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This article presents a novel, on-wafer deembedding technique for the accurate small-signal equivalent circuit modeling of resonant tunneling diodes (RTDs). The approach is applicable to stabilized RTDs, and so enables the modeling of the negative differential resistance (NDR) region of the device's current-voltage (I-V) characteristics. Furthermore, a novel quasi-analytical procedure to determine all the equivalent circuit elements from the deembedded S-parameter data is developed. Extraction results of a 10 μm x 10 μm stabilized, low-current density RTD at different bias points show excellent fits between modeled and measured S-parameters up to 110 GHz.

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... To increase the RTD power, it was suggested to design a large-scale 2D array of RTD coupled to an emitting antenna. 15 For efficient coupling of RTD to external RFcircuitry, it is necessary to develop experimentally 16 or theoretically 17 an equivalent schematic diagram of RTD. One of the experimental approaches is based on measuring the complex S11-parameters (the reflection coefficients) in a wide frequency range and fitting ReðS 11 Þ and ImðS 11 Þ curves by a simple theory based on a lumped elements network. ...

... One of the experimental approaches is based on measuring the complex S11-parameters (the reflection coefficients) in a wide frequency range and fitting ReðS 11 Þ and ImðS 11 Þ curves by a simple theory based on a lumped elements network. 16 In this work, to evaluate the potential of operation distributed RTDs as an active microstrip transmission line (MTL), we use experimentally extracted parameters of the lumped equivalent network to define amplification conditions in a such THz generator. ...

... Recently, we have investigated the operation of fabricated RTDs biased into self-oscillation regime. 16 Here, we use a small signal equivalent RF-network [see in Fig. 2(b)] for fabricated RTDs. The equivalent network contains quantum inductance L q connected in series with the differential resistance R d . ...

We describe a method of parameters extraction for the lumped element network representing resonant tunneling diodes (RTDs). The method is based on onchip reflection coefficient measurements in a wide frequency range from 1 kHz up to 60 GHz in combination
with differential resistance measurements. We have proposed and fabricated double-barrier GaAs/AlAs RTDs embedded into the 50-Ohm coplanar transmission line section, suitable for onchip RF-measurements using a probe station and a vector network analyzer. A good agreement between the experimental S11-parameter curves and the curves calculated from the equivalent lumped network is obtained for various RTD bias voltages. A possible operation
of a distributed RTDs as an active microstrip transmission line (MTL) is also discussed. Experimentally extracted parameters of the lumped equivalent network are used to define amplification
conditions in MTLs based on distributed RTDs.

... The inclusion of scattering processes is also useful for the accurate determination of the intrinsic cutoff frequency of the RTD, as the electron lifetime in the quantum well depends on the strength of the scattering mechanisms connecting the localized states in the quantum well with the delocalized current-carrying states in the emitter and collector regions. The frequency dependence of the real and imaginary parts of the small-signal impedance in the PDR and NDR regions are reported in Fig. 7. Our results are in qualitative agreement with time-dependent quantum Monte Carlo calculations based on Bohmian trajectories [60], and equivalent circuit models obtained from scattering parameter measurements [61]. The small-signal conductance equals the differential conductance in the low-frequency 064020-9 limit, while in the high-frequency limit, the capacitance approaches the geometrical capacitance. ...

Emerging applications in the field of finite-frequency mesoscopic physics require accurate modeling tools for the evaluation of carrier-transport dynamics, modulation bandwidth, and frequency conversion effects in nanodevices. With foundations in advanced concepts of many-body and quantum field theories, the nonequilibrium Green’s function technique is widely adopted in the calculation of steady-state carrier-transport properties of nanostrucures, while the evaluation of the frequency response is so far largely unexplored by genuine quantum models. Guided by the connection with drift-diffusion solvers within a local description of carrier-phonon scattering, we propose an accurate, yet computationally efficient nonequilibrium Green’s function model of dissipative carrier transport to study the small-signal properties of semiconductor nanostructures. From the numerical evaluation of steady-state Green’s functions and their functional derivatives, we compute spectrally resolved observables expressed in terms of familiar microscopic quantities germane to the drift-diffusion framework, the most prevalent tool in semiclassical device simulation. Besides drastically improving the convergence properties, the exact Jacobian, complemented with the contribution of the displacement current, gives access to the small-signal admittance. Current-conserving boundary conditions suitable for small-signal analysis provide the correct physical behavior near the contacts. Numerical examples show the accuracy and flexibility of the proposed model.

