JP5278291B2 - Quantum dot photodetector and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide sufficient sensitivity by improving quantum efficiency, and to improve performance of a quantum dot photodetector, in a quantum dot photodetector. <P>SOLUTION: The quantum dot photodetector includes: a columnar quantum dot layer 2 including a plurality of quantum dot layers 5 each including quantum dots 5A and a first embedding layer 5B for embedding the quantum dots 5A therein, wherein the quantum dots 5A included in the plurality of respective quantum dot layers 5 are aligned in the lamination direction to form columnar quantum dots 2A; two electrode layers 3 sandwiching the columnar quantum dot layer 2; and a carrier supplying quantum dot layer 4 formed between the columnar quantum dot layer 2 and the carrier supply-side electrode layer 3A out of the two electrode layers 3, contacting the carrier supply-side electrode layer 3A, and including carrier-supplying quantum dots 4A doped with impurities, and a second embedding layer 4B for embedding the carrier-supplying quantum dots 4A. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a quantum dot photodetector and a method for manufacturing the same.

In recent years, quantum dot photodetectors have attracted attention among photodetectors that detect light by capturing a current that flows when incident light is absorbed.
The conventional quantum well photodetector could not absorb normal incident light, but the quantum dot photodetector can confine carriers in three dimensions and absorb normal incident light.
A typical example is a quantum dot infrared detector.

Here, FIG. 4 is a schematic cross-sectional view showing the structure of a standard quantum dot infrared detector.
As shown in FIG. 4, in a standard quantum dot type infrared detector, an InAs quantum dot embedded with an i-GaAs intermediate layer (embedded layer) is used as a quantum dot layer, and a plurality of stacked quantum dot layers are formed. The quantum dot layer (or one quantum dot layer) is sandwiched between n-GaAs electrode layers.

  Thus, the quantum dot infrared detector has a structure in which an active region formed by embedding quantum dots in an intermediate layer is sandwiched between electrode layers. When infrared rays are incident on the active region, the electrons bound in the quantum dots are excited, and a photocurrent is generated according to the amount of incident infrared rays. By detecting this, infrared rays are detected. Yes.

JP 2008-91420 A

However, in the conventional quantum dot infrared detector, for example, when the quantum dot layer is 30 layers and the dot density is 2 × 10 ¹⁰ cm ⁻² , the quantum efficiency is about 3%, and sufficient sensitivity is obtained. Absent. This is because the quantum efficiency per quantum dot is as small as about 5 × 10 ⁻¹² %.
As measures for improving the quantum efficiency, for example, increasing the dot density or increasing the number of stacked layers can be considered.

In addition, as shown in FIG. 5, when stacking a plurality of quantum dot layers, the quantum dots are aligned in the growth direction by forming the interlayer distance of each quantum dot layer less than 30 nm to form columnar quantum dots. Is also possible.
Here, in order for the quantum dots to feel light, carriers (electrons) must be contained in the quantum dots.

In the conventional quantum dot infrared detector, the quantum dots are randomly arranged, so that it is difficult for carriers to be supplied via the quantum dots included in the adjacent quantum dot layers. Carriers are supplied from the surroundings.
In contrast, in a quantum dot infrared detector using columnar quantum dots, the quantum dots are aligned in the growth direction, so that carriers are supplied via the quantum dots included in the adjacent quantum dot layers. Therefore, it is expected that the supply of carriers becomes easy and the infrared absorption probability is increased.

However, experiments have shown that quantum efficiency does not change even with quantum dot infrared detectors using columnar quantum dots.
This is the same value as the conventional quantum dot infrared detector and the quantum dot infrared detector using columnar quantum dots with the same fill factor (percentage of quantum dots in the plane) in one quantum dot layer. If f is the number of stacked layers and n, the probability that the incident infrared ray hits the quantum dot is f * n, which is considered to be the same. The value of the fill factor f is usually about 0.2 to 0.5.

  Therefore, in a quantum dot type photodetector, it is desired to improve quantum efficiency and obtain sufficient sensitivity and improve its performance.

  Therefore, the quantum dot photodetector includes a plurality of quantum dot layers including a quantum dot and a first embedded layer that embeds the quantum dot, and the quantum dots included in each of the plurality of quantum dot layers are stacked in the stacking direction. Between the columnar quantum dot layer constituting the columnar quantum dot, the two electrode layers sandwiching the columnar quantum dot layer, and the columnar quantum dot layer and the electrode layer on the carrier supply side of the two electrode layers A carrier supply quantum dot layer including a carrier supply quantum dot that is in contact with the carrier supply side electrode layer and is doped with an impurity, and a second embedded layer that embeds the carrier supply quantum dot. It is a requirement to prepare.

