JPH0651251A - Optical semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] With regard to an optical semiconductor device, an extremely simple modification is made to a laminated body of semiconductor layers having a TBQ structure.
Electrons and holes excited by light irradiation can be rapidly eliminated, and high-speed repetitive operation is possible. [Structure] Material layer W ₁ and material layer W that form a well of a quantum well
Material layer B which is laminated so as to sandwich ₁ from both sides and has a thickness capable of tunneling electrons to form a barrier of a quantum well.
_2A and B _2B , and the material layer W _3A (and W _3B ) laminated in contact with at least one of the material layers B _2A and B _2B has a basic layer structure and can be present in the material layer W _3A (and W _3B ). A laminated body in which the lowest energy level of electrons in the conduction band is lower in energy than the lowest quantum level of electrons generated in the material layer W ₁ and light is generated to generate in the material layer W ₁ Of the material layers W ₁ , B _2A (and B _2B ), W _3A (and W _3B ) and an electrode for applying an electric field to the stack to promote the discharge of the generated electrons and holes To introduce.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device suitable for use in optical / optical switches, optical bistable devices, optical / optical memories and the like.

Currently, in the ultra-high speed region, for example, picoseconds (1)
From 0 ^-9 [sec] to 10 ^-12 [sec]) area to subpico [sec]
Optical switch operating in the (<10 ^-12 [sec]) range,
It is required to realize an optical bistable device, an optical / optical memory, and the like, and an optical semiconductor device called a nonlinear optical device is suitable for that, but there are still many points that need to be improved.

[0003]

2. Description of the Related Art Since light is turned on and off at an extremely high speed,
TBQ (tunneling bi-quantum)
An optical semiconductor device having a well structure has been developed (see JP-A-2-210332, if necessary). FIG. 7 is an energy band diagram of an essential part for explaining an optical semiconductor device having TBQ.

In the figure, E_VIs the top of the valence band, E_CIs
Bottom of conduction band, W₁Is the first forbidden band E_g1Have and excite
The first thickness S that allows the existence of a child₁The first substance with
Layer, B _2AAnd B_2BIs the first forbidden band E_g1Wider second
Forbidden band E_g2And has tunneling of electrons
Second thickness S₂A second material layer having W_3AAnd W_3B
Is the second forbidden band E_g2The narrower third forbidden band E_g3Have
And the first material layer W₁To second material layer B_2AOr B
_2BThird thickness S in which electrons tunneled are present₃To
A third material layer having, E₁And E₃Is the electron quantum level,
H₁And H₃Is the hole quantum level and h is the valence band
Hole, e is electron in conduction band, L_CIs the control light, L_SIs
Signal lights are shown respectively.

Specifically, the first material layer W ₁ : GaAs and the second material layer B _2A or B _2B : Al _x Ga _1-x As (x
= 0.3 to 0.5) The third material layer W _3A or W _3B : GaAs, the first material layer W ₁ forms a narrow quantum well, and the second material layer B _2A or B _2A or B _2B forms a barrier layer, the third material layer W _3A or W _3B forms a wide quantum well,
Each of these semiconductor layers forms a laminated body as shown.

In this optical semiconductor device, when the control light L _C having a wavelength resonating with the quantum level in the first material layer W ₁ which is a narrow quantum well is irradiated, the first material layer W ₁ is irradiated. Electrons and holes are excited in the light. Therefore, the absorption rate of light there is reduced, and the light cannot be absorbed. As a result, the incident signal light L _S passes and is emitted.

The electrons excited in the first material layer W ₁ tunnel through the second material layer B _2A or B _2B which is a barrier layer and the third material layer W _3A or W which is a wide quantum well.
Escape to _3B, if the irradiation of the control light L _C at the time is stopped, since the first material layer W ₁ In again light absorptance of a state capable of absorbing light rises, the signal light incident L
_S will be absorbed and will not be emitted to the outside.

As described above, in the optical semiconductor device having the TBQ structure, light absorption and recovery can be performed on the order of 10 [ps] to 1 [ps], and light can be turned on and off at high speed.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As mentioned above, TB
The Q-structure optical semiconductor device is capable of extremely high-speed optical switching.

However, when the TBQ structure is repeatedly operated at a high speed, a phenomenon in which electrons that have escaped from the first material layer W ₁ by tunneling are retained in the third material layers W _3A and W _3B appears, resulting in high speed operation. There was a problem that it would be difficult.

In order to solve the problem, an electric field is applied in a direction perpendicular to the stacking direction of the semiconductor layers, that is, in a direction parallel to the stacking plane, to facilitate the discharge of electrons and holes. Was made (if necessary, Japanese Patent Application No. 3-2650)
(See No. 9).

