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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light emitting semiconductor device
which is constituted using semiconductor layers.
2. Description of the Prior Art
Heretofore there has been proposed a light emitting semiconductor device of
the type that p and n type single crystal semiconductor layers are formed
one on the other to define therebetween a pn junction. In this case, the
single crystal semiconductor layers are usually formed of direct gap
semiconductors of the III-V compounds, such as GaAs, GaAs.sub.1-x
P(0<x<1),Ga.sub.1-x Al.sub.x As(0<x<1) and so forth. The reason for using
such direct gap III-V compound semiconductors is that they provide for
enhanced light emission efficiency as compared with indirect gap III-V
compound semiconductors. However, the formation of such semiconductor
layers involves much difficulty as the semiconductor constituting the
layers must be provided in a single crystal form.
Accordingly, the conventional light emitting semiconductor device using
semiconductor layers of the direct gap III-V compound semiconductors are
difficult and expensive to manufacture.
Furthermore, in the prior art light emitting semiconductor device it is
customary that the two single-crystal semiconductor layers laminated to
define therebetween the pn junction are formed of direct gap
single-crystal III-V compound semiconductors of the same composition, i.e.
of the same energy gap, and hence the pn junction is a homojunction.
With such a light emitting semiconductor device, when applying a forward
bias voltage to the pn junction so as to emit light, the barrier height of
the pn junction is decreased, facilitating electrons from the n type
semiconductor layer to diffuse deeply into the p type semiconductor layer
across the pn junction and holes from the p type semiconductor layer to
diffuse deeply into the n type semiconductor layer across the pn junction.
This leads to the shortcoming of impaired light emission efficiency.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a novel light
emitting semiconductor device which is free from the abovesaid defects of
the prior art.
According to an aspect of the present invention, the light emitting
semiconductor device comprises using non-single-crystal semiconductor
layers. The non-single-crystal semiconductor layers can easily be obtained
because the semiconductor forming them is non-single-crystal, not single
crystal.
Therefore, the present invention permits easy fabrication of the light
emitting semiconductor device at low cost.
According to another aspect of the present invention, the light emitting
semiconductor device is provided with a first non-single-crystal
semiconductor layer, a second non-single-crystal semiconductor layer
formed thereon and a third non-single-crystal semiconductor layer formed
thereon, or a first non-single-crystal semiconductor layer, many second
non-single-crystal semiconductor layers formed thereon and a third
non-single-crystal semiconductor layer formed on the first semiconductor
layer in such a manner that the second semiconductor layers are buried in
the third layer. The first and third semiconductor layers respectively
have either one of p and n conductivity types and the other so as to form,
a pin or pn junction, including the second semiconductor layers.
In this case, non-single-crystal semiconductors forming the first, second
and third semiconductor layers are doped with a dangling bond and
recombination center neutralizer. Hence the non-single-crystal
semiconductors behave as direct gap semiconductors.
The non-single-crystal semiconductor forming the second semiconductor layer
is smaller in energy gap than the non-single-crystal semiconductors of the
first and third semiconductor layers. For this reason, when applying a
bias forward voltage relative to the pin or pn junction so as to effect
light emission, even if the barrier height of the pin or pn junction is
reduced, at least electrons from the third (or first) non-single-crystal
semiconductor layer do not easily diffuse into the first (or third) layer
across the junction, or holes from the first (or third) non-single-crystal
semiconductor layer do not easily diffuse into the third (or first) layer
across the junction. As a consequence, radiative recombination of the
electrons and holes is effectively developed in the second
non-single-crystal semiconductor layer.
Therefore, the present invention is able to offer a light emitting
semiconductor device of high light emission efficiency.
Other objects, features and advantages of the present invention will become
more fully apparent from the following detailed description taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged sectional view schematically illustrating a first
embodiment of the light emitting semiconductor device of the present
invention;
FIG. 2A to 20 schematically show energy band structures explanatory of the
first embodiment;
FIG. 3 is an enlarged sectional view schematically illustrating a second
embodiment of the present invention;
FIGS. 4A to 40 schematically show energy band structures explanatory of the
second embodiment;
FIG. 5 is an enlarged sectional view schematically illustrating a third
embodiment of the present invention;
FIGS. 6A to 60 schematically show energy band structures explanatory of the
third embodiment;
FIG. 7 is an enlarged sectional view schematically illustrating a fourth
embodiment of the present invention;
FIGS. 8A and 8B schematically show energy band structures explanatory of
the fourth embodiment;
FIGS. 9 and 11 are enlarged sectional views schematically illustrating
fifth and sixth embodiments of the present invention, respectively.
