Off-state Channel Research Articles

A 1.65 to 1.84 GHz Filtering SPDT Switch With Fully Tunable Insertion Phase Using NRN and Mixed Electromagnetic Coupling Techniques

This paper presents a novel filtering single-poledouble-throw (SPDT) switch with continuously tunable center frequency and insertion phase. It is comprised of six varactorloaded microstrip resonators and three tunable non-resonating nodes (NRNs) at source and loads. The controllable mixed electromagnetic couplings are introduced on the two main paths of each channel of the switch. At ON-state, the designed filtering switch can generate a 4th-order bandpass filtering performance with high selectivity, and the insertion phase can be continuously tuned with a full 3600 tuning range by changing the reactances of NRNs and switching the dominated modes of the mixed couplings. At OFF-state, the mixed electromagnetic couplings are set to zero, and hence high isolation can be realized. To validate the proposed technique, a circuit prototype is designed and fabricated. The measured results suggest that the designed filtering SPDT switch can operate with a tunable center frequency ranging from 1.65 GHz to 1.84 GHz, and its insertion phase at ON-state channel can be continuously tuned from -1800 to 1800. During the whole tuning process, the measured in-band isolation for OFF-state channel keeps better than 40 dB.

Wideband-Filtering Switches With Ultra-Wide Stopband Using P-I-N Diodes Loaded on Slotline

This paper presents a new design method for the microwave switch, which uses p-i-n diodes loaded on slotline. A single-pole single-throw (SPST) switch based on the microstrip-slotline-microstrip (M-S-M) transition with non-uniform loading structures is first designed to validate our design approach, which controls the on and off states of the switch by applying different voltages to the diodes. Then a single-pole double-throw (SPDT) switch using p-i-n diodes loaded on slotline T-junction is proposed, which achieves great high-pass response of ON-state channel and 20 dB OFF-state suppression (OSS) within dc to 4.64 GHz. To overcome the poor selectivity of two switches, transmission zeros need to be introduced to achieve band-pass response. Therefore, the slotline of the M-S-M transition is loaded with gradient length short stubs to bring in multiple transmission zeros and achieve SPST/SPDT wideband-filtering switches with ultra-wide stopband. Finally, the proposed filtering switches are fabricated and measured. The measurement results show that the SPDT filtering switch not only provides the expected band-pass response and wide stopband from 4 to 43.5 GHz of ON-state channel, but also has 22.8 dB rejection of OFF-state channel, and the 20.8 dB port-to-port isolation from dc to 43.5 GHz.

The beneficial impact of a p–p + junction on DC and analog/radio frequency performance of a vertical super‐thin body FET

This article investigates the impact of the p–p+ junction (at the body-substrate interface) on different direct current (DC) and analog/radio frequency (RF) performance parameters of a newly invented structure called vertical super-thin body field effect transistor (VSTB FET) through a well-calibrated TCAD tool. At a fixed body doping, the influence of p–p+ junction was inspected for different substrate doping (Ns); which reveals that Ns has a robust control on the device electrostatics. Interestingly, higher Ns is seen to significantly suppress different short channel effects (SCEs), which in turn helps to improve various DC parameters excellently. An increase in Ns from 1015 to 1018 cm−3 improves off-state leakage current and on-to-off current ratio by three orders of magnitude. Also, such a change in Ns decreases subthreshold swing and drain-induced-barrier-lowering by 8.78 mV/dec and 11.15 mV/V, respectively. The underlying physics behind such improvement at higher Ns is explored through the off-state channel electron density profiles corresponding to different Ns values. Further, different analog/RF parameters such as transconductance, input capacitance, gate-drain capacitance, output conductance, gain-bandwidth-product, and transconductance frequency product (TFP) show slight improvement for increasing Ns. In contrast, TGF, GFP, and GTFP offer large enhancement at higher Ns. This study is expected to demonstrate the significance of Ns on device performance.

