Resonant tunneling diode and high frequency device

Abstract

[Problem] To enlarge a negative resistance region. [Solution] According to the present invention, a resonant tunnel diode comprises: a first electrode layer disposed on a support substrate containing a nitride semiconductor material; a quantum well layer disposed on the first electrode layer; a second electrode layer disposed on the quantum well layer; a first semiconductor layer disposed in the quantum well layer; and a plurality of second semiconductor layers disposed so as to sandwich the first semiconductor layer therebetween and having a band gap larger than that of the first semiconductor layer. A thickness Tw of the first semiconductor layer and a thickness Tb of the second semiconductor layer satisfy 4 nm ≤ Tw + 2 x Tb ≤ 6 nm. The second semiconductor layer contains an element that enlarges a negative resistance region formed in the quantum well layer.

Description

Resonant tunneling diodes and high-frequency devices

[0001] This disclosure relates to resonant tunneling diodes and high-frequency devices.

[0002] In the field of semiconductor technology, research and development of tunneling devices is progressing. Among tunneling diodes, those that utilize the resonant tunneling phenomenon are also called resonant tunneling diodes (RTDs). Resonant tunneling diodes have been proposed for application in semiconductor memory and high-frequency oscillators of 1 THz or higher at room temperature.

[0003] Currently, research and development of resonant tunneling diodes using nitride semiconductor materials is underway. For example, a resistive random-access memory with faster operation than conventional models has been proposed by using a resonant tunneling diode with a potential gradient in the well layer of a quantum well (see Patent Document 1).

[0004] Japanese Patent Publication No. 2018-67727

[0005] On the other hand, when attempting to adapt resonant tunneling diodes to oscillators, improving the output is a challenge. To increase the output of an oscillator using a resonant tunneling diode, it is desirable to expand the negative resistance region of the resonant tunneling diode. Expanding the negative resistance region can be achieved by increasing the resonant tunneling current flowing through the resonant tunneling diode and suppressing the increase in reactive current.

[0006] One method to increase the resonant tunneling current is to reduce the thickness of the well layer. However, reducing the thickness of the well layer may also increase the reactive current, and the negative resistance region may not be sufficiently expanded.

[0007] Therefore, this disclosure provides a resonant tunnel diode and a high-frequency device that can expand the negative resistance region.

[0008] To solve the above problem, according to the present disclosure, there is provided a resonant tunnel diode comprising: a first electrode layer disposed on a supporting substrate including a nitride semiconductor material; a quantum well layer disposed on the first electrode layer; a second electrode layer disposed on the quantum well layer; a first semiconductor layer disposed in the quantum well layer; and a plurality of second semiconductor layers disposed so as to sandwich the first semiconductor layer and having a band gap larger than that of the first semiconductor layer, wherein a thickness Tw of the first semiconductor layer and a thickness Tb of the second semiconductor layer satisfy 4 nm ≤ Tw + 2×Tb ≤ 6 nm, and the second semiconductor layer contains an element that enlarges a negative resistance region formed in the quantum well layer.

[0009] The element may be indium (In).

[0010] A composition ratio of the element relative to a base material of the second semiconductor layer may be 0.1% or more and less than 10%.

[0011] The first semiconductor layer contains gallium (Ga) and nitrogen (N), and the base material of the second semiconductor layer may contain aluminum (Al) and nitrogen (N).

[0012] The first semiconductor layer contains GaN, and the base material of the second semiconductor layer may contain at least one of AlN or AlGaN.

[0013] The Tw may satisfy 0.26 nm ≤ Tw ≤ 4.0 nm.

[0014] The Tb may satisfy 0.5 nm ≤ Tb ≤ 2.87 nm.

[0015] The resonant tunnel diode may further comprise a plurality of spacer layers, wherein the plurality of second semiconductor layers include a third semiconductor layer disposed between the first semiconductor layer and the first electrode layer, and a fourth semiconductor layer disposed between the first semiconductor layer and the second electrode layer, and the plurality of spacer layers include a first spacer layer disposed between the first semiconductor layer and the third semiconductor layer, and a second spacer layer disposed between the first semiconductor layer and the fourth semiconductor layer.

[0016] The values ​​of Tb and Tw may satisfy any of the following conditions: Tb = 2.0 nm and 1.3 nm ≤ Tw ≤ 2.0 nm, Tb = 1.75 nm and 1.5 nm ≤ Tw ≤ 2.0 nm, Tb = 1.5 nm and 1.75 nm ≤ Tw ≤ 2.25 nm, Tb = 1.25 nm and 2.1 nm ≤ Tw ≤ 2.6 nm, Tb = 1.0 nm and 2.5 nm ≤ Tw ≤ 3.0 nm, or Tb = 0.75 nm and 3 nm ≤ Tw ≤ 3.8 nm.

[0017] Furthermore, the present disclosure provides a high-frequency device comprising a resonant tunneling diode and an antenna connected in parallel between the resonant tunneling diode and a reference voltage node, the antenna having a capacitor and an inductor that resonate at a specific frequency.

[0018] A perspective view showing the configuration of a high-frequency device according to an embodiment of this disclosure. A cross-sectional view of the high-frequency device in Figure 1. A circuit diagram showing the equivalent circuit of the high-frequency device according to an embodiment of this disclosure. A cross-sectional view showing the configuration of a resonant tunneling diode according to an embodiment of this disclosure. A waveform diagram showing the I-V characteristics of a resonant tunneling diode. A waveform diagram of the energy band in a resonant tunneling diode. A waveform diagram showing the change in I-V characteristics when the film thickness of the well layer is changed. A waveform diagram showing the relationship between the film thickness of the well layer and the film thickness of the barrier layer and the change in current. A waveform diagram showing the change in I-V characteristics when the In concentration of the barrier layer is changed. A waveform diagram showing the relationship between In concentration and the change in current. A block diagram showing an example of a schematic configuration of a vehicle control system. An explanatory diagram showing an example of the installation position of the external information detection unit and the imaging unit.

[0019] Embodiments of resonant tunneling diodes and high-frequency devices will be described below with reference to the drawings. While the main components of resonant tunneling diodes and high-frequency devices will be described below, there may be components and functions not shown or described. The following description does not exclude any components or functions not shown or described.

[0020] (Embodiments of the Disclosure) Figure 1 is a perspective view showing the configuration of a high-frequency device 1 comprising a resonant tunneling diode 10 according to an embodiment of the Disclosure. Figure 2 is a cross-sectional view of the high-frequency device 1 of Figure 1. Figure 2 shows a cross-section along the line A-A' in Figure 1.

[0021] The high-frequency device 1 in Figure 1 is, for example, a patch antenna type high-frequency device. The high-frequency device 1 can be used as an oscillator or a receiver.

