Electrical Characteristics Research Articles

The mercurial rise in research of halide perovskites: what´s next

AbstractPerovskites are of high potential in the ongoing academic research, due to their distinctive electrical properties and crystalline structures. Halide perovskites show high light emissive properties and panchromatic light absorption across the visible spectrum. The exceptional electrical characteristics, such as their long carrier lifespan, high diffusion length, and charge carrier mobility, allow the electric charges to be transported and collected effectively. Furthermore, by tuning the cations and anions composition, perovskite’s opto-electrical properties can be altered. Moreover, dimension reduction affects their band gap and intrinsic features to induce higher structural stability but at the cost of the quantum confinement effect. Owing to their exceptional properties, halide perovskites are being researched in energy-related and semiconducting applications, hold high promise and the future looks bright. But challenges remain, and the larger question is what needs to be done to make them more stable.

Optimizing ZnSe nanorods with La doping for structural, electrical, and dielectric properties in device applications

Nano-materials, pure Zinc Selenide (ZnSe), and rare earth (Lanthanum) doped ZnSe (Zn1-xLaxSe, x = 0.00, 0.02, 0.04, 0.06) were synthesized via a facile and low-cost hydrothermal method. X-ray diffraction (XRD) demonstrated that the nanoparticles grow in cubic crystal phase with high degree crystallinity, and the measured crystallite size of La-doped ZnSe ranges from 31.95 to 31.11 nm. Mitigation in crystallite size was observed with the inclusion of La and enhancement in the lattice constant ‘a’ from 5.6565 Å to 5.6818 Å. Morphological study (FESEM) depicts synthesized materials' morphologies as nanorods. The FESEM images indicate the random distribution of the nanorods across the crystal lattice, regardless of the accumulation of the nanorods, showing lumps in the synthesized material sample. The estimated grain size of pure ZnSe nanorods ranges from 137.6 to 496.9 nm. Electrical features revealed that direct current (DC) electrical conductivity ‘σdc’ enhances with temperature, affirming the semiconducting behavior of the materials. Increased lanthanum content enhances the ‘σdc’ from 3.08 × 10–5 (Ω cm)-1 to 5.94 × 10–5 (Ω cm)-1 at 303 K while lessening the activation energy value from 0.134 to 0.104 eV. Dielectric features, including relative permittivity (ε'), loss factor or dielectric loss (ε''), tangent loss (tanδ), as well as AC conductivity (σac), indicate a direct proportionality with temperature, and elevated values of all the dielectric parameters are noted with La-doping. An increase in dielectric constant with doping concentration displayed that the prepared nanocrystals have valuable dielectric and capacitive behavior. The outcomes of electrical and dielectric features display that the prepared nanorods have vital characteristics for developing optoelectronic devices, solar cells, photocatalysts, and light-emitting diode applications.

Influence of hydrocarbon environment on electrical characteristics of Ge-As-Se-S chalcogenide glass system

The effect of propane-butane gas mixture on volt-Ampere characteristic (VAX) of thin–layer sandwich structure Al-Ge33As17S35Se15-Te obtained by thermal evaporation method in vacuum was investigated. It has been established that under the influence of gas atoms, the oscillations observed in VAX gradually decrease and disappear. This result is explained by the accumulation of neutral gas atoms into lower atomar pores. It has been shown that neutral gas atoms collected in pores lead to weakening of thermal-field ionization processes of U--centers, and to increase the speed of periodic deflection of charge carriers by these centers, which leads to an increase in the resistance of the sample.

Influence of the annealing temperature on the self-powered CuO/ZnO NRs heterojunction photodetector

In this study, the fabrication and comprehensive analysis of CuO/ZnO nanorod (NR) heterojunction photodetectors were carried out, focusing on the influence of annealing temperatures (400 °C, 500 °C, and 600 °C) on their structural, optical, and electrical characteristics. The ZnO nanorods were synthesized via a hydrothermal method, followed by a spin-coating deposition of CuO thin films. The resultant heterojunctions were subjected to different annealing treatments to determine the optimal conditions for enhanced photodetector performance. Characterization techniques such as Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive x-ray Spectroscopy (EDX), x-ray Diffraction (XRD), and UV–vis spectroscopy were employed to assess the quality and composition of the heterostructures. The analyses revealed a polycrystalline structure with monoclinic phases for CuO and wurtzite phases for ZnO. Photodetectors annealed at 400 °C exhibited the highest performance metrics, achieving a photoresponse ratio (Iph/Idark) of 26.3, photosensitivity (Sph%) of 2531.6, and a specific detectivity (D*) of 4.58 × 1010 Jones under 405 nm UV light illumination. These devices also demonstrated rapid response times of 0.8 s without any external bias, indicating effective exciton separation and charge transport facilitated by the built-in electric field at the heterojunction interface. The study underscores the critical role of annealing temperature in optimizing the photodetector properties of CuO/ZnO NRs, positioning these self-powered devices as promising candidates for future ultraviolet sensor applications in optoelectronics.

