JPH077181A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To enhance the emission efficiency by employing a PIN structure where an I-type amorphous SiC, i.e., an active emission layer, is sandwiched between P-type and N-type semiconductors with positive and negative electrodes being provided, respectively, on P and N sides and determining the band gap of the I-type amorphous SiC depending on the visible region. CONSTITUTION:When a power supply 8 is connected between the rear electrode 2 and the transparent electrode 6 of a semiconductor light emitting element 1 and positive and negative voltages are applied, respectively, to P layer 5 and N layer 3, electrons 9 are injected from the N layer 3 into the I layer 4 and holes 10 are injected from the P layer 5 into the I layer 4. The electrons 9 injected into the I layer 4 are coupled again with the holes 10 to emit light. In Fig. (2), hnu represents the energy of emitted light, (h) is Planck constant, and nu is the frequency of light. The minority carriers can be increased through double injection of holes and electrons from P and N layers, resulting in the remarkable enhancement of emission efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a junction structure for semiconductor light emitting devices.

[0002]

2. Description of the Related Art Conventionally, semiconductor light emitting devices include a light emitting diode based on the principle of injection electroluminescence and a semiconductor laser diode, and an emission center element in which carriers in the semiconductor accelerated by a high electric field are added to the semiconductor. There is a thin-film electroluminescence device and the like that emits light upon collision excitation with.

[0003]

A conventional light emitting diode or semiconductor laser diode is formed of a PN junction doped with impurities to a degenerate state. Therefore, the minority carriers that recombine to emit light are either electrons or holes, and the emission efficiency is relatively low.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a semiconductor light emitting device capable of increasing the luminous efficiency.

[0005]

The present invention has a PIN structure in which an I-type amorphous SiC is used as a light emitting active layer, and both ends thereof are sandwiched by P-type and N-type semiconductors, and a positive side is provided on the P side.
The semiconductor light emitting device is characterized in that an electrode for applying a negative voltage is provided on the N side, and the band gap of the I-type amorphous SiC is determined corresponding to the visible light region.

Further, according to the present invention, a transparent conductive plate is coated on a transparent substrate 7, the conductive plate is separated using a laser to form a transparent electrode 6, and the transparent electrode 6 is connected to a high frequency power supply device. In the electric field between the pair of electrodes thus prepared, a gas containing C ₂ H ₂ gas and SiH ₄ gas is mixed in a mixed gas ratio X.

[0007]

[Equation 2]

However, by supplying 50 to 63% by plasma chemical vapor deposition, P-type amorphous SiC and I having a band gap of 2.29 to 2.64 eV are formed on the transparent electrode 6.
Type amorphous SiC and N type amorphous SiC
Is formed in this order, each element is separated by using a laser, and the metal electrode 2 is vapor-deposited on each element.

Further, the present invention is characterized in that a plurality of PIN structures are laminated, and the band gaps of the I-type amorphous SiC of each PIN structure are different from each other.

Further, according to the present invention, the forbidden band width is 2.29-2.
PI in which 64 eV of I-type amorphous SiC is used as a light emitting active layer and both ends thereof are sandwiched by P-type and N-type semiconductors
Each electrode for applying a positive voltage to the P side and a negative voltage to the N side has an N structure, and at least the electrode provided on the N-type semiconductor is a transparent electrode. The forbidden band widths m1 and m2 are selected to be smaller than the forbidden band width m2 of the I-type amorphous SiC.
The larger the band gap of the I-type amorphous SiC in the range of 5 V, the higher the voltage is selected, and the current density is 1 to 10 ² mA /
It is a semiconductor light emitting device characterized by being selected to be cm ² .