[0022] The high-frequency device 1 shown in Figures 1 and 2 comprises an emitter electrode 2, a collector electrode 3, a dielectric 4, a power supply circuit 5, a resonant tunnel diode 10, an emitter layer (first electrode layer) 11, a collector layer (second electrode layer) 12, and a support substrate 13. Figure 1 illustrates the emitter electrode 2, collector electrode 3, dielectric 4, and power supply circuit 5. Figure 2 illustrates the emitter electrode 2, collector electrode 3, dielectric 4, resonant tunnel diode 10, emitter layer 11, collector layer 12, and support substrate 13.

[0023] The emitter electrode 2 and the collector electrode 3 are, for example, metal electrodes. As shown in Figure 2, the emitter electrode 2 and the collector electrode 3 are arranged so as to sandwich the resonant tunnel diode 10, the emitter layer 11, and the collector layer 12 (hereinafter collectively referred to as the resonant tunnel diode 10) and at least a part of the dielectric 4.

[0024] The emitter electrode 2, collector electrode 3, and dielectric 4 form at least a part of the antenna 20. In this specification, the collector electrode 3 may be referred to as the antenna 20.

[0025] The potential of the emitter electrode 2 is set to a reference level (e.g., ground). In this specification, the emitter electrode 2 is also referred to as the ground electrode.

[0026] The collector electrode 3 inputs a signal based on the voltage supplied from the power supply circuit 5 to the resonant tunnel diode 10. In this specification, the collector electrode 3 is also referred to as the signal electrode.

[0027] The dielectric 4 is arranged so as to surround the power supply circuit 5 and the resonant tunnel diode 10 in a plan view.

[0028] The power supply circuit 5 in Figure 1 includes a filter section (MIM Filter) 6 and a power supply section (power supply pad) 7. The filter section 6 functions as a low-pass filter that separates IF (Intermediate Frequency) signals and DC signals from RF (Radio Frequency) signals. The filter section 6 includes, for example, a MIM (Metal-Insulator-Metal). The power supply section 7 supplies power to the collector electrode 3 via the filter section 6. The collector electrode 3, one terminal of the filter section 6, and the power supply terminal of the power supply section 7 may be formed integrally. The other terminal of the filter section 6 may be formed integrally with the emitter electrode 2.

[0029] As shown in Figure 2, the resonant tunnel diode 10 is placed in the slot portion 8 of the dielectric 4. The resonant tunnel diode 10 is positioned so as to be sandwiched between the emitter layer 11 and the collector layer 12.

[0030] The emitter layer 11 is placed between the support substrate 13 and the resonant tunnel diode 10. The collector layer 12 is placed between the collector electrode 3 and the resonant tunnel diode 10, and electrically connects the collector electrode 3 and one end of the resonant tunnel diode 10.

[0031] The support substrate 13 is, for example, a semiconductor substrate containing a nitride semiconductor material. However, it is not limited to this, and the support substrate 13 may be a substrate containing sapphire, Si (silicon), or SiC (silicon carbide), etc. The support substrate 13 is connected to the emitter electrode 2, for example, by ohmic contact. The emitter electrode 2 is electrically connected to the emitter layer 11 via the support substrate 13.

[0032] Figure 3 is a circuit diagram showing an equivalent circuit of a high-frequency device 1 according to an embodiment of the present disclosure. The resonant tunnel diode 10 in Figure 3 has a negative resistor -Grtd and a capacitor -Crtd connected in parallel between a reference voltage node n1 (e.g., emitter electrode 2) and a signal voltage node n2 (e.g., collector electrode 3). The negative resistor -Grtd can be realized by applying a bias voltage within a predetermined range (negative resistance region) to the resonant tunnel diode 10.

[0033] The antenna 20 in Figure 3 has a capacitor Cant, an inductor Lant, a resistor Gloss, and a resistor Grad connected in parallel with a negative resistor Grtd and a capacitor Crd. The resistor Gloss includes, for example, power loss (conductor loss) due to current generated on the surface of the collector electrode 3. The resistor Grad includes, for example, loss due to radiation from the antenna 20.

[0034] The resistive Gloss and resistive Grad act to attenuate the amplitude of the standing wave within the antenna 20. In contrast, the negative resistance -Grtd cancels out the effects of resistive Gloss and Grad, allowing the amplitude of the standing wave to be maintained (oscillate). The oscillation condition for antenna 20 can be expressed as Grtd > Gloss + Grad.

[0035] Here, the absolute value of the negative resistance -Grtd decreases as the oscillation frequency increases. Therefore, there is an upper limit to the oscillation frequency that satisfies the above oscillation conditions. Consequently, in order to make the antenna 20 oscillate at a higher oscillation frequency, it is desirable to increase the absolute value of Grtd over a wide oscillation frequency range.

[0036] The high-frequency device 1 in Figure 3 can be used as a receiver. In this case, the capacitor Can and the inductor Lan may be used as a resonator 21 that resonates with a specific frequency radio signal among the radio signals received by the antenna 20 (collector electrode 3).

[0037] Figure 4 is a cross-sectional view showing the configuration of a resonant tunneling diode 10 according to an embodiment of this disclosure. The resonant tunneling diode 10 in Figure 4 has a lower spacer layer (first spacer layer) 22, a quantum well layer 23, and an upper spacer layer (second spacer layer) 24, which are stacked in this order from the emitter layer 11 side. The quantum well layer 23 also has a lower barrier layer (first barrier layer, or third semiconductor layer) 25, a well layer (first semiconductor layer) 26, and an upper barrier layer (second barrier layer, or fourth semiconductor layer) 27, which are stacked in this order from the lower spacer layer 22 side. In this specification, some or all of the components in Figure 4 may be referred to as semiconductor layers.

[0038] The resonant tunneling diode 10 in Figure 4 includes a nitride semiconductor material. Specifically, the emitter layer 11, collector layer 12, lower spacer layer 22, upper spacer layer 24, and well layer 26 include, for example, GaN (gallium nitride). The lower barrier layer 25 and upper barrier layer 27 (hereinafter collectively referred to as the barrier layer) include, for example, AlN (aluminum nitride) or AlGaN (aluminum gallium nitride). Below, an example in which the barrier layer (second semiconductor layer) includes AlN will be described. The barrier layer has a larger band gap than the well layer 26.

[0039] The lower barrier layer 25 and the upper barrier layer 27 may contain indium (In).

[0040] The resonant tunnel diode 10 may be configured to include a plurality of well layers 26. Alternatively, the resonant tunnel diode 10 may be configured to include a plurality of barrier layers arranged to sandwich the plurality of well layers 26.

[0041] The characteristics of the resonant tunneling diode 10 will be explained using Figures 5 and 6. Figure 5 is a waveform diagram showing the I-V characteristics of the resonant tunneling diode 10. The horizontal axis of Figure 5 shows the voltage (Voltage [V]) applied to the resonant tunneling diode 10. The vertical axis of Figure 5 shows the current (Current [A]) flowing through the resonant tunneling diode 10.