Complementary Analysis and Performance Improvement of a Hydro-Wind Hybrid Power System

Hydropower as a flexible regulation resource is a rare choice to suppress the ever-increasing penetration of wind power in electrical power systems. The complementary characteristics and performance improvement of a hydro–wind hybrid power system based on a mathematical model of the hybrid power system is studied in this paper. This established model takes into account the stochastic variation in wind speeds in the wind power subsystem and the hydraulic–mechanical–electrical coupling characteristics of the hydropower subsystem. The complementary analysis is conducted based on the evaluation variables outputted by the established model, such as the wind power, hydro-regulation power, hydraulic power, and frequency. To make full use of the regulation capability of the hydropower system, the optimization of parameter settings is also carried out to improve complementary performances of the hybrid power system. The results from the complementary analysis show the detailed characteristics of hydro–wind coordinated operation under different types of real wind speeds. Here, 95% of installed hydro-capacity is used to complement the power shortage of the intermittent wind energy under the low wind speed. Alternatively, only around 66% of the installed hydro-capacity can be utilized to cope with the fluctuation in wind power under the medium and high wind speeds before the optimization of parameter settings. The recommended values and change rules of the control, hydraulic, and electrical parameters for the hydropower system are subsequently revealed from the analysis of parameter settings to contribute to a stable and safe hybrid power system. The results show that the optimized parameter can increase the maximal regulating capacity of the hydropower system by nearly 9 MW, approximately a sixth of the total installed hydropower capacity. The method and results obtained in this paper provide theoretical and technical guidance for the safe and economical operation of power stations.

Monitoring system for electrical load usage characteristics in electrical engineering building

Electrical energy is becoming increasingly essential for educational activities in electrical engineering facilities, as these activities include the use of electrical equipment. The quantity of electrical loads in buildings escalates annually, resulting in increased demand on existing lines and the original design of building construction. Nonetheless, the positioning and allocation of the load within the panel do not align with the augmentation of the load. Consequently, the load becomes uneven across all three stages. Phase T is experiencing an overload, while Phase R has a lesser burden compared to Phases S and T. The maximum current in Phase T is 36.3 A; the imbalance is excessive, leading to a neutral current of 25.2 A. This is perilous since the present value at the neutral point ought to be zero; if the load remains unregulated, it will lead to a contact voltage in electrical apparatus. The utilization of cables is unsuitable due to the substantial connected load, while the cable diameter is merely 2.5 mm², capable of conducting a maximum current of 21 A. Therefore, it is imperative to reassess the electrical installation in the engineering building to avert short circuit disruptions.

The Effect of Air Humidity on the Performance of DC Link Capacitor Components

DC link capacitors (DCLCs) are key devices in converters. The relative humidity affects the performance of the elements of a DCLC. Currently, there are relatively few studies on the effect of relative humidity on the electrical characteristics of the elements of DCLCs during the production process. This study describes the effects and the control of the relative humidity in the production process. For this purpose, a DCLC component withstand voltage test platform and a DCLC component aging test platform were established. The voltage withstand tests were conducted during different processes and at different relative humidities, and life aging tests were conducted at different relative humidities and different storage times. The results show that after the winding and metal-spraying processes, the voltage withstand levels of the components stored at 30% RH, 60% RH, and 80% RH were very close to that of the components at 3000 VDC; after the heat-setting process, the voltage withstand levels of the components stored at 30% RH, 60% RH, and 80% RH showed a decreasing tendency compared with the level of the components at 3000 VDC. Regarding the samples, after the heat-setting process, stored at 30% RH and 60% RH for 24 h, 96 h, 168 h, 240 h, and 336 h and 2000 h of the aging tests, the capacitance decreases monotonically as the storage time is increased but never exceeds 3%, and the capacitance change decreases as the relative humidity increases. This study can provide important guidance for the humidity control of various processes in the production of DCLCs.

