a procedure.

Next, the p-type contact structure of the present invention shown in FIG. 3 is produced. The shutter of the ZnS cell 59 for the clad layer is closed, and the shutters of the Zn cell 58, the Se cell 60 and the active nitrogen cell 66 are opened as they are, and the p-type ZnSe layer 32 is exposed to 30% for 30 minutes while performing nitrogen doping.
0Å Stack.

Next, the shutter of the Se cell 60 is closed and T
The shutter of the e-cell 62 is opened for 5 seconds, and the p-type ZnTe1 atomic layers 33 and 6Å are laminated. Then, close the shutter of the Te cell 62, open the shutter of the Se cell 60 for 12 seconds, p
Type ZnSe3 atomic layers 34, 17Å are laminated. afterwards,
The shutters of the Se cell 60 and the Te cell 62 are closed, the shutter of the ZnS cell 59 for the cladding layer is opened for 15 seconds, and the p-type ZnS1 atomic layers 35 and 5Å are laminated. Such Zn
The structure of Te1 atomic layer / ZnSe3 atomic layer / ZnS1 atomic layer is repeatedly stacked three more times to form a p-type ((ZnSe) ₃ (ZnTe) ₁ (ZnS) ₁ ) ₄ layer 46 having a layer thickness of 108Å.

P-type ((ZnSe) ₃ (ZnTe) ₁ (Zn
S) ₁ ) After forming ₄ layers, p-type ((Zn
Se) ₂ (ZnTe) ₂ (ZnS) ₃ ) ₃ layer 47, and p-type ((ZnSe) ₁ (ZnTe) ₃ (Zn
S) ₃ ) ₃ layers 48 are produced. Finally Zn cell 58, Te
Open the shutters of cell 62 and active nitrogen cell 66 for 6 minutes, p
The type ZnTe contact layer 45 is formed to a thickness of 500Å, all the shutters are closed to complete the crystal growth, and the laser structure including the p-type contact structure 49 is completed.

Then, as in the first embodiment, as shown in FIG. 16, the laser structure 76 is etched using a saturated bromine aqueous solution or the like to form a ridge or mesa stripe structure 77, and insulation of ZnO or the like is formed. The side surface of the ridge is filled with the object 78 to form the current constriction structure 79. Then p
Au, Pt, and Pd are vapor-deposited on the mold contact structure to form Au.
/ Pt / Pd electrode 10 is completed. In addition, n-type GaA
Au, Ge, and Ni are vapor-deposited on the back surface of the s substrate to produce an n-type electrode. A laser wafer is manufactured as described above.

Finally, the laser wafer is cleaved and mounted to produce a laser element. The characteristics of the laser structure and the characteristics of the laser device manufactured by the above method will be described below. First, regarding the characteristics of the laser structure, when observing the cross section of the laser structure with a scanning electron microscope, the defects in the p-type contact structure that have been conventionally observed are not seen. This indicates that the light emitting device of the present invention has better crystallinity than before.

Next, the characteristics of the laser device will be described.
FIG. 10 shows the IV characteristics of the laser device. In FIG. 10, the solid line indicates the IV characteristic of the light emitting device of the present invention,
The dashed line shows the ZnSe _1-x on the conventional SCH-SQW structure.
Suitably changing the composition x of Te _x is the I-V characteristic of the light emitting device having a stacked contact structure. From FIG. 10, it is apparent that the light emitting device of the present invention has better IV characteristics. The threshold voltage of the light emitting element of the present invention is 3.0 V, which is lower than that of the conventional light emitting element. This is because the contact structure of the light emitting device of the present invention has better crystallinity than before, and the operating voltage does not rise due to the deterioration of crystallinity.

From the above results, p-type ZnSe and ZnTe having a large lattice constant and ZnS having a small lattice constant are alternately laminated on a GaAs substrate to produce a p-type (Zn
By using a superlattice such as Se) _i (ZnTe) _j (ZnS) _k (i, j, and k are natural numbers), a p-type contact that is lattice-matched with a GaAs substrate, has no crystal defects, and has a sufficiently low operating voltage. It was revealed that the structure was obtained.