[0042] Figure 5 shows the curve J representing the change in current flowing through the resonant tunneling diode 10. rtd (Hereinafter, the current J rtdalso referred to as) is illustrated. Further, tunnel current J RT and thermionic current J TH are illustrated. Current J rtd is tunnel current J RT and thermionic current J TH using, for example, J rtd = J RT + J TH can be expressed as.

[0043] FIG. 6 is a waveform diagram of an energy band in the resonant tunneling diode 10. The horizontal axis of FIG. 5 indicates the distance from the collector electrode 3 (Distance [cm]), and the vertical axis of FIG. 5 indicates potential energy (Energy [eV]).

[0044] The lower barrier layer 25 and the upper barrier layer 27 have higher potential energy compared to other semiconductor layers. For this reason, the energy band of the conduction band of the resonant tunneling diode 10 has a convex shape in the lower barrier layer 25 and the upper barrier layer 27.

[0045] In FIG. 6, thermionic current J TH and tunnel current J RT are illustrated. Thermionic current J TH is current that flows over the potential barrier of the barrier layer. Tunnel current J RT is current that flows by tunneling through the potential barrier of the barrier layer.

[0046] Discrete quantum levels E R1 , E R2 , and E R3 are formed within the well layer of the resonant tunneling diode. FIG. 6 illustrates discrete quantum levels E R1 , E R2 , and E R3 within the well layer 26. In the resonant tunneling diode 10, while no voltage (bias voltage) is applied, the potentials (Fermi potential E f ) of the emitter electrode 2 and the collector electrode 3 are lower than the quantum level E R1 in the well layer 26, so no current flows.

[0047] The bias voltage applied to the resonant tunneling diode 10 is increased, and the Fermi potential E fis quantum level E R1 When this coincides, the charge tunnels through the potential barrier of the barrier layer, producing a tunneling current (resonant tunneling current) J. RT A current flows through (also known as quantum tunneling).

[0048] Quantum energy levels have an energetic extent due to thermal fluctuations or non-uniformity of well layer thickness, therefore the Fermi potential E f is E R1 As you approach, the tunnel current J RT The current begins to flow, but the tunnel current J RT is the Fermi potential E f is quantum level E R1 A peak occurs when it matches the specified value.

[0049] If the bias charge is further increased, the Fermi potential E f is quantum level E R1 Because it deviates from the tunnel current J RT It decreases, but on the other hand, the quantum level E R2 As you approach, the tunnel current J RT It increases. Fermi potential E f This increases further to quantum level E R2 When it matches, the tunnel current J returns RT This is the peak. This corresponds to quantum level E. R3 The same applies to this case as well.

[0050] Fermi potential E f is quantum level E R3 When deviating from this, the tunnel current J RT On the other hand, as the bias voltage increases, the Fermi potential E decreases. f When the potential barrier height increases, the effective barrier height for charges (e.g., electrons) decreases, and the thermionic current J is generated when charges overcome the potential barrier of the barrier layer. TH It becomes more dominant.

[0051] Quantum level E R1 , E R2 , and E R3 The tunnel current J generated in each of these locations RT This is determined by the barrier layer thickness, well layer thickness, and electron energy for each. For example, ER1 Tunnel current J RT The current is very small and hardly observable. Thus, the current-voltage characteristic of the resonant tunneling diode 10 is the tunneling current J. RT and thermionic current J TH It is determined by the sum of the two.

[0052] Figure 5 illustrates the voltage ranges A1, A2, and A3. Quantum levels As shown in Figure 5, the thermionic current J TH In the voltage range A1 to A3, it increases monotonically as the voltage rises.

[0053] Tunnel current J RT In voltage range A1, the current J increases monotonically as the voltage rises. As a result, in voltage range A1, the current J rtd It increases monotonically until it reaches its peak.

[0054] Tunnel current J RT In voltage ranges A2 and A3, the thermionic current J decreases monotonically as the voltage increases. Also, in voltage range A2, TH It is small. Therefore, the current J in voltage range A2 rtd The tunnel current J RT It is strongly affected by the decrease in voltage range A2. rtd It decreases monotonically until it reaches the Valley.

[0055] The resistance in voltage range A2 can be expressed as -ΔI / ΔV, where ΔV is the voltage change from peak to valley and -ΔI is the current change from peak to valley. As shown in Figure 5, the resistance -ΔI / ΔV is a negative value. In this specification, voltage range A2 is also referred to as the negative resistance region.

[0056] In voltage range A3, the thermionic current J TH The increase in tunnel current J RT This exceeds the decrease. Therefore, in voltage range A3, the current increases monotonically.

[0057] Here, the maximum oscillation frequency of the resonant tunnel diode 10 is proportional to the resistance ΔI / ΔV. Also, the maximum output of the high-frequency device 1 is proportional to the product of the voltage change ΔV and the current change ΔI, ΔV・ΔI. In order to improve the maximum oscillation frequency of the resonant tunnel diode 10 and the maximum output of the high-frequency device 1 (hereinafter also simply referred to as the output of the high-frequency device 1, etc.), it is desirable to increase both the voltage change ΔV and the current change ΔI. In this specification, an increase in the current change ΔI is also referred to as an expansion of the negative resistance region.

[0058] To expand the negative resistance region, the tunnel current J RT It is desirable to increase the thermionic current J. Furthermore, in order to expand the negative resistance region, the thermionic current J is desirable. TH It is desirable to reduce it.

[0059] To expand the negative resistance region, we consider a method for controlling the thickness of the quantum well layer 23. In an ideal resonant tunneling diode 10, reducing the thickness of the well layer 26 allows the tunnel current J to be reduced. RT This can increase the negative resistance region and expand it.

[0060] Furthermore, in an ideal resonant tunneling diode 10, the reactive current can be reduced and the negative resistance region expanded by increasing the thickness of the barrier layer. In this specification, the thermionic current J is defined as follows: TH Currents that increase the current in the valley shown in Figure 5 are called reactive currents.

[0061] However, since the resonant tunneling diode 10 contains nitride semiconductor material, an internal electric field exists. Therefore, when the thickness of the well layer 26 is reduced, the tunnel current J RT Furthermore, reactive current may increase, which can actually reduce the negative resistance region.

[0062] Furthermore, when increasing the thickness of the barrier layer, the tunnel current J increases along with the reactive current. RT In some cases, this can lead to a decrease in the negative resistance region, which may actually shrink.

[0063] Figure 7 is a waveform diagram showing the change in the I-V characteristics of the resonant tunneling diode 10 when the film thickness Tw of the well layer 26 is changed. The horizontal and vertical axes of Figure 7 represent voltage (V) and current (A), respectively, as in Figure 5. Figure 7 shows the I-V curves for film thickness Tw = 2.5 nm, film thickness Tw = 2.75 nm, and film thickness Tw = 3.0 nm. In Figure 7, the lower barrier layer 25 is 1.0 nm in all cases. Similarly, the film thickness of the upper barrier layer 27 is 1.0 nm in all cases.