From Molecular Electronics to Molecular Intelligence.

Molecular electronics is a field that explores the ultimate limits of electronic device dimensions by using individual molecules as operable electronic devices. Over the past five decades since the proposal of a molecular rectifier by Aviram and Ratner in 1974 ( Chem. Phys. Lett.1974,29, 277-283), researchers have developed various fabrication and characterization techniques to explore the electrical properties of molecules. With the push of electrical characterizations and data analysis methodologies, the reproducibility issues of the single-molecule conductance measurement have been chiefly resolved, and the origins of conductance variation among different devices have been investigated. Numerous prototypical molecular electronic devices with external physical and chemical stimuli have been demonstrated based on the advances of instrumental and methodological developments. These devices enable functions such as switching, logic computing, and synaptic-like computing. However, as the goal of molecular electronics, how can molecular-based intelligence be achieved through single-molecule electronic devices? At the fiftieth anniversary of molecular electronics, we try to answer this question by summarizing recent progress and providing an outlook on single-molecule electronics. First, we review the fabrication methodologies for molecular junctions, which provide the foundation of molecular electronics. Second, the preliminary efforts of molecular logic devices toward integration circuits are discussed for future potential intelligent applications. Third, some molecular devices with sensing applications through physical and chemical stimuli are introduced, demonstrating phenomena at a single-molecule scale beyond conventional macroscopic devices. From this perspective, we summarize the current challenges and outlook prospects by describing the concepts of "AI for single-molecule electronics" and "single-molecule electronics for AI".

Unraveling the influence of defects in Janus MoSSe and Janus alloys MoS2(1−x)Se2x

We investigate the effect of structural and substitutional defects in Janus MoSSe and the Janus alloys MoS2(1−x)Se2x by a comprehensive analysis. Distinct Raman signatures are associated with various defect types and densities, mirroring the evolution from MoSe2 to Janus alloys to ideal Janus MoSSe. By the corresponding stoichiometrical and structural changes, the band gap can be tuned from 1.50 eV up to 1.68 eV at room temperature. Electrical characterization in a field effect device uncovers the impact of defects on conductivity, mobility (up to 2.42 × 10−3 cm2 V−1 s−1), and threshold voltages. A decrease of n-type doping of 5.3 × 1011 cm−2 in Janus MoSSe compared to the Janus alloy points towards an increased work function and a reduction of defects. Our findings deepen the understanding of defect physics in 2D Janus materials and pave the way for tailored defect engineering strategies for advanced (opto-)electronic applications.

Annealing temperature induced variation on the electrical and photoelectrical characteristics of Al/Feq3/p-Si/Al heterojunction diode

Annealing temperature induced variation on the electrical and photoelectrical characteristics of Al/Feq3/p-Si/Al heterojunction diode

Investigation and Demonstration for immunoassay technology based on impedance Amplifies of magnetic and dielectric microbeads

BackgroundBead-based immunoassays typically require researchers to perform the analysis in a laboratory setting, involving complex processing procedures, most of the time, constant potential or current instruments are used to measure the bio-impedance change. However, almost all biological materials are decorated on the electrode surface to obtain the maximum sensitivity, resulting in difficulty to clean, separate, and other applications of fixed bead-based immunoassay. ResultWe present an innovative unfixed bead-based immunoassay technology that utilizes electrical impedance characteristics, offering the advantages of being rapid, portable, miniaturized, and cost-effective. This technique which is known as Impedance-enhanced electrochemical immunoassay (IE-ECIA) employs antibody-coated Magnetic beads (MBs) and Dielectric beads (DBs) linked to antigens for quantitative with miniaturization electronic devices, which has been successfully applied in an immune impedance sensor for detecting the Dengue virus (DENV), which is an affordable test with a low-cost microfluidic impedance biosensor combined with immune magnetic and dielectric micro/nanobeads for antigen detection. HighlightThe proposed immunoassay technology introduces a novel microfluidic platform incorporating magnetic and dielectric beads alongside with an electrochemical impedance biosensor, therefore facilitating continuous-fluid quantitative analysis. This innovative and unconventional approach leverages free-motion multiplex beads housing magnetic and dielectric bead-bound antigens within a simple linear microchannel of microfluidic chip architecture, making the high-through measurements more efficient, enhanced Electrochemical immunoassay (ECIA) signals of Bio-on-magnetic-beads (BOMB). This advancement holds significant potential for enhancing diagnostic capabilities for emerging infectious diseases within clinical environments, thereby bolstering rapid detection capabilities and aiding in the advancement of novel pharmaceuticals, benefiting all the stakeholders.

