JP2000091626A - Super lattice semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a super lattice semiconductor light emitting device whose light emission wavelength is variable in which the fluctuation of luminous intensity can be made smaller than that of an element in a conventional example, and a high speed operation can be attained with low power consumption. SOLUTION: A super lattice semiconductor element having an intrinsic semiconductor (i) layer 15 having a super lattice structure in which barrier layers 21 and quantum well layers 22 are alternately and repeatedly laminated is provided between two electrodes 11 and 12. Each material and each thickness of the barrier layer 21 and the quantum well layer 22 is selectively set so that electrons can pass through the barrier layer 21 by a tunnel effect, and that the X level of the barrier layer 21 which is present in a Γ mini-band and the Γlevel of the quantum well layer 22 can be turned into a resonating state. At the time of impressing a reverse bias voltage to the super lattice semiconductor light emitting element, carriers are injected by making incident excitation lights, and electrons are moved from the Γ level of the quantum well layer 22 through the X level of the barrier layer 21 to the Γ level of the quantum well layer 22 in the next stage, and the electrons are recombined with holes so as to emit light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a superlattice semiconductor light emitting device having a diode type semiconductor element having a superlattice semiconductor layer and performing a light emitting operation.

[0002]

2. Description of the Related Art A conventional superlattice semiconductor light emitting device provided with a diode type semiconductor element having a superlattice semiconductor layer has a low radiative recombination energy of electrons and holes due to a quantum confined Stark effect by applying an electric field. Therefore, the emission wavelength can be monotonously shifted to the longer wavelength side. The emission wavelength can be adjusted by changing the DC bias voltage.

[0003]

In a conventional semiconductor light emitting device having a superlattice semiconductor layer, the emission wavelength can be shifted to a longer wavelength simply by applying an electric field based on the above-described quantum confined Stark effect. However, the quantum confined Stark effect has a problem that the emission wavelength is changed and the emission intensity is significantly reduced.

Also, in order to greatly change the emission wavelength, a very high electric field must be applied to the superlattice, which limits the operating speed of the device and causes an avalanche breakdown (breakdown) voltage. And it is difficult to reduce power consumption.

An object of the present invention is to solve the above-mentioned problems, and to provide a super-lattice semiconductor light-emitting device having a variable light-emitting wavelength, which has less fluctuation in light-emitting intensity than the element of the conventional example and can operate at high speed with low power consumption. Is to do.

[0006]

According to a first aspect of the present invention, there is provided a superlattice semiconductor light emitting device in which a barrier layer and a quantum well layer are alternately and repeatedly formed between two electrodes. In a superlattice semiconductor light emitting device including a superlattice semiconductor element having an intrinsic semiconductor layer having a structure, electrons can pass through each material and each thickness of the barrier layer and the quantum well layer by a tunnel effect through the barrier layer. And Γ
The X level of the barrier layer is present in the Γ mini-band formed by the conduction band, and the X level of the barrier layer and the Γ level of the quantum well layer are selected and set to be in a resonance state; When a reverse bias voltage is applied to the superlattice semiconductor light emitting device, carriers are injected by irradiating excitation light to the superlattice semiconductor light emitting device, and electrons are transferred to the 井 戸 level of the quantum well layer. Then, light is emitted by making a transition to the Γ level of the next quantum well layer via the X level of the barrier layer and recombining electrons with holes.

