JP4040970B2 - Mid-infrared photon detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-sensitivity mid-infrared wavelength region photon detector capable of detecting a single photon. Mid-infrared light detection technology is expected to have a wide range of applications such as chemistry, biotechnology, environment, and infrared astronomy.
[0002]
[Prior art]
Conventionally, semiconductor devices for detecting mid-infrared light that have been widely used are mercury, cadmium, and tellurium-based photoconductive materials, and quantum well infrared detectors using longitudinal conduction due to intersubband transition in quantum wells. (Quantum Well Infrared Photodetector; QWIP). However, mercury, cadmium and tellurium-based photoconductive materials are material systems in which crystal growth and processes are very difficult, have strong toxicity, and have a drawback that the detector becomes very expensive.
[0003]
In addition, an infrared photodetector (QWIP) using intersubband transition in a quantum well is extremely revolutionary in that it enables infrared light in the 10 μm band with GaAs-based electronic materials. Device. However, there are disadvantages such as lack of sensitivity to vertically incident light on the sample surface due to selection rules, and high dark current due to scattering, which makes it difficult to operate at high temperature. Therefore, operation at 77K, which is important for practical use, was difficult. On the other hand, an infrared photodetector (Quantum Dot Infrared Photodetector; QDIP) using intersubband transition in a quantum dot in which electrons are confined three-dimensionally has recently been rapidly used as an effective means to solve the above problems. However, photodetectors using intersubband transitions in semiconductor quantum well structures have no sensitivity to normal incidence light and large dark current due to scattering-assisted tunneling effects There are problems such as that. On the other hand, vertical conduction photo detectors in which quantum wells in quantum well infrared photodetectors are replaced with indium arsenic self-assembled quantum dots have also been reported, but due to the irregular size and arrangement of quantum dots Highly sensitive light detection could not be performed due to the electron scattering effect.
[0004]
[Problems to be solved by the invention]
The ultimate sensitivity in light detection is to detect a single photon. In general, in a photoelectric conversion process, one photon excites one electron. The current generated by the photoexcited electrons is extremely small, so far, single photons have been detected by causing avalanche multiplication using an electron multiplier or an avalanche photodiode. However, in the mid-infrared wavelength range where the photon energy is small, it is not possible to find a material that causes an appropriate photoelectric conversion process and avalanche multiplication, and eventually single-photon detection in the mid-infrared wavelength region is possible. There was no such photon detector.
[0005]
The present invention
(1) A mid-infrared photon detector can be manufactured using standard semiconductor materials such as silicon and gallium arsenide whose manufacturing process has been established.
(2) Producing a photon detector having a structure that is easily arrayed;
(3) To realize a detector with higher sensitivity than the conventional mid-infrared photon detector,
Is an issue.
[0006]
[Means for Solving the Problems]
The mid-infrared photon detector of the present invention has a configuration in which a single electron transistor structure is stacked and capacitively coupled on the surface of a very fine semiconductor quantum well mesa structure in which charge transfer is caused by intersubband transition, The charge transfer of photoexcited carriers induced by photons incident on the quantum well structure can be detected with high sensitivity by a single electron transistor structure.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an element cross-sectional view of a mid-infrared photon detector according to an embodiment of the present invention.
[0008]