A BPF Integrated SP4T Switch Using Parallel Switched Fractal Common Feeding Line

This brief presents a method to design bandpass filter (BPF) integrated single-pole quadruple-throw (SP4T) switch by using parallel switched fractal common feeding line. The common feeding line with fractal design can provide four identical coupling paths for cascading switchable bandpass filters (SW-BPFs), which guarantees the consistency of channel electrical performance. The parallel switches are loaded on the fractal common feeding line, so as to decrease the impact of accumulated residual admittances from OFF-state channels. The SW-BPF is realized by the p-i-n diodes loaded tri-mode resonator (TMR), and the transmission zeros due to the intrinsic property of TMR and the source-load coupling are introduced on both sides of ON-state bandpass passband to improve the selectivity. The high suppression property of detuned TMR forms the OFF-state channel. As an example, a single-layer BPF integrated SP4T switch with the central frequency (CF) of 1.0 GHz and the ripple bandwidth (RBW) of 80 MHz is designed and fabricated to validate the proposed design concept.

Theory of transcription bursting: stochasticity in the transcription rates

Transcription bursting creates variation among the individuals of a given population. Bursting emerges as the consequence of turning on and off the transcription process randomly. There are at least three sub-processes involved in the bursting phenomenon with different timescale regimes viz. flipping across the on–off state channels, microscopic transcription elongation events and the mesoscopic transcription dynamics along with the mRNA recycling. We demonstrate that when the flipping dynamics is coupled with the microscopic elongation events, then the distribution of the resultant transcription rates will be over-dispersed. This in turn reflects as the transcription bursting with over-dispersed non-Poisson type distribution of mRNA numbers. We further show that there exist optimum flipping rates (αC, βC) at which the stationary state Fano factor and variance associated with the mRNA numbers attain maxima. These optimum points are connected via $$ \alpha_{C} = \sqrt {\beta_{C} \left( {\beta_{C} + \gamma_{r} } \right)} $$ . Here α is the rate of flipping from the on-state to the off-state, β is the rate of flipping from the off-state to the on-state and γr is the decay rate of mRNA. When α = β = χ with zero rate in the off-state channel, then there exist optimum flipping rates at which the non-stationary Fano factor and variance attain maxima. Here $$ \chi_{C,v} \simeq {{3k_{r}^{ + } } \mathord{\left/ {\vphantom {{3k_{r}^{ + } } {2\left( {1 + k_{r}^{ + } t} \right)}}} \right. \kern-0pt} {2\left( {1 + k_{r}^{ + } t} \right)}} $$ (here $$ k_{r}^{ + } $$ is the rate of transcription purely through the on-state elongation channel) is the optimum flipping rate at which the variance of mRNA attains a maximum and $$ \chi_{C,\kappa } \simeq {{1.72} \mathord{\left/ {\vphantom {{1.72} t}} \right. \kern-0pt} t} $$ is the optimum flipping rate at which the Fano factor attains a maximum. Close observation of the transcription mechanism reveals that the RNA polymerase performs several rounds of stall-continue type dynamics before generating a complete mRNA. Based on this observation, we model the transcription event as a stochastic trajectory of the transcription machinery across these on–off state elongation channels. Each mRNA transcript follows different trajectory. The total time taken by a given trajectory is the first passage time (FPT). Inverse of this FPT is the resultant transcription rate associated with the particular mRNA. Therefore, the time required to generate a given mRNA transcript will be a random variable. For a stall-continue type dynamics of RNA polymerase, we show that the overall average transcription rate can be expressed as $$ k_{r} \simeq h_{\infty }^{ + } k_{r}^{ + } $$ where $$ k_{r}^{ + } \simeq {{\lambda_{r}^{ + } } \mathord{\left/ {\vphantom {{\lambda_{r}^{ + } } L}} \right. \kern-0pt} L} $$ , λ+ is the microscopic transcription elongation rate in the on-state channel and L is the length of a complete mRNA transcript and h∞+ = [β/(α + β)] is the stationary state probability of finding the transcription machinery in the on-state channel.

