Ga Doping Concentration Research Articles

Interesting UV and visible photodetection properties of GZO‐based device

AbstractThe aim of this study is to investigate the performance of chemically deposited Ga doped ZnO (GZO) thin film for enhanced UV and visible light detection. Transparent thin film was grown on glass substrates by a spray pyrolysis technique. The Ga doping concentration was maintained at 1 at.% in the solution. The influence of gallium concentration in zinc oxide (ZnO) films on structural, morphological, electrical, and optical properties was studied.Measurements of the photoconductivity were performed by DC electrical tool under visible and UV illuminations. Obtained results reported in this study on the performances of the fabricated GZO based device reveal that the photoresponse, rapidity, photosensivity, responsivity, detectivity, and reproducibility of the device are very interesting in photodetection, especially in UV wavelength domain. We notice that the device has a good responsivity as compared to detectors fabricated using other techniques, with a rather good repeatability. Furthermore, the electronic conductivity mechanism is modeled as an ohmic one.

Bright solid-state luminescence and high-temperature resistance of Ga-doped carbon dots with ultra-wideband white emission for light-emitting diodes.

Fluorescent CDs tend to undergo solid-state aggregation quenching in powder form. This is caused by the stacking of π-π conjugate structures and excessive resonant energy transfer. Moreover, various forms of N play an important role in white CDs suitable for LED applications. White, single-component, non-N-doped CDs have never been reported for LED application. In this study, to overcome this limitation, we developed Ga-doped CD powders containing no N element that exhibit ultra-wideband white emission in the range of 420-800 nm for LED applications and were able to resist solid-state aggregation quenching. Furthermore, the Ga-doped CD powders demonstrated excellent luminescence stability under high temperatures. Another strength of the Ga-doped CD powders is their large Stokes shift, where the peak center of white emission shifts from 550 nm to 650 nm under 365 nm excitation as the Ga doping concentration is adjusted from 0.05 to 0.6 (Ga : H2O, mass ratio). The full width at half-maximum can reach 262 nm. Additionally, the Ga-doped CD powders exhibit good luminescence stability under long-time exposure to an air atmosphere. Their luminescent intensity retained 70%-74% of the initial values even after being left in natural placement for 100 days. Moreover, the Ga-doped CDs demonstrate afterglow features.

Green hydrothermal synthesis of Ga doping derived 3D ZnO nanosatellites for high sensitive gas sensors

A green hydrothermal synthesis methodology is employed for the synthesis of Ga3+ doped ZnO 3D nanosatellite structures. XRD technique exposed the hexagonal wurtzite type crystal structure of the 3D Ga3+ doped ZnO nanostructures. Ga3+ induced 3D morphology evolution in accordance to Ga doping concentration is realized via. the FESEM images. The FESEM images indicated one sided capped rod like structures (50–250 nm) in pristine ZnO, whereas 3D satellite kind of morphology (>500 nm) was observed in 5% Ga3+ doped ZnO structures. TEM images revealed physical specifications of 3D nanosatellite structures exposing the central rod of 500 nm length & 250 nm in width and the branch rods grown vertical to the central rod of length 300 nm and width of 50 nm. Further, optical absorbance and photoluminescence spectra confirmed the electron rich state of ZnO with Ga3+ doping. The gas sensing performance has shown selectivity toward CO gas at a working temperature of 250 ⁰C. High CO sensing was recorded for 5% Ga3+ doped ZnO 3D nanosatellites with attractive sensing characteristics such as good response, fast response time & fast recovery time.

Hydrothermal growth and ultraviolet sensing performance of well-aligned Ga-doped ZnO nanowire arrays

Herein, gallium (Ga)-doped zinc oxide (ZnO) nanowire arrays (GZNWAs) with different Ga doping concentrations (Ga/Zn = 0–4 atom%) were grown on the interdigital patterned fluoro-doped tin oxide glass substrates by a hydrothermal technique, their crystalline structure, morphology and ultraviolet (UV) sensing performance were focused on investigating. The results showed that all the as-grown samples were hexagonal wurtzite structure of ZnO. When the Ga doping concentration was below 4%, well-aligned GZNWAs were achieved. Furthermore, five UV photodetectors (PDs) were prepared using the GZNWAs as photoactive layers, all the devices were found to be excellent responses towards 365 nm light. Among these devices, the GZNWAs UV PD (1% Ga) maintained the optimal performance, its responsivity, sensitivity, detectivity, external quantum efficiency, response time and decay time were 72.8 A/W at 5 V, 747.8 at 0 V, 5.5 × 1012 Jones, 2.5 × 104%, 10.6 s and 45.6 s, respectively.

