Aluminum Doping Concentration Research Articles

Over 10% efficient Cu2ZnSn(S, Se)4 Thin-Film cells prepared by aluminium doping

Cu2ZnSn(S,Se)4(CZTSSe) solar cell is of excellent development tendency because of lower pollution and outstanding power conversion efficiency(PCE). Yet, current PCE of CZTSSe is limited because of a high open-circuit voltage deficit, primarily put down to severe band tailing and carrier recombination. In this paper, absorber films were obtained by solution method and the influences of different aluminum doping concentrations on the properties of CZTSSe thin film cell were studied. Analysis about X-ray diffraction (XRD) and Raman spectroscopy confirms which Al has incorporated into CZTSSe thin film lattice and replaced Sn. Hall effect measurements reveal the improvement of carrier concentration on thin film absorber layer attribute to the formation of AlSn acceptor defects. Furthermore, X-ray photoelectron spectroscopy (XPS) reveals that Al enter into the CZTSSe lattice and Al is in the appropriate state of + 3 valence without generating additional harmful defects. More important, the generation of deep energy level defects and defect clusters associated with Sn were suppressed by replacing Sn with Al. Finally, the photovoltaic performance of different Al doped CZTSSe cells were characterized by conducting J-V and external quantum efficiency (EQE) tests. Remarkably, the CZTSSe solar cell with PCE as high as 10.59 % is obtained under a doping level of 6 % Al, which has an open circuit voltage of 522 mv. Compared with reference CZTSSe solar cells with an efficiency of 7.29 %, which indicates with improvement of 45 % in efficiency. Consequently, Al doping process is considered as a prospective tactic to elevate the PCE of CZTSSe solar cells.

Effect Annealing Temperature on Pure and Al-Doped Iron Oxide Thin Films for Formaldehyde Gas Sensing Application

The present study employs chemical spray pyrolysis to prepare pure and Al-doped α-Fe2O3 thin films with different aluminium concentrations. Subsequently, annealed at 450 °C and investigated the effect of annealing temperature on structural, morphological, optical, chemical and gas sensing properties. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) studies were adapted to examine the morphologies and microstructural properties of the α-Fe2O3-based thin films. All the films were polycrystalline with rhombohedral structure, and the (104) plane was confirmed to be the favoured orientation. Deposited thin films were seen to have agglomerated, superimposed sphere-like particles on their surfaces in AFM and FESEM micrographs. Raman spectroscopy analysis and XPS were used to examine the film’s symmetry and structural characteristics. The optical band gap of the deposited thin films is determined using a Tauc plot.Pure and Al-doped thin film’s formaldehyde sensing capability was examined based on aluminium (Al) doping concentration. The results of the experiments showed that the gas-detecting capabilities have been significantly enhanced by the optimal content of Al added to the α-Fe2O3 lattice.

Impact of aluminum doping on nonlinear absorption and ultrafast carriers dynamics of Al:CdO thin films

Al:CdO thin films with different aluminum doping concentrations were prepared via magnetron sputtering technique with various sputtering power. It is found that the band gap Eg of Al:CdO films gradually increases with the increase of Al doping concentration, while the crystallinity became poor at high doping concentration. The nonlinear absorption properties of the film were characterized by nanosecond Z-scan measurements. The Z-scan results show that the nonlinear absorption coefficient β of Al:CdO thin films could be effectively modulated by Al concentration, and the maximum of β (2 × 10−6 m/W) is achieved around 20 W sputtering power. The carrier dynamics of Al:CdO thin films were studied by femtosecond pump–probe measurements. The results show that the carrier relaxation lifetime, carriers absorption cross section and carriers refraction volume are larger in the high Al concentration film. The optical limiting properties of Al: CdO films were also studied. These results demonstrate that the Al:CdO film is a promising candidate for applications in all optical switches and laser devices.