Explaining with reference to FIG. 7, in an optical semiconductor device for applying an electric field to a TBQ structure, an electrode for applying an electric field is formed in a direction parallel to the stacking plane in the stacked body, and the stacked body is formed. After irradiating the first material layer W ₁ with the control light L _C , the electrons of the electron-hole pairs excited in the first material layer W ₁ are second material layer B.
_2A and B _2B are tunneled to form a third material layer W _3A and W
_{After escape} to _3B , spatially separated electrons and holes are ejected toward the electrode. Therefore, the problem that carriers are retained in the third material layers W _3A and W _3B , which are wide quantum wells, is solved.

By the way, in the optical semiconductor device in which an electric field is applied to the TBQ structure, the electric field applied in the direction parallel to the stacking plane is not always uniform, and a large electric field may be locally applied. As a result, it becomes an obstacle when the electrons in the third material layers W _3A and W _3B are extracted. In order to avoid the obstacle, there is a drawback that a large electric field must be applied as compared with the case where a uniform electric field is applied.

Further, same is, since also occur for at holes in the first material layer W _1, to apply a uniform electric field in a direction parallel to the first stacking surface of the material layer W ₁ It is necessary.

In the optical semiconductor device having the TBQ structure, in addition to the drawbacks described above, there is a problem that the third material layers W _3A and W _3B absorb light when irradiated with the control light L _C. Therefore, there has been invented a device having a structure for suppressing the light absorption (see Japanese Patent Application No. 3-63385, if necessary).

FIG. 8 is an energy band diagram of an essential part for explaining an optical semiconductor device having a TBQ structure improved on the above-mentioned problem of light absorption. The same symbols as those used in FIG. They represent the same part or have the same meaning.

In the figure, E _gap1 is the energy difference between the electron quantum level E ₁ and the hole quantum level H ₁ , E _gap3 is the energy band gap at the Γ point, Γ is the Γ point, and X is Represents the X point, respectively.

This TBQ structure is characteristic in comparison with the TBQ structure seen in FIG. 7 in that the third material layers W _{3A and} W _3B are the conduction bands of the second material layers B _2A and B _2B . Of course, it has a conduction band bottom that is lower in energy than the bottom, but the lowest energy level of electrons in the conduction band that can exist in the third material layers W _{3A and} W _3B is the first. Energy level lower than the lowest quantum level of electrons generated in the material layer W ₁ of
In addition, the energy band gap of the direct transition that governs the optical transition is larger than the energy band gap of the direct transition in the _first material layer W ₁ .

Specifically, the first material layer W ₁ : GaAs and the second material layer B _2A or B _2B : Al _x Ga _1-x As (x
= 0.3 to 0.5) The third material layer W _3A or W _3B : AlAs, the first material layer W ₁ forms a narrow quantum well, and the second material layer B _2A or B _2A or B _2B forms a barrier layer, the third material layer W _3A or W _3B forms a wide quantum well,
Each of these semiconductor layers forms a laminated body as shown.

As described above, when the third material layer W _3A or W _3B in the TBQ structure is AlAs, the transition energy at the Γ point is 2.95 [eV], whereas X The transition energy at the point is 4.89 [eV]. The energy difference between the X point in the conduction band and the Γ point in the valence band is 2.16 [eV].

In the third material layer W _3A or W _{3B made} of AlAs as described above, the transition from the Γ point in the valence band to the X point in the conduction band includes an indirect process as in the case of GaAs. Although it does not happen, the difference from GaAs is that the bottom of the conduction band is the X point and the top of the valence band is the Γ point. Therefore, even if light energy of about 2.16 [eV] is supplied, almost no light absorption is exhibited.

As described above, the optical semiconductor device having the improved TBQ structure includes the second quantum well in the TBQ structure,
That is, the problem of light absorption in the third material layer W _3A or W _3B is solved by using a material having a characteristic of indirect transition such as AlAs.

By the way, the third material layers W _3A and W _3B
Similarly to the optical semiconductor device described above, the optical semiconductor device having the structure for suppressing the light absorption in the third embodiment also applies an electric field in the direction parallel to the stacked surface of the third material layers W _3A and W _3B. It has been attempted to accelerate the discharge of electrons and holes by applying the voltage.

However, in this case as well, the applied electric field is not always uniform, so that electrons are not effectively discharged, and holes in the first material layer W ₁ are also parallel to the stacking plane. There is a drawback that effective discharge cannot be performed because a uniform electric field is not applied in various directions.

The present invention makes it possible to rapidly eliminate electrons and holes excited by light irradiation by making a very simple modification to the laminated body of semiconductor layers in this kind of optical semiconductor device. At the same time, it tries to enable high-speed repetitive operation.

[0026]

According to the present invention, it is basically intended that an electric field is uniformly applied by doping a semiconductor layer stack to effectively discharge carriers. Has become.