Effect of Ga doping on microstructure, morphology, optical and electrical properties of spray deposited CdO thin films

Cadmium oxide (CdO) and gallium (Ga) doped CdO thin films were fabricated successfully onto glass substrate at 400 °C temperature by spray pyrolysis technique and the effect of Ga on microstructure, surface morphology, optical, electrical and Hall effect properties of CdO thin films have been revealed and discussed. X-ray diffraction results indicate that all films are polycrystalline and possess cubic crystal structure. The SEM images reveal that the surface morphology of CdO changes remarkably with increasing Ga doping concentration. EDX investigation confirms the presence of cadmium (Cd), oxygen (O) and gallium (Ga) elements in the deposited films. The optical transmittance of CdO increases continuously with Ga doping up to 3% and then decreases onwards within the same wavelength region. The optical band gap initially increases from 2.47 eV to 2.53 eV, and Urbach energy decreases from 0.55 eV to 0.50 eV when the doping of Ga varies from 0 to 3%. Thereafter, the extinction coefficient, refractive index and energy dissipation factor shows reverse relation above 3% doping of Ga. The electrical resistivity of CdO thin film has been found 5.79 × 10−4 (ohm-cm) and which reduces to 1.23 × 10−4 (ohm-cm) for 3% Ga doping. The temperature dependent electrical resistivity data of deposited films shows that the films possess poor metal-like behaviour. Results of Hall Effect measurement notifies that the carrier of the films is n-type, and Ga doping changes the Hall mobility & carrier concentration of CdO films significantly. The obtained figure of merit of all films is higher than 1.0% Ω−1 and the maximum FOM was found for 3% (8.28 %Ω−1) Ga doped CdO films.

Doping Concentration Influenced Pyro‐Phototronic Effect in Self‐Powered Photodetector Based on Ga‐Incorporated ZnO Microwire/p+‐GaN Heterojunction (Advanced Optical Materials 2/2022)

The influence of the pyro-phototronic effect on a self-powered photodetector, composed of Ga-incorporated ZnO microwire (ZnO:Ga MW) and p+-GaN layer, was studied systematically by Mingming Jiang, Xiaosheng Fang, Caixia Kan, and co-workers (see article number 2101851). Varying the Ga-doping concentration in ZnO:Ga MWs, the pyroelectric current and photovoltaic current of photodetectors can be tuned, and the variation is attributed to the increased rate of photogenerated temperature and narrowed depletion layer.

Structure and Optical Properties of Cdse:Ga Thin Films Prepared by Thermal Evaporation Method

Cadmium Selenide (CdSe and CdSe:Ga) alloy has been prepared successfully in an evacuated quartz tube at a pressure (10−2 Torr). The structure of the CdSe alloy (powder) was tested by X-ray diffraction (XRD) and found as a polycrystalline (hexagonal) structure. CdSe and CdSe: Thin films have been deposited with a thermal evaporation process on the glass and Si substrates. The aim of this kind of study was to determine the ultrastructural morphology and optical properties of pure CdSe and Ga doped films produced using a method of thermal evaporation. The effect of Gallium on the structural and optical properties of CdSe thin film were doped at 0, 1, 3 and 5%. For all Ga doping ratios, the structural features such as the size of the grain and the micro strain of the thin film have been clarified with XRD technique and XRD pattern. The chosen orientation (002) for all prepared film has been polycrystal structures (hexagonals). With an increase in Ga from 37,54 to 21,37 nm, the grain volume decreases. AFM and SEM were used to study the morphology and surface roughness of the CdSe pure and doping films. All films were homogeneous with a characteristic spherical grain size depending on Ga concentration. The roughness of the films increases with the increase of Ga dopant. UV-Visible spectra photometer is used to investigate the visible properties such as absorption, absorption coefficient and energy gaps in thin films. The absorption value subsequently increased with Al doping concentration of localized states in the band gap of the films increases with the increasing of Al dopant, where optical energy gap values decreased with increasing the proportion of the doping in the range between 1.74 and 1.62. The grain size for pure and Ga- doped CdSe of thin films were decreased with Ga ratios. The absorption coefficient determined depends on photon energy incident (hv), the energy gap of the semiconductor as well as the form of transitions. In conclusions, CdSe and CdSe:Ga were successfully prepared from pure elements Cd, Se and Ga. XRD patterns showed the CdSe and CdSe:Ga films are polycrystalline of hexagonal structure directions by Ga doping that orientated a peak became less intensity from undoped CdSe film. The XRD patterns and AFM measurements of Ga-doped and undoped CdSe thin films agree with each other of the grain size within nanocrystal range and decrease as Ga doping concentration increases. AFM images indicate that the increasing in Ga doping that showed smooth surface films compared to the CdSe films. The optical bands gaps of the films have a direct band transition and slightly decreased with the increasing Ga doping.

