JPH08116128A - Semiconductor quantum well optical element - Google Patents

Abstract

PURPOSE: To provide a semiconductor quantum well optical element which uses a nitrogen compound semiconductor and in which the probability of an optical transition is high regarding the semiconductor quantum well optical element such as a semiconductor laser or the like. CONSTITUTION: A semiconductor quantum well optical element uses a structure wherein a semiconductor quantum well structure composed of an In0.3 Ga0.7 N quantum well layer and of an In0.1 Al0.9 N barrier layer which sandwiches the In0.3 Ga0.7 N quantum well layer and whose band gap is higher than that of the In0.3 Ga0.7 N quantum well layer is provided as an active layer. The quantum well structure can be sandwiched by the In0.3 Ga0.7 N quantum well layer or by an AlN clad layer whose band gap is larger than that of the In0.1 Al0.9 N barrier layer. The quantum well layer can be constituted of InN, and the barrier layer can be constituted of A GaN, InAlN, AlGaInN, AlN or the like having a composition whose band gap is larger than that of the quantum well layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor quantum well optical device using a nitrogen compound.

[0002]

2. Description of the Related Art Nitrogen compound Al that emits light in the visible light region
Semiconductor optical devices such as semiconductor lasers using N, GaN, and InN are expected as a light source for the next-generation high-density magneto-optical disk, and already have InGaN as an active layer and have a wavelength of 450 n.
Diodes emitting light at m have been developed. And, like optical devices using other semiconductor materials, AlN,
Development of lasers using nitrogen compounds such as GaN and InN
In particular, it is expected that the development of optical devices such as quantum well lasers will proceed at a rapid pace.

[0003]

However, at present, these nitrogen compounds have a poor accumulation of physical property parameters, and in particular, the energy positions of the conduction band and valence band of the semiconductor determine the characteristics of the laser. It is an important parameter, but unknown at all. Therefore,
It was not known how to combine the nitrogen compound materials to obtain an optical device having excellent characteristics. The present invention
An object of the present invention is to provide a quantum well optical device using a nitrogen compound semiconductor and having a high probability of optical transition.

[0004]

In a semiconductor quantum well optical device according to the present invention, an InN quantum well layer and an InN quantum well layer are provided.
In having a forbidden band width larger than InN with N quantum well layers sandwiched therebetween
A structure including a semiconductor quantum well structure including an AlN barrier layer as an active layer is adopted.

In another semiconductor quantum well optical device according to the present invention, an InGaN well layer and AlGaIn having a band gap larger than that of InGaN sandwiching the InGaN well layer are provided.
A structure including a semiconductor quantum well structure including an N barrier layer as an active layer is adopted. In this case, the active layer may have a multi-layer structure composed of an AlGaN cladding layer sandwiching the quantum well layer and the barrier layer and having a band gap larger than those of the quantum well layer and the barrier layer.

Further, in another semiconductor quantum well optical device according to the present invention, an InGaN well layer and the InGaN well layer are provided.
AlG having a forbidden band width wider than that of InGaN sandwiching the well layer
A structure including a semiconductor quantum well structure including an aN barrier layer as an active layer is adopted. In this case, the quantum well layer and the barrier layer may have a structure in which they are sandwiched by AlGaN cladding layers having a band gap larger than those of the quantum well layer and the barrier layer.

Further, in another semiconductor quantum well optical device according to the present invention, an InGaN well layer and the InGaN well layer are provided.
InA with a forbidden band width wider than that of InGaN sandwiching the well layer
A structure including a semiconductor quantum well structure including an IN barrier layer as an active layer is adopted. In this case, the quantum well layer and the barrier layer may have a structure in which they are sandwiched by AlGaN cladding layers having a band gap larger than those of the quantum well layer and the barrier layer.

Further, in another semiconductor quantum well optical device according to the present invention, an InGaN well layer and the InGaN well layer are provided.
AlN having a forbidden band width wider than that of InGaN sandwiching the well layer
A structure including a semiconductor quantum well structure including a barrier layer as an active layer is adopted.

[0009]

In the semiconductor quantum well optical device of the present invention, the conduction band and valence electrons of the nitrogen compound semiconductor are calculated by using the "strong coupling approximation model including the cation d orbital" previously proposed by the inventors of the present invention. Determined the energy band. This model has already been published (Phys. Rev. B47,758.
8 (1993)), the conduction band and valence band energy of the compound semiconductor can be estimated very accurately. The parameters required for the calculation are as follows.

