Collector Region Research Articles

Impact of surface charge density modulation on ion transport in heterogeneous nanochannels

The PNP nanotransistor, consisting of emitter, base, and collector regions, exhibits distinct behavior based on surface charge densities and various electrolyte concentrations. In this study, we investigated the impact of surface charge density on ion transport behavior within PNP nanotransistors at different electrolyte concentrations and applied voltages. We employed a finite-element method to obtain steady-state solutions for the Poisson–Nernst-Planck and Navier–Stokes equations. The ions form a depletion region, influencing the ionic current, and we analyze the influence of surface charge density on the depth of this depletion region. Our findings demonstrate that an increase in surface charge density results in a deeper depletion zone, leading to a reduction in ionic current. However, at very low electrolyte concentrations, an optimal surface charge density causes the ion current to reach its lowest value, subsequently increasing with further increments in surface charge density. As such, at Vapp=+1V\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{app}=+1 \ ext{V}$$\\end{document} and C0=1mM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${C}_{0}=1 \ ext{mM}$$\\end{document}, the ionic current increases by 25% when the surface charge density rises from 5 to 20 mC.m-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{mC}.{\ ext{m}}^{-2}$$\\end{document}, whereas at C0=10mM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${C}_{0}=10 \ ext{mM}$$\\end{document}, the ionic current decreases by 65% with the same increase in surface charge density. This study provides valuable insights into the behavior of PNP nanotransistors and their potential applications in nanoelectronic devices.

Energy transfer, conversion and mechanical regulation in graded piezoelectric semiconductor bipolar junction transistor

While the effective regulation of carrier redistribution in piezoelectric semiconductor devices by mechanical loads through piezoelectric polarized electric fields is well-studied, there is a scarcity of reported research on the influence of energy transfer and conversion characteristics in a non-thermal equilibrium state of these devices. This paper establishes a nonlinear multi-field coupling model for piezoelectric semiconductor graded bipolar junction transistor (PS-GBJT) and proposes a corresponding multi-gradient iterative algorithm. We regard the product of current and built-in electric field as the work done by electric field force on carriers. By incorporating the energy absorbed/released during carrier recombination/generation process, we observe that non-equilibrium carriers act as a medium that facilitates energy conversion between these two mechanisms. Additionally, the non-uniformly distributed doping extends the influence of space charge region throughout entire transistor. In terms of external input electrical energy, the emitter, base, and collector regions play roles of input energy, transfer energy, and output energy, respectively. The study concludes by demonstrating the regulation of energy transfer or conversion efficiency in emitter, base, and collector regions through mechanical loads, thereby altering the heating behavior of entire GBJT and reshaping its energy transfer path. This leads to the significant finding that distinct energy transfer paths fundamentally define the various operational states of GBJT. The novel insights gained from this research hold reference value for thermal design and energy management of electronic devices.

An 800V ultra-low loss field-stop insulated gate bipolar transistor with extended polysilicon gate structure

This paper proposed a Insulated Gate Bipolar Transistor with extended polysilicon gate structure (EPG IGBT) based on P-type drift region (P-Drift), which has electron inverse and accumulation layer. It designs the gate as an extended gate structure with a Bipolar Junction Transistor (BJT), extending into the collector region, and the BJT is always blocked during the switching process. When the EPG IGBT is conducting, the Nj region has a constant positive voltage, which causes the P-Drift to form an electron inversion layer and conduct. Through TCAD simulation, the EPG IGBT maintained the same Breakdown Voltage and turn-off time, while reducing its forward voltage drop (VCE(sat) = 0.98 V) and turn-off loss (Eoff = 0.89 mJ/cm2) by 36 % and 44 %, respectively, compared with FSSJ IGBT of the same process (VCE(sat) = 1.53 V, Eoff = 1.58 mJ/cm2). In addition, the static latch-up I–V and Forward Biased Safe Operating Area (FBSOA) of the EPG IGBT have been significantly improved, providing a new approach for optimizing IGBT.

