Bias Current Density Research Articles

Enhancing CO2 Electroreduction Precision to Ethylene and Ethanol: The Role of Additional Boron Catalytic Sites in Cu-Based Tandem Catalysts.

The electrocatalytic conversion of carbon dioxide (CO2) into valuable multicarbon (C2+) compounds offers a promising approach to mitigate CO2 emissions and harness renewable energy. However, achieving precise selectivity for specific C2+ products, such as ethylene and ethanol, remains a formidable challenge. This study shows that incorporating elemental boron (B) into copper (Cu) catalysts provides additional adsorption sites for *CO intermediates, enhancing the selectivity of desirable C2+ products. Additionally, using a nickel single-atom catalyst (Ni-SAC) as a *CO source increases local *CO concentration and reduces the hydrogen evolution reaction. In situ experiments and density functional theory (DFT) calculations reveal that surface-bound boron units adsorb and convert *CO more efficiently, promoting ethylene production, while boron within the bulk phase of copper influences charge transfer, facilitating ethanol generation. In a neutral electrolyte, the bias current density for ethylene production using the B-O-Cu2@Ni-SAC0.05 hybrid catalyst exceeded 300 mA cm-2, and that for ethanol production with B-O-Cu5@Ni-SAC0.2 surpassed 250 mA cm-2. This study underscores that elemental doping in Cu-based catalysts not only alters charge and crystalline phase arrangements at Cu sites but also provides additional reduction sites for coupling reactions, enabling the efficient synthesis of distinct C2+ products.

Fracture strain improving via structural austenitic stainless steel-coated 22MnB5 plates

A total of 316 austenitic stainless steel (ASS) coatings were deposited on 22MnB5 press-hardening steel plates by varying the substrate bias voltages using a magnetron sputtering technique and quenched in a flat mold with cooling water. The substrate bias current and ion-bombardment energy densities increased up to 0.5 mA/mm2 and 50 J/mm2 at a high voltage of −100 V, and, therefore, the variations in the coatings’ morphologies were owing to the increases in the ion bombardment. The porous bulk pattern appeared in the quenched ASS coating at −100 V, clearly different from the porous columnar structure of the others at −50 and −75 V. The γ-Fe and α-Fe phases were observed from the diffraction peaks, presented the ASS coating and 22MnB5 substrate, respectively. There was no intermetallic compound (IMC) peak detected. In addition, the diffusion layer of the quenched ASS-coated plate was observed, in which its morphology was different from the quenched martensite (M) plate, and proved to be the α-Fe microstructure by the very low α-Fe peak at the standard (110) position. The bright image of TEM and the select area electron diffraction pattern indicated the nanostructure of the quenched ASS coating. The nanohardness of the ASS coating, diffusion layer, and M plate (7.36, 3.60, and 6.25 GPa, respectively) was detected, indirectly proving an α-Fe structure of the diffusion layer. The fracture angles of the 316-coated plates significantly improved from 51.82° at −50 V, 53.77° at −75 V to 57.38° at −100 V, as the ASS structure changed to be porous bulk pattern. The clearance of IMC, coating’s porous bulk pattern, and the low hardness α-Fe diffusion layer benefited for the fracture strain by lengthening the pathway of the crack’s development and blocking the further crack’s propagation, respectively.

Optical response in a high-TcYBCO nanowire

We demonstrate the optical response from high-Tc superconductor nanowires at temperatures above that of liquid nitrogen. Using hard oxide Al2O3 as a mask material, we achieved miniaturized YBa2Cu3O7−δ wires with widths nearing 100 nm, a significant milestone for highly sensitive photodetectors. We investigated the photoresponse of these nanowires at temperatures almost an order of magnitude higher than previously reported, under varying temperature and bias current conditions. Our findings reveal a strong correlation between the optical response and the critical parameters of the superconductor, with peak optical responses close to the critical values of temperature and bias current density. Nanowire response to wavelengths from visible to near-infrared range demonstrated a pronounced absorption maximum at temperatures below Tc. These results lay a solid foundation for the development of high-Tc superconductor nanowire single-photon detectors, understanding of nanoscale high-Tc superconductor structure optical behavior, and advancing the prospects of quantum technologies.