... The development of AC models is beyond the scope of the present paper but a intrinsic small-signal AC model can be constructed as a first-order (linear) approximation of our DC characteristic curve as a function of the bias point. Specifically regarding RTDs, a very good discussion can be found in a recent work [44]. It is shown that the main small-signal elements of the AC equivalent circuit can be obtained from the I-V curves and geometrical parameters. ...

In this paper, we develop an analytical model for the resonant current-voltage (
I–V)
characteristics of 2D-2D Resonant Tunneling Diodes. Starting from the Tsu-Esaki formalism, we consider the overall electrical potential distribution in the device layer structure, including the quantized space charge region in the emitter layer. Additionally, to obtain a more realistic model, we also take into account the scattering experienced by electrons during tunneling process through the double barrier region. These additional features greatly improve the accuracy of the proposed model when compared with others approaches reported in the literature. The device model is fully physics-based, allowing the computation of the
I-V
curve accordingly to the geometry and device structure of the RTD. The model is fully analytical and explicit, thereby well suited for circuit simulator environment. The model is validated against experimental data from distinct RTDs structures, providing excellent agreement.

... The complete device circuit, shown in Figure 5, is completed by the extrinsic elements Cp and Lp, which model the parasitic components introduced by the metallic bond-pads [7]. In order to accurately determine the equivalent circuit elements of the fabricated devices, the acquired S-parameter data was first converted to Z-parameters and fitted using the proposed model over the entire frequency range using a direct optimization procedure [8]. Good agreement between measurement and simulation was obtained across the entire bias range and up to 110 GHz for 500 nm nano RTD device compared with 3 µm RTD as illustrated by the graphs in Figure 6 for one bias point (0.65V) in NDR region. ...

In this paper, we report on the fabrication of micrometre and nanometre-sized resonant tunnelling diode (RTD) devices which may be used as excitable neuromorphic spike generators. The fabrication processes using photolithography were applied for micro-sized RTDs, while for nano-RTDs the fabrication was optimised to achieve accurate nano-sized mesas through a multi-exposure step based on e-beam lithography. The results show a large decrease in the peak currents from 41 mA to 27 A for micro- and nano-RTDs, respectively, peak and valley voltages of around 0.6 V and 0.8 V and a peak to valley current ratio of around 2.4. For the smallest fabricated RTD of 300 nm diameter, the expected energy consumption per oscillation cycle (if used in an oscillator) will be 1.55 fJ. DC characterisation of the devices show that the nano-RTDs are stable and have smooth current voltage (I-V) characteristics compared with micro-RTDs. The nano-RTD technology could be employed to realise highly sensitive photodetectors that can be operated as spike generators and so they could underpin the development of energy efficient neuromorphic computing.

... Notably, the total dissipated energy of our nanocircuit diode, E CV 2 , can be extremely low. As an example, for the case of a 2 μm 2 device resonant tunneling-based microLED device (assuming a 2.8 fF/μm 2 for QRT devices [75] and a 2 V operation), the estimated dissipated energy is ∼22 fJ. Lastly, we assume a 3-dB cutoff frequency, f 3dB , approximately set by the refractory time, ...

Event-activated biological-inspired subwavelength (sub- λ ) photonic neural networks are of key importance for future energy-efficient and high-bandwidth artificial intelligence systems. However, a miniaturized light-emitting nanosource for spike-based operation of interest for neuromorphic optical computing is still lacking. In this work, we propose and theoretically analyze a novel nanoscale nanophotonic neuron circuit. It is formed by a quantum resonant tunneling (QRT) nanostructure monolithic integrated into a sub- λ metal-cavity nanolight-emitting diode (nanoLED). The resulting optical nanosource displays a negative differential conductance which controls the all-or-nothing optical spiking response of the nanoLED. Here we demonstrate efficient activation of the spiking response via high-speed nonlinear electrical modulation of the nanoLED. A model that combines the dynamical equations of the circuit which considers the nonlinear voltage-controlled current characteristic, and rate equations that takes into account the Purcell enhancement of the spontaneous emission, is used to provide a theoretical framework to investigate the optical spiking dynamic properties of the neuromorphic nanoLED. We show inhibitory- and excitatory-like optical spikes at multi-gigahertz speeds can be achieved upon receiving exceptionally low (sub-10 mV) synaptic-like electrical activation signals, lower than biological voltages of 100 mV, and with remarkably low energy consumption, in the range of 10–100 fJ per emitted spike. Importantly, the energy per spike is roughly constant and almost independent of the incoming modulating frequency signal, which is markedly different from conventional current modulation schemes. This method of spike generation in neuromorphic nanoLED devices paves the way for sub- λ incoherent neural elements for fast and efficient asynchronous neural computation in photonic spiking neural networks.

