JP2012216714A - Terahertz detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terahertz detection device with low noise that uses a resonant tunnel diode.SOLUTION: A terahertz detection device comprises: a semiconductor substrate 1; second electrodes 2 and 2a that are disposed on the semiconductor substrate 1; an insulating layer 3 that is disposed on the second electrode 2; a first electrode 4 (4a, 4b, and 4c) that is disposed with respect to the second electrode 2 via the insulating layer 3 and is disposed so as to face the second electrode 2 on the semiconductor substrate 1; a MIM reflector 50 that is formed between the first electrode 4a and the second electrode 2 interposed the insulating layer 3 therebetween; a resonator 60 that is adjacent to the MIM reflector 50 and is disposed between the first electrode 4 and the second electrode 2 facing each other on the semiconductor substrate 1; an active element 90 that is disposed in the substantially center of the resonator 60; a waveguide 70 that is adjacent to the resonator 60 and is disposed between the first electrode 4 and the second electrode 2 facing each other on the semiconductor substrate 1; and a horn opening portion 80 that is adjacent to the waveguide 70 and is disposed between the first electrode 4 and the second electrode 2 facing each other on the semiconductor substrate 1.

Description

  The present invention relates to a terahertz detection element, and more particularly to a low noise terahertz detection element using a resonant tunneling diode.

  In recent years, electronic devices such as transistors have been miniaturized, and the size has become nano-sized. Therefore, a new phenomenon called a quantum effect has been observed. And development aiming at realization of ultra-high-speed devices and new functional devices using this quantum effect is in progress.

On the other hand, in such an environment, large-capacity communication, information processing, imaging, measurement, and the like are performed using a frequency range of 0.1 THz (10 ¹¹ Hz) to 10 THz, particularly called a terahertz band. An attempt is being made. This frequency region is an undeveloped region between light and radio waves. If a device that operates in this frequency band is realized, in addition to the above-mentioned imaging, large-capacity communication / information processing, physical properties, astronomy, living things, etc. It is expected to be used for many purposes such as measurement in various fields.

  As an element that oscillates a high-frequency electromagnetic wave having a frequency in the terahertz band, an element having a structure in which a fine slot antenna is integrated in an active device such as a transistor or a diode is known (for example, see Non-Patent Document 1).

  Further, an element having a structure in which a metal and an insulating layer are added on the slot lines at both ends of the antenna and short-circuited in a high frequency is disclosed (for example, see Non-Patent Document 1 and Non-Patent Document 2). This oscillation element is easy to manufacture and has features such as being suitable for miniaturization.

  FIG. 24 is a schematic bird's-eye view of an oscillation element manufactured by combining an RTD (Resonant Tunneling Diode) and a slot antenna. An active element 109 made of RTD is disposed near the center of the slot antenna 100, and a metal and insulator are laminated on both ends of the slot antenna 100, and the insulator is sandwiched between upper and lower electrode metals, and an MIM (Metal Insulator Metal) structure. Is formed. Here, the MIM structure includes the second electrode 104 / the insulating layer 103 / the first electrode 102, and is short-circuited in a high frequency manner.

  The second electrode 104 has two concave portions 105 and 106 formed in the central portion of the portion overlapping the first electrode 102 with the insulating layer 103 interposed between the two concave portions 105 and 106. In this state, the convex portion 107 is formed. A protrusion 108 is formed at a substantially central portion of the protrusion 107 of the second electrode 104, and an active element 109 is disposed below the protrusion 108 so as to be sandwiched between the first electrode 102. Yes. A DC power source 115 is connected to the second electrode 104 and the first electrode 102, and a parasitic oscillation suppression resistor 114 formed of a material such as bismuth (Bi) is connected to prevent parasitic oscillation. Has been.

  As a constituent material of the semiconductor substrate 101, semi-insulating (SI) InP is used. The slot antenna 100 made on both sides of the RTD serves as both a resonator and an electromagnetic wave radiation antenna. This oscillation element has a structure in which electromagnetic waves are radiated in two directions, upward and downward, with respect to the semiconductor substrate 101. For this reason, for example, as shown in FIG. 25, it is necessary to newly provide a silicon hemispherical lens 120 for condensing electromagnetic waves (hν) radiating vertically.

  In the conventional terahertz oscillation device shown in FIG. 24, an active element 109 such as a transistor or a diode disposed on the same plane as the insulating layer 103 is disposed at the center of the slot antenna 100, and both ends of the slot line are bent at right angles. This portion is covered with a metal / insulator / metal layer structure. For this reason, the portions covered with the metal / insulator / metal layer structure constitute the RF reflectors 150a and 150b, which are short-circuited in high frequency, and the slot antenna 100 is constructed. Since the slot antenna 100 is in an open state in terms of direct current, direct current can be supplied to the active element 109.

In FIG. 24 and FIG. 25, since the air above the slot antenna 100 is air, the relative permittivity ε _air = 1. Below the slot antenna 100, since an InP substrate is used as the semiconductor substrate 101, the relative dielectric constant ε _InP = 12.01. Here, the ratio of the oscillation output below the slot antenna 100 to the total oscillation output is represented by ε _InP ^3/2 / (ε _air ^3/2 + ε _InP ^3/2 ) = 0.97. That is, about 97% of the total oscillation output is radiated to the InP substrate side.

Oscillation with a terahertz band of 1.02 THz (10 ¹² Hz) is realized at room temperature by the oscillation element having this structure. That is, according to the prototyped element, the oscillation frequency of the fundamental wave was 342 GHz and the output was 23 μW. And it is reported that 1.02 THz electromagnetic waves were simultaneously output as the third harmonic of the fundamental wave, and the output of this third harmonic was 0.59 μW (see Non-Patent Document 3). Recently, fundamental wave oscillation of a terahertz band of 1.04 THz has been realized at room temperature (see Non-Patent Document 4).

  On the other hand, even in the case of electromagnetic waves in a frequency band with a relatively wide bandwidth that are oscillated from variable frequency oscillation elements, high efficiency and high output electromagnetic waves are oscillated without leakage from the slot line over the entire oscillation frequency. A terahertz oscillation element that can be used is also disclosed (for example, see Patent Document 1). In Patent Document 1, a multi-stage stub is provided at both ends of a fine slot antenna including an active device constituted by an RTD or the like, and a frequency band of an electromagnetic wave having a relatively wide bandwidth is reflected from the multi-stage stub, By providing this multi-stage stub circuit, leakage of electromagnetic waves oscillated from the active element is reflected and returned to the active element, so that a wide-band, high-power oscillation output can be obtained, and the active element used for the oscillation element has a variable frequency. In this case, an oscillation output can be obtained correspondingly.

  On the other hand, in the 300 GHz wireless communication system, there is one in which a 300 GHz electromagnetic wave is generated by a unit of about 20 cm square using a 16 GHz oscillator and a plurality of multipliers (for example, see Non-Patent Document 5). In addition, there is one in which an optical modulation technique is applied using two 1550 nm band semiconductor lasers (see, for example, Non-Patent Document 6).

  On the other hand, a Schottky Barrier Diode (SBD) is mainly developed as a terahertz detection element.

JP 2007-124250 A

N. Orihashi, S. Hattori, and M. Asada: “Millimeter and Submillimeter Oscillators Using Resonant Tunneling Diode and Slot Antenna with Stacked-Layer Slot Antenna,” Jpn.J.Appl.Phys. Vol.67, L1309 (2004). N. Orihashi, S. Hattori, and M. Asada: “Millimeter and Submillimeter Oscillator Using Resonant Tunneling Diode and Slot Antenna with a novel RF short structure,” Int. Conf. Infrared and Millimeter Waves (IRMMW2004), International Conference on Waves) Karlsruhe (Germany), M5.3 (Sept. 2004) pp.121-122. N. Orihashi, S. Suzuki, and M. Asada: “Harmonic Generation of 1THz in Sub-THz Oscillating Resonant Tunneling Diode,” [IRMMW2005 / THz2005 (The Joint 30th International Conference on Infrared and Millimeter Waves and 13th Infrared Conference on Terahertz Electronics) 2005.9.19-23] S. Suzuki, A. Teranishi, M. Asada, H. Sugiyama, and H. Yokoyama, “Increase of fundamental oscillation frequency in resonant tunneling diode with thin barrier and grated emitter structures,” Int. Conf. Infrared, Millimeter, and Teraherz waves, Tu-C1.2, Rome, Sept. 7, 2010 C. Jastrow, S. Priebe, B. Spitschan, J. Hartmann, M. Jacob, T. Kurner, T. Schrader, and T. Kleine-Ostmann, “Wireless digital data transmission at 300GHz,” Elecron. Lett., Vol 46, pp.661-663, 2010. T. Nagatsuma, H.- J. Song, Y. Fujimoto, K. Miyake, A. Hirata, K. Ajito, A. Wakatuski, T. Furuta, N. Kukutsu, and Y. Kado, “Giga-bit wireless link using 300-400 GHz bands, ”Tech. Dig. IEEE International Topical Meeting on Microwave Photonics, Th.2.3, 2009

  In SBD, the number of electrons that flow beyond the Schottky barrier increases with temperature, and as the temperature increases, there is a problem that thermal noise increases and the S / N ratio decreases.

