JP3002466B1 - Thermoelectric converter - Google Patents

Abstract

A p-type thermoelectric conversion layer provided with a p-type semiconductor and an n-type thermoelectric conversion layer provided with an n-type semiconductor are electrically connected in series via a heat-absorbing conductor. Provided is a thermoelectric conversion device provided with electrodes 12 and 13 for extracting thermoelectromotive force at both ends and capable of achieving high sensitivity and high detection performance. SOLUTION: At least one of a p-type thermoelectric conversion layer 7 and an n-type thermoelectric conversion layer 4 has a carrier supply layer 4b, 7b to which an impurity is added, and a band gap having a carrier supply layer 4b.
high purity layers 4a, 7b smaller than the band gaps of b, 7b
a) having a heterostructure consisting of

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric conversion device comprising a thermoelectric conversion layer comprising a p-type or n-type semiconductor and electrodes provided at both ends for extracting thermoelectromotive force, or a p-type semiconductor. The present invention relates to a thermoelectric conversion device in which a p-type thermoelectric conversion layer and an n-type thermoelectric conversion layer including an n-type semiconductor are electrically connected in series via a heat-absorbing conductor, and electrodes for extracting thermoelectromotive force are provided at both ends thereof. More specifically, the present invention relates to a technique for increasing the sensitivity and detectability of such a thermoelectric converter.

[0002]

2. Description of the Related Art A thermoelectric converter of this type uses a thermoelectric effect of a semiconductor to generate a thermoelectromotive force generated in each of a p-type and an n-type semiconductor due to a temperature difference between a heat absorbing conductor and an electrode by a Seebeck effect. It is configured to take out from

In the case where the above-described thermoelectric conversion device is used as an infrared sensor or the like, in order to achieve high sensitivity and high detection performance, as described below,
It is necessary to increase the conductivity of the thermoelectric conversion layer. Sensitivity R (unit: V / W) is Equation 1, Detectability D (unit: cm (Hz))
^1/2 / W) is expressed by Equation 2.

[0003]

## EQU1 ## R = αSR _th

D = R (AΔf / (4k _B TR _el )) ^1/2

Where α is the heat absorption coefficient, S is the Seebeck coefficient, R _th is the thermal resistance, A is the area of the heat absorber, Δf is the bandwidth, k _B is the Boltzmann constant, T is the absolute temperature, and R _el is the absolute temperature. Indicates electric resistance. From Equation 2, when the conductivity is increased, that is, R _el
Achieve a lower resistance when the thermal noise (4k _B TR _el) is can be improved detectability D decreases.

However, as shown in FIG. 5, since the Seebeck coefficient and the impurity concentration are in a relationship where the Seebeck coefficient value decreases as the impurity concentration increases, the impurity in the thermoelectric conversion layer is increased in order to increase the conductivity of the thermoelectric conversion layer. Conversely, when the concentration is increased, the Seebeck coefficient value decreases, and the sensitivity decreases. As a result, it can be seen that it is extremely difficult to improve the sensitivity characteristics even if the conductivity of the thermoelectric conversion layer is increased by increasing the impurity concentration.

The present invention has been made in view of the above problems, and has as its object to provide a p-type thermoelectric conversion layer having a p-type semiconductor and an n-type thermoelectric conversion layer having an n-type semiconductor. A thermoelectric conversion device that is electrically connected in series via a heat-absorbing conductor and provided with electrodes for extracting thermoelectromotive force at both ends of the thermoelectric conversion device, which can provide high sensitivity and high detectability. is there.

[0007]

A first characteristic configuration of a thermoelectric conversion device according to the present invention for achieving this object is to use a p-type semiconductor as described in claim 1 of the claims. An electrode having at least one of a p-type thermoelectric conversion layer provided and an n-type thermoelectric conversion layer provided with an n-type semiconductor, and electrodes for extracting thermoelectromotive force at both ends of the thermoelectric conversion layer. The thermoelectric conversion device provided, wherein the thermoelectric conversion layer has a heterostructure including a carrier supply layer to which impurities are added and a high-purity layer having a band gap smaller than the band gap of the carrier supply layer. .