FIG. 1 is a TBQ for explaining the principle of the present invention.
7 is an energy band diagram of a main part of an optical semiconductor device having a structure, and the same symbols as those used in FIGS. 7 and 8 represent the same parts or have the same meanings. In the figure, l _DN indicates a doping level.

In this optical semiconductor device, the second material layer
B_2AAnd B_2BIf the n-type impurity is doped into the
The electrons generated by the ping are the third material layer W_3AAnd W_3B
In the ground state of electrons in the
It In this case, the doping amount is the first material layer W
₁It has almost no effect on the electron-hole pairs, that is, the excitons.
Do not rely on doping as a guide to prevent
Generated third material layer W _3AAnd W_3BThe accumulation of electrons in
First material layer W₁To the ground level of electrons in
It is preferable to set the degree.

When the second material layers B _2A and B _2B are doped with p-type impurities, holes generated by the doping are the bases of holes in the third material layers W _3A and W _3B. A conductive layer is generated by being accumulated in the level. In this case, the doping amount in the third material layers W _3A and W _3B generated by the doping is used as a guideline so that the excitons in the first material layer W ₁ are hardly affected. It is preferable that the accumulation of holes in ( ₁₎ does not reach the ground level of holes in the _first material layer W ₁ .

In any of the above cases, by doping the second material layers B _2A and B _2B , the third material layers W _3A and W _3B become conductive layers, and when an electric field is applied, A uniform electric field is applied to the third material layers W _3A and W _3B , and good electron or hole discharge is realized.

In addition, when the first material layer W ₁ is doped with an n-type impurity, the electrons generated by the doping are accumulated in the ground level of the electrons in the third material layers W _3A and W _3B. Then, a conductive layer is generated. In this case, the doping amount in the third material layers W _3A and W _3B generated by the doping is used as a guideline so that the excitons in the first material layer W ₁ are hardly affected. It is preferable that the accumulation of electrons in ( ₁₎ does not reach the ground level of electrons in the _first material layer W ₁ .

Thus, by doping the first material layer W ₁ , the third material layers W _3A and W _3B become conductive layers, and when an electric field is applied, the third material layers W _3A and W _{3A A} uniform electric field is applied to _3B , and good electron ejection is realized.

Further, when the first material layer W ₁ is doped with p-type impurities, holes generated by the doping become the ground level of holes in the third material layers W _3A and W _3B. The conductive layer is accumulated to form the conductive layer. In this case, the doping amount in the third material layers W _3A and W _3B generated by the doping is used as a guideline so that the excitons in the first material layer W ₁ are hardly affected. It is preferable that the accumulation of holes in ( ₁₎ does not reach the ground level of holes in the _first material layer W ₁ .

Thus, by doping the first material layer W ₁ , the third material layers W _3A and W _3B become conductive layers, and when an electric field is applied, the third material layers W _3A and W _3A A uniform electric field is applied to W _3B , and good electron emission is realized.

In addition, when the third material layers W _3A and W _3B are doped with an n-type impurity, the electrons generated by the doping cause the electrons in the third material layers W _3A and W _3B to have a ground level. And the conductive layer is generated. In this case, the doping amount in the third material layers W _3A and W _3B generated by the doping is used as a guideline so that the excitons in the first material layer W ₁ are hardly affected. It is preferable that the accumulation of electrons in ( ₁₎ does not reach the ground level of electrons in the _first material layer W ₁ .

By doping the third material layers W _3A and W _3B in this manner, the third material layers W _3A and W _3B become conductive layers, and when the electric field is applied, the third material layers W _3A and W _3B become conductive layers. _A uniform electric field is applied to _3A and W _3B , and good electron ejection is realized.

When the third material layers W _3A and W _3B are doped with p-type impurities, the holes generated by the doping are the bases of the holes in the third material layers W _3A and W _3B. A conductive layer is generated by being accumulated in the level. In this case, the doping amount in the third material layers W _3A and W _3B generated by the doping is used as a guideline so that the excitons in the first material layer W ₁ are hardly affected. It is preferable that the accumulation of holes in ( ₁₎ does not reach the ground level of holes in the _first material layer W ₁ .

[0038] Thus, by doping the third layer of material W _3A and W _3B, when the third material layer W _3A and W _3B becomes conductive layer and an electric field is applied, the third material layer A uniform electric field is applied to W _3A and W _3B , and good electron ejection is realized.

TBQ to which the present invention is applied
The optical semiconductor device having the structure is not limited to the one having the standard energy band structure shown in FIG. 1, and other energy band structures, for example, the third energy band structure as described with reference to FIG. It may have an energy band structure capable of solving the problem of light absorption in the material layers W _3A and W _3B .

