Threading Dislocation Research Articles

Nucleation and Growth of GaAs on a Carbon Release Layer by Halide Vapor Phase Epitaxy.

We couple halide vapor phase epitaxy (HVPE) growth of III-V materials with liftoff from an ultrathin carbon release layer to address two significant cost components in III-V device - epitaxial growth and substrate reusability. We investigate nucleation and growth of GaAs layers by HVPE on a thin amorphous carbon layer that can be mechanically exfoliated, leaving the substrate available for reuse. We study nucleation as a function of carbon layer thickness and growth rate and find island-like nucleation. We then study various GaAs growth conditions, including V/III ratio, growth temperature, and growth rate in an effort to minimize film roughness. High growth rates and thicker films lead to drastically smoother surfaces with reduced threading dislocation density. Finally, we grow an initial photovoltaic device on a carbon release layer that has an efficiency of 7.2%. The findings of this work show that HVPE growth is compatible with a carbon release layer and presents a path toward lowering the cost of photovoltaics with high throughput growth and substrate reuse.

Imaging Threading Dislocations and Surface Steps in Nitride Thin Films Using Electron Backscatter Diffraction.

Extended defects, like threading dislocations, are detrimental to the performance of optoelectronic devices. In the scanning electron microscope, dislocations are traditionally imaged using diodes to monitor changes in backscattered electron intensity as the electron beam is scanned over the sample, with the sample positioned so the electron beam is at, or close to the Bragg angle for a crystal plane/planes. Here, we use a pixelated detector instead of single diodes, specifically an electron backscatter diffraction (EBSD) detector. We present postprocessing techniques to extract images of dislocations and surface steps, for a nitride thin film, from measurements of backscattered electron intensities and intensity distributions in unprocessed EBSD patterns. In virtual diode (VD) imaging, the backscattered electron intensity is monitored for a selected segment of the unprocessed EBSD patterns. In center of mass (COM) imaging, the position of the center of the backscattered electron intensity distribution is monitored. Additionally, both methods can be combined (VDCOM). Using both VD and VDCOM, images of only threading dislocations, or dislocations and surface steps can be produced, with VDCOM images exhibiting better signal-to-noise. The applicability of VDCOM imaging is demonstrated across a range of nitride semiconductor thin films, with varying surface step and dislocation densities.

The laser-induced rearrangement of extended defects in crystalline CdTe at a low temperature

The effect of subnanosecond laser pulses on the structure and electronic subsystem of extended defects in cubic semiconductors was studied using cadmium telluride (CdTe) as an example. A CdTe epitaxial film containing threading dislocations was exposed to pulsed laser emission at helium temperatures. This exposure led to a local rearrangement of dislocation, while the properties of the crystal lattice remained undisturbed. The rearrangement was visualized in situ via an observation of the single luminescent centers associated with the partial dislocation cores. The rearrangements in the center of the laser spot, as well as those far from this location, were detected, thus revealing the laser treatment’s non-thermal, relatively long-range influence. We associated the corresponding mechanism with Peierls’s gliding of dislocation under the impact of laser-induced hypersonic surface waves. The results we obtained are of interest in the development of all-optical methods for the local laser processing of extended defects in CdTe and subsequent expansion those methods to other A2B6 cubic semiconductors.

Charge-transfer interatomic potential to reproduce 30° partial dislocation movements for 4H-SiC in the surface vicinity and its application to BPD-TED conversion

4H-SiC has recently attracted attention as a new power semiconductor material to replace silicon. One of the challenges impeding its practical use is the elimination of killer defects in its epitaxial layer, such as dislocations and stacking faults. The conversion of basal plane dislocations (BPDs) into threading edge dislocations (TEDs) is crucial for reducing harmful mobile dislocations. However, the atomistic mechanism underlying the process remains elusive. To clarify the BPD–TED conversion mechanism, we developed a charge-transfer interatomic potential to reproduce 30° partial dislocation dynamics in the surface vicinity of 4H-SiC. The proposed potential significantly improved the accuracy of estimating the stacking fault energy and dislocation mobility in the regions where the dislocation core and surface overlap. Using the developed potential, we investigated the mechanism underlying the contraction of a pair of 30° partial dislocations in the vicinity of the surface. From the energy landscape, the equilibrium distance between the two partials decreased as the depth from the surface decreased because of the strong image force near the surface. The equilibrium distance decreased to zero when the depth reached 0.25 nm. This result is qualitatively consistent with the dislocation theory and the known effect of image force. From the viewpoint of the activation energies of kink nucleation and migrations, the activation energy for C-core and Si-core partial contractions decreased below a depth of 1 nm from the C-face and S-face surfaces, respectively, and became almost equal to that of C-core and Si-core expansions, respectively, when the depth reached 0.25 nm. Therefore, the partial BPDs can contract easily in the corresponding structures, particularly when the depth from the surface is less than 1 nm.