We develop in this work a qualitative quantum electron transport model, in the strong light-matter coupling regime under dipole approximation, able to capture polaritonic signatures in the time-dependent electrical current. The effect of the quantized electromagnetic field in the displacement current of a resonant tunneling diode inside an optical cavity is analyzed. The original peaks of the bare electron transmission coefficient split into two new peaks due to the resonant electron-photon interaction, leading to coherent Rabi oscillations among the polaritonic states that are developed in the system in the strong coupling regime. This mimics known effects predicted by a Jaynes-Cummings model in closed systems and shows how a full quantum treatment of electrons and electromagnetic fields may open interesting paths for engineering new THz electron devices. The computational burden involved in the multi-time measurements of THz currents is tackled by invoking a Bohmian description of the light-matter interaction. We also show that the traditional static transmission coefficient used to characterize DC quantum electron devices has to be substituted by a new displacement current coefficient in high-frequency AC scenarios.

We report about an In0.53Ga0.47As/AlAs double-barrier resonant tunnelling diode (RTD) epitaxial structure that features high-power capabilities at low-terahertz frequencies (∼ 100-300 GHz). The heterostructure was designed using a TCAD-based quantum transport simulator and experimentally investigated through the fabrication and characterisation of RTD devices. The high-frequency RF power performance of the epitaxial structure was analysed based on the extracted small-signal equivalent circuit parameters. Our analysis shows that a 9 µm2, 16 µm2, and 25 µm2 large RTD device can be expected to deliver around 2 mW, 4 mW, and 6 mW of RF power at 300 GHz.

This paper describes the systematic approach to develop low power consumption excitable neuromorphic spike generators using nano-sized resonant tunnelling diode (RTD), including fabrication, characterization and device modelling and spike circuit simulation. The fabrication process of nano sized RTDs has been developed and devices exhibit peak currents of up to 100 uA. The energy efficiency of the RTD spike generator can reach as low as 0.09 fJ per spike. An accurate small signal model of nano RTD has also been developed and is described. This nano-RTD technology could underpin the development of energy efficient neuromorphic computing in the very near future.

A new analysis method for the improvement and optimization of the geometrical layout parameter associated with the on-chip n-well meander line resistor layout to have a low-quality factor (Q) and better performance operating at high frequency is investigated through factorial design experiment DOE efficient method. The factors influencing the Q-factor include the width, line length, line segment, and spacing were studied. The factorial design DOE process model was formulated using the Minitab statistical package. The result in terms of the quality factor and resistance for comparison between the proposed optimized design and conventional design layout is simulated by Sonnet electromagnetic simulation tool and validated by the theoretical mathematical prediction calculation based on an equation of lumped physical model had been presented. Results indicate that a shorter line length and line segment lead to a high impact on the improvement of the Q-factor. By the factorial design experiment, the optimized structure with a single line segment, the width of 5 µm, spacing of 1 µm, and line length of 16 µm had been established to have a lower Q-factor compared to the conventional configuration. The Q-factor was improved by 93% from 1.193 to 0.071 at the targeted 1 GHz frequency by the Sonnet EM simulation tool. The simulation result had shown comparative agreement to the theoretical mathematical predictions analysis result.

Resonant tunnelling diode (RTD) technology is emerging as one of the promising semiconductor-based solid-state technologies for terahertz (THz) wireless communications. This paper provides a review of the state-of-the-art, with a focus on the THz RTD oscillator, which is the key component of RTD-based THz transmitters and coherent receivers. A brief summary on the device principle of operation, technology, modelling, as well as an overview of oscillator design and implementation approaches for THz emitters, is provided. A new insight to device evaluation and to the reported oscillator performance levels is also given, together with brief remarks on RTD-based THz detectors. Thereafter, an overview of the reported wireless links which utilise an RTD in either transmission or reception, or in both roles, is given. Highlight results include the record single-channel wireless data rate of 56 Gb/s employing an all RTD-based transceiver, which demonstrates the potential of the technology for future short-range communications. The paper concludes with a discussion of the current technical challenges and possible strategies for future progress.