FIG. 2 is an essential energy band diagram for explaining the principle of the present invention for an optical semiconductor device having an energy band structure similar to that of the optical semiconductor device described with reference to FIG. , Figure 1,
The same symbols as those used in FIGS. 7 and 8 represent the same parts or have the same meanings.

Such an energy band structure has, for example, a first material layer W ₁ : GaAs and a second material layer B _2A or B _2B : Al _x Ga _{1 -x} As (x
= 0.3 to 0.5) It is realized by using the third material layer W _3A or W _3B : AlAs.

In this structure, when the second material layers B _2A and B _2B are doped with n-type impurities, the electrons generated by the doping are the same as the electrons in the third material layers W _3A and W _3B . A conductive layer is generated by being accumulated in the ground level. In this case, the doping amount of the third substance generated by the doping is used as a measure for hardly affecting the electron-hole pairs in the first material layer W ₁ , that is, the excitons. It is preferable that the Fermi level in the material layers W _3A and W _3B does not energetically reach the ground level of electrons in the first material layer W ₁ .

In this case, by doping the second material layers B _2A and B _2B , the third material layers W _3A and W _3B become conductive layers, and when the electric field is applied, the third material layers W _3A And W
_A uniform electric field is applied to _3B , and good electron ejection is realized.

When the second material layers B _2A and B _2B are doped with p-type impurities, the holes generated by the doping are the ground level of the holes in the _first material layer W _1. And a conductive layer is generated. In this case, it is preferable that the doping amount is such a low concentration that the accumulation of holes caused by the doping hardly affects the excitons in the first material layer W ₁ .

In this case, by doping the second material layers B _2A and B _2B , the first material layer W ₁ becomes a conductive layer, and when an electric field is applied, the first material layer W ₁ becomes uniform. A strong electric field is applied, and good hole ejection is realized.

In addition, when the first material layer W ₁ is doped with an n-type impurity, the electrons generated by the doping are accumulated in the ground level of the electrons in the _first material layer W ₁ and the conductive layer is formed. Is generated. As the doping amount in this case,
It is preferable to perform doping at such a low concentration that it hardly affects excitons in the first material layer W ₁ .

[0047] Thus, by doping the first layer of material W _1, the first material layer W ₁ becomes conductive layer, when an electric field is applied, the first uniform electric field to the material layer W ₁ Is added, and good hole discharge is realized.

When the first material layer W ₁ is doped with p-type impurities, holes generated by the doping are accumulated in the ground level of holes in the first material layer W _1. A conductive layer is created. As the doping amount in this case,
It is preferable to perform doping at such a low concentration that it hardly affects excitons in the first material layer W ₁ .

[0049] Thus, by doping the first layer of material W _1, the first material layer W ₁ becomes conductive layer, when an electric field is applied, uniform in the first material layer W ₁ An electric field is applied, and good hole ejection is realized.

In addition, when the third material layers W _3A and W _3B are doped with an n-type impurity, the electrons generated by the doping cause the ground level of the electrons in the third material layers W _3A and W _3B. And the conductive layer is generated. In this case, the doping amount in the third material layers W _3A and W _3B generated by the doping is used as a guideline so that the excitons in the first material layer W ₁ are hardly affected. It is preferable that the accumulation of electrons in ( ₁₎ does not reach the ground level of electrons in the _first material layer W ₁ .

[0051] Thus, by doping the third layer of material W _3A and W _3B, the third material layer W _3A and W _3B is a conductive layer, when an electric field is applied, the third material layer W _A uniform electric field is applied to _3A and W _3B , and good electron ejection is realized.

When the third material layers W _3A and W _3B are doped with p-type impurities, the holes generated by the doping become the ground level of the holes in the _first material layer W _1. The conductive layer is accumulated to form the conductive layer. In this case, it is preferable that the doping amount is such a low concentration that it hardly affects the excitons in the first material layer W ₁ .

As described above, by doping the third material layers W _3A and W _3B , the first material layer W ₁ becomes a conductive layer, and when an electric field is applied, the first material layer W ₁ becomes A uniform electric field is applied, and good hole ejection is realized.