  The manufacturing method of this quantum dot type photo detector forms a carrier supplying quantum dot doped with an impurity so as to be in contact with the surface of the electrode layer, and includes a columner quantum dot directly above the carrier supplying quantum dot. It is necessary to form a columnar quantum dot layer and to form an electrode layer on the columnar quantum dot layer.

  Therefore, according to the quantum dot photodetector and the manufacturing method thereof, there is an advantage that the quantum efficiency can be improved and sufficient sensitivity can be obtained, and the performance can be improved.

It is a typical sectional view showing the composition of the quantum dot type infrared detector concerning this embodiment. (A), (B) is typical sectional drawing which shows the structure of the modification of the quantum dot type | mold infrared detector concerning this embodiment. It is typical sectional drawing which shows the structure of the other modification of the quantum dot type | mold infrared detector concerning this embodiment. It is typical sectional drawing which shows the structure of the conventional quantum dot type | mold infrared detector. It is typical sectional drawing which shows the structure considered in the creation process of the quantum dot type | mold infrared detector concerning this embodiment.

Hereinafter, the quantum dot photodetector and the manufacturing method thereof according to the present embodiment will be described with reference to FIGS.
In the present embodiment, the quantum dot photodetector is a light receiving device using self-assembled quantum dots that absorbs infrared rays by quantum dots and generates a photocurrent according to the amount of incident infrared rays. A type infrared detector will be described as an example.

As shown in FIG. 1, the quantum dot infrared detector includes a columnar quantum dot layer 2 (active layer; absorption layer) and two electrode layers 3 (contacts) sandwiching the columner quantum dot layer 2 on a semiconductor substrate 1. Layer), and the columnar quantum dot layer 2 and the carrier supplying quantum dot layer 4 provided between the two electrode layers 3 and the electrode layer 3A on the carrier supply side.
Here, the carrier supply quantum dot layer 4 is in contact with the carrier supply side electrode layer 3A and is filled with a plurality of carrier supply quantum dots 4A doped with impurities and embedded with these carrier supply quantum dots 4A. And a buried layer 4B (second buried layer).

  That is, the plurality of carrier supply quantum dots 4A are formed directly on the carrier supply side electrode layer 3A. Only these carrier supply quantum dots 4A are doped with impurities (impurities of the same conductivity type as the electrode layers). That is, the buried layer 4B in which the columnar quantum dot layer 2 and the carrier supply quantum dot 4A are embedded is not doped with impurities, and a plurality of carrier supply quantum formed directly on the carrier supply side electrode layer 3A. Only the dots 4A are doped with impurities.

Here, the plurality of carrier supply quantum dots 4A are doped with impurities at a high concentration so that one or more carriers enter one quantum dot. That is, the doping amount of the carrier supplying quantum dots 4A is 1 electron / 1 dot or more. As a result, carriers can be reliably supplied to the columnar quantum dots 2A.
The columnar quantum dot layer 2 includes a plurality of quantum dot layers 5 including a plurality of quantum dots 5A and an embedded layer 5B (first embedded layer) that embeds these quantum dots 5A.

In the columnar quantum dot layer 2, the quantum dots 5A included in each of the plurality of quantum dot layers 5 are aligned in the stacking direction to form the columner quantum dot 2A.
Here, the quantum dots 5A included in each of the plurality of quantum dot layers 5 constituting the carrier supplying quantum dots 4A and the columnar quantum dot layer 2 are aligned in the stacking direction. That is, a plurality (multiple stages) of quantum dots 5A constituting the columner quantum dots 2A are aligned above the carrier supply quantum dots 4A in the stacking direction.

  Here, the columnar quantum dot layer 2 is described as being formed on the carrier supply quantum dot layer 4, but the whole including the carrier supply quantum dot layer may be regarded as a columnar quantum dot layer. it can. That is, it can be seen that the quantum dot layer in the lowermost layer (first layer; first stage) of the columnar quantum dot layer is a carrier supply quantum dot layer including quantum dots doped with impurities.