Distance between electrons (a) a = 0.3197 nm (GaN) a = 0.3115 nm (AlN) a = 0.3508 nm (InN) Forbidden band width (Eg) Eg = 3.393 eV (GaN) Eg = 6 .171 eV (AlN) Eg = 1.975 eV (InN)

FIG. 6 is a diagram for explaining the energy of the conduction band and the valence band of the nitrogen compound. This figure shows the results of calculation of the conduction band and valence band energies of AlN, GaN, and InN, which are nitrogen compounds, by the strong coupling approximation model including the cation d orbital previously proposed by the inventors. .

Nitrogen compound AlN, G which is the object of the present invention
In a conventionally known AlAs, GaAs, InAs-based compound semiconductor in which nitrogen (N) of aN, InN is arsenic (As), the energy of the conduction band gradually decreases as the forbidden band width decreases, The valence band energy increases in sequence. However, in the nitrogen compound, the energy position of GaN having an intermediate band gap is AlN, I
Compared to nN, both the conductor and the valence band are projected above.

FIG. 7 shows GaN / In which is the premise of the present invention.
It is an energy band diagram of a N / GaN quantum well structure.
The quantum well structure of the GaN / InN / GaN structure has a structure in which InN having a small forbidden band is sandwiched by GaN having a large forbidden band. As described above, the energy position of GaN is the energy of InN. Since it protrudes above the level, a potential well is formed in InN in the conduction band, but wells are formed on both sides of the GaN in the valence band.

This type is called a heterojunction Type II, and it does not operate sufficiently as an optical element because of its small emission probability. From the above, it is understood that when manufacturing an optical device using a nitrogen compound semiconductor, the material composition of the nitrogen compound semiconductor needs to be well adjusted without directly laminating the nitrogen compound itself.

[0015]

Embodiments of the present invention will be described below. (First Embodiment) FIG. 1 shows InAlN / In of the first embodiment.
It is an energy band figure of a N / InAlN quantum well structure. In the quantum well structure of this example, the energy at the base of the conduction band is −10.14 eV, the energy at the top of the valence band is −12.11 eV, and the band gap is 1.97.
In the well layer made of InV of eV, the energy of the base of the conduction band is −8.97 eV, the energy of the top of the valence band is −14.72 eV, and the band gap is 5.75 eV.
It is sandwiched between barrier layers made of _0.1 Al _0.9 N, and unlike the quantum well of the GaN / InN / GaN structure shown in FIG. 7 above, InN is a well layer in both the conduction band and the valence band. Therefore, the probability of optical transition is increased, which is extremely effective as an optical element.

This quantum well structure is used as an InN well layer, In
AlN with a forbidden band width larger than _0.1 Al _0.9 N barrier layer
(The energy of the conduction band is −8.84 eV, the energy of the top of the valence band is −15.01 eV, and the band gap is 3.67 eV).

(Second Embodiment) FIG. 2 shows In of the second embodiment.
FIG. 3 is an energy band diagram of an AlN / InGaN / InAlN quantum well structure. In the quantum well structure of this example, the energy of the ground of the conduction band is −9.09 eV, the energy of the top of the valence band is −12.05 eV, and the forbidden band width is 2.96 eV from In _0.3 Ga _0.7 N. Is sandwiched by barrier layers made of In _0.1 Al _0.9 N having a conduction band ground energy of −8.97 eV, a valence band top energy of −14.72 eV, and a forbidden band width of 5.75 eV. And the GaN previously shown in FIG.
Unlike the quantum well having the / InN / GaN structure, InN is a well layer in both the conduction band and the valence band. Therefore, the probability of optical transition is increased, which is extremely effective as an optical element.

This quantum well structure is used as In _0.3 Ga _0.7 N
AlN having a forbidden band width larger than that of the well layer and the In _0.1 Al _0.9 N barrier layer (the energy of the base of the conduction band is −8.84e
V, the energy at the top of the valence band is -15.01 eV
And can be sandwiched between clad layers having a forbidden band width of 3.67 eV).

In this laser structure, as described above, InN is a well layer in both the conduction band and the valence band, so that the probability of optical transition is high, and the barrier layer made of In _0.1 Al _0.9 N has optical confinement. It acts as a layer and serves as a standard structure of a quantum well laser (SCH structure Separate Conf
element Heterostructure L
asers) are obtained.

(Third Embodiment) FIG. 3 shows Al of the third embodiment.
It is an energy band diagram of a GaInN / InGaN / AlGaInN quantum well structure. In the quantum well structure of this example, the energy at the base of the conduction band is -9.09.
eV, the energy at the top of the valence band is 12.05 eV
In the well layer made of In _0.3 Ga _0.7 N having a forbidden band width of 2.96 eV, the base energy of the conduction band is −9.28.
eV, the energy at the top of the valence band is -12.66 eV
And a forbidden band width of 3.38 eV of Al _0.2 Ga _0.4 In
It is sandwiched by barrier layers made of _0.4 N, and unlike the quantum well of the GaN / InN / GaN structure shown in FIG. 7 above, In _0.3 Ga _0.7 N is a well layer in both the conduction band and the valence band. . Therefore, the probability of optical transition is increased, which is extremely effective as an optical element.