From the above, in the optical semiconductor device according to the present invention, (1) a quantum well well is formed having a first forbidden band width and a thickness at which excitons can exist. The first material layer (for example, the first material layer W _{1 made} of GaAs) and the first material layer are laminated so as to sandwich the first material layer from both sides, and the first material layer is energetic in comparison with the bottom of the conduction band. A second material layer (eg AlG) having a high conduction band bottom and a thickness that allows electrons to tunnel to form a barrier for the quantum well.
a second material layer B _2A and B _2B ) made of aAs and a second material layer laminated so as to sandwich the first material layer between at least one of the second material layers. A third material layer (for example, a third material layer W _3A and W _{3B made of} GaAs) having a conduction band bottom that is lower in energy than the conduction band bottom of the layer is used as a basic layer structure, and A laminate in which the lowest energy level of electrons in the conduction band that can exist in the third material layer is lower in energy than the lowest quantum level of electrons generated in the first material layer. (For example, the laminated body 2), and among the electron-hole pairs generated in the first substance layer by irradiating the laminated body with light, electrons tunnel through the second substance layer to form the third substance layer. An electric field that promotes the ejection of spatially separated electrons and holes by escaping is generated in the stack. An electrode (for example, electrodes 3 and 4) formed in the vicinity of the stacked body for applying in a direction parallel to the layer surface, and a semiconductor is conductive to one of the first to third material layers. Or an impurity (for example, Si or Be) for introducing (for example, n-type or p-type) is introduced, or

(2) In the above (1), the laminated body is provided in the resonator, or

(3) The first material layer and the first material layer forming the quantum well well having the first forbidden band width and the thickness at which excitons can exist are sandwiched from both sides. A second barrier layer of the quantum well having a conduction band bottom that is energetically higher than the conduction band bottom of the first material layer and has a thickness that allows electrons to tunnel is formed. Compared to the bottom of the conduction band in the second material layer, which is laminated in contact with at least one second material layer of the material layers and the second material layer laminated so as to sandwich the first material layer. Third material layer (eg, Al
The third material layer W _3A and W _3B ) made of As is a basic layer structure, and the lowest energy level of electrons in the conduction band that can exist in the third material layer is generated in the first material layer. Energy band gap of the direct transition in the first material layer, which is lower in energy than the lowest quantum level of electrons and governs the optical transition in the third material layer. Of the second material layer in which the electrons of the electron-hole pairs generated in the first material layer by irradiating the laminate with light are second The stack is applied to apply a field parallel to the stacking plane of the stack by tunneling the electrons into the third material layer to promote the discharge of spatially separated electrons and holes. An electrode formed near the body, and a first to third object Characterized in that an impurity for making a semiconductor conductive is introduced into one material layer of the material layers, or

(4) In the above (3), the laminated body is provided in the resonator.

[0058]

By adopting the above means, a uniform electric field can be applied in the direction parallel to the stacking surface of the stacked body having the TBQ structure, so that carrier accumulation can be efficiently eliminated with a low applied electric field. Therefore, the high-speed performance of repetitive operation is significantly improved. Further, in order to realize it, n is formed in a predetermined semiconductor layer in the semiconductor layers forming the laminated body.
This is easy to carry out, since it is only necessary to dope the p-type or p-type impurities in a controlled state.

[0059]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical semiconductor device having a TBQ structure shown in the energy band diagram of FIG. 1 used for explaining the principle of the present invention will be described as a first embodiment. In the first embodiment, for example, the first material layer W ₁ : GaAs, the second material layer B _2A and B _2B : AlGaAs, and the third material layer W _3A and W _3B : GaAs are used. However, if necessary, a plurality of cycles may be repeatedly provided, or a normal quantum well structure and a bulk layer may be mixed.

Essentially important is the third material layer W
_3AAnd W_3BTo avoid the accumulation of carriers in the
To apply an electric field in the direction parallel to the stacking plane of the stack
Electrode is formed, and the first material layer is exposed to light.
W₁Of the electron-hole pairs generated in, the electron is the second
Stratum B_2AAnd B_2BTunneling the third material layer W _3A
And W_3BElectrons and holes that are spatially separated after
Is configured to be discharged toward the electrode,
Even with proper doping, carrier emission
Must be configured to enable efficient execution of
Is.

In this case, the doping is the first material layer W ₁
Alternatively, an n-type impurity such as Si may be introduced into the second material layers B _2A and B _2B or the third material layers W _3A and W _3B , or Be
It is realized by introducing p-type impurities.

FIG. 3 is a sectional side view of an essential part showing an optical semiconductor device for explaining the specific structure of the first embodiment. The same symbols as those used in FIG. 1 represent the same parts, or They have the same meaning. In the figure, 1 is a GaAs substrate, 1A is a recess for avoiding light attenuation, 2 is a laminated body, 3
Reference numerals 4 and 4 denote electrodes, 5 denotes a power source, and 6 denotes ground.

The layered body 2 shown in the drawing has a first material layer W ₁ : a GaAs layer having a thickness of 4.0 [nm], and second material layers B _2A and B _2B : Al having a thickness of 4.0 [nm].
_0.5 Ga _0.5 As layer Third material layer W _3A and W _3B : Ga having a thickness of 9.0 [nm]
It is composed of an As layer.