  An object of the present invention is to provide a low noise terahertz detecting element using a resonant tunneling diode.

  According to one aspect of the present invention for achieving the above object, a semiconductor substrate, a second electrode disposed on the semiconductor substrate, an insulating layer disposed on the second electrode, and the first A first electrode disposed on the semiconductor substrate so as to face the first electrode, and the first electrode sandwiching the insulating layer; An MIM reflector formed between the second electrodes; a resonator disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the MIM reflector; and An active element disposed at a substantially central portion of the resonator, a waveguide disposed between the first electrode and the second electrode facing the semiconductor substrate, adjacent to the resonator; Adjacent to the waveguide, the first electrode facing the semiconductor substrate and the front THz detection device is provided and a horn opening portion disposed between the second electrode.

  According to another aspect of the present invention, an insulator substrate, a first electrode disposed on the insulator substrate, an insulating layer disposed on the first electrode, and the insulator substrate An interlayer insulating film disposed; and a second electrode disposed on the interlayer insulating film and disposed opposite to the first electrode through the insulating layer with respect to the first electrode; A semiconductor layer disposed on the second electrode; an MIM reflector formed between the first electrode and the second electrode across the insulating layer; and the insulator adjacent to the MIM reflector A resonator disposed between the first electrode and the second electrode opposed to each other on a substrate; an active element disposed at a substantially central portion of the resonator; and the insulation adjacent to the resonator. A waveguide disposed between the first electrode and the second electrode facing each other on a body substrate; Adjacent to the road, the said faces on an insulating substrate a first electrode and the terahertz detector element and a said horn opening disposed between the second electrode.

  According to another aspect of the present invention, an insulator substrate, a first electrode disposed on the insulator substrate, an insulating layer disposed on the first electrode, and the insulator substrate An interlayer insulating film disposed; and a second electrode disposed on the interlayer insulating film and disposed opposite to the first electrode through the insulating layer with respect to the first electrode; A semiconductor layer disposed on the second electrode; and disposed adjacent to the first electrode on the insulator substrate and opposite the first electrode on the opposite side of the second electrode. A first slot line electrode formed on the insulating substrate, adjacent to the second electrode, and on the opposite side of the first electrode to face the second electrode. A line electrode; and an MIM reflector formed between the first electrode and the second electrode across the insulating layer; A resonator disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the MIM reflector; and an active element disposed at a substantially central portion of the resonator; A first waveguide disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the resonator; and adjacent to the first waveguide; A first horn opening disposed between the first electrode and the second electrode facing each other on the insulator substrate; and the first electrode and the first slot line electrode facing each other on the insulator substrate. And a second horn opening disposed between the first electrode and the first slot line electrode facing the insulator substrate, adjacent to the second waveguide. , The second electrode and the second slot line facing each other on the insulator substrate A third waveguide disposed between the electrodes, and a third horn disposed between the second electrode and the second slot line electrode adjacent to the third waveguide and opposed to the insulator substrate. A terahertz detection element comprising an opening is provided.

  According to the present invention, it is possible to provide a low noise terahertz detecting element using a resonant tunneling diode.

The typical bird's-eye view of the terahertz detection element concerning an embodiment. FIG. 2A is a schematic cross-sectional structure diagram taken along the line II of FIG. 1, and FIG. 2B is a schematic cross-sectional structure diagram taken along the line II-II of FIG. FIG. 4A is a schematic cross-sectional structure diagram of a terahertz detection element (RTD) according to an embodiment, and FIG. 3B is a schematic cross-sectional structure diagram of a modified example of FIG. The typical cross-section figure of the terahertz detection element (RTD) which concerns on embodiment integrated with the terahertz oscillation element. (A) The typical circuit block diagram of the terahertz detection element which concerns on embodiment, (b) The simple equivalent circuit block diagram of the terahertz detection element. (A) Typical equivalent circuit block diagram also including the antenna system of the terahertz detection element which concerns on embodiment, (b) The equivalent circuit block diagram of RTD of Fig.5 (a). The current-voltage characteristic example of the terahertz detection element which concerns on embodiment. The figure which shows the relationship between the oscillation frequency f which uses the resonator length L1 as a parameter, and the peak current Ip in the terahertz oscillation element produced by the same process as the terahertz detection element which concerns on embodiment. The figure which shows the relationship between an oscillation intensity | strength and the oscillation frequency f in the terahertz oscillation element produced at the same process as the terahertz detection element which concerns on embodiment. The schematic diagram of the current-voltage characteristic of the Schottky barrier diode which concerns on the comparative example applicable as a terahertz detection element. The schematic diagram of the current-voltage characteristic of the terahertz detection element (RTD) which concerns on embodiment. FIG. 6 is a current-voltage characteristic example of the terahertz detection element (RTD) according to the embodiment, and is a characteristic example when operating at room temperature, when irradiating a terahertz wave (A), and when not irradiating a terahertz wave (B). The typical block block diagram of the terahertz radio communication system which applies the terahertz detection element (RTD) which concerns on embodiment as a detection element. The block diagram of the terahertz radio | wireless communication system using the terahertz oscillation element (RTD) of the same structure as the terahertz detection element (RTD) which concerns on embodiment. The typical bird's-eye view of the terahertz detection element (RTD) which concerns on the modification 1 of embodiment. The typical bird's-eye view of the terahertz detection element (RTD) which concerns on the modification 2 of embodiment. FIG. 17 is a schematic plan view of a pattern structure of a first electrode 4, a second electrode 2a, and a semiconductor layer 91a corresponding to FIG. (A) The typical cross-section figure along the III-III line of FIG. 16, (b) The typical cross-section figure along the IV-IV line of FIG. The typical bird's-eye view which shows a mode that the insulator board | substrate was affixed on the sample surface in the terahertz detection element which concerns on the modification 2, and the semiconductor substrate was removed. The typical bird's-eye view which shows a mode seen from the back surface of FIG. (A) The schematic plan view of the electrode pattern structure of the terahertz detection element which concerns on the modification 3 of embodiment, (b) The typical top view of the electrode pattern structure of the terahertz detection element which concerns on the modification 4 of embodiment. FIG. 10 is a schematic plan view of a terahertz detection element according to Modification 5 of the embodiment. The typical top view of the terahertz detection element which concerns on the modification 6 of embodiment. The typical bird's-eye view which shows the structure of the conventional terahertz oscillation element. The typical bird's-eye view which shows the structure of the conventional terahertz oscillation element arrange | positioned on a silicon hemisphere lens.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following, the same reference numerals are assigned to the same blocks or elements to avoid duplication of explanation and simplify the explanation. It should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention. In the embodiments of the present invention, the arrangement of each component is as follows. Not specific. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

[Embodiment]
A schematic bird's-eye view structure of the terahertz detection element according to the embodiment is represented as shown in FIG. 1, and a schematic cross-sectional structure taken along line II in FIG. 1 is represented as shown in FIG. A schematic cross-sectional structure taken along line II-II in FIG. 1 is expressed as shown in FIG.

  The schematic bird's-eye view structure of the terahertz detection element according to the embodiment includes, as shown in FIGS. 1 to 2, a semiconductor substrate 1, second electrodes 2 and 2 a disposed on the semiconductor substrate 1, An insulating layer 3 disposed on the electrode 2 and a first electrode disposed on the semiconductor substrate 1 so as to face the second electrode 2 with respect to the second electrode 2 via the insulating layer 3. The electrode 4 (4a, 4b, 4c), the MIM reflector 50 formed between the first electrode 4a and the second electrode 2 with the insulating layer 3 interposed therebetween, and adjacent to the MIM reflector 50 on the semiconductor substrate 1 The resonator 60 disposed between the first electrode 4 and the second electrode 2 facing each other, the active element 90 disposed substantially at the center of the resonator 60, and the semiconductor substrate 1 adjacent to the resonator 60. A waveguide 70 disposed between the first electrode 4 and the second electrode 2 facing upward, and adjacent to the waveguide 70 To, and a first electrode 4 and the horn opening 80 disposed between the two second electrodes facing on the semiconductor substrate 1.