Further, according to the present invention, the forbidden band width is 2.29 to 2.6.
4 eV I-type amorphous SiC 42, 45, 48; 1
7 and 21 are active layers for light emission, and both ends thereof are P-type and N-type semiconductors 41, 44, 47, 16, 20; 43, 4
PIN structure 40a sandwiched between 6, 49, 18 and 22
40b, 40c; 14a, 14b, a plurality of PIN structures 40a, 40b, 40c; 14a, 14b are stacked, and each stacked PIN structure 40a, 40b, 40
c; 14a and 14b, the band gaps E ₀₁ , E ₀₂ , and E ₀₃ of the respective I-type amorphous SiC are changed so as to increase sequentially toward the downstream in the light emission direction, and the PIN structures 40a and 40b. , 40c; electrodes 15 and 1 for applying a positive voltage to the P side and a negative voltage to the N side of 14a and 14b.
9 and 23, the N-type semiconductors 49 and 2 of the PIN structures 40c and 14b having the minimum bandgap of I-type amorphous SiC are provided.
The remaining electrodes 15, 19 other than the electrode 23 provided on the second electrode
Is made transparent, and each PIN structure 40a, 40b, 40c;
P-type and N-type semiconductors 14a and 14b 4
1,44,47,16,20; 43,46,49,1
Forbidden band widths m1 and m3 of 8 and 22 are the PIN structures 40
a, 40b, 40c; 14a, 14b I-type amorphous SiC 42, 45, 48; 17, 21 forbidden band width m2
It is selected to be smaller than
The larger the band gap of the I-type amorphous SiC is, the higher voltage is selected and the current density is 10 to 10 ³ mA /
It is a semiconductor light emitting device characterized by being selected to be cm ² .

[0012]

According to the present invention, by having a PIN structure and using the I-type semiconductor as the active layer for light emission, the injection of minority carriers into the light emitting region can be increased, and the light emission efficiency is significantly improved. can do.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows an amorphous silicon carbide (hereinafter abbreviated as a-SiC) according to an embodiment of the present invention.
It is a cross-sectional view of a semiconductor light emitting device 1 using a semiconductor. The semiconductor light emitting device 1 includes a back electrode 2 made of aluminum and N
A-SiC semiconductor layer (hereinafter abbreviated as N layer) 3, I-type a-SiC semiconductor layer (hereinafter abbreviated as I layer) 4, P-type a
-SiC semiconductor layer (hereinafter abbreviated as P layer) 5, a transparent electrode 6 made of tin oxide, and a transparent glass substrate 7 are laminated.

A power source 8 is connected between the back electrode 2 and the transparent electrode 6 of the semiconductor light emitting device 1 so that the P layer 5 is positive and the N layer 3 is positive.
When a negative voltage is applied to the electrons, electrons 9 are injected from the N layer 3 to the I layer 4 and holes 10 are injected from the P layer 5 to the I layer 4, as shown in FIG. Electrons 9 injected into I layer 4
Then, the holes 10 are recombined to emit light. The forbidden band width of the N layer 3 is indicated by a reference sign m1, and the forbidden band width of the I layer 4 is indicated by a reference sign m.
2, the band gap of the P layer 5 is indicated by reference numeral m3. Figure 1 (2)
Where hν represents the energy of light emitted, h is the Planck's constant, and ν is the frequency of light. As is apparent from FIG. 1 (2), m2> m1 and m2> m3.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor light emitting device 1. The semiconductor light emitting device 1 has a first step a for forming the transparent electrode 6, a second step b for forming the P layer 5, a third step c for forming the I layer 4, and a fourth step for forming the N layer 3. It is manufactured through a step d, a fifth step e for separating the elements, and a step f for vapor-depositing the back surface electrode 2.

First, in the first step a, a glass substrate 7 coated with a transparent conductive plate is separated by a laser scriber 11 to form a transparent electrode 6. Second step b
Is performed on the P layer 5, the third step c is performed on the I layer 4, and the fourth step d is performed on the N layer by the plasma chemical vapor deposition method. SiC is vapor-grown using methane gas (CH ₄ ) as a hydrogen-based gas and monosilane gas (SiH ₄ ) as a hydrogen silicate gas. In the fifth step e, after the PIN layer is formed, each element is separated by the laser scriber 13. In the sixth step f, aluminum is mask-deposited as the back surface electrode 2 on each of the separated elements.

A method of manufacturing such a light emitting diode is as follows.
Unlike the conventional method of manufacturing a light emitting diode, there is an advantage that a semiconductor layer having a large area and excellent uniformity of characteristics can be formed by utilizing the characteristics of the integration technology and the vapor phase growth method.