The effects and mechanisms of 2 MeV proton irradiation on high bias conditions of InP/InGaAs DHBTs

In this work, a 2 MeV proton irradiation experiment has been carried out on self-fabricated InP/InGaAs heterojunction bipolar transistors (HBTs) with fluence of 5 × 1013 H+/cm2 and 1 × 1014 H+/cm2. The degradation and mechanisms have systematically been studied under different bias conditions. The irradiated InP-based HBTs have suffered more sever degradation at low and high bias voltages with larger damage coefficient of current gain (Kβ), due to the increased base recombination current and the slacken collector current respectively. Under high injection current densities, the slow-down of collector current and the collapse of current gain (β) have occurred at increasingly smaller biases as irradiation fluence increases. Consistently, the ideality factor of base current collapses to 1 at high injection current, moreover, the collapse point decreases as fluence increases. The aggravated degradation at high current densities is attributed to the influence of heterojunction barrier effect (HBE) by the structure of the multi-layer collector region. The study would be of great significance for optimizing the device structure and improving the irradiation tolerance.

The functional switching on the operating modes of a piezoelectric semiconductor bipolar junction transistor via mechanical loadings

A nonlinear model was developed on piezoelectric bipolar junction transistors (PS-BJTs) subjected to mechanical loadings by disregarding the assumption of low injection and the approximation of depletion layer. It was found that a PS-BJT subjected to different mechanical loadings can exhibit distinct carrier flow directions, for example, a remarkable transition for an n+pn-type PS-BJT from a transistor unit with amplification capability to two parallel connected PN junctions by applying a pair of lateral tensile or compressive stresses at the emitter and collector interfaces. Further in-depth analysis revealed that shielding effect produced by base region carriers greatly varies according to different loading mode, which leads to changing degrees of mechanical reconstruction on emitter junction barrier. Consequently, an artificial electron pathway (AEP) is formed at the emitter junction by a specific loading configuration. It is just due to the form change of AEP to produce distinct carrier flow directions, which can realize multifunctional switching of electronic devices. In addition, we also found an interesting phenomenon that an AEP can be directly constructed to penetrate the emitter junction by applying mechanical loadings in the longitudinal direction such that electrons in emitter region can travel across the emitter interface directly to the collector region without regulated by the base current. Under that situation, the PS-BJT resembles a parallel combination of a PN junction and an NN junction. This research provides novel insights into the mechanical modulation of piezoelectric electronic devices and the design of novel logic circuits.

The Effect of Collector Region Design on Large-Signal Performance of Horizontal Current Bipolar Transistor (HCBT)

The impact of collector region design on large-signal performance of horizontal current bipolar transistor (HCBT) technology is investigated by calibrated time-domain load-pull measurements. Three representative high-performance devices of the same geometry but with different collector doping profiles, namely, uniform, n-well, and low-doped, are subjected to large-signal measurements wherein the radio frequency (RF) time-domain waveforms of current and voltage are measured to facilitate the determination of the maximum output power for each device. The extensive measurements outline the boundaries of the maximum collector current and voltage swings at RF determining linear operating area, which are a result of the physical phenomena in the high-current and high-voltage regimes, namely, the Kirk effect and impact ionization, respectively. While the highest-doped n-well HCBT provides the highest output power of 25.3 dBm at 1-dB gain compression, and the lowest-doped HCBT enables a wideband match at the collector, the HCBT with a uniform doping profile provides a tradeoff between the output power and bandwidth of the output match. The results show the versatility of HCBT technology as an alternative to CMOS and/or sillicon–germanium (SiGe) large-signal RF circuits for the front-ends (FEs) in the sub-6 GHz wireless communications range.

APPLICATION OF SILICON CARBIDE SAND IN THE TECHNOLOGY OF PROCESSING THE REVERSE SIDE OF SILICON TRANSISTOR STRUCTURES

A method is proposed for processing the reverse side of silicon transistor structures before the metal deposition process and obtaining contact to the collector of the transistor being formed. The parameters of the surface roughness of the silicon surface treated with carbide–silicon sand are studied in order to improve the adhesive properties before spraying the contact to the collector region of the transistor.

