Depletion Region Research Articles

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.

Nonlinear behaviors in back-gate effects of FDSOI MOSFETs at cryogenic temperatures

In this work, we systematically investigate the DC performance of fully depleted silicon-on-insulator (FD-SOI) MOSFETs at both room and cryogenic temperatures as low as 77 K. The influences of back-gate bias on normal and flip-well devices are measured and analyzed. Both types devices display non-linear behaviors when adjusting the back-gate voltage at cryogenic temperatures. Notably, the non-linear effects are more prominent in normal-well devices. The possible reasons are analyzed and verified by technology computer aided design simulation, suggesting that normal-well devices are more susceptible to the formation of depletion regions between the buried oxide layer and the well. This phenomenon disrupts the linearity of the back-gate effect. This research contributes to understanding and characterizing of the back-gate effects in cryogenic environments and holds potential for high-performance computing applications.

Classical Concept of Semiconductor Heterojunctions in the Approach to Nanohybrid Catalysts.

Recalling the well-established theory of heterojunction formation between two different semiconductors or a semiconductor and a metal can elucidate the remarkable catalytic properties of nanohybrid systems employed in thermal catalysis. Upon the creation of heterojunctions, involved nanoparticles or nanometer-sized thin films, as a result of their dimensions, may become entirely filled with space charges generated from the development of depletion or accumulation regions. This phenomenon dictates the nature of catalytic sites and consequently affects the catalytic activity of such nanohybrids. The following perspective presents this concept and examples of experimental results that substantiate its validity, along with an extremely effective tool, cold plasma deposition, for designing and realizing in a controlled manner the structure of nanohybrids with heterojunctions. This approach will undoubtedly broaden the view of the contemporary "alchemy" of nanocatalysts.

On the piezo-phototronic effect in heterojunction photodiode with type-II energy band: Simulation on complex incident light illumination

A photodiode, a semiconductor device, is designed to convert light into an electric current. The piezo-phototronic effect, arising from the interplay of semiconductor properties, piezoelectric polarizations, and photo-excitations, presents a promising avenue for enhancing photodiode performance. This research is dedicated to analyzing the impact of the piezo-phototronic effects on p-Si/n-ZnO heterojunction photodiodes when subjected to 365 nm illumination, a situation more intricate than the commonly studied 648 nm illumination. Employing numerical simulation methods, we systematically investigated the influence of varying ZnO and Si lengths on the piezo-phototronic effect, with a focus on the depletion region and neutral region current perspectives. Our findings reveal that adjusting these lengths can heighten sensitivity at low currents or lead to increased base currents. Additionally, the study delves into the effects of doping concentration, minority carrier lifetime, and mobility on device characteristics. This investigation contributes essential insights for a comprehensive understanding of piezo-phototronic effects and establishes a foundational framework for the design of industrial devices.

Precipitation of secondary Laves phases and its effect on notch sensitivity

AbstractThe precipitation of secondary Laves phases and its effect on notch sensitivity are systematically studied in Thermo-Span alloy. The results show that the precipitation peak temperature of secondary Laves phases is 925 °C. Below 925 °C, the volume fraction of secondary Laves phases increases with the rise of the temperature, and its morphology changes from granular to thin-film; above 925 °C, the volume fraction of secondary Laves phases shows an opposite trend to temperature, and its morphology changes from thin-film to granular. A detailed explanation through linear density (ρ) is provided that the influence of secondary Laves phases at the grain boundaries (GBs) on notch sensitivity depends on the coupling competition effect of their size, quantity, and morphology. Notably, the granular Laves phases are more beneficial to improving the notch sensitivity of the alloy compared with thin-film Laves phases. Granular secondary Laves phases can promote the formation of γ′ phases depletion zone to improve the ability of GBs to accommodate high strain localization, and effectively inhibit the crack initiation and propagation.