[0008] The second characteristic structure is a p-type semiconductor device having a p-type semiconductor as described in claim 2 of the claims.
A thermoelectric conversion device comprising: an n-type thermoelectric conversion layer comprising an n-type semiconductor; and an n-type thermoelectric conversion layer comprising an n-type semiconductor, electrically connected in series via a heat-absorbing conductor, and electrodes provided at both ends thereof for extracting thermoelectromotive force. In this case, at least one of the p-type thermoelectric conversion layer and the n-type thermoelectric conversion layer is a hetero-layer comprising a carrier supply layer to which an impurity is added and a high-purity layer having a band gap smaller than that of the carrier supply layer. It has a structure.

The heat-absorbing conductor is an electric conductor for electrically connecting the p-type and n-type semiconductors so that the thermoelectromotive force generated in both thermoelectric conversion layers can be taken out in series between the two electrodes. While functioning as a connection medium, it absorbs thermal energy in the atmosphere and conducts heat to the portion of each thermoelectric conversion layer that contacts the heat absorbing conductor, between the portion that contacts the electrode and the portion that contacts the heat absorbing conductor. It functions as a heat absorber for forming a temperature difference. In addition, as long as the heat-absorbing conductor has both functions as an electric connection medium and a heat absorber,
Even if the composite has both functions formed of individual materials,
It may be a single body formed of a single material.

[0010] The third characteristic configuration is, in addition to the second characteristic configuration, as described in claim 3 of the claims section, in addition to the p-type thermoelectric conversion layer and the n-type thermoelectric conversion layer. Both have the above-mentioned hetero structure.

According to a fourth aspect of the present invention, in addition to the second or the third aspect, the high purity layer and the carrier supply layer are combined with each other. In the vicinity of the interface, a two-dimensional electron gas or a two-dimensional hole gas is formed at least in a portion overlapping the thickness direction of the heat absorbing conductor, the electrode, and the thermoelectric conversion layer.

[0012] The fifth feature configuration is, in addition to the second, third or fourth feature configuration, as described in claim 5 in the claims section, in addition to the n-type on a predetermined substrate. The point is that the thermoelectric conversion layer and the p-type thermoelectric conversion layer are laminated.

According to a sixth aspect of the present invention, in addition to the fifth aspect, the n-type thermoelectric conversion layer and the p-type thermoelectric conversion layer are in addition to the fifth characteristic configuration. The present invention is characterized in that a plurality of the thermoelectric conversion devices each including the heat absorbing conductor and the electrode are formed on the substrate.

According to a seventh aspect of the present invention, in addition to the first, second, third, fourth, fifth or sixth aspect of the present invention, as described in claim 7 of the claims section. The material composition of the carrier supply layer and the high-purity layer (carrier supply layer / high-purity layer) is InP / InGaAs, InAlAs / I
nP, InAlAs / InGaAs, AlGaAs / A
lGaAs, AlGaAs / InGaAs, AlGaAs
s / GaAs, AlGaAs / InAs, InGaP /
InGaAs, InGaP / AlGaAs, InGaP
/ GaAs, InGaP / InAs, AlGaN / Ga
N, AlGaN / AlGaN, AlGaN / InGa
N, AlGaN / SiC, GaN / SiC, GaN / I
That is, it is any one of nGaN and Si / SiGe.