BPF-Integrated SPDT Switches With Improved Performance Using Frequency Selective Star-Junction Matching Circuit and Switched Magnetic Coupling Technique

This article presents a type of bandpass filter (BPF)-integrated single-pole double-throw (SPDT) switch using the frequency selective star-junction matching circuit and the switched magnetic coupling (SMC) technique, i.e., the lowpass phase shifter (LP-PS) and the quasi-elliptic lowpass filter (QE-LPF) with specified phase shift. Firstly, a high selectivity third-order BPF-integrated single-pole single-throw (SPST) switch with cross coupling and mixed electric and magnetic coupling (MEMC) is designed by the classical coupled-resonator filter design theory. A 34-dB OFF-state suppression (OSS) is achieved due to the detuned resonators, and the OSS can be further increased to 60 dB by the introduced SMC. Then, the BPF-integrated SPDT switches are designed by using proposed frequency selective star-junction matching circuit to cascade the above designed BPF-integrated SPST switch with or without SMC. The proposed frequency selective star-junction matching circuit is used to not only provide the required phase shift for meeting the impedance matching condition, but also have lowpass frequency response for expanding the upper stopband of ON-state channel, the rejection bandwidth of OFF-state channel, and the port-to-port isolation bandwidth. As examples, four BPF-integrated SPDT switches are designed and fabricated to validate the proposed design approaches, which show the improved electrical performance.

A Wideband Bandpass Filter Integrated Single-Pole Double-Throw Switch with Wide Stopband

AbstractThis paper proposes a wideband bandpass filter (BPF) integrated single-pole double-throw (SPDT) switch by using the capacitively coupledLCresonators with loadedp-i-ndiodes. The BPF-integrated on-state channel can be synthesized by using the coupled resonator filter theory, and the off-state channel with high suppression is built due to the misaligned resonant frequencies ofLCresonators. As an example, a BPF-integrated SPDT switch is designed and fabricated with the central frequency of 1 GHz and the 3 dB fractional bandwidth of 29.7 %. The on-state channel has a measured insertion loss of 1.23 dB, and a 20 dB rejection wide stopband from 1.47 GHz to 8.6 GHz. The off state channel has a 43 dB suppression around 1 GHz. The isolation between two ports is better than 52.4 dB. The fabricated BPF-integrated SPDT switch size including bias circuits but excluding feeding lines has a compact size of 0.086 λg×0.096 λg.

Narrowband Single-Pole Double-Throw Filtering Switch Based on Dielectric Resonator

In this letter, a narrowband single-pole double-throw (SPDT) filtering switch based on dielectric resonators (DRs) is presented. It consists of two DRs shared by two channels for size reduction. Printed circuit boards are embedded in the metal cavity to integrate the PIN diodes. The switching between two channels is enabled by controlling the PIN diodes connected to the two output feeding lines. The electromagnetic field distributions of the DR at the TE $_{11\delta }$ mode are studied to control the coupling between the DR and two output feeding lines. When one channel is on, the PIN diode for this channel is turned off, which does not introduce loss and affect the linearity. For the off-state channel, isolation is obtained by controlling the coupling between the DR and output feeding line, which is considerably enhanced. For demonstration, the DR filtering SPDT switch is implemented. The measured results exhibit that the proposed filtering SPDT switch has narrow bandwidth, low loss, high isolation, and high linearity.

Miniaturized frequency-agile bandpass filter integrated single-pole double-throw switch

This article presents a miniaturized frequency-agile bandpass filter (BPF) integrated single pole double throw (SPDT) switch using common LC resonator. The BPF-integrated on-sate channel is constituted by the capacitively coupled LC resonators with loaded varactor diodes and reverse-biased p-i-n diodes. The off-state channel with high suppression is built when the p-i-n diodes loaded LC resonators is forward-biased. As an example, a frequency-agile BPF-integrated SPDT switch with constant 3-dB fractional bandwidth of 18.4% is designed. Its fabricated circuit area including bias circuit but excluding feeding lines is 0.105 λg × 0.079 λg. Measured results show that its 3 dB operating frequency bandwidth covers from 0.499 to 1.077 GHz with in-band insertion loss varying from 4.15 to 3.15 dB. Off-state suppression better than 37.8 dB, port-to-port isolation better than 51.1 dB, and good return loss can be also observed.