Analysis of diamond dislocations by Raman polarization measurement

Raman peaks with weak intensities at low wavelength were detected in dislocation areas of diamond substrates. Polarized Raman measurements were performed, and the origins of peaks were estimated. Based on the appearance of the Raman modes, the three peaks were estimated to be non-diamond owing to their structural asymmetries. Mapping measurements were carried out using one of the peaks and a small area of a high intensity region was estimated as the core of dislocation threading to the crystal surface. This method showed two dislocations on the surface, approximately 1.2 μm apart. The imaging using the peaks will be a powerful tool for investigating the dislocations of diamond epitaxial layers.

Three-dimensional distribution and propagation of dislocations in β-Ga2O3 revealed by Borrmann effect x-ray topography

Synchrotron radiation x-ray topography (XRT) in a transmission configuration based on the Borrmann effect (BE) was carried out to observe characteristic dislocation structures and three-dimensional distribution and propagation of dislocations in β-Ga2O3 grown via the edge-defined film-fed growth (EFG) method. Substrates with a range of surface orientations of (001), (010), and (2¯01), cut perpendicular or parallel to the ⟨010⟩ growth direction of the EFG, were observed to understand the whole picture of dislocations distributed in the bulk crystals. Using the (001)-oriented substrate, we found characteristic dislocation structures such as dislocation helices, damage-related (001)-plane dislocation networks, and tangled dislocation complexes, which exist universally in EFG crystals but have rarely been reported before. A careful measurement of the dislocation length in BE-XRT images taken with different g-vectors allows us to determine the crystal plane on which a dislocation lies. The BE-XRTs taken from the (010)-oriented and (2¯01)-oriented substrates suggested that the dislocations propagating along the [010] growth direction were dominant. Most of these b-axis threading dislocations had a Burgers vector of [010] or [001], and they tended to align in the (100) plane. The BE-XRT observations in this study provide valuable knowledge for understanding the structure and character of dislocations in β-Ga2O3.

The Si (001) substrate with sub-nano streaky surface: Preparation and its application to high-quality growth of GaAs heteroepitaxial-layer

The Si (001) substrates with a kind of special sub-nano streaky surface were prepared and applied to high-quality growth of GaAs heteroepitaxial-layers. The morphology of each of them features a series of parallel but randomly intermittent streaks along a common fixed direction and individually with their own saw-tooth cross-sections. The lateral interval between any two adjacent streaks is bound to be in sub-nano scale and both the two side-facets of every cross-section sawtooth are {111} planes. It has been found that the direct growth of GaAs epilayers on this kind of substrates, especially on exactly (001) oriented ones, can not only completely prevent the antiphase boundaries (APBs) generation, but also significantly reduce the threading dislocation density (TDD). This advancement could be regarded as a nearly perfect solution to APBs elimination and, moreover, provides better basis for further TDD reduction in the preparation of III-V/Si epilayers and for relevant device fabrications.

Porous pseudo-substrates for InGaN quantum well growth: Morphology, structure, and strain relaxation

Strain-related piezoelectric polarization is detrimental to the radiative recombination efficiency for InGaN-based long wavelength micro-LEDs. In this paper, partial strain relaxation of InGaN multiple quantum wells (MQWs) on the wafer scale has been demonstrated by adopting a partially relaxed InGaN superlattice (SL) as the pseudo-substrate. Such a pseudo-substrate was obtained through an electro-chemical etching method, in which a sub-surface InGaN/InGaN superlattice was etched via threading dislocations acting as etching channels. The degree of strain relaxation in MQWs was studied by x-ray reciprocal space mapping, which shows an increase of the in-plane lattice constant with the increase of etching voltage used in fabricating the pseudo-substrate. The reduced strain in the InGaN SL pseudo-substrate was demonstrated to be transferable to InGaN MQWs grown on top of it, and the engineering of the degree of strain relaxation via porosification was achieved. The highest relaxation degree of 44.7% was achieved in the sample with the porous InGaN SL template etched under the highest etching voltage. Morphological and structural properties of partially relaxed InGaN MQWs samples were investigated with the combination of atomic force and transmission electron microscopy. The increased porosity of the InGaN SL template and the newly formed small V-pits during QW growth are suggested as possible origins for the increased strain relaxation of InGaN MQWs.