FIGS. 10A to 10C and 12A to 12C schematically show energy band structures
explanatory of the fifth and sixth embodiments, respectively.
FIGS. 13 and 15 are enlarged sectional view schematically illustrating
seventh and eighth embodiments of the present invention, respectively.
FIGS. 14A to 14C and 16A to 16C schematically show energy band structures
explanatory of the seventh and eighth embodiments, respectively.
FIGS. 17 and 19 are enlarged sectional views schematically illustrating
ninth and tenth embodiments of the present invention, respectively.
FIGS. 18A to 18C and 20A to 20C schematically show energy band structures
explanatory of the ninth and tenth embodiments, respectively.
FIG. 21 is an enlarged sectional view schematically illustrating an
eleventh embodiment of the present invention;
FIG. 22A to 22B schematically shows an energy band structure explanatory of
the eleventh embodiment;
FIG. 23 is an enlarged sectional view schematically illustrating a twelfth
embodiment of the present invention;
FIG. 24A to 24B schematically shows an energy band structure explanatory of
the twelfth embodiment;
FIGS. 25 and 26 are enlarged sectional views schematically illustrating
thirteenth and fourteenth embodiments of the present invention,
respectively.
FIGS. 27, 28, 29 and 30 are enlarged sectional views schematically
illustrating fifteenth, sixteenth, seventeenth and eighteenth embodiments
of the present invention, respectively.
FIGS. 31, 32, 33 and 34 are enlarged sectional views schematically
illustrating nineteenth, twentieth, twenty-first and twenty-second
embodiments of the present invention, respectively.
FIGS. 35, 36, 37 and 38 are enlarged sectional views schematically
illustrating twenty-third, twenty-fourth, twenty-fifth and twenty-sixth
embodiments of the present invention, respectively.
FIG. 39A is a plan view schematically illustrating a twenty-seventh
embodiment of the present invention;
FIGS. 39B and 39C are sectional views taken on the lines B--B and C--C in
FIG. 39A, respectively.
FIG. 40 is a circuit diagram of the device depicted in FIG. 39A;
FIG. 41A is a plan view schematically illustrating a twenty-eighth
embodiment of the present invention;
FIGS. 41B and 41C are sectional views taken on the lines B--B and C--C in
FIG. 41A, respectively;
FIG. 42A is a plan view schematically illustrating a twenty-ninth
embodiment of the present invention;
FIGS. 42B and 42C are sectional views taken on the lines B--B and C--C in
FIG. 42A, respectively.
FIG. 43A is a plan view schematically illustrating a thirtieth embodiment
of the present invention;
FIGS. 43B and 43C are sectional views taken on the lines B--B and C--C in
FIG. 43A, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 schematically illustrates a first embodiment of the light emitting
semiconductor device of the present invention, in which a
light-transparent electrode 2 is formed on a light-transparent insulated
substrate 1. The insulated substrate 1 may be formed as of glass, ceramic,
synthetic resin of the like material. The electrode 2 may be formed as tin
oxides, indium oxide, antimony oxide, indium-titanium oxide, a mixture of
antimony oxide and titanium oxide or the like.
On the light-transparent electrode 2, semiconductor layer 3, 4 and 5 are
formed one on another in this order:
The semiconductor layers 3, 4 and 5 are each formed of a non-single-crystal
semiconductor such as an amorphous, semi-amorphous or polycrystalline
semiconductor. The semi-amorphous semiconductor has such a structure that
its degree of crystallization varies spatially, and it is typically a
semiconductor which is composed of a mixture of a micro-crystalline
semiconductor having a lattice strain and a particle size of 5 to 200
.ANG. and a non-single-crystal semiconductor such as an amorphous
semiconductor. The non-single-crystal semiconductor, which forms each of
the semiconductor layers 3, 4 and 5, may be the Group IV element such as
silicon (Si) or germanium (Ge), a carbide of the Group IV element such as
silicon carbide (Si.sub.x C.sub.1-x).0.<x<x) or germanium carbide
(Ge.sub.x C.sub.1-x).0.<x<1), a nitride of the Group IV element such as
silicon nitride (Si.sub.3 N.sub.4-x).0.<x<4) or germanium nitride
(Ge.sub.3 N.sub.4-x (.0.<x<4), or an oxide of the Group IV element such as
silicon oxide (SiO.sub.2-).0.<x<2).
