JPH05206514A - Light-emitting element - Google Patents

Abstract

PURPOSE:To obtain a charge-injection type light-emitting element using a p-n junction, which can be used for optical communication, a self-light emission type display, a light source, an optical integrated circuit and the like using porous silicon. CONSTITUTION:In order to accomplish a charge-injection type light-emitting element in which p-n junction is used, it is necessary that holes are injected from a p-type semiconductor and electrons are injected from an n-type semiconductor into a light-emitting layer, and they are recoupled on the light-emitting layer. Therefore, porous silicon is formed on a p-type and n-type single crystal silicon substrate, and amorphous silicon carbon, containing fine crystal having the conductive type different from single crystal silicon, is deposited on the porous silicon. As a result, a charge-injection type light-emitting element, in which p-n junction is used, can be obtained for the first time using a silicon semiconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device which can be used for optical communication, a self-luminous display, a light source, an optical integrated circuit, etc., and more particularly, a charge injection type light emitting device (L
ED).

[0002]

2. Description of the Related Art Since a silicon semiconductor is an indirect transition semiconductor, it is considered impossible to manufacture a light emitting device. Therefore, a conventional light emitting device using a pn junction is III-V.
Group II compound semiconductors, Group II-VI compound semiconductors, and IV-VI
It was made of a genus compound semiconductor. However, compared with compound semiconductors, silicon semiconductors have more resources, have a high single-crystal manufacturing technology, and can supply large-area ones at low cost. In addition, highly integrated and highly reliable logic, which is difficult to realize with current compound semiconductors with high device design and fabrication technology,
Realization of a light emitting element using silicon, and finally a charge injection type light emitting element using a pn junction that can be finally applied to a laser, due to advantages such as calculation, driving, and light receiving element can be formed on the same substrate. Was longed for. But 1990
Year, L. T. It was shown by Canham that porous silicon obtained by anodizing single crystal silicon in a hydrofluoric acid solution exhibits strong photoluminescence at room temperature (Applied).
Physics Letters 57, 1990,
p. 1046). This indicates that there is a possibility that a light emitting device can be realized by using silicon, and thereafter, active research has been conducted on the mechanism of this photoluminescence generation. However, since a good pn junction with porous silicon was formed and no material capable of producing an LED was found, a pn junction type charge injection type light emitting device using this porous silicon was not realized.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to realize a light emitting element using silicon, which has never existed in the past, and in particular, an LED which emits light by injecting charges using a pn junction. ..

[0004]

SUMMARY OF THE INVENTION The present invention is p-type or n-type.
A charge injection type light emitting device using a pn junction composed of an amorphous silicon carbon film containing porous silicon formed on a single crystal silicon substrate and microcrystals having a conductivity type different from that of the single crystal silicon.

[0005]

In order to realize the charge injection type light emitting device using the pn junction, holes are injected from the p type semiconductor into the light emitting layer and electrons are injected from the n type semiconductor, and the light emitting layer is recombined. is necessary.

The present inventors have found that p-type or n-type single crystal silicon substrates (plane orientations (111) and (100), resistivity 0.
Porous silicon, which is a light emitting layer, is formed on the positive electrode (05 to 50 Ωcm) by anodizing method (ethyl alcohol: hydrofluoric acid (48% aqueous solution) = 0: 1 to 10: 1 in an aqueous solution and monocrystalline silicon is applied to the anode. Connect an electrode such as platinum to the cathode, 1mA / c
m ^{2 to} 200 mA / cm ² current for 30 seconds to 10 minutes, and then n
Band gap (2.0
~ 2.4 eV) and high conductivity (10 ^-2 to 10 ¹ S / c)
It has been found that a good pn junction can be obtained by depositing an amorphous silicon carbon film containing microcrystals having m) on porous silicon.

In order to produce a good pn junction that emits light from an LED, not only the method for producing porous silicon (resistivity of the substrate, anodization method, etc.) but also particularly porous silicon and microcrystals are contained. It is very important to optimize the deposition conditions of the amorphous silicon carbon film containing microcrystals so as not to damage the interface characteristics of the amorphous silicon carbon film.

