Resistive Cutoff Frequency Research Articles

Theoretical analysis of AlGaN/GaN resonant tunnelling diodes with step heterojunctions spacer and sub-quantum well

In this paper, we proposed to use step heterojunctions emitter spacer (SHES) and InGaN sub-quantum well in AlGaN/GaN/AlGaN double barrier resonant tunnelling diodes (RTDs). Theoretical analysis of RTD with SHES and InGaN sub-quantum well was presented, which indicated that the negative differential resistance (NDR) characteristic was improved. And the simulation results, peak current density JP=82.67 mA/μm2, the peak-to-valley current ratio PVCR=3.38, and intrinsic negative differential resistance RN=-0.147Ω at room temperature, verified the improvement of NDR characteristic brought about by SHES and InGaN sub-quantum well. Both the theoretical analysis and simulation results showed that the device performance, especially the average oscillator output power presented great improvement and reached 2.77mW/μm2 magnitude. And the resistive cut-off frequency would benefit a lot from the relatively small RN as well. Our works provide an important alternative to the current approaches in designing new structure GaN based RTD for practical high frequency and high power applications.

Humidity sensing and resonant tunneling properties of indium nitride p-n device

Indium nitride (InN) and indium nitride compound doped oxygen element (InN:O) compounds are grown for application in sensing devices along with the function of microwave properties. The peak-to-valley current ratio (PVCR) of InN/InNO/In/SiO2/Si (III-S) p-n sensing device reached 2.6. The peak current density and peak voltage of the III-S device were as high as 3.67kA/cm2 and 2.2V, respectively. The sensing periods were 580s and 600s for the adsorption and desorption processes, respectively. The sensing sensitivities at a low RH% from 40% to 70% and at a high RH% from 70% to 90% were 8.3mΩ/RH% and 7.5mΩ/RH%, respectively. The resistive cutoff frequency of an III-S device reached 28GHz at an RH of 40%. The sensitivity of frequency measurement for an III-S device for relative humidity was 1.7kHz/RH%.

Humidity Sensor of p-n InN/Si Nanostructure With GHz Resonant Microwave Property

As the growth temperature, annealing temperature, and annealing time of InN sensing film of InN/InNO/In2O3/In/SiO2/Si humidity sensor were, respectively, adjusted at 400 °C, 400 °C, and 15 min, the sensing surface possesses obvious particles of nanometer scale. The particle size of InN sensing film was estimated about 65 nm which realized the quantum effect of InN sensing film for the humidity sensing performance in chemistry. The designed p-n InN/InNO/In2O3/In/SiO2/Si structures of humidity sensor in this paper contained three different buffer layers (indium layer, InNO layer, and In2O3 layer) which also revealed the negative differential resistance effect with peak current density of 2.8 kA/cm $^ {2}$ and peak-to-valley current ratio of 1.93 for quantum resonant microwave performance in physics. The periods of water molecular adsorption and desorption are $\sim 600$ and 580 s, respectively. The sensing resolution of adsorption and desorption is defined by resistance variation per second. The response sensitivity ( $S_{{\it {R}}})$ of adsorption and desorption are $\sim 0.25~\text{m}\Omega $ /s (0.1 %RH/s) and 0.41 $\text{m}\Omega $ /s (0.1 %RH/s), respectively. The InN/InNO/In2O3/In/SiO2/Si humidity sensor revealed the sensing sensitivity of $6 \times 10^{{ {-3}}}$ ohm/% RH. The InN/InNO/In2O3/In/SiO2/Si humidity sensor also revealed the resistive cutoff frequency ( $f_{r})$ and the self-resonant frequency ( $f_{\rm {SR}})$ of microwave device reached as 1.6 MHz and 70 GHz, respectively. Microwave transmission property of p-n InN/InNO/In2O3/In/SiO2/Si humidity sensor reached as gigahertz frequency range can transfer the humidity signal from patient to monitoring station via high frequency wireless communication from one device. InN/InNO/In2O3/In/SiO2/Si humidity sensor can be, therefore, applied in wireless microwave transmission of human body sensing signal.