Quasi-Lumped-Element Filter-Integrated Single-Pole Double-Throw Switch

In this paper, the capacitively coupled LC resonators with loaded p-i-n diodes are used to develop fixed-response filter-integrated single-pole double-throw (SPDT) switch. The filter-integrated on-state channel with reverse-biased p-i-n diodes can be designed and synthesized using the coupled-resonator filter theory, and the off-state channel with forward-biased p-i-n diodes exhibits high suppression. A 1-GHz filter-integrated SPDT switch with ripple bandwidth of 195 MHz is designed to demonstrate the proposed design concept. Measured results show that it has a low on-state insertion loss (IL) of 1.03 dB, a wide passband, high off-state suppression (OSS), high port-to-port isolation, and compact circuit size. Since both the properly misaligned resonant frequencies of LC resonators and weakly coupling between LC resonators also result in high suppression, a frequency-agile filter-integrated switchless SPDT switch without p-i-n diodes can be designed by using the varactor diodes to realize the corresponding capacitors. A frequency-agile filter-integrated switchless SPDT switch with constant 1-dB fractional bandwidth of 19.5% is also designed. Measured results show that its operating frequency can be tuned from 0.612 to 1.088 GHz with corresponding frequency tuning range of 58% and IL varying from 2.8 to 2.3 dB. Good return loss, high OSS, and port-to-port isolation can be also observed.

A Reliable Extraction Method for Source and Drain Series Resistances in Silicon Nanowire Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs) Based on Radio-Frequency Analysis

This paper presents a new extraction method for source and drain (S/D) series resistances of silicon nanowire (SNW) metal-oxide-semiconductor field-effect transistors (MOSFETs) based on small-signal radio-frequency (RF) analysis. The proposed method can be applied to the extraction of S/D series resistances for SNW MOSFETs with finite off-state channel resistance as well as gate bias-dependent on-state resistive components realized by 3-dimensional (3-D) device simulation. The series resistances as a function of frequency and gate voltage are presented and compared with the results obtained by an existing method with infinite off-state channel resistance model. The accuracy of the newly proposed parameter extraction method has been successfully verified by Z22- and Y-parameters up to 100 GHz operation frequency.

A two-dimensional fully analytical model with polarization effect for off-state channel potential and electric field distributions of GaN-based field-plated high electron mobility transistor

In this paper, we present a two-dimensional (2D) fully analytical model with consideration of polarization effect for the channel potential and electric field distributions of the gate field-plated high electron mobility transistor (FP-HEMT) on the basis of 2D Poisson's solution. The dependences of the channel potential and electric field distributions on drain bias, polarization charge density, FP structure parameters, AlGaN/GaN material parameters, etc. are investigated. A simple and convenient approach to designing high breakdown voltage FP-HEMTs is also proposed. The validity of this model is demonstrated by comparison with the numerical simulations with Silvaco—Atlas. The method in this paper can be extended to the development of other analytical models for different device structures, such as MIS-HEMTs, multiple-FP HETMs, slant-FP HEMTs, etc.

Electrical and Optical Characterization of AlGaN/GaN HEMTs with In Situ and Ex Situ Deposited SiN x Layers

A comparative study of AlGaN/GaN high-electron-mobility transistor (HEMT) surface passivation using ex situ and in situ deposited SiN x is presented. Performing ex situ SiN x passivation increased the reverse gate leakage and off-state channel leakage by about three orders of magnitude. The in situ SiN x layer was characterized using transmission electron microscopy (TEM) and capacitance–voltage (CV) measurements. Photoluminescence (PL) spectra indicated a reduction of nonradiative recombination centers in in situ SiN x -passivated samples, indicating improved crystal quality. CV measurements indicated a reduction of surface state density as well, and thus better overall passivation using in situ SiN x . Electroluminescence (EL) images of the channel regions in AlGaN/GaN HEMT devices operating in forward blocking mode with up to 400 V drain bias demonstrated reduced channel emission profiles of in situ-passivated devices. Compared with a nonpassivated reference sample, the reduced EL emission profiles correlated with a reduced channel temperature on ex situ SiN x -passivated devices.