The non-single-crystal semiconductor forming the layer 3 is doped with the
Group III element which is a p type impurity, such as boron (B), aluminum
(Al), or indium (In), to make the layer 3 p-type. The non-single-crystal
semiconductor forming the layer 5 is doped with the Group V element which
is an n type impurity, such as phosphors (P), arsenic (As), or antimony
(Sb), rendering the layer 5 n-type.
The semiconductor layer 4 is composed of a non-single-crystal semiconductor
14. The non-single-crystal semiconductor forming the layer 14 is not doped
with any of the abovesaid Group III and IV elements or it is doped with
them so that the conductivity type of the layer 14 may be compensated for,
making the layer 14 exhibit the i conductivity type.
The non-single-crystal semiconductors constituting the layers 3, 4 and 5
are each doped with a dangling bond and recombination center neutralizer
such as hydrogen or a halogen such as fluorine. In consequence, the
non-single-crystal semiconductor behaves as a direct gap one to generate
radiative recombination of carriers.
The non-single-crystal semiconductors for the layers 3, 4 and 5 may be the
aforementioned Group IV element, its carbide, nitride or oxide or its
compound semiconductor but the non-single-crystal semiconductor of the
layer 4 and consequently the layer 14 has a smaller energy gap than does
the non-single-crystal semiconductors of the layers 3 and 5. That is to
say, letting the energy gaps of the non-single-crystal semiconductors of
the layers 3, 14 and 5 be represented by Eg.sub.3, Eg.sub.4 and Eg.sub.5,
respectively, they bear relationships Eg.sub.3 >Eg.sub.14, Eg.sub.5
>Eg.sub.14 as shown in FIGS. 2A to 2I, Eg.sub.3 .gtoreq.Eg.sub.14,
Eg.sub.5 >Eg.sub.14 as shown in FIGS. 2J to 2L, (which illustrate the case
of Eg.sub.3 .div.Eg.sub.14), Eg.sub.5 .gtoreq.Eg.sub.14, Eg.sub.5
>Eg.sub.14 as shown in FIGS. 2M to 2O (which illustrate the case of
Eg.sub.5 .div.Eg.sub.14). In the case where the energy gaps Eg.sub.3,
Eg.sub.14 and Eg.sub.5 bear relationships Eg.sub.3 >Eg.sub.14, Eg.sub.5
>Eg.sub.14, the energy gaps Eg.sub.3 and Eg.sub.5 may bear a relationship
Eg.sub.3 =Eg.sub.5 as shown in FIGS. 2A, 2F and 2I, Eg.sub.3 >Eg.sub.5 as
shown in FIGS. 2B, 2C and 2G, or Eg.sub.3 >Eg.sub.5 as shown in FIGS. 2D,
2E and 2H. In order that the energy gaps Eg.sub.3, Eg.sub.14 and Eg.sub.5
of the semiconductors of the layers 3, 14 and 5 may bear the abovesaid
relationships, these layers 3, 14 and 5 may preferably be formed of a
silicon carbide (Si.sub.x C.sub.1-x).0..ltoreq.x.ltoreq.1). In this case,
however, the value of x in the Si.sub.x C.sub.1-x used for the layer 14
is selected larger than the value of x in the Si.sub.x C.sub.1-x for the
layers 3 and 5. In such a case, the energy gap Eg.sub.14 of the
semiconductor of the layer 14 is obtained in the range of 1.5 to 1.7 eV
and the energy gaps Eg.sub.3 and Eg.sub.5 of the semiconductors of the
layers 3 and are obtained in the range of 2.0 to 4.0 eV.