FIG. 3 is a diagram showing the relationship between the applied voltage and the current density of the semiconductor light emitting device 1, and shows each line when the values of the forbidden band width E ₀ of the I layer a-SiC are different from each other. . Table 1 shows a description of each element.

[0019]

[Table 1]

The lines L1a and L1b shown in FIG.
The relationship between the applied voltage and the current density of the IN type amorphous solar cell is shown.

As is clear from FIG. 3, a used for the I layer
-The emission color changes depending on the value of the forbidden band width E ₀ of SiC.
Due to the high resistance of the layer, the forward rising voltage increases as the emission color changes from red to green. The applied voltage in the vicinity of the operating point shown by the black dots in FIG. 3 is from several volts to at most 10 and several volts, which is an order of magnitude higher than the operating voltage of about 200 volts of the electroluminescence panel currently used. It is also a feature of the semiconductor light emitting device of the present invention that it is low and a semiconductor integrated circuit can be used for a drive circuit used for a display. The raw material gas (CH ₄ , C ₂ H ₄ ) in Table 1 is the hydrocarbon gas used for forming the semiconductor thin film.

FIG. 4 is a diagram showing the relationship between the injection current density and the emission intensity of the semiconductor light emitting device 1, in which the device temperature of the semiconductor light emitting device 1 is changed and each of the above relationships is shown by a line. Semiconductor light emitting device 1 used in this experiment
Has a mixed gas ratio X represented by the following first formula of 55% and a bandgap of the I layer of 2.58 eV.

[0023]

[Equation 3]

The element temperatures corresponding to the respective lines in FIG. 4 are shown in Table 2.
Shown in.

[0025]

[Table 2]

From FIG. 4, the emission intensity of the semiconductor light emitting device 1 is
It can be seen that the injection current density increases almost in proportion to the square. This is a clear confirmation of the injection type light emission due to the double injection of electrons and holes as described above. In the experiment, the light emission due to the double injection was recognized in the device temperature of the semiconductor light emitting device 1 in the range of 300 ° K to 110 ° K.

FIG. 5 shows the reciprocal of the emission intensity and the element temperature, which is 10
The relationship with the value of 00 times is shown, each line shows the difference when the injection current density is changed, and Table 3 shows the value.

[0028]

[Table 3]

It can be seen from FIG. 5 that the emission intensity changes with temperature, and the emission intensity increases as the temperature decreases. This is because the probability of non-radiative recombination becomes smaller as the temperature becomes lower than the probability of radiative recombination.

FIG. 6 shows the emission spectrum distribution of electroluminescence of the semiconductor light emitting device 1 together with the photoluminescence. The mixed gas ratio X of the first formula is changed so that each of the distributions is indicated by each line. Shows. Details are shown in Table 4.

[0031]

[Table 4]

The peak energies in Table 4 are the energies for the peaks of the respective wavelengths and are calculated from the second equation.

E = hc / λ (2) where h is Planck's constant, c is the speed of light, and λ is the wavelength.
Further, X in Table 4 is the raw material gas ratio calculated from the first equation.

Lines L19 to L21 shown in FIG. 6 indicate wavelengths corresponding to the energy of the forbidden band width of the I layer a-SiC in which the gas ratio X is different from each other. X corresponding to each line
The values of are shown in Table 5.

[0035]

[Table 5]

As is apparent from FIG. 6, the emission color can be controlled by designing different gas mixture ratios for the I layer.

FIG. 7 is a sectional view and an energy level diagram of a semiconductor light emitting device 40 according to a second embodiment of the present invention. The semiconductor light emitting device 40 includes a first PIN layer 40a and a second PIN layer 40.
b, the third PIN layer 40c. The first PIN layer 40a includes a first P layer 41, a first I layer 42, and a first
The second PIN layer 40b includes the N layer 43 and the second PIN layer 40b is the second P layer 4
4, a second I layer 45, and a second N layer 46. Also the third
The PIN layer 40c includes a third P layer 47, a third I layer 48, and a third N layer.
It consists of layer 49. Reference numeral E ₀₁ in Figure 7 represents the band gap of the 1I layer, reference numeral E ₀₂ is the first 2I layer, reference numeral E ₀₃
Indicate the band gaps of the third I layer. The forbidden band widths E ₀₁ , E ₀₂ , E ₀₃ have different sizes, and
It is provided so as to have the relationship represented by the formula.