As described above, the carrier supply quantum dot 4A is formed directly on the carrier supply side electrode layer 3A, and the carrier supply quantum dot 4A is doped with impurities, and the carrier supply quantum dot 4A and the columnar The quantum dots 5A included in each of the plurality of quantum dot layers 5 constituting the quantum dot layer 2 are aligned in the stacking direction.
Thereby, carriers are supplied from the carrier supply side electrode layer 3A to the quantum dots 5A included in each of the plurality of quantum dot layers 5 constituting the columnar quantum dot layer 2 via the carrier supply quantum dots 4A. Will be.

  In this case, the carrier supply quantum dots 4A form a protrusion with a thin tip on the carrier supply side electrode layer 3A, which becomes a carrier supply structure (carrier supply source). That is, carriers supplied from the carrier supply side electrode layer 3A are emitted from the tips of the carrier supply quantum dots 4A. Also, by providing the carrier supply quantum dots 4A, the distance between the carrier supply source and the quantum dots 5A closest to the carrier supply side electrode layer 3A constituting the columner quantum dots 2A is also shortened. For this reason, carriers can be reliably supplied to the columnar quantum dots 2A, and the quantum efficiency can be improved. As a result, the characteristics of the quantum dot infrared detector can be improved.

  On the other hand, in the quantum dot infrared detector using columnar quantum dots as shown in FIG. 5, when supplying carriers from the electrode layer on the carrier supply side to each quantum dot constituting the columnar quantum dots, Since carriers are likely to flow even in a region where no is formed, supply efficiency of carriers to columnar quantum dots is poor, and it is difficult to improve quantum efficiency.

By the way, in this embodiment, as shown in FIG. 1, it is preferable that the interlayer distance of the several quantum dot layer 5 and the quantum dot layer 4 for carrier supply shall be 10 nm or more and less than 30 nm.
This is because if the thickness is less than 10 nm, the wave functions between the quantum dots 4A and 5A included in each of the quantum dot layers 4 and 5 are overlapped to form one quantum dot. Further, when the thickness is 30 nm or more, the plurality of quantum dots 5A (4A) are not the columnar quantum dots 2A aligned in the stacking direction, but become regular quantum dots randomly arranged.

As described above, in the columnar quantum dot 2A of the present embodiment, although the plurality of quantum dots 5A (4A) are aligned in the stacking direction, the plurality of quantum dots 5A (4A) (quantums at each stage) are aligned in the stacking direction. Dot) function as independent quantum dots.
Here, although the quantum dot infrared detector is configured to include one columnar quantum dot layer 2, the present invention is not limited to this.

For example, as shown in FIGS. 2A and 2B, the quantum dot infrared detector may be configured to include a plurality of columnar quantum dot layers 2. Thereby, quantum efficiency can be improved further.
In this case, as shown in FIG. 2B, a plurality of quantum dots for supplying carriers (another impurity having the same conductivity type as that of the electrode layer) are doped between the plurality of columnar quantum dot layers 2. It is preferable to include a carrier supply quantum dot layer 6 including a carrier supply quantum dot) 6A and an embedded layer 6B (third embedded layer) in which these carrier supply quantum dots 6A are embedded.

Further, as shown in FIG. 2 (A), a carrier supply semiconductor layer 7 doped with impurities (impurities having the same conductivity type as the electrode layers) is provided between the plurality of columnar quantum dot layers 2; The plurality of carrier supplying quantum dots 6A may be in contact with the side opposite to the carrier supplying side electrode layer 3A side of the carrier supplying semiconductor layer 7.
In this case, the carrier supply quantum dots 6A are doped with impurities at a high concentration so that one or more carriers enter one quantum dot, like the carrier supply quantum dots 4A described above. As a result, carriers can be reliably supplied to the columnar quantum dots 2A.

In addition, when the plurality of columnar quantum dot layers 2 are provided in this way, the interlayer distance between the plurality of columnar quantum dot layers 2 is preferably 30 nm or more.
By setting it to 30 nm or more, the upper and lower columnar quantum dot layers 2 can be separated and made independent. That is, when the upper columnar quantum dot layer 2 is formed, it is possible to prevent the columnar quantum dot layer 2A included in the lower columnar quantum dot layer 2 from being affected. As a result, it is possible to prevent the influence of distortion from increasing and causing crystal defects.