Test concept for a direct correlation between dislocations and the intrinsic degradation of lateral PIN diodes in GaN-on-Si under reverse bias

Although often discussed, the role of threading dislocations (TDs) in the degradation of lateral GaN-on-Si p-GaN HEMTs under reverse bias stress test (RBST) has never been clearly shown in experiment until today. Here we present a novel test concept to establish a direct correlation between dislocations and degradation sites in RBST and demonstrate it on lateral p-GaN/AlGaN/GaN PIN diodes. By scaling down structures down to ~500 nm width, the point of degradation is always forced to be located at a defined position, independent of the local position of TDs. Furthermore, an integrated serial p-GaN resistor has been implemented with the PIN diode, which effectively limits the current and protects the device from a large meltdown due to parasitic capacitances and enables TEM analysis of structural degradation. A large quantity of lateral PIN devices exhibit a similar time-to-breakdown under RBST, indicating the intrinsic nature of this failure mode. Planar TEM analysis of a degraded and failed device clearly reveals structural damages and a breakdown of the AlGaN barrier as the failure signature. A combined planar and cross-sectional TEM lamella analysis approach of the expected failure site was introduced and applied. The results unambiguously show, that the observed degradation in the AlGaN barrier, which is attributed to the intrinsic failure mode, is not directly linked to the position of a dislocation.

Novel approach of combined planar and cross-sectional defect analysis of stressed normally-on HEMT devices with leaky Schottky gates

The clear correlation of defect localization by Electroluminescence to nanometer sized defects at Schottky gate contacts of GaN HEMTs are always challenging and limiting the root cause analysis of the stress related electrical degradation of the devices. In this paper a novel approach combining large area planar TEM defect screening followed by cross sectional preparation at identified defect sites is demonstrated to get access to relevant structural damages at the gate. The analysis flow is applied for normally-on GaN HEMT devices with an increased leakage at the Schottky gates observed after electrical stressing. To initiate electrical active degradation these devices were stressed up to significant changes in the electrical performance and then Electroluminescence spots were detected identifying possible defect positions. Metal intrusions into the AlGaN/ GaN stack underneath the Schottky gate contacts of only 20 nm size could be found by the newly combined planar/ cross-sectional analysis flow in good correlation to the EL spot positions. Analytical TEM investigations of the defects reveal Pt and Au inside the semiconductor reaching the 2DEG at a threading dislocation of the HEMT. These intrusions contribute to the gate leakage current and are causing the increased leakage current after electrical testing.

Reducing GaN crystal dislocations through lateral growth on uneven seed crystal surfaces using the Na-flux method

In recent years, we have achieved low threading dislocation density in GaN wafers by using the Na-flux multi-point seed technique. However, the resulting wafers exhibit regions of high dislocation density, exceeding 105 cm−2 at the coalescence boundary where pyramidal crystals merge. In this study, we discovered that annealing seed crystals at 900 °C generated an uneven surface with approximately 50 μm of GaN decomposition, and growing GaN on the thus-generated uneven surfaces induced lateral growth composed of facets. We then investigated the effect of the uneven surface on dislocation reduction and found that the average threading dislocation density of the grown crystal was reduced from cm−2 in the seed crystal to cm−2. We confirmed that the reduction in threading dislocation density was due to the termination of dislocations by means of inclusions, and to mergers or annihilation as they encountered one another during facet growth.