E ₀₁ > E ₀₂ > E ₀₃ (3) By providing the forbidden band widths E ₀₁ , E ₀₂ , and E ₀₃ as described above, the long wavelength light emitted from the 3I layer is absorbed on the way. The first P layer 4 without separating into pairs of electrons and holes
It is devised so as to reach the left side of FIG.

This is because the relationship between the energy width and the wavelength is as shown in the first equation, and the wider the band gap, the less the light on the long wavelength side is absorbed.

FIG. 8 shows the relationship between the injection current density and the emission intensity of the semiconductor light emitting device 40. The line L22 shown in FIG. 8 has an I layer width of 500Å and one PIN layer, the line L23 has an I layer width of 1000Å and one PIN layer, and the line L24 has an I layer of 500Å and two PIN layers.
In the case of a layer, the line L25 shows the relationship between the injection current density and the emission intensity when the PIN layer has three layers. As is clear from FIG. 8, the I layer width is 500Å
As for the single-layer structure and the two-layer structure and the three-layer structure with the I layer width of 500 Å, the latter multi-layer structure has a light emission intensity higher by almost one digit or more. The reason for this is
This is because both the increase in the efficiency of double injection of carriers into the I layer and the improvement in the internal electric field distribution are effective, and such an order of magnitude improvement in light emission efficiency is observed.

FIG. 9 is a sectional view of a semiconductor light emitting device 14 according to the third embodiment of the present invention. The semiconductor light emitting device 14 is composed of a first PIN layer 14a and a second PIN layer 14b. The first PIN layer 14a includes a transparent electrode 15, a P layer 16,
The second PIN layer 14b includes an I layer 17 and an N layer 18, and the second PIN layer 14b includes a transparent electrode 19, a P layer 20, an I layer 21, and an N layer 2.
2 and the back electrode 23. A glass substrate 24 is arranged below the transparent electrode 15 of the semiconductor light emitting element 14 in FIG. 9.

The I layer 17 of the first PIN layer 14a emits green light 2
6 has a characteristic of emitting light, and the I layer 2 of the second PIN layer 14b
1 has a characteristic of emitting red light 27. The first PIN layer 14a having the above-mentioned characteristics is formed on the glass substrate 24.
The second PIN layer 14b is disposed at a position away from the glass substrate 24, and pulse power supplies 25 and 26 are applied to each layer as shown in FIG.

At this time, by controlling any one of the magnitude of the peak value of the applied pulse voltage, the pulse width and the duty ratio, the semiconductor light emitting element 14 on the outer side of the lower side of the glass substrate 24 in FIG. When visually observed at a place on a straight line in the direction of light emission, the luminescent color appears to change in color tone in five stages of red, orange, yellow, yellow-green and green.

FIG. 10A is a sectional view of the semiconductor light emitting device 28 of the fourth embodiment of the present invention. The point to be noted in this embodiment is that the P layer 29 has a superlattice structure as described later. FIG. 10 (2) is an enlarged cross-sectional view of the P layer 29 having a superlattice structure, and FIG. 10 (3) is an energy level diagram of the semiconductor light emitting device 28. The configuration of the semiconductor light emitting device 28 of the present embodiment will be described with reference to FIGS. 10 (1), 10 (2) and 10 (3). The semiconductor light emitting device 28 includes a back surface electrode 30, an N layer 31, an I layer 32, a P layer 29, a transparent electrode 33, and a glass substrate 34. Of the above-described structure, the structure other than the P layer 29 is the same as that of the first embodiment, and therefore the description thereof is omitted.

The P layer 29 has a structure in which a plurality of P-type a-SiCs 36 and 37 having different forbidden band widths are alternately laminated. Therefore, as shown in FIG. 10C, the energy level becomes a rectangular pulse shape, and the barrier layer 38
And the well layer 39 are formed. Such a structure is called a superlattice structure.

