JP3337494B2 - Method of manufacturing solar cell and thin-film solar cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a chalcopyrite structure semiconductor thin film, a thin film solar cell and a light emitting device using the same.

[0002]

2. Description of the Related Art A chalcopyrite structure semiconductor is a material which is advantageous for forming a light emitting element and a solar cell because its forbidden band width can be widened from the visible region to the infrared region due to its constituent elements and its light absorption coefficient is large. is there. When manufacturing a solar cell or a light emitting element, it is essential to form a pn junction. Conventionally, when controlling the pn conductivity type of a chalcopyrite thin film, a group I element and a group III element which are constituent elements of a chalcopyrite compound are used. A method of changing the composition ratio of the element or the group II element and the group IV element has been used. For example, Cu
In the case of the InSe ₂ thin film, the composition ratio is Cu which is a group I element.
When In, which is a Group III element, is larger, it becomes n-type, and vice versa, it becomes p-type.

[0003] In this case, there are problems such as the occurrence of many lattice defects due to the deviation of the composition ratio, the precipitation of excess components, and the appearance of foreign phase compounds other than the chalcopyrite structure. It has been reported that it is difficult to control the carrier concentration and the resistivity by changing the composition ratio (R. Noufi et al., Appl. Phys. Lett., 45 (R. 19
84) p.668). In particular, most of n-type chalcopyrite semiconductor thin films due to composition deviation show high resistance, and a low resistance film has not been obtained.

[0004]

As described above, when a pn junction is manufactured using a chalcopyrite thin film manufactured by a conventional technique, as described above, a lattice defect and an excess component are precipitated due to a shift in a composition ratio, or Deterioration of electrical and optical characteristics due to the appearance of a hetero-phase compound other than the chalcopyrite structure and the like is a factor of deteriorating the efficiency or efficiency of the device. For example, an increase in the number of carrier recombination centers due to lattice defects or a heterophase compound causes a decrease in the open-circuit voltage of the solar cell and a decrease in the quantum efficiency of the semiconductor laser.

When the obtained n-type high resistance film is used, a short-circuit current is reduced in a solar cell because of a high resistance layer, and a carrier injection efficiency is reduced in a light emitting element. Therefore, this is one of the factors that cause a reduction in the conversion efficiency of the solar cell and a reduction in the luminous efficiency of the light emitting element.

The present invention has been made in consideration of the above-mentioned problems of the conventional chalcopyrite thin film, and provides a method of manufacturing a chalcopyrite-structured semiconductor thin film which does not have such a problem. It is intended to provide a device.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a group I, group III, VI
After depositing a p-type semiconductor thin film having a chalcopyrite structure composed of a group element, a group II element as a dopant is thermally diffused into the p-type semiconductor thin film, so that pn is contained in the p-type semiconductor thin film.
A method for manufacturing a solar cell, comprising forming a junction.

It is preferable that the chalcopyrite structure semiconductor thin film obtained by the above manufacturing method is heat-treated in a gas atmosphere or in a vacuum. At this time, heat treatment is preferably performed while evaporating the group VI element.

Further, the present invention is formed by depositing a II group element on I-III-VI ₂ film, a chalcopyrite structure manufacturing method of the semiconductor thin film is heat-treated.

When the heat treatment in the above-described manufacturing method is performed in a vacuum, the degree of vacuum is preferably in the range of 10 ^-9 Torr to 10 ^-2 Torr. In the case of performing the treatment in a gas atmosphere, it is preferable to use at least one of hydrogen, nitrogen, oxygen, helium, and argon.

The present invention also relates to a thin-film solar cell using the chalcopyrite-structured semiconductor thin film obtained by the above-mentioned manufacturing method for a light absorbing layer or a pn junction forming layer, or a light emitting device for use in an active layer or a cladding layer. .

[0012]

[Action]

After forming the chalcopyrite thin film, heat treatment is preferably performed while evaporating the group II element in a gas atmosphere or vacuum, or heat treatment is performed after depositing the group II element film on the chalcopyrite thin film. As a result, substitution of a group I element and a group II element in the chalcopyrite thin film occurs (hereinafter referred to as a diffusion method). I-II like this
By partially substituting the group II element at the position of the group I element in the I-VI ₂ chalcopyrite structure semiconductor thin film, excess electrons are supplied and the semiconductor film exhibits n-type conduction.

