Dominant Carrier Transport Mechanism Research Articles

Tunnel oxide thickness-dependent dominant carrier transport in crystalline silicon solar cells

Silver consumption reduction is a current development in commercial tunnel passivated contact (TOPCon) crystalline silicon solar cell devices aimed at lowering the entire production cost of photovoltaic energy sources. It depends on the number of fingers and/or finger spacing (SP) on a cell area. In this paper, we analyze the possibility of minimizing silver use with respect to the dominant carrier transport mechanism. The carrier transporting mechanism, such as “pinhole” and/or “tunnel” models, is identified by examining temperature-dependent I–V characteristics of polysilicon passivating contact as a function of tunnel oxide (TO) thickness from 0.6 to 2.2 nm. Thermal oxidation was used to produce ultrathin TO films (0.6–2.2 nm) with temperature and gas ratio controlled. We find that the “pinholes” transport mechanism prevails when the TO thickness exceeds 1.6 nm, whereas the “tunnel” mode dominates when the TO thickness is less than 1.4 nm. The pinhole density is critical in pinhole mode for increasing SP. It is found that low pinhole densities and thick TO thickness (more than 1.6 nm) are two of the primary causes of narrow SP in TOPCon devices, which need a considerable quantity of silver. The experimental TOPCon devices as a function of TO thickness show a considerable trade-off between open circuit voltage (Voc) and fill factor (FF). While Voc rises, FF drops as TO thickness increases. The mechanism is described.

Hysteresis loops on voltage-current characteristics and optical responses of PEDOT:PSS/ZnO nanorods/ZnO:Ga heterostructure

Volage (V)-current (I) curves of the poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/ZnO nanorods (NRs)/ZnO:Ga (GZO) heterostructure exhibited a rectification behavior with hysteresis loops both in forward voltage (VF) and reverse voltage (VR) regions. The ultraviolet (UV) light irradiation of 360 nm led to the increase in the reverse current (IR), i.e. generation of photocurrent (PC), and the decrease in the hysteresis loop area in the VF region. In dark, the 1/V vs. ln (I/V2) plot revealed that the dominant carrier transport mechanisms in the low- and the high-VF regions are the direct tunneling and the Fowler-Nordheim (F-N) tunneling through the dipole layer formed at the interface between the PEDOT:PSS and ZnO NRs layers, respectively. On the contrary, the carrier transport in the middle-VF region in dark was dominated by the bulk-limited mechanisms, such as the space-charge-limited (SCL) conduction controlled by the single shallow traps, the trap-free SCL conduction, and the trap-filled-limit conduction controlled by the traps with Gaussian distribution. The UV light irradiation changed the carrier transport mechanism in the middle-VF region to the trap-free SCL conduction. The resistive switching related to the hysteresis loop was found to be caused by the trapping and detrapping of the injected carriers at the traps. In dark, the maximum forward current was increased by the repetition of the VF sweep of 0 V → 5 V → 0 V, but decreased by the repetition of the VR sweep of 0 V → -5V → 0 V, indicating the possibility of the resistive memory. At the low VRs, PC spectra showed a main peak at 350 nm, which is corresponding to slightly higher photon energy than the bandgap energy of ZnO. Moreover, the existence of the tail extending into the bandgap was also observed on the PC spectra. From the time response of PC, the depth of the trap state was estimated to be 0.64–0.77 eV.

Barrier properties and current conduction mechanism for metal contacts to lightly and highly doped p-type 4H-SiC

The barrier properties of Ti, Ni and Pt contact to lightly (9 × 1016 cm−3) and highly (9 × 1018 cm−3) doped p-type 4H-SiC were investigated. It is found that the barrier heights and ideality factors estimated from the thermionic emission model for the lightly doped samples are non-ideal and abnormally temperature dependent. The anomalies have been successfully explained in terms of both the pinch-off model and the Gaussian distribution of inhomogeneous barrier heights. In addition, the evaluated homogeneous barrier heights are reasonably close to the average barrier heights from capacitance–voltage measurements. For the highly doped samples, thermionic field emission (TFE) is found to be the dominant carrier transport mechanism. The barrier heights estimated from the TFE model are temperature independent. If the barrier inhomogeneities and tunneling effects are considered, the experimental results of the samples are in well agreement with the theoretical calculations.