The effect of RF plasma power on remote plasma sputtered AZO thin films

Aluminium-doped ZnO (AZO) thin films were deposited by remote plasma sputtering of a ZnO:Al2O3 98:2 wt% ceramic target in a pulsed DC configuration. The target power was kept constant at 445 W and the RF plasma power was varied between 0.5 and 2.5 kW. The as-deposited AZO thin films exhibited an optimum resistivity of 6.35 × 10−4 Ω·cm and optical transmittance of 92% at a RF plasma power of 1.5 kW. The thin film microstructure, chemical composition, and residual stress were investigated using SEM, RBS, XPS and XRD. Accurate determination of the chemical composition and correct interpretation of GIXRD data for AZO thin films are a particular focus of this work. The AZO layer thickness was 500–700 nm and Al content in the range of 2.3–3.0 at.%, determined by RBS. The AZO thin films exhibited a strong (002) preferential orientation and grain sizes between 70 and 110 nm. The (103) peak intensity enhancement in GIXRD is proven to be a result of the strong (002) preferential orientation and GIXRD geometrical configuration rather than a change in the crystallite orientation at the surface. XPS depth profiles show preferential sputtering of O and Al using a 500 eV Ar+ beam, which can be reduced, but not eradicated using an 8 keV Ar150+ beam. The preferential sputtering can be successfully modelled using the simulation software TRIDYN. A plasma power of 1.5 kW corresponds to a highly ionised plasma and various microstructural and compositional factors have all contributed to the optimum low resistivity occurring at this plasma power. The grain size exhibits a maximum in the 1.25–1.5 kW range and there is improved (002) orientation, minimising grain boundary scattering. The highest carrier concentration and mobility was observed at the plasma power of 1.5 kW which may be associated with the maximum in the aluminium doping concentration (3.0 at.%). The lowest residual stress is also observed at 1.5 kW.

Piezoresistive Thermal Characteristics of Aluminum-Doped P-Type 3C-Silicon Carbides

This study examined the temperature-related piezoresistance issues of p-type doped 3C-silicon carbide (3C-SiC) materials. Previously, we proposed piezoresistance temperature models that describe phenomena based on the ionization energies of materials oriented for high-temperature operations. This study aimed to determine the ionization energy as a function of the aluminum doping concentration of 3C-SiC. However, at the low-temperature region a drastic decrease in the piezoresistive coefficient was observed, and it was predicted to occur when materials possessing large impurity ionization energy are used under negative thermal strained conditions. This phenomenon is in contrast to the conventional piezoresistance factor P(N,T) that is based on narrow band-gap materials such as silicon or germanium; thus, it provides new insights into low-temperature piezoresistance phenomena.

Enhancement of optoelectronic properties of ZnO thin films by Al doping for photodetector applications

Abstract In the present study, pure and Al-doped ZnO thin films have been deposited on glass substrates using a cost-effective nebulizer spray technique. The structural, topographical, photoluminescence, and UV detector properties of ZnO thin films have been studied for various aluminium-doping concentrations. X-ray diffraction (XRD) studies confirmed the polycrystalline hexagonal structure plane with preferred orientation along (002) direction. The ZnO structural parameters like crystallite size, dislocation density, and strain showing considerable variation with aluminium doping. Atomic force microscope (AFM) images displaying spherical grains and the grain size is increasing with Al concentration. The energy dispersive X-ray (EDX) analysis displays the presence of Zn, Al, and O elements in the deposited thin films. The optical bandgap values are decreased with aluminium doping concentration and the lowest value was observed for the 1% Al doping. Photoluminescence (PL) spectra reveal a sharp emission peak at 390 nm and peak with the shoulder at 554 nm. The Responsivity, External quantum efficiency, and Detectivity of pure and doped samples are in the range of 0.22–0.38 AW-1, 70–123%, and 1.22 × 1010 to 1.70 × 1010 Jones, respectively. The better photodetection results are observed for the 1% Al-doped ZnO thin film which indicates it is a good candidate for photo-detector applications.

Optimization of Aluminium Doping Concentration in Titanium Dioxide Nanoparticles Photo Anode for Enhancing Efficiency of Dye-Sensitized Solar Cell