  The active element 90 is typically an RTD, but can be composed of other diodes or transistors. Other active elements include, for example, a tannet (TUNNETT) diode, an impulse (Impact Ionization Avalanche Transit Time) diode, a GaAs field effect transistor (FET), a GaN FET, a high An electron mobility transistor (HEMT), a heterojunction bipolar transistor (HBT), or the like can also be applied.

  The horn opening 80 is composed of an open horn antenna. The opening angle θ of the horn opening is desirably set to about 10 degrees or less, for example, in order to provide directivity in the electromagnetic wave (hν) detection direction. The length L3 of the horn opening 80 is, for example, about 700 μm or less. The opening width at the tip of the horn opening 80 is, for example, about 160 μm.

  The waveguide 70 is disposed in the opening of the resonator 60. The length L2 of the waveguide 70 is, for example, about 700 μm or less. In addition, the distance between the first electrode 4 and the second electrode 2 in the waveguide 70 is, for example, about 24 μm.

  Note that the horn shape of the horn opening 80 is a structure necessary for effectively detecting electromagnetic waves from the air. Due to the horn shape, electromagnetic waves can be efficiently detected from the air with good impedance matching. The shape of the horn is not limited to a linear shape, but may be a non-linear shape, a curved shape, a quadratic curved shape, a parabolic shape, a stepped shape, or the like.

  In the resonator 60, two concave portions 5 and 6 are formed, and a convex portion 7 is formed between the two concave portions 5 and 6. Then, a protrusion 8 is formed at a substantially central portion of the protrusion 7 of the first electrode 4, and an active element 90 is disposed below the protrusion 8 so as to be sandwiched between the second electrode 2. .

The length L1 of the resonator 60 is, for example, about 30 μm or less. The length of the protrusion 8 is, for example, about 6 μm or less. Further, the width of the recesses 5 and 6 (the distance between the first electrode 4 and the second electrode 2) is, for example, about 4 μm. The dimension of the active element 90 is, for example, about 1.4 μm ² . However, the size of the active element 90 is not limited to this value, and may be, for example, about 5.3 μm ² or less. The detailed structure of the active element 90 will be described later. The size of each part of the resonator 60 is not limited to the above dimensions, and is appropriately set in design according to the frequency of the terahertz electromagnetic wave to be received.

  Further, as shown in FIG. 1, compared with the distance between the first electrode 4 and the second electrode 2 in the waveguide 70, the first electrode 4 and the second electrode in the portion where the resonator 60 is formed. The interval between the electrodes 2 is narrow.

  The MIM reflector 50 is disposed at the closing portion on the opposite side of the opening of the resonator 60. Due to the laminated structure of the metal / insulator / metal MIM reflector 50, the first electrode 4 and the second electrode 2 are short-circuited in high frequency. Further, the MIM reflector 50 has an effect that it can reflect a high frequency while being open in terms of direct current.

  Each of the first electrode 4 (4a, 4b, 4c) and the second electrode 2, 2a has, for example, a metal laminated structure of Au / Pd / Ti, and the Ti layer is a semi-insulating InP substrate described later. It is a buffer layer for making the contact state with the semiconductor substrate 1 which consists of favorable. The thickness of each part of the first electrodes 4a, 4b, 4c and the second electrodes 2, 2a is, for example, about several hundred nm, and as shown in FIGS. 2 (a) and 2 (b) as a whole. A flattened laminated structure is obtained. Note that both the first electrode 4 and the second electrode 2 can be formed by a vacuum evaporation method, a sputtering method, or the like.

  More specifically, the first electrode 4a and the first electrode 4c are made of, for example, Au / Pd / Ti, and the first electrode 4b is made of, for example, Au / Ti. The second electrode 2 is made of, for example, Au / Pd / Ti, and the second electrode 2a is made of, for example, Au / Ti.

  Note that the Ti layer forming the surface layer of the first electrode 4b is desirably removed in order to reduce the contact resistance when the extraction electrode is formed by a bonding wire (not shown). Similarly, the Ti layer forming the surface layer of the second electrode 2a is desirably removed in order to reduce the contact resistance when forming the extraction electrode with a bonding wire (not shown).

The insulating layer 3 can be formed of, for example, a SiO ₂ film. In addition, a Si ₃ N ₄ film, a SiON film, a HfO ₂ film, an Al ₂ O ₃ film, or the like can be applied. The thickness of the insulating layer 3 can be determined in consideration of the geometric plane size of the MIM reflector 50 and the required capacitor value in terms of circuit characteristics, and is, for example, about several tens nm to several hundreds nm. . The insulating layer 3 can be formed by a chemical vapor deposition (CVD) method, a sputtering method, or the like.

―Resonant tunnel diode―
A schematic cross-sectional structure of a resonant tunneling diode (RTD) applicable to the terahertz detection element according to the embodiment is represented as shown in FIG. 3A, and a schematic cross-sectional structure of the modified example is shown in FIG. It is expressed as shown in b).

  As shown in FIG. 3A, a configuration example of an RTD as an active element 90 applicable to the terahertz detection element according to the embodiment is arranged on a semiconductor substrate 1 made of a semi-insulating InP substrate, and is n-type. GaInAs layer 91a doped with impurities at a high concentration, GaInAs layer 92a doped with n-type impurities, GaInAs layer 92b disposed on GaInAs layer 92a, and GaInAs layer disposed on GaInAs layer 91a An RTD portion composed of an AlAs layer 94a / GaInAs layer 95 / AlAs layer 94b disposed on 93b, an undoped GaInAs layer 93b disposed on the AlAs layer 94b, and an n-type layer disposed on the GaInAs layer 93a An impurity-doped GaInAs layer 92b and an n-type impurity disposed on the GaInAs layer 92b A GaInAs layer 91b doped with a material at a high concentration, a first electrode 4a disposed on the GaInAs layer 91b, and a second electrode 2 disposed on the GaInAs layer 91a are provided.

  In the modification, as shown in FIG. 3B, a GaInAs layer 91c doped with a high concentration of n-type impurities is further disposed on a GaInAs layer 91b doped with a high concentration of n-type impurities, and the first The contact with the electrode 4a is made good.

As shown in FIGS. 3A and 3B, the RTD portion is formed by sandwiching a GaInAs layer 95 between AlAs layers 94a and 94b. The RTD portion laminated in this way is interposed with n-type GaInAs layers 92a and 92b and n ⁺ -type GaInAs layers 91a, 91b or 91c with undoped GaInAs layers 93a and 93b used as spacers interposed therebetween. The second electrode 2 and the first electrode 4 are ohmicly connected.

  Here, the thickness of each layer is as follows, for example.

The thicknesses of the n ⁺ -type GaInAs layers 91a, 91b, and 91c are, for example, about 400 nm, 15 nm, and 8 nm, respectively. The thicknesses of the n-type GaInAs layers 92a and 92b are substantially equal, for example, about 25 nm. The undoped GaInAs layers 93a and 93b have a thickness of about 2 nm and 20 nm, for example. The thicknesses of the AlAs layers 94a and 94b are equal, for example, about 1.1 nm. The thickness of the GaInAs layer 95 is about 4.5 nm, for example.

Note that, on the side wall portion of the stacked structure shown in FIGS. 3A and 3B, the SiO ₂ film, the Si ₃ N ₄ film, the SiON film, the HfO ₂ film, the Al ₂ O ₃ film, etc., or these An insulating film made of a multilayer film can also be deposited. The insulating layer can be formed by a CVD method, a sputtering method, or the like.

  The terahertz detection element according to the embodiment can be formed in the same manufacturing process as the terahertz oscillation element. Here, a schematic cross-sectional structure of the terahertz detection element RTD (D) according to the embodiment integrated with the terahertz oscillation element RTD (O) manufactured in the same process is expressed as shown in FIG. Since the configuration of each layer is the same as that in FIG.

For example, in a terahertz oscillation device manufactured in the same process, the oscillation frequency observed at room temperature is about 300 GHz. Further, for example, the current density Jp of the terahertz oscillation element at the time of oscillation is about 7 mA / μm ² .

  In the terahertz detection element according to the embodiment, the AlAs layers 94a and 94b serving as barrier layers are formed thicker than the terahertz oscillation element, and the current density Jp of the terahertz detection element during detection is set low. Thus, noise reduction may be achieved. Similarly, in the terahertz detection element according to the embodiment, the doping level of the n-type GaInAs layers 92a and 92b is formed lower than that of the terahertz oscillation element, and the current density Jp of the terahertz detection element at the time of detection is set low. Thus, noise reduction may be achieved. In the case of an oscillation element, it is desirable that the RTD current density is large. However, when used as a detection element, oscillation may cause noise, so the RTD current density is desirably relatively low. For this reason, when there is a possibility that the oscillation becomes noise, a structure for reducing the noise may be provided by deliberately reducing the current density.

