JP2004214383A - Mid-infrared photon detector - Google Patents

Abstract

An object of the present invention is to realize a high-sensitivity photodetector capable of detecting a single photon in a wavelength region of a mid-infrared photon having a small energy, without depending on avalanche multiplication.
A mid-infrared photon detector according to the present invention has a structure in which a single electron transistor structure is stacked on a surface of a semiconductor quantum well structure in which charge transfer occurs due to an intersubband transition. A single electron transistor structure enables highly sensitive detection of charge transfer of photoexcited carriers induced by incident photons. It can be manufactured using a conventional semiconductor process having sensitivity to vertically incident light, and can be easily arrayed.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photon detector in the mid-infrared wavelength region with high sensitivity capable of detecting a single photon. Mid-infrared light detection technology is expected to be used in a wide range of applications such as chemistry, biotechnology, the environment, and infrared astronomy.
[0002]
[Prior art]
Conventionally, semiconductor devices for mid-infrared light detection, which have been widely used, include a mercury-cadmium-tellurium photoconductive material and a quantum well infrared photodetector using longitudinal conduction due to intersubband transition in the quantum well. (Quantum Well Infrared Photodetector; QWIP). However, the mercury / cadmium / tellurium-based photoconductive material is a material system in which crystal growth and its process are extremely difficult, has high toxicity, and has a disadvantage that the detector becomes very expensive.
[0003]
In addition, an infrared photodetector (Quantum Well Infrared Photodetector; QWIP) using transition between subbands in a quantum well is extremely breakthrough in that a 10 μm band infrared light is made possible with a GaAs-based electronic material. Device. However, there are drawbacks such as a lack of sensitivity to the vertically incident light on the sample surface due to the selection rule, a large dark current via scattering, and a difficulty in high-temperature operation. Therefore, it was difficult to operate at 77K, which is important for practical use. On the other hand, an infrared photodetector (Quantum Dot Infrared Photodetector; QDIP) using a transition between subbands in a quantum dot in which electrons are three-dimensionally confined has recently been used as an effective means for solving the above problem. Although rapidly gaining attention, photodetectors using intersubband transitions in semiconductor quantum well structures have no sensitivity to vertically incident light, and dark current due to scattering-assisted tunneling effects There is a problem such as being large. On the other hand, a vertical conduction photodetector in which the quantum well in the quantum well infrared photodetector is replaced with indium arsenide self-assembled quantum dots has been reported, but due to the irregular size and arrangement of the quantum dots. Highly sensitive light detection was not possible 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. Generally, in the photoelectric conversion process, one photon excites one electron. Since the current generated by the photoexcited electrons is extremely small, avalanche multiplication has been performed using an electron multiplier or an avalanche photodiode to detect single photons. However, in the wavelength range of the mid-infrared light where the photon energy is small, an appropriate photoelectric conversion process and a material that causes avalanche multiplication cannot be found, so that a single photon can be detected in the wavelength range of the mid-infrared light. There was no good photon detector.
[0005]
The present invention
(1) The mid-infrared photon detector can be manufactured using standard semiconductor materials, such as silicon and gallium arsenide, for which the manufacturing process is established.
(2) To make a photon detector sensitive to normal incident light so that it can be 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 an ultrafine semiconductor quantum well mesa structure in which charge transfer occurs due to an intersubband transition, A single electron transistor structure can detect charge transfer of photoexcited carriers induced by photons incident on the quantum well structure with high sensitivity.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view of an element of a mid-infrared photon detector according to one 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 sub-band transition by irradiation with mid-infrared light, and has a diameter of, for example, about several hundred nm. Reference numeral 2 denotes a lower electrode in which electrons having undergone subband transition in the mesa structure 1 are relaxed. Reference numeral 3 denotes a metal electrode for making contact with the lower electrode 2. Reference numeral 4 denotes a quantum dot for detecting a change in charge in the quantum well of the mesa structure 1. The quantum dots 4 serve as quantum dot electrodes of a single electron tunnel transistor stacked on the surface of the mesa structure 1. 5 is a tunnel barrier layer of the single electron tunnel transistor. Reference numeral 6 denotes a lead electrode of the single-electron tunnel transistor, which conducts electrons with the quantum dot electrode 4 by a tunnel effect. Using this lead electrode 6, a signal due to single photon absorption is taken out. By appropriately designing the shapes (patterns) of the metal electrode 3 and the lead electrode 6, an antenna effect for mid-infrared light is provided, and mid-infrared light incident from above is applied to the quantum well portion of the mesa structure 1. Light can be collected efficiently.
[0009]
FIG. 2 shows an energy band diagram of the quantum dot electrode 4 in FIG.
[0010]
In FIG. 2, the portion 1 causing the intersubband transition can be formed using a quantum well of, for example, gallium arsenide, but the same applies when an indium arsenide self-assembled quantum dot is used instead of the quantum well structure. Effects can be obtained. For the quantum dot electrode 4, an extremely fine structure of a semiconductor or metal is used.
[0011]
When the mid-infrared light is incident on one quantum well, electrons existing in the base subband in the quantum well transit to an upper subband by intersubband transition. Since the wave function of the upper sub-band also has a large amplitude at the lower electrode portion of 2, the electrons that have transitioned to the upper sub-band relax toward the lower electrode 2. Therefore, 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 decreases.
[0012]
Since the electrochemical potential of the quantum dot electrode 4 of the single electron tunnel transistor is capacitively coupled to one quantum well, the electrochemical potential changes due to the decrease in the charge in the quantum well. If the conductance of the single-electron transistor is biased to a high state, the conductance decreases due to a change in the electrochemical potential of the quantum dot 4. The incidence of mid-infrared light is detected as a 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 μm. Further, it can be manufactured on a wafer by using a standard semiconductor process, and can be formed into an array.
[0014]
【The invention's effect】
The mid-infrared photon detector according to the present invention has a configuration in which charge transfer due to intersubband transition in the quantum well is read out by a single-electron tunnel transistor, thereby significantly increasing the detection sensitivity. This enables single photon detection 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 have several orders of magnitude higher sensitivity than a conventional mid-infrared photon detector operating in the mid-infrared light region.
[0015]
In addition, since the semiconductor device can be manufactured using a conventional semiconductor process and can be easily formed into an array, the semiconductor device can be used for various purposes at a relatively low cost.
[Brief description of the drawings]
FIG. 1 is a sectional view of an element of a mid-infrared photon detector according to one embodiment of the present invention.
FIG. 2 is an energy band diagram at a 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 (5)

A photon detector in the mid-infrared wavelength region, wherein a single-electron transistor structure is stacked on the surface of a semiconductor quantum well structure in which charge transfer occurs due to intersubband transition. The single-electron transistor structure is capacitively coupled to the surface of the semiconductor quantum well structure, and the charge transfer of photoexcited carriers induced by photons incident on the semiconductor quantum well structure is detected by the single-electron transistor structure. The photon detector in the mid-infrared wavelength region according to claim 1. 3. The photon detector according to claim 1, wherein the semiconductor quantum well structure is a fine mesa structure. 4. The photon detector in the mid-infrared wavelength region according to claim 1, wherein a material of the semiconductor quantum well structure is gallium arsenide. 4. The photon detector in the mid-infrared wavelength region according to claim 3, wherein the semiconductor quantum well fine mesa structure is replaced by indium arsenide self-assembled quantum dots.

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