Carrier transport mechanisms of reactively direct current magnetron sputtered tungsten oxide/n-type crystalline silicon heterojunction

For optimizing the performance of tungsten oxide (WOx)/c-Si heterojunction solar cells, it is important to understand the carrier transport process within the device. Recently, several studies examined transport mechanisms; but yet reported not apparently. In this study, the fundamental carrier transport mechanisms in WOx/c-Si heterojunction solar cells and their effects on the device characteristics are investigated. Our results indicate that the trap-assisted-tunneling (TAT) process is the dominant carrier transport mechanism in the forward-bias voltage regime, while the generation of current in the space-charge region is dominant in the reverse-bias voltage regime. Interestingly, it was found that the hole-selective contact with lower oxygen-to-tungsten ratios, which is related to that of high trap densities, can assist the TAT process and increase the fill factor of the device regardless of the film conductivity. This finding is inconsistent with those of previous experiments but is consistent with those of previous simulations. Finally, this confirmation can help with optimization of WOx/c-Si heterojunction solar-cell efficiencies.

Au-free recessed Ohmic contacts to AlGaN/GaN high electron mobility transistor: Study of etch chemistry and metal scheme

The authors study the effect of etch chemistry and metallization scheme on recessed Au-free Ohmic contacts to AlGaN/GaN heterostructures on silicon. The effect of variation in the recess etch chemistry on the uniformity of Ohmic contact resistance has been studied using two different etch chemistries (BCl3/O2 and BCl3/Cl2). Experiments to determine the optimum recess etch depth for obtaining a low value of contact resistance have been carried out, and it is shown that near-complete etching of the AlGaN barrier layer before metallization leads to the lowest value of contact resistance. Furthermore, two metal schemes, namely, Ti/Al and Ti/Al/Ti/W, are investigated, and it is found that the Ti/W cap layer on Ti/Al leads to low contact resistance with a smooth contact surface morphology. The effect of maintaining unequal mesa and contact pad widths on the extracted values of contact resistance and sheet resistance using the linear transfer length method (LTLM) has been studied. This is important as LTLM structures are used as monitors for process control during various steps of fabrication. It is shown that the extracted contact resistance and sheet resistance values are reliable when the mesa width is equal to the contact pad width. Finally, a possible mechanism for carrier transport in the Ohmic contacts formed using this process has been discussed, based on temperature dependent electrical characterization, and the field emission mechanism is found to be the dominant mechanism of carrier transport. A low Ohmic contact resistance of 0.56 Ω mm, which is one of the lowest reported values for identical metal schemes, and good contact surface morphology has been obtained with moderate post-metal annealing conditions of 600°C.

Material-to-device performance correlation for AlGaN-based solar-blind p–i–n photodiodes

We report on crystalline quality-to-device performance correlation for self-powered Al0.40Ga0.60N, p–i–n ultraviolet (UV) photodetectors on c-plane sapphire. The active p–i–n detector stack was grown over an AlN buffer. Careful optimization of the nucleation density on growth surface helped achieve a two-orders and one-order of magnitude reduction in the screw and edge dislocation density in the buffer layer, respectively. This resulted in a nine-orders of magnitude reduction in the reverse leakage current from 4.3 mA to 4.2 pA (at 10 V). Correspondingly, a thirteen-fold enhancement in the zero-bias external quantum efficiency (EQE) from 3.4% to 45.5%, when measured under 289 nm front-illumination was also observed. The detector epi-stack grown over the optimal AlN buffer layers led to the realization of high-performance p–i–n detectors with a dark current density below 4 nA cm−2 at 10 V and a zero-bias EQE of 74.7% under back-illumination. This is one of the highest zero-bias EQE reported for solar-blind detectors realized on template-free and mask-free III-nitrides grown using metal organic chemical vapor deposition on any substrate. The deep-UV-to-visible rejection ratio exceeded 106 while the deep-UV-to-near UV rejection exceeded 103. The thermal-noise limited detectivity was estimated to be 4 × 1014 cm Hz1/2 W−1. Hopping conduction along screw dislocation-mediated localized trap states was found to be the dominant carrier transport mechanism in the samples exhibiting high reverse leakage. For these samples, the responsivity (photocurrent) exhibited an exponential variation with reverse bias and a nonlinear variation with input optical power. This is explained using a hole-trapping associated gain mechanism and its impact on the transient characteristics of the detectors is investigated. A 6 × 1 linear array of the highest EQE detectors was realized and detector performance parameters were found to be comparable before and after wire bonding. This study is expected to enhance the understanding of III-nitrides-based vertical, self-powered detectors and benefit the development of high-performance, focal plane arrays using less complicated growth techniques.

