JP2508649B2 - Semiconductor light emitting device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device capable of stably and continuously emitting far infrared light.

[Conventional technology]

As a semiconductor light emitting device of this type according to a conventional example, here, Applied Physics Letters (Applied Physics Letters) is used.
FIG. 4 shows an energy band diagram of the quantum well type semiconductor laser device shown in ysics Letters) vol.39 (3), 1.1981.

That is, in the energy band diagram of FIG. 4, reference numeral 7 is the ground quantum level of the electron in the quantum well,
16 is the ground quantum level of the same hole, and 13 is n-type Al
_0.48 Ga _0.52 As layer, 14 Al _0.17 Ga _0.89 As layer, 15 p-type Al
_0.48 Ga _0.52 As layer.

Therefore, in this case, Al _0.17 Ga _0.89 As layer 14 and Al _0.48
Due to the difference in energy gap between Ga _0.52 As layers 13 and 15, A
l _0.17 Ga _0.89 As Quantum level 7,1 in the conduction band and valence band of layer 14
6 is formed on each of them, and by applying a forward bias to the pn junction of the Al _0.48 Ga _0.52 As layers 13 and 15, Al _0.17 Ga _0.89 As
When electrons and holes are injected into the layer 14, the injected electrons and holes occupy the quantum ground levels 7 and 16 of the quantum well Al _0.17 Ga _0.89 As layer 14, respectively, and these electrons and holes The recombined emission of light causes laser oscillation.

[Problems to be solved by the invention]

Regarding the quantum well type semiconductor laser device in the conventional example,
Because of this structure, Al that becomes the quantum well layer
There is a problem that only laser light having an energy larger than the bandgap of the _0.17 Ga _0.89 As layer 14 can be obtained.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object of the present invention is to use a quantum well structure to stably emit far infrared light. Is to provide.

[Means for solving problems]

In order to achieve the above-mentioned object, a semiconductor light emitting device according to the present invention is capable of applying an electric field in the in-plane direction and in the direction perpendicular to the plane, and has a quantum well having a plurality of quantum levels in a conduction band, a light emitting layer, An electric field can be applied in the direction perpendicular to the plane, and a quantum well having a quantum level different from that of the light emitting layer and a current injection layer are adjacently arranged.

[Action]

Therefore, in the case of the device of the present invention, in the quantum well as the light emitting layer, by applying an electric field in the vertical direction, the quantum levels of electrons and holes are spatially separated, and recombination between electrons and holes occurs. By applying an appropriate electric field in the vertical direction to the quantum well that serves as the current injection layer, the electrons are injected into the excited quantum level of the conduction band of the light emitting layer by resonance tunneling, and The outside light can be emitted stably.

〔Example〕

An embodiment of a semiconductor light emitting device according to the present invention will be described in detail below with reference to FIGS.

1 and 2 show energy band diagrams of the device of this embodiment, and FIG. 3 is a structural explanatory view schematically showing an outline of the semiconductor light emitting device of the same.

First, in each of the energy band diagram shown in FIG. 1 and the device configuration shown in FIG.
Is an n-type AlAs layer, 2 is a non-doped Al as a current injection layer
_X Ga _1-X As layer, 3 is an AlAs layer, 4 is a non-doped GaAs layer as a light emitting layer, 5 is an n-type AlAs layer, and 6 is the AlAs layer.
The ground quantum level formed in the quantum well of the Al _X Ga _1-X As layer 2 sandwiched between 1, 3 and 7 is GaA sandwiched between the AlAs layers 3 and 5.
The ground quantum level formed in the quantum well of the s layer 4, 8 indicates the first excitation quantum level, 9 and 10 are bias power sources, and 11a and 11b are formed in the in-plane direction of the GaAs layer 4. The pair of electrodes 12 and 12 are these substrates.

In the structure of this embodiment, however, since the AlAs layer 1 is n-type, the ground quantum level 6 of the Al _X Ga _1-X As layer 2 is occupied by electrons, and the quantum well Al _X Ga _1-X
Since the energy gap between the As layer 2 and the GaAs layer 4 is different, the energy level of the ground level in the quantum well formed in the conduction band between them is also different. Then, the electron occupying the ground level 6 is GaAs
It is not tunneled to the conduction band of layer 4.

The film thickness of the AlAs layer 3 which is a common barrier between the Al _X Ga _1-X As layer 2 and the GaAs layer 4 which are quantum wells is the electron thickness between both quantum wells as described later. It is thick enough to cause tunneling.

