JP7291942B2 - Quantum infrared sensor - Google Patents

Description

The present invention relates to a quantum infrared sensor.

There are pyroelectric infrared sensors and quantum infrared sensors. Pyroelectric infrared sensors detect infrared rays by heat and can operate at room temperature, but have the problem of low sensitivity. On the other hand, quantum-type infrared sensors can detect incident photons with high sensitivity in proportion to the number of incident photons, but have the problem that they are difficult to operate at room temperature.
The main reasons why it is difficult for the quantum infrared sensor to operate at room temperature are that the quantum infrared sensor uses a compound semiconductor crystal, so it must be cooled until the n-type or p-type characteristics appear. Among the various noise components is the need to reduce thermally excited noise. Thermally excited noise is the fluctuation of the number of carriers thermally excited from the valence band to the conduction band by thermal energy corresponding to temperature. Thermally induced noise varies with temperature and can be reduced by cooling.

In a quantum infrared sensor, when irradiated with infrared rays having an energy (hc/λ) higher than the bandgap (Eg) of a compound semiconductor crystal, electrons or holes are excited in the quantum dot region (electrons are excited in the conduction band). Infrared rays are detected by applying a bias voltage to the photocarriers of these electrons and holes and detecting them as photocurrent. When the infrared wavelength range of the target to be detected is 3 to 5 μm, a compound semiconductor crystal having a bandgap (Eg) of about 250 to 400 meV is used. The influence of noise due to carriers thermally excited from the electronic band to the conduction band cannot be ignored, and it is necessary to reduce the thermal energy by cooling.

In recent years, quantum structure fabrication technology has improved, and quantum infrared sensors that can operate at room temperature using quantum nanostructures have been actively developed. It is expected to be widely applied to sensing and other applications.

For example, a quantum infrared sensor with improved infrared detection sensitivity is known (see Patent Document 1, for example). In the quantum infrared sensor disclosed in Patent Document 1, an intermediate layer such as GaAs, AlGaAs, or InGaAlAs and In _x Ga _1-x As (0<x≦ 1) has a structure formed by a quantum dot layer containing quantum dots, and an AlAs layer is provided on one side of the interface between the intermediate layer and the quantum dot layer containing quantum dots and to cover at least the quantum dots. It prevents mutual diffusion of the elements forming the quantum dots and the intermediate layer, and sharpens the interface between the quantum dots and the intermediate layer, thereby improving the infrared detection sensitivity. Typically, this quantum dot structure is preferably repeatedly stacked, thereby increasing the photocurrent with the number of layers.

Also known is a quantum infrared sensor that reduces noise, improves the S/N ratio, and has high reliability (see Patent Document 2, for example). In the quantum infrared sensor disclosed in Patent Document 2, a barrier layer below the quantum dots and a barrier layer above the quantum dots, which are provided to cover the quantum dots, and further below the barrier layer below the quantum dots, The upper barrier layer consists of a first region and a second region, and the second region has a lower Al concentration than the intermediate layer.

JP 2009-65142 A Japanese Patent Application Laid-Open No. 2019-21706

As described above, the quantum infrared sensor needs to be cooled, making it difficult to operate at room temperature. In addition, in order to increase the photocurrent and improve the sensitivity, the quantum dot structure is repeatedly stacked to increase the infrared absorption intensity and increase the sensitivity. It is difficult, and there is a fact that sufficient infrared absorption intensity cannot be secured.
In view of such circumstances, an object of the present invention is to provide a quantum infrared sensor that can operate at room temperature and detect infrared rays with high sensitivity.

As a result of extensive research, the present inventors have succeeded in generating intra-bandgap transitions with high optical transition probability by effectively confining only electrons in a quantum nanostructure through engineering of intra-bandgap transitions in compound semiconductors. Then, it was demonstrated that the intra-bandgap transition can cover from the near-infrared to the mid-infrared region, leading to the completion of the present invention.

