JP2000022203A - Light emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode which is high light emission efficiency and has stable property to temperature ripple by preventing the overflow of electrons from a well layer at implantation of carriers in high density. SOLUTION: An InGaAlAs light guide layer 31 is made on the topside of an n-type InP substrate 11, and further an InGaAs well layer 32 and an InGaAs barrier layer 33 are stacked in order thereon. The energy difference between the first quantum level of the positive holes in the InGaAs well layer 32 and the top of the valence band in the InGaAsP barrier layer 33 is about 107 meV, and the energy difference between the first quantum level of the electron in the InGaAs well layer 32 and the bottom of the conduction band of the InGaAlAs barrier layer 33 is about 186 meV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode, and more particularly to a light emitting diode having a quantum well structure that can be used for an optical communication device or the like.

[0002]

2. Description of the Related Art Conventionally, a light emitting layer of an edge-emitting type light emitting diode having an absorption region therein is provided with "Japan Jou."
rnal of Applied Physics, V
ol. 33 (1994) pp. 6584-6585, P
art1, No. 1; 12A, December 199
4 ", a quantum well structure has been used.

The barrier layer in the light emitting layer of such a conventional edge emitting type light emitting diode includes the above-mentioned document No. 6584F.
ig. As shown in FIG. 1, InGaAsP was adopted. When a quantum well type structure is applied to the light emitting layer of a light emitting diode, the temperature dependence of the light output of the light emitting diode and the shift amount of the peak wavelength due to the temperature are controlled by the effect of confinement of two-dimensionally quantized carriers. This is reduced as compared with the case where the structure is adopted.

[0004]

SUMMARY OF THE INVENTION However, InG
In a quantum well type structure using aAsP as a barrier layer, as shown in FIG.
h and the energy difference δEv between the top of the valence band VB of the barrier layer 43 and the first quantum level E1e of electrons in the well layer 41 and the conduction band CB of the barrier layer 43.
Is smaller than the energy difference δEc of the bottom. The energy difference δEv and the energy difference δEc are determined by the discontinuity of the band edge energy due to the electric affinity specific to the crystal material.
When s is used and InGaAsP (composition wavelength: 1.2 μm) is used as the barrier layer 43, the energy difference δEv is about 1
94 meV, and the energy difference δEc is about 101 me
V.

As described above, a light emitting diode having a quantum well structure having a large energy difference δEv and a small energy difference δEc has the following problems to be solved.

(1) Since the energy difference δEc is small, when electrons are injected at a high density, an overflow phenomenon of electrons from the well layer 41 has occurred. In particular, the number of overflowing electrons increases with increasing device temperature,
As a result, the luminous efficiency was reduced.

(2) In connection with the above (1), when the number of the well layers 41 is increased in order to reduce the amount of electron overflow, all the well layers 41 are reduced due to the magnitude of the energy difference δEv. However, there has been a problem that holes are not uniformly injected, and the luminous effect is reduced.

The present invention has been made in view of the above-mentioned problems, and has as its object to prevent the overflow of electrons from the well layer at the time of high-density injection of carriers, thereby achieving high luminous efficiency. An object of the present invention is to provide a light emitting diode having stable characteristics against temperature fluctuation.

[0009]

In order to solve the above-mentioned problems, there is provided a light emitting diode having a quantum well type structure layer in which one or more well layers and barrier layers are stacked.
The light emitting diode is characterized in that the well layer is formed of InGaAs and the barrier layer is formed of InGaAlAs. According to such a configuration, the first hole in the well layer is formed.
It is possible to reduce the energy difference δEv between the quantum level and the top of the valence band in the barrier layer, and conversely, the energy difference between the first quantum level of electrons in the well layer and the bottom of the conduction band in the barrier layer. δEc can be increased. And if the energy difference δEv is made smaller than the energy difference δEc as described in claim 2,
The overflow of electrons injected into the well layer is prevented,
At the same time, holes are uniformly injected into the well layer.

According to a third aspect of the present invention, the well layer is formed of InGaAsP, and the barrier layer is formed of InGaAl.
It may be formed by As. Then, the energy difference between the first quantum level of holes in the well layer and the top of the valence band in the barrier layer is determined by the first quantum level of electrons in the well layer and the barrier layer. Is smaller than the energy difference from the bottom of the conduction band at
In particular, holes can be uniformly injected into a plurality of well layers.

According to a fifth aspect of the present invention, the well layer is formed of InGaAlAs, and the barrier layer is formed of InGaAs.
It may be formed by 1As. Then, the energy difference between the first quantum level of holes in the well layer and the top of the valence band in the barrier layer is determined by the first quantum level of electrons in the well layer and the barrier layer. If the energy difference from the bottom of the conduction band is smaller than in the above case, it becomes possible to inject holes uniformly into a plurality of well layers.