A process of manufacturing the optical semiconductor device of the first embodiment will be described. (1) Molecular beam epitaxial growth (molecule)
By applying the r beam epitaxy (MBE) method, the stacked body 2 is formed on the GaAs substrate 1 having a surface index of (001). The laminated body 2 is formed while doping the second material layers B _2A and B _2B with Si, and the doping concentration is 1 × 10 ¹⁰ [cm ⁻³ ].
The basic structure is grown for 50 cycles.

(2) By applying a resist process in the lithographic technique, a resist film having an opening in the electrode formation planned portion is formed. (3) Depending on the application of the vapor deposition method, the thickness, for example, 30
0 [Å] Cr film and thickness, for example 2000 [Å] Au
The films are sequentially laminated. (4) The above step (2) of immersing in a resist film stripping solution
The electrode 3 and the electrode 4 are formed by patterning the Cr / Au film formed in the step (3) by the lift-off method of peeling off the resist film formed in step 3. (5) The back surface of the GaAs substrate 1 is etched to form the recess 1A by applying a resist process in the lithography technique and a wet etching method using H ₂ O ₂ + NH ₄ OH as an etchant.

FIG. 4 is a diagram for explaining the response of the signal light when the optical semiconductor device of the first embodiment is irradiated with the control light, in which the vertical axis represents the signal light and the horizontal axis represents the signal light. I'm taking each time. In the measurement in which this data is obtained, since the exciton level between the ground quantum levels in the first material layer W ₁ is excited, both the signal light L _S and the control light Lc have a wavelength of 795 [n
m] light pulse.

According to the characteristic line shown in FIG. 4, the control light L
The signal light L passing through the optical semiconductor device at the time of being irradiated with c
The peak of _S is observed, and then it is observed that the optical absorption power of the optical semiconductor device is gradually attenuated as it is recovered.

Now, to explain this state in detail, assuming that the voltage applied in the direction parallel to the stacking surface of the stack in the optical semiconductor device is 0 [V], after irradiation with the control light Lc, The signal light L _S increases due to the absorption saturation of the exciton level. Subsequently, the electrons in the first material layer W ₁ tunnel through the second material layers B _2A and B _2B , and the third material layer W 1
_Since it flows to _3A and W _3B , the absorption of light is restored to about half within about 15 [ps]. However, at this point, the holes in the first material layer W ₁ do not completely tunnel and stay, so that the recovery is about half as shown in the figure.

On the other hand, when an electric field is applied parallel to the stacking surface, carriers can be positively discharged, and in the present invention, a uniform electric field can be applied to the stacking surface. Therefore, effective carrier discharge is performed only by applying a bias voltage of 0.5 [V].
It can be seen that the light absorption is completely recovered with a time constant of about 0 [ps].

FIG. 5 is a diagram for explaining the response of the signal light when the conventional optical semiconductor device is irradiated with the control light. Similar to FIG. 4, the vertical axis indicates the signal light and the horizontal axis indicates the response. Each has a time.

FIG. 5 is provided for comparison with FIG. 4, and is data obtained by operating an optical semiconductor device having a TBQ structure without doping as in the present invention.
Also in this case, the signal light and the control light have a wavelength of 795.
An optical pulse of [nm] was used. When no electric field is applied in the direction parallel to the stacking plane of the stack, that is, when the bias voltage is 0
In the case of [V], the bias voltage shown in FIG. 4 is 0 [V].
The same as in the above case, and it is possible to positively discharge the carriers when a bias voltage is applied.

By the way, the discharge of carriers in this case is supposed to be realized by applying a voltage of about 15 [V], but in the conventional TBQ structure, the doping as in the present invention is performed. Since the electric field is not formed, the electric field in the stacking plane is not uniform, so that the carriers cannot be discharged efficiently.

In order to avoid this problem and realize carrier discharge to the same extent as in the present invention, a voltage as high as 40 [V] must be applied as a voltage applied in the direction parallel to the laminated surface. .

In the present invention, as a structure for applying a voltage to the laminate, as described above, the electrodes 3 and 4 are simply used.
Alternatively, the p-type electrode contact region and the n-type electrode contact region may be provided in the laminated body 2 which is the base of each electrode.

As a second embodiment of the present invention, TBQ
An optical semiconductor device having a structure in which a laminated body having a structure is incorporated in a Fabry-Perot resonator will be described. Such an optical semiconductor device is realized by forming a Bragg reflector made of a semiconductor on both front and back surfaces of a laminated body to form a Fabry-Perot resonator.

The Bragg reflector is formed only on one of the front and back surfaces of the laminated body, and the other surface is formed with an anti-reflection coat by vapor deposition of, for example, SiO ₂ , and the outside is covered with an external film. The resonator may be configured by installing a mirror.