Influence of tunneling barrier width on the forward current characteristics of InAs-based microwave p–n diode

InAs-based p–n interband tunneling bi-barrier resonant microwave (ITE BBRM) devices were successfully fabricated by using the molecular beam epitaxial (MBE) method in this research. The influence of a central barrier thickness from 10Å to 40Å on electrical characteristics of BBRM devices was investigated by using theoretical analysis and experimental evidence. Tunneling current densities (JT) of BBRM devices were simulated in accordance with the consideration of a narrowing bandgap (NBG) effect caused by the heavy concentration doped (HCD) effect. The peak-to-valley current ratio (PVCR) value and output current density reached as high as 383 and 0.226kA/cm2 in practice, respectively, when the central barrier thickness was 10Å thick. When an InAs-based p–n BBRM device produces a resonant phenomenon, the resonant operation voltage of the device is as low as 2.03V in our experimental study. Experimental results of the tunneling current density are matched to the calculating results of device from the calculation of quantum energy levels. The thinner the tunneling barrier thickness between the double quantum wells, the more the tunneling current density, which is attributed to the larger transmittance coefficient. In this study, an increase in the central barrier thickness increased the resistive cutoff frequency (fr), which the frequency reached GHz indicating that the ITE BBRM device became a microwave resonant device.

Indium nitride humidity sensing devices with microwave resonant property

An effective microstructure indium nitride (InN) humidity sensing (INHUSE) device has been developed after InN compound was appropriately annealed with nitrogen source compensation. An X-ray diffraction spectrum of the as-synthesised structure shows one strong peak at 30.5° corresponding to the (0002) atomic plane of the InN hexagonal compound. The InN compound of p-type is exhibited to reach an average Hall coefficient of 2.270 × 107 m2/C, which can be conjugated with the n-type substrate to construct the p–n sensing device with a resonant tunnelling property. The Raman spectrum reveals the longitudinal optical phonon mode A1(LO) (polar mode), transverse optical phonon mode A1(TO) (polar mode) and transverse optical phonon mode E1(TO) of the InN-based INHUSE device in 582, 437 and 473 cm−1, respectively. The negative differential resistance effect of the INHUSE device with an excellent peak current density in 13.2 kA/cm2 and an outstanding peak to valley current ratio of about 3.36 is exhibited. Experimental moisture examination of the INHUSE device from RH30 to 90% in accordance with the calculation of the microwave resonant property up to GHz is completed. The linear region of relative humidity measurement is from RH40 to 70% in resistance value, reached as the measured resistance value at about 31 Ω. The sensitivity of the INHUSE device is about 50 kHz/RH% for the self-resonant frequency and 2.5 MHz/RH% for the resistive cutoff frequency.

Si/SiGe resonant interband tunnel diode with f/sub r0/ 20.2 GHz and peak current density 218 kA/cm/sup 2/ for K-band mixed-signal applications

This letter presents the room-temperature high-frequency operation of Si/SiGe-based resonant interband tunnel diodes that were fabricated by low-temperature molecular beam epitaxy. The resulting devices show a resistive cutoff frequency f/sub r0/ of 20.2 GHz with a peak current density of 218 kA/cm/sup 2/, a speed index of 35.9 mV/ps, and a peak-to-valley current ratio of 1.47. A specific contact resistivity of 5.3/spl times/10/sup -7/ /spl Omega//spl middot/cm/sup 2/ extracted from RF measurements was achieved by Ni silicidation through a P /spl delta/-doped quantum well by rapid thermal sintering at 430/spl deg/C for 30 s. The resulting devices are very good candidates for RF high-power mixed-signal applications. The device structures presented here are compatible with a standard complementary metal-oxide-semiconductor or heterojunction bipolar transistor process.