The operation and effect will be described below. According to the first or second characteristic configuration of the thermoelectric conversion device according to the present invention, for example, when the hetero structure is employed in the n-type thermoelectric conversion layer, a portion of the n-type carrier supply layer which is in contact with an electrode and has a heat absorption property. The concentration difference of the electrons generated from the donor impurity occurs from the high temperature side to the low temperature side due to the temperature difference of the portion in contact with the conductor, and an electric field is formed in a direction to suppress the diffusion of the electrons accompanying the concentration gradient. Also, the high concentration of electrons on the high temperature side
The band gap moves to the high-purity layer side smaller than the band gap of the carrier supply layer without diffusing the high-resistance carrier supply layer. Further, since the band gap of the carrier supply layer is larger than the high-purity layer, a region having a low potential is formed near the interface on the high-purity layer side, so that the electrons supplied from the carrier supply layer side are Since it is concentrated near this interface, and the interface becomes an energy barrier for electrons when viewed from the high-purity layer side, a so-called two-dimensional electron gas is formed, and extremely high mobility along the interface, that is, high It shows conductivity. As a result, since the thermoelectric conversion function and the conductive function can be separated and controlled independently with the heterojunction interface interposed therebetween, high conductivity can be ensured without lowering the Seebeck coefficient value, and the thermoelectric conversion which has been considered difficult in the past is achieved. The conversion layer can have high sensitivity and high detection ability. Further, in the above description of the n-type thermoelectric conversion layer, if the electron is read as a hole and the donor is read as an acceptor, and the polarity is reversed, the same applies to the case where the heterostructure is adopted as a p-type thermoelectric conversion layer. It will be explained that the above-mentioned effects are obtained.

According to the third characteristic configuration, both the p-type and n-type thermoelectric conversion layers can achieve high sensitivity and high detection performance.
Higher sensitivity and higher detectability can be achieved as compared with the case where only one of the thermoelectric conversion layers has the heterostructure.

The above two-dimensional electron gas or two-dimensional hole gas is not formed depending on conditions such as the thickness of the carrier supply layer and the electric field strength in the thickness direction between the heat absorbing conductor and the electrode. It is possible. In other words, if the thickness of the carrier supply layer is small, in the case of an n-type thermoelectric conversion layer, the number of free electrons generated from donor impurities that migrate to the high-purity layer cannot be obtained sufficiently, and the two-dimensional Electron gas is not formed. As described above, the two-dimensional electron gas is formed on the n-type thermoelectric conversion layer and the two-dimensional hole gas is formed on the p-type thermoelectric conversion layer.

According to the fourth characteristic structure, the portion of the high-purity layer near the interface with the carrier supply layer, which overlaps the heat absorbing conductor, the electrode, and the thermoelectric conversion layer in the thickness direction. During this time, a two-dimensional electron gas or a two-dimensional hole gas may not be formed, but even in such a case, a high concentration of electrons or holes on the high temperature side moves to the high-purity layer. Since such electrons or holes are conducted to the low-temperature side through the high-purity layer, high conductivity is secured as compared with the case where the heterostructure is not employed.

Further, it is necessary to suppress the series resistance component between the heat absorbing conductor or the electrode and a portion near the interface overlapping with the heat absorbing conductor or the electrode sufficiently low. Alternatively, by forming a two-dimensional hole gas, the series resistance component can be sufficiently reduced.

According to the fifth characteristic configuration, the n-type is formed on the predetermined substrate by utilizing a thin film lamination technique such as MBE (Molecular Beam Epitaxy) or MOCVD (Metal Organic Chemical Vapor Deposition). Alternatively, a p-type thermoelectric conversion layer is formed, the other thermoelectric conversion layer is formed thereon, and a part of the lower thermoelectric conversion layer is exposed to form the n-type or p-type thermoelectric conversion layer. By forming the heat absorbing conductor and the electrode respectively,
The thermoelectric conversion device according to the present invention can be manufactured by a series of steps. Further, by forming a peripheral circuit for signal processing for amplifying the output power of the thermoelectric conversion device on the same substrate, the functionality of the thermoelectric conversion device can be enhanced.

The predetermined substrate is made of Si, Ga
Various materials such as As, sapphire, and glass can be appropriately selected and used in combination with the material of the thermoelectric conversion layer.

