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Article

Structural and Electrically Conductive Properties of Plasma-Enhanced Chemical-Vapor-Deposited High-Resistivity Zn-Doped β-Ga2O3 Thin Films

by
Leonid A. Mochalov
1,2,
Sergey V. Telegin
2,
Aleksei V. Almaev
2,3,4,*,
Ekaterina A. Slapovskaya
2 and
Pavel A. Yunin
2,5
1
Department of Physics & Optical Science, The University of North Carolina at Charlotte, Charlotte, NC 28223, USA
2
Department of Inorganic Compounds Chemistry, N. I. Lobachevsky State University, 603950 Nizhny Novgorod, Russia
3
Laboratory of Metal Oxide Semiconductors, Research and Development Center for Advanced Technologies in Microelectronics, National Research Tomsk State University, 634050 Tomsk, Russia
4
Fokon LLC, 248035 Kaluga, Russia
5
Institute for Physics of Microstructures RAS, 603087 Nizhny Novgorod, Russia
*
Author to whom correspondence should be addressed.
Micromachines 2025, 16(8), 954; https://doi.org/10.3390/mi16080954
Submission received: 7 July 2025 / Revised: 15 August 2025 / Accepted: 17 August 2025 / Published: 19 August 2025
(This article belongs to the Special Issue Thin Film Microelectronic Devices and Circuits, 2nd Edition)
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Abstract

A method was developed for plasma-enhanced chemical vapor deposition of β-Ga2O3:Zn thin films with the possibility of pre-purifying precursors. The structural and electrically conductive properties of β-Ga2O3:Zn thin films were studied. Increasing the temperature of the Zn source (TZn) to 220 °C led to the formation of Ga2O3 films with a Zn concentration of 4 at.%, at TZn = 230 °C [Zn] = 6 at.% and at 235 °C. [Zn] = 8 at.% At TZn = 23 °C, the films corresponded to the β-Ga2O3 phase and were single-crystalline with a surface orientation of (–201). As TZn increased, the polycrystalline structure of β-Ga2O3 films with a predominant orientation of (111) was formed. The introduction of Zn led to the formation of a more developed microrelief of the surface. Raman spectroscopy showed that a small concentration of impurity atoms tended to replace gallium atoms in the oxide lattice, which was also confirmed by the Hall measurements. The concentration of charge carriers upon the introduction of Zn, which is a deep acceptor, decreased by 2–3 orders of magnitude, which mainly determined the decrease in the films’ resistivity. The resulting thin films were promising for the development of high-resistivity areas of β-Ga2O3-based devices.

1. Introduction

Recently, β-Ga2O3 has attracted increasing attention due to the newly discovered opportunities for its potential application as a basis for developing new semiconductor elements and various optoelectronic devices [1,2,3], power electronics devices [4,5,6,7], gas sensors [8,9], and transparent conductive oxides (TCOs) [10].
Like other metal oxide semiconductors, there is a need to obtain high-quality, high-purity thin layers of β-Ga2O3 with variable conductive properties over a wide range and with the ability to accurately specify their thickness, phase, and chemical composition. To deposit high-quality, thin layers of β-Ga2O3, it is advisable to consider methods such as atomic layer deposition (ALD) [11,12], pulsed laser deposition (PLD) [13,14], ion beam sputtering deposition (IBSD) [15], and various modifications of chemical vapor deposition (CVD) [16]. The first three methods have advantages but do not have a high deposition rate, and they also require expensive equipment and special precursors. Many epitaxial methods do not permit the deposition of continuous films with small thicknesses. Additionally, these methods do not permit the pre-purification of the precursors. The purity of the final deposited films depends on the impurity contents of the precursors. We previously developed a facility for depositing metal oxide semiconductor films via plasma-enhanced chemical vapor deposition (PECVD), which has the capability to pre-purify precursors [17,18,19]. The gaseous gallium was purified via distillation in complex oxygen–hydrogen plasma. The process of purification includes oxidation and reduction stages carried out at low pressure in an inductively coupled non-equilibrium plasma discharge, with the plasma treatment facilitating the intensive removal of the contained carbon and most of the metal impurities. The Ga precursors were at least 8N pure, and using high-purity precursors clearly affects the chemical composition of the final β-Ga2O3 films. Background impurities, even at levels of 0.01–0.1 ppm, significantly affect electrical and optical properties and, to a lesser extent, structural properties [20]. Additionally, PECVD offers high-precision control over the thickness, phase, and chemical composition of β-Ga2O3 films [17,18,19,21,22,23,24,25].
We have previously reported the possible deposition of both Ga2O3 [22,23,24] and ZnO [25] using the same PECVD method. Given the potential of this method, developing a technique to deposit and study the properties of these metal-oxide-doped films is appealing. Doping ZnO films with Ga facilitates a high concentration of donors in the semiconductor [26,27]. Additionally, when the concentration of Ga is 1 at.% or higher, two-phase composite films are formed that combine the properties of two metal oxides, and are commonly referred to as GZO films. GZO has attracted interest as a material for developing TCOs [26] and gas sensors [28,29], and it can be concluded that the material may be useful for creating highly conductive functional areas in Ga2O3-based power and optical electronics devices. On the other hand, functional Ga2O3-based power and optical electronics devices require high-resistivity areas that can act as drift and buffer layers, guard rings, sensitive layers, and low-dark-current photodetectors [30,31,32,33]. To create high-resistance areas, it is advisable to use Ga2O3 doped with Zn, and this material was initially investigated to obtain p-type Ga2O3 [34,35,36,37]. However, despite theoretical predictions [36,38], it was not possible to obtain p-type conductivity by doping Ga2O3 with Zn in practice. It was later shown that Zn acts as a deep acceptor [39], compensating for the small donor levels of defects formed during material growth, which leads to an increase in Ga2O3 resistivity. It is thus possible to create layers with high and low conductivity in the Ga–Zn–O system using PECVD with the same precursors and tooling. This work focuses on the deposition and investigation of the structural and electrically conductive properties of Ga2O3 films doped with Zn and deposited via PECVD with pre-purification of the precursors. This is the first time that Ga2O3:Zn films have been deposited via PECVD with pre-purification of Ga and Zn precursors, with the advantages of this technique presented above. PECVD and its various modifications have proven to be scalable, highly reproducible, and easy to automate and implement, leading to their widespread industrial use for deposition of thin semiconductor films for various applications [40].
Experimental studies have shown that Ga2O3:Zn films and bulk crystals are of interest for TCOs [34], phosphors [41], photocatalysts [42,43], and gas sensors [44]. In many studies, especially those involving the deposition of Ga2O3:Zn films, high concentrations of Zn (1–10 at.%) were used. To compare our results with those studies, we deposited and investigated Ga2O3:Zn thin films containing 4 at.%, 6 at.%, and 8 at.% of Zn.