Development and analysis of thick GaN drift layers on 200 mm CTE-matched substrate for vertical device processing

This work reports the epitaxial growth of 8.5 µm-thick GaN layers on 200 mm engineered substrates with a polycrystalline AlN core (QST by QROMIS) for CMOS compatible processing of vertical GaN power devices. The epitaxial stack contains a 5 upmum thick drift layers with a Si doping density of 2 × 1016 cm−3 and total threading dislocation density of 4 × 108 cm−2. The thick drift layer requires fine-tuning of the epitaxial growth conditions to keep wafer bow under control and to avoid the formation of surface defects. Diode test structures processed with this epitaxial stack achieved hard breakdown voltages > 750 V, which is shown to be limited by impurity or metal diffusion from the contact metal stack into threading dislocations. Conductive Atomic Force Microscopy (cAFM) reveals some leakage contribution from mixed type dislocations, which have their core structure identified as the double 5/6 atom configuration by scanning transmission electron microscopy images. Modelling of the leakage conduction mechanism with one-dimensional hopping conduction shows good agreement with the experimental data, and the resulting fitting parameters are compared to similar findings on silicon substrates. The outcome of this work is important to understand the possibilities and limitations of vertical GaN devices fabricated on large diameter wafers.

Introduction of dislocation filtering with different ammonia flows in low-temperature grown AlN (< 1200 °C)

High crystalline quality of AlN layers are commonly grown at temperatures above 1200 °C. However, this work revealed that introducing a rough surface of AlN layer, defined as dislocation filtering (DF) herein, can improve the crystalline quality of 1.5 μm thick AlN layers grown at 1175 °C via metal organic vapor phase epitaxy technique. With 7 slm of ammonia flow during the DF growth, the lowest threading dislocation density (TDD) of ∼2.9 × 109 cm−2 was obtained. The result was associated to the formation of 3D growths which become reasonably smaller, denser, and more uniformly distributed with increasing ammonia flow up to 7 slm. The 3D growths were suggested to promote lateral growth that can increase the possibility for TD inclination and hence, mutual annihilation. The 3D growths characteristic disappeared when the ammonia flow was 10 slm. The optimized AlN layer that was obtained with 7 slm of ammonia flow exhibited an atomically smooth surface with a few deep trenches and improved transparency. Meanwhile, the calculated in-plane tensile strain for the AlN layers grown on DF with 1–7 slm of ammonia was about 3 times higher than the AlN layer without DF. However, no evidence of microcracks on the surface was observed.

Investigation of the Impact of Point Defects in InGaN/GaN Quantum Wells with High Dislocation Densities.

In this work, we report on the efficiency of single InGaN/GaN quantum wells (QWs) grown on thin (<1 µm) GaN buffer layers on silicon (111) substrates exhibiting very high threading dislocation (TD) densities. Despite this high defect density, we show that QW emission efficiency significantly increases upon the insertion of an In-containing underlayer, whose role is to prevent the introduction of point defects during the growth of InGaN QWs. Hence, we demonstrate that point defects play a key role in limiting InGaN QW efficiency, even in samples where their density (2-3 × 109 cm-2) is much lower than that of TD (2-3 × 1010 cm-2). Time-resolved photoluminescence and cathodoluminescence studies confirm the prevalence of point defects over TDs in QW efficiency. Interestingly, TD terminations lead to the formation of independent domains for carriers, thanks to V-pits and step bunching phenomena.

Origin of residual strain in heteroepitaxial films

Heterogeneous integration of diverse materials structures is critical to the scaling of electronic and photonic integrated circuits. For a model system of Ge-on-Si, we experimentally examine the roles of lattice misfit and thermal expansion misfit in determining the residual strain in as-grown and annealed heteroepitaxial films. We present data for Ge-on-Si growth from 400 to 730 °C followed by heat treatment from 500–900 °C. We show that strain fluctuations of 5.02% enable misfit dislocation formation, and we propose a comprehensive model for the conversion of compressive misfit strain to tensile elastic strain. The model is expressed in terms of three regimes: (1) misfit control for the low temperature growth regime at 400 °C; (2) point defect control via annealing in the point defect recovery regime at 500–650 °C; and (3) thermal expansion control for growth or anneal at T &amp;gt; 650 °C in the dislocation recovery regime. Growth from 400 to 730 °C exhibits near complete misfit strain relief by misfit dislocations leaving a consistent residual compressive strain of 0.09%. Growth at 400 °C followed by post growth heat treatment at 600 °C results in vertical threading dislocation density reduction via a point defect-mediated climb mechanism that gives minimal strain relief. Anneal above 650 °C promotes strain relief by dislocation glide. Temperature excursions at T &amp;gt; 730 °C followed by cooling to room temperature yield plastic strain in the Ge film that cannot be further relieved by thermal expansion misfit accommodation. Growth at 400–730 °C retains a residual compressive strain that represents the nucleation threshold for misfit dislocations.