Significantly Improved Electrical Properties of Crosslinked Polyethylene Modified by UV-Initiated Grafting MAH.

Direct current (DC) electrical performances of crosslinked polyethylene (XLPE) have been evidently improved by developing graft modification technique with ultraviolet (UV) photon-initiation. Maleic anhydride (MAH) molecules with characteristic cyclic anhydride were successfully grafted to polyethylene molecules under UV irradiation, which can be efficiently realized in industrial cable production. The complying laws of electrical current varying with electric field and the Weibull statistics of dielectric breakdown strength at altered temperature for cable operation were analyzed to study the underlying mechanism of improving electrical insulation performances. Compared with pure XLPE, the appreciably decreased electrical conductivity and enhanced breakdown strength were achieved in XLPE-graft-MAH. The critical electric fields of the electrical conduction altering from ohm conductance to trap-limited mechanism significantly decrease with the increased testing temperature, which, however, can be remarkably raised by grafting MAH. At elevated temperatures, the dominant carrier transport mechanism of pure XLPE alters from Poole–Frenkel effect to Schottky injection, while and XLPE-graft-MAH materials persist in the electrical conductance dominated by Poole–Frenkel effect. The polar group of grafted MAH renders deep traps for charge carriers in XLPE-graft-MAH, and accordingly elevate the charge injection barrier and reduce charge mobility, resulting in the suppression of DC electrical conductance and the remarkable amelioration of insulation strength. The well agreement of experimental results with the quantum mechanics calculations suggests a prospective strategy of UV initiation for polar-molecule-grafting modification in the development of high-voltage DC cable materials.

High-pressure triggered quantum tunneling tuning through classical percolation in a single nanowire of a binary composite

In the era of miniaturization, the one-dimensional nanostructures presented numerous possibilities to realize operational nanosensors and devices by tuning their electrical transport properties. Upon size reduction, the physical properties of materials become extremely challenging to characterize and understand due to the complex interplay among structures, surface properties, strain effects, distribution of grains, and their internal coupling mechanism. In this report, we demonstrate the fabrication of a single metal-carbon composite nanowire inside a diamond-anvil-cell and examine the in situ pressure-driven electrical transport properties. The nanowire manifests a rapid and reversible pressure dependence of the strong nonlinear electrical conductivity with significant zero-bias differential conduction revealing a quantum tunneling dominant carrier transport mechanism. We fully rationalize our observations on the basis of a metal-carbon framework in a highly compressed nanowire corroborating a quantum-tunneling boundary, in addition to a classical percolation boundary that exists beyond the percolation threshold. The structural phase progressions were monitored to evidence the pressure-induced shape reconstruction of the metallic grains and modification of their intergrain interactions for successful explanation of the electrical transport behavior. The pronounced sensitivity of electrical conductivity to an external pressure stimulus provides a rationale to design low-dimensional advanced pressure sensing devices.

Effect of Grain Boundaries on Charge Transport in Methylammonium Lead Iodide Perovskite Thin Films

Methylammonium lead iodide (MAPbI3) has attracted great interest as an organic–inorganic hybrid perovskite for photovoltaic applications. Vacancy-mediated ion migration is one of the dominant carrier transport mechanisms in MAPbI3. Our previous work clarified the nature of migrating species and their moderating effect on electronic transport. However, to develop strategies to mitigate ion migration and its impact thereof, it is important to know whether the migration is homogeneous or controlled by microstructural features, such as grain boundaries. In this work, we implement temperature-dependent pulsed voltage–current measurements of MAPbI3 thin films with different grain sizes under dark conditions and distinguish the electromigration of iodine vacancies and methylammonium vacancies. Upon increasing the grain size, the total accumulated charge decreases, whereas the activation energies increase. This is consistent with the high grain boundary density in small-grained films responsible for facilitating charge transport. These results suggest that one viable strategy to decrease ion migration would be to engineer the grain boundaries of MAPbI3.