Gray relational analysis for parametric optimization of micro-EDM of thermo-mechanically processed AA7075 and AA7075/SiC/Gr composite

The AA7075 alloy and AA7075/SiC/Gr hybrid composite prepared by the stir-casting method have been further thermo-mechanically processed through unidirectional hot rolling and hot cross-rolling routes to eliminate casting defects like voids, blow holes etc. Three initial sample temperatures, that is, 350℃, 400℃, and 450℃, have been considered for the hot cross-rolling. The Al alloy and its hybrid composite prepared at different rolling temperatures are studied to investigate their micro-machining behavior through micro-electric discharge machining (µ-EDM). The micro-holes are made on the rolled samples along the rolling direction of the final rolling pass using a tool with twist drill bit geometry. Further, multi-objective optimization of the µ-EDM process parameters considering the response parameters viz. material removal rate (MRR) and tool wear rate (TWR) has been carried out using the gray relational analysis (GRA) technique. The µ-EDM parameters chosen to optimize in this study are voltage, pulse on time, and tool rotation. The obtained GRA results are further analyzed through normality and equal variance tests. The R-squared values of 95.02% and 95.53% for AA7075 alloy and hybrid composite, respectively, indicate that the data fit well with the statistical model. In material removal, the different electrical and thermal characteristics of the Al matrix and the reinforcements possibly generate sparks with a different characteristic that ultimately affects the MRR of the composite. Through scanning electron microscopy (SEM), the morphological study confirmed the presence of globules and voids on the machined surface. The formation of globules and voids is more significant in the AA7075 alloy than in the composite.

Low temperature atomic layer deposition of PbO2 for electrochemical applications

A low temperature atomic layer deposition (ALD) process for PbO2was developed using bis(1-dimethylamino-2-methyl-2-propanolate)lead(II), Pb(DMAMP)2, and O3as the reactants, with a high growth rate of 2.6 Å/cycle. PbO2readily reduces under low oxygen partial pressures at moderate temperatures making it challenging to deposit ALD PbO2from Pb2+precursors. However, thin films deposited with this process showed small crystalline grains of α-PbO2and β-PbO2, without signs of reduced PbOxphases. The ALD PbO2thin films show the high electrical conductivity characteristic of bulk PbO2. In situ measurements of ALD PbO2film conductivity during growth suggest a reaction mechanism by which sub-surface oxygen mobility contributes to the growth of resistive PbO or PbOxduring the Pb(DMAMP)2surface reaction step, which is only fully oxidized from Pb2+to Pb4+during the O3reaction step. These films were electrochemically reduced to PbSO4in H2SO4and then reoxidized to PbO2, demonstrating their suitability for use as an electrode material for fundamental battery research and other electrochemical applications.

Two-Stage Optimization Scheduling of Integrated Energy Systems Considering Demand Side Response

This study proposes a two-level optimization scheduling method for multi-region integrated energy systems (IESs) that considers dynamic time intervals within the day, addressing the diverse energy characteristics of electricity, heat, and cooling. The day-ahead scheduling aims to minimize daily operating costs by optimally regulating controllable elements. For intra-day scheduling, a predictive control-based dynamic rolling optimization model is utilized, with the upper-level model handling slower thermal energy fluctuations and the lower-level model managing faster electrical energy fluctuations. Building on the day-ahead plan, different time intervals are used for fast and slow layers. The slow layer establishes a decision index for command cycle intervals, dynamically adjusting based on ultra-short-term forecasts and incremental balance corrections. Case studies demonstrate that this method effectively leverages energy network characteristics, optimizes scheduling intervals, reduces adjustment costs, and enhances system performance, achieving coordinated operation of the IES network and multi-energy equipment.