  In the terahertz detection element according to the present embodiment, bismuth (Bi) wiring for suppressing parasitic oscillation is also unnecessary.

―Circuit configuration―
A schematic circuit configuration of the terahertz detection element according to the embodiment is represented by a parallel circuit of a diode that configures the active element 90 and a capacitor CM that configures the MIM reflector 50, as illustrated in FIG. A diode anode is connected to the first electrode 4, a diode cathode is connected to the second electrode 2, a negative voltage is applied to the first electrode 4, and a positive voltage is applied to the second electrode 2. Is applied. In the detection state, the electromagnetic wave (hν) from the Y-axis direction, which is the opening direction of the horn opening, is detected with good directivity.

  In the simple equivalent circuit configuration corresponding to FIG. 5A, as shown in FIG. 5B, the RTD constituting the active element 90 can be represented by a parallel circuit of a capacitor C01 and an inductor L01, and the MIM reflector 50 Are further connected in parallel.

A schematic equivalent circuit configuration including the antenna system of the terahertz detection element according to the embodiment is as shown in FIG. 6A with respect to a parallel circuit of an active element 90 and a capacitor CM representing a diode (RTD) system. A parallel circuit of an antenna inductor L representing an antenna (ANT) system, an antenna capacitor CA, and an antenna radiation resistance _GANT is connected in parallel.

  As shown in FIG. 6 (b), the equivalent circuit configuration of the diode constituting the active element 90 of FIG. 6 (a) is as follows. A parallel circuit of a diode part composed of an internal diode capacitor Cd and a diode negative resistance (-Gd) and a series circuit of a mesa part composed of an inductor LM and a resistor RM are connected in series.

Here, the admittance Y of the entire equivalent circuit is
Y = Yd + Yc.Ya.Ym / (Yc.Ya + Ya.Ym + Yc.Ym)
It is represented by Here, Yd = −Gd + jωCd, Yc = 1 / Rc + jωCc, Ym = 1 / (Rm + jωLm), Ya represents the admittance of the antenna system, and ω represents the oscillation angular frequency. Each parameter can be obtained from a physical property value of a diode (RTD) constituting the active element 90.

  An example of the current-voltage characteristic of the terahertz detection element according to the embodiment is expressed as shown in FIG. 7, and the value of the peak current Ip is about 12 mA at about 0.75 V. Further, negative differential resistance (NDR) is obtained in the range of 0.7V to 1.0V. The peak-to-valley ratio is about 3.

  In the terahertz oscillation element manufactured in the same process as the terahertz detection element according to the embodiment, the relationship between the oscillation frequency f using the resonator length L1 as a parameter and the peak current Ip is expressed as shown in FIG. With the resonator length L1 = 80 μm, an oscillation frequency f of about 250 to 300 GHz, with L1 = 60 μm, about 300 to 320 GHz, with L1 = 40 μm, about 350 to 370 GHz, and with L1 = 20 μm, an oscillation frequency f of about 380 to 400 GHz is obtained. Yes. The value of the peak current Ip is about 4 to 10 mA. As the resonator length L1 becomes shorter, the oscillation frequency f tends to increase.

  In the terahertz oscillation element manufactured in the same process as the terahertz detection element according to the embodiment, the relationship between the oscillation intensity and the oscillation frequency f is expressed as shown in FIG. An oscillation frequency f of about 300 GHz is obtained at room temperature. The value of the oscillation frequency f can be changed by adjusting the structure of each layer, the size of the mesa region, the antenna structure, and the like shown in FIG.

  A current-voltage characteristic of a Schottky Barrier Diode (SBD) according to a comparative example applicable as a terahertz detection element is schematically represented as shown in FIG.

  On the other hand, the current-voltage characteristic of the terahertz detection element (RTD) according to the embodiment is schematically represented as shown in FIG. Since the terahertz detection element (RTD) according to the embodiment has a negative resistance, there is a region with higher nonlinearity than SBD, and sensitivity is high.

  In SBD, the number of electrons that flow beyond the Schottky barrier increases with temperature, so as the temperature increases, thermal noise increases and the S / N ratio decreases. On the other hand, in the terahertz detection element (RTD) according to the embodiment, the electrons contributing to the tunnel current are electrons lower than the Fermi energy level. For this reason, the temperature dependence of the tunnel current is small. Therefore, in the terahertz detection element (RTD) according to the embodiment, the nonlinearity is large before and after the negative resistance, so that the S / N ratio is improved.

  As shown in FIG. 11, the operating point Q on the current-voltage characteristic is in the oscillation state because it is in the NDR region. Therefore, in the terahertz detection element according to the embodiment, the operating point on the current-voltage characteristic needs to be in a non-oscillating state. On the other hand, in order to increase the detection sensitivity in the terahertz detection element according to the embodiment, it is desirable to set the operating point on the current-voltage characteristic to the non-oscillation state and maximize the rate of change of the differential resistance. Such an operating point corresponds to the operating point P and the operating point Q on the current-voltage characteristics of the terahertz detecting element according to the embodiment. That is, the operating point P and the operating point R on the current-voltage characteristic are in a non-oscillating state, and the detection sensitivity has a maximum value.

  FIG. 6 is an example of current-voltage characteristics of the terahertz detection element (RTD) according to the embodiment, and the characteristics change between the time of irradiation with the terahertz wave (A) and the time of non-irradiation of the terahertz wave in the room temperature operation is illustrated in FIG. As shown in FIG. As shown in FIG. 12, by setting the bias voltage to 0.5 V, for example, terahertz electromagnetic waves can be detected with good sensitivity and at room temperature operation.

  A schematic block configuration of a terahertz wireless communication system in which the terahertz detection element (RTD) according to the embodiment is applied as a detection element includes a terahertz transmitter 100 including a terahertz oscillation element 38 and a terahertz detection as illustrated in FIG. A terahertz receiver 200 including an element 44. Here, the terahertz detection element (RTD) according to the embodiment can be applied to the terahertz detection element 44. Here, the terahertz oscillation element 38 has an operating point in a negative differential resistance region (NDR), for example, and generates a terahertz electromagnetic wave, and the terahertz detection element 44 receives the terahertz electromagnetic wave generated from the terahertz oscillation element 38. To detect.

  The configuration of the terahertz wireless communication system using the terahertz oscillation element (RTD) having the same configuration as the terahertz detection element (RTD) according to the embodiment is expressed as shown in FIG. In FIG. 14, a terahertz oscillation element (RTD) having the same configuration as that of the terahertz detection element (RTD) according to the embodiment shown in FIG. 1 is used. For this reason, by combining with the terahertz oscillation device manufactured in the same process, the transmitter and the detector are drastically reduced, and a radio transmission / reception system of terahertz electromagnetic waves can be provided with high sensitivity and low noise.

-Modification 1-
A schematic bird's-eye view structure of the terahertz detection element according to the first modification according to the embodiment is expressed as shown in FIG.

  In Modification 1, as shown in FIG. 15, the semiconductor substrate 1 is a region where the first electrode 4 and the second electrode 2 that form the resonator 60, the waveguide 70, and the horn opening 80 are disposed. In FIG. Further, as shown in FIG. 15, the waveguide 70 between the first electrode 4 and the second electrode 2 and the semiconductor substrate 1a of the horn opening 80 may be completely removed. Since other configurations are the same as the configuration in FIG. 1, description of each part is omitted.

  In FIG. 15, the thickness of the thinned semiconductor substrate 1a is, for example, about 20 μm. The length of the waveguide 70 is, for example, about 700 μm or less, and the length of the horn opening 80 is, for example, about 700 μm or less. The total length of the terahertz detection element according to the first modification including the MIM reflector 50 is, for example, about 1600 μm or less.

  According to the electromagnetic field simulation result when the terahertz detection element according to the first modification is operated as a terahertz oscillation element, the Y axis is extended along the electrode pattern extending in the Y axis direction on the thinned semiconductor substrate 1a. Electric field patterns are generated at regular intervals in the direction, and there is almost no electric field leakage in the direction perpendicular to the semiconductor substrate 1a (−Z axis direction). Further, according to the three-dimensional electromagnetic field simulation result in the XYZ-axis directions, the directivity in the Y-axis direction is remarkably improved. Further, from the relationship between the Y-axis direction radiation intensity and the oscillation frequency, the harmonic component is suppressed, and the directivity is improved. As a technique for forming the thinned semiconductor substrate 1a, a technique for forming a MEMS (Micro Electro Mechanical Systems) element can be applied.