According to the sixth characteristic configuration, for example, a high voltage can be taken out by connecting a plurality of the thermoelectric converters in series, and a large current can be taken out by connecting them in parallel, thereby improving the performance. You can do it. Also, by dicing the substrate into a plurality of chips, a plurality of thermoelectric converters having the same characteristics or a plurality of thermoelectric converters having different specification values of output voltage and output current can be manufactured from the same substrate. is there.

According to the seventh characteristic configuration, a combination of the carrier supply layer and the high-purity layer in which the band gap of the high-purity layer is smaller than the band gap of the carrier supply layer is obtained. A two-dimensional electron gas or a two-dimensional hole gas is formed in the vicinity of the interface of the purity layer, and the functions and effects of the first to sixth features can be specifically realized.

Further, in the material configuration of this characteristic configuration, a material having a lattice constant that is substantially close between the carrier supply layer and the high-purity layer is selected to avoid lattice mismatch at the heterojunction interface. , Si / SiGe, a two-dimensional electron gas or a two-dimensional hole gas is formed by a strained superlattice that actively utilizes lattice mismatch.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a thermoelectric converter according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the basic structure of the thermoelectric conversion device according to the present invention is such that a lateral etching stopper layer 2, a first separation layer 3,
An n-type thermoelectric conversion layer 4 including an n-type semiconductor, a first ohmic contact layer 5, a second separation layer 6, a p-type thermoelectric conversion layer 7 including a p-type semiconductor, and a second ohmic contact layer 8 are sequentially arranged. The n-type thermoelectric conversion layer 4 and the first ohmic contact layer 5, and the second separation layer 6 to the second ohmic contact layer 8 are selectively photo-etched separately to form the n-type thermoelectric layer. The conversion layer 4 and the p-type thermoelectric conversion layer 7 are patterned in a step-like manner, an insulating protective film 9 is formed thereon, and a window 10 for ohmic contact is opened at a predetermined portion of the insulating protective film 9 by photoetching. The n-type thermoelectric conversion layer 4
And the first ohmic contact layer 5 and the second ohmic contact layer 8 at the boundary between the p-type thermoelectric conversion layer 7 and the second ohmic contact layer 8 are exposed and connected by a heat absorbing conductor 11. The first ohmic contact layer 5 and the p-type thermoelectric conversion layer 7
Similarly, the second ohmic contact layer at the end is exposed by photoetching, and electrodes 12 and 13 are formed on the respective layers. The basic structure is substantially the same as a conventional thermopile.

Here, the heat-absorbing conductor 11 is
A temperature difference is formed between each of the electrodes 12 and 13 for each of the p-type thermoelectric conversion layer 4 and the p-type thermoelectric conversion layer 7, and the thermoelectromotive force generated by the temperature difference is connected in series as a high voltage. It is provided so that it can be taken out from the electrodes 12 and 13.

Further, in the present embodiment, in order to improve the sensitivity by increasing the thermal resistance of the lower n-type thermoelectric conversion layer 4 in particular, and to shorten the response time of the thermoelectric conversion device, In order to reduce the heat capacity of the thermoelectric conversion layers 4 and 7, a bridge structure for hollowly supporting the thermoelectric conversion layers 4 and 7 is adopted. The lateral etching stopper layer 2 is an etching stopper for etching a portion of the substrate 1 below the thermoelectric conversion layers 4 and 7 to form a bridge structure. The n-type thermoelectric conversion layer 4 is electrically insulated and separated from the substrate 1 by the first separation layer 3, and the n-type thermoelectric conversion layer 4 and the p-type thermoelectric conversion layer 7 are
The insulating layer 6 is electrically insulated from each other.

In the thermoelectric conversion device according to the present invention, at least one of the n-type thermoelectric conversion layer 4 and the p-type thermoelectric conversion layer 7 has a carrier supply layer to which an impurity is added and a band gap of the carrier supply layer. And a high-purity layer smaller than the band gap. In the embodiment described below, as shown in FIG. 1, both the thermoelectric conversion layers 4 and 7 have the hetero structure, and the n-type thermoelectric conversion layer 4 is formed of the high-purity layer 4a and the n-type carrier supply layer 4b. And the p-type thermoelectric conversion layer 7 has the hetero structure including a high-purity layer 7a and a p-type carrier supply layer 7b.