The inventors of the present invention have conducted intensive studies on these. As a result, when a p-type single crystal silicon substrate was used, p-type single crystal silicon having plane orientations (111) and (100) or a resistivity of 0.1 to 40 Ωcm was used, and ethyl alcohol: hydrofluoric acid (48% Aqueous solution) = 0.1-1:
By making porous silicon in a 5: 1 aqueous solution at a current density of 5 to 50 mA / cm ² and anodization time of 1 to 5 minutes and further immersing it in a KOH solution for 3 minutes to remove the impurity layer on the surface of the porous silicon, Holes can be satisfactorily injected from the p-type single crystal silicon substrate into the porous silicon layer,
It was found that a porous silicon layer that can be manufactured can be manufactured. Also, electron cyclotron resonance plasma CVD
Method, gas pressure 0.01 to 0.05 Torr, substrate temperature 150 to 350 ° C., input power 200 to 350 W, S
iH4: CH4: PH3: H2 = 1: 1: 0.01: 2
By forming an amorphous silicon carbon film containing fine crystals at 00: 1: 3: 0.01: 200,
The deposition conditions of the amorphous silicon carbon film containing the microcrystals which allows the electrons to be favorably injected onto the porous silicon from the amorphous silicon carbon film containing the microcrystals which are n-type semiconductors have been found. As a result, a charge injection type light emitting device using a pn junction was realized.

Further, in the case of the n-type single crystal silicon substrate, the conditions for producing the porous silicon layer from which the electrons can be favorably injected into the porous silicon layer from the n-type single crystal silicon substrate are:
When producing porous silicon, the same conditions are used as when a p-type single crystal silicon substrate is used, except that light must be applied, and non-crystal containing a p-type semiconductor is used. The deposition condition of the amorphous silicon carbon film containing fine crystals that allows holes to be well injected into the porous silicon from the amorphous silicon carbon film is n-type by using B2 H6 instead of PH3 as the source gas. It has been found that the deposition conditions for the amorphous silicon carbon film containing microcrystals are the same.

Regarding the conditions under which the above-mentioned LED can be manufactured, there are many unclear reasons why the LED cannot be manufactured outside this range. However, if you describe below the reason that is currently known, regarding the resistivity,
This is because if the resistance exceeds 40 Ωcm, the resistance of the substrate becomes high, and the electric charge cannot be well injected from the substrate to the porous silicon. With respect to the ratio of ethyl alcohol and hydrofluoric acid, if the ratio of ethyl alcohol: hydrofluoric acid is less than 0.1: 1, porous silicon cannot be made uniform because of bubbles generated during anodization. This is because when the current density exceeds 50 mA / cm ² , silicon electropolishing gradually begins to occur. Further, when the gas pressure of the electron cyclotron resonance plasma CVD method is less than 0.01 Torr, the underlying porous silicon is damaged by the etching effect. Also, if it exceeds 0.05 Torr, the plasma is not stable and it becomes impossible to produce amorphous silicon carbon containing fine crystals. Regarding the substrate temperature, if the temperature is lower than 150 ° C, it becomes impossible to produce amorphous silicon carbon containing fine crystals, and the temperature is 350 ° C.
This is because the surface state of the porous silicon changes and light emission is stopped in the above.

In principle, a light emitting device can be realized by using p-type or n-type amorphous silicon carbon instead of the amorphous silicon carbon film containing p-type or n-type microcrystals. However, p-type or n-type amorphous silicon carbon has a bandgap and conductivity of 2.0 eV, and an amorphous silicon carbon film having a conductivity of 10 ⁻⁵ S / cm and microcrystals is formed. Since the bandgap and the electrical conductivity are lower than those in the comparative example, it is considered that the emission luminance is lowered. Furthermore, in principle, a light emitting element can be realized by using silicon containing p-type or n-type microcrystals or p-type or n-type amorphous silicon. However, as compared with amorphous silicon containing microcrystals and amorphous silicon carbon containing microcrystals, it is not possible to increase the conductivity in a place where the band gap is wide, and thus the emission brightness is naturally lowered. it is conceivable that.