A superlattice semiconductor light emitting device according to a second aspect of the present invention has an intrinsic superlattice structure in which a barrier layer and a quantum well layer are alternately and repeatedly formed between two electrodes. In a superlattice semiconductor light-emitting device including a superlattice semiconductor element having a semiconductor layer, each material and each thickness of the barrier layer and the quantum well layer are set so that electrons can pass through the barrier layer by a tunnel effect. And the X-level of the barrier layer is present in the {mini-band formed by the conduction band} so that the X-level of the barrier layer and the Γ-level of the quantum well layer are in a resonance state. A carrier is injected by applying a forward voltage that is set to a breakdown state with respect to the superlattice semiconductor light emitting element, and electrons are changed from the Γ level of the quantum well layer to the X level of the barrier layer. Through the next quantum well layer Light is emitted by transition to a level and recombination of electrons with holes.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a structure of a superlattice semiconductor light emitting device provided with a superlattice semiconductor element 10 according to an embodiment of the present invention, and FIG. FIG. 3 is an energy level diagram showing an energy band structure when a reverse bias voltage is applied to the superlattice semiconductor device 10 of FIG.

In the superlattice semiconductor device of the present embodiment, barrier layers 21-0 to 21-N (hereinafter, generically referred to as 21) and a quantum well layer 22 are provided between the two electrodes 11 and 12.
-1 to 22-N (hereinafter, generically referred to as 22) are alternately stacked on the intrinsic semiconductor i-layer 15 having a superlattice semiconductor structure, each of which has an n-type cladding layer 1.
4 and 16, and the p-type cap layer 13
And a heterojunction p− sandwiched through the n-type buffer layer 17.
The superlattice semiconductor element 10 which is an in-type diode element is provided. Here, when a reverse bias voltage is applied between the electrodes 11 and 12 by the variable voltage DC power supply 30 and laser excitation light for exciting carriers is incident on the intrinsic semiconductor i-layer 15 having a superlattice semiconductor structure, the superlattice semiconductor As shown in FIG. 2, the structure is such that the X1 level exists in the barrier layer 21 inside the Γ1 miniband formed by the Γconduction band.
It is characterized in that each material and each thickness of the barrier layer 21 and the quantum well layer 22 are selected and set.

In the conventional superlattice semiconductor device, in order to shift the emission wavelength to a longer wavelength, a direct current reverse bias voltage is applied to the device to reduce the radiative recombination energy of electrons and holes. In the form, the X level suppresses the electron transport of the Γ mini-band by a slight applied electric field,
A superlattice semiconductor element having a superlattice semiconductor structure in which the X level itself participates in light emission is used.

As shown in FIG. 1, the superlattice semiconductor element 10 of the present embodiment has a flat back electrode 1 made of Au.
2 are formed, and the following layers are sequentially formed on a 300 μm thick n-type semiconductor substrate 20 made of n-GaAs in which n-type impurity ions made of Si are implanted at, for example, an implantation amount of 10 ¹⁸ / cm ³ . It is formed by being stacked from the side close to the n-type semiconductor substrate 20. (A) An n-type impurity ion made of Si has, for example, an implantation amount of 1
A 200 nm thick n-type buffer layer 17 made of n-GaAs implanted at 0 ¹⁸ / cm ³ . (B) An n-type impurity ion made of Si has an implantation amount of, for example, 5
N-Al _0.4 Ga _0.6 A implanted by × 10 ¹⁷ / cm ³
a 500 nm thick n-type cladding layer 16 made of s. (C) An intrinsic semiconductor i-layer (i-SL) 15 having a superlattice semiconductor structure and a thickness of about 600 nm. (D) The p-type impurity ions of Be are, for example, implanted at a dose of 5
N-Al _0.4 Ga _0.6 A implanted by × 10 ¹⁷ / cm ³
An n-type cladding layer 14 having a thickness of 200 nm and made of s. (E) The amount of p-type impurity ions of Be is, for example, 2
A 110 nm-thick p-type cap layer 13 made of p-GaAs implanted at a dose of × 10 ¹⁸ / cm ³ . (F) An electrode 11 made of a ring-shaped Au having an opening formed in the center in the thickness direction.