Recessed Channel Fin Field-Effect Transistor Cell Technology for Future-Generation Dynamic Random Access Memories

A new bulk fin field-effect transistor (bulk FinFET) with a recessed channel structure is proposed as a future dynamic random access memory (DRAM) cell transistor following the recess-channel-array transistor (RCAT). An enlarged effective channel length improves the relationship between off-state channel leakage (Ioff) and gate-induced drain leakage (GIDL) current, which correspond to the static and dynamic retention characteristics of a DRAM chip. The high current drivability of FinFET is maintained even with a recessed channel. A recessed-channel FinFET (RC-FinFET) shows excellent DC characteristics (subthreshold swing, drain-induced barrier lowering and body-bias effect) and longer retention time than a conventional local-damascene FinFET (LD-FinFET).

A closed-form model of the drain-voltage dependence of the off-state channel electric field in a HEMT with a field plate

The channel-field distribution under the field plate in a high-electron mobility transistor (HEMT) in the off-state is modeled in terms of drain-voltage and physical parameters. Depending upon the drain-voltage and device structure, this distribution can have up to three peaks-one each at the two ends of the field plate and at the drain. It is shown that the complete distribution can be approximated as superposition of triangular distributions, which are analogous to that in the depletion layer of a p-n junction; consequently, the peaks increase as square root of the drain-voltage. The model fits into two-dimensional simulation results and allows estimation of the minimum drain-gate separation, the electric-field reduction, the breakdown-voltage improvement, and critical field for the onset of a parasitic phenomenon in a HEMT with a field plate

Ferroelectric field effect in epitaxial LaVO3/(Ba,Sr)/TiO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 heterostructures

A ferroelectric field effect was demonstrated in epitaxial LaVO3/(Ba,Sr)TiO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 semiconductor–ferroelectric–metal heterostructures grown on (001) SrTiO3 single crystal substrates by pulsed laser deposition. A high degree of c-axis orientation and strong in-plane texture measured by four-circle x-ray diffractometer confirmed the epitaxial crystallographic relationships between the layers. A 30 nm interlayer of (Ba,Sr)TiO3 was required to prevent decomposition of the (Pb,La)(Zr,Ti)O3 during growth of LaVO3 at 500 °C in a vacuum. The capacitance–voltage measurement of the heterostructure exhibited a decrease in capacitance of ∼20% at positive voltages, which was explained by the formation of the depletion region in the semiconducting LaVO3. The observed ferroelectric field effect revealed the modulation of the channel resistance confirming the formation of a depletion region estimated to be ∼7 nm in depth. On- to off-state channel resistance ratios up to 2.5 were measured.

Epitaxial Perovskite LaVO3/(Ba,Sr)TiO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 Heterostructures for Ferroelectric Field Effect Memory Devices

AbstractThe ferroelectric field effect was demonstrated in epitaxial perovskite LaVO3/(Ba,Sr)TiO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 heterostructures grown on (001) SrTiO3 single crystal substrates by pulsed laser deposition. A high degree of c-axis orientation and strong in-plane texture revealed by x-ray diffraction indicated the epitaxial crystallographic relationships between the layers. The heterostructure showed optimal ferroelectric hysteresis with remanent polarizations over 30 μC/cm2. The capacitance measurement as a function of voltage coupled with the measurement of channel resistance revealed the formation of a depletion layer in the semiconducting LaVO3. A ratio of ON- to OFF-state channel resistance of up to 2.5 was observed.