It is preferred that the semiconductor of the layer 14 be Si.sub.x
Ge.sub.1-x (.0..ltoreq.x.ltoreq.1) and the semiconductors of the layers 3
and 5 Si.sub.x C.sub.1-x (.0..ltoreq.x.ltoreq.1). In this case, however,
the value of x in the Si.sub.x Ge.sub.1-x is selected larger than the
value of x in the Si.sub.x C.sub.1-x.
Further, it is preferable that the semiconductors of the layers 3, 14 and 5
be Si.sub.x Ge.sub.1-x (.0..ltoreq.x.ltoreq.1). In this case, however, the
value of x in the SixGe.sub.1-x for the layer 14 is selected larger than
the value of x in the Si.sub.x Ge.sub.1-x for the layers 3 and 5.
Still further, it is preferable that the semiconductor of the layer 14 be
Si.sub.x C.sub.1-x (.0..ltoreq.x.ltoreq.1) and the semiconductors of the
layers 3 and 5 Si.sub.3 N.sub.4-x (.0..ltoreq.x.ltoreq.4).
The non-single-crystal semiconductor layer 3 makes ohmic contact with the
light-transparent electrode 2. The non-single-crystal layer 14 defines a
pi junction 8 between it and the semiconductor layer 3. When the energy
gaps Eg.sub.3 and Eg.sub.14 of the non-single-crystal semiconductors
forming the layers 3 and 14 bear the abovesaid relation Eg.sub.3
>Eg.sub.14 or Eg.sub.3 <Eg.sub.14, the pi junction 8 is heterojunction
but, in the case of Eg.sub.3 =Eg.sub.14, it is a homojunction. The
non-single-crystal semiconductor layer 5 forms an ni junction 9 between it
and the semiconductor layer 14. When the energy gaps Eg.sub.14 and
Eg.sub.5 of the semiconductors forming the layers 14 and 5 have the
aforesaid relation Eg.sub.14 <Eg.sub.5 or Eg.sub.14 >Eg.sub.5, the ni
junction 9 is a heterojunction and, in the case of Eg.sub.14 =Eg.sub.5, it
is a homojunction.
The semiconductor layers 3, 4 and 5 can be obtained very easily by the
plasma CVD technique because the semiconductor forming them may be
non-single-crystal. The semiconductor layers 3 and 5 are usually formed to
a desired thickness exceeding 0.1 .mu.m. The semiconductor layer 14 is
usually thinner than the semiconductor layers 3 and 5; it is 100 .ANG. to
2 .mu.m thick, in particular, 0.1 to 0.4 .mu.m.
The semiconductor layers 3, 4 and 5 form the pi junction 8 between the
layers 3 and 14 and the ni junction 9 between the layers 14 and 5,
constituting a pin junction structure as a whole.
The semiconductor layers 3 and 5 have such impurity concentrations which
provide such energy band profiles as shown in FIGS. 2A to 20 when a
forward bias voltage is applied to the abovesaid pin junction structure in
the case where the energy gaps Eg.sub.3, Eg.sub.14 and Eg.sub.5 of the
semiconductors forming the semiconductor layers 3, 14 and 5 bear the
aforementioned relationships. That is to say, the semiconductor layers 3
and 5 have such impurity concentrations that at least an edge of the
conduction band C.B. of the semiconductor forming the layer 3 assumes a
higher energy potential position than does the edge of the conduction band
C.B. of the semiconductor forming the layer 14, or an edge of the valence
band V.B. of the semiconductor forming the layer 5 assumes a higher energy
potential position than does the edge of the valence band V.B. of the
semiconductor forming the layer 14. In the drawings, there is shown the
case where the edges of the conduction band C.B. of the semiconductor of
the layer 3 and the valence band V.B. of the semiconductor of the layer 5
are respectively higher than the edges of the conduction band C.B. and the
valence band V.B. of the semiconductor of the layer 14.
The non-single-crystal semiconductor layer 5 is covered with an opaque
electrode 6 to make ohmic contact therewith as indicated by 10. The opaque
electrode 6 may be formed of aluminum (Al), nickel (Ni), cobalt (Co),
molybdenum (Mo) or the like.