Next, the material of each component in the present embodiment
The charge composition will be described. The substrate 1 has a semi-insulating In
Using the P substrate 1a, the lateral etching stopper
100 nm-thick i-In layer 2_xGa_1-xAs
Is used as the high-purity layers 4a and 7a.
-In_xGa_1-xAs, the n-type carrier supply layer 4b
100 nm-thick n-InP as the p-type carrier
P-InP having a thickness of 100 nm as the supply layer 7b
The first and second separation layers 3 and 6 each have a thickness of 200 nm.
-InP is applied as the first ohmic contact layer 5 to a thickness of 1
00nm n⁺-In_xGa_1-xAs for the second oh
A 100 nm-thick p ⁺-In_xG
a_1-xAs, respectively, semiconductors such as MBE method and MOCVD method
It is formed using body thin film lamination technology.

In each of the thermoelectric conversion layers 4 and 7, In_x
Ga_1-xAs and InP are the various semiconductor vans shown in FIG.
Dogap E_gAnd the lattice constant, the InP band
Gap E_g2Is In_xGa_1-xAs band gap E
_g1For E_g2> E_g1That the relationship is satisfied
I understand. The n-type carrier supply layer 4b, ie, n-
InP is made by doping impurities such as Si, Se, and S by modulation doping.
P-type carrier supply layer 7b
-InP is doped with impurities such as Mg by modulation doping.
To form the n-type and p-type carrier supply layers 4b and 7b.
The impurity concentration is 10¹⁷~ 1 × 10¹⁸cm^-3About
The carrier concentration of the high-purity layers 4a and 7a is 10¹⁴c
m^-3It is about. Also, In_xGa_1-xComposition ratio x of As
Is x = 0.53 when lattice matching with InP is obtained,
The composition ratio x is preferably around 0.53. Follow
Thus, the heterostructure having the material configuration as described above and the modulation
The n-type thermoelectric conversion layer 4
2D electrons near the heterojunction interface of the high-purity layer 4a.
The gas 14 and the high-purity layer 7a of the p-type thermoelectric conversion layer 7
A two-dimensional hole gas 15 is formed near the heterojunction interface.
You. Also, In_xGa_1-xAs is higher than GaAs
Is known as a material having an electron mobility.
Coupled with the formation of the secondary gas 14 and the two-dimensional hole gas 15
The thermoelectric conversion layers 4 and 7 contribute to high conductivity.

The thickness of the n-type and p-type carrier supply layers 4b and 7b is set to 100 nm so that the two-dimensional electron gas 14 and the two-dimensional hole gas 15 can be surely formed. Can be reduced to a critical value within a range of about 50 nm to 80 nm, at which the two-dimensional electron gas 14 and the two-dimensional hole gas 15 are not formed.

The first ohmic contact layer 5 of n ⁺ −
In _x Ga _{1 -x} As is also formed by adding impurities such as Si, Se, and S, and the impurity concentration is higher than that of the n-type carrier supply layer 4b and is about 5 × 10 ¹⁸ cm ⁻³ . Also, the second ohmic contact layer 8 of p ⁺ -In _x G
a _1-x As is also formed by adding an impurity such as Mg, and its impurity concentration is higher than that of the p-type carrier supply layer 7b and is about 5 × 10 ¹⁸ cm ⁻³ . By setting the impurity concentration of the first ohmic contact layer 5 higher than that of the n-type carrier supply layer 4b, free electrons due to the band gap of the first ohmic contact layer 5 being smaller than the n-type carrier supply layer 4b are obtained. Can be prevented, and the electrons in the first ohmic contact layer 5 also move to the high-purity layer 4a to be used for forming the two-dimensional electron gas 14. As a result, the inside of the first ohmic contact layer 5 is depleted, the electric resistance in the lateral direction becomes high, and the film thickness is thin, so that the electric conduction in the lateral direction via the first ohmic contact layer 5 is suppressed. You. In the case of the present embodiment, when an Au alloy is used as the electrode metal, it is considered that ohmic contact is possible without providing the second ohmic contact layer 8, but by providing the second ohmic contact layer 8, A metal other than the Au alloy such as Al can be used as the electrode metal. As a result, material cost can be reduced and mass production adaptability can be increased.