The quantum infrared sensor of the present invention is an infrared sensor having an undoped compound semiconductor layer sandwiched between either or both of n-type and p-type doped compound semiconductor layers, wherein the undoped compound semiconductor layer is a hetero semiconductor layer of a different kind of semiconductor. At the junction, the heterointerface is provided with a quantum dot region that forms an intra-band level with a bandgap that can absorb the target infrared radiation. The quantum dot region then forms a conduction band energy level lower than the Fermi level.
The Fermi level is a place where the probability of electrons existing is 50%, but if the energy level of the conduction band at the heterointerface is lower than the Fermi level, a lot of electrons can be accumulated at the heterointerface. .
Here, the Fermi level is uniquely determined by the system (the device structure such as the impurity concentration and film thickness of the doped compound semiconductor layer, and the composition and film thickness of the undoped compound semiconductor layer sandwiched between them).

An important feature of the quantum infrared sensor of the present invention is that there are quantum dots at the hetero-interface of the undoped compound semiconductor layer.
In an ideal two-dimensional heterointerface, optical transitions between intraband levels are forbidden, but this prohibition can be broken by providing quantum dots at the heterointerface. On the other hand, in the case of a structure in which there is no heterointerface and only quantum dots are provided, a large number of electrons cannot be accumulated unless the number of layers of the quantum dot regions is simply increased.
The different semiconductors forming the heterojunction include group II-VI heterogeneous compound semiconductors, group III-V heterogeneous compound semiconductors, and group IV semiconductors such as Si-, Ge-, and C-based semiconductors.

In addition, the heterojunction in the quantum infrared sensor of the present invention has a composition and film thickness in which the difference in the band gaps of the heterogeneous semiconductors forming the heterointerface corresponds to the target infrared wavelength, and dislocations do not occur at the heterointerface. be.
In designing a heterojunction, it is necessary to select dissimilar semiconductors so that the difference in bandgap between the dissimilar semiconductors forming the heterointerface corresponds to the target infrared wavelength. In addition, the composition and film thickness are such that dislocations do not occur at the hetero interface. When dislocations (crystal defects) occur at heterointerfaces, non-radiative recombination occurs in the energy levels created by the dislocations, resulting in a decrease in signal intensity. It should be noted that the phrase "no dislocations occur" does not mean that dislocations do not occur at all, but means that dislocations do not substantially occur.
Here, one of the factors that causes dislocations to occur at the hetero-interface is the lattice constant mismatch due to the composition of the dissimilar semiconductor that constitutes the hetero-interface. do. That is, even if the lattice mismatch is small, dislocations are generated when the film thickness is large, and conversely, dislocations are not generated when the film thickness is thin even if the lattice mismatch is large. The film thickness at which dislocations occur is called the critical film thickness, which decreases as the lattice mismatch increases. In designing a heterojunction, it is important to select a composition and film thickness that do not generate dislocations at the heterointerface.
Note that when the film thickness is changed, the number of space charges changes, so the Fermi level also changes. Therefore, in designing a device having a heterojunction, film thickness control has two aspects: strain control and Fermi level control, and the film thickness is optimized for each device design. It is necessary.

The undoped compound semiconductor layer (hereinafter also referred to as i-layer) in the quantum infrared sensor is either an n-type doped compound semiconductor layer (hereinafter also referred to as n-layer) or a p-type doped compound semiconductor layer (hereinafter also referred to as p-layer). n-layer-i-layer-n-layer, p-layer-i-p-layer, n-layer-i-p-layer, or p-layer-i-n-layer . Preferably, the i-layer is sandwiched between the n-layers that control the Fermi level.

In the quantum infrared sensor of the present invention, the quantum dot region is composed of a single layer or multiple layers and has a thickness of 50 nm or less. In conventionally known quantum infrared sensors, the detection sensitivity was not increased unless several layers of quantum dot regions were laminated. Sensitivity is obtained.