  According to the terahertz detection element according to the first modification, by reducing the thickness of the semiconductor substrate, it is possible to suppress the influence of the substrate, improve directivity, and highly efficiently in a lateral direction with respect to the substrate. Radio waves can be detected and integration is easy.

  According to the terahertz detection element according to the first modification, the influence of the substrate can be suppressed by thinning the semiconductor substrate, the directivity is improved in the direction horizontal to the substrate, and the terahertz electromagnetic wave is efficiently generated. Can be detected.

-Modification 2-
A schematic bird's-eye view structure of the terahertz detection element according to the second modification of the embodiment is expressed as shown in FIG. 16, and the first electrode 4, the second electrode 2a, and the semiconductor layer 91a corresponding to FIG. A schematic plan view of the pattern structure is expressed as shown in FIG. Further, a schematic cross-sectional structure taken along line III-III in FIG. 16 is represented as shown in FIG. 18A, and a schematic cross-sectional structure taken along line IV-IV in FIG. 16 is shown in FIG. Represented as shown.

  As shown in FIGS. 16 to 18, the terahertz detection element according to Modification 2 includes an insulator substrate 10, a first electrode 4 (4 a, 4 b, 4 c) disposed on the insulator substrate 10, An insulating layer 3 disposed on one electrode 4a, an interlayer insulating film 9 disposed on an insulator substrate 10, and an insulating layer 3 disposed on the interlayer insulating film 9 and with respect to the first electrode 4a. A second electrode 2, 2 a disposed opposite to the first electrode 4 via the semiconductor layer 91, a semiconductor layer 91 a disposed on the second electrode 2, and the first electrode 4 a sandwiching the insulating layer 3 The MIM reflector 50 formed between the second electrodes 2, and the resonator 60 disposed between the first electrode 4 and the second electrode 2 facing the insulator substrate 10 adjacent to the MIM reflector 50. An active element 90 disposed substantially at the center of the resonator 60, and an insulator substrate adjacent to the resonator 60. The waveguide 70 disposed between the first electrode 4 and the second electrode 2 facing each other on the substrate 10, and the first electrode 4 and the second electrode facing each other on the insulator substrate 10 adjacent to the waveguide 70. A horn opening 80 disposed between the two electrodes 2.

  The horn opening 80 is composed of an open horn antenna. The opening angle θ of the horn opening is preferably set to about 10 degrees or less, for example, in order to provide directivity in the terahertz electromagnetic wave (hν) detection direction. The length L3 of the horn opening 80 is, for example, about 700 μm or less. The opening width at the tip of the horn opening 80 is, for example, about 160 μm.

  The waveguide 70 is disposed in the opening of the resonator 60. The length L2 of the waveguide 70 is, for example, about 700 μm or less. In addition, the distance between the first electrode 4 and the second electrode 2 in the waveguide 70 is, for example, about 24 μm.

  Note that the horn shape of the horn opening 80 is a structure necessary for effectively detecting terahertz electromagnetic waves from the air. By the horn shape, terahertz electromagnetic waves can be efficiently detected from the air with good impedance matching. The shape of the horn is not limited to a linear shape, but may be a non-linear shape, a curved shape, a quadratic curved shape, a parabolic shape, a stepped shape, or the like.

  In the resonator 60, two concave portions 5 and 6 are formed, and a convex portion 7 is formed between the two concave portions 5 and 6. A protrusion 8 is formed at a substantially central portion of the protrusion 7 of the semiconductor layer 91a, and an active element 90 is disposed below the protrusion 8 so as to be sandwiched between the first electrode 4a.

The length L1 of the resonator 60 is, for example, about 30 μm or less. The length of the protrusion 8 is, for example, about 6 μm or less. Further, the width of the recesses 5 and 6 (the distance between the first electrode 4 and the second electrode 2) is, for example, about 4 μm. The dimension of the active element 90 is, for example, about 1.4 μm ² . However, the size of the active element 90 is not limited to this value, and may be, for example, about 5.3 μm ² or less. The size of each part of the resonator 60 is not limited to the above dimensions, and is appropriately set in design according to the frequency of the terahertz electromagnetic wave to be received.

  In addition, as shown in FIG. 16, compared with the distance between the first electrode 4 and the second electrode 2 in the waveguide 70, the first electrode 4 and the second electrode in the portion where the resonator 60 is formed. The interval between the electrodes 2 is narrow.

  The MIM reflector 50 is disposed at the closing portion on the opposite side of the opening of the resonator 60. Due to the laminated structure of the metal / insulator / metal MIM reflector 50, the first electrode 4 and the second electrode 2 are short-circuited in high frequency. Further, the MIM reflector 50 has an effect that it can reflect a high frequency while being open in terms of direct current.

  Each of the first electrode 4 (4a, 4b, 4c) and the second electrode 2, 2a has, for example, an Au / Pd / Ti metal laminated structure, and the Ti layer is in contact with the insulator substrate 10. This is a buffer layer for improving the resistance. The thickness of each part of the first electrodes 4a, 4b, 4c and the second electrodes 2, 2a is, for example, about several hundred nm, and as a whole, as shown in FIGS. 18 (a) and 18 (b). A flattened laminated structure is obtained. Note that both the first electrode 4 and the second electrode 2 can be formed by a vacuum evaporation method, a sputtering method, or the like.

  More specifically, the first electrode 4a and the first electrode 4c are made of, for example, Au / Pd / Ti, and the first electrode 4b is made of, for example, Au / Ti. The second electrode 2 is made of, for example, Au / Pd / Ti, and the second electrode 2a is made of, for example, Au / Ti.

  Note that the Ti layer forming the surface layer of the first electrode 4b is desirably removed in order to reduce the contact resistance when the extraction electrode is formed by the bonding wire 12b. Similarly, the Ti layer forming the surface layer of the second electrode 2a is desirably removed in order to reduce the contact resistance when the extraction electrode is formed by the bonding wire 12a.

The insulating layer 3 can be formed of, for example, a SiO ₂ film. In addition, a Si ₃ N ₄ film, a SiON film, a HfO ₂ film, an Al ₂ O ₃ film, or the like can be applied. The thickness of the insulating layer 3 can be determined in consideration of the geometric plane size of the MIM reflector 50 and the required capacitor value in terms of circuit characteristics, and is, for example, about several tens nm to several hundreds nm. . The insulating layer 3 can be formed by a CVD method or a sputtering method.

Similarly, the interlayer insulating film 9 can be formed of, for example, a SiO ₂ film. In addition, a Si ₃ N ₄ film, a SiON film, a HfO ₂ film, an Al ₂ O ₃ film, or the like can be applied. As shown in FIG. 18A, the thickness of the interlayer insulating film 9 is such that the total thickness of the second electrode 2a and the interlayer insulating film 9 is substantially the same as the thickness of the first electrode 4. Is set to The interlayer insulating film 9 can be formed by a CVD method or a sputtering method.

  The insulator substrate 10 is preferably made of a substrate having a lower dielectric constant than that of the semiconductor layer 91a in order to detect radio waves efficiently. As the insulating substrate 10 made of a low dielectric constant material, for example, a polyimide resin substrate, a Teflon (registered trademark) substrate, or the like can be applied. The thickness of the insulator substrate 10 is, for example, about 200 μm.

In the terahertz detection element according to Modification 2, since the upper side is air, the relative permittivity ε _air = 1. When a polyimide resin substrate is used as the insulator substrate 10, since the relative dielectric constant ε _poly = 3.5 of the polyimide resin, the ratio of the received radio wave from below the insulator substrate 10 to the total received radio wave is ε _poly ^3/2 / (ε _air ^3/2 + ε _poly ^3/2 ) = 0.87. That is, about 87% of the total received radio waves are detected from the insulator substrate 10 side, and the received radio waves detected from the lateral direction through the horn opening 80 are relatively increased.

Further, when a Teflon (registered trademark) resin substrate is used as the insulator substrate 10, since the relative permittivity ε _tef of the Teflon (registered trademark) is 2.1, the lower portion of the insulator substrate 10 with respect to the entire received radio wave The ratio of the detected radio wave is represented by ε _tef ^3/2 / (ε _air ^3/2 + ε _tef ^3/2 ) = 0.75. That is, about 75% of the total received radio waves are detected from the insulator substrate 10 side, and the received radio waves detected from the lateral direction through the horn opening 80 are relatively increased.