Ionic transfer behavior of bipolar nanochannels resembling PNP nanotransistor

This article presents a study on the use of nanofluidic membranes containing straight nanopores as nanotransistors, with a specific focus on the PNP nanotransistor with its three regions representing the emitter, base, and collector. By applying a voltage to the base region, the current flowing between the emitter and collector regions is increased. The nanotransistor has two active intersections in its nanochannel where ions can either collect or deplete. Due to its nanoscale size, the PNP nanotransistor has unique properties that make it suitable for various applications, including ultra-sensitive biosensors, low-power electronics, and rapid computation. We investigated the effect of electrolyte concentrations on the performance of the PNP nanotransistor using a finite-element numerical computing method to determine the steady-state solutions of the Poisson-Nernst-Planck and Navier-Stokes equations. Our results show that the concentration profile in the system varies with voltage, and changing the concentration ratio of the tanks can improve the ionic current. For instance, our findings indicate that the passing ionic current at a Ca/Cg ratio of 3 and a Vapp=+1V is 84% higher than that at a Vapp=−1V. This study provides valuable insights into the performance of the PNP nanotransistor and its potential applications, particularly in the field of nanoelectronics. The results suggest that adjusting the electrolyte concentrations can improve the device's performance, leading to new opportunities for developing nanoscale electronics with enhanced functionality.

Performance investigation of low-power flexible n-ZnO/p-CuO/n-ZnO heterojunction bipolar transistor: Simulation study

Oxide semiconductor-based heterojunction bipolar transistors are widely applicable in flexible, printable, and cost-effective circuit applications. Among earth-abundant metal oxides, zinc oxide and copper oxide inherently show n-type and p-type characteristics, respectively, and their electronic properties can be easily modified during the fabrication process. Accordingly, a planar-type HBT can be achieved by low-temperature growth of the metal-oxide layers on a flexible substrate without the need for further sophisticated processes. In this paper, a double heterojunction bipolar transistor (DHBT) comprised of ZnO layers serving as the emitter and collector regions, along with the CuO layer functioning as the base area is presented. Simulation results demonstrate that the proposed all-metal oxide transistor based on p-CuO/n-ZnO heterojunction enjoys low power consumption owing to the low threshold voltage. High-frequency characterization and DC analysis of the proposed NPN configuration are carried out using the ATLAS/SILVACO package. Our findings reveal that at the base-emitter voltage of 0.55 V, the current gain factor of the device reaches 155, which is larger than those reported in the literature. Furthermore, an ideality factor at the base-emitter voltage of 0.7 V was obtained for the collector-base and emitter-base junctions equal to 1.5 and 1.2, respectively.

Spatiotemporal Resolution of Phase Formation in Thick Porous Sodium Vanadium Oxide (NaV3O8) Electrodes via Operando Energy Dispersive X-ray Diffraction.

Herein, zinc vanadium oxide (ZVO) and zinc hydroxy-sulfate (ZHS) formation as discharge products in sodium vanadium oxide (NVO) cathode materials of two distinct morphologies, NVO(300) and NVO(500), is studied with ex situ and operando X-ray diffraction methods. ZHS formation upon discharge is shown to be favored at higher current densities and reversible upon charge, while ZVO formation is found to be favored at lower current densities but persists throughout cycling. Operando synchrotron-based energy dispersive X-ray diffraction (EDXRD) reveals reversible expansion of the NVO lattice due to Zn2+ during discharge, spontaneous ZVO formation following cell assembly, and ZHS formation concomitant with H+ insertion at potentials less than ∼0.8 V vs Zn/Zn2+. With spatially resolved EDXRD, ZVO formation is show to occur near the separator region first, eventually moving to the current collector region as discharge depth increases. ZHS formation, however, is found to originate from the current collector side of the positive electrode and then propagate through the porous electrode network. This study highlights the special benefits of the EDXRD method to gain mechanistic insight into structural evolution within the electrode and at its interface.

A Technique for Planar Integration of Components of W-Band Backward-Wave Oscillator to Eliminate Misalignment

The alignment within the required tolerance between components like electron beam source, beam-wave interaction structure and spent beam collector is a major challenge in the realization of the high-power vacuum-tube sub-THz source. To overcome this major issue, a novel integrated W-band beam-wave interaction circuit along with spent beam collector and beam adapter region has been designed and developed on two planar metallic plates itself for the first time. It accomplished the level of required alignment of different components of a sub-THz source. This interaction circuit along with beam adapter region and spent beam collector has been developed on a single plate. These structures have been developed using optimized micro-milling techniques with achieved dimensional deviation less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ &lt; 7~\mu \text{m}$ </tex-math></inline-formula> . The average surface roughness is found to be around 100 nm, which is much less than the skin depth in the W band.