Heterogeneous integration photoferroelectrics for self-powered photoelectric detectors

The anomalous photovoltaic effect inherent in ferroelectric materials brings promising opportunities for self-powered photoelectric detectors. However, the photoelectric detection performances in photoferroelectrics are limited by the low photocurrent output due to the recombination and low separation ability of photogenerated carriers. This work proposes a heterogeneous integration technology for self-powered photoelectric detectors by designing a P-type/N-type/P-type (PNP) ferroelectric junction with sandwich structure, in which not only the photogenerated carrier separation is strengthened due to the enhanced polarization derived from the interface compressive stress, but also the carrier recombination is suppressed by the built-in electric field in the depletion layer. Thus, the photocurrent output in the PNP heterojunction is increased by more than seven times at 0 V bias compared with N-type ferroelectric film and exhibits excellent responsivity and detectivity. The temperature stability for repeatable time-resolved self-powered photocurrent demonstrates applicability in high temperature environments. This work provides a feasible strategy for high-performance self-powered photoelectric detectors by heterogeneous integration in photoferroelectrics, promoting ferroelectric photonic applications.

Interface Characterization of Graphene‐Silicon Heterojunction Using Hg Probe Capacitance–Voltage Measurement

AbstractInvestigating the intrinsic properties of the Schottky interface between graphene and 3D bulk silicon is crucial. However, the semiconductor technology introduces extra doping and defects in graphene, which significantly disturbs the property of the graphene‐silicon interface. Here, the interface parameters of graphene/n‐Si heterojunction are derived by the damage‐free Hg‐probe capacitance–voltage measurement. Due to its low‐density states, the Fermi level of graphene can be pushed upward, which results in a lower Schottky barrier height (ΦB0) of Hg/graphene/n‐Si (HGS) heterostructure than that of Hg/n‐Si (HS) structure. Additionally, the series resistance (Rs) of HGS becomes lower than that of HS, which can be attributed to the narrowed depletion layer width (WD) and the decreased interface state density (Nit). Furthermore, the frequency characteristic is also investigated. Because of the weak interface state charge trapping–detrapping process and the decreased Nit at high frequency, electrons will accumulate in graphene, and the Fermi level will be pushed up. Hence, the ΦB0 and Rs will decrease with increasing frequency. This study contributes to a deep understanding of the graphene/silicon heterojunction interfaces, which is crucial for designing and optimizing the new electronic and optoelectronic devices based on 2D/3D heterostructure.

THz Wave Power Enhancement Using a Microstrip Line-Based Combiner Integrated with Arrayed UTC-PDs

Advancements in semiconductor devices, such as Uni-travelling-carrier photodiodes (UTC-PDs), have played a significant role in the development of Terahertz communication technology. However, the persistent challenge is the limited output power from a single UTC-PD required for practical transmission distances. To enhance the output power, we propose and demonstrate a novel Terahertz wave power combining technique using a photomixer device comprising two arrayed UTC-PDs monolithically integrated with a microstrip line-based 2 × 1 Wilkinson power combiner and a patch antenna on a Silicon Carbide (SiC) substrate at 300 GHz. When the two UTC-PDs are activated at photocurrents of 8 mA and 10 mA, the device exhibits a 7.3 dB increase in power relative to the power obtained when only the 8 mA UTC-PD is activated, and a 4.4 dB increase in power relative to the power obtained with the 10 mA UTC-PD. This implies that power can be enhanced by a factor of N2 if the photocurrent is multiplied by N. Additionally, we demonstrate that the UTC-PD output saturation depends on the space charge effect, which modulates the electric field in the depletion region and results from critical charge density of about 80 kA/cm2 for the device in this work.

Effect of AZO seed layers on the ultraviolet photoresponse of Ag/ZnO NRs Schottky junctions

Al-doped ZnO (AZO) thin films with different layers were prepared by sol-gel method. The SEM, XRD and AFM for three layers thin films demonstrates high crystal quality and low roughness. ZnO nanorods arrays (NRs) with different AZO seed layers were fabricated using hydrothermal process, and the effect of AZO seed layers on the structural, optical, and electrical characteristics was investigated. When there are three AZO seed layers present, ZnO NRs exhibit fewer surface states, smaller interface charge transfer resistance (Rce = 6.1 × 103Ωand Rct = 6.6 × 106Ω), longer carrier lifetimes (τe = 4.0 ms), higher carrier concentration (ND = 4.73 × 1019 cm−3), and narrower depletion region width W = 3.1 nm. Under weak UV light 381 nm (5.68 mW/cm2) at a bias −0.5 V, Ag/ZnO NRs Schottky devices with three AZO seed layers display a comparatively strong responsivity 34.64 mA/W. Appropriate AZO seed layers are favorable for highly efficient ZnO NRs-based photoelectric conversion devices.