Further, the first and second separation layers 3 and 6 are used.
The use of high-purity i-InP enables high-resistance insulation
Functions as a layer, and the band gap of InP is
In _xGa_1-xClose the carrier because it is larger than As
It can also be expected to have a confined effect. The first separation layer 3
When the substrate 1 is a high-resistance material having a high insulating property.
It is not necessarily required.

The insulating protective film 9 is formed on the respective ohmic contact layers 5 and 8 of the n-type and p-type thermoelectric conversion layers 4 and 7 formed in a step-like manner.
It is formed by forming a SiO ₂ film or the like by a CVD method, a sputtering method, or the like. The window for ohmic contact 10 is
And p at the boundary and end of the p-type and p-type thermoelectric conversion layers 4 and 7
Photo-etching is provided at each of two locations in the region. First, the p-type ohmic contact metal 1 is formed in the window 10 in the p region.
6, TiPtAu is deposited, and then a window 10 in the n region is formed.
Then, AuGeNi, which is an n-type ohmic contact metal 17, is deposited, and both ohmic contact metals 16, 17 are annealed to form n-type and p-type ohmic contacts. Subsequently, Cr / Au is used to electrically connect to both ohmic contact metals 16 and 17 at both ends of the n-type and p-type thermoelectric conversion layers 4 and 7.
Metal wiring 18 is connected to both ohmic contact metals 1 at both ends.
6, 17 and the insulating protective film 9 are formed by vapor deposition. Therefore, the electrodes 12 and 13 are constituted by the ohmic contact metals 16 and 17 at both ends and the Cr / Au metal wiring 18. The Cr / Au metal wiring 18 is patterned as a wiring for connecting a plurality of thermoelectric converters described later in series or as a bonding pad for packaging.

Both ohmic contact metals 16, 1 formed in the window 10 at the boundary between the n-type and p-type thermoelectric conversion layers 4, 7
7 has one part overlapped with the other part or all, and the n-type and p-type thermoelectric conversion layers 4 and 7 are electrically connected in series. Next, a heat absorber 19 such as an Au cluster is deposited on the ohmic contact metals 16 and 17 at the boundary, and is patterned into a predetermined planar shape by a lift-off method or the like. The heat absorbing conductor 11 is constituted by the ohmic contact metals 16 and 17 at the boundary between the n-type and p-type thermoelectric conversion layers 4 and 7 and the heat absorbing body 19.

Finally, the InP substrate 1a is laterally anisotropically etched by a micromachining technique using a single thermoelectric conversion device composed of a pair of the n-type and p-type thermoelectric conversion layers 4 and 7. Bridge structure. First, an opening for anisotropic etching is formed in the lateral etching stopper layer 2, the first separation layer 3, and the insulating protective film 9, and the substrate 1 is etched from this opening with a predetermined etchant.
Is etched to form a gap portion 20 having a depth of about 200 to 300 μm below the thermoelectric conversion device. At this time, the In _x Ga which is the lateral etching stopper layer 2 is used.
_Since the etching rate of _1-x As is lower than that of the InP substrate 1a, it functions as an etching stopper. The I
The nP substrate 1a has a (100) crystal plane in order to anisotropically etch the void 20 into an inverted pyramid shape. Note that the above-described anisotropic etching is an example of a micromachining technique for forming the bridge structure, and the gap 20 may be formed using an etching technique other than the anisotropic etching. . Furthermore, in the present embodiment, the thermoelectric conversion device has a form having a bridge structure that is hollowly supported, but the thermoelectric conversion device does not necessarily have to have a bridge structure that is hollowly supported. For example, a structure may be employed in which a column having a width smaller than that of the n-type thermoelectric conversion layer 4 is formed on the substrate 1 to support the n-type thermoelectric conversion layer 4 from below. Even with such a structure, the thermal resistance of the n-type thermoelectric conversion layer 4 can be increased, and the heat capacity can be reduced.