C60 Concentration Influence on MEH-PPV:C60 Bulk Heterojunction-Based Schottky Devices

We have investigated the effect of C60 concentration on the performance of poly[2-methoxy-5-(2′-ethylhexoxy-p-phenylene vinylene] (MEH-PPV):C60 blend-based Schottky barrier-based devices. Incorporation of C60 in MEH-PPV leads to a red shift and the reduction of intensity in MEH-PPV absorption spectra. The appearance of a C60 characteristic band in the Raman spectra of the composites indicates the presence of C60 in the blends. A FESEM study reveals that the addition of C60 significantly modifies the surface morphology of the blend films. However, higher concentrations (> 5 wt.%) results in agglomeration of C60 particles. Dark I–V measurements allow us to extract various diode parameters including barrier height, ideality factor, and saturation current. Profound variations have been observed in the dominant charge carrier transport mechanism for different C60 concentrations. A photoresponse study demonstrates the enhancement in the photocurrent with the increase in the C60 concentration up to 5 wt.%. Beyond this concentration, agglomeration impedes exciton dissociation and charge transport, which results in a decrease in the photocurrent. Finally, an impedance spectroscopy analysis has been extensively carried out to estimate the internal device parameters, such as junction resistance, capacitance and carrier lifetime. The correlation between these parameters and I–V curves has been established.

Charge carrier transport and electroluminescence in atomic layer deposited poly-GaN/c-Si heterojunction diodes

In this work, we study the charge carrier transport and electroluminescence (EL) in thin-film polycrystalline (poly-) GaN/c-Si heterojunction diodes realized using a plasma enhanced atomic layer deposition process. The fabricated poly-GaN/p-Si diode with a native oxide at the interface showed a rectifying behavior (Ion/Ioff ratio ∼ 103 at ±3 V) with current-voltage characteristics reaching an ideality factor n of ∼5.17. The areal (Ja) and peripheral (Jp) components of the current density were extracted, and their temperature dependencies were studied. The space charge limited current (SCLC) in the presence of traps is identified as the dominant carrier transport mechanism for Ja in forward bias. An effective trap density of 4.6 × 1017/cm3 at a trap energy level of 0.13 eV below the GaN conduction band minimum was estimated by analyzing Ja. Other basic electrical properties of the material such as the free carrier concentration, effective density of states in the conduction band, electron mobility, and dielectric relaxation time were also determined from the current-voltage analysis in the SCLC regime. Further, infrared EL corresponding to the Si bandgap was observed from the fabricated diodes. The observed EL intensity from the GaN/p-Si heterojunction diode is ∼3 orders of magnitude higher as compared to the conventional Si only counterpart. The enhanced infrared light emission is attributed to the improved injector efficiency of the GaN/Si diode because of the wide bandgap of the poly-GaN layer and the resulting band discontinuity at the GaN/Si interface.

Analysis of Dark Count Mechanisms of 4H-SiC Ultraviolet Avalanche Photodiodes Working in Geiger Mode

In this paper, the dark count mechanisms of 4H-SiC ultraviolet avalanche photodiodes (APDs) working in Geiger mode are studied by temperature-dependent characterizations. At temperatures above 260 K, the activation energy derived from the dark count characteristics is much less than half of the bandgap of 4H-SiC. Trap-assisted tunneling is determined as the dominant carrier transport mechanism in this temperature regime, which is supported by the observed capacitance frequency dispersion and low-temperature persistent photoconductivity effect. As temperature further decreases, the temperature dependence of dark count rate (DCR) becomes weaker, suggesting that band-to-band tunneling starts to play a role in the dark count generation process, which turns into the major mechanism below 120 K. As a consequence, one way to suppress dark counts for SiC APDs is to inhibit tunneling process, which can be realized by increasing the intrinsic layer thickness. In addition, it is found that when the single photon detection efficiency is in the range of 0%–30%, the DCR of the SiC APD can be reduced by an order of magnitude as temperature decreases from room temperature to 77 K, which is the first report of low-temperature performance of SiC APDs.