Wide range variation of resonance wavelength of GaZnO plasmonic metamaterials grown by molecular beam epitaxy with slight modification of Zn effusion cell temperatures

The innovative growth condition of heavily Ga-doped ZnO (GaZnO) plasmonic metamaterials is reported in this article. GaZnO epilayers are deposited by molecular beam epitaxy (MBE) with small variation of Zn effusion cell temperatures. The variation of Zn effusion cells temperatures are 330, 335, and 340 °C corresponding to Ga doping concentration 6.8, 6.3, and 3.2 at%, respectively, which are obtained from the measurements of energy-dispersive X-ray spectroscopy (EDX). Temperatures of Ga effusion cell and sapphire substrate are fixed at 735 and 250 °C in the growth. Hall effect measurements exhibiting free electron concentration of all samples approach 1021 cm−3. The lowest strain/stress (0.08%/0.34 GPa), the largest crystalline size (47.5 nm), the highest Hall mobility (30.1 cm2/Vs), and the lowest material loss of GaZnO epilayers are observed in Ga doping concentration 6.3 at% sample. Statistical analysis of root mean square (RMS) surface roughness declines from 3.1 to 1.74 nm in the atomic force microscope (AFM) measurements when the doping is increased from 3.2 to 6.8 at%. Wide range variation of plasmonic resonance wavelength from 1333 to 1515 nm with the raise of Ga doping concentration is acquired through the analysis of spectroscopic ellipsometry measurements. Slight variations of Zn effusion cell temperatures in the range of 330–340 °C bring about efficient and drastic change of Ga doping concentration as well as wide range variation of plasmonic resonance wavelength (1333–1515 nm) for the applications in fiber-optic communication.

Formation of a Diffusion Barrier-Like Intermetallic Compound to Suppress the Formation of Micro-voids at the Sn-0.7Cu/Cu Interface by Optimal Ga Additions

Kirkendall micro-voids observed within ϵ-Cu3Sn or at the bulk Sn solder/Cu interface are undesirable imperfections in solder joints in electronic interconnections that significantly decrease the reliability of the joint. Recent studies have shown that micro-alloying could alter these interfacial reactions and improve the mechanical properties. In this study, we investigated the Cu-Ga-Sn phase equilibria at 200°C and the interfacial reactions between Cu substrate and Ga-doped Sn-0.7Cu solders with doping levels of 1.0, 2.0, and 3.0 wt.%. The assembled diffusion couples were isothermally annealed at 200°C for different time periods. The results showed that the thickness of the typical Cu-Sn IMCs (η-Cu6Sn5 and ϵ-Cu3Sn) progressively decreased along with the formation of the γ-Cu9Ga4 phase as the Ga-doping concentration was increased. The η-Cu6Sn5 and ϵ-Cu3Sn were completely suppressed and substituted by the γ-Cu9Ga4 phase when the Ga-doping concentration was 3 wt.%. More interestingly, the γ-Cu9Ga4 was the only IMC formed at the Sn-0.7Cu-3.0 Ga/Cu interface even when aging at 200°C for up to 1000 h, implying that the undesired defectiveness of Kirkendall micro-voids is possibly prevented by controlling the formation of the interfacial phase.