Defect-enabled room-temperature acetone gas sensors based on Zn-doped cauliflower-like bismuth oxide

Metal oxide-based gas sensors have promising advantages, such as low cost and high sensitivities, but the high working temperature (150°C–300 °C) hinders their practical applications. Herein, this study demonstrated a Zinc (Zn)-doped approach to achieve defect-enabled room-temperature acetone gas sensors based on bismuth oxide (Bi2O3) thin film. Through a simple chemical bath deposition method, the varying substitutional doping of zinc (2 wt% to 8 wt%) can induce the morphological transformation of Bi2O3 nanosheets to a cauliflower-like nanostructure, leading to enhanced surface area and active sites. The incorporation of Zn ions can result in oxygen vacancies in the Bi2O3 lattice and the rising of the depletion layer, facilitating the interaction toward acetone molecules at ambient temperatures, leading to an increment of response ∼6. The Zn-doped cauliflower-like Bi2O3 electrode exhibits a superior sensing performance of acetone gas with a low detection limit of 1 ppm and high stability over 90 days. This work underscores the potential of controlled doping of Zn for oxygen vacancy-riched Bi2O3 thin film as a promising room-temperature acetone gas sensor, offering new avenues for the detection of hazardous gases with improved sensitivity.

Contactless edge for edge recombination optimization in solar cell

AbstractAs the conversion efficiency of solar cell approaching its theoretical limits, reducing the power loss during the collection and transmission process is a promising way to improve the performance of solar cell. Cleaved edges create recombination centers, causing up to 0.8%abs (absolute efficiency) of power loss or even more for 156 × 156 mm silicon solar cell. Due to the complexity of edge passivation technique, alternative methods are desired. This article proposes a method to minimize this problem. It is found that most of the recombination current of edge comes from the recombination near the contact and the space charge region (SCR). As a result, keeping the cleaved edge a certain distance away from the contacts and SCR can improve performance effectively. On the other hand, contactless edge can reduce the recombination from the SCR without extra manufacturing difficulty. The results indicate the edge recombination loss can be reduced to less than 0.4%abs after the distance is optimized appropriately.

Molecular Diodes Induced by a Schottky Barrier with a Gold-Silicon Doped Electrode.

To create complementary metal oxide semiconductor compatible molecular devices, more insights into the electrode property regarding its metal/semiconductor doping level and creating a functional molecular device are required. In this work, we constructed an EGaIn/alkanethiol/Au-Si molecular diode (with a rectification ratio R of 50.70) induced by Schottky barriers within a gold-silicon doped electrode instead of the functional property of molecules. The relationship between the rectification ratio and the number of methylene units in alkanethiol was analyzed, revealing a gradual increase in the ratio from 3.33 for C6H14S to 50.70 for C16H34S. The rectification ratio of the junction is well modulated by the temperature due to the change in the Schottky barrier. Such a mechanism is explained by the energy band diagrams of the surface space charge region and a combination of density functional theory and Keldysh-Green formalism calculations.

Investigation of Electrical and Dielectrically Properties of a Novel Structure of PANI-PPy--GO-MWCNTs Composite/MnO2/Fe3O4/n-Si Structure

We investigated here the electrical properties of the novel structure of PANI-PPy-GO-MWCNTs composite/MnO2/Fe3O4/n-Si. This structure has not been addressed in literature before, the manufacture of this novel structure is carried out using a simple technique. So, we introduce here a novel structure with a simple method of manufacture. The imaginary part of modulus M″ has two behaviors, the first behavior at high and low frequency and the second behavior at mid frequency, so the M″ gives two contrarian behaviors, The M″ is a strong function of frequency and we can change the behavior of M″ by change of frequencies. The Col—Col diagram of modulus has ideal figures at some voltages including two semicircles of grains and grain boundaries. The imaginary part of impedance Z″ vs frequency creates peaks, the peaks shift toward the low frequencies. The novel here the Z″ has positive and negative values, despite the Z″ should have negative values only. The real part of impedance Z″ keeps on without change at high frequencies and splits for all temperatures at low and mid frequencies. Some electrical properties such as barrier height ɸb,Wd the width of the depletion layer, Nss the density of states, and acceptor carrier concentration Na were obtained by C—V2. All these parameters were strong functions of frequency.