[0064] As shown in Figure 7, the I-V curve for a film thickness Tw = 2.75 nm has a larger voltage difference ΔV from the peak to the valley and a larger current drop -ΔI than the I-V curve for a film thickness Tw = 3.0 nm. In other words, the negative resistance region can be expanded when the film thickness Tw = 2.75 nm compared to when the film thickness Tw = 3.0 nm.

[0065] On the other hand, in the I-V curve for a film thickness Tw = 2.5 nm, the current in the valley exceeds the current in the peak. Therefore, when the film thickness is 2.5 nm, a negative resistance region is not formed, and the output of the high-frequency device 1 cannot be obtained sufficiently. Note that in the I-V curve for a film thickness of 2.5 nm, the current increases monotonically with increasing voltage, but for convenience, the points where the slope of increase changes significantly are called the peak and the valley.

[0066] In the example shown in Figure 7, the case where the film thickness Tw = 2.75 nm of the well layer 26 is preferred over the cases where the film thickness Tw = 3.0 nm and Tw = 2.5 nm. As described above, in order to expand the negative resistance region, it is necessary to appropriately adjust the film thickness of the well layer 26 and the barrier layer.

[0067] The inventor focused on the correlation between the effect of adjusting the film thickness of the well layer 26 on the current change ΔI, and the effect of adjusting the film thickness of the barrier layer on the current change ΔI. Below, as one method for expanding the negative resistance region, a method for adjusting the film thickness of the well layer 26 and the barrier layer, taking the above correlation into consideration, will be described.

[0068] Figure 8 is a waveform diagram showing the relationship between the film thickness Tw of the well layer 26, the film thickness Tb of the barrier layer, and the current change ΔI. The horizontal axis of Figure 8 represents the film thickness Tw of the well layer 26 (Well thickness [nm]). The vertical axis of Figure 8 represents the current change ΔI ([mA]) between the peak and valley in Figure 5.

[0069] Here, the film thickness T of the quantum well layer 23 can be expressed as T = Tw + 2 × Tb, based on the film thickness Tw of the well layer 26 and the film thickness Tb of the multiple barrier layers (i.e., the lower barrier layer 25 and the upper barrier layer 27).

[0070] Figure 8 shows the relationship between the film thickness Tw of the well layer 26 and the current change ΔI for barrier layer film thicknesses Tb = 2.0 nm, Tb = 1.75 nm, Tb = 1.5 nm, Tb = 1.25 nm, Tb = 1.0 nm, and Tb = 0.75 nm.

[0071] As shown in Figure 8, the peak of the current change ΔI falls within the range satisfying (1) 4 nm ≤ Tw + 2 × Tb ≤ 6 nm.

[0072] In order to expand the negative resistance region, it is desirable that the film thickness Tw of the well layer 26 be set in the range of (2) 0.26 nm ≤ Tw ≤ 4.0 nm. Also, it is desirable that the film thickness Tb of the barrier layer be set in the range of (3) 0.5 nm ≤ Tb ≤ 2.87 nm.

[0073] By setting the film thickness Tw of the well layer 26 and the film thickness Tb of the barrier layer to satisfy the above conditions (1) to (3), the negative resistance region can be expanded. This makes it possible to improve the output of the high-frequency device 1, etc.

[0074] More specifically, when the barrier layer thickness Tb = 2.0 nm, it is estimated that the peak of the current change ΔI is contained within the range of 1.3 nm ≤ Tw ≤ 2.0 nm for the thickness Tw of the well layer 26. When the barrier layer thickness Tb = 1.75 nm, it is estimated that the peak of the current change ΔI is contained within the range of 1.5 nm ≤ Tw ≤ 2.0 nm for the thickness Tw of the well layer 26. When the barrier layer thickness Tb = 1.5 nm, it is estimated that the peak of the current change ΔI is contained near Tw = 2.0 nm (for example, in the range of 1.75 nm ≤ Tw ≤ 2.25 nm) for the thickness Tw of the well layer 26. When the barrier layer thickness Tb = 1.25 nm, it is estimated that the peak of the current change ΔI is contained within the range of 2.1 nm ≤ Tw ≤ 2.6 nm for the thickness Tw of the well layer 26. When the barrier layer thickness Tb = 1.0 nm, it is estimated that the peak of the current change ΔI is located near Tw = 2.75 nm (for example, in the range of 2.5 nm ≤ Tw ≤ 3.0 nm) in the well layer thickness Tw. When the barrier layer thickness Tb = 0.75 nm, it is estimated that the peak of the current change ΔI is located in the range of 3 nm ≤ Tw ≤ 3.8 nm in the well layer thickness Tw.

[0075] The peak of the current change ΔI shown in Figure 8 and the rest of the current change show significant differences in the output of the high-frequency device 1. For example, as shown in Figure 8, the current change ΔI differs by approximately six times between the case where the barrier layer thickness Tb = 1.0 nm and the well layer 26 thickness Tw = approximately 4.0 nm, and the case where the barrier layer thickness Tb = 1.0 nm and the well layer 26 thickness Tw = approximately 2.75 nm. In other words, the maximum oscillation frequency of the resonant tunnel diode 10 and the maximum output of the high-frequency device 1 both differ by approximately six times.

[0076] The resonant tunnel diode 10 has an internal electric field due to spontaneous polarization and piezoelectric polarization. Therefore, the driving voltage of the resonant tunnel diode 10 can be adjusted by adjusting the thickness of the well layer 26. For example, if the thickness of the well layer 26 increases, the driving voltage decreases, and if the thickness of the well layer 26 decreases, the driving voltage increases.

[0077] Figure 8 shows the correlation between the film thickness of multiple well layers 26 and the film thickness of the barrier layer. The inventor expresses this correlation using the above-mentioned conditions (1) to (3). By maintaining this correlation, it is possible to increase or maximize the current change ΔI at any driving voltage.

[0078] Furthermore, the lower barrier layer 25 and the upper barrier layer 27 may contain elements (for example, In) that expand the negative resistance region of the quantum well layer 23. In can expand the negative resistance region, for example, by suppressing reactive current.

[0079] At least a portion of the In may be introduced, for example, as a surfactant in the barrier layer (In surfactant atoms). Furthermore, the inventors have discovered that introducing more In than when In is introduced as a surfactant can further expand the negative resistance region. That is, at least a portion of the In may be introduced into the film inside the interface of the barrier layer. The following describes the concentration of In introduced into the barrier layer.

[0080] Figure 9 is a waveform diagram showing the change in the I-V characteristics of the resonant tunneling diode 10 when the In concentration of the barrier layer is changed. The horizontal and vertical axes of Figure 9 represent voltage (V) and current (A), respectively, as in Figure 5. Figure 9 shows the I-V curves for In concentrations of 1.0 [atomic%], 2.5 [atomic%], and 6.0 [atomic%].