As shown in FIG. 18A, the MIM reflector 50 is formed from a structure in which an insulating layer 3 is interposed between the first electrode 4 a and the second electrode 2. As is clear from FIG. 18B, the active element 90 made of RTD is disposed on the insulator substrate 10 via the first electrode 4a. The first electrode 4a is disposed in contact with the n ⁺ GaInAs layer 91b of the RTD. The second electrode 2 is disposed in contact with the n ⁺ GaInAs layer 91a of the RTD. Further, the first electrode 4 (4b, 4c) is disposed so as to extend on the insulator substrate 10.

Thus, since the 1st electrode 4 is extended and arrange | positioned on the insulator board | substrate 10, the 1st electrode 4 and the 2nd electrode 2 are not mutually short-circuited, but RTD. A predetermined DC bias voltage can be applied between the n ⁺ GaInAs layer 91a and the n ⁺ GaInAs layer 91b.

  Note that a bonding wire 12b is connected to the first electrode 4, a bonding wire 12a is connected to the second electrode 2a, and a DC power source is connected between the first electrode 4 and the second electrode 2a. 15 is connected. In addition, a resistor (not shown) for preventing parasitic oscillation is connected between the first electrode 4 and the second electrode 2a.

  In the structure of the terahertz detection element according to the modified example 2, the insulator substrate 10 is pasted directly on the first electrode 4 and on the second electrode 2 via the interlayer insulating film 9, and the semiconductor substrate 1 is removed by etching. The inverted structure after the above is expressed as shown in FIGS. 18 (a) and 18 (b). As shown in FIGS. 18A and 18B, in the terahertz detection element according to the second modification, the semiconductor layer 91a is disposed on the second electrode 2, but the second electrode 2a is also exposed. Therefore, an electrode extraction process such as wire bonding can be easily performed on the second electrode 2a.

  In the method for manufacturing a terahertz detection element according to Modification 2, as shown in FIGS. 2A and 2B, after the semiconductor layer 91a is formed on the semiconductor substrate 1, the width of the semiconductor layer 91a is formed by patterning. And the pattern width of the second electrode 2 formed on the semiconductor layer 91a is narrowed. In the remaining portion, a second electrode 2a is formed which is connected to the second electrode 2 and has a predetermined width and is relatively thick. As a result, as shown in FIGS. 2A and 2B, a structure in which the second electrode 2a is in contact with the semiconductor substrate 1 is obtained.

  Next, as shown in FIGS. 18A and 18B, the insulator substrate 10 is pasted directly on the first electrode 4 and on the second electrode 2 via the interlayer insulating film 9, A vertically inverted structure after the semiconductor substrate 1 is removed by etching is obtained.

  Next, as shown in FIG. 16, the bonding wire 12b is connected to the first electrode 4, and the bonding wire 12a is connected to the second electrode 2a, whereby the electrode is taken out.

  The semiconductor substrate 1 is formed of, for example, a semi-insulating InP substrate and has a thickness of about 600 μm, for example. As the etching solution for the InP substrate, for example, a hydrochloric acid-based etching solution can be applied.

  In the terahertz detection element according to Modification 2, a schematic bird's-eye view structure after the step of attaching the insulator substrate 10 having a thickness d to the sample surface and removing the semiconductor substrate by etching is represented as shown in FIG. A schematic bird's-eye view structure viewed from the back surface of FIG. 19 is expressed as shown in FIG. As is clear from FIG. 19, the first electrode 4 is directly attached to the insulator substrate 10. The second electrodes 2 and 2a are not shown in FIG. 19, but are formed on the insulator substrate 10 via the interlayer insulating film 9, as shown in FIGS. 18 (a) and 18 (b). It is pasted. The detailed structure of FIG. 20 corresponds to FIG.

  As a terahertz detecting element according to the second modification of the embodiment, a schematic cross-sectional structure of a resonant tunneling diode (RTD) applicable to the active element 90 is expressed in the same manner as FIG. Moreover, the schematic cross-sectional structure of the modification is represented similarly to FIG.3 (b). Further, an integrated structure of the terahertz detection element RTD (D) and the terahertz oscillation element RTD (O) formed in the same manufacturing process is expressed in the same manner as in FIG.

  FIGS. 3 and 4 are structural examples arranged on the semiconductor substrate 1, but after the insulator substrate 10 is attached to the first electrode 4a in a subsequent process, the semiconductor substrate 1 is removed by etching. Is done. Therefore, FIGS. 3 and 4 correspond to a schematic cross-sectional structure in the vicinity of the active element 90 just before the insulator substrate 10 is attached.

  As described above, the active element 90 is typically an RTD, but other diodes or transistors may be used. As other active elements, for example, TUNETTT diodes, IMPATT diodes, GaAsFETs, GaN-based FETs, HEMTs, HBTs, and the like can be applied.

  According to the terahertz detection element according to the modified example 2, it is possible to improve the directivity in the lateral direction by using an insulating substrate having a low dielectric constant, and to detect with high directivity in the lateral direction with respect to the substrate with high efficiency. In addition, integration is easy.

-Modification 3 and Modification 4
The electrode pattern structure of the terahertz detection element according to Modification 3 of the embodiment is represented as shown in FIG. 21A, and the electrode pattern structure of the terahertz detection element according to Modification 4 is shown in FIG. Represented as shown.

  The electrode pattern structure of the terahertz detection element according to Modification 3 of the embodiment is an example in which the second electrode 2 constituting the MIM reflector 50 is provided with a stub structure, and the electrode pattern structure of the terahertz detection element according to Modification 4 These are examples in which the first electrode 4 constituting the MIM reflector 50 is provided with a stub structure. As apparent from FIG. 18A, since the semiconductor layer 91a is disposed on the second electrode 2, in FIG. 21A and FIG. 21B, the semiconductor layer 91a is displayed. However, the pattern of the second electrode 2 is arranged in the same pattern shape under the semiconductor layer 91a.

  That is, as shown in FIG. 21A, the second electrode 2 includes a plurality of stubs 13 </ b> A in a part constituting the MIM reflector 50.

  In addition, as shown in FIG. 21B, in the portion constituting the MIM reflector 50, the first electrode 4 includes a plurality of stubs 13B.

  The plurality of stubs 13A or 13B may be arranged at equal intervals facing the resonator 60, or may be arranged so that the intervals thereof change.

  A combination of Modification 3 and Modification 4 described above may include a plurality of stubs on both the second electrode 2 and the first electrode 4.

  A resonant circuit is formed by providing a stub with a quarter of the wavelength of the electromagnetic wave in a part of the transmission line of the electromagnetic wave, drawing the electromagnetic wave into the stub, reflecting it, and returning it to the transmission line. I know. This is because only the electromagnetic wave having a wavelength four times the length of the stub out of the electromagnetic wave incident on the transmission line is equivalently short-circuited at the position of the stub, and this electromagnetic wave is reflected thereby. This is a phenomenon that leakage from the transmission line is reduced. According to this method, since the length of the stub is determined to be a quarter wavelength with respect to the wavelength of the input electromagnetic wave, for the electromagnetic wave in which the wavelength of the electromagnetic wave is four times the length of the stub. Although it can be strongly resonated and reflected, an electromagnetic wave having a wide bandwidth has little reflection effect.

  The length of the stub 13A of the third modification is not a quarter wavelength of the electromagnetic wave at the central portion of the incident electromagnetic wave having a band, but is shifted from the quarter. For example, when there is a frequency width to be reflected, it is desired to reflect by providing many stubs 13A having a length of 2 to 3 wavelengths for partially reflecting electromagnetic waves having a median frequency of the frequency width. It is possible to reflect electromagnetic waves having a frequency range in a wide range.

  Naturally, the reflectivity of the electromagnetic wave is smaller than that of the quarter wavelength, but still a considerable amount of reflection occurs compared to the case where there is no stub. And, there is an effect of uniformly reflecting a frequency having a certain band (electromagnetic wave having a certain wavelength width) as much as the resonance condition is loose. In addition, the multi-stage stubs have a length that is about half the wavelength of electromagnetic waves having a median frequency of the electromagnetic wave frequency to be reflected, thereby strengthening the interference between the reflections from each stub (Bragg). Reflection) occurs, the reflected waves are superimposed, and the reflectance becomes a large value of almost 100%. Depending on the length, number, and interval of the stubs, the reflected frequency width and the center frequency are comprehensively determined.

₀ the center wavelength of the electromagnetic wave lambda having a predetermined bandwidth, and the distance of the stub and lambda _0/2, the reflectivity can be obtained a wavelength range Δλ of electromagnetic waves close to 100%. At this time, the length of the stub, it is preferable to design the 2～3Ramuda ₀ or more. Further, when the width of the stub is half of the stub interval, a large reflectance close to 100% is obtained with a small number of about 5 to 10 stubs. When the stub width is other than that, it is necessary to increase the number of stubs in order to obtain a large reflectance, and the frequency width is also narrowed. However, these lengths are not limited and are defined in terms of design in relation to the reflected bandwidth.