This work presents an experimental study of InGaAs/AlAs resonant tunneling diodes designed to improve the diode characteristics using five different device structures. A promising high peak to valley current ratio of 5.2 was obtained for a very low current density device. As expected, the measured results show a significant increase in the current density with thinner barriers and quantum well widths. This is, however, at the expense of an increase in the peak voltages for high peak current density devices. A 36mV/μm2 voltage deviation was found for a diode with a peak current density of 10.8 mA/μm2 that we attribute to self-heating of the diodes, which were confirmed using pulsed dc voltage tests. To demonstrate how the self-oscillation at low frequency can be eliminated, a 25Ω resistor was integrated in parallel with the diodes. The experimental findings suggest that the partially stabilizing resistor is limited by the absolute value of the negative differential resistance. The equivalent circuit of the diodes was validated using on-wafer S-parameter measurements up to 40 GHz. An estimated high frequency operation limit of 2.7THz was deduced for RTD sample #327.

The National Institute of Information and Communications Technology (NICT, Japan) started the Terahertz Project in April 2006. Its fundamental purpose in the next five years is to enable a nationwide technical infrastructure to be created for diverse applications of terahertz technology. The technical infrastructure includes the development of semiconductor devices such as terahertz quantum cascade lasers, terahertz-range quantum well photodetectors, and high-precision tunable continuous wave sources. It also includes pulsed terahertz measurement systems, modeling and measurement of atmospheric propagation, and the establishment of a framework to construct a materials database in the terahertz range including standardization of the measurement protocol. These are common technical infrastructure even in any terahertz systems. In this article, we report the current status of developments in these fields such as terahertz quantum cascade lasers (THz-QCLs) (with peak power of 30 mW, 3.1 THz), terahertz-range quantum well photodetectors (THz-QWPs) (tuned at 3 THz) an ultrawideband terahertz time domain spectroscopy (THz-TDS) system (with measurement range of from 0.1 to 15 THz), an example of a database for materials of fine art, and results obtained from measuring atmospheric propagation.

An overview of semiconductor device modelling is presented which describes the principal methods of representing and analysing modern solid-state devices. The review deals with classical, semiclassical, particle and quantum transport methodologies and compares the relative merits of each approach. The background behind each modelling technique is briefly summarised and recent developments in each area are described. The importance of accounting for non-stationary and quantum effects in small geometry devices is emphasised.

Fundamental oscillations up to 1.04 THz were achieved in resonant tunneling diodes at room temperature. A graded emitter and thin barriers were introduced in GaInAs/AlAs double-barrier resonant tunneling diodes for reductions of the transit time in the collector depletion region and the resonant tunneling time, respectively. Output powers were 7 mu W at 1.04 THz and around 10 mu W in 0.9-1 THz region. A change in oscillation frequency of about 4% with bias voltage was also obtained. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525834]

Bias circuit stability has important implications for the study and application of double-barrier resonant tunneling structures. Stability criteria for resonant tunneling diodes are investigated for the common bias circuit topologies. A systematic study was made of the effect of different bias circuit elements on the measured d.c. I−V curves. A double-barrier diode was studied as an example, with experimental and theoretical results. The main results of the paper are (1) stable resonant tunneling diode operation is difficult to obtain, (2) the low-frequency oscillation introduces a characteristic signature in the measured d.c. I−V characteristic.

A physics-based model is shown to yield the small-signal equivalent circuit of the resonant tunneling diode (RTD) including an analytic expression for both the quantum inductance and capacitance. This model unifies previous models by Brown et al. for quantum inductance and by Lake and Yang for quantum capacitance, and extends the RTD SPICE model of Broekaert. The equivalent circuit has been fit to both current-voltage and microwave S-parameter measurements of AlAs-InGaAs-InAs-InGaAs-AlAs RTDs from 45 MHz to 30 GHz and over biases from 0 to 0.81 V. Good agreement between the model and measurement is shown.

This paper reports on a 15-Gb/s wireless link that employs a high-power resonant tunneling diode (RTD) oscillator as a transmitter (Tx). The fundamental carrier frequency is 84 GHz and the maximum output power is 2 mW without any power amplifier. The reported performance is over a 50-cm link, with simple amplitude shift keying modulation utilized. The 15-Gb/s data link shows correctable bit error rate (BER) of
$4.1 \times 10^{-3}$
, while the lower data rates of 10 and 5 Gb/s show a BER of
$3.6 \times 10^{-4}$
and
$1.0 \times 10^{-6}$
, respectively. These results demonstrate that the RTD Tx is a promising candidate for the next-generation low-cost, compact, ultrahigh data rates wireless communication systems.