[0081] In this specification, the composition ratio (atomic%) of In to the base material of the barrier layer is also referred to as the In concentration. The base material of the barrier layer includes, for example, at least one of AlN or AlGaN. In the examples shown in Figures 9 and 10, an example in which AlN is used as the base material of the barrier layer is described.

[0082] Figure 10 is a waveform diagram showing the relationship between In concentration and current change ΔI. The horizontal axis of Figure 10 represents In concentration [atomic%]. The vertical axis of Figure 10 represents current change ΔI.

[0083] Figures 9 and 10 show data when the barrier layer thickness Tb = 1.5 nm and the well layer 26 thickness Tw = 2.0 nm.

[0084] As shown in Figure 10, the current change ΔI increases in the following order: when the In concentration is 2.5 [atomic%], 1.0 [atomic%], and 6.0 [atomic%].

[0085] In other words, in the examples shown in Figures 9 and 10, when the In concentration is approximately 2.5 [atomic%], the negative resistance region can be expanded and the output of the high-frequency device 1 can be improved compared to when the In concentration is 1.0 or 6.0 [atomic%].

[0086] Furthermore, as shown in Figure 10, the current change ΔI is larger when the In concentration is 2.5, 1.0, or 6.0 [atomic%] than when the In concentration is 0.0 [atomic%].

[0087] In the resonant tunnel diode 10 according to the embodiment of this disclosure, the output of the high-frequency device 1 can be further improved when the In concentration in the barrier layer is (4) 0.1 [atomic%] or more and less than 10 [atomic%]. That is, in the barrier layer, the In material has a lower concentration than the AlN material. Also, in the example of Figures 9 and 10, the output of the high-frequency device 1 can be further improved when the In concentration is around 2.5 [atomic%].

[0088] The In concentration in the barrier layer can be adjusted (or estimated) by, for example, adjusting (or measuring) the flow rate of the In raw material (e.g., TMI: Trimethylindium) in metal-organic chemical vapor deposition (MOCVD). Alternatively, the In concentration in the barrier layer can be adjusted (or estimated) by adjusting (or measuring) the growth temperature during crystal growth in MOCVD.

[0089] As described above, in the resonant tunneling diode 10 according to the embodiment of this disclosure, the film thickness of the well layer 26 and the film thickness of the barrier layer are adjusted considering a predetermined correlation. Specifically, in the resonant tunneling diode 10, the film thickness of the well layer 26 and the film thickness of the barrier layer are adjusted to satisfy the above conditions (1) to (3).

[0090] In adjusting the film thickness of the well layer 26, the tunnel current J RT While it is possible to adjust the reactive current, adjusting the thickness of the barrier layer can also affect the tunnel current J. RT This can also affect the tunnel current J. Therefore, by adjusting the film thickness of the well layer 26 and the barrier layer, taking into consideration the correlation described above, the increase in reactive current can be suppressed while controlling the tunnel current J. RT This allows for an increase in the negative resistance region (i.e., an increase in the current change ΔI). The increase in the current change ΔI improves the output of the high-frequency device 1.

[0091] Within the range that satisfies the above conditions (1) to (3), the film thickness of the well layer 26 can be arbitrarily adjusted. By adjusting the film thickness of the well layer 26, the driving voltage of the resonant tunnel diode 10 can be adjusted. Therefore, the current change ΔI can be increased over a wide range of driving voltages.

[0092] The barrier layer may contain the element In. The element In may be introduced into the film inside the interface of the barrier layer. When the concentration of In in the barrier layer satisfies the above condition (4), the negative resistance region can be expanded, and the output of the high-frequency device 1 can be further improved.

[0093] In particular, by adjusting the film thickness of the well layer 26 and the barrier layer to satisfy the above conditions (1) to (3), and by adjusting the In concentration of the barrier layer to satisfy the above condition (4), the negative resistance region can be greatly expanded, and the output of the high-frequency device 1 can be greatly improved.

[0094] (Application Examples) The technology disclosed herein can be applied to a variety of products. For example, the technology disclosed herein may be implemented as a device mounted on any type of mobile vehicle, such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility devices, airplanes, drones, ships, robots, construction machinery, or agricultural machinery (tractors).

[0095] Figure 11 is a block diagram showing a schematic configuration example of a vehicle control system 7000, which is an example of a mobile control system to which the technology described herein may be applied. The vehicle control system 7000 comprises a plurality of electronic control units connected via a communication network 7010. In the example shown in Figure 11, the vehicle control system 7000 comprises a drive system control unit 7100, a body system control unit 7200, a battery control unit 7300, an external information detection unit 7400, an internal information detection unit 7500, and an integrated control unit 7600. The communication network 7010 connecting these plurality of control units may be an in-vehicle communication network conforming to any standard such as CAN (Controller Area Network), LIN (Local Interconnect Network), LAN (Local Area Network), or FlexRay®.

[0096] Each control unit comprises a microcomputer that performs calculations according to various programs, a storage unit that stores programs executed by the microcomputer or parameters used in various calculations, and a drive circuit that drives various controlled devices. Each control unit is equipped with a network interface for communication with other control units via the communication network 7010, and a communication interface for communication with devices or sensors inside or outside the vehicle via wired or wireless communication. Figure 11 shows the functional configuration of the integrated control unit 7600, which includes a microcomputer 7610, a general-purpose communication interface 7620, a dedicated communication interface 7630, a positioning unit 7640, a beacon receiver 7650, an in-vehicle equipment interface 7660, an audio / image output unit 7670, an in-vehicle network interface 7680, and a storage unit 7690. Other control units similarly include a microcomputer, a communication interface, and a storage unit.

[0097] The drivetrain control unit 7100 controls the operation of devices related to the vehicle's drivetrain according to various programs. For example, the drivetrain control unit 7100 functions as a control device for generating driving force for the vehicle, such as an internal combustion engine or a drive motor; a driving force transmission mechanism for transmitting driving force to the wheels; a steering mechanism for adjusting the steering angle of the vehicle; and a braking device for generating braking force for the vehicle. The drivetrain control unit 7100 may also function as a control device such as an ABS (Antilock Brake System) or an ESC (Electronic Stability Control).

[0098] A vehicle state detection unit 7110 is connected to the drive system control unit 7100. The vehicle state detection unit 7110 includes, for example, a gyro sensor for detecting the angular velocity of the axial rotation motion of the vehicle body, an acceleration sensor for detecting the acceleration of the vehicle, or at least one of the sensors for detecting the amount of operation of the accelerator pedal, the amount of operation of the brake pedal, the steering angle of the steering wheel, the engine speed, or the rotational speed of the wheels. The drive system control unit 7100 performs calculation processing using the signals input from the vehicle state detection unit 7110 and controls the internal combustion engine, drive motor, electric power steering system, brake system, etc.