Well crystallized Aluminium (Al) doped Titanium dioxide (TiO2) nanoparticles with various doping concentration (0, 0.05[Formula: see text]M, 0.07[Formula: see text]M, 0.09[Formula: see text]M and 0.11[Formula: see text]M) were synthesized successfully by sol–gel route to develop the photo anode of Dye Sensitized Solar Cell (DSSC). Anatase crystalline nature of TiO2 nanoparticles was confirmed using X-ray diffraction (XRD) and Raman spectrophotometer. The Atomic Force Microscopy (AFM) was used to investigate the morphology of the photo anode (Al-doped TiO2 nanoparticles). The photovoltaic performance of the DSSC in terms of Current, Voltage and efficiency was investigated with a standard illumination of AM1.5G having an irradiance 100[Formula: see text]mW/cm2. Optimized values of Short Circuit Current density ([Formula: see text]), Open Circuit Voltage ([Formula: see text]) and efficiency ([Formula: see text]) obtained was 247.62[Formula: see text][Formula: see text]A/cm2, 359[Formula: see text]mV and 0.02456%, respectively for 0.07[Formula: see text]M Al doping concentration. Eco-friendly Eosin Y dye was used for sensitization of the photo anode. The optimized photovoltaic cell exhibits very good efficiency (80.05% more than the earlier reported work).

Infrared emission characteristic and microwave loss property of aluminum doped zinc oxide nanoparticles

Aluminum doped zinc oxide (AZO) nanoparticles with different doping concentrations were prepared by a simple one-step hydrothermal synthesis method. The crystal structure, morphology, infrared absorption, infrared emission and microwave loss properties of the AZO nanoparticles were analyzed in detail. With the increase of the aluminum doping concentration, the crystal plane spacing does not change much, while the grain size increases gradually, and the thickness of the flakes and the average size of the particles have no significant change. With the increase of the Al doping concentration, the infrared emissivity of AZO tends to decrease first and then increase, among which the AZO infrared emissivity with Zn-ion ratio of 95:5 is the lowest. The electromagnetic parameters of AZO with a mole doping ratio of 93:7 were carried out at a frequency range of 2–18 GHz, the real part (ε′) and imaginary part (ε″) of the complex permittivity varies between 4.3-4.5 and 0.2–0.4, respectively, the dielectric loss tangent (tanδ) varies between 0.04 and 0.09.

Solution-processable zinc oxide based thin films with different aluminum doping concentrations

Al doped zinc oxide (AZO) thin films are attempted to be formed on glass substrates via solution processing with 0, 0.5, 1, 2, 3, and 4 at% Al doping concentrations. Analysis of X-ray diffraction patterns and scanning electron microscopy micrographs indicate that the AZO thin films belong to the wurtzite hexagonal structure with (100), (002), (101), (102), (110), (103), (112) and (201) orientations, and show that the grain size of AZO thin films decreases with higher Al doping concentrations. Optical and electrical properties of the AZO thin films are characterized from using a UV/vis spectrometer and a four-probe measurement system, respectively. The AZO thin films obtained have a minimum sheet resistance of 30.41 Ω/sq for the dopant concentration of 1 at%, and a bandgap energy varying from 3.26 eV to 3.16 eV as the Al doping concentration increases from 0 to 4 at%. The maximum figure of merit value of 7.48 × 10 −3 (Ω/sq) −1 corresponds to the deposition of the AZO thin film with 2 at% Al doping. • Al doped ZnO thin films with a single phase of wurtzite hexagonal crystal structure successfully prepared. • Sheet resistivity approached to the lowest value with the doping concentration of 1 at%, which is comparable with other reports. • Maximum figure of merit corresponded to the AZO thin film with 2 at% Al doping.

Influence of Aluminum Compensation Effects in 4H-SiC on the Performance of VDMOS Transistors

The compensation of charge carriers is an important aspect to be considered in Aluminum doped areas in 4H-SiC. In this paper, a straightforward method has been found to implement compensation effects into a basic device simulation model and to improve the conformance of electrical measurement and simulation results. By implementing the compensation factors, which depend on Aluminum doping concentration, device simulation in combination with basic device cell structure can be used to create electrical characteristics that are in accordance with measured characteristics. This is a simple alternative for complex process simulation, taking into account physical effects like defects in the crystal structure. The method was used for simulation of lateral MOSFETS transfer characteristic as well as VDMOS blocking characteristic. Found compensation values were 80 % in the 1.5 ∙ 1017 cm-3 Al-doped channel region and 23% in the deep, 7.5 ∙ 1017 cm-3 Al-doped, shielding region.