A resonant-tunnelling-diode terahertz oscillator capable of wide-band direct modulation was fabricated, and wireless data transmission at a 500-GHz range was demonstrated. An error-free transmission up to the data rate of 22 Gbit/s and a transmission with a bit error rate less than the forward error correction limit up to 34 Gbit/s were achieved.

Circuit models of transmission line elements and of a terahertz resonant tunneling diode (RTD) have been developed. The models allow for a reliable design of RTD-based oscillator and detector circuits. The transmission line elements have been modeled based on electromagnetic field simulations and dc measurements. Their accuracy has been verified through S-parameter measurements. The RTD has been modeled on the basis of dc and S-parameter measurements. The models have been used for the circuit design. A new circuit has been developed that can provide a load impedance that allows for high-output-power oscillators and high-sensitivity detectors. The circuit has been manufactured and measured as an oscillator and as a detector at frequencies around 300 GHz. An excellent agreement between measurement and simulation has been obtained, proving the accuracy of the developed models.

We report a feasibility study of a terahertz imaging system with resonant tunneling diodes (RTDs) that oscillate at 0.30 THz. A pair of RTDs acted as an emitter and a detector in the system. Terahertz reflection images of opaque samples were acquired with our RTD imaging system. A spatial resolution of 1 mm, which is equal to the wavelength of the RTD emitter, was achieved. The signal-to-noise ratio (SNR) of the reflection image was improved by 6 dB by using polarization optics that reduced interference effects. Additionally, the coherence of the RTD enabled a depth resolution of less than 3 mu m to be achieved by an interferometric technique. Thus, RTDs are an attractive candidate for use in small THz imaging systems. (C) 2016 The Japan Society of Applied Physics

Fundamental oscillations up to 1.08THz with the output power of 5.5 microwatts was achieved in GaInAs/AlAs resonant tunneling diodes (RTDs) at room temperature. The graded emitter, thin barriers, and high-indium-composition transit layers were introduced to reduce the tunneling and transit delays. The first two of these structures are the same as those in RTDs oscillating at 1.04 THz reported recently, and the last structure provided for further reduction of the transit time and increase in frequency due to suppression of the Γ-L transition and increment of the launching velocity.

One THz harmonic oscillation was observed in a sub-THz oscillating GaInAs/AlAs resonant tunneling diode integrated with a slot antenna. The fundamental and third-harmonic frequencies were 342 GHz and 1.02 THz, respectively, for a 50 mu m long antenna. The maximum output power of the fundamental mode was around 23 mu W, and that of the third-harmonic component was 2.6% of the fundamental. Theoretical analysis with the van der Pole equation qualitatively explained the measured results. (c) 2005 Americian Institute of Physics.

Resonant tunneling diodes (RTDs) have the potential for use as compact
and coherent terahertz (THz) sources operating at room temperature. In
this paper, sub-THz and THz oscillators with RTDs integrated on planar
circuits are described. Fundamental oscillation up to 0.65 THz and
harmonic oscillation up to 1.02 THz were obtained at room temperature in
our recent study. Limiting factors for oscillation frequency and output
power are theoretically analyzed including tunneling and transit-time
effects and parasitic elements. Oscillation frequency and its dependence
on RTD size are in good agreement with the measured results. Based on
this result, it is shown that fundamental oscillation up to 2.3 THz and
an output power of 60 μW at 1 THz are theoretically expected by
improving the structures of the RTD and the antenna. Voltage-controlled
oscillation, which is useful for the precise control of frequency, is
observed in the RTD oscillators. Coherent power combining in an array
configuration to achieve high output power as well as mutual injection
locking between the array elements are also described.

Recent observations of oscillation frequencies up to 56 GHz in resonant tunneling structures are discussed in relation to calculations by several authors of the ultimate frequency limits of these devices. We find that calculations relying on the Wentzel–Kramers–Brillouin (WKB) approximation give limits well below the observed oscillation frequencies. Two other techniques for calculating the upper frequency limit were found to give more reasonable results. In one method we use the solution of the time‐dependent Schrödinger equation obtained by Kundrotas and Dargys [Phys. Status Solidi B 134, 267 (1986)], while in the other we use the energy width of the transmission function for electrons through the double‐barrier structure. This last technique is believed to be the most accurate since it is based on general results for the lifetime of any resonant state. It gives frequency limits on the order of 1 THz for two recently fabricated structures. It appears that the primary limitation of the oscillation frequency for double‐barrier resonant tunneling diodes will be imposed by intrinsic device circuit parameters and by the transit time of the depletion layer rather than by time delays encountered in the double‐barrier region.