Novel superjunction Fin-based NiO/β-Ga2O3 HJFET with additional surface drift region channels for record-high performance

—In this paper, a novel superjunction fin-based NiO/β-Ga2O3 heterojunction field-effect transistor (SJ Fin-HJFET) is proposed and studied by simulations. Compared with the conventional Ga2O3 SJ FinFET, Ga2O3 SJ Fin-HJFET can generate surface conduction channels instead of depletion zones near the p-n junction interface in the SJ drift region. The additional surface conduction channel significantly improves the specific on-resistance of the SJ Fin-HJFET (from 1.091 mΩ cm2 to 0.397 mΩ cm2, reduced by 63.6 %) and dramatically improves the Baliga figure of merit (BFOM, form 11.75 GW/cm2 to 32.28 GW/cm2) at the same breakdown voltage (3580 V). The effect of different conduction band offset (ΔEC) on the performance of the SJ Fin-HJFET is also investigated. The simulation results show that the on-resistance advantage of the SJ Fin-HJFET applies to a wide range of ΔEC, exhibiting strong applicability and stability. These results indicate that the SJ Fin-HJFET has record-high performance and promising application prospects.

Prospects of silicide contacts for silicon quantum electronic devices

Metal contacts in semiconductor quantum electronic devices can offer advantages over doped contacts, primarily due to their reduced fabrication complexity and lower temperature requirements during processing. Some metals can also facilitate ambipolar device operation or form superconducting contacts. Furthermore, a sharp metal–semiconductor interface allows for contact placement in close proximity to the active device area avoiding damage caused by dopant implantation. However, in the case of gate-defined quantum dots in intrinsic silicon, the formation of a Schottky barrier at the silicon–metal interface can lead to large, nonlinear contact resistances at cryogenic temperatures. We investigate this issue by examining hole transport through metal oxide-semiconductor transistors with platinum silicide contacts on intrinsic silicon substrates. We extract the contact and channel resistances as a function of temperature and improve the cryogenic conductance of the device by more than an order of magnitude by implementing meander-shaped contacts. In addition, we observe signatures of enhanced transport through localized defect states, which we attribute to platinum clusters in the depletion region of the Schottky contacts that form during the silicidation process. These results showcase the prospects of silicide contacts in the context of cryogenic quantum devices and address associated challenges.

Microstructure evolution during oxidation of protruded NiCoCrAlYTa-Al2O3 abrasive coating produced by vacuum infiltration sintering

In this paper, protruded NiCoCrAlYTa-Al2O3 abrasive coatings were prepared by vacuum infiltration sintering, and the effect of the filler metal content on the microstructure before and after oxidation is investigated. The results show that, the Al2O3 grits are bonded to the coating matrix by a layer of Y-Al-O compound, and various types of G-phase are presented depending on the locations. Adjacent to the G-phase, larger γ' phase and γ/γ' eutectics are presented due to the expel of Al during the formation of G-phase. With the increase of the filler metal content, G-phase precipitation and the Si penetration depth into the single crystal superalloy substrate increase. After 1000 °C/100 h oxidation, the Y-Al-O intermediate layer between Al2O3 grits and the coating matrix is little changed, with an additional thermally grown oxide (TGO) layer between the Y-Al-O layer and the coating matrix presented. The selective oxidation of Al and Cr facilitates the formation of G-phase layer underneath the oxide film, and the rapid diffusion of Ti and the selective oxidation of Al yields the formation of γ' depletion region adjacent to the G-phase and on coating surface without Al2O3 grits.

Symbolism and Aesthetics: Analyzing Mughal Motifs in Art and Architecture

Spanning from 16th to 18th of imperial rule in the Indian subcontinent, the Mughal Empire is an indelible mark on artistic expression through its meticulous cultivation of motifs in various mediums, including art, architecture, manuscript illumination, textiles and decorative arts. This paper examined the symbolism reflected in the Mughal art and architecture. Through a multidisciplinary approach drawing from art history, cultural studies and material culture analysis, this study examined the diverse typologies of Mughal motifs, which included the study of flora and fauna imagery on Mughal monuments, illustrated manuscripts, textile and costumes. By analyzing their aesthetic qualities, symbolic meanings attributed to floral motifs and historical contexts, this research seeks to unravel the complex layers of cultural synthesis and exchange that characterize Mughal art. Through a comprehensive exploration of primary sources, scholarly literature and visual analysis, this paper examined the motifs in shaping the artistic identities, cultural narratives and aesthetic sensibilities in the Mughal Empire and beyond.