Synergistic effect of proton irradiation and electrical stress on high-speed 850 nm vertical-cavity surface-emitting lasers

The synergistic effect significantly impact VCSEL's reliability for potential applications in spatial data communication. The synergistic effect of 3 MeV proton irradiation and electrical stress on 850 nm high-speed VCSELs is investigated. The degradation of VCSEL slow down under the influence of bias current. However, device degradation is more pronounced during irradiation under high bias current density. Low frequency noise (LFN) analysis results indicate that defects induced by proton irradiation are the primary cause of the optical-electrical parameter degradation in the device. The bias current density significantly influences the final defect yield, leading to variations in the degree of degradation after irradiation at different bias currents. At a bias current density of 6.03 × 105 A/m2, the degradation of the modulation bandwidth is reduced in comparison to the unbiased state. A mechanism investigation into the synergistic effect of proton irradiation and electrical stress on VCSELs lends support for accurately evaluating the radiation hardness of optical communication system composed of VCSELs in harsh radiation environments.

Multilayer-Cavity Tandem Catalyst for Profiling Sequentially Coupling of Intermediate CO in Electrocatalytic Reduction Reaction of CO2 to Multi-Carbon Products.

Electrochemical CO2 reduction reaction (CO2 RR) is an effective approach to address CO2 emission, promote recycling, and synthesize high-value multi-carbon (C2+ ) chemicals for storing renewable electricity in the long-term. The construction of multilayer-bound nanoreactors to achieve management of intermediate CO is a promising strategy for tandem to C2+ products. In this study, a series of Ag@Cu2 O nanoreactors consisting of an Ag-yolk and a multilayer confined Cu shell is designed to profile electrocatalytic CO2 RR reactions. The optimized Ag@Cu2 O-2nanoreactor exhibits a 74% Faradaic efficiency during the C2+ pathway and remains stable for over 10h at a bias current density of 100mAcm-2 . Using the finite element method, this model determines that the certain volume of cavity in the Ag@Cu2 O nanoreactors facilitates on-site CO retention and that multilayers of Cu species favor CO capture. Density functional theory calculations illustrate that the biased generation of ethanol products may arise from the (100)/(111) interface of the Cu layer. In-depth explorations in multilayer-bound nanoreactors provide structural and interfacial guidance for sequential coupling of CO2 RR intermediates for efficient C2+ generation.

Study of In x Ga1-x N/GaN Homotype Heterojunction IMPATT Diodes

In this work, a novel n-In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-<i>x</i></sub> N/N-gallium nitride (GaN) homotype heterostructure is proposed instead of P-GaN/N-GaN homostructure to produce impact-ionization-avalanche-transit-time (IMPATT) diode. Conventional GaN IMPATT device will lose its working ability due to the immature p-type GaN, so this work predicts that the n-In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-<i>x</i></sub> N/N-GaN IMPATT diode can be an alternative to the GaN p-n IMPATT diode; thus, the difficulty of the p-type doping process is avoided. The dc and RF large-signal output characteristics with different compositions are investigated in detail. The simulation results show that the power and efficiency of the novel structure device increase when the In composition increases. When the In composition is greater than 0.4, the performance of the homotype heterojunction IMPATT is better than that of p-n IMPATT. Moreover, homotype heterojunction IMPATT is better in frequency bandwidth, and it can hold greater bias current density than p-n IMPATT. Meanwhile, the performance of homotype heterojunction IMPATT does not depend on the thickness of the InGaN layer, but it decreases as the thickness of the p-type region in p-n IMPATT increases. As it has greater potential in the application, this work brings a reference for the design and manufacture of IMPATT devices based on wide bandgap semiconductor materials, especially GaN materials.

DRT Analysis of Solid Oxide Electrolysis Cells: Polarization Resistance of Fuel Electrodes