The contact structure is shown in FIG.
P-type ((ZnTe) _m (ZnSe) _n (ZnS) _k )
Instead of _j (m, n, k, and j are natural numbers), p-type ZnS _x Se _y Te _1-xy (0 <x <1, 0 <
y <1) or p-type (ZnSe _{1 −x} Te _x ) _m (ZnS _y S
Similar results can be obtained by using e _1-y ) _n (0 <x <1, 0 <y <1, m and n are integers).

(Fourth Embodiment) First, the same method as in the first embodiment,
The SCH-SQW structure 11 is produced by a procedure. Next, the p-type contact structure of the present invention shown in FIG. 11 is produced. The shutters of the Zn cell 58, the Se cell, the ZnS cell, and the active nitrogen cell are opened as they are, and p-type ZnSe 300Å is produced over 3 minutes and 20 seconds while performing nitrogen doping.

After that, the shutter 68 on the front side of the substrate is temporarily returned.
To stop the growth, and the Cd beam flux becomes 5.
The temperature of the Cd cell 61 was lowered to 5 × 10 ⁻⁸ Torr, and the ZnS beam flux was 1.25 × 10 ⁻⁷ Tor.
The temperature of the ZnS cell 59 for the cladding layer is raised until it becomes rr. Cd beam flux is 5.5 × 10 ^-8 To
Beam flux of rr and ZnS is 1.25 × 10 ^-7 T
At orrr, the shutters of the Cd cell 61 and the ZnS cell 59 and the shutter 68 in front of the substrate are opened to restart crystal growth, and the p-type Zn _0.9 Cd _0.1 S _0.2 Se _0.8 layer 51 is taken over 6 minutes.
500 Å are laminated. After that, all the shutters are closed to complete the crystal growth, and the laser structure including the p-type contact structure is completed.

Then, as in the first embodiment, as shown in FIG. 16, the laser structure 76 is etched using a saturated aqueous bromine solution or the like to form a ridge or mesa stripe structure 77, and insulation of ZnO or the like is performed. The side surface of the ridge is filled with the object 78 to form the current constriction structure 79. Then p
Au, Pt, and Pd are vapor-deposited on the mold contact structure to form Au.
/ Pt / Pd electrode 11 is completed. In addition, n-type GaA
Au / Ge / Ni is vapor-deposited on the back surface of the s substrate to form an n-type electrode. A laser wafer is manufactured as described above.

Finally, the laser wafer is cleaved and mounted to manufacture a laser element. The characteristics of the laser structure and the characteristics of the laser device manufactured by the above method will be described below. First, regarding the characteristics of the laser structure, it is shown that the X-ray analysis peaks of all layers in the laser structure coincide with the peaks of the GaAs substrate and are lattice-matched to the GaAs substrate. Further, when observing the cross section of the laser structure with a scanning electron microscope, the defects in the p-type contact structure which have been conventionally observed are not observed. This indicates that the light emitting device of the present invention has better crystallinity than before.

Next, the characteristics of the laser device will be described.
The IV characteristics of the laser device are shown in the figure. FIG.
In the figure, the solid line indicates the IV characteristic of the light emitting element of the present embodiment, and the broken line indicates the IV characteristic of the light emitting element of the first embodiment. From FIG. 11, it is apparent that the light emitting element of this example has better IV characteristics. The threshold voltage of the light emitting element of this embodiment is 2.7V, which is 0.3V lower than that of the light emitting element of the first embodiment. This indicates that the characteristics of the contact structure of the light emitting device of the present embodiment are better than those of the contact structure of the first embodiment. Needless to say, the characteristics of the light emitting element of this embodiment are better than those of the conventional one.

From the above results, instead of ZnSe _1-x Te _x mixed crystal, p-type Zn _1-x Cd _x S _y Se _1-y mixed crystal (0 ≦ x ≦) having a smaller band offset in the valence band is obtained. 1,0 ≦ y
It was revealed that the use of ≦ 1) makes it possible to obtain a p-type contact layer which is lattice-matched to the GaAs substrate, has no crystal defects, and has a sufficiently low operating voltage.

The contact structure is shown in FIG.
P-type Zn _1-x Cd _{x Sy} Se _1-y (0 <x <1, 0 <y <
1) instead of p-type (Zn _1-x Cd _x Se) _m (ZnS _y S
e _{1- y} ) _n (0 <x <1, 0 <y <1, m and n are integers),
Or p-type ((Zn _1-x Cd _x S) _m (ZnS _y S
Similar results can be obtained by using e _1-y ) _k ) _j (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, j, k, and m are integers).