[0099] The body system control unit 7200 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 7200 functions as a control device for a keyless entry system, a smart key system, a power window system, or various lamps such as headlights, reverse lights, brake lights, turn signals, or fog lights. In this case, the body system control unit 7200 may receive radio waves transmitted from a portable device that replaces a key or signals from various switches. The body system control unit 7200 receives these radio waves or signals and controls the vehicle's door lock system, power window system, lamps, etc.

[0100] The battery control unit 7300 controls the secondary battery 7310, which is the power source for the drive motor, according to various programs. For example, the battery control unit 7300 receives information such as battery temperature, battery output voltage, or remaining battery capacity from the battery device equipped with the secondary battery 7310. The battery control unit 7300 uses these signals to perform calculations and controls the temperature of the secondary battery 7310 or the cooling device provided in the battery device.

[0101] The external information detection unit 7400 detects information from outside the vehicle equipped with the vehicle control system 7000. For example, at least one of the imaging unit 7410 and the external information detection unit 7420 is connected to the external information detection unit 7400. The imaging unit 7410 includes at least one of the following: a Time of Flight (ToF) camera, a stereo camera, a monocular camera, an infrared camera, and other cameras. The external information detection unit 7420 includes at least one of the following: an environmental sensor for detecting the current weather or climate, or an ambient information detection sensor for detecting other vehicles, obstacles, or pedestrians around the vehicle equipped with the vehicle control system 7000.

[0102] The environmental sensor may be at least one of the following: a raindrop sensor for detecting rain, a fog sensor for detecting fog, a sunshine sensor for detecting the degree of sunlight, and a snow sensor for detecting snowfall. The ambient information detection sensor may be at least one of the following: an ultrasonic sensor, a radar device, and a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) device. These imaging unit 7410 and external information detection unit 7420 may be provided as independent sensors or devices, or as a device in which multiple sensors or devices are integrated.

[0103] Here, Figure 12 shows an example of the installation location of the imaging unit 7410 and the external information detection unit 7420. The imaging units 7910, 7912, 7914, 7916, and 7918 are installed, for example, at least one of the following locations on the vehicle 7900: the front nose, side mirrors, rear bumper, back door, and the upper part of the windshield inside the passenger compartment. The imaging unit 7910 installed on the front nose and the imaging unit 7918 installed on the upper part of the windshield inside the passenger compartment mainly acquire images of the front of the vehicle 7900. The imaging units 7912 and 7914 installed on the side mirrors mainly acquire images of the sides of the vehicle 7900. The imaging unit 7916 installed on the rear bumper or back door mainly acquires images of the rear of the vehicle 7900. The imaging unit 7918 installed on the upper part of the windshield inside the passenger compartment is mainly used for detecting preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, or lanes.

[0104] Figure 12 shows an example of the imaging range of each imaging unit 7910, 7912, 7914, and 7916. Imaging range a shows the imaging range of imaging unit 7910 located on the front nose, imaging ranges b and c show the imaging ranges of imaging units 7912 and 7914 located on the side mirrors, respectively, and imaging range d shows the imaging range of imaging unit 7916 located on the rear bumper or back door. For example, by superimposing the image data captured by imaging units 7910, 7912, 7914, and 7916, an overhead view image of the vehicle 7900 can be obtained.

[0105] The external information detection units 7920, 7922, 7924, 7926, 7928, and 7930, which are installed on the front, rear, sides, corners, and the upper part of the windshield inside the vehicle 7900, may be, for example, ultrasonic sensors or radar devices. The external information detection units 7920, 7926, and 7930, which are installed on the front nose, rear bumper, back door, and the upper part of the windshield inside the vehicle 7900, may be, for example, LIDAR devices. These external information detection units 7920 to 7930 are mainly used for detecting preceding vehicles, pedestrians, or obstacles.

[0106] Returning to Figure 11, the explanation continues. The external information detection unit 7400 causes the imaging unit 7410 to capture images of the area outside the vehicle and receives the captured image data. The external information detection unit 7400 also receives detection information from the connected external information detection unit 7420. If the external information detection unit 7420 is an ultrasonic sensor, radar device, or LIDAR device, the external information detection unit 7400 emits ultrasonic waves or electromagnetic waves and receives information on the received reflected waves. Based on the received information, the external information detection unit 7400 may perform object detection processing such as detecting people, vehicles, obstacles, signs, or characters on the road surface, or distance detection processing. Based on the received information, the external information detection unit 7400 may perform environmental recognition processing to recognize rainfall, fog, or road surface conditions. Based on the received information, the external information detection unit 7400 may calculate the distance to an object outside the vehicle.

[0107] Furthermore, the external information detection unit 7400 may perform image recognition processing or distance detection processing to recognize people, vehicles, obstacles, signs, or characters on the road surface based on the received image data. The external information detection unit 7400 may perform distortion correction or alignment processing on the received image data, and may also synthesize image data captured by different imaging units 7410 to generate an overhead view image or a panoramic image. The external information detection unit 7400 may also perform viewpoint transformation processing using image data captured by different imaging units 7410.

[0108] The in-vehicle information detection unit 7500 detects information inside the vehicle. The in-vehicle information detection unit 7500 is connected to, for example, a driver status detection unit 7510 that detects the driver's state. The driver status detection unit 7510 may include a camera that images the driver, a biosensor that detects the driver's biometric information, or a microphone that collects sounds inside the vehicle. The biosensor is installed, for example, on the seat or steering wheel and detects the biometric information of an occupant sitting in the seat or a driver holding the steering wheel. Based on the detection information input from the driver status detection unit 7510, the in-vehicle information detection unit 7500 may calculate the driver's level of fatigue or concentration, or determine whether the driver is dozing off. The in-vehicle information detection unit 7500 may perform processing such as noise cancellation on the collected audio signals.

[0109] The integrated control unit 7600 controls the overall operation of the vehicle control system 7000 according to various programs. An input unit 7800 is connected to the integrated control unit 7600. The input unit 7800 is implemented by a device that can be operated by the passenger, such as a touch panel, buttons, a microphone, a switch, or a lever. The integrated control unit 7600 may also receive data obtained by voice recognition of voice input from the microphone. The input unit 7800 may be, for example, a remote control device using infrared or other radio waves, or an externally connected device such as a mobile phone or PDA (Personal Digital Assistant) that is compatible with the operation of the vehicle control system 7000. The input unit 7800 may be, for example, a camera, in which case the passenger can input information by gesture. Alternatively, data obtained by detecting the movement of a wearable device worn by the passenger may be input. Furthermore, the input unit 7800 may include, for example, an input control circuit that generates an input signal based on the information input by the passenger using the above input unit 7800 and outputs it to the integrated control unit 7600. Passengers and others can input various data or instruct the vehicle control system 7000 to perform processing operations by operating this input unit 7800.

[0110] The storage unit 7690 may include a ROM (Read Only Memory) for storing various programs executed by a microcomputer, and a RAM (Random Access Memory) for storing various parameters, calculation results, or sensor values. The storage unit 7690 may also be implemented using a magnetic storage device such as an HDD (Hard Disk Drive), a semiconductor storage device, an optical storage device, or a magneto-optical storage device.