Introduction Solid oxide electrolysis cell (SOEC), which enables steam electrolysis by reversely operating solid oxide fuel cell (SOFC), is capable of highly efficient hydrogen production. While SOFC and SOEC are using similar materials and cell structures, electrode reactions in SOEC operation have to be studied in more details. Here in this study, we aim to establish experimental evaluation method for the development of solid oxide cells with high performance and durability by characterizing the electrode reactions through electrochemical impedance measurements and subsequent analysis of distribution of relaxation times (DRT). Such analysis is made to reveal similarities and differences of electrode reactions between SOFC and SOEC. Experimental Three types of cells were prepared with different fuel electrodes: Ni-ScSZ cermet fuel electrode; Ni-GDC co-impregnated fuel electrode; and Rh-GDC co-impregnated fuel electrode. Ni-cermet is widely used as the fuel electrode for SOFC. (Ni, Rh)-GDC co-impregnated fuel electrodes, made by impregnating the catalysts (Ni, Rh) and the Gd-doped ceria on the composite of La-Sr-Ti oxide (LST) and GDC, exhibit high durability at high water vapor partial pressure and against redox cycling (1,2).The electrochemical impedance under the open-circuit condition and at given current densities was measured in the frequency range between 0.1 Hz and 1 MHz with a signal amplitude of 0.02 A/cm2. Negative bias current density means a measurement in the SOEC mode, while positive one means a measurement in the SOFC mode. Measurements were mainly performed for the cells with the Ni-ScSZ cermet fuel electrode at low and high current density up to ± 1.2 A/cm2, in every 0.2 A/cm2. In addition, the cells with (Ni, Rh)-GDC co-impregnated fuel electrodes were also characterized up to high current density. Impedance measurements were made by using an impedance analyzer (Solartron 1255WB). 50%-humidified hydrogen was supplied to the fuel electrode. The operating temperature was 800℃. Results and discussion Figure 1 shows typical DRT peaks of the cell using the Ni-ScSZ cermet fuel electrode. A few DRT peaks are distinguished, which can be used to analyze individual electrode processes and their dependencies. Figure 2 shows the polarization resistance of the cell with the Ni-GDC and Rh-GDC co-impregnated fuel electrodes. Whilst the cell with the Ni-cermet fuel electrode exhibited an increase in polarization resistance in the SOEC mode, the Ni-GDC co-impregnated fuel electrode cell exhibited identical polarization resistance within a wide current density region. A similar trend was also found for the Rh-GDC co-impregnated fuel electrode cell. It was suggested that electrode reactions in the SOEC mode could be more complicated, compared to those in the SOFC mode. Various factors could affect polarization resistance, including the difference in the microstructure of these fuel electrodes, and catalytic activity of GDC. Detailed DRT analysis of the polarization resistance for various fuel electrodes will be presented. References Futamura, A. Muramoto, Y. Tachikawa, J. Matsuda, S. M. Lyth, Y, Shiratori, S. Taniguchi, and K. Sasaki, International J. Hydrogen Energy, 44 (16), 8502 (2019). S. P. Jiang, Mater. Sci. Eng. A, 418, 199 (2006). Figure 1

Magnesium oxide formed by a reaction of thermally-deposited magnesium with molybdenum oxide as a cathode buffer layer material for semi-transparent organic solar cells using gold as a cathode metal

Incorporation of a magnesium oxide (MgO) cathode buffer layer fabricated by a reaction of thermally-deposited magnesium with molybdenum oxide in semi-transparent vacuum-processed Schottky and solution-processed bulk heterojunction OSCs using gold as a cathode metal reduces the series resistance and reverse bias current density, thus preventing the reduction of the open-circuit voltages and fill factors. It is speculated that the high hole-blocking ability of MgO which possesses the deep-lying conduction band level is responsible for these results.

Research on Hysteresis Modeling and Compensation Method of Giant Magnetostrictive Force Sensor

Linearity is an important index for evaluating the performance of various sensors. Under the Villari effect, there may be some hysteresis between the input force and the output voltage of a force sensor, meaning that the output will be multivalued and nonlinear. To improve the linearity and eliminate the hysteresis of such sensors, an output compensation method using a variable bias current is proposed based on the bidirectional energy conversion mechanism of giant magnetostrictive material. First, the magnetization relationship between the input force, bias current, and flux density is established. Second, a nonlinear neural network model of the force‐magnetization hysteresis and a neural network model for the compensation control of the force sensor are established. These models are trained using the magnetic flux density‐force curve and the magnetic flux density‐current curve, respectively. Taking the optimal linearity as the objective function, the bias current under different input forces is optimized. Finally, a bias current control system is developed and an experimental test platform is built to verify the proposed method. The results show that the proposed variable bias current hysteresis compensation method enables the linearity under the return of the force sensor to reach 1.6%, which is around 48.3% higher than under previous methods. Thus, the proposed variable bias current method effectively suppresses the hysteresis phenomenon and provides improved linearity for giant magnetostrictive force sensors.