Therefore, in the case of this embodiment configuration, as shown in FIG.
When a bias voltage is applied so that the energy levels of the ground quantum level 6 of the Al _X Ga _1-X As layer 2 and the first excited quantum level 8 of the GaAs layer 4 match, at this time, the ground quantum level The electron occupying 6 comes to occupy the first excited quantum level 8 of the GaAs layer 4 by the resonance tunneling, and this electron becomes a ground quantum level not occupied by the electron. When it transits to the position 7, it emits and emits far-infrared light having energy equal to the energy difference between the two quantum levels.

Here, the occurrence of such an emission phenomenon only between the quantum levels of the conduction bands of both quantum wells is guaranteed by the following mechanism.

That is, due to the electric field applied perpendicularly to the GaAs layer 4, the electron distribution in the conduction band is attracted to the side of the AlAs layer 3 while the holes in the valence band are attracted, as shown in FIG. The distribution is attracted in the opposite direction to the electrons, that is, toward the n-type AlAs layer 5, and thus the electron distribution and the hole distribution are spatially separated from each other, so that the recombination between electrons and holes is performed. And the electrons accumulated in the ground quantum level 7 due to the transition from the excited quantum level 8
A pair of electrodes 11a formed in the in-plane direction of the GaAs layer 4 shown in the figure,
It is removed to the outside by 11b.

Thus, from the ground quantum level 6 of the Al _X Ga _1-X As layer 2 serving as the current injection layer to the first excited quantum level 8 of the GaAs layer 4 serving as the light emitting layer, electrons are stably generated by resonance tunneling. When it is supplied, stable far-infrared light emission is continuously generated between the quantum levels 7 and 8.

In the structure of the above embodiment, the current injection layer is made of Al _X G.
Although it is formed by a _1-X As, it may be formed by GaAs similarly to the light emitting layer. In this case, by changing the quantum well widths of the current injection layer and the light emitting layer, both quantum wells are formed. Since the formed quantum levels are different, the same action and effect as those of the embodiment can be obtained.

Further, in the above-mentioned embodiment, GaAs and AlAs epitaxially grown thereon are described, but any material may be used as long as it has a similar quantum well structure. It can be used as a far-infrared laser oscillator by cleaving the opposite end faces of the above to form a Fabry-Perot resonator.

〔The invention's effect〕

As described above in detail, according to the present invention, a quantum well as a light emitting layer that can apply an electric field in the in-plane direction and in the direction perpendicular to the plane and has a plurality of quantum levels in the conduction band, and A quantum well as a current injection layer, which can apply an electric field in the vertical direction and has a quantum level different from that of the light-emitting layer, is adjacent to the quantum well, and a vertical electric field is applied to the quantum well to cause resonance between the two quantum wells. Since tunneling is caused to spatially separate the electron distribution and hole distribution in the light emitting layer, recombination between electrons and holes can be prevented, and as a result, a quantum well structure is used. It has an excellent feature that it can emit far infrared light stably and continuously.

[Brief description of drawings]

1 and 2 are energy band diagrams according to an embodiment of the semiconductor light emitting device according to the present invention, FIG. 3 is a schematic explanatory view showing the structure of the semiconductor light emitting device of the same as above, and FIG. 7 is an energy band diagram of a quantum well semiconductor laser device according to a conventional example. 1 ... n-type AlAs layer, 2 ... Al _X Ga _1-X as current injection layer
As layer, 3 ... AlAs layer, 4 ... GaAs layer as light emitting layer, 5
...... n-type AlAs layer, 6,7 ...... ground quantum level, 8 …… first excitation quantum level, 9,10 …… bias power supply, 11a, 11b …… pair of electrodes, 12 …… semiconductor substrate.

Claims (4)

(57) [Claims] 1. An electric field can be applied in the in-plane direction and in the direction perpendicular to the plane, and an electric field can be applied in the direction perpendicular to the plane, with a quantum well and a light emitting layer having a plurality of quantum levels in the conduction band. Further, the quantum well and the current injection layer, which are adjacent to the light emitting layer and have a quantum level different from that of the light emitting layer, are provided, and the light emitting layer is provided with an electrode for taking out the electrons accumulated in the ground level to the outside. A semiconductor light emitting device having the above structure. 2. The semiconductor light emitting device according to claim 1, wherein the quantum wells of the light emitting layer and the current injection layer have different barrier heights. 3. The semiconductor light emitting device according to claim 1, wherein the quantum wells of the light emitting layer and the current injection layer have the same barrier height and different well widths. 4. The semiconductor light emitting device according to claim 1, wherein the opposite ends have cleavage planes.