(Invited) Application of Synchrotron X-Ray Topography Techniques to the Analysis of Defect Microstructures in Bulk GaN Substrates and Epilayers for Power Devices

Wide bandgap semiconductor gallium nitride (GaN), along with silicon carbide (SiC) are replacing silicon materials in the applications for power electronic devices. While SiC-based power technologies are based on bulk SiC substrates, GaN-based power technologies have until recently been based on GaN layers grown on foreign substrates such as sapphire, SiC and Si substrates. To achieve the full potential of GaN power devices, devices on bulk GaN substrates are desirable. In this review, the use of synchrotron X-ray topography techniques to evaluate defects and strain in bulk GaN substrates for vertical device development is presented. Ray tracing simulations is shown to effectively identify the Burgers vectors of all dislocations on X-ray topographs from GaN materials. Ammonothermal-grown GaN substrate wafers show the best quality among all the wafers. These wafers, which are free of basal plane dislocations (BPDs), have low curvature and threading mixed dislocations (TMDs) dominant among the TDs. However, certain ammonothermal substrates contain growth sectors with different impurity concentrations that are likely inherited from prior seed expansion growth runs. Patterned hydride vapor phase epitaxy (HVPE) GaN reveal a starkly heterogeneous distribution of dislocations with large areas containing low threading dislocation densities in between a grid of strain centers with higher threading dislocation densities and BPDs. These substrates also contain growth sector boundaries separating core regions growing in <11-22> directions and surrounding regions growing along [0001]. HVPE GaN substrates are characterized by high lattice distortion and dislocation densities of the order of 105-106 cm-2, which is much higher than 103-104 cm-2 of ammonothermal samples and dislocation-free areas in the patterned HVPE samples. Epitaxial growth and other processes involving heat treatment (including annealing) does not nucleate new defects but can result in interactions of dislocations (threading screw dislocations(TSDs)/threading mixed dislocations (TMDs)/threading edge dislocations (TEDs)) with point defects leading to changes in dislocation configurations. Mg-ion implantation for p-type doping does not change the distribution of dislocation but introduces lattice damage. By Rocking curve Analysis by Dynamical Simulation (RADS) analysis of X-ray rocking curves, the depth profile of strain can be obtained and correlated with doping profile. During annealing the implanted samples to heal lattice damage and activate the Mg ions, proper capping is necessary to limit loss of matter and introduction of additional lattice distortion. However, high pressure annealing has been shown to eliminate the need for capping. The effect on microstructure from other selectively area doping techniques such as etch and regrowth, diffusion and neutron transmutation will also be discussed.

Germanium wafers for strained quantum wells with low disorder

We grow strained Ge/SiGe heterostructures by reduced-pressure chemical vapor deposition on 100 mm Ge wafers. The use of Ge wafers as substrates for epitaxy enables high-quality Ge-rich SiGe strain-relaxed buffers with a threading dislocation density of (6±1)×105 cm−2, nearly an order of magnitude improvement compared to control strain-relaxed buffers on Si wafers. The associated reduction in short-range scattering allows for a drastic improvement of the disorder properties of the two-dimensional hole gas, measured in several Ge/SiGe heterostructure field-effect transistors. We measure an average low percolation density of (1.22±0.03)×1010 cm−2 and an average maximum mobility of (3.4±0.1)×106 cm2/Vs and quantum mobility of (8.4±0.5)×104 cm2/Vs when the hole density in the quantum well is saturated to (1.65±0.02)×1011 cm−2. We anticipate immediate application of these heterostructures for next-generation, higher-performance Ge spin-qubits, and their integration into larger quantum processors.