40 Gbps With Electrically Parallel Triple and Septuple 980 nm VCSEL Arrays

Electrically parallel and optically uncoupled triple and septuple oxide confined vertical-cavity surface-emitting laser (VCSEL) arrays emitting at about 980 nm where each VCSEL has an oxide aperture diameter ( φ ) of ∼7.5 μm transmit data at 40 Gbps at room temperature (RT) in a back-to-back test configuration using standard two-level non-return-to-zero pulse amplitude modulation at bias current densities ( J ) of 17.4 and 10.3 kA/cm2, respectively. Reference single VCSELs processed with the VCSEL arrays on the same wafer pieces with φ ∼7.5, 13.5, and 19.5 μm transmit data at up to 45, 40, and 35 Gbps at RT at J of 20.4, 13.3, and 10.7 kA/cm2, respectively, where the latter two single VCSELs have total emitting areas nearly equal to the total additive emitting areas of the triple and septuple VCSEL arrays, respectively. The RT optical output power at J ∼10 and 15 kA/cm2 is 11.4 and 17.2 mW for the triple arrays and 31.1 and 45.9 mW for the septuple arrays, respectively. By increasing the number of emitters in an array for a fixed φ per VCSEL from 3 to 7 we increase the total optical output power and simultaneously we decrease the J required for error free digital data transmission at 40 Gbps.

Investigation of Stability and Power Consumption of an AlGaN/GaN Heterostructure Hydrogen Gas Sensor Using Different Bias Conditions.

A Pd-functionalized hydrogen gas sensor was fabricated on an AlGaN/GaN-on-Si heterostructure platform. The AlGaN layer under the Pd catalyst area was partially recessed by plasma etching, which resulted in a low standby current level enhancing the sensor response. Sensor stability and power consumption depending on operation conditions were carefully investigated using two different bias modes: constant voltage bias mode and constant current bias mode. From the stability point of view, high voltage operation is better than low voltage operation for the constant voltage mode of operation, whereas low current operation is preferred over high current operation for the constant current mode of operation. That is, stable operation with lower standby power consumption can be achieved with the constant current bias operation. The fabricated AlGaN/GaN-on-Si hydrogen sensor exhibited excellent sensing characteristics; a response of 120% with a response time of < 0.4 s at a bias current density of 1 mA/mm at 200 °C. The standby power consumption was only 0.54 W/cm2 for a sensing catalyst area of 100 × 24 μm2.

Ultra-wide-bandgap AlGaN homojunction tunnel diodes with negative differential resistance

The power efficiencies of state-of-the-art AlxGa1-xN deep-ultraviolet (UV) emitters operating in the &amp;lt;300 nm wavelength region are currently limited to a few percent in part due to limitations in the series and contact resistance which result in excessive drive voltages. AlxGa1-xN tunnel contacts and tunnel junctions in deep-UV devices are a promising route toward increasing these efficiencies by improving the contact resistances, hole injection, and reducing optical absorption by removing undesirable p-GaN contact layers. However, due to doping inefficiencies, standalone tunnel diodes have not been realized in the form of homojunction AlxGa1-xN. In this work, AlxGa1-xN (0.19 ≤ x ≤ 0.58) homojunction tunnel diodes are fabricated with high reverse bias current densities, and one device with x = 0.19 demonstrates a negative differential resistance at ∼2.4 V. AlxGa1-xN p++/n++/n tunnel diodes are compared to reference p++/i/n diodes to provide clarity about the role of tunneling conduction vs leakage conduction. Transmission electron microscopy verifies that heavy doping does not result in visible defects such as Mg precipitates and allows for subsequent epitaxy, critical for buried tunnel junction structures. Increasing the bandgap energy of AlxGa1-xN for higher Al content tunnel junctions decreases the tunnel current, but still allows sufficient conduction necessary for future improvements in deep UV emitter efficiencies.