LG = 50 nm T-gated and Fe-doped double quantum well GaN‒HEMT on SiC wafer with graded AlGaN barrier for future power electronics applications

High-performance LG = 50 nm graded double-channel (GDC)-HEMT featuring AlN top barrier, recessed T-gate and graded-AlGaN bottom barrier is designed and investigated. Two quantum wells are formed in the AlN-GaN-graded AlGaN-GaN multilayer structure developed on a SiC substrate and the clear double hump feature of the transconductance (GM), cut-off frequency (fT), and capacitance plots clearly illustrates the double-channel (DC) behavior. The investigations carried out to explore the impact of barrier thickness (both AlN & graded-AlGaN) revealed superior performance with the GM showing two peaks at 181.5 & 488.1 mS/mm, the peak-drive-current (ID_peak) with VGS biased at 3 V is 1.81 A/mm, maximum saturation drain current of 3.08 A/mm (VGS = 3V), and the fT derived from the left- and right-hump are 263.7 GHz & 354.2 GHz, respectively, when both barriers are 6 nm thin, attributable to enhanced 2DEG density due to the coordination of channels because of proximity and lower leakage. It has been noticed that when the bottom barrier is thick, the DC behaviour is less obvious due to insufficient gate access to the lower channel. We investigated the impact of varying the Al % in AlGaN top barrier on the DC/RF performance of GDC-HEMTs, demonstrating enhanced performance with increased Al content, particularly for Al0.35Ga0.65N. By using various metals, this study also investigates how gate engineering affects the electrical characteristics of the GDC-HEMT. The lower ϕm (work function) of the Al-gate led to better DC/RF performance. When the Schottky barrier rises as a result of the conduction band edge being elevated, the performance reduces, and the threshold voltage (Vth) increases. Since it is essential to comprehend the role that source resistance (Rs) & drain resistance (Rd) play in RF design, we have also conducted simulations by varying the source-gate gap (LGS) & drain-gate gap (LGD). Due to low Rs & Rd, it was determined that the GDC-HEMT performed better at the smallest LGS & LGD. The extraordinary performance strongly highlights the immense potential and applicability of the GDC-HEMTs for future broadband power amplifiers.

Novel ionic liquid systems based on three-nitro phenoxide: Spectroscopic and electronic characterization using theoretical and experimental study

After extensive computations, novel trinitro compounds, triethyl ammonium 2,4,6-trinitro phenoxide (TEA-TNP) and tetramethyl guanidinium 2,4,6-trinitro phenoxide (TMG-TNP), are designed, synthesized, and identified. The Geometrical parameters, electronic properties, and spectroscopic analysis have been investigated by comparison of theoretical and experimental methods. Spectrum features that include IR and Raman have been calculated, and 1H and 13C NMR spectra are compared to experimental data. Electronic analysis has been investigated through NLO, FMO, UV-Vis, NBO, and MEP calculations. B3LYP/6-311++G(d,p) is highly successful and dependable for predicting ionic liquid stability, electrical characteristics, and spectroscopy. Both TEA-TNP and TMG-TNP are introduced as suitable candidates for NLO material. TMG-TNP with greater nucleophilicity (N) is a noncorrosive lubricant additive that reduces friction and wear for tribological performance.

Analysis of the Sr2GdTi2Nb3O15 ceramic: Investigation into its structural properties and complex impedance spectroscopy

In this study, we successfully synthesized tetragonal tungsten bronze with the nominal formula Sr2GdTi2Nb3O15 and systematically examined of its structure, dielectric, and electrical properties. The material was synthesized through the solid-state reaction technique at a temperature of 1350 °C. The formation of the tetragonal tungsten bronze in the P4/mbm space group was verified via Rietveld refinement using X-ray diffraction data. The electrical characteristics of the ceramic were examined using non-destructive complex impedance spectroscopy (CIS) across a range of frequencies (10–106 Hz) at various temperatures. The real component of impedance (Z') displayed a decrease with rising frequency, suggesting a negative temperature coefficient of resistance (NTCR) for this sample. The Cole-Cole plot of the compound exhibits two semicircles, with the compound's resistance gradually decreasing as the temperature increased. Moreover, the activation energy (Ea) was found to be approximately 0.9 eV, which confirms that oxygen vacancies are responsible for the observed relaxation behavior. Complex modulus analysis confirmed the presence of non-Debye relaxations. These results contribute to a thorough comprehension of the structural and electrical characteristics of Sr2GdTi2Nb3O15, opening avenues for potential applications in diverse electronic devices.