Results of the Study of a New Generation Technological Gyrotron System With High Power and Efficiency

A series of work has been carried out to develop a new generation of technological gyrotrons on the first cyclotron harmonic with a radiation frequency of 28 GHz and a power beyond 20 kW. The generation efficiency reaches up to 55% at 6-kW power level without a system of recovery of residual electron energy. The efficiency of the entire setup is about 35% in the mode of maximum radiation power, which is achieved by using a magnetically shielded oil-cooled solenoid. The proper operation of the developed electron-optical system under conditions of a quasi-adiabatic magnetic field in the area of formation of a helical electron beam and a non-adiabatic one in the collector region is confirmed. The letter presents experimental data which is consistent with the results of numerical modeling. This allows us to further count on the implementation of generators up to the W-band frequency range using the magnetic system and high-voltage power sources.

Silicon-Germanium Heterojunction Bipolar Transistor DC and AC Analysis Operating under Cryogenic Temperature

In this work, the numerical simulation of a SiGe heterojunction bipolar transistor (HBT) for DC and AC performance operating at cryogenic temperature with a hydrodynamic carrier transport model is analyzed. A new modified temperature-dependent Si1−xGex energy bandgap model was used. Using a simplified 2D TCAD design structure, the device characteristics on 55 nm SiGe HBT technology and the mobility model are calibrated with experimental data. Base current reversal due to induced impact-ionization at the collector-base junction is analyzed, where the estimated collector-emitter breakdown voltage with the base open (BVCEO) is 1.48 V at 300 K. This reveals good voltage handling ability. At cryogenic temperatures, dopant incomplete ionization in the lightly doped collector region shows a 28% decrease in ionized dopant concentration at 50 K; this affects the base-collector depletion capacitance. The emitter electron barrier tunneling leakage on collector current is studied using a non-local e-barrier tunneling model at different temperatures that shows an improvement in peak DC gain at lower temperatures. Using the small-signal ac analysis, the cut-off frequency and the maximum oscillation frequency are extracted for high-frequency application, and the base widening effect is discussed. A comparison of this work with measured data on 90 nm SiGe HBT is also discussed in brief, which shows improvements in the simulated structure.

Improving the thermal properties of the device in the process of forming a contact with the collector region of a silicon transistor

Objective. The objective of the study is to increase the reliability of the contact of the semiconductor transistor crystal to the body and the reproducibility of the technological process.Method. A method for obtaining multilayer metallization of the reverse side of the crystal has been developed and the most optimal technological modes of its formation have been selected. The parameters of the reliability of the connection of the crystal to the body of the transistor were checked.Results. Layer-by-layer metallization has been obtained, which provides a strong contact to the collector region of the transistor and a reliable fit of the crystal to the base of the case.The control of technological operations showed 100% distribution of solder over the surface of the crystal, the absence of pores in the solder, the improvement in the output characteristics of the device and the increase in the percentage of output usable transistors.Conclusion. An analysis of the experimental results showed that in order to create a reliable contact and remove heat from the collector junction of power semiconductor transistors on the reverse side of the plates, it is necessary to form a metallization in one technological cycle, consisting of four layers of metals (Cr-Ni-Sn-Ag). The technical result of the research is to improve the quality of fit by obtaining a uniform distribution of the layer of Cr-Ni-Sn-Ag metals in a single technological cycle.

X-ray diffraction imaging of fully packaged n-p-n transistors under accelerated ageing conditions.

X-ray diffraction imaging was used to monitor the local strains that developed around individual n-p-n bipolar transistors within fully encapsulated packages under conditions of extremely high forward bias to simulate accelerated ageing. Die warpage associated with the packaging was observed to relax systematically as the polymer became viscous due to the temperature rise associated with the dissipation of heat in the transistor. The direct image size and intensity from the individual transistors were interpreted in terms of a model in which local thermal expansion is treated as a cylindrical inclusion of distorted material, contrast arising principally from lattice tilt. The extension of the thermal strain image along the emitter with increasing power dissipation was ascribed to the effect of current crowding in the emitter region. Weaker large-area contrast associated with the base-collector region was interpreted as arising from the smaller change in effective misorientation at the high X-ray energy of thermal lattice dilation in the base region.