Next, the manufacturing method of the quantum dot type infrared detector concerning this embodiment is demonstrated.
First, carrier supply quantum dots 4A doped with impurities are formed so as to be in contact with the surface of the electrode layer 3A.
Next, the columner quantum dot layer 2 including the columner quantum dots 2A is formed immediately above the carrier supply quantum dots 4A.

Then, the electrode layer 3 is formed on the columnar quantum dot layer 2.
Thereby, the quantum dot type infrared detector configured as described above is manufactured.
More specific description will be given below.
Here, a manufacturing method of a quantum dot infrared detector including a plurality of columnar quantum dot layers 2 and including a carrier supply quantum dot layer 6 and a carrier supply semiconductor layer 7 between the columnar quantum dot layers 2 is taken as an example. This will be described with reference to FIG.

First, the n-GaAs electrode layer 3A (carrier supply side electrode layer; carrier concentration n = 1 × 10 ¹⁸ cm ⁻³ ) is formed on the GaAs substrate 1 by, for example, MBE so as to have a thickness of 1000 nm, for example. .
Next, for example, the first-stage quantum dots 4A are formed at a substrate temperature of 500 ° C., an InAs growth rate of 0.1 ML / sec, and an InAs supply amount of 2.1 ML. Here, InAs quantum dots 4A having a dot density of 2.5 × 10 ¹⁰ cm ⁻² , a height of 6 nm, and a dot diameter of 30 nm are formed.

  In particular, in the present embodiment, the first-stage quantum dots 4A are doped with an n-type impurity (for example, Si). Here, the doping amount is adjusted by adjusting the cell temperature of the impurity supply source. Thereby, about 2 to 10 (for example, 5) carriers (electrons) per quantum dot are entered. That is, the impurity is doped at a high concentration so that one or more carriers enter one quantum dot.

Next, for example, an i-GaAs buried layer 4B having a thickness of 20 nm is formed. That is, the first-stage quantum dot layer 4 is formed by embedding the first-stage quantum dots 4A with the i-GaAs buried layer 4B.
Subsequently, for example, the second-stage quantum dots 5A are formed at an InAs growth rate of 0.1 ML / sec and an InAs supply amount of 2.1 ML. Here, InAs quantum dots 5A having a dot density of 2.5 × 10 ¹⁰ cm ⁻² , a height of 6 nm, and a dot diameter of 30 nm are formed. Such quantum dots 5A can detect infrared rays having a wavelength of about 6 μm. In particular, in the present embodiment, the second-stage quantum dots 5A are non-doped.

Further, for example, an i-GaAs buried layer 5B having a thickness of 20 nm is formed. That is, the second-stage quantum dot layer 5 is formed by embedding the second-stage quantum dots 5A (non-doped) with the i-GaAs buried layer 5B.
Thereafter, similarly to the formation of the second-stage quantum dot layer 5, the third-stage, fourth-stage, and fifth-stage quantum dot layers 5 are formed. However, the thickness of the i-GaAs buried layer 5B formed after the fifth-stage quantum dots 5 are formed is, for example, 50 nm.

Here, since the thickness of the i-GaAs buried layer 5B, that is, the interlayer distance between the quantum dot layers 5 is 20 nm, the first to fifth quantum dots 5A are aligned in the stacking direction. Will be formed. That is, columnar quantum dots formed by stacking five stages of quantum dots 4A and 5A are formed on the n-GaAs electrode layer 3A.
In the present embodiment, the first-stage quantum dots 4A are carrier supply quantum dots that are formed directly on the electrode layer 3A on the carrier supply side, doped with impurities, and function as a carrier supply source. On the other hand, the quantum dots 5A in the second to fifth stages constitute columnar quantum dots 2A that function as an infrared detector. For this reason, the columnar quantum dot 2A (infrared detection) is composed of the quantum dots 5A in the second to fifth stages on the carrier supply quantum dot layer 4 including the first stage carrier supply quantum dots 4A and functions as an infrared detection unit. The columnar quantum dot layer 2 (infrared detecting columnar quantum dot layer) including the columnar quantum dots for use is stacked.

In this way, the first columnar quantum dot layer 2 is formed on the first carrier supply quantum dot layer 4 in which the four-stage quantum dots 5A are aligned in the stacking direction.
Next, the second carrier supplying quantum dot layer 6 and the columner quantum dot layer 2 are formed.
That is, first, the n-GaAs layer 7 (carrier concentration n = 1 × 10 ¹⁸ cm ⁻³ ) is formed on the 50-nm-thick i-GaAs buried layer 5B constituting the first columnar quantum dot layer 2 described above. Is formed to a thickness of, for example, 5 nm. The n-GaAs layer 7 is a carrier supply semiconductor layer for supplying carriers to the second columnar quantum dot layer 2.

