KR20240046080A - THz transceiver with monolithic integration - Google Patents

Abstract

The present invention relates to a terahertz transceiver, comprising: a gun diode fabricated on a substrate; and a Schottky barrier diode manufactured on a substrate, wherein the Gunn diode and the Schottky barrier diode are formed with the same epi structure.

Description

Integrated terahertz transceiver {THz transceiver with monolithic integration}

The present invention relates to an integrated terahertz transceiver.

A terahertz band transceiver is an integrated module composed of elements capable of simultaneous or sequential transmission and reception of terahertz (THz) waves within a single chip.

Terahertz band transceivers can be applied in a variety of ways, from spectroscopy, imaging, and non-destructive testing to two-way communication applications, and are a key component in miniaturizing systems, reducing cost, reducing power consumption, and improving ease of use.

The transmitter (Tx) and receiver (Rx) that make up the terahertz transceiver are composed of a Gunn diode (Tx) and a Schottky barrier diode (SBD (Rx)), respectively, and use the same epi structure. Integration is possible through a single substrate process, and by using epitaxial grown on InP or GaAs, MMIC (Monolithic Microwave Integrate Circuit) can be configured through integration of elements such as existing compound semiconductor-based oscillators, low-noise amplifiers, power amplifiers, and switches. It is easy to

The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2014-0012937 (2014.02.04).

According to one aspect, the problem to be achieved by the present invention is to apply Gunn diodes and Schottky barrier diodes as transmitting and receiving elements, respectively, to provide an integrated terahertz device manufactured on a substrate using the same epi structure without a separate chip or die bonding process. The goal is to provide a transceiver.

According to one aspect of the present invention, the present invention includes a gun diode manufactured on a substrate; and a Schottky barrier diode fabricated on a substrate, wherein the Gunn diode and the Schottky barrier diode are formed in the same epi structure.

According to one aspect of the present invention, the present invention applies Gunn diodes and Schottky barrier diodes as transmitting and receiving elements, respectively, and is manufactured on a substrate using the same epi structure without a separate chip or die bonding process.

According to another aspect of the present invention, the present invention can be mass-produced in an integrated form, is easy to integrate with other compound-based MMIC (Monolithic microwave integrated circuit), and can be used from millimeter waves to terahertz bands depending on the length of the channel. possible.

Figure 1 is a cross-sectional view of a terahertz transceiver in which the Gunn diode and Schottky barrier diode are separated according to an embodiment of the present invention.
Figure 2 is a cross-sectional view of a terahertz transceiver sharing the cathode of a Gunn diode and a Schottky barrier diode according to an embodiment of the present invention.
Figure 3 is a schematic diagram of the band structure of the conduction band of GaAs of the Gunn diode.
Figure 4 is a diagram showing the electronic drift velocity-electric field characteristic curve of the Gunn diode.
Figure 5 is a diagram showing the current density-electric field characteristic curve of the Gunn diode.
Figure 6 is a diagram showing the growth and movement of the dipole layer in the negative conduction section of the Gunn diode (left: change in semiconductor internal carrier concentration over time, right: change in internal electric field distribution).
Figure 7 is a diagram showing an example of the relationship between the oscillation frequency (f _osc. ) and channel length (L- _ac ) of the planar Gunn-diode.
Figure 8 is a band alignment diagram according to external bias of a metal-semiconductor Schottky junction.
9 is a schematic diagram of an antenna-integrated Schottky barrier diode.
Figure 10 is a diagram showing the principle of zero-bias detection of external electromagnetic waves by the rectification action of a Schottky barrier diode.
Figure 11 is a diagram showing the current-voltage characteristics of an InGaAs-based Schottky barrier diode.
Figure 12 is a diagram showing an example of current and voltage response characteristics according to external voltage.
Figure 13 is a diagram showing an example in which the electrode 150 of the Gunn diode and the cathode of the Schottky barrier diode are separated or shared according to an embodiment of the present invention.

Below, an example of a terahertz transceiver according to an embodiment of the present invention will be described. In this process, the thickness of lines or sizes of components shown in the drawing may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, definitions of these terms should be made based on the content throughout this specification.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

Implementations described herein may be implemented, for example, as a method or process, device, software program, data stream, or signal. Although discussed only in the context of a single form of implementation (eg, only as a method), implementations of the features discussed may also be implemented in other forms (eg, devices or programs). The device may be implemented with appropriate hardware, software, firmware, etc. The method may be implemented in a device such as a processor, which generally refers to a processing device that includes a computer, microprocessor, integrated circuit, or programmable logic device.