[0111] The general-purpose communication interface 7620 is a general-purpose communication interface that mediates communication between the external environment 7750 and various devices present in the external environment 7750. The general-purpose communication interface 7620 may implement cellular communication protocols such as GSM (Global System of Mobile communications), WiMAX (registered trademark), LTE (registered trademark) (Long Term Evolution), or LTE-A (LTE-Advanced), or other wireless communication protocols such as wireless LAN (also known as Wi-Fi (registered trademark)) and Bluetooth (registered trademark). The general-purpose communication interface 7620 may connect, for example, to devices (e.g., application servers or control servers) located on an external network (e.g., the Internet, a cloud network, or a carrier-specific network) via a base station or access point. Furthermore, the general-purpose communication I / F 7620 may connect to terminals located near the vehicle (for example, terminals belonging to the driver, pedestrians, or shops, or MTC (Machine Type Communication) terminals) using, for example, P2P (Peer To Peer) technology.

[0112] The dedicated communication interface 7630 is a communication interface that supports communication protocols developed for use in vehicles. The dedicated communication interface 7630 may implement standard protocols such as WAVE (Wireless Access in Vehicle Environment), DSRC (Dedicated Short Range Communications), or cellular communication protocols, which are combinations of lower-layer IEEE 802.11p and upper-layer IEEE 1609. The dedicated communication interface 7630 typically performs V2X communication, a concept that includes one or more of the following: vehicle-to-vehicle communication, vehicle-to-infrastructure communication, vehicle-to-home communication, and vehicle-to-pedestrian communication.

[0113] The positioning unit 7640 performs positioning by receiving, for example, GNSS (Global Navigation Satellite System) signals from GNSS satellites (for example, GPS signals from GPS (Global Positioning System) satellites) and generates location information including the vehicle's latitude, longitude, and altitude. The positioning unit 7640 may also determine its current location by exchanging signals with a wireless access point, or it may acquire location information from a terminal such as a mobile phone, PHS, or smartphone that has a positioning function.

[0114] The beacon receiver 7650 receives radio waves or electromagnetic waves transmitted from, for example, a radio station installed on a road, and acquires information such as the current location, traffic congestion, road closures, or travel time. The functions of the beacon receiver 7650 may also be included in the dedicated communication interface 7630 described above.

[0115] The in-vehicle equipment interface 7660 is a communication interface that mediates connections between the microcomputer 7610 and various in-vehicle equipment 7760 located inside the vehicle. The in-vehicle equipment interface 7660 may establish a wireless connection using wireless communication protocols such as wireless LAN, Bluetooth®, NFC (Near Field Communication), or WUSB (Wireless USB). Furthermore, the in-vehicle equipment I / F 7660 may establish a wired connection such as USB (Universal Serial Bus), HDMI (High-Definition Multimedia Interface), or MHL (Mobile High-definition Link) via connection terminals (and, if necessary, cables) not shown. The in-vehicle equipment 7760 may include, for example, at least one of the following: a mobile device or wearable device owned by a passenger, or an information device brought into or installed in the vehicle. The in-vehicle equipment 7760 may also include a navigation device that searches for a route to any destination. The in-vehicle equipment I / F 7660 exchanges control signals or data signals with these in-vehicle equipment 7760s.

[0116] The in-vehicle network interface 7680 is an interface that mediates communication between the microcomputer 7610 and the communication network 7010. The in-vehicle network interface 7680 transmits and receives signals and other data in accordance with a predetermined protocol supported by the communication network 7010.

[0117] The microcomputer 7610 of the integrated control unit 7600 controls the vehicle control system 7000 according to various programs based on information acquired via at least one of the general-purpose communication I / F 7620, dedicated communication I / F 7630, positioning unit 7640, beacon receiver 7650, in-vehicle equipment I / F 7660, and in-vehicle network I / F 7680. For example, the microcomputer 7610 may calculate control target values ​​for the drive force generator, steering mechanism, or braking device based on acquired information from inside and outside the vehicle, and output control commands to the drive system control unit 7100. For example, the microcomputer 7610 may perform coordinated control aimed at realizing ADAS (Advanced Driver Assistance System) functions, including vehicle collision avoidance or impact mitigation, following driving based on distance between vehicles, maintaining vehicle speed, vehicle collision warning, or vehicle lane departure warning. Furthermore, the microcomputer 7610 may perform cooperative control for purposes such as autonomous driving, where the vehicle drives autonomously without driver intervention, by controlling the drive force generating device, steering mechanism, or braking device, etc., based on the acquired information about the vehicle's surroundings.

[0118] The microcomputer 7610 may generate three-dimensional distance information between the vehicle and surrounding structures, people, and other objects based on information acquired via at least one of the general-purpose communication I / F 7620, dedicated communication I / F 7630, positioning unit 7640, beacon receiver 7650, in-vehicle equipment I / F 7660, and in-vehicle network I / F 7680, and create local map information including surrounding information of the vehicle's current location. The microcomputer 7610 may also predict dangers such as vehicle collision, proximity of pedestrians, or entry into a closed road based on the acquired information, and generate a warning signal. The warning signal may be, for example, a signal to generate a warning sound or to illuminate a warning lamp.

[0119] The audio-image output unit 7670 transmits at least one of audio and image output signals to an output device capable of visually or audibly notifying the vehicle's occupants or those outside the vehicle. In the example in Figure 11, the output devices are exemplified as an audio speaker 7710, a display unit 7720, and an instrument panel 7730. The display unit 7720 may include, for example, at least one of an onboard display and a head-up display. The display unit 7720 may also have an AR (Augmented Reality) display function. The output device may be other devices besides these, such as headphones, wearable devices such as glasses-type displays worn by occupants, projectors, or lamps. If the output device is a display device, the display device visually displays the results obtained from various processes performed by the microcomputer 7610 or information received from other control units in various formats such as text, images, tables, and graphs. If the output device is an audio output device, the audio output device converts the audio signal, consisting of reproduced audio data or sound data, into an analog signal and outputs it audibly.

[0120] In the example shown in Figure 11, at least two control units connected via the communication network 7010 may be integrated into a single control unit. Alternatively, each control unit may be composed of multiple control units. Furthermore, the vehicle control system 7000 may include other control units not shown. Also, in the above description, some or all of the functions performed by one control unit may be assigned to other control units. In other words, as long as information is transmitted and received via the communication network 7010, predetermined calculation processing may be performed by any of the control units. Similarly, a sensor or device connected to one control unit may be connected to another control unit, and multiple control units may transmit and receive detection information to and from each other via the communication network 7010.

[0121] In the vehicle control system 7000 described above, the high-frequency device 1 according to this embodiment, as described with reference to Figure 1, can be applied to the general-purpose communication interface 7620 or dedicated communication interface 7630, etc., as shown in the application example in Figure 11. By applying the high-frequency device 1 of Figure 1, the general-purpose communication interface 7620 or dedicated communication interface 7630 can be realized as a compact and high-output communication device.