In the quantum infrared sensor of the present invention, the heterojunction may be composed of a III-V group compound semiconductor, and the quantum dot region may be composed of quantum dots of InAs, InSb, InGaAs, GaSb, Ge or HgCdTe. This is a preferred embodiment.

In the quantum infrared sensor of the present invention, the undoped compound semiconductor layer is specifically a heterojunction of _{AlaGa1 -aAs} (0<a≤1) and GaAs, and the quantum dot region is an InAs quantum dot. formed by In the case of such an undoped compound semiconductor layer structure, the target infrared rays are in the wavelength range of 1 to 14 μm. The target infrared rays may be in the wavelength range of 1 to 7 μm.

The quantum infrared sensor of the present invention can operate not only at low temperatures but also at room temperature. The quantum infrared sensor of the present invention is characterized by accumulating a large amount of electrons in one hetero-interface and exciting them to an intra-band level formed in the quantum dot region by infrared light. Therefore, once it escapes from the heterointerface, it can be detected as a photocurrent. In addition, the density of states at the bulk heterointerface is much larger than that of quantum dots. The quantum infrared sensor of the present invention utilizes high-density electrons that can be accumulated in heterointerfaces with a very high density of states.
On the other hand, in conventional quantum infrared sensors, in which ordinary quantum dots are stacked in multiple layers instead of using high-density electrons at heterointerfaces, the intra-band level changes according to the number of quantum dot stacks. Although the number of carriers excited in the direction increases, at the same time there is recapture by the quantum dots continuing in the conduction direction, resulting in a structure with a large loss. For this reason, it is difficult for conventional quantum infrared sensors to achieve high sensitivity at room temperature.

An imaging device using the quantum infrared sensor of the present invention includes the quantum infrared sensor of the present invention described above and a drive circuit for driving the infrared sensor.

The manufacturing method of the quantum infrared sensor of the present invention comprises the following steps 1) and 2).
1) A step of selecting a composition and a film thickness of the hetero-semiconductor that composes the hetero-interface so that the difference in the bandgap of the hetero-semiconductor corresponds to the target infrared wavelength and that dislocations do not occur at the hetero-interface.
2) A step of forming a quantum dot region at the heterointerface that forms an intra-band level of a bandgap capable of absorbing target infrared radiation and an energy level of a conduction band lower than the Fermi level.

Advantageous Effects of Invention The quantum infrared sensor of the present invention can operate at room temperature and can detect target infrared rays with high sensitivity.

Schematic configuration diagram of the quantum infrared sensor of Example 1 Explanatory drawing of the configuration of the quantum infrared sensor of the first embodiment Band diagram and electric field distribution diagram in the quantum infrared sensor of Example 1 Explanatory diagram of the band state of the hetero interface of the quantum infrared sensor of Example 1 Explanatory drawing of the band state of the quantum infrared sensor of Example 1 Explanatory diagram of changes in band state due to differences in various bias voltages Infrared sensor circuit diagram Infrared light response spectrum of the quantum infrared sensor of Example 1 Graph showing dark current with different bias voltages ΔJ/P spectra at various temperatures with different bias voltages Graph showing photocurrent (ΔI) and ΔI/I under different bias voltages Graph showing infrared light output density dependence of ΔI under bias voltage Infrared response spectrum at 295K and 15K

An example of an embodiment of the present invention will be described in detail below with reference to the drawings. The scope of the present invention is not limited to the following examples and illustrated examples, and many modifications and variations are possible.