Figure 1 is a cross-sectional view of a terahertz transceiver in which the Gunn diode and Schottky barrier diode are separated according to an embodiment of the present invention.

Referring to FIG. 1, the terahertz transceiver 10 according to an embodiment of the present invention includes a Gunn diode 20 manufactured on a substrate 110, and a Schottky transceiver manufactured on the substrate 110. It may include a barrier diode (Schottky Barrier Diode, SBD) 30.

The substrate 110 may be an InP or GaAs substrate, which is a group III-V compound semiconductor.

The Gunn diode 20 and the Schottky barrier diode 30 may be formed on the substrate 110 with the same epi structure.

The Gunn diode 20 and the Schottky barrier diode 30 may be formed separately on the substrate 110.

In another embodiment, Gunn diode 20 and Schottky barrier diode 30 may share a cathode on substrate 110.

Figure 2 is a cross-sectional view of a terahertz transceiver sharing the cathode of a Gunn diode and a Schottky barrier diode according to an embodiment of the present invention.

Referring to FIG. 2, the terahertz transceiver 10 includes a Gunn diode 20 and a Schottky barrier diode 30, and the Gunn diode 20 and the Schottky barrier diode 30 may share a cathode. .

The Gunn diode 20 can be used as a transmitter (Tx), and the Schottky barrier diode 30 can be used as a receiver (Rx).

The Gunn diode 20 is a device that utilizes an oscillation phenomenon due to the negative resistance characteristic caused by the nonlinearity of the mobility of electrons in a semiconductor with respect to an external electric field.

Figure 3 is a schematic diagram of the band structure of the GaAs conduction band of the Gunn diode, Figure 4 is a diagram showing the electronic drift velocity-electric field characteristic curve of the Gunn diode, and Figure 5 is a diagram showing the current density-electric field characteristic curve of the Gunn diode. Figure 6 is a diagram showing the growth and movement of the dipole layer in the negative conduction section of the Gunn diode (left: change in semiconductor internal carrier concentration over time, right: change in internal electric field distribution), and Figure 7 is a diagram showing the growth and movement of the dipole layer in the negative conduction section of the Gunn diode. This diagram shows an example of the relationship between the oscillation frequency (f _osc. ) and channel length (L- _ac ) of a planar Gunn-diode.

When GaAs is applied to the Gunn diode 20 as an active layer, as shown in FIG. 3, when an electric field exceeding the threshold within the semiconductor is applied, electrons distributed in the low energy band (Valley 1) gain energy of 0.3 eV or more. It is mostly transmitted to a higher energy band (Valley 2) and is distributed in that energy band due to the relative difference in effective state density.

Since the effective mass of electrons in Valley 2 increases by more than 8 times, the mobility becomes very low. Above the critical electric field, the speed of electrons actually decreases, so the negative differential mobility in that section (dV _d /dE=- μ ^* ).

As a result, the Gunn diode 20 exhibits electromagnetic drift speed-electric field and current density-electric field characteristics as shown in FIGS. 4 and 5.

Under bias conditions where such negative differential mobility (C section in Figure 4) appears, as the electric field in the domain (dipole layer) formed due to the imbalance of electron concentration inside the semiconductor increases, the electric field inside the dipole layer becomes higher than outside. As this increases, the drift speed of electrons decreases. Accordingly, electrons on the right side outside the dipole layer escape by drift, and electrons accumulate on the left side, causing the dipole layer to grow. In the grown dipole layer, stable conditions are maintained when the internal electric field of the dipole layer exists at point B and the external electric field exists at point A, so that all electrons drift to the anode at a saturation speed (V _s ), and the change in current when passing through ( An alternating current) appears outside, and then the electric field inside the semiconductor becomes E _C and the process of increasing again is repeated, and a continuous alternating current is generated outside, which can be applied as an alternating current and electromagnetic wave signal source. The transition oscillation frequency of the Gunn diode 20 is determined by the length of the active layer channel (L _ch ) and the speed of the domain formed in the semiconductor (υ _domain ), as shown in Equation 1 below.

L _dead in Equation 1 is the minimum channel length (dead space or dead zone) required for electrons in the channel to transition from the cathode to the conduction band energy band, and corresponds to a resistance component that does not contribute to DC-to-RF conversion. Minimizing it is beneficial to rashes.