Since the ratio of the partially substituted element (dopant) to the main element as described above is usually as very small as 0.1% or less, it is necessary to maintain the composition ratio of the formed chalcopyrite thin film at the stoichiometric ratio. It is possible to prevent precipitation of lattice defects and excess components due to a composition ratio shift, or appearance of a foreign phase compound other than the chalcopyrite structure. Further, in such a manufacturing method, the carrier density or the resistivity can be controlled by controlling the deposition rate of a group II element or a group III element serving as a dopant or a compound thereof. Therefore, the degree of freedom in designing a solar cell or a light emitting element is increased, and a desired carrier density or the like required for each element can be easily obtained.

Further, when the dopant is replaced with the main element by using a diffusion method, the replacement occurs from the surface of the chalcopyrite thin film, so that the group II element is densely distributed near the surface and has a gradually dilute distribution. When such a distribution occurs,
For example, in a solar cell, an internal electric field is generated in the n-type semiconductor film, and minority carriers (holes in this case) generated near the surface are accelerated from the film surface toward the inside, that is, toward the pn junction surface. Therefore, carrier recombination in the n-type film is reduced, and a large current can be obtained.

Further, n obtained by the above-mentioned manufacturing method
By performing heat treatment (post-heat treatment) on the shaped chalcopyrite thin film, the activation rate of the substituted dopant (the ratio of the supplied electron quantity to the substituted dopant quantity) can be improved. That is, a low-resistance n-type film can be obtained with a small amount of dopant, and crystallinity deterioration such as disorder of chalcopyrite structure due to an excessive amount of impurities does not occur. Further, in the n-type chalcopyrite film formed by the diffusion method, since the shape of the distribution of the dopant in the film can be controlled by the heat treatment temperature and time, the n-type chalcopyrite film can be used for a method of optimizing the efficiency of a device such as a solar cell. . Heat treatment 10 ^-9 to 10
^{The use of} a vacuum in the range of ^-2 Torr has the advantage that foreign substances can be prevented from adhering or forming on the film surface. Also,
When the reaction is performed in a gas atmosphere, when a gas of hydrogen, helium, or argon is used, a reaction with the chalcopyrite thin film does not occur, so that formation of a foreign phase compound or a foreign substance can be prevented. In addition, when oxygen or nitrogen is used, the I-III-VI ₂ film in a region not substituted with a group II element may become p-type, which has an advantage that a pn junction can be easily formed. Furthermore, when heat treatment is performed while evaporating the group VI, VI
It is possible to prevent the group element from separating from the film.

In a solar cell or a light emitting device manufactured by using the n-type chalcopyrite thin film obtained by the above manufacturing method, the number of lattice defects, excess component precipitation, and heterophase compounds is small, so that carrier recombination centers are reduced. A solar cell with high conversion efficiency and a light-emitting element with excellent luminous efficiency can be provided. Further, since a film having a distributed carrier density can be formed, the carrier extraction efficiency of a solar cell is improved, and the carrier injection efficiency of a light-emitting element is improved, so that a high-efficiency solar cell or a high-luminance light-emitting element can be provided.

[0018]