(Embodiment 5) A p-type contact layer of the present invention and a method for producing the same will be described with reference to the drawings.

First, the SCH-SQW structure is manufactured by the same method and procedure as in the first embodiment. Next, the p-type contact structure of the present invention shown in FIG. 5 is produced. Once the shutter 68 in front of the substrate is closed to stop the growth, ZnS and Cd
Beam flux of 5.0 × 10 ^-7 Torr
The temperature of the ZnS cell 59 for the cladding layer and the temperature of the Cd cell 61 are raised until the temperature reaches Next, the Zn cell 58 and the Se cell 60
Open the shutter for 8 seconds, p-type ZnSe2 atomic layer 53, 1
Make 1 Å. Then, the shutter of the Zn cell 58 is closed, the shutter of the Cd cell 61 is opened for 8 seconds, and the p-type CdS is opened.
The e2 atomic layer 54, 12Å is produced. After that, the shutters of the Cd cell 61 and the Zn cell are closed, and the shutter of the ZnS cell is opened for 12 seconds to produce p-type ZnS3 atomic layers 55 and 15Å. Such a structure of ZnSe2 atomic layer / CdSe2 atomic layer / ZnS1 atomic layer was repeatedly prepared eight times,
P-type ((ZnSe) ₂ (CdSe) ₂ (Z
A p-type contact structure 57 consisting of nS) ₃ ) ₉ layers is produced.

After that, all the shutters are closed to complete the crystal growth, and the laser structure including the p-type contact structure 57 is completed.

Then, as in the first embodiment, as shown in FIG. 16, the laser structure 76 is etched using a saturated bromine aqueous solution or the like to form a ridge or mesa stripe structure 77, and insulation of ZnO or the like is formed. The side surface of the ridge is filled with the object 78 to form the current constriction structure 79. Then p
Au, Pt, and Pd are vapor-deposited on the mold contact structure to form Au.
/ Pt / Pd electrode 10 is completed. In addition, n-type GaA
Au / Ge / Ni is vapor-deposited on the back surface of the s substrate to form an n-type electrode. A laser wafer is manufactured as described above.

Finally, the laser wafer is cleaved and mounted to manufacture a laser element. The characteristics of the laser structure and the characteristics of the laser device manufactured by the above method will be described below. First, regarding the characteristics of the laser structure, it is shown that the X-ray analysis peaks of all layers in the laser structure coincide with the peaks of the GaAs substrate and are lattice-matched to the GaAs substrate. Further, when observing the cross section of the laser structure with a scanning electron microscope, the defects in the p-type contact structure which have been conventionally observed are not observed. This indicates that the light emitting device of the present invention has better crystallinity than before.

Next, the characteristics of the laser device will be described.
FIG. 12 shows the IV characteristics of the laser device. In FIG. 12, the solid line represents the IV characteristic of the light emitting element of this example, and the broken line represents the IV characteristic of the light emitting element of Example 1. From FIG. 12, it is clear that the light emitting device of this embodiment has IV
You can see that the characteristics are good. The threshold voltage of the light emitting element of this embodiment is 2.7V, which is 0.3V lower than that of the light emitting element of the first embodiment. This indicates that the characteristics of the contact structure of the light emitting device of the present embodiment are better than those of the contact structure of the first embodiment. Needless to say, the characteristics of the light emitting element of this embodiment are better than those of the conventional one. The contact structure is ZnSe, CdSe, ZnS.
Since it is a superlattice composed of the binary crystal of, the contact structure with higher carrier density and lower resistance than the contact structure using p-type Zn _0.9 Cd _0.1 S _0.2 Se _0.8 in FIG. 4 is realized.
The characteristics are further improved.

From the above results, instead of the ZnSe _1-x Te _x mixed crystal as the p-type contact layer for ZnSe,
P-type (ZnS having a smaller band offset in the valence band)
e) p that is lattice-matched to the GaAs substrate by using a superlattice such as _i (CdSe) _j (ZnS) _k (i, j, and k are natural numbers), has no crystal defects, and has a sufficiently low operating voltage
It was revealed that a mold contact layer was obtained.