Synthesis of Gallium-Doped Zinc Oxide (GZO) Nanoparticles for GZO/Silver Nanowire Nanocomposite Transparent Conductive Electrodes

Gallium (Ga)-doped zinc oxide nanoparticles (GZO-NPs) have been synthesized using a heating-up method. The Ga doping concentration strongly affected the particle size, distribution, and bandgap energy of the GZO-NPs. When the Ga concentration was increased from 0% to 5%, the average size of the GZO-NPs decreased from 57 nm to 16 nm while the bandgap increased from 3.14 eV to 3.26 eV. On further increase of the Ga content to 7% and 9%, the particle size increased while the bandgap narrowed. The GZO-NPs synthesized with 5% Ga showed the best uniformity and smallest average diameter of approximately 16 nm. The GZO-NPs with 5% Ga were applied to reduce the mechanical contact between the AgNWs in GZO/silver nanowire (AgNW) composite for application as a transparent conductive electrode, yielding RSH = 18.1 Ω/□, T = 77.8% at 550 nm, and σDC/σOp = 77.53. These results indicate that such GZO-NPs are a very promising nanocrystalline ink precursor for printing thin films for application in nanocomposite transparent conductive electrodes.

Enhanced Electrical Mobilities of Laser Annealed Ga Doped ZnO Thin Films.

In this study, Ga-doped ZnO thin films were prepared, and their potential for transparent conducting oxide applications was assessed. To increase the electrical mobility and reduce the resistance of Ga-doped ZnO thin films, CO₂ laser annealing was employed. Recently, the use of transparent conducting oxides (TCOs) have increased, particularly ZnO-based TCOs have been intensively investigated for display applications. To enhance the electrical and optical properties of ZnO thin films, Ga was used as a dopant. First, Ga-doped ZnO thin-film precursors were prepared by the sol-gel method. Subsequently, Ga-doped ZnO thin films were coated on glass substrates by spin coating. Electrical furnace treatment and rapid thermal annealing were employed to obtain and anneal a wurtzite ZnO based structure. The electrical and optical properties of the annealed thin films were optimized by varying the Ga doping concentration. Via Ga doping and optimized laser annealing, the resistivity of the ZnO film could be decreased from 16.32 Ω· cm to 0.45 Ω·cm; notably, the transmittance was similar (85%) in the 380-800 nm range. The transmittance properties of the films are not presented in this paper. Moreover, after an optical CO₂ laser annealing process, the conductivity of the films improved by more than 40 times. Furthermore, the electrical properties (mobility, resistivity, and bulk and sheet concentrations) of the CO₂-laser-annealed Ga-doped ZnO thin films were optimized.

Optimization of Gallium concentration to improve the performance of ZnO nanopowders for nanophotonic applications

This study reports the effects of gallium concentration on the properties of doped zinc oxide nanopowders. Both pure and gallium doped zinc oxide (GZO) nanoparticles were prepared via a simple and effective sol-gel method. The structural, morphological and optical properties of synthesized GZO nanopowders were investigated using different characterization methods such as X-ray diffraction, Raman, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, UV–Vis diffuse reflectance spectroscopy, Transmission electron microscopy, Photoluminescence spectroscopy, X-ray and ion-beam-induced luminescence (IBIL) measurements. Firstly, in the presence of Ga ions in the host the purity of synthesized sample was evaluated by X-ray diffraction analysis. X-ray photoelectron spectroscopy confirmed the presence of bonding states of Zn, O, and Ga on the surface of powders. Raman spectroscopy analysis showed that the increase of Ga content upper than 1 at.% leads to an increase in the number of defects in the ZnO lattice. Field emission scanning electron microscopy (FESEM) confirmed that the uniform integration of spherical and hexagonal rod shape particles can be found in the doped samples. According to FESEM images, the particle size of prepared nanopowders increased from 101 to 200 nm by increasing in the Ga doping concentration. The photoluminescence, X-ray and ion beam induced luminescence results of the pure and doped ZnO powders revealed novel blue-green emission band from 400 up to 550 nm at room temperature. Optical and structural studies confirmed the optimized Ga concentration is 1 at.%.