Simulation Study of Low Turn-Off Loss and Snapback-Free SA-IGBT with Injection-Enhanced p-Floating Layer

In this study, a shorted-anode IGBT with an injection-enhanced p-floating layer (IEPF-IGBT) under the N-buffer layer is proposed. Compared to conventional shorted-anode IGBT (SA-IGBT), the IEPF-IGBT has the structural characteristics of an injection-enhanced P-floating (IEPF) layer inserted into the N-buffer layer and the P+ collector region. The IEPF layer and P+ collector region pinch off the electron path during the turn-on period to suppress the snapback effect with a half-cell pitch of 10 μm. In addition, the IEPF layer acts as an injection-enhanced layer that influences the current injection of the holes. There is 56.3% reduction in the turn-off loss of the IEPF-IGBT at the same forward voltage drop.

Effect of uniaxial strain on characteristic frequency of scaled SiGe HBT with embedded stress raiser

In order to further improve the high-frequency characteristics of highly scaled SiGe HBT and consider the compatibility with the mature CMOS technology, a new SiGe HBT structure is proposed by introducing an embedded Si1−yGey stress raiser to produce additional uniaxial stress in the bulk collector region. The energy-band configuration of multi-layered emitter has been investigated by the estimation of the strain effect, and then the influence of stress raiser on the electrical properties and frequency response has been studied by employing the SILVACO TCAD tools. The results show that the device performance has been enhanced to different degrees by altering the Ge fraction (y) in the stress raiser. At y = 0.3, the current gain is increased by approximately 6% compared to the case without stress in the collector region (y = 0). For the case of a uniform Si0.75Ge0.25 base, the cut-off frequency (fT) and the maximum oscillating frequency (fmax) are, respectively, peaked at 507.7 GHz and 730.7 GHz. Approximately 29.1% improvement in fT and 71.5% improvement in fmax have been achieved for the proposed HBT device in comparison with an equivalent traditional SiGe HBT. At y = 0.1, the frequency characteristic is considered the best due to the maximum of fT × fmax product.

New possibilities of collectors with azimuthal magnetic field for multistage energy recovery in gyrotrons

The results of modeling a collector with 4-stage recovery of residual electron energy for the SPbPU gyrotron with a frequency of 74.2 GHz and an output power of 100 kW are presented. For spatial separation of electrons with different energies, an azimuthal magnetic field created by a toroidal solenoid is used. An increase of the recovery efficiency and a decrease of the current of electrons reflected from the collector is achieved by reducing the spread of the radial position of the leading centers of electron trajectories at optimal parameters of the toroidal solenoid, as well as by using a sectioned electron beam. The trajectory analysis of the spent electron beam in the collector region showed the possibility of achieving the total efficiency of the gyrotron, close to 80%.

Thick Sintered Electrodes with Porosity Gradients to Facilitate Ion Transport

Engineering electrode structure such as increasing thickness increases areal energy density and reduces the relative mass and volume allocated to inactive components. However, electrodes with increased thickness encounter ionic and/or electronic transport limitations at high rates of charge/discharge. This poster will describe an investigation of electrodes with porosity gradients. Sintered electrodes were used due to the ability to fabricate relatively thick electrodes using only solid electroactive materials and mild sintering processing. Larger porosity near the separator facilitated ionic transport because this region has greater ion flux relative to regions near the current collector, particularly at high current densities where overall electrode utilization is more restricted to the separator region for both electrodes. A gradient structure would also be desirable because reduced porosity next to the current collector will increase overall cell energy density at lower rates when ion transport restrictions are less of an issue. We will present the experimental and simulation comparisons between electrodes with gradients in porosity, where for comparison the higher porosity is near the separator or current collector region. Electrodes with equivalent total porosity without a gradient structure were investigated as controls.

Area-efficient dual-diode with optimized parasitic bipolar structure for rail-based ESD protections

Lateral parasitic PNP transistor inside P+/N-well diode is explored and investigated for the electrostatic discharge (ESD) protections in I/O interface integrated circuits (ICs). An analysis for the breakdown behavior of the lateral parasitic PNP transistor with base floating is presented for the first time. Simulations on the lateral parasitic PNP transistor have been performed to understand the effects of geometry parameters on current gain β, triggering voltage Vt1 and on-resistance RON. The test structures were fabricated using the UMC 65 nm low-k logic/mixed-mode CMOS process and characterized with the transmission line pulse (TLP) system. The TLP characterization results demonstrate that the triggering voltage Vt1 is strongly influenced by the base region (i.e., base width), and on-resistance RON is mainly affected by the collector region (i.e., collector width) for the finger-type parasitic PNP. Meanwhile, the scalability of thermal failure current It2 has been studied in terms of the periphery of the lateral parasitic PNP and the whole device width.