[0069]

According to the present invention, it is possible to obtain a p-type contact structure which is superior in controllability to the structure and has a low resistance as compared with the conventional structure. As a result, a lower threshold voltage is realized and the characteristics are better than those in the conventional structure. It is possible to obtain an excellent semiconductor light emitting device.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of a light emitting device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a contact structure for a light emitting device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a contact structure for a light emitting device according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a contact structure relating to a light emitting device of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a contact structure for a light emitting device according to a fifth embodiment of the present invention.

FIG. 6 is a structural cross-sectional view of a molecular beam epitaxial device for producing the semiconductor light emitting device of the present invention.

FIG. 7 shows I- of the light emitting device according to the first embodiment of the present invention.
Diagram showing V characteristics

FIG. 8 shows p of a contact structure for a light emitting device of the present invention
Of the relationship between the number of ZnSe1-xTex layers and the threshold voltage

FIG. 9 shows an I- of a light emitting device according to a second embodiment of the present invention.
Diagram showing V characteristics

FIG. 10 relates to a light emitting device of a third embodiment of the present invention I
Figure showing -V characteristics

FIG. 11 relates to a light emitting device of a fourth embodiment of the present invention I
Figure showing -V characteristics

FIG. 12 is a schematic diagram of a light emitting device according to a fifth embodiment of the present invention.
Figure showing -V characteristics

FIG. 13 is a diagram showing a relationship between a band gap and a lattice constant of a II-VI group compound semiconductor.

FIG. 14 is a sectional view of a contact structure for a conventional semiconductor light emitting device.

FIG. 15 is a diagram showing a band diagram of a valence band regarding a p-type contact structure of a light emitting device of the present invention and a conventional light emitting device.

FIG. 16 is a diagram illustrating a method for manufacturing a ridge stripe structure for a light emitting element of the present invention

[Explanation of symbols]

2 n-type GaAs substrate 9 p-type contact structure 13 p-type ZnSe _0.75 Te _0.25 layer 14 p-type ZnSe _0.5 Te _0.5 layer 15 p-type ZnSe _0.25 Te _0.75 layer 28 p-type ((ZnS) ₆ (ZnTe) ₁ ) ₄ layer 29 p-type ((ZnS) ₄ (ZnTe) ₃ ) ₄ layer 30 p-type ((ZnS) ₁ (ZnTe) ₄ ) ₅ layer 31 p-type contact structure 46 p-type ((ZnSe) ₃ (ZnTe) ₁ (ZnTe)
S) ₄ ) ₄ layers 47 p-type ((ZnSe) ₂ (ZnTe) ₂ (Zn
S) ₃ ) ₃ layer 48 p-type ((ZnSe) ₁ (ZnTe) ₃ (Zn
S) ₃ ) ₃ layers 49 p-type contact structure 51 p-type Zn _0.9 Cd _0.1 S _0.2 Se _0.8 layer 52 p-type contact structure 53 p-type CdSe 2 atomic layer 54 p-type ZnSe 2 atomic layer 55 p-type ZnS 2 atomic layer 57 p-type contact Structure 73 p-type ZnSe _1-x Te _x graded layer 75 p-type contact structure

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoichi Sasai 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor, Yuu Uenoyama 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (20)