After the above lamination, the electrode 11 is formed in a ring shape by a predetermined etching method. The intrinsic semiconductor i-layer 15 is, for example, a quantum well layer 2
GaAs so that 2-N is adjacent to the n-type cladding layer 16.
s quantum well layer 2 of 11 atomic layers and a thickness of 3.1 nm
2 and a barrier layer 21 made of AlAs and having a thickness of 7 atomic layers and a thickness of 2 nm, for example, N = 100 periods (that is, 10
0 pairs). The electrode 11 is connected to the negative electrode of the variable DC power supply 30 having the reverse bias voltage Vb, and the positive electrode is connected to the electrode 12 via a load resistor 32 serving as a load circuit. As a result, a reverse bias voltage is applied between the electrodes 11 and 12 of the superlattice semiconductor element 10, and a predetermined electric field is applied.

In the superlattice semiconductor device configured as described above, electrodes 11, 1 at both ends of superlattice semiconductor element 10 are provided.
2 applies an electric field in a direction perpendicular to the superlattice, the X1 level of the barrier layer 21 and the Γ1 level of the quantum well layer 22 resonate, and the accelerated electrons are tunneled. Due to the effect, it moves in the mini band and proceeds to the next quantum well layer 22. That is, as shown in FIG.
The electron at the X1 level of 1 transitions to the X1 level of the barrier layer 21 at the next stage via the Γ1 level of the quantum well layer 22 and repeats this. Then, the electron at the X1 level of the barrier layer 21 emits light to a predetermined level of the quantum well layer 22 in the valence band Ev by radiative recombination with holes that are simultaneously photoexcited.
The emission wavelength at this time is determined by the energy of electrons and holes.

In the present invention, various materials can be used for the intrinsic semiconductor i-layer 15 which is a superlattice semiconductor layer. The material of the superlattice semiconductor layer may be a combination of three or more types. For example, the intrinsic semiconductor i-layer 15 is made of GaAs
Not only the s / AlAs superlattice semiconductor layer, but also InGaAs
/ InAlAs or a superlattice semiconductor layer such as InGaN / InAlN.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor produced the superlattice semiconductor device of the embodiment shown in FIG. In this embodiment, a streak camera is used to measure light emission.

In a GaAs / AlAs superlattice semiconductor device, (1) an optical transition between a Γ-electron level localized in a GaAs-Γ point quantum well and a GaAs-Γ hole level (type-I Transition) and (2) AlAs localized in the AlAs layer due to the quantum effect due to the X-point potential
There is an optical transition between the -X electron level and the GaAs-Γ hole level (type-II transition). The feature of the superlattice semiconductor light emitting device of the present embodiment is that, as shown in FIG.
The first GaAs-Γ electronic state forms a miniband state, and the first X electron level (X1 level) is formed in the miniband energy region. The 直流 1 electron mini-band state breaks down due to a DC electric field caused by an external DC reverse bias voltage, and when the applied voltage is around 1.0 V, as shown in FIG. 3, the first Γ1 electron level and the X1 electron level Energy resonance occurs between the phases. This Γ
It is considered that the energy resonance of -X electrons enhances the Γ-X hybrid effect and enhances the type II transition intensity.

FIG. 4 is a graph showing the energy level with respect to the reverse bias voltage in the superlattice semiconductor device 10 shown in FIG. 1, and shows the applied voltage dependence of the electric field modulation reflection (ER) signal intensity. Is represented by shading. Γ1 (X1 level) -HH1 in the figure is the first GaAs
The type I (type II) optical transition between the s-Γ (AlAs-X) electron level and the GaAs-Γ heavy hole is shown, and the numbers in parentheses are the electronic and hole levels involved in the optical transition. Are shown as multiples of the superlattice period. Type II-X1-HH in the type I superlattice, which is hardly observed in the ordinary optical spectrum
One optical transition is clearly observed. This is explained from the generation principle of the ER spectrum, and indicates that the X electron level in the type I superlattice, which has been difficult to observe until now, is clearly detected by the ER spectroscopy. Here, it should be noted that X1 (+ ／) − around 1.0 V.
HH1 transition intensity, and X1 (+
Significant enhancement of the [1/2] -HH1 transition intensity is understood as an enhancement of the type II transition intensity associated with the enhancement of the [Delta] -X hybridization effect in the energy state as shown in FIG.