Next, the second carrier supply quantum dot layer 6 is formed in the same manner as the formation of the first carrier supply quantum dot layer 4 described above.
Then, the second columnar quantum dot layer 2 is formed in the same manner as the first columnar quantum dot layer 2 described above.
In this way, the second columnar quantum dot layer 2 in which the four quantum dots 5A are aligned in the stacking direction is formed on the second carrier supply quantum dot layer 6. That is, on the first columnar quantum dot layer 2, the second carrier supplying quantum dot layer 6 and the second columnar quantum are interposed via the carrier supplying semiconductor layer 7 (n-GaAs layer). A dot layer 2 is formed.

  As described above, the thickness of the uppermost i-GaAs buried layer 5B of the first columnar quantum dot layer 2 is 50 nm, for example, and the first columnar quantum dot layer 2 and the second layer Since the interlayer distance of the columnar quantum dot layer 2 is 30 nm or more, the second columnar quantum dot layer is not affected by the arrangement of the columnar quantum dots 2A included in the first columnar quantum dot layer 2. Columnar quantum dots 2A included in 2 can be formed.

Thereafter, this process is repeated eight times, and the third to tenth carrier supplying quantum dot layers 6 and the columnar quantum dot layer 2 are formed via the carrier supplying semiconductor layer 7 (n-GaAs layer). Form.
In this manner, a semiconductor crystal having a structure in which 10 layers of the columnar quantum dot layer 2 in which the carrier supplying quantum dot layer 6 and the four-stage quantum dots 5A are aligned in the stacking direction are stacked is formed.

An n-GaAs electrode layer 3 (carrier concentration n = 1 × 10 ¹⁸ cm ⁻³ ) is, for example, 500 nm on the 50-nm thick i-GaAs buried layer 5B constituting the tenth columnar quantum dot layer 2. It forms so that it may become thickness.
Thereafter, using the wafer formed by crystal growth in this way, a part thereof is etched away in a mesa shape to expose the lower n-GaAs electrode layer 3A.

Finally, a metal electrode (not shown) made of, for example, AuGe / Au is provided on the upper and lower n-GaAs electrode layers 3 (3A), and the element surface (other than the electrode) is further provided with a SiN protective film or a SiON protective film (see FIG. (Not shown).
In this manner, a quantum dot infrared detector including 10 columnar quantum dot layers 2 is manufactured.

  In this case, the carrier supplying semiconductor layer 7 (n-GaAs layer) is formed before forming the carrier supplying quantum dot layer 6 and the columnar quantum dot layer 2 in the second and subsequent layers. However, it is not limited to this. For example, as shown in FIG. 2B, the carrier supply semiconductor layer (n-GaAs layer) is not formed, but the carrier supply is provided on the i-GaAs buried layer 5B constituting the uppermost layer of the columnar quantum dot layer 2. You may make it form the quantum dot layer 6, and the same effect | action and effect are acquired also in this case.

  Here, InAs and GaAs are used as materials for the upper and lower electrode layers 3 (contact layers), the quantum dots 4A, 5A, and 6A, the buried layers (intermediate layers) 4B, 5B, and 6B, and the semiconductor layer 7 for supplying carriers. Although used, it is not limited to this. The materials of the quantum dots 4A, 5A, 6A and the buried layers (intermediate layers) 4B, 5B, 6B include InAs, GaAs, AlAs, InP, GaP, AlP, InSb, GaSb, AlSb, InN, GaN, AlN, and these. A mixed crystal of may be used. For example, a material containing In (or Sb) may be used for the quantum dots 4A, 5A, and 6A.

  Furthermore, here, the conductivity types of the upper and lower electrode layers 3 (contact layers), quantum dots 4A, 5A, and 6A, buried layers (intermediate layers) 4B, 5B, and 6B, and the semiconductor layer for carrier supply 7 are n-type. However, the present invention is not limited to this, and the polarity of the conductivity type (p / n type) may be reversed to obtain the p type. That is, instead of the n-type impurities doped in the upper and lower electrode layers 3 (contact layers), quantum dots 4A, 5A, 6A, buried layers (intermediate layers) 4B, 5B, 6B, and the carrier supply semiconductor layer 7. These may be doped with a p-type impurity (for example, Be).