Aluminum-doped ZnO thin films deposited on flat and nanostructured glass substrates: Quality and performance for applications in organic solar cells

Transparent conductive aluminum-doped zinc oxide (AZO) thin films were deposited on a flat and nanostructured borosilicate glass substrates by using DC-magnetron sputtering. The aluminum doping concentration was kept at 3.3 wt% and the film thickness (100–400 nm) was varied. The thin films were then annealed at 250 °C for 1 h in nitrogen and/or argon atmosphere, respectively. AZO thin films exhibited hexagonal wurtzite structure of ZnO with an intense (0 0 2) diffraction peak, indicating that they have c-axis preferred orientation. Optical transmittance was observed to be greater than 80% in the visible range for films deposited on both flat and nanostructured glass substrates. The lowest resistivity of 9.7 × 10−4 Ω cm was observed for AZO film of 400 nm thickness on flat glass substrate, annealed in Nitrogen atmosphere. The power conversion efficiency (PCE) of 0.27% and 2.24% were recorded for organic solar cell devices based on AZO deposited on nanostructured and flat borosilicate glass, respectively. In comparison with the latter, the PCE of ITO based device was recorded to be 3.17%. Due to their good optical and electrical properties, AZO thin films are promising candidates as transparent electrodes in organic solar cells.

Effect of aluminium doping concentration on microstructures, optical and electrical properties of ZnO thin films by spray pyrolysis technique

The effect of Al doping on a ZnO thin film, deposited on a glass substrate by spray pyrolysis under ambient atmosphere, is investigated. Zinc acetate and aluminum nitrate were used as precursors for Zn and Al ions, respectively. The Al-doped ZnO thin films, with Al doping contents of 0 at%(undoped), 1at.%, 2at.%, 3at.%, 4at.% and 5at.%, were deposited at 400 C. X-ray diffraction analysis showed that the undoped ZnO exhibited hexagonal wurtzite crystal structure with major diffraction peak along (002) plane and minor peaks of (101) and (103) planes. The relative intensities of the diffraction peaks and the crystallinity decreased with an increase in Al-doping concentration.Surface morphology of the films were investigated by Scanning Electron Microscope (SEM). The morphological analysis showed that the grain size decreased with higher doping concentration. The optical transmittance spectra of the films showed a high transmittance (higher than 80%) within the visible and near infrared wavelength region. The electrical properties were characterized by the four point probe technique. Undoped ZnO films exhibited the highest sheet resistance, while the 2 at% Al-doped ZnO exhibited minimum sheet resistance.

Calibration on wide-ranging aluminum doping concentrations by photoluminescence in high-quality uncompensated p-type 4H-SiC

Previous work has shown that the concentration of shallow dopants in a semiconductor can be estimated from the photoluminescence (PL) spectrum by comparing the intensity of the bound-to-the-dopant exciton emission to that of the free exciton. In this work, we study the low-temperature PL of high-quality uncompensated Al-doped p-type 4H-SiC and propose algorithms for determining the Al-doping concentration using the ratio of the Al-bound to free-exciton emission. We use three different cryogenic temperatures (2, 41, and 79 K) in order to cover the Al-doping range from mid 1014 cm−3 up to 1018 cm−3. The Al-bound exciton no-phonon lines and the strongest free-exciton replica are used as a measure of the bound- and free-exciton emissions at a given temperature, and clear linear relationships are obtained between their ratio and the Al-concentration at 2, 41, and 79 K. Since nitrogen is a common unintentional donor dopant in SiC, we also discuss the criteria allowing one to determine from the PL spectra whether a sample can be considered as uncompensated or not. Thus, the low-temperature PL provides a convenient non-destructive tool for the evaluation of the Al concentration in 4H-SiC, which probes the concentration locally and, therefore, can also be used for mapping the doping homogeneity.

Effect of aluminum doping concentration on optical, magnetic and microstructural properties of MnZnO thin films

Al doped MnZnO thin films have been successfully deposited via the gel route by varying concentration of Al between 1 and 3%. Identification of the chemical components of the films was done using Fourier Transform Infrared Spectroscopy (FTIR). The structural properties evaluated by using X-ray diffraction showed that the Al doped MnZnO films are amorphous and only film with 3% Al doping exhibits hexagonal wurtzite structure along a-axis orientation. The surface morphological studies from Scanning Electron Microscope (SEM) showed the nano-crystalline grains on the surface. Transmission among the wavelength range 300–900nm was found to be decreased with increase of doping percentage of Al. The optical band gap was decreased from 3.46 to 3.4eV when% of Al doping was increased till 2.5%. Further increase in Al percentage to 3% increased band gap. The hysteresis curves showed ferromagnetic behavior and magnetic properties were enhanced with increase in Al%.