  In the third modification, the leaked electromagnetic wave is reflected by the stub 13A and the MIM reflector and returned to the resonator 60 side. Since the reflected electromagnetic wave is detected as a received radio wave, the electromagnetic wave detected by the active element 90 has a high output.

  Also in the modified example 4, since the operation of the stub 13B is the same as that of the stub 13A, a duplicate description is omitted.

  By providing multistage stubs on both the second electrode 2 and the first electrode 4, it is possible to obtain the same large reflectivity with about half the number of stubs as compared with the case of only one. In addition, the degree of freedom in design when determining the frequency width and center frequency can be increased, which is extremely effective in design. Note that the length, number, and interval of the stubs attached to both the second electrode 2 and the first electrode 4 are not necessarily equal, and can be freely changed in design.

  According to the terahertz detection element according to the modification 3 and the modification 4, the directivity in the lateral direction is improved by using an insulating substrate having a low dielectric constant, and high efficiency and high output are achieved. Detection can be performed with high directivity, and integration is facilitated.

  According to the terahertz detecting element according to the modified example 3 and the modified example 4, by using a low dielectric constant insulator substrate, the directivity in the lateral direction is improved, and by combining the stub structure with the electrodes constituting the MIM reflector, It becomes possible to detect electromagnetic waves more efficiently in the direction horizontal to the substrate and with high directivity.

-Modification 5-
A schematic planar configuration of the electrode pattern structure of the terahertz detecting element according to the fifth modification of the embodiment is expressed as shown in FIG.

  Also in the terahertz detection element according to the modified example 5, the configuration of the first electrode 4 (4a, 4b, 4c), the second electrode 2, 2a, the MIM reflector 50, the resonator 60, and the active element 90 is the same as that of the modified example 2. Since it is the same, in the following, redundant description is omitted.

  As shown in FIG. 22, the terahertz detection element according to Modification 5 includes an insulator substrate 10, a first electrode 4 (4 a, 4 b, 4 c) disposed on the insulator substrate 10, and a first electrode Insulating layer 3 (FIG. 18) disposed on 4a (FIG. 18), interlayer insulating film 9 (FIG. 18) disposed on insulator substrate 10, and disposed on interlayer insulating film 9 and the first A second electrode 2, 2 a disposed opposite to the first electrode 4 via the insulating layer 3 with respect to the electrode 4 a, a semiconductor layer 91 a disposed on the second electrode 2, and an insulator A first slot line electrode 41 disposed adjacent to the first electrode 4 on the substrate 10 and opposite the first electrode 4 on the opposite side of the second electrode 2a; A second slot disposed adjacent to the second electrode 2a and opposite the second electrode 2a on the side opposite to the first electrode 4 The in-electrode 21, the MIM reflector 50 formed between the first electrode 4 a and the second electrode 2 with the insulating layer 3 interposed therebetween, and the first electrode facing the insulator substrate 10 adjacent to the MIM reflector 50. The resonator 60 disposed between the electrode 4 and the second electrode 2, the active element 90 disposed substantially at the center of the resonator 60, and the resonator 60 are adjacent to each other on the insulator substrate 10. A first waveguide 70 disposed between the first electrode 4 and the second electrode 2, and the first electrode 4 and the second electrode adjacent to the first waveguide 70 and opposed to the insulator substrate 10. A first horn opening 80 disposed between the electrodes 2, a second waveguide 71 disposed between the first electrode 4 and the first slot line electrode 41 opposed to each other on the insulator substrate 10, and a second conductor. The first electrode 4 and the first slot line electrode that are adjacent to the waveguide 71 and face the insulator substrate 10. A second horn opening 81 disposed between the first substrate 2, a second waveguide 2 a facing the insulator substrate 10, a third waveguide 72 disposed between the second slot line electrodes 21, and a third waveguide 72, the second electrode 2 a facing the insulator substrate 10 and the third horn opening 82 disposed between the second slot line electrodes 21 are provided.

  As in the second modification, the active element 90 is typically an RTD, but can be configured by other diodes or transistors. As other active elements, for example, TUNETTT diodes, IMPATT diodes, GaAsFETs, GaN-based FETs, HEMTs, HBTs, and the like can be applied.

  The horn openings 80 to 82 constitute an open horn antenna.

  In the terahertz detection element according to Modification 5, as shown in FIG. 22, the width W4 of the slot line electrodes 21 and 41 at the output end is, for example, about 160 μm. As shown in FIG. 22, the width D20 of the horn opening 80, the width D10 of the horn openings 81 and 82, and the width W4 of the slot line electrodes 21 and 41 at the output end can be changed as appropriate.

  The waveguide 70 is disposed in the opening of the resonator 60.

  The MIM reflector 50 is disposed in a closed portion opposite to the opening of the resonator 60.

  In the portion constituting the MIM reflector 50, the second electrode 2 may include a plurality of stubs similar to those of the third modification shown in FIG. Similarly, in the portion constituting the MIM reflector 50, the second electrode 2 may include a plurality of stubs similar to those of the modification 4 shown in FIG.

  In the above description, the plurality of stubs may be arranged at equal intervals facing the resonator 60, or may be arranged so that the intervals change.

  The insulator substrate 10 is preferably made of a substrate having a lower dielectric constant than that of the semiconductor layer 91a in order to detect radio waves efficiently in the lateral direction and with high directivity. As the insulator substrate 10 made of a low dielectric constant material, for example, a polyimide resin substrate, a Teflon (registered trademark) substrate, or the like can be applied as in the first embodiment.

  When a polyimide resin substrate is used as the insulator substrate 10, about 87% of the total received radio waves are detected from the insulator substrate 10 side, and the received radio waves detected from the lateral direction through the horn opening 80 are The relatively increasing point is the same as in the second modification.

  Further, when a Teflon (registered trademark) resin substrate is used as the insulator substrate 10, about 75% of the total received radio waves are detected from the insulator substrate 10 side as in the second modification, and the horn opening The received radio waves detected from the lateral direction via 80 are relatively similar to the second modification in that they increase relatively.

  In the terahertz detection element according to the modified example 5, a pair of tapered slots having the same shape is formed on both sides of the tapered slot antenna including the first electrode 4 and the second electrode 2 connected to the active element 90. By arranging the line electrodes 41 and 21, the directivity of the detected radio wave is further improved as compared with the second modification.

  According to the terahertz detecting element according to the modified example 5, the pair of tapered slot line electrodes 41 and 21 are arranged in parallel on both sides of the tapered slot antenna including the first electrode 4 and the second electrode 2. As a result, even if the tapered slot antenna is integrated on the insulator substrate 10, the influence of the insulator substrate 10 can be suppressed and sufficient directivity of the detected radio wave can be obtained.

  The electric field spread from the tapered slot antenna composed of the first electrode 4 and the second electrode 2 in the center is drawn into a pair of slot line electrodes 41, 21 provided on both sides, and the slot line electrodes 41, 21 And is returned to the first electrode 4 and the second electrode 2 at the center. At this time, standing waves are formed in the first electrode 4, the second electrode 2, and the slot line electrodes 41, 21 in the center, and electromagnetic waves are received inside by the reflected electric field. The radiation electromagnetic fields from the first electrode 4 and the second electrode 2 at the center and the pair of slot line electrodes 41 and 21 interfere with each other, thereby improving the directivity of the received electromagnetic wave.

  According to the terahertz detection element according to the modified example 5, the directivity in the lateral direction is improved by using an insulating substrate having a low dielectric constant, and the standing wave is effectively generated by arranging the slot line electrodes in parallel. As a result, it is possible to receive signals with higher efficiency and higher output, higher directivity in the lateral direction with respect to the substrate, and easy integration.

-Modification 6-
A schematic planar configuration of the electrode pattern structure of the terahertz detection element according to the sixth modification of the embodiment is expressed as shown in FIG.

  Also in the terahertz detection element according to Modification 6, the first electrode 4, the second electrode 2, the MIM reflector 50, the resonator 60, the active element 90, the first slot line electrode 41, and the second slot line electrode 21 Since the configuration is the same as that of the second embodiment, redundant description will be omitted below.