Graphene transistor based on tunable Dirac fermion optics

We present a quantum switch based on analogous Dirac fermion optics (DFO), in which the angle dependence of Klein tunneling is explicitly utilized to build tunable collimators and reflectors for the quantum wave function of Dirac fermions. We employ a dual-source design with a single flat reflector, which minimizes diffusive edge scattering and suppresses the background incoherent transmission. Our gate-tunable collimator-reflector device design enables the quantitative measurement of the net DFO contribution in the switching device operation. We obtain a full set of transmission coefficients between multiple leads of the device, separating the classical contribution from the coherent transport contribution. The DFO behavior demonstrated in this work requires no explicit energy gap. We demonstrate its robustness against thermal fluctuations up to 230 K and large bias current density up to 102 A/m, over a wide range of carrier densities. The characterizable and tunable optical components (collimator-reflector) coupled with the conjugated source electrodes developed in this work provide essential building blocks toward more advanced DFO circuits such as quantum interferometers. The capability of building optical circuit analogies at a microscopic scale with highly tunable electron wavelength paves a path toward highly integrated and electrically tunable electron-optical components and circuits.

Design of spin-injection-layer in all-in-plane spin-torque-oscillator for microwave assisted magnetic recording

Abstract A new type of spin-torque-oscillator (STO), all-in-plane STO, is introduced for microwave assisted magnetic recording (MAMR) that consist of a spin-injection-layer (SIL) and a field-generating-layer (FGL) with an effective in-plane easy axis due to the shape anisotropy separated with a metallic spacer. In this device, electrons are injected from SIL to FGL while the magnetization of the SIL and FGL is saturated to the out-of-plane by the external magnetic field of ∼1.0 T. Micromagnetic simulations showed that the magnetization direction of SIL can be switched to the opposite direction to that of the applied external magnetic field by the use of spin-transfer-torque. This results in a larger spin accumulation in FGL and its oscillation with a large cone angle at a low bias current density. We designed SIL to reduce the critical current density, Jc, required for the magnetization switching of SIL. Materials with a smaller saturation magnetization in SIL reduce Jc. Smaller spin polarization of SIL leads to a larger spin accumulation in SIL with an opposite direction to the magnetization, resulting in a reduction of Jc. This enables magnetization switching of SIL in small Jc followed by oscillation of FGL with frequency above 20 GHz with a large out-of-plane oscillation cone angle of 45–50°. The validity of this finding was studied experimentally by developing STO with two SIL materials, Co2Fe(Al0.5Si0.5) Heusler alloy and Fe67Co33, the former has the B2 crystal structure with a large spin polarization and the latter has the A2 crystal structure with a smaller spin polarization. The magnetization configuration of SIL and FGL in STO with a diameter of ∼60 nm is investigated experimentally based on the field dependent resistance change and the oscillation behavior is discussed based on the micromagnetic simulations.

On-chip bias circuit for W-band silicon–germanium power amplifier

The performance of the power amplifier determines the detection capability of 77 GHz automotive radar, and the bias circuit is one of the most important parts of a silicon-germanium power amplifier. In this paper, we discussed and designed an on-chip bias circuit based on a silicon-germanium heterojunction bipolar transistor, which is used for the W-band silicon–germanium power amplifier. Considering the low breakdown voltage and the correlation between characteristic frequency and bias current density of the silicon-germanium heterojunction bipolar transistor, the bias circuit is designed to improve the breakdown voltage of the power amplifier and meet the W band characteristic frequency at the same time. The simulation results show that the designed bias circuit can make the amplifier operate normally from −40 to 125 °C. In addition, the output power and smooth controllability of the power amplifier can be adjusted by controlling the bias circuit.

Interface Tailoring Effect for Heusler Based CPP-GMR with an L1₂-Type Ag₃Mg Spacer.

Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effects are of interest in a possible application of magnetic sensor elements, such as read-head of hard disk drives. To improve the junction performance, the interface tailoring effects were investigated for the Heulser alloy, Co2Fe0.4Mn0.6Si (CFMS), based CPP-GMR junctions with an -Ag3Mg ordered alloy spacer. Ultra-thin Fe or Mg inserts were utilized for the CFMS/Ag3Mg interfaces, and CPP-GMR at low bias current density, J and the J dependence were evaluated for the junctions. Although, at low bias J, MR ratio decreased with increasing the inserts thickness, the device output at high bias J exhibited quite weak dependence on the insert thickness. The output voltages of the order of 4 mV were obtained for the junctions regardless of the insert at an optimal bias J for each. The critical current density was evaluated by the shape of MR curves depending on J. increased with the insert thicknesses up to 0.45 nm. The enhancement of suggests that spin-transfer-torque effect may reduce in the junctions with inserts, which enables a reduction of noise and can be an advantage for device applications.