FIG. 5 shows an emission wavelength spectrum of photoluminescence with respect to a DC reverse bias voltage Vb applied to the superlattice semiconductor element 10 when light is excited by a helium neon laser having a light intensity of about 1 mW. Here, EB is
A peak of the emission intensity at a wavelength of about 705 nm,
EX indicates the peak of the emission intensity near the wavelength of 697 nm, and ES indicates the peak of the emission intensity near the wavelength of 693 nm.

In the experiment of FIG. 5, the DC reverse bias voltage is changed from 2 V to 8 V in increments of 0.25 V, and is displayed shifted in the vertical direction for easy viewing.
As is apparent from FIG. 5, when the DC reverse bias voltage is 2 V, photoluminescence having a peak at a wavelength of 705 nm due to light emission from the lower end of the mini-band occurs as shown by EB. However, when the DC reverse bias voltage is slightly increased, light emission due to the X level appears at about 697 nm as shown by EX, and the DC reverse bias voltage 2.
The light emission intensity of both is reversed by 5V. At a DC reverse bias voltage of 3.5 V, light emission from the lower end of the mini-band is weak enough to be hardly observed.
As described above, the emission wavelength is dominant at the bottom of the mini-band in a low electric field. However, the application of a slight electric field hinders the traveling of carriers by the X level, and the electrons trapped in the X level emit light. And the energy of the X level is higher than the lower end of the Γ mini-band, so that the emission wavelength shifts to the shorter wavelength side. In other words, the emission wavelength can be changed by changing the DC reverse bias voltage, and a higher emission intensity can be obtained at a low voltage such as 2V.

As described in detail above, according to the present embodiment, carrier injection is performed by injecting laser excitation light in a state where a reverse bias voltage is applied to the superlattice semiconductor light emitting device using the DC power supply 30. 2, the X1 level of the barrier layer 21 is located in the # 1 mini-band shown in FIG. In this case, light is emitted by performing transition transport in the film and recombining with holes. Therefore, since the fluctuation of the light emission intensity is smaller than that of the element of the conventional example and the device can be operated with a low bias voltage, it is possible to provide a super-lattice semiconductor light emitting device with a variable light emission wavelength capable of high-speed operation with low power consumption. .

<Modification> In the above embodiment, carrier injection is performed by injecting laser excitation light while applying a reverse bias voltage to the superlattice semiconductor light emitting device using the DC power supply 30. However, the present invention is not limited to this. By applying a forward voltage that causes a breakdown state to the superlattice semiconductor light emitting device without applying a reverse bias voltage, the barrier layer can be formed in the # 1 mini-band shown in FIG. 2
1, the X1 level of the quantum well layer 22 and the X1 level of the barrier layer 21 are resonated to cause transition transport of electrons in the Γ1 miniband and recombination with holes. To emit light. The element of this modified example also has the same operation and effect as the embodiment.

In the above embodiment, GaAs / A
Although the superlattice semiconductor element 10 which is a pin type diode element having a superlattice semiconductor layer made of 1As is described, the present invention is not limited to this, and the niin shown in Tables 1 and 2 is not limited thereto. Type superlattice semiconductor element or n ⁺ −n ⁻ −n ⁺ type superlattice semiconductor element. In Tables 1 and 2, the composition ratio is not limited to this. The cladding layer may be an intrinsic semiconductor.