  As shown in FIG. 23, the terahertz detection element according to Modification 6 further includes a pair of slot line electrodes 22 and 42 arranged in parallel to the electrode pattern configuration of Modification 5 shown in FIG. Yes. That is, the third slot line electrode 42 disposed on the insulator substrate 10 adjacent to the first slot line electrode 41 and opposite to the first electrode 4 and facing the first slot line electrode 41; A fourth slot line electrode 22 disposed adjacent to the second slot line electrode 21 on the insulator substrate 10 and opposite to the second slot line electrode 21 on the opposite side of the second electrode 2a; A fourth waveguide 74 disposed between the first slot line electrode 41 and the third slot line electrode 42 facing on the substrate 10, and a first waveguide facing the insulator substrate 10 adjacent to the fourth waveguide 74. A fourth horn opening 84 disposed between the first slot line electrode 41 and the third slot line electrode 42, and between the second slot line electrode 21 and the fourth slot line electrode 22 facing on the insulator substrate 10. The fifth waveguide 73 disposed and the fifth horn opening disposed between the second slot line electrode 21 and the fourth slot line electrode 22 facing the insulator substrate 10 adjacent to the fifth waveguide 73. Part 83.

  The insulator substrate 10 is preferably made of a substrate having a lower dielectric constant than that of the semiconductor layer 91a in order to detect radio waves efficiently in the lateral direction and with high directivity. As the insulator substrate 10 made of a low dielectric constant material, for example, a polyimide resin substrate, a Teflon (registered trademark) substrate, or the like can be applied as in the first embodiment.

  In the configuration of FIG. 23, the directivity is further improved by further arranging a pair of slot line electrodes 22, 42 in parallel outside the slot line electrodes 21, 41.

  According to the terahertz detecting element according to the modified example 6, the horizontal directionality is improved by using an insulating substrate having a low dielectric constant, and two pairs of slot line electrodes are arranged in parallel to make a standing wave effective. Therefore, it is possible to detect with high directivity in the lateral direction with respect to the substrate with high efficiency and high output, and integration is easy.

  According to the terahertz detection element of the present invention, since the antenna is integrated on the substrate to detect the terahertz electromagnetic wave, the detector is dramatically smaller than the conventional technology, and the terahertz electromagnetic wave can be detected with high sensitivity and low noise. It is.

  According to the terahertz detection element of the present invention, when combined with a terahertz oscillation element that can be manufactured in the same process, the transmitter and the detector are remarkably smaller than the prior art, and the terahertz electromagnetic wave with high sensitivity and low noise is obtained. It is also possible to provide a wireless transmission / reception system.

  Further, the terahertz detection element applied to such a terahertz wireless communication system may be disposed on a Teflon (registered trademark) substrate and applied with an optimum bias by an SMA connector in order to demodulate at high speed.

  Further, since the terahertz detection element (RTD) according to the embodiment can be used as a terahertz oscillation element, it is possible to configure a device that functions as an oscillation element and a detection element with the same element.

  According to the present invention, it is possible to provide a low noise terahertz detecting element using a resonant tunneling diode.

[Other embodiments]
As described above, the terahertz detection element according to the embodiment and the modified example thereof has been described. However, it is understood that the description and drawings constituting a part of this disclosure are exemplary and limit the present invention. should not do. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  As described above, the present invention includes various embodiments not described herein.

  The terahertz detection element of the present invention can operate with low noise in the terahertz band frequency range, so in addition to terahertz imaging, large-capacity communication and information processing, measurement and security fields in various fields such as physical properties, astronomy, and organisms It can be applied to a wide range of fields.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2, 2a ... 2nd electrode 3 ... Insulating layer 4, 4a, 4b, 4c ... 1st electrode 5, 6 ... Concave part 7 ... Convex part 8 ... Protrusion part 9 ... Interlayer insulating film 10 ... Insulator Substrate 13A, 13B ... Stub 15 ... DC power supply 21, 22, 41, 42 ... Slot line electrode 38 ... Terahertz oscillation element 44 ... Terahertz detection element 50 ... MIM reflector 60 ... Resonator 70, 71, 72, 73, 74 ... Waveguide 80, 81, 82, 83, 84 ... Horn opening 90 ... Active element 91a ... Semiconductor layer 100 ... Terahertz transmitter 200 ... Terahertz receiver

Claims (15)

A semiconductor substrate;
A second electrode disposed on the semiconductor substrate;
An insulating layer disposed on the second electrode;
A first electrode disposed with respect to the second electrode through the insulating layer and disposed on the semiconductor substrate so as to face the first electrode;
An MIM reflector formed between the first electrode and the second electrode across the insulating layer;
A resonator disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the MIM reflector;
An active element disposed substantially in the center of the resonator;
A waveguide disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the resonator;
A terahertz detection element, comprising: a horn opening disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the waveguide. An insulator substrate;
A first electrode disposed on the insulator substrate;
An insulating layer disposed on the first electrode;
An interlayer insulating film disposed on the insulator substrate;
A second electrode disposed on the interlayer insulating film and disposed opposite to the first electrode via the insulating layer with respect to the first electrode;
A semiconductor layer disposed on the second electrode;
An MIM reflector formed between the first electrode and the second electrode across the insulating layer;
A resonator disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the MIM reflector;
An active element disposed substantially in the center of the resonator;
A waveguide disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the resonator;
A terahertz detection element, comprising: a horn opening disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the waveguide. An insulator substrate;
A first electrode disposed on the insulator substrate;
An insulating layer disposed on the first electrode;
An interlayer insulating film disposed on the insulator substrate;
A second electrode disposed on the interlayer insulating film and disposed opposite to the first electrode via the insulating layer with respect to the first electrode;
A semiconductor layer disposed on the second electrode;
A first slot line electrode disposed on the insulator substrate adjacent to the first electrode and opposite to the second electrode and facing the first electrode;
A second slot line electrode disposed on the insulator substrate adjacent to the second electrode and opposite to the first electrode and facing the second electrode;
An MIM reflector formed between the first electrode and the second electrode across the insulating layer;
A resonator disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the MIM reflector;
An active element disposed substantially in the center of the resonator;
A first waveguide disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the resonator;
A first horn opening disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the first waveguide;
A second waveguide disposed between the first electrode and the first slot line electrode facing each other on the insulator substrate;
A second horn opening disposed between the first electrode and the first slot line electrode facing the insulator substrate adjacent to the second waveguide;
A third waveguide disposed between the second electrode and the second slot line electrode facing each other on the insulator substrate;
A terahertz detection comprising: a second horn opening disposed between the second electrode facing the insulator substrate and the second slot line electrode adjacent to the third waveguide. element. A third slot line electrode disposed on the insulator substrate adjacent to the first slot line electrode and opposite the first slot line electrode to face the first slot line electrode;
A fourth slot line electrode disposed adjacent to the second slot line electrode on the insulator substrate and opposite to the second slot line electrode on the opposite side of the second electrode;
A fourth waveguide disposed between the first slot line electrode and the third slot line electrode facing each other on the insulator substrate;
A fourth horn opening disposed between the first slot line electrode and the third slot line electrode facing the insulator substrate adjacent to the fourth waveguide;
A fifth waveguide disposed between the second slot line electrode and the fourth slot line electrode facing each other on the insulator substrate;
The fifth horn opening disposed between the second slot line electrode and the fourth slot line electrode facing the insulator substrate adjacent to the fifth waveguide. Item 4. The terahertz detecting element according to Item 3.   The semiconductor substrate is thinned in a region where the first electrode and the second electrode forming the resonator, the waveguide, and the horn opening are disposed. The terahertz detection element according to claim 1.   2. The active element is any one of a resonant tunnel diode, a tannet diode, an impat diode, a GaAs field effect transistor, a GaN FET, a high electron mobility transistor, and a heterojunction bipolar transistor. The terahertz detection element of any one of -4.   The terahertz detection element according to any one of claims 1 to 4, wherein the horn opening constitutes an opening horn antenna.   5. The terahertz detection element according to claim 2, wherein the insulator substrate is made of a substrate having a dielectric constant lower than that of the semiconductor layer.   The terahertz detecting element according to claim 1, wherein the waveguide is disposed in an opening of the resonator.   5. The terahertz detection element according to claim 1, wherein the MIM reflector is disposed in a closed portion opposite to the opening of the resonator.   5. The terahertz detection element according to claim 1, wherein the second electrode includes a plurality of stubs in a portion constituting the MIM reflector.   5. The terahertz detection element according to claim 1, wherein the first electrode includes a plurality of stubs in a portion constituting the MIM reflector.   The terahertz detection element according to claim 11, wherein the plurality of stubs are arranged at equal intervals so as to face the resonator. The terahertz detecting element according to claim 11 or 12, wherein the plurality of stubs are arranged so as to face the resonator and change their intervals. A terahertz transmitter including a terahertz oscillation element;
A terahertz receiver including the terahertz detection element, wherein the terahertz detection element is the terahertz detection element according to any one of claims 1 to 14.