RF Performance and Modeling of Si/SiGe Resonant Interband Tunneling Diodes

The RF performance of two different Si-based resonant interband tunneling diodes (RITD) grown by low-temperature molecular beam epitaxy (LT-MBE) were studied. An RITD with an active region of B /spl delta/-doping plane/2 nm i-Si/sub 0.5/Ge/sub 0.5//1 nm i-Si/P /spl delta/-doping plane yielded a peak-to-valley current ratio (PVCR) of 1.14, resistive cutoff frequency (f/sub r0/) of 5.6 GHz, and a speed index of 23.3 mV/ps after rapid thermal annealing at 650/spl deg/C for 1 min. To the authors' knowledge, these are the highest reported values for any epitaxially grown Si-based tunnel diode. Another RITD design with an active region of 1 nm p+ Si/sub 0.6/Ge/sub 0.4//B /spl delta/-doping plane/4-nm iSi/sub 0.6/Ge/sub 0.4//2 nm i-Si/P /spl delta/-doping plane and annealed at 825/spl deg/C for 1 min had a PVCR of 2.9, an f/sub r0/ of 0.4 GHz, and a speed index of 0.2 mV/ps. A small signal model was established to fit the measured S/sub 11/ data for both device designs. Approaches to increase f/sub r0/ are suggested based on the comparison between these two diodes. The two devices exhibit substantially different junction capacitance/bias relationships, which may suggest the confined states in the /spl delta/-doped quantum well are preserved after annealing at lower temperatures but are reduced at higher temperature annealing. A comprehensive dc/RF semi-physical model was developed and implemented in Agilent advanced design system (ADS) software. Instabilities in the negative differential resistance (NDR) region during dc measurements were then simulated.

Temperature dependent DC/RF performance of Si/SiGe resonant interband tunnelling diodes

The temperature dependent DC/RF performance of Si-based resonant interband tunnelling diodes (RITDs) grown by low temperature molecular beam epitaxy was studied. Both DC and RF performance were measured at various temperatures from 20 to 150°C. At 20°C, the RITD exhibits a peak current density ( Jp) of 22 kA/cm2 with peak-to-valley current ratio (PVCR) of 2.0. The maximum resistive cutoff frequency (fr0) of 2.4 GHz was obtained by biasing the diode at 320 mV. Increasing temperature slightly degrades the PVCR and fr0. At 150°C, the PVCR and fr0 reduced to 1.8 and 1.9 GHz, respectively. The observed weak temperature dependence of the DC/RF performance and the GHz operating frequency make Si/SiGe RITDs a good candidate for high power microwave applications.

A physics based model for the RTD quantum capacitance

A simple derivation of the form for the compact model of the quantum capacitance in a resonant tunneling diode (RTD) is presented. The quantum capacitance is shown to reduce the resistive cutoff frequency. The implementation of the model into SPICE is described. The distorting effect of the strongly nonlinear quantum capacitance on an oscillator circuit is demonstrated in a SPICE simulation. The nonlinearity becomes important for the highest frequency applications when the RTD capacitance is comparable to the capacitance in the rest of the circuit.

Hall Magnetocapacitance in Two-Dimensional Electron Systems

The magnetocapacitance of a two-dimensional electron system (2DES) is investigated experimentally, both under and away from Quantum Hall (QH) conditions, at frequencies between 1 kHz and 100 MHz. The nature of the capacitive signal in a bounded 2DES is determined by a resistive cut-off frequency 1/$\tau \propto \sigma_{xx}$, the longitudinal magnetoconductivity. A new response mechanism is reported for angular frequencies $\omega > 1/\tau$, which is controlled by the $\em transverse$ or Hall conductivity $\sigma_{xy}$ and the boundaries of the sample, even at frequencies far below those of the Edge Magnetoplasma resonances and away from the QH-conditions.

Experimental study of the frequency limits of a resonant tunneling oscillator

An equivalent circuit obtained from microwave impedance and power data is proposed for a resonant tunneling diode. The four-element circuit consists of a series R and C in parallel with a nonlinear negative differential conductance −G, the combination in turn in series with a resistor r. The resistive cut-off frequency predicted by this model depends on both the RC and RG products. Detection at THz frequencies is also explained by the model.

High frequency amplification in quantum well oscillators

We have calculated the frequency limit of negative differential resistance and a.c. amplification of quantum well oscillators. From the time development of resonant tunneling, negative resistance is expected to occur at very high frequencies. However, the large device impedance results in a resistive cut-off frequency that is several orders of magnitude below that predicted from transit time considerations. This cut-off frequency is estimated from an equivalent circuit model, and the power of an oscillator as a function of frequency and negative resistance is found from a transmission line model.