PVC/CNT Electrospun Composites: Morphology and Thermal and Impedance Behavior.

Due to their mechanical robustness and chemical resistance, composite electrospun membranes based on polyvinyl chloride (PVC) are suitable for sensor applications. Aiming to improve the electrical characteristics of these membranes, this work investigated the effects of the addition of carbon nanotubes (CNTs) to PVC electrospun membranes, in terms of morphology and thermal and impedance behavior. Transmission electron microscopy images evidenced that most of the nanotubes were encapsulated within the fibers and oriented along them, while field-emission scanning electron micrographs revealed that the membranes consisted of uniform fibers with an average diameter of 339 ± 31 nm, regardless of the addition of the carbon nanotubes. With respect to the neat resin, the addition of nanotubes caused a significant lowering of the glass transition temperature (up to 20 °C) and a marked change in the second degradation step of PVC. Nyquist plots from electrical impedance spectra showed a charge transfer resistance (RCT) of 38 and 40 MΩ for neat PVC and PVC/CNT 3 wt.% membranes, respectively, indicating that, in the dry state, the encapsulation of CNTs in the fibers and the high porosity of the membranes prevented the formation of a percolation network, increasing the electrical resistance. In the wet state, however, there was a greater change in the impedance behavior, decreasing the resistance RCT to 4.5 and 1.1 MΩ, for neat PVC and PVC/CNT 3 wt.% membranes, respectively. The results of this study, showing a significant variation in impedance behavior between dry and wet membranes, are relevant for the development of various types of sensors based on PVC composites.

Optical, Photophysical, and Electroemission Characterization of Blue Emissive Polymers as Active Layer for OLEDs.

Polymers containing π-conjugated segments are a diverse group of large molecules with semiconducting and emissive properties, with strong potential for use as active layers in Organic Light-Emitting Diodes (OLEDs). Stable blue-emitting materials, which are utilized as emissive layers in solution-processed OLED devices, are essential for their commercialization. Achieving balanced charge injection is challenging due to the wide bandgap between the HOMO and LUMO energy levels. This study examines the optical and photophysical characteristics of blue-emitting polymers to contribute to the understanding of the fundamental mechanisms of color purity and its stability during the operation of OLED devices. The investigated materials are a novel synthesized lab scale polymer, namely poly[(2,7-di(p-acetoxystyryl)-9-(2-ethylhexyl)-9H-carbazole-4,4'-diphenylsulfone)-co-poly(2,6-diphenylpyrydine-4,4'-diphenylsulfone] (CzCop), as well as three commercially supplied materials, namely Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), poly[9,9-bis(2'-ethylhexyl) fluorene-2,7-diyl] (PBEHF), and poly (9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) (F6PC). The materials were compared to evaluate their properties using Spectroscopic Ellipsometry, Photoluminescence, and Atomic Force Microscopy (AFM). Additionally, the electrical characteristics of the OLED devices were investigated, as well as the stability of the electroluminescence emission spectrum during the device's operation. Finally, the determined optical properties, combined with their photo- and electro-emission characteristics, provided significant insights into the color stability and selectivity of each material.

On the relationship between electrical and electro-optical characteristics in vertical cavity surface emitting lasers for chip scale Rb atomic clocks

We report on a comprehensive study of the electrical and electro-optical properties of 795 nm vertical cavity surface emitting lasers (VCSELs) designed for chip scale Rb atomic clocks. We highlight several key findings including the observation that the current flow at moderate bias levels comprises several parallel paths which are identified by an analysis of the I−V characteristic also confirmed by a numerical simulation. Resistance is a key parameter in any VCSEL. We analyze it in detail at all bias levels and find that above transparency, when the VCSEL enters the high injection regime, the current flow mechanism is modified significantly from an exponential to a power law characteristic. Consequently, resistance attains a nonlinear contribution which is quadratic in the spontaneous emission regime and quasi-linear above the threshold. This nonlinear contribution is not considered in common models. The optoelectronic properties are strongly correlated with the electrical characteristics what allow to explain several peculiarities of the VCSEL performance. We designed and fabricated the VCSELs according to the requirements of miniature Rb atomic clocks, including optimal operation at high temperatures. Their minimum threshold occurs at 363 K where they emit at 794.7 nm. The modal and polarization discrimination in the bias range where these VCSELs operate in practical miniature atomic clocks is well above 30 dB.