Effect of doping concentration and temperature on the morphology, crystallinity and electrical conductivity of Al:ZnO nanostructured films grown from aqueous solution

Al-doped ZnO nanostructures were grown on glass substrate by hydrothermal method, in the temperature range of 70–95°C, from aqueous solutions of zinc nitrate he333xahydrate and aluminum chloride hexahydrate. Based on scanning electron microscopy, X-ray diffraction, micro-Raman spectroscopy and electrical measurement data, the effect of 2–6wt.% Al doping on the morphology, microstructure and electrical properties was investigated. The morphology and crystalline structure are strongly dependent on the Al-doping and growth temperature. When Al doping increases from zero to 2 and 4wt.%, the morphology changes from nanowires with higher optical phonon confinement, to combined morphologies including nanowires, nanoblades and transparent nanosheets. Lowering the temperature of the growth solution and/or increasing the concentration of aluminum dopant above 4wt.%, 1D (nanowires) and 2D (nanoblades and nanosheets) nanostructures collapse into an amorphous structure with totally changed morphology. Micro-Raman spectra and X-ray diffraction patterns confirmed the wurtzite structure with preferential c-axis growth direction of samples containing up to 4wt.% aluminum. The average crystallite size decreases continuously from 23.8 to 21.1nm with increasing the Al concentration from 0 to 4wt.%. The electrical conductivity of the obtained nanostructures significantly depends on the aluminum doping concentration. 2wt.% Al-doped ZnO nanostructured layer grown at 95°C showed the best electrical conductivity of 140.9Ω−1cm−1. The ambivalent role of aluminum, donor or acceptor, depending on doping concentration was highlighted.

Fluorescent P-Type 4H-SiC Grown by PVT Method

Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystal in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.

Hall scattering factors in p-type 4H-SiC with various doping concentrations

The Hall scattering factor (γH) in p-type 4H-SiC with various aluminum doping concentrations of 5.8 × 1014–7.1 × 1018 cm−3 was investigated from 300 to 900 K. γH was determined by comparing the Hall coefficient with the theoretical carrier concentration derived from acceptor and donor concentrations obtained from secondary ion mass spectrometry and capacitance–voltage measurements. γH decreased with increasing temperature or doping concentration; γH = 1–0.4 for the doping concentration of 5.8 × 1014 cm−3 and γH = 0.5–0.2 for the doping concentration of 7.1 × 1018 cm−3. The dependence might be caused by the anisotropic and nonparabolic valence band structure of 4H-SiC.

Donor-acceptor-pair emission in fluorescent 4H-SiC grown by PVT method

Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystal in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.

Effect of aluminum doping on a solution-processed zinc-tin-oxide thin-film transistor

The doping effect of aluminum (Al) on a solution-processed zinc-tin-oxide (Al-ZTO) film was examined. The solution processing temperature and aluminum doping concentration were optimized. The following optimal electrical properties with 0.0025 M Al doping at a processing temperature of 500°C were obtained; a mobility of 5.41 cm2/Vs, a current ratio of Ion/Ioff of 107, a threshold voltage of 2.46 V, and a subthreshold slope of 0.48 V/dec with better bias stability. Al doping into the ZTO TFTs improved the electrical properties and bias stability due to the control of free charge carriers without suppressive atoms.

Microwave dielectric properties of Al-doped ZnO powders synthesized by coprecipitation method

Al-doped ZnO (AZO) powders with different Al concentrations were synthesized by coprecipitation method. Crystal structural and dielectric properties of the powders as a function of aluminum doping concentration as well as annealing temperature were investigated. The XRD results reveal that Al atoms are doped into ZnO lattice successfully and all the samples are polycrystalline with a hexagonal wurtzite structure. The real part (ε′) and imaginary part (ε″) of the complex permittivity of the powders were carried out by a vector network analyzer in the microwave frequency range of 8.2–12.4 GHz. The results show that the ε′ and ε″ of the doped ZnO powders increase with the doping content and both of them are higher than that of the pure one. For the AZO powder with 7 mol% Al, both ε′ and ε″ increase firstly and then decrease with increasing annealing temperature.