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

FIG. 1 is a schematic sectional view showing one embodiment of the present invention. As shown in FIG. 1, a deposition source 2 of Cu, which is a main component element of chalcopyrite compound CuInSe ₂ , is provided inside.
A vacuum vessel 1 is provided which includes three evaporation sources, an In evaporation source 3, an Se evaporation source 4, and an evaporation source 5 containing Cd as a dopant. Here, reference numeral 6 denotes a heater for heating the substrate 30. Under a vacuum of about 10 ^-7 Torr,
Cu, In and Se deposition source crucibles were each 1140
C, 860 ° C., and 200 ° C. to evaporate each element and simultaneously evaporate Cd from the Cd evaporation source 5 to form CuInSe ₂ : Cd (CIS: C
d) A film was deposited. Hereinafter, this is referred to as a simultaneous vapor deposition method.
Here, glass partially covered with a CdS film and an Au film was used as the substrate 30. Using the substrate temperature during film formation as a parameter, the change in resistivity with respect to the crucible temperature of Cd is shown in FIG.
Shown in Here, the higher the Cd crucible temperature, the higher the Cd deposition rate or the amount of Cd reaching the substrate. The composition ratio of all films is Cu / In: 0.95 to 1.00.
And Se / (Cu + In) is in the range of 1 to 1.02, and the stoichiometric composition (Cu: In: Se)
= 1: 1: 2). In addition, all of the prepared films showed n-type. If the film is formed at a substrate temperature of 500 ° C., C
The resistivity is 10 ⁴ Ωcm or more regardless of the crucible temperature of d. CuInSe with stoichiometric composition without adding Cd
_Since the resistivity of the ₂ (CIS) film is about 10 ⁴ to 10 ⁵ Ωcm, it is understood that Cd does not enter the film when the film is formed at a substrate temperature of 500 ° C. When the film is formed at a substrate temperature of 400 ° C., the resistivity decreases to 10 ³ Ωcm when the temperature of the Cd crucible is set to 300 ° C. In contrast, a substrate temperature of 300
In a film formed at ° C., the resistivity of the film sharply decreases as the crucible temperature of Cd increases. From the above, it is understood that Cd is effectively incorporated into the film at a substrate temperature of about 300 ° C. during the film formation. In the case of forming a film at a substrate temperature of 300 ° C., the resistivity, that is, the carrier density can be controlled by the crucible temperature of Cd. However, from the results of X-ray diffraction, the CIS: Cd film formed at a substrate temperature of 400 ° C. or more forms a chalcopyrite structure on the glass and Au film, whereas the film formed at a substrate temperature of 300 ° C. has a chalcopyrite structure. It turned out that it did not form. Therefore,
This manufacturing method is not suitable for an amorphous substrate such as glass or a metal film. However, similarly, it was confirmed from the X-ray diffraction pattern that a chalcopyrite structure was formed on the CdS film even at a substrate temperature of 300 ° C. Therefore, the effectiveness of this manufacturing method differs depending on the substrate used, and it is necessary to pay attention to that point.

Next, an example of a production method in which a group II element is replaced with a group II element by heat treatment while evaporating a group II element near the film after preparing an I-III-VI ₂ chalcopyrite thin film will be described. . Hereinafter, this production method is referred to as a gas phase diffusion method. FIG.
Cu, In, and Se were heated at the same temperature as in the above example using a vacuum vessel 1 shown in FIG. 1 to form a CIS film at a substrate temperature of 500 ° C., and then Cd was deposited at a vacuum degree of about 10 ⁻⁷ Torr by a deposition source 5.
The substrate temperature is fixed within the range of 200 to 400 ° C. while evaporating from the substrate, followed by heat treatment. FIG. 3 shows the change in the resistivity of Cd with respect to the crucible temperature using the substrate temperature as a parameter. Here, the heat treatment time is fixed at 30 minutes. The compositions of all the heat-treated films almost satisfied the stoichiometric composition and exhibited n-type conduction. When the substrate temperature is 200 ° C., the change in the resistivity is small with respect to the change in the Cd crucible temperature, and at a Cd crucible temperature of 150 ° C., it is almost the same as the resistivity of the CIS film to which Cd is not added at about 10 ⁴ Ωcm. . Substrate temperature 3
In the case of 00 ° C., the resistivity sharply decreases with a change in the Cd crucible temperature. At a Cd crucible temperature of 300 ° C., the resistivity becomes about 10 Ωcm, which is three orders of magnitude lower than the resistivity of the CIS film. This indicates that the resistivity can be controlled by the crucible temperature of Cd. In addition, the substrate temperature 400
At ℃, the resistivity decreases rapidly up to the Cd crucible temperature of 250 ℃, but there is not much change between 250 ℃ and 300 ℃. This is considered because the amount of Cd to be replaced is saturated. From X-ray diffraction, C
d When the gas phase diffusion is performed at 300 ° C.
The half width of the peak was reduced, and deterioration of the orientation was observed. On the other hand, in the film heat-treated at a substrate temperature of 300 ° C., no deterioration in orientation was observed.