Gigahertz acoustic vibrations of Ga-doped ZnO nanoparticle array

In this work, we present an experimental study on the acoustic vibrations of ZnO nanoparticles array with different concentration of Ga dopings by using femtosecond pump-probe technique. The Ga-doped ZnO (GZO) nano-triangle particles with the sizes of 190, 232 and 348 nm are fabricated by nanosphere lithography and pulsed laser deposition method. The result indicates that the frequency of acoustic vibrations of GZO nanoparticles decrease as the Ga-concentration is increased. Importantly, the vibration period of the GZO nanoparticles at the same Ga doping concentration show a nonlinear increase as the nanoparticle size is increased, which is different from the common linear dependency in undoped ZnO nanoparticles. It may be attributed to the crystal structure distortion and elastic characteristics variation due to Ga doping, and the elastic modulus at 7.3% Ga doping is decreased by 30%–60% for GZO nanoparticles with different sizes. The study can be very helpful for evaluating the crystal structure distortion and elastic characteristics of doped nano-materials with optical methods. Besides, it can offer a complementary method of thermal management in ZnO based optoelectronic devices.

Enhanced fluorescence efficiency and photocatalytic activity of ZnS quantum dots through Ga doping

Zinc Sulfide (ZnS) quantum dots (QDs) with enhanced fluorescence efficiency and photocatalytic activity have been attained through Ga doping for the first time. Ga-doped ZnS QDs were synthesized via a solvothermal method using Polyethylene glycol (PEG) as a stabilizer. Transmission electron microscopy studies disclosed that the obtained QDs were slightly polydispersed with an average size of 5.5–3.8 nm. The results of X-ray diffraction and Raman and X-ray photoelectron spectroscopy stipulated that the Ga ions were successfully incorporated into the ZnS crystal lattice without amending their internal structure. A blue shift was noticed in the ZnS QDs when doped with Ga. The photoluminescence spectra of all the QDs displayed the same blue emission and enhanced fluorescence efficiency with increase in Ga doping content. The photocatalytic degradation of the phenol red dye under UV-light illumination was enhanced with increasing Ga doping concentration. Thus, the Ga-doped ZnS QDs are potential and favorable candidates for both photoluminescent and photocatalytic device applications.

Ga Dopant Induced Band Gap Broadening and Conductivity Enhancement in Spray Pyrolysed Zn0.85Ca0.15O thin Films

Ga doped Zn0.85Ca0.15O thin films were prepared by spray pyrolysis method and studied the impact of Ga doping concentration on the physical properties of these films. XRD analysis confirmed the structural purity and polycrystalline nature of the films and composition analysis verified the incorporation of dopants in the structures. Optical transmission in the visible range initially increased and at higher Ga concentration decreased in accordance with the crystalline quality. Energy gap increased with doping percentage due to Burstein-Moss effect arising from the increase in carrier concentration. Ga doping resulted in enhanced electron concentration and consequently obtained lower resistive n type thin films. At higher doping level, electron density decreased due to the limit of solid solubility and hence conductivity slightly decreased but energy gap increased due to the extended localization arising from the poor crystallinity. Mobility decreased with doping due to the increased ionized impurity scattering at lower dopant concentration and due to intra-grain cluster scattering at heavy doping.

The study of transparent conducting gallium doped ZnO thin films in order to use in solar cells

In this study, transparent conducting Ga-doped ZnO thin films were deposited on glass substrate using chemical spray pyrolysis technique. The effect of Ga-doping concentration (0, 1, 2 and 3 at.%) on microstructural, optical and electrical characteristics of layers have been investigated. The studies of X-ray diffraction and optical transmission spectra show these films have a hexagonal wurtzite structure with (002) preferred growth direction, also a high transmission of 85-95% in visible range. Data analysis show that the band gap energies in these films are varying in the range of 3.27-3.33 eV, consistent with the Burstein-Moss shift effect, with Urbach tail widths between 114-160 meV. The 2 wt% Ga sample showed the maximum figure of merit (3×10-2Ω-1), with an electron concentration and sheet resistance of ~1.42×1019 cm-3 and 13 kΩ/square, respectively. Â