Double-diode model carrier lifetime-based internal recombination parameter analysis and efficiency prediction of crystalline Si solar cells

With the continuous and significant advancements in the performance of crystalline silicon (c-Si) solar cells, an effective method for a detailed analysis of the efficiency loss factors is increasingly important. Specifically, a detailed analysis of recombination parameter (J0) is crucial for devising strategies to approach the theoretical efficiency limit. In this study, we propose an analysis method that utilizes minority carrier lifetime based on the double-diode model and predicts the performance efficiency of c-Si solar cells. The analysis, conducted through the p-PERC structure, examines the contributions to J0 from different recombination areas. The advantages of this method include: (i) its relative simplicity and reliance on non-destructive analysis techniques; (ii) its capability to extract internal recombination parameters, such as J0,total emitter, J0,rear, and J02, from a fully assembled solar cell with metal contacts. Furthermore, this method serves as a diagnostic tool to identify the sequence in which parameters should be adjusted to enhance solar cell efficiency effectively and to pinpoint areas within the solar cell that significantly limit performance efficiency. Using this method, the diagnosis of the p-PERC cell revealed that the main cause of performance limitation was the emitter in the front region. The carrier lifetime analysis showed that for overcoming cell performance limitations, it is more effective to design process improvements in the following order: i) front emitter region (J0,em), ii) space charge region (J02), iii) rear surface region (J0r).

Ultrathin WO3 Nanosheets/Pd with Strong Metal-Support Interactions for Highly Sensitive and Selective Detection of Mustard-Gas Simulants.

Exposure to mustard gas can cause damage or death to human beings, depending on the concentration and duration. Thus, developing high-performance mustard-gas sensors is highly needed for early warning. Herein, ultrathin WO3 nanosheet-supported Pd nanoparticles hybrids (WO3 NSs/Pd) are prepared as chemiresistive sulfur mustard simulant (e.g., 2-chloroethyl ethyl sulfide, 2-CEES) gas sensors. As a result, the optimal WO3 NSs/Pd-2 (2 wt % of Pd)-based sensor exhibits a high response of 8.5 and a rapid response/recovery time of 9/92 s toward 700 ppb 2-CEES at 260 °C. The detection limit could be as low as 15 ppb with a response of 1.4. Moreover, WO3 NSs/Pd-2 shows good repeatability, 30-day operating stability, and good selectivity. In WO3 NSs/Pd-2, ultrathin WO3 NSs are rich in oxygen vacancies, offer more sites to adsorb oxygen species, and make their size close to or even within the thickness of the so-called electron depletion layer, thus inducing a large resistance change (response). Moreover, strong metal-support interactions (SMSIs) between WO3 NSs and Pd nanoparticles enhance the catalytic redox reaction performance, thereby achieving a superior sensing performance toward 2-CEES. These findings in this work provide a new approach to optimize the sensing performance of a chemiresistive sensor by constructing SMSIs in ultrathin metal oxides.

Carrier Recombination in Nitride-Based Light-Emitting Devices: Multiphonon Processes, Excited Defects, and Disordered Heterointerfaces.

We study recombination processes in nitride LEDs emitting from 270 to 540 nm with EQE ranging from 4% to 70%. We found a significant correlation between the LEDs' electro-optical properties and the degree of nanomaterial disorder (DND) in quantum wells (QWs) and heterointerfaces. DND depends on the nanoarrangement of domain structure, random alloy fluctuations, and the presence of local regions with disrupted alloy stoichiometry. The decrease in EQE values is attributed to increased DND and excited defect (ED) concentrations, which can exceed those of Shockley-Read-Hall defects. We identify two mechanisms of interaction between EDs and charge carriers that lead to a narrowing or broadening of electroluminescence spectra and increase or decrease EQE, respectively. Both mechanisms involve multiphonon carrier capture and ionization, impacting EQE reduction and efficiency droop. The losses caused by these mechanisms directly affect EQE dependencies on current density and the maximum EQE values for LEDs, regardless of the emission wavelength. Another manifestation of these mechanisms is the reversibility of LED degradation. Recombination processes vary depending on whether QWs are within or outside the space charge region of the p-n junction.