[0012]

EXAMPLE An example of the present invention will be described below with reference to FIG.
Description will be given with reference to (a), (b), FIG. 2 (a), (b), FIG. 3, FIG. 4, FIG. 5 (a), and (b).

Example 1 First, a case of using a p-type single crystal silicon substrate. FIG. 1A is a structural diagram of a light emitting device of the present invention when a p-type single crystal silicon substrate is used. Au is deposited on the back surface of the p-type single crystal silicon substrate ((100) surface, resistivity 3 to 5 Ωcm) to make ohmic contact. Next, a mask is made with wax except for the portion to be made porous, and then, as shown in FIG.
Immerse in a solution of ethyl alcohol: hydrofluoric acid (48% aqueous solution) = 1: 1 as shown in FIG. Using a constant current power source, a platinum electrode is attached to the cathode side and a single crystal silicon substrate is attached to the anode side. In this way, the current is 30 mA / cm ²
It was fixed to and anodized for about 3 minutes. Then, it was immersed in a KOH solution for 3 minutes to remove the impurity layer on the surface of the porous silicon. Next, the wax on the surface was thawed with an organic solvent, washed with pure water, and then placed in an electron cyclotron resonance plasma CVD apparatus to deposit an amorphous silicon carbon film containing n-type microcrystals at 150 Å. Deposition conditions are gas pressure 0.05To
rr, input power 300 W, SiH4: CH4: PH3:
H2 = 1: 2: 0.01: 200, substrate temperature 300 ° C
Is. Next, using an electron beam evaporation apparatus, 600 liters of indium tin oxide (ITO), which is a transparent electrode, was deposited.

FIG. 3 shows the voltage-current characteristics of the element thus produced. It can be seen that good rectification characteristics are obtained, in which the forward direction is obtained when a negative voltage is applied to the ITO side and the reverse direction is obtained when a positive voltage is applied. As a result, a good pn junction is formed between the p-type single crystal substrate and the porous silicon and the amorphous silicon carbon containing n-type microcrystals, and the p-type single crystal substrate is directly converted into porous silicon. It can be seen that the holes are also well injected with electrons from the amorphous silicon carbon containing n-type crystallites.

FIG. 5A shows an emission spectrum when a negative voltage of 10 V is applied to the ITO side. The emission wavelength was about 600 to 800 nm.

Example 2 Next, a case where an n-type single crystal silicon substrate was used. FIG. 1B is a structural diagram of a light emitting device of the present invention when an n-type single crystal silicon substrate is used. Ohmic contact is made by evaporating Al on the back surface of the n-type single crystal silicon substrate ((100) surface, resistivity 3 to 5 Ωcm). Next, the portion to be made porous is masked with a wax and immersed in a solution of ethyl alcohol: hydrofluoric acid (48% aqueous solution) = 1: 1. Using a constant current power supply, attach a platinum electrode to the cathode side,
An n-type silicon substrate is attached to the anode side. In this way, the current was fixed at 30 mA / cm ² and anodization was performed for about 3 minutes. At this time, as shown in FIG. 2 (b), the surface on which the porous silicon was formed was irradiated with a tungsten lamp light to perform anodization. Then, it was immersed in a KOH solution for 3 minutes to remove the impurity layer on the surface of the porous silicon. After that, the wax was removed with an organic solvent, washed with pure water, placed in an electron cyclotron resonance plasma CVD apparatus, and an amorphous silicon carbon film containing p-type microcrystals was deposited by 150 l. The deposition conditions are gas pressure of 0.05 Torr, input power of 300 W,
SiH4: CH4: B2 H6: H2 = 1: 2: 0.0
The temperature is 1: 200 and the substrate temperature is 300 ° C. Next, using an electron beam evaporation device, 600 liters of ITO was deposited.

FIG. 4 shows the voltage-current characteristics of the element thus produced. It can be seen that good rectification characteristics are obtained, in which the positive direction is applied to the ITO side and the reverse direction is applied when the negative voltage is applied. As a result, a good pn junction is formed between the n-type single crystal substrate and the porous silicon and the amorphous silicon carbon containing p-type microcrystals, and electrons are transferred from the n-type single crystal substrate to the porous silicon. It is also understood that holes are well injected from the amorphous silicon carbon containing p-type microcrystals.