The spin-reorientation magnetic transitions in Ga-doped SmCrO3

Orthochromite SmCrO3 is known to show spin reorientation around 34 K and which was assigned as transition from Γ4 to Γ2. Our work reports the spin reorientation transitions in a series of Ga-doped SmCrO3: the spin reorientation transition from Γ4 to Γ2 at TSR2 = 88 K and another spin reorientation transition of Γ2 to Γ1 at TSR1 = 15 K were observed simultaneously when the content of Ga is 30%. Importantly, the evolution of spin reorientation transitions from the single spin reorientation of Γ4 → Γ2 to double ones of Γ4 → Γ2 → Γ1, and then to the single one of Γ2 → Γ1 is caused by the increase of Ga doping concentration. The M-T and M-H measurements have been made to study the temperature and magnetic field dependence of these spin reorientation transitions. These temperatures and doping dependence of spin reorientation transitions in RCrO3 (R = rare earth or yttrium) can appeal to the magnetic switching devices design based on these findings.

Ga-doped ZnO nanoparticles synthesized by sonochemical-assisted process

In this work, the experimental work has been conducted on the synthesis of Gallium (Ga)- doped zinc oxide (ZnO) nanoparticles with different doping concentration (0-5% at.) via sonochemical process. The precursors of Ga-doped ZnO nanoparticle were sourced by zinc acetate dehydrate and gallium (III) nitrate hydrate, respectively. Ammonia (NH3) was chosen as a precipitating agent in sonochemical process. The sonochemical time was operated for 10 min by a direct-immersion ultrasonic horn using Sonic model VCX 750 (750W, 20 KHz). Structural properties and morphologies were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that Ga doped ZnO powder after the synthesis were obtained in ultrafine structure that different form with pure ZnO. XRD analysis revealed that the pattern of Ga doped ZnO powder showed good crystallinity with the wurtzite structure due to the preferred orientation direction and crystallization. Ga doping concentration plays a key role in significant change of ZnO structures.

Wavelength-Tunable Ultraviolet Electroluminescence from Ga-Doped ZnO Microwires.

The usage of ZnO as active layers to fabricate hybrid heterojunction light-emitting diodes is expected to be an effective approach for ultraviolet light sources. Individual ZnO microwires with controlled gallium (Ga) incorporation (ZnO/Ga MWs) have been fabricated via a chemical vapor deposition method. It is found that with the increasing Ga-incorporated concentration, the near-band-edge (NBE) photoluminescence of the ZnO MWs blue-shifted gradually from 390 to 370 nm. Heterojunction diodes comprising single ZnO/Ga MWs and p-GaN have been fabricated. With increasing injection currents, the interfacial emissions can be suppressed effectively and the typical NBE emission dominates the electroluminescence (EL). In particular, with increasing Ga-doping concentration, the dominant EL emission wavelengths of the ZnO/Ga MW-based heterojunction diodes blue-shifted from 384 to 372 nm, and the blue shift can be ascribed to the Burstein-Moss effect induced by the Ga incorporation. The present work demonstrates the feasibility of optical band gap engineering of ZnO MWs and the potential application for wavelength-tuning ultraviolet light sources.

Electrical properties of lightly Ga-doped ZnO nanowires

We investigated the growth, crystal structure, elemental composition and electrical transport characteristics of ZnO nanowires, a promising candidate for optoelectronic applications in the UV-range. Nominally-undoped and Ga-doped ZnO nanowires were grown by metal-organic chemical vapor deposition. Photoluminescence measurements confirmed the incorporation of Ga via donor-bound exciton emission. With atom-probe tomography we estimated an upper limit of the Ga impurity concentration (). We studied the electrical transport characteristics of these nanowires with a W-nanoprobe technique inside a scanning electron microscope and with lithographically-defined contacts allowing back-gated measurements. An increase in apparent resistivity by two orders of magnitude with decreasing radius was measured with both techniques with a much larger distribution width for the nanoprobe method. A drop in the effective carrier concentration and mobility was found with decreasing radius which can be attributed to carrier depletion and enhanced scattering due to surface states. Little evidence of a change in resistivity was observed with Ga doping, which indicates that the concentration of native or background dopants is higher than the Ga doping concentration.