FIG. 1 shows a schematic configuration diagram of a quantum infrared sensor in one embodiment of the present invention. As shown in FIG. 1, a quantum infrared sensor 1 of the present invention comprises an n-type doped compound semiconductor layer 2, an n-type doped compound semiconductor layer 3, an undoped compound semiconductor layer 4 sandwiched between them, and an electrode 5. structure. The undoped compound semiconductor layer 4 is composed of a heterojunction of different kinds of semiconductors, and is characterized in that the heterointerface 6 is provided with the quantum dot region 7 . Underneath the n-type doped compound semiconductor layer 3 is a semiconductor substrate 8, under which a backside electrode 52 is located. An electrode 51 is provided on the upper portion of the n-type doped compound semiconductor layer 2, and the energy of infrared light incident from above is converted by the undoped compound semiconductor layer 4 and detected as a photocurrent.
In the quantum dot region 7 of the undoped compound semiconductor layer 4, electrons excited by infrared light escape from the quantum dot wells, and many electrons accumulate at the hetero interface 6, which can be taken out as photocurrent.

A specific configuration of the infrared sensor device of Example 1 will be described.
The infrared sensor _of Example ₁ , as shown in FIG. A heterojunction of Al _0.3 Ga _0.7 As and GaAs is formed as the ⁺ −GaAs, undoped compound semiconductor layer 4 , and a quantum dot region 7 of InAs quantum dots is formed at the hetero interface 6 . The film thickness, carrier density, and quantum dot density of the nin structure are shown in the schematic diagram of FIG. The nin structure is stacked in order on an n-GaAs semiconductor substrate 8, and electrodes 5 are provided on the top and bottom surfaces, respectively. In Example 1, the quantum dot region 7 is a single layer, but a plurality of quantum dot regions 7 may be laminated.

FIG. 3 shows the band diagram at 300 K with a bias voltage of 0 V on the device surface of the fabricated infrared sensor (FIG. 3 a; upper diagram), and when bias voltages of −1 V, 0 V and 1 V are applied to the device surface of the infrared sensor. The electric field distribution (Fig. 3b; bottom) is shown.
As shown in the lower part of FIG. 3, the internal electric field is strong in the vicinity of the heterointerface, and excited electrons are likely to be pulled out to the barrier side of Al _0.3 Ga _0.7 As. Efficient intra-band transitions can be generated by inserting quantum dot regions 7 (hereinafter also referred to as QD layers) that have sensitivity to light from arbitrary directions and three-dimensional electron confinement at the heterointerface.

A method of manufacturing the infrared sensor device of Example 1 will be described.
The infrared sensor device of Example 1 was fabricated on an n ⁺ -GaAs(001) substrate using solid source molecular beam epitaxy. First, a 400 nm-thick n ⁺ -GaAs layer was crystal-grown on the substrate as a buffer layer. During crystal growth, the substrate temperature was monitored using an infrared pyrometer. Thereafter, on the buffer layer of the n ⁺ -GaAs layer, GaAs with a thickness of 300 nm is deposited as an undoped compound semiconductor layer to form a QD layer, GaAs is further deposited with a thickness of 10 nm, and Al _0.3 Ga _0.7 with a thickness of 20 nm is deposited. As was deposited to form an intrinsic carrier layer having a heterojunction compound semiconductor structure of Al _0.3 Ga _0.7 As/GaAs.
The nominal thickness of InAs was 0.64 nm (2.1 monolayers). The substrate temperature is 550° C. before forming the InAs quantum dots. An InAs QD layer followed by a 10 nm GaAs capping layer was grown at 490°C. Finally, an n-Al _0.3 Ga _0.7 As, n ⁺ -GaAs layer was grown at a substrate temperature of 500° C. as a contact layer. The beam equivalent pressure of As ₂ flux was 1.15×10 ⁻³ Pa. Next, Au--Ge/Au electrodes were formed on the upper and lower surfaces, respectively.