Furthermore, a resonator structure may be obtained by forming an anti-reflection coat on both front and back surfaces of the laminate and forming an external mirror made of a dielectric multilayer film.

Furthermore, instead of the Bragg reflector made of GaAs or AlGaAs, a dielectric multilayer mirror using a dielectric such as SiO ₂ and TiO ₂ can be used as the mirror constituting the resonator.

FIG. 6 is a sectional side view of an essential part showing an optical semiconductor device for explaining a specific structural example of the second embodiment.
The same symbols as those used in FIG. 3 represent the same parts or have the same meanings. In the figure, reference numerals 7 and 8 denote dielectric multilayer mirrors formed by evaporating SiO ₂ and TiO _2, for example. Dielectric multilayer mirror 7
And each layer in 8 is a quarter of the first forbidden band width E _g1
The thickness of the wavelength is set, and each of them is laminated for 12 periods.

In the second embodiment, excitons are generated in the first material layer W ₁ by the irradiation of the control light Lc, and the refractive index of the laminated body 2 changes. Therefore, the resonance condition in the Fabry-Perot resonator changes, and as a result, the signal light L _S undergoes intensity modulation. The mechanism of carrier discharge in the second embodiment is the same as that in the first embodiment, and not only the electrodes are provided but also the inside of the stack is configured to apply an electric field in the direction parallel to the stacking plane of the stack. P-type electrode contact area and n
It goes without saying that the mold electrode contact region may be provided. In the second embodiment, the structure of the resonator is of the Fabry-Perot type, but this may be replaced by the ring resonator structure.

An optical semiconductor device having the TBQ structure shown in the energy band diagram of FIG. 2 used for explaining the principle of the present invention will be described as a third embodiment.

In the third embodiment, the third material layers W _3A and W _{3B are used.}
Carriers are discharged by implementing the present invention to an optical semiconductor device in which AlAs, which is one of the materials characterized by indirect transition, is used as a material constituting It's faster. The energy band diagram in the third embodiment is exactly the same as in FIG.

In this case, the laminated body 2 comprises a first material layer W ₁ : a GaAs layer having a thickness of 2.8 [nm] and second material layers B _2A and B _2B : a thickness of 1.7 [nm]. Al
_0.5 Ga _0.5 As layer Third material layer W _3A and W _3B : Al having a thickness of 7.1 [nm]
It is composed of an As layer.

As described above, the structure of the laminated body 2 is different from those of the first and second embodiments, but other structures, manufacturing steps,
The modification of the configuration, the operation, etc. are completely the same as those of the first embodiment added to the previously described principle of the present invention.

As a fourth embodiment, in addition to the optical semiconductor device described as the third embodiment, the Fabry-Perot resonator structure or the structure in which the Bragg reflector is provided in the optical semiconductor device described as the second embodiment. Or anti
A configuration in which a reflection coat + external mirror is provided, or a configuration in which a dielectric multilayer film mirror is provided instead of the Bragg reflector is added.

In this embodiment, the structure of the laminated body 2 is the same as that of the third embodiment, and other structures, manufacturing processes, modification of the structure, operation, etc. are the same as those of the second and third embodiments. Is the same as the one with.

By the way, in each of the above-mentioned embodiments, GaAs is used.
Although the / AlGaAs system has been described, the so-called In system, such as InGaAs or InAlAs, may be used. Further, the laminated body described in the first embodiment or the third embodiment uses the semiconductor laser as an optical threshold element by inserting the semiconductor laser as a saturable absorber into the resonator of the semiconductor laser, or It can be used to generate short pulses in a lock laser.

[0088]

In the optical semiconductor device according to the present invention,
The first material layer forming the quantum well well and the first material layer sandwiched from both sides, and the second material layer forming the quantum well barrier and the first material layer sandwiched The third material layer, which is laminated in contact with at least one of the second material layers of the second material layer, has a basic layer structure, and the lowest energy level of electrons in the conduction band that can exist in the third material layer. A stack whose energy level is lower than the lowest quantum level of electrons generated in the first material layer and the stack is irradiated with light to form in the first material layer Electrons of the electron-hole pairs tunnel through the second material layer and escape to the third material layer, so that an electric field that promotes the emission of spatially separated electrons and holes is laminated in the stack. An electrode formed in the vicinity of the laminated body for applying in a direction parallel to the plane, and One of impurities for the semiconductor to conductive to material layers of the first through third material layers are introduced.

By adopting the above-mentioned structure, a uniform electric field can be applied in the direction parallel to the stacking plane of the stacked body having the TBQ structure, so that carrier accumulation can be efficiently eliminated with a low applied electric field. Therefore, the high-speed performance of repetitive operation is significantly improved. Further, in order to realize it, it suffices to dope a predetermined semiconductor layer among the semiconductor layers constituting the laminated body in a controlled state with n-type or p-type impurities, and therefore the implementation is easy. is there.