Biaxial, Hybrid Plastic-Elastic Relaxation in Micropatterned Semipolar InGaN Buffer Layers Improves Quality of Templated Quantum Well Emitters

Despite significant progress and multiple creative approaches taken toward the realization of long-wavelength III-nitride based light emitters over the past decade, high double-digit external quantum efficiencies remain elusive for GaN/InGaN based devices for wavelengths longer than 525 nm. This stems from the large mismatch between the GaN and InGaN lattice that manifests in deleterious crystal strain gradients, degrades surface growth morphology, and introduces diverse and potent nonradiative defects.A promising route to mitigation of strain-based effects is templating epitaxial growth on relaxed InGaN epilayers; in particular, a known and controllable platform for uniaxial strain relaxation is the creation of 1-D misfit dislocation arrays at semipolar GaN/InGaN heterointerfaces. Leveraging work by Hardy et al. on achieving >200 nm thick, partially relaxed semipolar InGaN layers [1] and precise determination of InGaN epilayer strain state and composition by Young et al. [2], we explore the potential for 2-D buffer layer relaxation in (11-22) InGaN layers via micron- and sub-micron patterning. Cathodoluminescence microscopy and x-ray diffraction indicated significant increases in biaxial epilayer relaxation with increased pillar aspect ratio; quantum wells deposited atop these relaxed InGaN buffers showed dramatic threading dislocation reduction, luminescence and morphology improvements, and evidence of improved indium incorporation relative to planar samples at nominally identical growth conditions.[1] Hardy, M.T., Young, E.C., Hsu, P.S., Haeger, D.A., Koslow, I.L., Nakamura, S., DenBaars, S.P., Speck, J.S. Suppression of m-plane and c-plane slip through Si and Mg doping in partially relaxed (20-21) InGaN/GaN heterostructures. Appl. Phys. Lett. 101, 132102 (2012).[2] Young, E. C., Romanov, A.E., Speck, J.S., Determination of composition and lattice relaxation in semipolar ternary (In,Al,Ga)N strained layers from symmetric x-ray diffraction measurements. Appl. Phys. Express. 4, 061001 (2011).

Wafer-scale heteroepitaxy GaN film free of high-density dislocation region with hexagonal 3D serpentine mask

GaN-based III-Nitride compound semiconductors are fundamental materials for high-performance optoelectronic and electronic devices. Low-defect-density substrate has been a major bottleneck in achieving high internal quantum efficiency and high breakdown voltage in those devices. However, a large-scale and uniform low dislocation density GaN film is still hard to obtain on foreign substrates, which is the mainstream economical method in scientific research and industrial production. Here, we present a 3D serpentine mask method of growing high-quality GaN film on foreign substrates without high dislocation density (HDD) areas by designing both sectional and planar shapes of stacked masks. The serpentine channel in the cross-section mechanically blocks the extended dislocations and the hexagonal planar pattern reduces the dimension of coalescence geometry. A wafer-scale GaN epilayer, free of HDD zone, with the overall threading dislocation density of 1.7 × 107 cm−2 estimated by plan-view cathode luminescence, is achieved in the metal-organic chemical vapor deposition system. Then, an array of light-emitting diodes based on this substrate with low forward voltages and high light output powers are fabricated, which introduces a practical method to provide high-quality GaN films for high-performance optoelectronic devices.

Description of electron mobilities in epitaxial lanthanum-doped barium stannate films: Influences of LO phonons, threading dislocation, and ionized donor defects

Lanthanum-doped barium stannate (La-doped BaSnO3 or LBSO) has attracted the attention of researchers and engineers because of its wide range of potential applications in electronic and optoelectronic devices. This is due to a combination of its exceptional room temperature (RT) mobility of 320 cm2 V−1 s−1 and high visible range transparency. However, epitaxial LBSO films made using strategic deposition techniques such as molecular beam epitaxy, pulsed laser deposition, and magnetron sputtering show comparatively low RT mobilities, between 24 and 183 cm2 V−1 s−1, and an accurate description of these RT mobilities is still sought. Herein, we provide the underlying scattering mechanisms related to longitudinal optical (LO) phonons, threading dislocation, and ionized donor defects to elucidate the RT mobilities in LBSO epitaxial films. It was found that the total mobility estimated using Matthiessen's rule provided strong quantitative agreement with experimental results. The large polaron mobility based on LO phonon scattering dominated the whole spectrum of electron concentrations in this system. It was an upper bound mobility, i.e., the mobility limit attained at 320 cm2 V−1 s−1. The calculated mobility associated with LO phonon and threading dislocation scatterings adequately verified the experimental results between 150 and 183 cm2 V−1 s−1. The predicted results for all three scattering types were predominant in experimental data at less than 150 cm2 V−1 s−1. These investigations deepen our understanding of mechanisms governing the charge transport scattering in epitaxial LBSO films and pave the way for the development of novel semiconductor thin films for use in electronic and optoelectronic devices.