[0122] The technology can take the following configurations: (1) A resonant tunneling diode comprising: a first electrode layer disposed on a support substrate containing a nitride semiconductor material; a quantum well layer disposed on the first electrode layer; a second electrode layer disposed on the quantum well layer; a first semiconductor layer disposed within the quantum well layer; and a plurality of second semiconductor layers disposed so as to sandwich the first semiconductor layer and having a larger band gap than the first semiconductor layer, wherein the thickness Tw of the first semiconductor layer and the thickness Tb of the second semiconductor layer satisfy 4 nm ≤ Tw + 2 × Tb ≤ 6 nm, and the second semiconductor layer contains an element that expands the negative resistance region formed in the quantum well layer. (2) The resonant tunneling diode according to (1), wherein the element is indium (In). (3) The resonant tunneling diode according to (1) or (2), wherein the composition ratio of the element to the base material of the second semiconductor layer is 0.1% or more and less than 10%. (4) The resonant tunnel diode according to (3), wherein the first semiconductor layer comprises gallium (Ga) and nitrogen (N), and the base material of the second semiconductor layer comprises aluminum (Al) and nitrogen (N). (5) The resonant tunnel diode according to (4), wherein the first semiconductor layer comprises GaN, and the base material of the second semiconductor layer comprises at least one of AlN or AlGaN. (6) The resonant tunnel diode according to any one of (1) to (5), wherein Tw satisfies 0.26 nm ≤ Tw ≤ 4.0 nm. (7) The resonant tunnel diode according to any one of (1) to (6), wherein Tb satisfies 0.5 nm ≤ Tb ≤ 2.87 nm. (8) A resonant tunneling diode according to any one of (1) to (7), further comprising a plurality of spacer layers, wherein the plurality of second semiconductor layers include a third semiconductor layer disposed between the first semiconductor layer and the first electrode layer and a fourth semiconductor layer disposed between the first semiconductor layer and the second electrode layer, and the plurality of spacer layers include a first spacer layer disposed between the first semiconductor layer and the third semiconductor layer and a second spacer layer disposed between the first semiconductor layer and the fourth semiconductor layer.(9) A resonant tunnel diode according to any one of (1) to (8), wherein Tb and Tw satisfy any of the following: Tb = 2.0 nm and 1.3 nm ≤ Tw ≤ 2.0 nm, Tb = 1.75 nm and 1.5 nm ≤ Tw ≤ 2.0 nm, Tb = 1.5 nm and 1.75 nm ≤ Tw ≤ 2.25 nm, Tb = 1.25 nm and 2.1 nm ≤ Tw ≤ 2.6 nm, Tb = 1.0 nm and 2.5 nm ≤ Tw ≤ 3.0 nm, or Tb = 0.75 nm and 3 nm ≤ Tw ≤ 3.8 nm. (10) A high-frequency device comprising a resonant tunnel diode according to any one of (1) to (9), and an antenna connected in parallel between the resonant tunnel diode and a reference voltage node, having a capacitor and an inductor that resonate at a specific frequency.

[0123] The aspects of this disclosure are not limited to the individual embodiments described above, but include various modifications that a person skilled in the art could conceive, and the effects of this disclosure are not limited to those described above. In other words, various additions, modifications, and partial deletions are possible, as long as they do not depart from the conceptual idea and spirit of this disclosure derived from the claims and their equivalents.

[0124] 1. High-frequency device, 2. Emitter electrode, 3. Collector electrode, 4. Dielectric, 5. Power supply circuit, 6. Filter section, 7. Power supply section, 8. Slot section, 10. Resonant tunnel diode, 11. Emitter layer, 12. Collector layer, 13. Support substrate, 20. Antenna, 21. Resonator, 22. Lower spacer layer, 23. Quantum well layer, 24. Upper spacer layer, 25. Lower barrier layer, 26. Well layer, 27. Upper barrier layer

Claims

1. A resonant tunneling diode comprising: a first electrode layer disposed on a support substrate containing a nitride semiconductor material; a quantum well layer disposed on the first electrode layer; a second electrode layer disposed on the quantum well layer; a first semiconductor layer disposed within the quantum well layer; and a plurality of second semiconductor layers disposed so as to sandwich the first semiconductor layer and having a larger band gap than the first semiconductor layer, wherein the thickness Tw of the first semiconductor layer and the thickness Tb of the second semiconductor layer satisfy 4 nm ≤ Tw + 2 × Tb ≤ 6 nm, and the second semiconductor layer contains an element that expands the negative resistance region formed in the quantum well layer.

2. The resonant tunneling diode according to claim 1, wherein the element is indium (In).

3. The resonant tunneling diode according to claim 1, wherein the composition ratio of the element to the base material of the second semiconductor layer is 0.1% or more and less than 10%.

4. The resonant tunnel diode according to claim 3, wherein the first semiconductor layer comprises gallium (Ga) and nitrogen (N), and the base material of the second semiconductor layer comprises aluminum (Al) and nitrogen (N).

5. The resonant tunneling diode according to claim 4, wherein the first semiconductor layer comprises GaN, and the base material of the second semiconductor layer comprises at least one of AlN or AlGaN.

6. The resonant tunneling diode according to claim 1, wherein Tw satisfies 0.26 nm ≤ Tw ≤ 4.0 nm.

7. The resonant tunneling diode according to claim 1, wherein Tb satisfies 0.5 nm ≤ Tb ≤ 2.87 nm.

8. The resonant tunneling diode according to claim 1, further comprising a plurality of spacer layers, wherein the plurality of second semiconductor layers include a third semiconductor layer disposed between the first semiconductor layer and the first electrode layer, and a fourth semiconductor layer disposed between the first semiconductor layer and the second electrode layer, and the plurality of spacer layers include a first spacer layer disposed between the first semiconductor layer and the third semiconductor layer, and a second spacer layer disposed between the first semiconductor layer and the fourth semiconductor layer.

9. The resonant tunneling diode according to claim 1, wherein Tb and Tw satisfy any of the following: Tb = 2.0 nm and 1.3 nm ≤ Tw ≤ 2.0 nm, Tb = 1.75 nm and 1.5 nm ≤ Tw ≤ 2.0 nm, Tb = 1.5 nm and 1.75 nm ≤ Tw ≤ 2.25 nm, Tb = 1.25 nm and 2.1 nm ≤ Tw ≤ 2.6 nm, Tb = 1.0 nm and 2.5 nm ≤ Tw ≤ 3.0 nm, or Tb = 0.75 nm and 3 nm ≤ Tw ≤ 3.8 nm.

10. A high-frequency device comprising: a resonant tunneling diode according to claim 1; and an antenna connected in parallel between the resonant tunneling diode and a reference voltage node, having a capacitor and an inductor that resonate at a specific frequency.

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