This quantum well structure is used as In _0.3 Ga _0.7 N
Al _0.4 Ga _0.6 N having a forbidden band width larger than that of the well layer and the AlGaInN barrier layer (the energy of the base of the conduction band is −
8.76 eV, energy at the top of the valence band is -13.
It can be sandwiched between clad layers having a band gap of 82 eV and a band gap of 5.06 eV.

(Fourth Embodiment) FIG. 4 shows Al of the fourth embodiment.
FIG. 3 is an energy band diagram of a GaN / AlGaN / AlGaN quantum well structure. In the quantum well structure of this example, the energy of the ground of the conduction band is −9.09 eV, the energy of the top of the valence band is −12.05 eV, and the forbidden band width is 2.96 eV from In _0.3 Ga _0.7 N. The well layer consisting of Al _0.2 Ga _0.8 N having a conduction band ground energy of −8.68 eV, a valence band top energy of −12.63 eV, and a forbidden band width of 3.95 eV. In contrast to the quantum well of the GaN / InN / GaN structure shown in FIG. 7, the conduction band and the valence band of In _0.3 Ga _0.7 N are well layers. Therefore, the probability of optical transition is increased, which is extremely effective as an optical element.

This quantum well structure is used as In _0.3 Ga _0.7 N
Well layer, Al _0.4 Ga _0.6 N having a forbidden band width larger than that of the Al _0.2 Ga _0.8 N barrier layer (conduction band ground energy is −8.76 eV, valence band top energy is −1)
It can be sandwiched by cladding layers having a band gap of 4.56 eV at 3.32 eV.

(Fifth Embodiment) FIG. 5 shows the Al of the fifth embodiment.
It is an energy band figure of a N / InGaN / AlN quantum well structure. In the quantum well structure of this example, the energy of the ground of the conduction band is −9.09 eV, the energy of the top of the valence band is −12.05 eV, and the forbidden band width is 2.96 eV from In _0.3 Ga _0.7 N. A well layer
The conduction band has a ground energy of −8.84 eV, the valence band has a top energy of −15.01 eV, and has a structure sandwiched by barrier layers made of AlN having a forbidden band width of 6.17 eV. GaN / In shown by FIG.
Different from the quantum well having the N / GaN structure, In _0.3 Ga _0.7 N is a well layer in both the conduction band and the valence band. Therefore, the probability of optical transition is increased, which is extremely effective as an optical element.

The structures described in the above embodiments can be easily realized by using a conventionally known crystal growth technique such as the CVD method.

[0026]

As described above, according to the present invention,
Optical element related technology in the visible light region such as a light source for high density magneto-optical disk, which is promising as a next-generation information storage device that can realize a quantum well structure with excellent optical characteristics by using a nitrogen compound. It has a large contribution in the field.

[Brief description of drawings]

FIG. 1 InAlN / InN / InAlN of the first embodiment
It is an energy band diagram of a quantum well structure.

FIG. 2 InAlN / InGaN / InA of the second embodiment
It is an energy band figure of a 1N quantum well structure.

FIG. 3 AlGaInN / InGaN / A of the third embodiment.
It is an energy band diagram of a 1GaInN quantum well structure.

FIG. 4 AlGaN / AlGaN / AlG of the fourth embodiment
It is an energy band diagram of an aN quantum well structure.

FIG. 5 is an energy band diagram of an AlN / InGaN / AlN quantum well structure of a fifth example.

FIG. 6 is an explanatory diagram of energy in a conduction band and a valence band of a nitrogen compound.

FIG. 7 is an energy band diagram of a GaN / InN / GaN quantum well structure which is a premise of the present invention.

Claims (4)

[Claims] 1. A semiconductor quantum well optical device comprising a semiconductor quantum well structure comprising an InN well layer and an InAlN barrier layer sandwiching the InN well layer and having a band gap larger than InN as an active layer. 2. An InGaN well layer and AlGa having a band gap larger than that of InGaN sandwiching the InGaN well layer.
A semiconductor quantum well optical device comprising a semiconductor quantum well structure composed of a barrier layer of N, InAlN or AlGaInN as an active layer. 3. The semiconductor according to claim 2, further comprising a structure in which the quantum well layer and the barrier layer are sandwiched by AlGaN cladding layers having a band gap larger than those of the quantum well layer and the barrier layer. Quantum well optical device. 4. A semiconductor quantum well optical device comprising, as an active layer, a semiconductor quantum well structure including an InGaN well layer and an AlN barrier layer sandwiching the InGaN well layer and having a forbidden band width larger than InGaN.