Further, as described in claim 7, the wavelength of light emitted from the quantum well type structure layer is set to 1.3 μm to 1.3 μm.
When the thickness is 65 μm, the light emitting diode can be applied to an optical communication device or the like that generally uses infrared light.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A preferred embodiment of the light emitting diode according to the present invention will be described in detail. In the following description, components having substantially the same function and configuration will be denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 shows a structure of a multiple quantum well type light emitting diode 1 according to an embodiment of the present invention. Hereinafter, the structure of the multiple quantum well type light emitting diode 1 will be described in detail according to the manufacturing process.

A multiple quantum well type structure layer 12 is formed on the surface of an n-type InP substrate 11, and a p-type InP cladding layer 13 (thickness 0.5 μm) and an n-type InP block layer 14 are formed.
(Having a thickness of 0.5 μm). Next, an etching mask is formed in the crystal plane <011> direction by a lithography method.
A portion of the InP block layer 14 is removed to form a rectangular groove G. After forming the rectangular groove G, a p-type InP cladding layer 15 (thickness 1.5 μm) and a p-type InGaAs contact layer 16 (thickness 0.5 μm) are formed. Further, an AuZn contact electrode 17 and a bonding electrode 18 are sequentially formed on the surface of the p-type InGaAs contact layer 16.
Thereafter, the n-type InP substrate 11 is polished, and AuGe is
A Ni contact electrode 19 and a bonding electrode 20 are sequentially formed. After the above steps, chips are formed by a cleavage method, and devices are formed in a subsequent packaging step.

The n-type InP blocking layer 14 in the multiple quantum well type light emitting diode 1 is located between the p-type InP cladding layer 13 and the p-type InP cladding layer 15 as shown in FIG.
A pnp junction is formed in the vertical direction. With this structure, even when a predetermined voltage is applied to the bonding electrode 18 and the bonding electrode 20, a current flows through the multiple quantum well structure layer 12 in a range covered by the n-type InP block layer 14. No light emission phenomenon due to recombination of carriers is observed. Incidentally, the rectangular groove G is formed in the n-type InP block layer 14 as described above, and since a pnp junction is not formed in this region, a predetermined voltage applied to the bonding electrode 18 and the bonding electrode 20 is applied. A current flows in the region of the rectangular groove G. That is, a light emitting region ER as a region where carriers recombine is created by the rectangular groove G. And the multiple quantum well type light emitting diode 1
By adjusting the size of the rectangular groove G, the light emitting end face 21 is adjusted to a predetermined area. For example, when the multiple quantum well type light emitting diode 1 is used for optical communication,
The size of the light emitting end face 21 is set to 10 according to the diameter of the optical fiber.
If it is less than μm, the coupling efficiency with the optical fiber will be improved.

The rectangular groove G is formed in the n-type InP block layer 1 in the stripe direction of the multiple quantum well type light emitting diode 1.
4 are formed. As a result, as shown in FIG. 1, in the stripe direction of the rectangular groove G, a light absorbing area AR for absorbing light generated in the light emitting area ER and traveling in the opposite direction to the light emitting end face 21 is formed. Is formed. The light absorption region AR contributes to prevention of laser oscillation inside the device of the multiple quantum well type light emitting diode 1. The rectangular groove G may be a trapezoidal groove depending on the etching conditions, but is substantially the same in terms of function.

Next, the most characteristic multiple quantum well type structure layer 12 in the multiple quantum well type light emitting diode 1 according to the embodiment of the present invention will be described with reference to FIG. FIG. 2 is an enlarged view of the multiple quantum well type structure layer 12 shown in FIG.

On the upper surface of the n-type InP substrate 11, InGa
AlAs light guide layer 31 (composition wavelength 1.2 μm, thickness 1
0 nm) is formed, and on the upper surface thereof, I
nGaAs well layer 32 (7 nm thick), InGaAlA
The s barrier layers 33 (thickness 10 nm) are sequentially stacked.
Here, the InGaAs well layer 32 and the InGaAlA
The s barrier layer 33 has a thickness of 3 to 30 depending on the required light emission amount.
The layers are stacked. Then, the InGaAlAs light guide layer 31 is laminated on the uppermost portion, and the multiple quantum well structure layer 12 is formed.

Next, FIG. 3 shows the energy band of the multiple quantum well type structure layer 12. Energy difference δEv between the first quantum level E1h of holes in the InGaAs well layer 32 and the top of the valence band VB in the InGaAsP barrier layer 33.
Is about 107 meV, and the energy difference δEc between the first quantum level E1e of the electrons in the InGaAs well layer 32 and the bottom of the conduction band CB in the InGaAlAs barrier layer 33 is about 186 meV.