The fabricated sample surface is defined in FIG. 3 as position=0 nm and the Al _0.3 Ga _0.7 As barrier height is about 230 meV. When a positive (negative) bias is applied, electrons excited by infrared light drift to the n-Al _0.3 Ga _0.7 As (GaAs) side. At the heterointerface (position = 400 nm), the electron Fermi level (E _F ) indicated by the dashed line in the figure is higher than the bottom level (E _C ) of the conduction band, which is due to the high density of electrons. indicates that there is FIG. 4 shows an enlarged view of the heterointerface (position=400 nm) in the upper band diagram of _FIG . _C ) is formed. A large amount of electrons are accumulated in this portion. At this position, when the bias voltage is 0 V, the bottom level of the conduction band (E _C )−the Fermi level of the electron (E _F )=−0.0014 (eV), and the electron carrier density is 3.5. ×10 ¹⁷ cm ⁻³ .

In FIG. 5, the orientation of the band diagram is changed, and the positions of the schematic diagrams are combined. At the hetero interface (position = 400 nm) where InAs quantum dots are doped, the bandgap changes sharply and the conduction band energy level (E _C ) lower than the Fermi level (E _F ) is formed. As a result, a large amount of carrier electrons can be accumulated in this hetero-interface, so that the amount of light can be increased and the sensitivity can be enhanced.
FIG. 6 shows changes in band states under bias voltages (+1 V, -1 V) in Example 1. FIG. The dashed lines in the figure indicate the Fermi level of electrons (E _F ), the bottom level of the conduction band (E _C ), or the level of the valence band (E _V ).

FIG. 7 shows a circuit for applying a bias voltage to a device of an infrared sensor and detecting a photocurrent generated when infrared rays are incident on the device. It measures the photocurrent output from the device and detects infrared rays.

FIG. 8 shows the infrared photoresponse spectrum of the infrared sensor device of Example 1 at room temperature (295K). As can be seen from FIG. 8, in the infrared sensor device of Example 1, three peaks appear in the spectrum near 3 μm, 4.5 μm, and 6.5 μm, corresponding to intraband transitions in the heterostructure. . In the case of the infrared photoresponse spectrum of the conventional infrared sensor, the photocurrent due to the incidence of short to medium wavelength infrared rays of 1 to 5 μm was small. The amount of photocurrent due to the incidence of infrared rays of medium wavelength is increased by about ten times, and the detection sensitivity of infrared rays is improved by about ten times.

FIG. 9 shows the dark current at different bias voltages of 15K and 290K for the infrared sensor device shown in the schematic diagram of FIG. When a voltage is applied to the device surface, electrons are drawn from the Al _0.3 Ga _0.7 As (GaAs) side with a positive (negative) bias, respectively, generating current.

Next, in order to confirm the effect of the buffer layer (barrier layer) of Al _0.3 Ga _0.7 As on electrons, the temperature dependence of photoresponse at wavelengths of 700 to 1000 nm was measured. FIG. 10 shows the results of the temperature dependence of the optical response ΔI/P at ±1V. Here, ΔI represents the photocurrent and P represents the light intensity. Absorption edges of wetting layers of GaAs and InAs at this wavelength were confirmed.
That is, at −1 V, electrons excited by the interband transition of GaAs reach the electrode due to the electric field. At low temperatures, the absorption edge of GaAs is relatively steep. As the temperature increases, the absorption edge shifts and the sub-gap state due to the wetting layer of InAs appears clearly. At a bias voltage of 1 V and around room temperature, the absorption edge of GaAs is observed, but it is not clearly observed at cryogenic temperatures. This indicates that electrons excited in GaAs are blocked by the Al _0.3 Ga _0.7 As barrier and therefore cannot be drawn out due to current flow at low temperatures.
As a result, the extraction of carriers by the electric field is reduced, and electrons are expected to be densely distributed at the hetero-interface. Above 160 K, the GaAs absorption edge appears gradually with increasing temperature. Some electrons are extracted under the influence of thermal excitation. These results clearly show the effect of the Al _0.3 Ga _0.7 As barrier in the nin layer structure of the infrared sensor device of this example, and the difference in how electrons are extracted by changing the positive or negative bias voltage. became.