Precision microwave measurement of the internal parasitics of tunnel-diodes

This paper reports the results of precision microwave standing-wave measurements using a superheterodyne technique from 4 to 11 GHz on the internal parasitics of tunnel-diodes terminating a coaxial-line. Because of past conflicting conjectures as to the frequency dependence of the series resistance, particular attention has been paid to its accurate evaluation. Errors due to transmission-line attenuation and mount discontinuities have been explicitly eliminated from the measured results. The frequency invariance of the series inductance and junction capacitance is verified; but a new variation of series resistance with frequency is proposed of the form <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r=T_{dc}+(af)^{2}</tex> , in accordance with the experimental results. The effect of this variation on the resistive cutoff frequency is discussed and a comparison is made With the relevant results of other researchers.

On "Operation of tunnel diodes above their resistive cutoff frequency"

Tunnel diodes have been made to operate above their resistive cutoff frequency by mounting them in tapered waveguides. The output is apparently due to harmonics of a lower frequency oscillation. The fundamental frequency was detected by means of a probe placed close to the diode. Examination of the diode's equivalent circuit indicates that it is unlikely that oscillations can occur above the resistive cutoff frequency.

Characterisation of tunnel diodes at microwave frequencies

Microwave characteristics of coaxial-mounted tunnel diodes are investigated. Measured immittance data are used to deduce the equivalent-circuit parameters of the diode without recourse to d.c. or low-frequency measurements. The results indicate that the series-resistance component is frequency dependent, while the rest of the parameters in the circuit are frequency invariant. The phenomenological cause of this observed variation is attributable to the microwave absorption within the narrow p-n junction. An important consequence is that the true resistive cut-off frequency of a tunnel diode is lower than the value suggested by the low-frequency equivalent-circuit parameters.

Operation of tunnel diodes above their resistive cutoff frequency

Tunnel diodes have been made to operate above their resistive cutoff frequency by mounting them in tapered waveguides. The output is apparently due to harmonics of a lower frequency oscillation. The fundamental frequency was detected by means of a probe placed close to the diode. Examination of the diode's equivalent circuit indicates that it is unlikely that oscillations can occur above the resistive cutoff frequency.

Above cutoff frequency circuit principles for microwave tunnel diode oscillators

The principle of possible operation of a tunnel diode above its classically accepted resistive cutoff frequency is presented. This principle requires a new interpretation of the tunnel diode mounting and equivalent circuit. The theoretical analysis indicates that, if the tunnel diode is operated in the series circuit mode, the diode cannot be operated above its classical resistive cutoff frequency; but, if the same diode is operated in the parallel circuit mode, the diode can be operated far above its classical resistive cutoff frequency. Millimeter-wave operation of a microwave tunnel diode is given as an example. When the tunnel diode is operated in the parallel circuit mode, a new cutoff frequency appears. This is the conductive lower cutoff frequency. Below the conductive lower cutoff frequency and within certain forbidden frequency bands, the tunnel diode is in-operative in the parallel circuit mode. A method of operating the tunnel diode in the parallel circuit mode is given. Equations for the new cutoff frequency and the forbidden frequency bands are derived. The tunnel diode can be operated in the parallel circuit mode at an extremely high frequency and can be operated in the series circuit mode at a relatively low frequency.

5-10 Ghz YIG-tuned tunnel-diode oscillator

A previously reported YIG-tuned tunnel diode oscillator was limited in its upper frequency of oscillation by the resonance of the diode capacitance with the inductance of the YIG coupling loop. The oscillator described here was designed to operate above this resonance, which is one of the causes of the curvature at the low frequency end of the tuning curve. The tunnel diode used is a Microwave Associates MA 4655 Gallium-Arsenide diode, having an operating (large signal) self-resonance at 10.3 GHz. It has a peak current of 25 mA and a resistive cutoff frequency of 25 GHz. The YIG sphere has a diameter of 0.040 inch and a saturation magnetization of 1750 gauss. It was oriented with one of the easy axes parallel to the applied magnetic field. The magnetic field was varied from 1120 to 3360 gauss in order to tune the oscillator from 5.1 to 10.2 GHz.

Operation of the tunnel diode above resistive cutoff frequency

Operation of the tunnel diode above resistive cutoff frequency

Operation of the tunnel diode above the resistive cutoff frequency

Operation of the tunnel diode above the resistive cutoff frequency