When connecting a bias power source 11 across the electrodes 2 and 6 making
the former positive relative to the latter, the pin junction constituted
by the semiconductor layers 3, 14 and 5 is biased in a forward direction.
As a result of this, holes 12 from the p type semiconductor layer tend to
flow out therefrom into the n type semiconductor layer 5 across the pi
junction 8, the i type semiconductor layer 14 and the ni junction 9 as
typically depicted in FIGS. 2A, 2D, 2G, 2I and 2M. Conversely, electrons
13 from the n type semiconductor layer 5 also tend to flow into the p type
semiconductor layer 3 across the ni junction 9, the i type semiconductor
layer 14 and the pi junction 8. However, in the case where the edge of the
valence band V.B. of the semiconductor of the layer 5 assumes a higher
potential position than does the edge of the valence band of the
semiconductor forming the layer 14, the ni junction 9 constitutes a high
barrier against the holes 12. This limits the flowing of the holes 12 into
the semiconductor layer 5 across the ni junction 9, resulting in increased
density of holes in the layer 14. Where the edge of the conduction band
C.B. of the semiconductor of the layer 3 assumes a higher position than
the conduction band C.B. of the semiconductor of the layer 14, the pi
junction makes up a high barrier against the electrons 13. This limits the
flowing of the electrons 13 into the semiconductor layer 3 across the pi
junction 8, increasing the density of the electrons 13 in the layer 14.
As a result of this, direct transition type radiative recombination of
carriers is effectively developed in the semiconductor layer 14,
generating light with high efficiency. The light generated in the
semiconductor layer 14 is emitted to the outside, passing through the
semiconductor layer 3, the transparent electrode 2 and the transparent
insulated substrate 1 as indicated by 15 in FIG. 1. In this case, a
portion of the light is directed towards the electrode 6 through the
semiconductor layer 5 but it is reflected by the electrode 6 to be emitted
to the outside through the semiconductor layers 5, 4 and 3, the
transparent electrode 2 and the transparent substrate 1 as similarly
indicated by 15. The light 15 thus emitted has a wavelength corresponding
to the energy gap Eg.sub.14 of the semiconductor of the layer 14.
FIG. 3 illustrates a second embodiment of the light emitting semiconductor
device of the present invention. The parts corresponding to those in FIG.
1 are identified by the same reference numerals.
The light emitting semiconductor device of this embodiment is identical in
construction with the embodiment of FIG. 1 except that the i type
semiconductor layer 14 forming the non-single crystal semiconductor layer
4 of the latter is replaced with an n type non-single-crystal
semiconductor layer 24 to form a pn junction between the semiconductor
layers 3 and 24 and an nn junction 29 between the semiconductor layers 24
and 5.
The semiconductor layer 24 is formed of the same non-single-crystal
semiconductor as is employed for the semiconductor layer 14 in the
embodiment of FIG. 1 and the non-single-crystal semiconductor is doped
with the dangling bond and recombination center neutralizer as in the case
of FIG. 1. Accordingly, this semiconductor behaves as one that develops
direct transition type radiative recombination of carriers.
The non-single-crystal semiconductor, which forms the semiconductor layer
24, is doped with the same n type impurity as that for the semiconductor
layer 5 of the light emitting semiconductor device shown in FIG. 1,
whereby the semiconductor layer 24 is made n-type.
The semiconductor of the semiconductor layer 24 has an energy gap Eg.sub.24
smaller than the energy gap Eg.sub.3 of the semiconductor layer 3 and/or
the energy gap Eg.sub.5 of the semiconductor of the layer 5 as is the case
with the energy gap Eg.sub.14 of the semiconductor of the layer 14 in the
embodiment of FIG. 1. Accordingly, when the energy gaps Eg.sub.3 and
Eg.sub.24 of the semiconductors of the layers 3 and 24 bear such a
relationship as Eg.sub.3 >Eg.sub.24 or Eg.sub.3 <Eg.sub.24, the pn
junction 28 is a heterojunction but, in the case of Eg.sub.3 =Eg.sub.24,
it is usually a homojunction. The nn junction 29 is a heterojunction when
the energy gaps Eg.sub.24 and Eg.sub.5 of the semiconductors of the layers
24 and 5 bear such a relationship as Eg.sub.24 <Eg.sub.5 or Eg.sub.24
>Eg.sub.5 and, in the case of Eg.sub.24 =Eg.sub.5, the nn junction 29 is
usually homojunction.