Next, after coating the deposited film of a group II element I-III-VI ₂ chalcopyrite thin film, described for the embodiment of the production process to substitute the I group element and II-group elements and heat-treated. Hereinafter, this production method is referred to as a solid phase diffusion method. Cd was vapor-deposited on the CIS film formed at a substrate temperature of 500 ° C. in the same manner as in the above embodiment, and heat-treated in an Ar atmosphere. FIG. 4 shows the change in resistivity with respect to the heat treatment temperature, using the Cd film thickness as a parameter. Here, the heat treatment time is 30 minutes each. In addition, all films showed n-type. Regardless of the Cd film thickness, at a heat treatment temperature of 400 ° C. or higher, the resistivity was almost equal to the resistivity of 10 ⁴ Ωcm of CIS to which Cd was not added.
This is probably because Cd evaporates from the film before diffusing. In the case of a Cd film thickness of 10 nm, the change in resistivity is almost eliminated at a heat treatment temperature of 300 ° C. or higher. This is because Cd is CIS at a heat treatment temperature of 300 ° C for 30 minutes.
This is considered to be due to uniform diffusion in the film. The resistivity at this time is about 10 ³ Ωcm, and CIS without Cd added
The drop from resistivity is small. In the case of a Cd film having a thickness of 50 nm, the resistance is 1 Ωcm, which is the smallest at a heat treatment temperature of 200 ° C., and the resistance increases as the heat treatment temperature increases. This is presumably because Cd diffuses deeper into the film as the heat treatment temperature increases. When the heat treatment temperature is 200 ° C,
Cd is accumulated on the surface of the CIS film. As a result of evaluating the film surface by X-ray diffraction, it was confirmed that the crystallinity of CIS was remarkably inferior. The crystallinity recovered as the heat treatment temperature increased. When the Cd film thickness was 100 nm, Cd remained on the film surface at a heat treatment temperature of 200 ° C.
Therefore, although the resistivity showed a low value of 10 ^-2 Ωcm, Cd
Is considered to be mainly due to resistance due to metal conduction. Also in this case, the resistance increases as the heat treatment temperature increases. From the above, for example, when focusing on the heat treatment temperature of 300 ° C., C
It can be seen that the resistivity can be controlled by the thickness of the d film. In this example, Ar was used as the atmosphere gas.
Similar results can be obtained by using hydrogen and helium. Also, when using nitrogen, oxygen, or a mixed gas thereof,
The film surface becomes n-type due to the diffusion of Cd, but in a deep portion in the film, CIS becomes p-type due to the incorporation of nitrogen or oxygen and exhibits rectifying characteristics.

Next, the CIS: Cd produced in the above embodiment was used.
FIG. 5 shows the result of examining the distribution of the Cd element in the film by secondary ion mass spectrometry. The solid line 7 is a Cd co-evaporation method, the dashed line 8 is a gas phase diffusion method, and the dashed line 9 is a solid phase diffusion method.
S: shows the distribution of Cd in the Cd film. In addition, two-dot chain line 10
Will be described later. Cd co-evaporation method has a substrate temperature of 300
For a film formed at 250 ° C. and a Cd crucible temperature of 250 ° C., the vapor phase diffusion method is performed at a substrate temperature of 300 ° C. and a Cd crucible temperature of 250 ° C.
The solid phase diffusion method is a result of examining a film heat-treated at 300 ° C. in an Ar atmosphere at 300 ° C. for a film heat-treated for 30 minutes in the above. It was found that Cd was uniformly distributed in the film by the Cd co-evaporation method. In the vapor phase diffusion method and the solid phase diffusion method, it was found that Cd was distributed most in the vicinity of the film surface, and was distributed in a Gaussian form or a complementary error function form in the film thickness direction. In particular, the solid phase diffusion method has a larger accumulation amount of Cd near the film thickness. From the above, the manufacturing method to be used can be selected depending on the configuration or design of the element to be manufactured.