[0024]

[Table 1] Ni-n-type superlattice semiconductor device ―――――――――――――――――――――――――――――――― Layer or Substrate composition Thickness Impurity doping amount (/ cm ³ ), Impurity ―――――――――――――――――――――――――――――――― Cap Layer 13 n-GaAs 110 nm 2 × 10 ¹⁸ , Si ―――――――――――――――――――――――――――――――― Cladding layer 14 n −Al _0.4 Ga _0.6 As 200 nm 5 × 10 ¹⁷ , Si ―――――――――――――――――――――――――――――――― Intrinsic semiconductor i Layer GaAs / 3.4 nm 15 AlAs 5 nm Period N = 100 ―――――――――――――――――――――――――――――――― Clad layer 16 n-Al _0.4 Ga _0.6 As 500n m 5 × 10 ¹⁷ , Si ―――――――――――――――――――――――――――――――― Buffer layer 17 n-GaAs 200 nm 10 ¹⁸ , Si ―――――――――――――――――――――――――――――――― Semiconductor substrate 20 n-GaAs 300 μm 10 ¹⁸ ――――― ―――――――――――――――――――――――――――――

[0025]

[Table 2] n ⁺ −n ⁻ −n ⁺ type superlattice semiconductor element ――――――――――――――――――――――――――――――――― ― Layer or substrate composition Thickness Impurity doping amount (/ cm ³ ), impurity ―――――――――――――――――――――――――――――――― ―― Cap layer 13 n ⁺ -GaAs 110 nm 5 × 10 ¹⁸ , Si ―――――――――――――――――――――――――――――――― Cladding layer 14 n ⁻ −Al _0.4 Ga _0.6 As 200 nm 1 × 10 ¹⁷ , Si ―――――――――――――――――――――――――――――― -Intrinsic semiconductor i-layer n ^-- GaAs / 3.4 nm 1 × 10 ¹⁷ , Si 15 n ^--In _0.2 Al _0.8 As 5 nm 1 × 10 ¹⁷ , Si period N = 30 ―――――――――― ――――――――――――― ---------- cladding layer _{^{16 n - -In 0.2 Al 0.8 As}} 500nm 5 × 10 17, Si ---------------------- ―――――――――――― Buffer layer 17 n ⁺ -GaAs 200 nm 10 ¹⁸ , Si ―――――――――――――――――――――――――― ―――――――― Semiconductor substrate 20 n ⁺ -GaAs 300 μm 10 ¹⁸ , Si ―――――――――――――――――――――――――――― ――――

Note that the aperture 1 through which the excitation light is incident on the electrode 11
It is not necessary to form 1h. In this case, the excitation light is allowed to pass by forming the electrode 11 thin.

[0027]

As described above in detail, according to the superlattice semiconductor light emitting device according to the first aspect of the present invention, a barrier layer and a quantum well layer are alternately and repeatedly formed between two electrodes. In a superlattice semiconductor light emitting device including a superlattice semiconductor element having an intrinsic semiconductor layer having a superlattice structure,
The materials and thicknesses of the barrier layer and the quantum well layer are adjusted so that electrons can pass through the barrier layer by a tunnel effect, and the barrier layer is formed in a mini-band formed by a conduction band. An X level is selected and set so that the X level of the barrier layer and the Γ level of the quantum well layer are in a resonance state, and a reverse bias voltage is applied to the superlattice semiconductor light emitting device. In some cases, carriers are injected by injecting excitation light into the superlattice semiconductor light emitting device, and electrons are transferred from the Γ level of the quantum well layer to the next quantum via the X level of the barrier layer. Light is emitted by making a transition to the Γ level of the well layer and recombining electrons with holes. Therefore, since the fluctuation of the light emission intensity is smaller than that of the element of the conventional example and the device can be operated with a low bias voltage, it is possible to provide a super-lattice semiconductor light emitting device with a variable light emission wavelength capable of high-speed operation with low power consumption. .