The semiconductor layers 3, 24 and 5 have such impurity concentrations that
when applying a forward bias voltage to the pn junction 28 in the case
where the energy gaps Eg.sub.3, Eg.sub.24 and Eg.sub.5 of the
semiconductors bear the abovesaid relationship, the edge of the conduction
band C.B. of the semiconductor of at least the layer 3 assumes a higher
position than the edge of the conduction band of the semiconductor of the
layer 24, or the edge of the valence band V.B. of the semiconductor of the
layer 5 assumes a higher position than the edge of the valence band of the
semiconductor of the layer 24. In practice, the semiconductor layer 24 has
a lower impurity concentration than the semiconductor layers 3 and 5.
Connecting across the electrodes 2 and 6 the bias power source 11 which is
forward with respect to the pn junction 28, the holes 12 in the p type
semiconductor layer 3 tend to flow out therefrom into the n type
semiconductor layer 5 across the pn junction 28 and the n type
semiconductor layer 29 as typically shown in FIGS. 4A, 4D, 4J and 4M.
Further, the electrons 13 in the semiconductor layer 5 also tend to flow
out therefrom into the semiconductor layer 3 across the n type
semiconductor layer 24. In this case, however, at least the pn junction 28
serves as a high barrier against the holes 12, or the nn junction 29
constitutes a high barrier against the electrons 13. Therefore, the
density of the holes 12 and/or electrons 13 increases in the semiconductor
layer 24. As a result of this, radiative recombination of carriers
effectively takes place in the semiconductor layer 24 to efficiently
generate light, which is delivered to the outside as indicated by 15. The
light thus emitted has a wavelength corresponding to the energy gap
Eg.sub.24 of the semiconductor of the layer 24.
FIG. 5 illustrates a third embodiment of the light emitting semiconductor
device of the present invention, in which the parts corresponding to those
in FIG. 1 are identified by the same reference numerals.
This embodiment is identical in construction with the embodiment of FIG. 1
except that the i type non-single-crystal semiconductor layer 14 of the
latter is replaced with a p type non-single-crystal semiconductor layer
34, and that a pp junction 38 and a pn junction 39 are formed between the
semiconductor layers 3 and 34 and between the semiconductor layers 34 and
5, respectively.
The semiconductor layer 34 has the same structure as the layer 14 in the
embodiment of FIG. 1 except that the former is doped with the same p type
impurity as that used for the semiconductor in the device of FIG. 1.
Accordingly, the semiconductor layers 3, 34 and 5 constitute a pn
juncstructure, though no further detailed description will be given of the
layer 34. The energy gaps EG.sub.3, Eg.sub.34 and Eg.sub.5 of the
semiconductors forming the semiconductor layers 3, 34 and 5 assume such
relative values and positions as shown in FIGS. 6A to 60.
Connecting across the electrodes 2 and 6 the bias power source 11 which is
formed with respect to the pn junction 39, light is efficiently emitted as
in the case of FIG. 1 as indicated by 15. The light thus emitted has a
wavelength corresponding to the energy gap Eg.sub.34 of the semiconductor
layer 34.
FIG. 7 illustrates a fourth embodiment of the present invention, in which
the parts corresponding to those in FIG. 1 are identified by the same
reference numerals and no detailed description will be repeated. This
embodiment is identical in construction with the embodiment of FIG. 1
except that the non-single-crystal semiconductor layer 4 is made up of two
i type non-single-crystal semiconductor layers 14A and 14B formed one on
the other. In this case, the semiconductors of the layers 14A and 14B are
the same as that of the layer 14 in FIG. 1 and have different energy gaps
Eg.sub.14A and Eg.sub.14B as shown in FIGS. 11A and 11B. As this
embodiment is identical in construction with the embodiment of FIG. 1
except the above, the radiative recombination of carriers occurs in the
semiconductor layer 4, i.e. the layers 14A and 14B, emitting light though
not described in detail. In this case however, the light thus produced is
a combination of lights of different wavelengths because the energy gaps
Eg.sub.14A and Eg.sub.14B of the semiconductors of the layers 14A and 14B
are different.