Referring to FIG. 7, the oscillation frequency of the Gunn diode 20 is determined by the channel length, and it can be seen that it is possible to generate high frequencies of 100 GHz or more when manufacturing a device with a channel of 2 μm or less by applying In _0.53 Ga _0.47 As as an active layer. .

Figure 8 is a band alignment diagram according to external bias of a metal-semiconductor Schottky junction, Figure 9 is a schematic diagram of an antenna-integrated Schottky barrier diode, and Figure 10 is a no-voltage diagram of external electromagnetic waves due to the rectification action of the Schottky barrier diode. (zero-bias) This is a diagram showing the detection principle, Figure 11 is a diagram showing the current-voltage characteristics of an InGaAs-based Schottky barrier diode, and Figure 12 is a diagram showing an example of current and voltage response characteristics according to external voltage. .

As shown in FIGS. 8 and 9, the Schottky barrier diode 30 operates by detecting electromagnetic waves using the rectification characteristics of the Schottky energy barrier formed by the metal-semiconductor junction.

Unlike a typical p-n type semiconductor junction, it is composed of a metal-n type semiconductor junction and operates by majority carriers (electrons), so it does not have the minority carrier accumulation effect and the reverse recovery time is very short, making it suitable for microwave/terahertz wave detection. The actual detector detects a current or voltage of a magnitude proportional to the output of the signal received by a rectifying action at both terminals of the SBD integrated in the antenna or waveguide. In particular, when using InGaAs and InGaAsP, which have high mobility while forming a relatively low Schottky barrier, it is possible to implement a voltage-free detection method, making it possible to manufacture a terahertz wave detector for room temperature detection with low noise, low power, and high sensitivity. Based on the detection principle by the rectification action of SBD, the responsiveness to the current and voltage caused by the incident wave through the I-V curve can be expressed as Equation 2 and Equation 3 below, assuming that it follows the square-law detection principle.

Here, e is the charge of the electron, α is the ideality coefficient, k- _B is the Boltzmann constant, and T is the absolute temperature.

As shown in Figures 11 and 12, when InGaAs is used as a semiconductor and Ti is used as a metal to form a Schottky junction with a low energy barrier in an SBD device, excellent rectification characteristics and a low threshold voltage of 0.1 V or less can be achieved at the same time. It shows high current and voltage responsiveness around 0V. These characteristics, along with the high mobility (~8000 cm2/V·sec, x=0.47) of In _{1-x Ga} It is possible to manufacture a zero-bias detector.

Meanwhile, the Gunn diode 20 may include a cathode and an anode.

An active layer 120 is formed on the substrate 110, an ohmic layer is formed on the active layer 120, and an electrode 150 is formed on the ohmic layer 140 to form a cathode.

The active layer 120 may form a channel between the electrode 150 and the electrode 150 that generates the current pulse of the Gunn diode 20.

An ohmic layer 140 may be formed on the active layer 120, and an electrode 150 may be formed on the ohmic layer 140 to form an anode.

The active layer 120 has a quantum structure based on In- _1-x Ga _x As, Al _1-x Ga _x As, In _1-x Ga _x As/Al _1-y Ga _y As (0≤x, y≤1) It may be composed of the same type of material.

The ohmic layer 140 facilitates current flow from the active layer 120 to the electrode 150.

The ohmic layer 140 may be formed of an n-type material doped at a concentration of 10 ¹⁸ cm ^-3 or more of the same type used in the active layer 120 and the Schottky layer 130 or a heterogeneous III-V group compound semiconductor. You can.

The channel of the Gunn diode 20 may be formed as a single or multiple channels.

As shown in FIG. 7, the length of the channel determines the oscillation frequency to be used, so the set channel length for each channel may vary, for example, within the range of several μm. The total width of the channel in the device can be formed to be a set channel width, for example, a width of several tens of μm or more, because the current density per channel length ranges from several to several tens of A/mm.

Schottky barrier diode 30 may include a cathode and an anode.

A Schottky layer 130 is formed on the substrate 110, an ohmic layer 140 is formed on the Schottky layer 130, and an electrode 150 is formed on the ohmic layer 140 to form a cathode. It can be.

A dielectric layer 160 may be formed on the Schottky layer 130, and an electrode 150 may be formed on the dielectric layer 160 to form an anode.

The Schottky layer 130 may form a Schottky joint of Schottky bonding layers.