Next, the infrared light response due to intra-band transition will be described.
A solid-state laser with a wavelength of 1319 nm was used to induce an intraband transition, and the light intensity dependence of the photocurrent was measured at 290 K with different bias voltages. show. The laser spot size was approximately 0.012 cm ² . The photocurrent increased with increasing light intensity and bias voltage, both positive and negative. The lower graphs of FIGS. 11(1) and 11(2) show the bias dependence of ΔI/I. ΔI/I represents the ratio of photocurrent to total current. ΔI/I has a peak at ±0.2V. By applying a voltage, extraction of excited carrier electrons is increased.

On the other hand, when the electric field exceeds a certain electric field, the current due to carrier extraction by the electric field becomes dominant, and ΔI/I decreases. In other words, it was shown that the bias voltage of ±0.2 V can extract the carrier electrons excited by the electric field most efficiently. FIG. 12 shows the infrared light-pump power dependence of ΔJ at 290K and 15K. Excited carrier electrons, which increase with excitation power, are effectively extracted by the increased electric field. Comparing the results at each temperature, the dark current changed compared to FIG. 9, but the photocurrent was almost the same, suggesting that the photocurrent observed by irradiation with infrared light was not due to thermal artifacts. is shown.

Next, when _the PL spectrum is measured and the quantum level at 295 K is calculated, the energy difference between each excitation level and the ground level is were E ₁ −E ₀ =65 meV, E ₂ −E ₀ =128 meV and E ₃ −E ₀ =198 meV.

FIG. 13 shows the infrared response spectrum of the infrared sensor device of Example 1 for short wavelength infrared rays (1.0 to 1.8 μm) and medium wavelength infrared rays (1.8 to 7.0 μm) at 295 K and 15 K. show. A SiC lamp dispersed by a 320 mm single monochromator was used for excitation. It can be seen that the infrared sensor device of Example 1 is very sensitive to medium wavelength infrared radiation even at room temperature, as several peaks appear in the spectrum corresponding to intraband transitions in the heterostructure. As shown in FIG. 13, three peaks were observed near 3 μm, 4.5 μm and 6.5 μm at both 295K and 15K. In particular, broad peaks appeared near 3 μm and 6.5 μm. The maximum sensitivity was 0.62 A/W. The peak around 3 μm results from an intraband transition from the quantum dot energy levels (E ₀ , E ₁ ) to the Al _0.3 Ga _0.7 As (GaAs) conduction band edge at each bias. Furthermore, the peak around 6.5 μm is derived from the intraband transition from the confined state formed at the heterointerface to the conduction band edge of Al _0.3 Ga _0.7 As at 1 V. Near the surface, the GaAs conduction band edge transitions to that of Al _0.3 Ga _0.7 As. The dip in the spectrum near 6.5 μm is due to absorption by _H2O .

The infrared sensor of the present invention is a new type of infrared light sensor sensitized with quantum dots intercalated into Al _0.3 Ga _0.7 As/GaAs heterointerfaces for infrared light detection at high temperatures. As shown in the photoelectric conversion characteristics described above, the difference in the method of extracting electrons by the heterostructure is shown depending on whether the bias voltage is positive or negative. When a positive bias is applied to the surface, the electrons are densely distributed because the Al _0.3 Ga _0.7 As barrier blocks them. Therefore, efficient infrared absorption can be expected. Further, in the measurement of the infrared light response, a clear peak was observed at a maximum optical response of 0.62 A/W at about 3 μm and 6.5 μm at 295 K, and particularly at about 6.5 μm at 1 V. It was shown that a structure in which quantum dots are inserted into the _0.3 Ga _0.7 As/GaAs heterointerface functions as a highly sensitive infrared sensor that can operate even at room temperature.