FIG. 5B shows an emission spectrum when a positive voltage of 10 V is applied to the ITO side. The emission wavelength was about 500 to 750 nm.

[0019]

According to the present invention, a pn junction type charge injection type light emitting device using porous silicon, which has not been realized in the past, can be realized. The LED of the present invention is 30
Since it can be manufactured by a low temperature process of 0 ° C. or less, if the element of the present invention is covered with wax after manufacturing the logic, operation, drive, light receiving element, etc., the logic, operation, drive Since the light emitting element and the logic, operation, driving, light receiving element and the like can be monolithically incorporated without destroying the light receiving element and the like, there are many advantages. Silicon is expected to enter the fields of optical communication, self-luminous displays, light sources, optical integrated circuits, etc.

[Brief description of drawings]

FIG. 1A is a structural diagram of a light emitting device of the present invention when a p-type single crystal silicon substrate is used, and FIG. 1B is a structure of a light emitting device of the present invention when an n-type single crystal silicon substrate is used. It is a figure.

2A and 2B are views for explaining the anodization method.

FIG. 3 is a diagram showing voltage-current characteristics of a light emitting element.

FIG. 4 is a diagram showing voltage-current characteristics of a light emitting element.

5 (a) and 5 (b) are diagrams showing an emission spectrum when a positive voltage of 10 V is applied to the ITO side.

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[Procedure amendment]

[Submission date] May 19, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

The inventors of the present invention have conducted intensive studies on these. As a result, when a p-type single crystal silicon substrate was used, p-type single crystal silicon having plane orientations (111) and (100) or a resistivity of 0.1 to 40 Ωcm was used, and ethyl alcohol: hydrofluoric acid (48% Aqueous solution) = 0.1-1:
By making porous silicon in a 5: 1 aqueous solution at a current density of 5 to 50 mA / cm ² and anodization time of 1 to 5 minutes and further immersing it in a KOH solution for several seconds to remove the impurity layer on the surface of the porous silicon, Holes can be satisfactorily injected from the p-type single crystal silicon substrate into the porous silicon layer,
It was found that a porous silicon layer that can be manufactured can be manufactured. Also, electron cyclotron resonance plasma CVD
Method, gas pressure 0.001 to 0.005 Torr , substrate temperature 150 to 350 ° C., input power 200 to 350
W, SiH4: CH4: PH3: H2 = 1: 1: 0.0
By forming an amorphous silicon carbon film containing microcrystals at 1: 200 to 1: 3: 0.01: 200, the amorphous silicon carbon film containing microcrystals that is an n-type semiconductor is porous. The deposition conditions of an amorphous silicon carbon film containing fine crystals that enable good injection of electrons on silicon have been found. As a result, a charge injection type light emitting device using a pn junction was realized.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

Regarding the conditions under which the above-mentioned LED can be manufactured, there are many unclear reasons why the LED cannot be manufactured outside this range. However, if you describe below the reason that is currently known, regarding the resistivity,
This is because if the resistance exceeds 40 Ωcm, the resistance of the substrate becomes high, and the electric charge cannot be well injected from the substrate to the porous silicon. With respect to the ratio of ethyl alcohol and hydrofluoric acid, if the ratio of ethyl alcohol: hydrofluoric acid is less than 0.1: 1, porous silicon cannot be made uniform because of bubbles generated during anodization. This is because when the current density exceeds 50 mA / cm ² , silicon electropolishing gradually begins to occur. Further, the gas pressure of the electron cyclotron resonance plasma CVD method is less than 0.001 Torr , because the underlying porous silicon is damaged by the etching effect. Also, if it exceeds 0.005 Torr , the plasma is not stabilized and it becomes impossible to produce amorphous silicon carbon containing fine crystals. Regarding the substrate temperature, if the temperature is lower than 150 ° C, it becomes impossible to produce amorphous silicon carbon containing fine crystals, and if the temperature is 350 ° C.
This is because if C or higher, the surface state of the porous silicon changes and no light is emitted.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