[Claims] 1. A GaAs substrate, a double hetero structure composed of a II-VI group compound laminated on the GaAs substrate, and at least three layers having p-type conductivity laminated on the double hetero structure. And a contact structure composed of ZnSe _1-x Te _x (0 ≦ x ≦ 1) in which the composition of each layer is different. 2. The contact structure is (ZnSe) _m (ZnT).
2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is composed of e) _n (m and n are natural numbers). 3. A GaAs substrate, a double hetero structure composed of a II-VI group compound laminated on the GaAs substrate, and at least three layers having p-type conductivity laminated on the double hetero structure. And a contact structure composed of ZnS _1-x Te _x (0 ≦ x ≦ 1) in which the composition of each layer is different. 4. The contact structure is (ZnS) _m (ZnT).
The semiconductor light emitting device according to claim 3, wherein the semiconductor light emitting device is composed of e) _n (m and n are natural numbers). 5. A GaAs substrate, a double heterostructure composed of a II-VI group compound laminated on the GaAs substrate, and at least three layers having p-type conductivity laminated on the double heterostructure. ZnS _x Se _{1 -xy} Te _y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) in which the composition of each layer is different
And a contact structure composed of the following. 6. The contact structure is (ZnSe) _k (Zn
The semiconductor light emitting device according to claim 5, wherein the semiconductor light emitting device is composed of S) _m (ZnTe) _n (k, m, and n are natural numbers). 7. The contact structure is (ZnS _x Se _1-x ).
_m (ZnSe _1-y Te _y ) _n (0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
6. The semiconductor light emitting device according to claim 5, wherein m and n are natural numbers. 8. The contact structure is (ZnS _x Se _1-x ).
_m (ZnS _1-y Te _y ) _n (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, m,
6. n is a natural number)
The semiconductor light-emitting device according to claim 1. 9. The contact structure is (ZnS _x Te _1-x )
_m (ZnSe _1-y Te _y ) _n (0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
6. The semiconductor light emitting device according to claim 5, wherein m and n are natural numbers. 10. A GaAs substrate, a double hetero structure composed of a II-VI group compound laminated on the GaAs substrate, and zinc, cadmium, sulfur and selenium laminated on the double hetero structure as components. And a contact structure made of a II-VI group compound having p-type conductivity. 11. A contact structure comprising p-type Zn _1-x Cd _x S
11. The semiconductor light emitting device according to claim 10, wherein _y Se _1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is laminated by changing the composition. 12. The contact structure is ((Zn _1-x Cd _x S
e) _m (ZnS _y Se _1-y ) _k ) _j (0 ≦ x ≦ 1, 0 ≦ y ≦
12. The semiconductor light emitting device according to claim 11, wherein 1, j, k, and m are integers. 13. The contact layer comprises ((Zn _1-x Cd _x S
e) _m (ZnS _y Se _1-y ) _k ) _j (0 ≦ x ≦ 1, 0 ≦ y ≦
12. The semiconductor light emitting device according to claim 11, wherein (1, j, k, m are integers) are laminated while changing m, k, j. 14. A GaAs substrate, a double heterostructure composed of a II-VI group compound laminated on the GaAs substrate, and p-type ZnSe on the double heterostructure.
An atomic layer, an n atomic layer of p-type CdSe, and a k atomic layer of p-type or undoped ZnS (m, n is an integer, k is a natural number) are alternately repeated j times and are laminated on the GaAs substrate so as to be coherent (( ZnSe) _m (CdSe) _n (Zn
S) _k ) _j , a semiconductor light-emitting device. 15. The contact structure is ((ZnSe)).
_m (CdSe) _n (ZnS) _k ) _j (m and n are integers, j and k
15. The semiconductor light-emitting device according to claim 14, wherein is a natural number) and is laminated while changing m, n, k, and j. 16. A double hetero structure of a II-VI compound semiconductor, and a contact structure of a p-type ZnSe _1-x Te _x (0 ≦ x ≦ 1) layer laminated on the double hetero structure, A semiconductor light-emitting device characterized in that the p-type ZnSe _1-x Te _x layer is composed of at least three layers, and each layer has a different composition. 17. A double heterostructure of a II-VI compound semiconductor, and a contact structure of a p-type ZnS _1-x Te _x (0 ≦ x ≦ 1) layer laminated on the double heterostructure, The semiconductor light emitting device characterized in that the p-type ZnS _1-x Te _x layer is composed of at least three layers and each layer has a different composition. 18. A double heterostructure of II-VI compound semiconductor, and p-type ZnS _x Se _1-xy Te _y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) laminated on the double heterostructure. And a contact structure of layers, wherein the p-type ZnS _x Se _1-xy Te _y layer is composed of at least three layers and layers each having a different composition. 19. A group II-VI compound semiconductor double heterostructure, and a group II-VI group having zinc-, cadmium-, sulfur-, and selenium-layered components and having p-type conductivity. A semiconductor light-emitting device having a contact structure of a compound semiconductor. 20. A double heterostructure comprising a II-VI group compound, and p-type ZnSe on the double heterostructure.
Is an m atomic layer, p-type CdSe is an n atomic layer, and p-type or undoped ZnS is a k atomic layer (m and n are integers, k is a natural number).
Alternatingly repeated j times to be coherently laminated on the GaAs substrate ((ZnSe) _m (CdSe) _n (Z
and a contact structure composed of nS) _k ) _j .