(Other examples)
(1) In Example 1, the undoped compound semiconductor layer (i-layer) has a nin configuration sandwiched between n-type doped compound semiconductor layers (n-layers), but is not limited to this. pi-p configuration in which the i-type layer is sandwiched between p-type doped compound semiconductor layers (p-layers), or n-layer, i-layer, and p-layer nip in order from the incident direction of infrared rays or a pin structure of p-layer, i-layer and n-layer.
(2) In Example 1, the quantum dot region of the heterointerface is a single layer, but a plurality of quantum dot regions 7 can be laminated to form a multilayer.
(3) In Example 1, InAs quantum dots were formed at the heterointerface, but quantum dots of other narrow bandgap semiconductors InSb, InAsSb, GaSb, Ge or HgCdTe can be formed.
(4) In Example 1, an AlGaAs/GaAs heterojunction was used as the undoped compound semiconductor layer (i-layer). Group IV semiconductors such as Ge-based and C-based semiconductors can be used.

INDUSTRIAL APPLICABILITY The present invention is useful as a quantum infrared sensor that operates at room temperature. If a quantum infrared sensor with high sensitivity at room temperature is put into practical use, it can be expected to replace the low-sensitivity, slow-response pyroelectric sensor that has been widely used, and bring about a major market change.

1 quantum infrared sensor 2 n-type doped compound semiconductor layer (surface side)
3 n-type doped compound semiconductor layer 4 undoped compound semiconductor layer 5, 51, 52 electrode 6 hetero interface 7 quantum dot region 8 semiconductor substrate

Claims (9)

An infrared sensor having an undoped compound semiconductor layer sandwiched between either or both of n-type or p-type doped compound semiconductor layers,
The undoped compound semiconductor layer is a heterojunction of different semiconductors, and has a quantum dot region at the hetero interface that forms an intra-band level of a bandgap that can absorb the target infrared ray,
The quantum dot region forms an energy level of a conduction band lower than the Fermi level, and the electrons accumulated at the hetero interface are excited by infrared rays to an intra-band level formed in the quantum dot region and detected as a photocurrent. A quantum infrared sensor characterized by : The heterojunction is characterized in that the difference in bandgap between dissimilar semiconductors forming the heterointerface corresponds to the target infrared wavelength, and has a composition and a film thickness that do not generate dislocations at the heterointerface. The quantum infrared sensor according to claim 1. 3. The quantum infrared sensor according to claim 1, wherein the undoped compound semiconductor layer is sandwiched between n-type doped compound semiconductor layers that control the Fermi level. 4. The quantum infrared sensor according to claim 1, wherein the quantum dot region is composed of a single layer or multiple layers and has a thickness of 50 nm or less. The heterojunction is composed of a III-V group compound semiconductor,
5. A quantum infrared sensor according to claim 1, wherein said quantum dot region is formed of quantum dots of InAs, InSb, InGaAs, GaSb, Ge or HgCdTe. The undoped compound semiconductor layer is a heterojunction of AlaGa1-aAs (0<a≦1) and GaAs, the quantum dot region is formed of InAs quantum dots, and the target infrared rays are in the wavelength range of 1 to 14 μm. 6. The quantum infrared sensor according to any one of claims 1 to 5, characterized in that: 7. The quantum infrared sensor according to claim 1, wherein the quantum infrared sensor is operable at room temperature. An imaging device using a quantum infrared sensor, comprising: the quantum infrared sensor according to any one of claims 1 to 7; and a driving circuit for driving the infrared sensor. A method for manufacturing a quantum infrared sensor according to any one of claims 1 to 7,
a step of selecting a composition and a film thickness of a hetero-semiconductor that composes the hetero-interface so that the bandgap difference of the hetero-semiconductor corresponds to the target infrared wavelength and that dislocations do not occur at the hetero-interface;
A step of forming a quantum dot region at the heterointerface that forms an intra-band level of a bandgap capable of absorbing the target infrared rays and forms an energy level of a conduction band lower than the Fermi level;
A method of manufacturing a quantum infrared sensor, comprising:

Images