As described above, according to the multiple quantum well type light emitting diode 1 according to the embodiment of the present invention including the multiple quantum well type structure layer 12 including the InGaAs well layer 32 and the InGaAlAs barrier layer 33, the electron The energy difference δEc between the 1 quantum level E1e and the bottom of the conduction band CB in the InGaAlAs barrier layer 33 is sufficiently large,
Conversely, the energy difference δEv between the first quantum level E1h of holes (heavy holes) and the top of the valence band VB in the InGaAs well layer 32 becomes smaller. This makes it possible to prevent electrons injected at high density from overflowing from the InGaAs well layer 32, and even if the number of the InGaAs well layers 32 is increased, Thus, holes can be uniformly injected. Therefore, the multiple quantum well type light emitting diode 1 is an optical device having excellent temperature characteristics and ensuring stable operation.

The multiple quantum well type light emitting diode 1 according to the above-described embodiment has the InGaAs well layer 32 as a well layer, but may use an InGaAsP well layer or an InGaAlAs well layer instead. Good. For example, the multiple quantum well type structure layer 12 is
AsP well layer (compression strain 0.5%, composition wavelength 1.67μ)
m) and an InGaAlAs barrier layer (composition wavelength 1.2 μm)
m), the first electron
The energy difference δEc between the quantum level E1e and the bottom of the conduction band in the InGaAlAs barrier layer is about 189 meV.
And the first quantum level E1h of the hole (heavy hole)
The energy difference δEv between the InGaAlAs barrier layer and the top of the valence band in the InGaAlAs barrier layer is about 80 meV. That is, instead of the InGaAs well layer 32, InGaAsP
When a well layer is employed, the energy difference δEv increases, and in particular, the energy difference δEc significantly decreases,
Therefore, the uniformity of holes injected into the InGaAs well layer 32 is further improved.

Although the preferred embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those modifications naturally fall within the technical scope of the present invention. It is understood to belong.

For example, in the embodiment of the present invention,
Although the description has been made using the edge emitting light emitting diode having the stripe structure, the present invention is applicable to a surface emitting light emitting diode, a buried structure (BH structure) edge emitting light emitting diode, and the like. Further, the thickness and other conditions of each layer when forming the multiple quantum well type light emitting diode are not limited to the values shown in the embodiment.

[0025]

As described above, according to the present invention,
It is possible to prevent high-density injection of electrons from overflowing the well layer, and to uniformly inject holes into all the well layers even when the number of well layers is increased. Becomes possible. Thereby, the temperature characteristics of the quantum well type light emitting diode are improved, and stable operation is ensured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a structure of a multiple quantum well type light emitting diode according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a multiple quantum well type structure layer in the multiple quantum well type light emitting diode of FIG. 1;

3 is a schematic diagram showing energy bands of a well layer and a barrier layer in the multiple quantum well type structure layer of FIG.

FIG. 4 is a schematic diagram showing energy bands of a well layer and a barrier layer in a multiple quantum well structure layer of a conventional multiple quantum well light emitting diode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multiple quantum well type light emitting diode 12 Multiple quantum well type structure layer 32 InGaAs well layer 33 InGaAlAs barrier layer E1e First quantum level of electron E1h First quantum level of hole CB Conduction band VB Valence band δEv Energy difference δEc Energy difference

Claims (7)

[Claims] 1. A light emitting diode having a quantum well type structure layer in which one or more well layers and barrier layers are stacked: the well layer is formed of InGaAs;
The light emitting diode according to claim 1, wherein the barrier layer is formed of InGaAlAs. 2. The energy difference between the first quantum level of holes in the well layer and the top of the valence band in the barrier layer is determined by the first quantum level of electrons in the well layer and the conduction band in the barrier layer. The light emitting diode according to claim 1, wherein an energy difference between the light emitting diode and the bottom of the light emitting diode is smaller than that of the light emitting diode. 3. A light emitting diode having a quantum well structure layer in which one or a plurality of well layers and barrier layers are stacked: the well layer is formed of InGaAsP, and the barrier layer is formed of InGaAlAs. A light emitting diode characterized by the above-mentioned. 4. The energy difference between the first quantum level of holes in the well layer and the top of the valence band in the barrier layer is determined by the first quantum level of electrons in the well layer and the conduction band in the barrier layer. The light emitting diode according to claim 3, wherein an energy difference between the light emitting diode and the bottom of the light emitting diode is smaller than that of the light emitting diode. 5. A light emitting diode having a quantum well type structure layer in which one or more well layers and barrier layers are stacked: the well layer is formed of InGaAlAs, and the barrier layer is formed of InGaAlAs. A light emitting diode characterized by the above-mentioned. 6. The energy difference between the first quantum level of holes in the well layer and the top of the valence band in the barrier layer is determined by the first quantum level of electrons in the well layer and the conduction band in the barrier layer. The light emitting diode according to claim 5, wherein an energy difference between the light emitting diode and the bottom of the light emitting diode is smaller than that of the light emitting diode. 7. The light-emitting device according to claim 1, wherein the wavelength of light emitted from the quantum well type structure layer is 1.3 μm to 1.65 μm. A light-emitting diode according to any of the above.