A new equivalent circuit is derived for the double‐barrier resonant tunneling diode. An essential feature of this circuit is the addition of an inductance in series with the differential conductance G of the device. The magnitude of the inductance is τ N /G where τ N is the lifetime of the (Nth) quasibound state through which all of the conduction current is assumed to flow. This circuit model is used to derive values of theoretical oscillator power that are in much better agreement with experimental results than theoretical predictions made without the inductance. The conclusion is drawn that the response of the double‐barrier structure to a time varying potential is consistent with the coherent picture of resonant tunneling.

A common problem in designing with Esaki tunneling diodes in circuits is parasitic oscillations, which occur when these devices are biased in their negative differential resistance (NDR) region. Because of this, the measured current-voltage (I-V) characteristics in the NDR region are usually incorrect, with sudden changes in current with voltage and a plateaulike waveform in this region. Using a full nonlinear analysis of the shunt-resistor-stabilized tunnel diode circuit, we have established the criteria for the range of element values that give stable operation. On this basis, I-V measurement circuits can be designed to be free from both low-frequency bias oscillations and high-frequency oscillations. The design equations lead to a direct I-V measurement setup in which the stabilization resistor in series with a capacitor can be employed. Experimental results validate the approach, and this is confirmed by second-derivative analysis (d^{2}I/dV^{2}) of the measured I-V characteristics.

Data on the operation of very high efficiency microwave oscillators using AlAs/InGaAs quantum well injection transit (QWITT) diodes are presented. A DC-to-RF power conversion efficiency as high as 50% was achieved, which, to the authors' knowledge, is the highest efficiency reported for continuous wave (CW) operation of a two terminal semiconductor device.

While resonant tunnel diodes (RTD's) are useful as
submillimeter-wave oscillators, circuit design constraints imposed to
suppress parasitic bias circuit oscillations have limited output powers
to well below 1 mW. We report a 7-GHz RTD oscillator with a shunt
regulator for bias circuit stabilization. With regulation, oscillator
power is not limited by stability constraints. Regulation elements are
readily integrated with RTD's to construct monolithic RTD oscillator
arrays

By using a nonlinear rather than a linear stabilizing resistor in tunnel-diode oscillator and amplifier circuits, the dc power dissipation in the resistor may be reduced by a factor of 3 for typical germanium tunnel diodes, and by a factor of 6 for typical gallium arsenide tunnel diodes. At the same time ac loading by the resistor is reduced. Such nonlinear stabilizing resistors may consist of reverse- or forward-biased heavily doped pn junctions.

Stability criteria for resonant tunneling diodes are investigated.
Details of how extrinsic elements, such as series inductance and
parallel capacitance, affect the stability are presented. A
GaAs/AlAs/InGaAs/AlAs/GaAs double-barrier diode is investigated, showing
the effect of different modes of low-frequency oscillation and the
extrinsic circuit required for stabilization. The effect of device
stabilization on high-frequency power generation is described. The main
conclusions of the paper are: (1) stable resonant tunneling diode
operation is difficult to obtain, and (2) the circuit and device
conditions required for stable operation greatly reduce the amount of
power that can be produced by these devices

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.

The scattering parameters (S parameters) of double barrier quantum
well resonant tunneling diodes have been measured at various biases with
on-wafer probing techniques. Impedances up to 40 GHz for AlGaAs/GaAs
diodes with asymmetric spacer layers were obtained. It was found that
the impedances could be accurately described by the lumped equivalent
circuit representation. With the conductance-voltage characteristic
derived from high frequency S parameter measurement, the portions of
current-voltage curve that were distorted by oscillation in the dc
measurement are recovered. Peaks corresponding to the process of
electrons discharging from the quantum well are found in the
capacitance-voltage (C-V) characteristic

Handbook of Terahertz Technologies: Devices and Applications

H.-J. Song and T. Nagatsuma, Handbook of Terahertz Technologies:
Devices and Applications. Boca Raton, FL, USA: CRC Press, 2015.

Properties of lattice-matched and strained indium gallium arsenide

- bhattacharya

P. Bhattacharya, Ed., "Properties of lattice-matched and strained indium
gallium arsenide," in EMIS Datareviews. London, U.K.: IEE INSPEC,
1993, no. 8.