Next, the results of heat-treating a CIS: Cd film formed by a Cd co-evaporation method and a vapor phase diffusion method at 400 ° C. for 30 minutes while evaporating Se in an Ar atmosphere will be described. Hereinafter, it is referred to as post heat treatment. In the case of the Cd co-evaporation method, in a film formed at a substrate temperature of 400 ° C. or higher, there was no change in the resistivity before and after the post heat treatment regardless of the Cd crucible temperature. On the other hand, when the substrate temperature is 300 ° C. and Cd
In the films manufactured at a crucible temperature of 200 ° C. or higher, the respective resistivity was lower by one digit than before the post heat treatment. It is considered that this is because substitution of Cd and Cu progressed in the film, and the amount of Cd supplying electrons increased (the activation rate increased). Furthermore, it was confirmed by X-ray diffraction that a chalcopyrite structure was formed. Further, among the films manufactured by the gas phase diffusion method, the film heat-treated at a substrate temperature of 200 ° C. has an increased resistance,
The resistivity of the film heat-treated at 300 ° C. or more decreased by about one digit. This is considered to be because Cd near the film surface diffuses into the film and becomes thin in the film heat-treated at a substrate temperature of 200 ° C. On the other hand, in a film formed at a substrate temperature of 300 ° C. or higher, Cd near the film surface also diffuses, but it is considered that the activation rate is further increased. Two-dot chain line 1 in FIG.
0, Cd crucible temperature 250 ° C, substrate temperature 300 ° C, 30 ° C
The Cd distribution of the film that has been further heat-treated in an Ar atmosphere at 400 ° C. for 30 minutes is shown. It can be seen that Cd is more widely distributed in the film than the film that has not been heat-treated after the broken line 8.

Next, application of the present invention to a chalcopyrite structure semiconductor thin film other than CIS will be described. Cu, I
n target is sputtered at an acceleration voltage of 1 KV,
When vapor-depositing on glass partially covered with (Indium Tin Oxide), group II element Zn is vapor-deposited simultaneously by electron beam vapor deposition (two kinds of currents of 20 mA and 30 mA at an electron acceleration voltage of 5 KV). This deposited film is heat-treated at 400 ° C. for 2 hours in a mixed gas of H ₂ S 10% and Ar 90% to obtain CuInS ₂ :
A Zn film was produced. Regardless of the current value of the electron beam, the conductivity type of the film was n-type. Resistivity is 20mA of electron beam
Film is 100 Ωcm, and 30 Ω film is 1 Ωc.
m. The resistivity was reduced by about 2 to 4 digits compared to the resistivity of 10 ⁴ Ωcm of the CuInS ₂ film to which Zn was not added. However, in the film on which Zn was deposited at an electron beam current of 30 mA, the orientation of the chalcopyrite structure (112) plane was deteriorated from the X-ray diffraction pattern as compared with the film prepared at 20 mA. On the other hand, in the film manufactured with the electron beam current of 20 mA, there was almost no change from the orientation of the film to which Zn was not added.

Next, the crucibles of the deposition sources containing Cu, Al and Se were heated at 1140 ° C., 1200 ° C. and 200 ° C., respectively, to deposit a CuAlSe ₂ film on the (100) plane GaAs crystal at a substrate temperature of 600 ° C. . The resulting film was p-type and had a resistivity of 5 Ωcm. This film was heated at a substrate temperature of 400 ° C. and a Cd crucible temperature of 300 ° C. in a vacuum of about 10 ⁻⁷ Torr.
For 1 hour. The conductivity type of the film changed to n-type, and its resistivity was 1 Ωcm. Therefore, it was found that the conduction type of the CuAlSe ₂ film can be controlled by the vapor phase diffusion method.