In principle, a light emitting device can be realized by using p-type or n-type amorphous silicon carbon instead of the amorphous silicon carbon film containing p-type or n-type microcrystals. However, p-type or n-type amorphous silicon carbon has a bandgap and conductivity of 2.0 eV, and an amorphous silicon carbon film having a conductivity of 10 ⁻⁵ S / cm and microcrystals is formed. The bandgap and the conductivity are both lower than those of the conventional products, so the emission brightness is reduced.
It Furthermore, in principle, a light emitting element can be realized by using silicon containing p-type or n-type microcrystals or p-type or n-type amorphous silicon. However, as the amorphous silicon containing microcrystals and the amorphous silicon carbon containing microcrystals in both amorphous silicon cannot increase the conductivity in a place where the band gap is wide, the emission brightness is naturally lowered.
To do.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Example 1 First, a case of using a p-type single crystal silicon substrate. FIG. 1A is a structural diagram of a light emitting device of the present invention when a p-type single crystal silicon substrate is used. Au on the back surface of the p-type single crystal silicon substrate ((100) surface, resistivity 3 to 5 Ωcm) ,
Alternatively, Al is deposited to make ohmic contact. Next, the portion to be made porous is masked with a wax and immersed in a solution of ethyl alcohol: hydrofluoric acid (48% aqueous solution) = 1: 1 as shown in FIG. 2 (a). Using a constant current power source, a platinum electrode is attached to the cathode side and a single crystal silicon substrate is attached to the anode side. In this way the current is 3
It was fixed at 0 mA / cm ² and anodized for about 3 minutes. Then, it was immersed in a KOH solution for 3 seconds to remove the impurity layer on the surface of the porous silicon. Next, the wax on the surface was thawed with an organic solvent, washed with pure water, and then placed in an electron cyclotron resonance plasma CVD apparatus to deposit an amorphous silicon carbon film containing n-type microcrystals at 150 Å. The deposition conditions are as follows : gas pressure 0.005 Torr , input power 300 W, SiH4:
CH4: PH3: H2 = 1: 2: 0.01: 200, and the substrate temperature is 300.degree. Next, using an electron beam vapor deposition apparatus, indium tin oxide (IT
O) was deposited at 600Å.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Example 2 Next, a case where an n-type single crystal silicon substrate was used. FIG. 1B is a structural diagram of a light emitting device of the present invention when an n-type single crystal silicon substrate is used. An n-type single crystal silicon substrate ((100) surface, resistivity 3 to 5 Ωcm) was formed on the back surface with Al or
Deposits Au—Sb to form an ohmic contact.
Next, except for the portion to be made porous, a mask is made with wax, and ethyl alcohol: hydrofluoric acid (48% aqueous solution) = 1:
Immerse in the solution of 1. Using a constant current power source, a platinum electrode is attached to the cathode side and an n-type silicon substrate is attached to the anode side. In this way, the current was fixed at 30 mA / cm ² and anodization was performed for about 3 minutes. At this time, as shown in FIG. 2 (b), the surface on which the porous silicon was formed was irradiated with a tungsten lamp light to perform anodization. Then add 3 to KOH solution
It was immersed for 2 seconds to remove the impurity layer on the surface of the porous silicon. Then, the wax is removed with an organic solvent, washed with pure water, and then placed in an electron cyclotron resonance plasma CVD apparatus to form an amorphous silicon carbon film containing p-type microcrystals.
50Å accumulated. The deposition conditions are gas pressure of 0.05 Torr,
Input power 300W, SiH4: CH4: B2 H6: H2
= 1: 2: 0.01: 200, and the substrate temperature is 300 ° C. Next, using an electron beam vapor deposition device, 600 liters of ITO
Deposited.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

Claims (1)

[Claims] 1. A pn junction comprising a porous silicon formed on a p-type or n-type single crystal silicon substrate and an amorphous silicon carbon film containing microcrystals having a conductivity type different from that of the single crystal silicon. Charge injection type light emitting device.