FIG. 11 shows the relationship between the injection current density and the emission intensity for the semiconductor light emitting device 28 having the P layer 29 having the superlattice structure and the semiconductor light emitting device having a single P layer having no superlattice structure. It is the figure which showed. In the P layer 29, an a- having a bandgap of 1.99 eV which is P-type doped with boron is formed.
SiC is used as the well layer 39, a-SiC having a band gap of 2.36 eV that is not doped with boron is used as the barrier layer 38, and is repeatedly laminated for 6 cycles with a thickness of 25Å and 15Å, respectively. Further, the single P layer is a single layer of a-SiC having a band gap of 1.99 eV and a thickness of 150 Å. The line L27 in FIG. 11 is P of the superlattice structure.
The line L28 is for a semiconductor light emitting device having a layer 29, and the line L28 is for a semiconductor light emitting device having a single P layer 28.

As is apparent from FIG. 11, the P layer having the superlattice structure increases the emission intensity by about 3 times as compared with the case without the superlattice structure. This is because the apparent forbidden band width of the P layer 29 having the superlattice structure is about 2.1 eV, and the light emission from the I layer is effectively extracted to the outside. By using such a superlattice structure P layer, the luminous efficiency can be increased.

[0048]

As described above, according to the present invention, an I-type semiconductor is used as a light emitting active layer, and P-type and N-type semiconductors are joined to both ends of the active layer to form a PIN structure, and a positive side is provided on the P side. Since an electrode for applying a negative voltage is provided on the N side, a small number of carriers can be increased by double-injecting holes from the P layer and electrons from the N layer, respectively, and increase the luminous efficiency. It is possible to rise significantly.

Further, the method for manufacturing a semiconductor light emitting device of the present invention is a vapor phase growth method using a gas obtained by adding a minute amount of a gas such as B ₂ H ₆ or PH ₃ to a gas obtained by mixing a hydrocarbon gas and a hydrogen silicate gas. Therefore, a large-area and uniform semiconductor layer can be formed.

In particular, according to the present invention, C ₂ H ₂ gas and SiH ₂ are generated in the electric field between the pair of electrodes connected to the high frequency power supply device.
Gases containing ₄ gases are used to form P, I and N type amorphous SiC layers in this order on the transparent electrode 6 by a plasma chemical vapor deposition method at a mixed gas ratio X of 50 to 63%. Thus, by using the high frequency electric field in this way, the substrate temperature required for depositing the layer of amorphous SiC can be made relatively low, less energy is required, and such a high frequency electric field is used. As a result, the excellent effect that each such layer can be formed in a relatively short time is achieved. Furthermore, according to such a manufacturing method of the present invention, an excellent effect that a total dry process by a so-called vacuum part system is possible, and thus the number of steps can be reduced and mass productivity can be improved is also achieved. It

Further, according to the present invention, since the P, I and N type SiC have an amorphous structure, the transparent substrate 7
Can be any material, for example glass and other materials, the superior effect of being able to form a layer of uniform composition over a large area is also achieved.

[Brief description of drawings]

FIG. 1 is a sectional view and energy order diagram of a semiconductor light emitting device 1 according to an embodiment of the present invention.

FIG. 2 is a diagram showing a method of manufacturing the semiconductor light emitting device 1.

FIG. 3 is a diagram showing a relationship between an applied voltage and a current density of the semiconductor light emitting device 1 under different manufacturing conditions.

FIG. 4 is a diagram showing a relationship between an injection current density and a light emission intensity of the semiconductor light emitting device 1.

FIG. 5 is a diagram showing a relationship between a light emission intensity of the semiconductor light emitting device 1 and a value of 1000 times the reciprocal of the device temperature.

FIG. 6 is an emission spectrum distribution chart of a semiconductor light emitting device.

FIG. 7 is a sectional view and an energy level diagram of a semiconductor light emitting device 40 according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between an injection current density and a light emission intensity of the semiconductor light emitting device 40.

FIG. 9 is a sectional view of a semiconductor light emitting device 14 according to a third embodiment of the present invention.