The Schottky layer 130 may be composed of the same type of material among In- _1-x Ga _x As, Al _1-x Ga _x As, and In _1-x Ga _x As/Al _1-y Ga _y As-based quantum structures. there is.

As described above, the active layer 120 and the Schottky layer 130 are In- _1-x Ga _x As, Al _1-x Ga _x As, In _1-x Ga _x As/Al _1-y Ga _y As. As the underlying quantum structure is made of the same material, the Gunn diode 20 and the Schottky barrier diode 30 may be separated or their cathodes may be shared.

The ohmic layer 140 facilitates current flow from the Schottky layer 130 to the electrode 150. The ohmic layer 140 may be formed of an n-type material doped at a concentration of 10 ¹⁸ cm ^-3 or more of the same type used in the active layer 120 and the Schottky layer 130 or a heterogeneous III-V group compound semiconductor. You can.

The Schottky barrier layer may use an electron beam or optical lithography method to form the anode area size to several μm ² or less.

When the frequency to be detected in the Schottky barrier layer is 300 GHz or higher, an etching area 170 may be formed within the Schottky layer 130 to reduce parasitic capacitance. The etching area 170 may form a dielectric having a low dielectric constant in free space or in the operating frequency band of the device.

Meanwhile, the active layer 120 and the Schottky barrier layer describe an example in which the active layer 120 and the Schottky barrier layer formed on the same substrate 110 share a cathode.

Figure 13 is a diagram showing an example in which the electrode of the Gunn diode and the cathode of the Schottky barrier diode are separated or shared according to an embodiment of the present invention.

A transceiver structure capable of single frequency oscillation is shown in Figures 13 (a) and (b) depending on the modulation of the channel length. (a) is a structure in which the cathode is shared within the single-frequency oscillation terahertz transceiver 10, and (b) is a structure in which the cathodes are separated within the single-frequency oscillation terahertz transceiver 10.

A transceiver structure capable of multi-frequency oscillation is shown in Figures 13 (c) and (d). (c) is a structure in which the cathode is shared within the multi-frequency oscillation terahertz transceiver 10, and (d) is a structure in which the cathodes are separated within the multi-frequency oscillation terahertz transceiver 10.

As shown in Figures 13 (e) and (f), the Schottky barrier diode 30 can be implemented by modifying it into a harmonic mixer manufactured with an anti-parallel structure. The electrode structure is not limited to the CPW (Coplanar waveguide) form, and may be formed in the form of a waveguide or integrated into an antenna with narrow-band and wide-band characteristics. For this purpose, an example of a two-terminal electrode 150 structure and an antenna integrated form using the same is shown in Figures 13 (g) and (h). The proposed device includes scalability in the form of a 1D or 2D array that shares the electrode structure or is independently separated, as shown in (i) of FIG. 13. Here, (e) is a structure in which an anti-parallel structure Schottky barrier diode 30 shares a cathode within a transceiver applied as a receiving element, and (f) is an anti-parallel structure SBD. It is a structure in which the cathode is separated within the transceiver applied as a receiving element. (g) is a transceiver structure for antenna integration, (h) is a structure integrated into a broadband antenna, and (i) is a top view of an array-type transceiver.

As such, the terahertz transceiver 10 according to an embodiment of the present invention uses the Gunn diode 20 and the Schottky barrier diode 30 as transmitting and receiving elements, respectively, to transmit the same epitaxial signal without a separate chip or die bonding process. It is manufactured on the substrate 110 using the structure.

In addition, the terahertz transceiver 10 according to an embodiment of the present invention can be mass-produced in an integrated form, is easy to integrate with other compound-based MMICs, and can be utilized from millimeter waves to terahertz bands depending on the length of the channel. possible.

The present invention has been described with reference to the embodiments shown in the drawings, but these are merely illustrative, and those skilled in the art will recognize that various modifications and other equivalent embodiments are possible therefrom. You will understand. Therefore, the scope of technical protection of the present invention should be determined by the scope of the patent claims below.

10: Terahertz transceiver
20: Gunn diode
30: Schottky barrier diode
110: substrate
120: Active layer
130: Schottky layer
140: Ohmic layer
150: electrode
160: Dielectric layer
170: Etching area

Claims (1)

A diode is fabricated on a substrate; and
It includes a Schottky barrier diode fabricated on the substrate,
An integrated terahertz transceiver in which the Gunn diode and the Schottky barrier diode are formed with the same epi structure.

Images