In FIG. 1, reference numeral 1 denotes a fine mesa structure including a quantum well in which electrons or holes undergo subband transition upon irradiation with mid-infrared light. For example, the diameter is about several hundred nm. Reference numeral 2 denotes a lower electrode in which electrons that have undergone subband transition in the mesa structure 1 relax. Reference numeral 3 denotes a metal electrode for making contact with the lower electrode 2. Reference numeral 4 denotes a quantum dot that detects a change in charge in the quantum well of the mesa structure 1. This quantum dot 4 is a quantum dot electrode of a single electron tunnel transistor laminated on the surface of the mesa structure 1. Reference numeral 5 denotes a tunnel barrier layer of a single electron tunnel transistor. Reference numeral 6 denotes a lead electrode of a single electron tunnel transistor, which conducts electrons between the quantum dot electrode 4 by a tunnel effect. Using this lead electrode 6, a signal by single photon absorption is taken out. In addition, by appropriately designing the shapes (patterns) of the metal electrode 3 and the lead electrode 6, the antenna effect with respect to the mid-infrared light is provided, and the mid-infrared light incident from above is applied to the quantum well portion of the mesa structure 1. It can condense efficiently and give sensitivity to normal incident light .
[0009]
FIG. 2 shows an energy band diagram in the portion of the quantum dot electrode 4 of FIG.
[0010]
In FIG. 2, the portion 1 that causes the transition between subbands can be fabricated using a quantum well such as gallium arsenide. Effects can be obtained. For the quantum dot electrode 4, a semiconductor or metal ultrafine structure is used.
[0011]
When the mid-infrared light is incident on one quantum well, electrons existing in the base subband in the quantum well transition to an upper subband by intersubband transition. Since the wave function of the upper subband has a large amplitude also in the lower electrode portion of 2, the electrons that have transitioned to the upper subband relax toward the lower electrode 2. Accordingly, when the mid-infrared light is incident, the charge moves from the inside of the quantum well to the lower electrode 2, and the charge in the quantum well is reduced.
[0012]
Single electron tunneling electrochemical potential of the quantum dot electrodes 4 of the transistors, since the coupling 1 of the quantum well and capacity, you change by a reduction in charge in the quantum well. In this case, for example, the voltage of the lower electrode 2, if it is biased to the state conductance high single-electron transistor, a change in the electrochemical potential of the quantum dot 4, conductance decreases. Incidence of mid-infrared light is detected as this change in conductance.
[0013]
The wavelength of light detection can be controlled by designing the quantum well structure, and light can be detected in a wide wavelength range from several μm to several tens of μm. It can also be fabricated on a wafer using standard semiconductor processes and can be arrayed.
[0014]
【The invention's effect】
The mid-infrared photon detector according to the present invention has a configuration in which charge transfer caused by intersubband transition in a quantum well is read out by a single electron tunnel transistor, so that the detection sensitivity is remarkably increased. This makes it possible to detect single photons in the mid-infrared light region where it is difficult to use the multiplication effect. The mid-infrared light detector according to the present invention can be expected to improve the sensitivity by several orders of magnitude as compared with the conventional mid-infrared photon detector operating in the mid-infrared light region.
[0015]
Further, since it can be manufactured using a conventional semiconductor process and is easily arrayed, it can be used for various purposes at a relatively low cost.
[Brief description of the drawings]
FIG. 1 is an element cross-sectional view of a mid-infrared photon detector according to an embodiment of the present invention.
FIG. 2 is an energy band diagram in the quantum dot electrode portion of the mid-infrared photon detector according to the present invention.
[Explanation of symbols]
1: Mesa structure including quantum well 2: Lower electrode 3: Metal electrode 4: Quantum dot / quantum dot electrode 5: Tunnel barrier layer 6: Lead electrode

Claims (3)

It is formed by laminating a single-electron transistor structure on the surface of a semiconductor quantum well mesa structure of very fine, such as charge transfer by intersubband transition occurs, the single electron transistor structure, the surface of the semiconductor quantum well mesa structure The charge transfer of photoexcited carriers induced by photons incident on a semiconductor quantum well mesa structure is detected by a single electron transistor structure in the mid-infrared wavelength region of claim 1 Photon detector. The photon detector in the mid-infrared wavelength region according to claim 1 , wherein the material of the semiconductor quantum well mesa structure is gallium arsenide. The photon detector in the mid-infrared wavelength region according to claim 1 , wherein the semiconductor quantum well mesa structure is replaced with indium arsenic self-assembled quantum dots.

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