10 (1) is a sectional view of a semiconductor light emitting device 28 of a fourth embodiment, FIG. 10 (2) is an enlarged sectional view of a P layer 29 of the semiconductor light emitting device 28, and FIG. 10 (3) is a semiconductor. 3 is an energy level diagram of the light emitting element 28. FIG.

FIG. 11 is a diagram showing the relationship between the injection current density and the emission intensity of the semiconductor light emitting device 28.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor light emitting element 2 Back surface electrode 3 N layer 4 I layer 5 P layer 6 Transparent electrode 38 Barrier 39 Well layer

Claims (5)

[Claims] 1. A P type in which I-type amorphous SiC is used as a light emitting active layer and both ends thereof are sandwiched by P-type and N-type semiconductors.
It has an IN structure, is provided with an electrode for applying a positive voltage on the P side and a negative voltage on the N side, and the forbidden band width of the I-type amorphous SiC is determined corresponding to the visible light region. Semiconductor light emitting device. 2. A transparent conductive plate body is coated on a transparent substrate 7, and the transparent plate 6 is separated by using a laser.
In the electric field between a pair of electrodes connected to the high frequency power supply,
A gas containing C ₂ H ₂ gas and SiH ₄ gas is mixed gas ratio X Of 50 to 63% by plasma-enhanced chemical vapor deposition on the transparent electrode 6 to form P-type amorphous Si.
C, I-type amorphous SiC having a bandgap of 2.29 to 2.64 eV, and N-type amorphous SiC are formed in this order, and each element is separated by using a laser, and the metal electrode 2 is attached to each element. A semiconductor light emitting device characterized by vapor deposition. 3. The semiconductor light emitting device according to claim 1, wherein a plurality of PIN structures are stacked, and the band gap widths of the I-type amorphous SiC of each PIN structure are different from each other. 4. A PIN structure in which I-type amorphous SiC having a band gap of 2.29 to 2.64 eV is used as an active layer for light emission, and both ends thereof are sandwiched by P-type and N-type semiconductors,
Electrodes for applying a positive voltage to the P side and a negative voltage to the N side are provided, and at least the electrodes provided on the N-type semiconductor are transparent electrodes. The band gaps m1 and m3 of the P-type and N-type semiconductors are Is selected to be smaller than the band gap m2 of the I-type amorphous SiC, and the voltage is within the range of about 1 to 15V.
A semiconductor light emitting device characterized in that as the band width of iC is larger, a higher voltage is selected and a current density of 1 to 10 ² mA / cm ² is selected. 5. I-type amorphous SiC 42, 45, 48; 17, 21 having a band gap of 2.29 to 2.64 eV,
A light emitting active layer, both ends of which are P-type and N-type semiconductors 41, 44, 47, 16, 20; 43, 46, 49, 1
PIN structure 40a, 40b, 40 sandwiched between 8 and 22
c; 14a, 14b, and this PIN structure 40a, 40b, 40c; 14a, 14
a plurality of stacked b, and each stacked PIN structure 40a, 40b, 40c; 14
The forbidden band widths E ₀₁ , E ₀₂ , and E ₀₃ of the I-type amorphous SiCs a and 14b are changed so as to be sequentially increased toward the downstream in the light emission direction, and the PIN structures 40a, 40b, and 40c. 14a, 14b
Each electrode 1 for applying a positive voltage to the P side and a negative voltage to the N side of
5, 19 and 23 are provided, and the remaining electrodes 15 and 19 other than the electrodes 23 provided on the N-type semiconductors 49 and 22 of the PIN structures 40c and 14b having the minimum band gap of I-type amorphous SiC are made transparent. PIN structures 40a, 40b, 40c; 14a, 14b
P-type and N-type semiconductors 41, 44, 47 in
Forbidden band widths m1 and m3 of 16, 20; 43, 46, 49, 18 and 22 are PIN structures 40a, 40b and 40, respectively.
c; 14a, 14b I-type amorphous SiC 42, 4
5, 48; 17, 21 is selected to be smaller than the band gap m2 of I-type amorphous S in the range of about 1 to 15V.
A semiconductor light emitting device characterized in that as the band width of iC is larger, a higher voltage is selected and a current density of 10 to 10 ³ mA / cm ² is selected.