Hereinafter, a solar cell and a light emitting device manufactured by using the present manufacturing method will be described. FIG. 6A is an example of a solar cell manufactured using the present invention. A p-type CIS thin film 13 is formed in a predetermined region on the Mo thin film 12 covering the surface of the glass substrate 11. As a method of manufacturing the p-type CIS, there are a method of depositing two layers of CIS having different composition ratios of Cu and In, and a method of depositing a CIS film while irradiating with nitrogen ions. Next, the substrate temperature of the p-type CIS film is fixed at about 300 ° C. in a vacuum of about 10 ⁻⁷ Torr, and C
By evaporating d, substitution of Cu and Cd occurs from the CIS surface to form the n-type CIS layer 14. Further, heat treatment is performed in an Ar or nitrogen atmosphere at 300 ° C. for about 30 minutes. Note that this heat treatment is performed by evaporating the amount of Cd (amount of substitution) or p-type CIS.
It depends on the carrier density of the film, and the atmosphere gas or the heat treatment temperature or time is appropriately determined. Therefore, p-type C
Heat treatment may not be required depending on the carrier density and the film thickness of the IS film. The p formed by the above manufacturing method
A transparent electrode 15 such as ZnO or ITO is formed on the n-homo junction CIS film. FIG. 6B shows the band structure of this element. In the n-type CIS film, Cd
, The surface has an n-type low resistance, that is, the Fermi level exists near the conduction band of the CIS, and the Fermi level gradually approaches the valence band. In the case of such a band structure, since an internal electric field is generated even in the n-type CIS film, minority carriers (holes in this case) generated near the film surface by light irradiation are accelerated to a depletion layer. In the case of a normal pn junction, minority carriers near the film surface that are recombined can be taken out, so that the amount of current obtained increases. Therefore, high efficiency can be achieved.
In addition, there is a structure shown in FIG. On the CdS film 16 formed on the glass 11 coated with the transparent electrode 15, Cd is co-deposited at a substrate temperature of 300 ° C. by the same manufacturing method as in the above embodiment to form an n-type CIS film 14 having a thickness of 0.1 to 0.1. After producing about 0.2 μm, the CIS film 17 to which Cd is not added is formed to a thickness of 0.2 μm.
Deposit about 5 to 2.0 μm. After heat-treating the produced device at 300 ° C. for 3 hours in the air, Au or Pt is deposited to form an electrode 18. In the case of this element, the CIS film becomes p-type by heat treatment in air, and the CIS: Cd film near the CdS film changes from n-type to electrically neutral i-type. Since this i-layer is sandwiched between the n-type CdS layer and the p-type CIS layer, an internal electric field is generated smoothly as a whole. Therefore, the carriers generated in the i-layer are accelerated and taken out from the electrode. By optimizing the film thickness of the i-layer based on the light absorption coefficient of CIS and the carrier density of p-type CIS and n-type CdS, carrier recombination is small and carriers generated by light irradiation can be efficiently taken out. Becomes Therefore, the efficiency of the solar cell can be improved.

FIG. 8A shows an embodiment of a visible light emitting device manufactured by using the present invention. A low-resistance p-type CuAlSe ₂ film 20 is grown on a GaAs substrate 19, and a high-resistance p-type CuAlSe ₂ film 21 is grown thereon. SiO ₂ or Al leaving a part on the high resistance p-type CuAlSe ₂ film
It is covered with an insulator film such as ₂ O ₃ which has low reactivity with the CuAlSe ₂ film. Then, while evaporating Cd, Cd is diffused from the portion of the CuAlSe ₂ film where the insulator film is not covered, and an n-type CuAlSe ₂ film 22 is formed. Finally, an Al or Au electrode 23 is provided on both surfaces. In this device, the resistance near the surface of the CuAlSe ₂ film where Cd diffusion occurs is reduced, and gradually increased in the film thickness direction. This Cd diffusion film thickness is optimized by the substrate temperature and time when Cd is diffused, or by heat treatment after Cd diffusion, and a pn junction is formed in the p-type high-resistance CuAlSe ₂ film. Light is emitted by injecting carriers into the pn junction. At this time, the carriers are injected only from the surface of the CuAlSe ₂ : Cd film surface where the Cd is diffused and the resistance becomes n-type. Therefore, luminous efficiency can be improved. There is also a structure shown in FIG. Ga
N-type CuAlS by simultaneous Cd deposition on As substrate 19
e ₂ : After the Cd film 22 is formed, a high-resistance p-type CuAlS
An e ₂ film 21 is deposited, and a low-resistance p-type CuAlSe ₂
The film 20 is manufactured. An insulating film such as SiO ₂ is formed on a part of the laminated film in the form of a stripe in a manner opposite to the above-described embodiment,
Cd is diffused while being evaporated to form an n-type CuAlSe ₂ film 22. Then, the SiO ₂ film is removed, and Au or Pt is deposited on the SiO ₂ film to form an electrode 23. In this configuration, the light emitting layer is composed of n-type CuAlSe ₂ and high-resistance p-type C
It becomes a pn junction formed by a uAlSe ₂ film. Carrier injection is performed from a low-resistance p-type CuAlSe ₂ film under the electrode. At this time, Cd-diffused CuAlSe ₂ : Cd
Since the region becomes n-type, carriers are injected into the pn junction without diverging. Therefore, the luminous efficiency can be improved.