Effect of temperature and ridge-width on the lasing characteristics of InAs/InP quantum-dash lasers: A thermal analysis view

We investigate the thermal characteristics of multi-stack chirped barrier thickness InAs/InGaAlAs/InP quantum-dash-in-a-well lasers of different ridge widths 2, 3, 4 and 15µm. The effect of varying this geometrical parameter on the extracted thermal resistance and characteristic temperature, and their stability with temperature are examined. The results show an inverse relation of ridge-width with junction temperature with 2µm device exhibiting the largest junction temperature buildup owing to an associated high thermal resistance of ∼45°C/W. Under the light of this thermal analysis, lasing behavior of different ridge-width quantum-dash (Qdash) lasers with injection currents and operating temperatures, is investigated. Thermionic carrier escape and phonon-assisted tunneling are found to be the dominant carrier transport mechanisms resulting in wide thermal spread of carriers across the available transition states of the chirped active region. An emission coverage of ∼75nm and 3dB bandwidth of ∼55nm is exhibited by the 2µm device, thus possibly exploiting the inhomogeneous optical transitions to the fullest. Furthermore, successful external modulation of a single Qdash Fabry-Perot laser mode via injection locking is demonstrated with eye diagrams at bit rates of 2–12Gbit/s incorporating various modulation schemes. These devices are being considered as potential light sources for future high-speed wavelength-division multiplexed optical communication systems.

Carrier transportation properties and series resistance of n-type β-FeSi2/p-type Si heterojunctions fabricated by RF magnetron sputtering

Heterojunctions composed of n-type β-FeSi2 thin films and p-type Si(111) substrates were formed by radio frequency magnetron sputtering at an Ar pressure of 2.66 × 10−1 Pa at a substrate temperature of 560 °C. The current density–voltage (J–V) curves of the heterojunctions measured in the dark and under illumination at room temperature showed a large leakage current under reverse bias conditions and a weak response to near-infrared (NIR) light irradiation. From the results of the analysis of dark forward J–V curves, the dominant carrier transport mechanisms at V ≤ 0.15 V and V > 0.15 V were considered a recombination process and a space-charge-limited current process, respectively. Both capacitance–voltage and conductance–voltage characteristics at room temperature were measured and analyzed as a function of applied frequency (f) ranging from 20 kHz to 2 MHz in order to estimate the series resistance (Rs) by the Nicollian–Brews method. Rs was estimated as 77.79 Ω at 20 kHz. It decreased to 14.16 Ω at 2 MHz, which is expected because the charges at the interface states cannot follow the AC signal at high f values.

Low temperature carrier transport mechanism in high-mobility zinc oxynitride thin-film transistors

The authors investigate the low-temperature carrier transport mechanism in high-mobility zinc oxynitride (ZnON) thin-film transistors (TFTs) over a wide range of operating temperatures below room temperature (90–293 K) by analyzing the temperature-dependent field-effect characteristics. In the subthreshold and transition regions, the variable range hopping and trap-limited band transport are considered as dominant carrier transport mechanisms in the ZnON TFT at temperatures below ∼207 K and above ∼243 K, respectively. In the above-threshold region, the field-effect mobility almost linearly depends on 1/T (T: absolute temperature) at all temperatures, which represents that the trap-limited band transport is the dominant carrier transport mechanism through the entire temperature range of 90 to 293 K in the fabricated ZnON TFT. Approximately 1 order of magnitude higher subgap density of states is extracted from the fabricated ZnON TFT compared with a conventional amorphous indium-gallium-zinc oxide TFT, which is primarily attributed to the large number of defective ZnXNY bonds inside the ZnON.

Localized tail state distribution and hopping transport in ultrathin zinc-tin-oxide thin film transistor

Carrier transport properties of solution processed ultra thin (4 nm) zinc-tin oxide (ZTO) thin film transistor are investigated based on its transfer characteristics measured at the temperature ranging from 310 K to 77 K. As temperature decreases, the transfer curves show a parellel shift toward more postive voltages. The conduction mechanism of ultra-thin ZTO film and its connection to the density of band tail states have been substantiated by two approaches, including fitting logarithm drain current (log ID) to T−1/3 at 310 K to 77 K according to the two-dimensional Mott variable range hopping theory and the extraction of density of localized tail states through the energy distribution of trapped carrier density. The linear dependency of log ID vs. T−1/3 indicates that the dominant carrier transport mechanism in ZTO is the variable range hopping. The extracted value of density of tail states at the conduction band minimum is 4.75 × 1020 cm−3 eV−1 through the energy distribution of trapped carrier density. The high density of localized tail states in the ultra thin ZTO film is the key factor leading to the room-temperature hopping transport of carriers among localized tail states.