Here, the MBE method is used as the growth method. However, the growth method is not limited to this. For example, the MOCVD method may be used. That is, a growth method that can form self-assembled quantum dots may be used.
Therefore, according to the quantum dot photodetector and the manufacturing method thereof according to the present embodiment, the quantum efficiency can be improved, sufficient sensitivity can be obtained, and the performance can be improved. There is.

  That is, the carrier supply quantum dots 4A doped with impurities are formed directly on the electrode layer 3A on the carrier supply side, and the columnar quantum dots are aligned above the carrier supply quantum dots 4A in the stacking direction. By forming 2A, carrier supply efficiency can be improved. Thereby, the quantum efficiency of the quantum dot infrared detector can be improved, high sensitivity can be realized, and device performance can be improved.

  In the above-described embodiment, the carrier supply quantum dots 4A are entirely embedded by the embedded layer 4B, but the present invention is not limited to this. For example, as shown in FIG. 3, a barrier layer 4C made of a material that is in contact with the side surface of the carrier supply quantum dot 4A and has a wider band gap than the buried layer 4B (second buried layer) is provided. 4B may be formed on the barrier layer 4C to cover the upper part of the carrier supplying quantum dots 4A.

  In the above-described embodiment, only the carrier supply quantum dots 4A are doped with impurities, and the buried layers 4B, 5B, and 6B and the columnar quantum dots 2A are not doped with impurities, but this is not limitative. It is not a thing. For example, impurities may be doped in other portions. In this case, the carrier supply quantum dots 4A are made to have a larger doping amount than the other parts (buried layers and columnar quantum dots).

  Note that the present invention is not limited to the configurations described in the above-described embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Columnar quantum dot layer 3 Electrode layer 3A Electrode layer of carrier supply side 4 Quantum dot layer for carrier supply 4A Quantum dot for carrier supply 4B Embedded layer (second embedded layer)
4C barrier layer 5 quantum dot layer 5A quantum dot 5B embedded layer (first embedded layer)
6 Quantum dot layer for carrier supply 6A Quantum dot for carrier supply 6B Buried layer (third buried layer)
7 Semiconductor layer for carrier supply

Claims (6)

A plurality of quantum dot layers including a quantum dot and a first embedded layer that embeds the quantum dot, and the quantum dots included in each of the plurality of quantum dot layers are aligned in a stacking direction to form a columnar quantum dot. The columna quantum dot layer,
Two electrode layers sandwiching the columnar quantum dot layer;
A quantum dot for carrier supply provided between the columnar quantum dot layer and the electrode layer on the carrier supply side of the two electrode layers, in contact with the carrier supply side electrode layer and doped with impurities; A quantum dot photodetector comprising a carrier supplying quantum dot layer including a second embedded layer in which the carrier supplying quantum dots are embedded. Including a plurality of the columnar quantum dot layers,
Other carrier supply quantum comprising, between the plurality of columnar quantum dot layers, another carrier supply quantum dot doped with an impurity and a third embedded layer in which the other carrier supply quantum dot is embedded The quantum dot photodetector according to claim 1, further comprising a dot layer. A carrier supplying semiconductor layer doped with impurities between the plurality of columnar quantum dot layers,
3. The quantum dot photodetector according to claim 2, wherein the other carrier supply quantum dots are in contact with a side opposite to the carrier supply side electrode layer of the carrier supply semiconductor layer. An interlayer distance between the plurality of columnar quantum dot layers is 30 nm or more;
4. The quantum dot photodetector according to claim 2, wherein an interlayer distance between the plurality of quantum dot layers and the carrier supplying quantum dot layer is 10 nm or more and less than 30 nm. A barrier layer made of a material in contact with the side surface of the carrier supply quantum dot and having a wider band gap than the second buried layer;
5. The quantum dot type according to claim 1, wherein the second embedded layer is formed on the barrier layer and covers an upper portion of the carrier supplying quantum dots. 6. Photo detector. Forming quantum dots for carrier supply doped with impurities so as to be in contact with the surface of the electrode layer,
A columnar quantum dot layer including a columnar quantum dot is formed immediately above the carrier supply quantum dot,
An electrode layer is formed on the columnar quantum dot layer. A method for manufacturing a quantum dot photodetector.

Images