[0028]

As is apparent from the above description,
The present invention can produce a chalcopyrite structure semiconductor thin film in which the composition of the constituent elements has a stoichiometric ratio, and controls electrical properties such as pn conductivity type and carrier density. A highly efficient thin-film solar cell and light-emitting device used can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for mixing a group II element into a thin film of I-III-VI ₂ chalcopyrite structure according to one embodiment of the present invention.

FIG. 2 is a diagram showing a change in resistivity with respect to a crucible temperature of Cd when Cd is simultaneously deposited.

FIG. 3 is a diagram showing a change in resistivity with respect to a crucible temperature of Cd when a heat treatment is performed while evaporating Cd.

FIG. 4 is a diagram showing a change in resistivity with respect to a Cd film thickness when a heat treatment is performed after a Cd thin film is formed.

FIG. 5 is a diagram showing the distribution of Cd in a CuInSe ₂ film by secondary ion mass spectrometry.

FIG. 6A is a cross-sectional structural view of a solar cell according to one embodiment of the present invention, and FIG. 6B is a diagram illustrating a band structure.

FIG. 7 is a sectional structural view of a solar cell according to one embodiment of the present invention.

FIG. 8A is a cross-sectional structural view of a light-emitting element according to one embodiment of the present invention, and FIG. 8B is a cross-sectional structural view of a light-emitting element according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Cu evaporation source 3 In evaporation source 4 Se evaporation source 5 Cd evaporation source 6 Heater for substrate heating 7 Distribution of Cd in CuInSe ₂ : Cd film produced by simultaneous evaporation method 8 Gas phase diffusion method CuInSe ₂ prepared by: Cd CuInSe produced by the distribution 9 solid phase diffusion method Cd in the film _2: Cd CuInSe produced in distributed 10 vapor phase diffusion method Cd in the film _2: after the heat treatment of the Cd film Cd Distribution 11 Glass substrate 12 Mo thin film 13 p-type CuInSe ₂ film 14 n-type CuInSe ₂ : Cd layer 15 transparent electrode 16 CdS film 17 CuInSe ₂ film 18 upper electrode 19 GaAs substrate 20 low-resistance p-type CuAlSe ₂ film Reference Signs List 21 High-resistance p-type CuAlSe ₂ film 22 n-type CuAlSe ₂ : Cd film manufactured by the present invention 23 electrode 30 substrate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-56171 (JP, A) JP-A-52-146582 (JP, A) JP-A-50-61182 (JP, A) JP-A Sho 53- 84582 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21 / 203,21 / 363,31 / 04 C23C 14/00-14/58

Claims (6)

(57) [Claims] 1. A p-type semiconductor thin film having a chalcopyrite structure comprising a group I, a group III, and a group VI element is deposited, and then a group II element as a dopant is thermally diffused into the p-type semiconductor thin film. A method for manufacturing a solar cell, wherein a pn junction is formed in a thin film. 2. The method for manufacturing a solar cell according to claim 1, wherein after depositing the semiconductor thin film, a heat treatment is performed while evaporating a group II element or a compound containing the element. 3. A method for manufacturing a solar cell, comprising heat-treating a chalcopyrite structure semiconductor thin film manufactured by the method according to claim 2 in a gas atmosphere or in a vacuum. 4. The method according to claim 3, wherein the heat treatment is performed while evaporating the group VI element. 5. The solar cell according to claim 1, wherein any one of the heat treatments is performed in a vacuum in a range of 10 ⁻⁹ Torr to 10 ⁻² Torr. Manufacturing method. 6. The method according to claim 1, wherein at least one of hydrogen, nitrogen, oxygen, helium, and argon is used as an atmosphere gas for any heat treatment or for any heat treatment. A method for manufacturing any of the solar cells.