As shown in FIG. 3, the planar shape of the single thermoelectric conversion device manufactured in the above-described manufacturing process is such that the area of the heat absorbing conductor 11 is increased in order to increase the heat absorbing area in order to increase the detectability. Patterning in the step of forming the n-type and p-type thermoelectric conversion layers 4 and 7 in a stepwise manner so that the n-type and p-type thermoelectric conversion layers 4 and 7 are elongated to increase the thermal resistance of the n-type and p-type thermoelectric conversion layers 4 and 7, respectively. Is done. The reference dimensions of the n-type and p-type thermoelectric conversion layers 4 and 7 are about 1 m in length in a state where both are combined.
m and a width of about 20 μm.

Further, as shown in FIG. 4, when a plurality of the single thermoelectric converters are simultaneously formed on the substrate 1 in the above-described manufacturing process, one of the single thermoelectric converters may be adjacent to the other. The electrode 1 of the n-type thermoelectric conversion layer 4
2 and the electrode 13 of the other p-type thermoelectric conversion layer are connected, and a plurality of thermoelectric conversion devices are connected in series while meandering. According to such a configuration, the voltage value of the thermoelectromotive force that can be taken out increases, and the sensitivity is improved by the number of series. When the plurality of thermoelectric converters meander, the heat absorbing conductor 11 is arranged so as to be adjacent to the elongated portion of the n-type or p-type thermoelectric conversion layers 4 and 7 of the adjacent thermoelectric converter. Thus, a plurality of thermoelectric conversion devices can be integrated at a high density.

Next, another embodiment of the thermoelectric converter according to the present invention will be described. <1> In the above embodiment, the high-purity layers 4a, 7
a is a 900 nm-thick i-In _x Ga _1-x As,
The n-type and p-type carrier supply layers 4b and 7b are made of n-InP and p-InP with a thickness of 100 nm, but the high-purity layers 4a and 7a and the n-type and p-type carrier supply layers 4b and 7b are not used. The material configuration may be other than the above. Other material configurations are shown in Table 1,
The two-dimensional electron gas 1 is provided in the high-purity layers 4a and 7a, respectively.
4 and a heterostructure forming the two-dimensional hole gas 15. Further, the film thicknesses of the layers including the high-purity layers 4a and 7a and the n-type and p-type carrier supply layers 4b and 7b are not necessarily limited to the values in the above embodiment.
It can be changed as appropriate.

[0040]

[Table 1]

<2> In the above-described embodiment, the p-type thermoelectric conversion layer 7 is laminated on the n-type thermoelectric conversion layer 4, but the order of lamination may be reversed. . In addition, the hetero structure includes the n-type and p-type thermoelectric conversion layers 4,
7, but may be applied to only one of them.

<3> In the above embodiment, each semiconductor layer is assumed to be a single crystal epitaxially grown. However, the semiconductor layer may not necessarily be a single crystal.

<4> The n-type and p-type thermoelectric conversion layers 4 and 7
Depending on the choice of material, the ohmic contact metal 1
When direct ohmic contact with the first and second ohmic contacts 6 and 17 is possible, the first and second ohmic contact layers 5 and 8 need not always be provided.

<5> In the above embodiment, n
And the p-type thermoelectric conversion layers 4 and 7 have a complementary configuration using both thermoelectric conversion layers.
May be used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of a thermoelectric conversion device according to the present invention.

FIG. 2 is a relationship diagram showing a relationship between a band gap E _g and a lattice constant of various semiconductors.