FIGS. 9 and 11 illustrate fifth and sixth embodiments of the present
invention, which are identical in construction with the embodiment of FIG.
1 except that the semiconductor layer 4 is formed by the lamination of the
i type semiconductor layer 14 described previously in respect of FIG. 1
and the n type semiconductor layer 24 described previously in respect of
FIG. 3. In this case, however, the energy gaps Eg.sub.14 and Eg.sub.24 of
the semiconductors of the layers 14 and 24 may be equal to or different
from each other as shown in FIGS. 10A, B and C and FIGS 12A, B and C. In
FIG. 9, the layer 14 is shown to be formed on the side of the layer 3 and,
in FIG. 11, it is shown to be formed on the side of the layer 5.
With the embodiments of FIGS. 9 and 11, the radiative recombination of
carriers occurs in the semiconductor layers 14 and 24 as is the case with
FIGS. 1 and 3, emitting light though not described in detail. In this
case, if the energy gaps Eg.sub.14 and Eg.sub.24 of the semiconductors of
the layers 14 and 24 are different from each other, lights of two
different wavelengths are combined into a composite light.
FIGS. 13 and 15 illustrate seventh and eighth embodiments of the present
invention, which are identical in construction with the embodiment of FIG.
1 except that the semiconductor layer 4 is formed by the lamination of the
i type semiconductor layer 14 described previously in respect of FIG. 1
and the p type semiconductor layer 34 described previously in respect of
FIG. 5. In this case, however, the energy gaps EG.sub.14 and Eg.sub.34 of
the semiconductors of the layers 14 and 34 may be equal to or different
from each other as shown in FIGS. 14A, B and C and FIGS. 16A, B and C. In
FIG. 13, the layer 14 is shown to be formed on the side of the layer 3
and, in FIG. 15, it is shown to be formed on the side of the layer 5.
With the embodiments of FIGS. 13 and 15, the radiative recombination of
carriers occurs in the semiconductor layers 14 and 34 as is the case with
FIGS. 1 and 5, emitting light, though not described in detail. In this
case, if the energy gaps Eg.sub.14 and Eg.sub.34 of the semiconductors of
the layers 14 and 34 are different from each other, lights of two
different wavelengths are combined into a composite light.
FIGS. 17 and 19 illustrate ninth and tenth embodiments of the present
invention, which are identical in construction with the embodiment of FIG.
1 except that the semiconductor layer 4 is formed by the lamination of the
n type semiconductor layer 24 described previously in respect of FIG. 3
and the p type semiconductor layer 34 described previously in respect of
FIG. 5. In this case, however, the energy gaps Eg.sub.24 and Eg.sub.34 of
the semiconductors of the layers 24 and 34 may be equal to or different
from each other as shown in FIGS. 18A, B and C and FIGS. 20A, B and C. In
FIG. 17, the layer 24 is shown to be formed on the side of the layer 3
and, in FIG. 19, it is shown to be formed on the side of the layer 5.
With the embodiments of FIGS. 17 and 19, the radiative recombination of
carriers occurs in the semiconductor layers 24 and 34 as is the case with
FIGS. 3 and 5, emitting light though not described in detail. In this
case, if the energy gaps Eg.sub.24 and Eg.sub.34 of the semiconductor of
the layers 24 and 34 are different from each other, lights of two
different wavelengths are combined into a composite light.
FIG. 21 illustrates an eleventh embodiment of the present invention in
which the parts corresponding to those in FIG. 1 are identified by the
same reference numerals and no detailed description will be repeated. This
embodiment is identical in construction with the embodiment of FIG. 1
except that the non-single-crystal semiconductor layer 4 is made up of two
n type non-single-crystal semiconductor layers 24A and 24B formed one on
the other. In this case, the semiconductors of the layers 24A and 24B are
the same as that of the layer 24 in FIG. 3 and have different energy gaps
Eg.sub.24A and Eg.sub.24B as shown in FIGS. 22A and 22B. As this
embodiment is identical in construction with the embodiment of FIG. 1
except the above, the radiative recombination of | | |