Large Bandwidth, Small Current Density, and Temperature Stable 980-nm VCSELs

A low-cost method to adjust the mirror reflectivity of vertical-cavity surface-emitting lasers (VCSELs) helps to optimize the cavity photon lifetime. The joint variation of photon lifetime and the oxide aperture diameter of our 980-nm VCSELs allows optimization procedures between the laser parameters. A new indicator helps to judge the optimum mirror reflectivity to enable increased bit rates in concert with reduced energy consumption, as well as temperature stability, and a smaller bias current density. Error-free back-to-back data transmission at 50 Gb/s over a wide temperature range from 25 °C to 75 °C for completely unchanged driving conditions is presented amongst other progress, including a 400-fJ/b data transmission energy efficiency at 50 Gb/s.

Integrated temperature sensor with diamond Schottky diodes using a thermosensitive parameter

Diamond Schottky diodes with high figures of merit have been previously demonstrated. However, self-heating during characterization process has been widely observed and fast and high temperature monitoring is highly desired, moreover temperature management is of high interest for device parallelization. In this article, we investigate the possibility to monolithically integrate a small area Schottky diode which will be used as temperature sensor. The diode voltage drop at a constant forward bias current will be used as a thermosensitive parameter. This voltage drop has a quasi-linear variation over a temperature range (experimentally demonstrated from 300K to 440K in this study due to the maximum operating temperature of the experiments) at constant bias current densities between 0.25A/cm2 and 2.5A/cm2, with a sensor sensitivity of −1.6mV/K. It is also demonstrated that this integrated temperature sensor is affected by the biasing conditions of the main Schottky diode. To perform reliable measurements, the temperature measurement must be done while the main Schottky diode is in OFF-state or the fabrication process must be modified. This integrated temperature measurement allows accurate junction temperature monitoring, offering a diamond Schottky diode operation at its best ON-state performance through an active device temperature management.

Optoelectrical Properties of a Heterojunction with Amorphous InGaZnO Film on n-Silicon Substrate

An a-IGZO/n-Si heterojunction device has been fabricated at room temperature by depositing amorphous InGaZnO (a-IGZO) film on n-type silicon substrate by plasma-assisted pulsed laser deposition and its optoelectrical properties studied in detail. The heterojunction showed distinct rectifying characteristic with rectification ratio of 1.93 × 103 at ±2 V bias and reverse leakage current density of 1.6 × 10−6 A cm−2 at −2 V bias. More interestingly, the heterojunction not only showed the characteristic of unbiased photoresponse, but could also detect either ultraviolet or ultraviolet–visible light by simply changing the polarity of the bias applied to the heterojunction. The variable photoresponse phenomenon and the charge transport mechanisms in the heterojunction are explained based on the energy band diagram of the heterojunction.

Analyses and techniques for phase noise reduction in CMOS Hartley oscillator topology

SummaryThis paper reports the analyses of the inductive degeneration, noise filter, and optimum current density techniques for phase noise reduction in the CMOS Hartley oscillator circuit topology. The design of the circuit topology is carried out in 28 nm bulk CMOS technology in a range of common conditions adopted also for a previous study on the Colpitts topology, so complementing the previous study on Colpitts topology and allowing a direct comparison between the Hartley and Colpitts topologies. The theoretical analyses of the three techniques are carried out and verified by means of circuit simulations. The results obtained for the inductive degeneration and noise filter show the existence of an optimum inductance for minimum phase noise. Moreover, the results obtained for the optimum bias current density technique applied to a Hartley oscillator circuit topology incorporating either inductive degeneration or noise filter provide the demonstration of the existence of an optimum bias current density for minimum phase noise. Moreover, we will go beyond this important result, by investigating for the first time the relationship with the optimum current density for transistor minimum noise figure and other general results reported in the literature. Overall, the analyses show that the adoption of these techniques may lead to a potential phase noise reduction up to 16 dB at a 1 MHz frequency offset for an oscillation frequency of 10 GHz, with respect to the traditional Hartley topology. Lastly, we report a comparison under common conditions between Colpitts and Hartley topologies implementing the aforementioned techniques, which could, from a designer perspective, be useful to acquiring a few key insights about the circuit design opportunities and focus the design efforts toward specific directions for performance optimizations. Copyright © 2017 John Wiley &amp; Sons, Ltd.