FIG. 3 is a plan view showing a single thermoelectric converter according to the present invention.

FIG. 4 is a plan view showing a plurality of thermoelectric converters connected in series according to the present invention.

FIG. 5 is a relationship diagram showing a relationship between a Seebeck coefficient and an impurity concentration.

[Explanation of symbols]

 Reference Signs List 1 substrate 1a InP substrate 2 lateral etching stopper layer 3 first separation layer 4 n-type thermoelectric conversion layer 4a, 7a high-purity layer 4b n-type carrier supply layer 5 first ohmic contact layer 6 second separation layer 7 p-type thermoelectric conversion layer 7b p-type carrier supply layer 8 second ohmic contact layer 9 insulating protective film 10 window for ohmic contact 11 heat-absorbing conductor 12, 13 electrode 14 two-dimensional electron gas 15 two-dimensional hole gas 16 p-type ohmic contact metal 17 n Type ohmic contact metal 18 Cr / Au metal wiring 19 heat absorber 20 void

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-32354 (JP, A) JP-A-10-32353 (JP, A) JP-A-10-32355 (JP, A) JP-A-1- 208876 (JP, A) JP-A-63-102382 (JP, A) US Pat. No. 5,436,467 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) 35/26

Claims (7)

(57) [Claims] 1. A thermoelectric conversion layer having at least one of a p-type thermoelectric conversion layer having a p-type semiconductor and an n-type thermoelectric conversion layer having an n-type semiconductor. A thermoelectric conversion device provided with electrodes for extracting thermoelectromotive force at both ends, wherein the thermoelectric conversion layer has a carrier supply layer to which impurities are added, and a high-purity layer whose band gap is smaller than the band gap of the carrier supply layer. A thermoelectric conversion device having a heterostructure comprising: 2. A p-type thermoelectric conversion layer comprising a p-type semiconductor and an n-type thermoelectric conversion layer comprising an n-type semiconductor are electrically connected in series via a heat-absorbing conductor. A thermoelectric conversion device provided with an electrode for extracting electric power, wherein at least one of the p-type thermoelectric conversion layer and the n-type thermoelectric conversion layer has a carrier supply layer to which an impurity is added, and a band gap is the carrier supply layer. A thermoelectric conversion device having a heterostructure including a high-purity layer smaller than a band gap of the layer. 3. The thermoelectric conversion device according to claim 2, wherein both the p-type thermoelectric conversion layer and the n-type thermoelectric conversion layer have the hetero structure. 4. A two-dimensional electron gas or two-dimensional positive electrode at least in a portion of the high-purity layer near an interface with the carrier supply layer, the portion overlapping in the thickness direction of the heat absorbing conductor, the electrode, and the thermoelectric conversion layer. 4. The thermoelectric conversion device according to claim 2, wherein a pore gas is formed. 5. The thermoelectric conversion device according to claim 2, wherein the n-type thermoelectric conversion layer and the p-type thermoelectric conversion layer are laminated on a predetermined substrate. 6. The thermoelectric conversion device comprising the n-type thermoelectric conversion layer, the p-type thermoelectric conversion layer, the heat-absorbing conductor, and the electrode, wherein a plurality of the thermoelectric devices are formed on the substrate. Thermoelectric converter. 7. The material configuration of the carrier supply layer and the high purity layer (carrier supply layer / high purity layer) is InP / In.
GaAs, InAlAs / InP, InAlAs / In
GaAs, AlGaAs / AlGaAs, AlGaAs
/ InGaAs, AlGaAs / GaAs, AlGaAs
s / InAs, InGaP / InGaAs, InGaP
/ AlGaAs, InGaP / GaAs, InGaP /
InAs, AlGaN / GaN, AlGaN / AlGa
N, AlGaN / InGaN, AlGaN / SiC, G
aN / SiC, GaN / InGaN, and Si / Si
The thermoelectric conversion device according to claim 1, 2, 3, 4, 5, or 6, which is any one of Ge.