Investigation of Carrier Transport Mechanism in High Mobility ZnON Thin-Film Transistors

In this letter, the carrier transport mechanism in a high-mobility zinc oxynitride (ZnON) thin-film transistor (TFT) is investigated by analyzing the gate bias and temperature dependence of conductance and intrinsic field-effect mobility ( $\mu _{\mathrm {FEi}})$ in the subthreshold and above-threshold regions, respectively. The measured drain currents increase with a temperature and show a thermally activated Arrhenius-like behavior in the subthreshold region. The experimental results are well explained using a Meyer–Neldel rule, which suggests that the trap-limited conduction is the dominant carrier transport mechanism in the ZnON TFT in the subthreshold region. The carrier transport mechanism in the ZnON TFT in the above-threshold region is investigated by examining the gate overdrive voltage ( $V_{\mathrm {OV}})$ and temperature dependence of $\mu _{\mathrm {FEi}}$ . $\mu _{\mathrm {FEi}}$ extracted from the ZnON TFT decreases with an increase in $V_{\mathrm {OV}}$ and temperature, which suggests that the phonon scattering is the most probable mechanism limiting $\mu _{\mathrm {FEi}}$ in the ZnON TFT in the above-threshold region.

Tuning the properties of ALD-ZnO-based rectifying structures by thin dielectric film insertion – Modeling and experimental studies

This paper is devoted to the electrophysical diagnostics of the ZnO-based rectifying structures in which the semiconducting oxide layer has been obtained by the low-temperature (80 °C ≤ T ≤ 130 °C) Atomic Layer Deposition (ALD) process. For the growth of examined diodes an organic compound (diethylzinc, DEZn) was used as a zinc precursor. As an oxygen source either deionized (in case of Schottky rectifiers as well as for n-type part of homojunction) or ammonia water (for the p-type layer of homojunction) was applied. In order to improve the basic electrical parameters of these structures (with a particular interest in the rectification (ION/IOFF) ratio) a solution based on inserting the thin dielectric layer (HfO2 or Al2O3) either below the Ag Schottky contact or between the homodiode parts, respectively, has been tested. Through comparing the electrical properties of Ag/HfO2/ZnO/ITO Schottky diodes and ZnO homojunctions as well as modeling their room-temperature current–voltage (I–V) characteristics according to the differential approach it has been proven that the optimal interlayer thickness allowing to achieve the ION/IOFF parameter as high as 104–105 for approximately ± 2 V polarization voltage range is about 2.5–5-nm. Additionally, involving the theoretical studies, the dominant carrier transport mechanisms were identified to be the monopolar injection, tunneling/trapping phenomena occurring in the dielectric layer and bimolecular recombination. The achieved results predestine the examined structures to be applied in the modern electronic devices, where stable in time and good quality diodes are required.

Unipolar resistive switching and tunneling oscillations in isolated Si–SiOx core–shell nanostructure

Unipolar resistive switching (URS) is observed in isolated Si–SiOx core–shell nanostructures. I–V characteristics recorded by a conductive atomic force microscope tip show SET and RESET processes with self compliance behavior. Hopping of carriers through defect states in the high resistance state (HRS) and space charge limited conduction in the low resistance state (LRS) are found to be the dominant carrier transport mechanisms in Si–SiOx core–shell nanostructures. URS between LRS and HRS may be attributed to the transition between hydrogen bridge (Si–H–Si) and hydrogen doublet (Si–HH–Si) defects. During RESET process, charge carriers tunnel through the nanostructure giving rise to oscillatory conduction.

Magnetic, transport, and magnetotransport properties of the textured Fe3O4 thin films reactively deposited onto SiO2/Si

The structural, magnetic, transport, and magnetotransport properties of Fe3O4 thin films with thicknesses from 38 nm to 95 nm are systematically investigated. The occurrence of the Verwey transition in these films at a temperature of about 120 K is established. It is found that the temperature dependences of the magnetic moment have a feature near 40 K, which can be attributed to the multiferroic phase. According to the X-ray diffraction data, the film structure represents a (001) texture. As was established using transmission electron microscopy, the height and width of texture crystallites increase with film thickness. Analysis of the temperature dependences of the resistivity showed that the dominant carrier transport mechanism in the films is thermoactivated tunneling. The thermoactivation energy, along with the room-temperature resistivity, decreases with increasing film thicknesses, which is most likely related to the variation in the crystallite size, especially in the crystallite width. The field dependence of magnetoresistance behaves similarly over the entire temperature range and has a positive MR peak in weak fields, which is related to spin-dependent tunneling through Fe3O4 grains and antiferromagnetically coupled antiphase boundaries.