According to a second aspect of the present invention, there is provided a superlattice semiconductor light emitting device having a superlattice structure in which a barrier layer and a quantum well layer are alternately and repeatedly formed between two electrodes. In a superlattice semiconductor light emitting device including a superlattice semiconductor element having an intrinsic semiconductor layer, electrons can pass through the barrier layer and the quantum well layer by tunnel effect through each material and thickness of the barrier layer and the quantum well layer. Thus, the X level of the barrier layer exists in the mini band formed by the conduction band, and the X level of the barrier layer and the X level of the quantum well layer.
The level is selected and set to be in a resonance state, carriers are injected by applying a forward voltage that causes a breakdown state to the superlattice semiconductor light emitting device, and electrons are injected into the quantum well layer. Light is emitted by making a transition from the level to the Γ level of the next quantum well layer via the X level of the barrier layer and recombining electrons with holes. Therefore, since the fluctuation of the light emission intensity is smaller than that of the element of the conventional example and the device can be operated with a low bias voltage, it is possible to provide a super-lattice semiconductor light emitting device with a variable light emission wavelength capable of high-speed operation with low power consumption. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a superlattice semiconductor light emitting device including a superlattice semiconductor element 10 according to an embodiment of the present invention.

FIG. 2 is an energy level diagram showing an energy band structure of the superlattice semiconductor device 10 of FIG.

FIG. 3 is an energy level diagram showing an energy band structure when a reverse bias voltage is applied to the superlattice semiconductor device 10 of FIG.

FIG. 4 is a graph showing an energy level with respect to a reverse bias voltage in the superlattice semiconductor device 10 of FIG.

FIG. 5 is a spectrum diagram showing a photoluminescence emission spectrum with respect to a DC reverse bias voltage applied to the superlattice semiconductor device 10 of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... super lattice semiconductor element, 11 and 12 ... electrode, 13 ... p-type cap layer, 14 ... p-type cladding layer, 15 ... intrinsic semiconductor i-layer, 16 ... n-type cladding layer, 17 ... n-type buffer layer, 20 ... n-type semiconductor substrate, 21-0 to 21-N: barrier layer, 22-0 to 22-N: quantum well layer, 30: variable voltage DC power supply, 32: load resistance.

Continued on the front page (72) Norifumi Egami, Inventor No. 5 Sanraya, Seiya-cho, Soraku-cho, Soraku-gun, Kyoto F-term in Environmental Research Institute for Environmentally Friendly Communications, Inc. F-term (reference) 5F041 AA12 CA05 CA36 5F073 AA74 CA04 EA29

Claims (2)

[Claims] 1. A superlattice semiconductor light emitting device including a superlattice semiconductor element having an intrinsic semiconductor layer having a superlattice structure in which a barrier layer and a quantum well layer are alternately and repeatedly formed between two electrodes. In each of the materials and thicknesses of the barrier layer and the quantum well layer, electrons are allowed to pass through the barrier layer by a tunnel effect, and the barrier layer is formed in a mini band formed by a conduction band. The X level of the layer exists and is selected and set so that the X level of the barrier layer and the Γ level of the quantum well layer are in a resonance state, and a reverse bias voltage is applied to the superlattice semiconductor light emitting device. When the voltage is applied, carriers are injected by injecting excitation light into the superlattice semiconductor light emitting device, and electrons are transferred from the Γ level of the quantum well layer to the next stage via the X level of the barrier layer. To the 層 level of the quantum well layer of A superlattice semiconductor light emitting device, which emits light by recombining electrons with holes. 2. A superlattice semiconductor light emitting device including a superlattice semiconductor element having an intrinsic semiconductor layer having a superlattice structure in which a barrier layer and a quantum well layer are alternately and repeatedly formed between two electrodes. In each of the materials and thicknesses of the barrier layer and the quantum well layer, electrons are allowed to pass through the barrier layer by a tunnel effect, and the barrier layer is formed in a mini band formed by a conduction band. The X level of the layer exists and is selected and set so that the X level of the barrier layer and the Γ level of the quantum well layer are in a resonance state. Carriers are injected by applying a certain forward voltage to cause electrons to transition from the Γ level of the quantum well layer to the Γ level of the next quantum well layer via the X level of the barrier layer; Emitted by recombination of electrons with holes A superlattice semiconductor light emitting device characterized in that it emits light.