[Brief description of drawings]

FIG. 1 is an energy band diagram of an essential part of an optical semiconductor device having a TBQ structure for explaining the principle of the present invention.

FIG. 2 is an essential energy band diagram for explaining the principle of the present invention for an optical semiconductor device having an energy band structure similar to that of the optical semiconductor device described with reference to FIG.

FIG. 3 is a fragmentary side view showing an optical semiconductor device for explaining a specific structure of the first embodiment.

FIG. 4 is a diagram for explaining the response of signal light when the optical semiconductor device of the first embodiment is irradiated with control light.

FIG. 5 is a diagram for explaining a response of signal light when a conventional optical semiconductor device is irradiated with control light.

FIG. 6 is a fragmentary side view showing an optical semiconductor device for explaining a specific structural example of a second embodiment.

FIG. 7 is a main part energy band diagram for explaining an optical semiconductor device having TBQ.

FIG. 8 is an essential-part energy band diagram for explaining an optical semiconductor device having a TBQ structure, which is improved with respect to the problem of light absorption.

[Explanation of symbols]

E _V Top of valence band E _C Bottom of conduction band W ₁ First material layer E _g1 First forbidden band width S ₁ First thickness B _2A Second material layer B _2B Second material layer E _g2 Second forbidden band width S ₂ Second thickness W _3A Third material layer W _3B Third material layer E _g3 Third forbidden band width S ₃ Third thickness E ₁ Electron quantum level E ₃ electron quantum level H ₁ hole quantum level H ₃ hole quantum level h hole in valence band e electron in conduction band L _C control light L _S signal light E _{gap 1} electron quantum level E Energy difference between ₁ and hole quantum level H ₁ E _gap3 Energy band gap at Γ point Γ Γ point XX point l _DN doping level 1 GaAs substrate 1A _Recess for avoiding light attenuation 2 Laminated body 3 Electrode 4 Electrode 5 Power supply 6 Grounding 7 Dielectric multilayer film mirror 8 Dielectric multilayer film mirror

Claims (4)

[Claims] 1. A first material layer which has a first forbidden band width and a thickness at which excitons can exist and which forms a well of a quantum well, and a first material layer and a first material layer are laminated so as to sandwich them from both sides. A second material that has a conduction band bottom that is energetically higher than the conduction band bottom in the first material layer and that has a thickness that allows electrons to tunnel and forms a barrier for the quantum well. Layer and the second material layer laminated so as to sandwich the first material layer, in comparison with the bottom of the conduction band in the second material layer laminated in contact with at least one of the second material layers Basic layer structure of a third material layer having an energetically low conduction band bottom, and the lowest energy level of electrons in the conduction band that can exist in the third material layer is generated in the first material layer A stack having an energy lower than the lowest quantum level of electrons to be generated, and the stack. Of the electron-hole pairs generated in the first material layer by irradiation with light, electrons tunnel through the second material layer and escape into the third material layer, resulting in spatially separated electrons and positive electrons. An electrode formed in the vicinity of the laminated body for applying an electric field that promotes discharge of holes in a direction parallel to the laminated surface of the laminated body, An optical semiconductor device, wherein impurities for making a semiconductor conductive are introduced into one material layer. 2. The optical semiconductor device according to claim 1, wherein the laminated body is provided in the resonator. 3. A first material layer having a first forbidden band width and a thickness allowing excitons to exist so as to form a well of a quantum well, and a first material layer and a first material layer are laminated on both sides. A second material that has a conduction band bottom that is energetically higher than the conduction band bottom in the first material layer and that has a thickness that allows electrons to tunnel and forms a barrier for the quantum well. Layer and the second material layer laminated so as to sandwich the first material layer, in comparison with the bottom of the conduction band in the second material layer laminated in contact with at least one of the second material layers Basic layer structure of a third material layer having an energetically low conduction band bottom, and the lowest energy level of electrons in the conduction band that can exist in the third material layer is generated in the first material layer The energy level is lower than the lowest quantum level of the emitted electrons and in the third material layer The energy band gap of the direct transition that governs the optical transition is wider than the energy band gap of the direct transition in the first material layer, and the laminate is irradiated with light. Of the electron-hole pairs generated in the first material layer, the electrons tunnel through the second material layer and escape into the third material layer, thereby discharging the spatially separated electrons and holes. One of the first to third material layers, comprising an electrode formed in the vicinity of the laminated body so as to apply an promoting electric field in a direction parallel to the laminated surface of the laminated body. An optical semiconductor device, wherein an impurity for making a semiconductor conductive is introduced into the semiconductor device. 4. The optical semiconductor device according to claim 3, wherein the laminated body is provided in the resonator.