2. Materials and Methods

The PECVD installation used in the experiment made it possible to purify the initial Ga and Zn and deposit them onto the substrate [17]. During the PECVD process, metal sources were heated to high temperatures at which the formation of appropriate vapors is possible. These vapors interacted with O2 and Ar plasma during deposition. The inductively coupled non-equilibrium plasma discharge was excited via an external inductor placed on the outer surface of the reactor, a generator with an operating frequency of 40.68 MHz and the maximum power of 500 W, and a matching unit. Commercially available high-purity Ga 6N and Zn 5N were preliminarily purified: Quartz boats with the initial molten Ga and Zn were placed in the high-temperature zone of a tubular reactor. The purifying reactor was evacuated to 1 × 10−5 Torr for a few hours to remove traces of O2 and H2O from the walls. Next, the Ga source was heated to TGa = 850 °C; then, the total flow of the Ar through the plasma–chemical reactor was set 30 mL/min at the total pressure in the system of 1 × 10−3 Torr and the plasma discharge was ignited. The adjacent purifying reactor contained a Zn source heated to temperatures of TZn = 220 °C, 230 °C, and 235 °C. The absolute error of the TGa and TZn was 1 °C. Purified Ga and Zn vapors in elemental form were transported by a carrier gas H2 stream through a heated quartz line to a cross-shaped mixing device, which was also equipped with an external heater made of high-purity quartz which served as a growth reactor. The reaction of interaction between the elements was initiated by electron impact/electron sticking mechanisms in the plasma discharge, with a mixture of O2 and Ar forming the plasma. Solid reaction products were deposited on a c-plane sapphire substrate. The plasma power corresponded to 30 W at film deposition. The temperature of the substrate Ts was maintained at 350 °C, a value previously found to be optimal for depositing high-quality Ga2O3 thin films via PECVD [24]. The area of the substrates was 10 mm × 10 mm, and the average film thickness was 300 nm; the deposition time of thin films was 60 min. The experimental PECVD installation and the principles of its operation were discussed in detail in our previous work [18].
To determine the phase composition of thin films, an X-ray diffraction (XRD) analysis was performed using a Bruker D8 Discover diffractometer (Bruker, Billerica, MA, USA) (CuKα λ = 1.5406 Å) in Bragg–Brentano geometry with a LynxEYE position-sensitive linear detector (Bruker, USA). The morphological state of the surface of gallium oxide films was studied using atomic force microscopy (AFM) using a scanning probe microscope SPM-9700 (Shimadzu, Kyoto, Japan) in contact mode and scanning electron microscopy (SEM) JSM IT-300LV SEM (JEOL, Tokyo, Japan) at an accelerating voltage of 20 kV. The SPM-9700 (Shimadzu, Kyoto, Japan) microscope has a horizontal resolution of 1–2 nm and a vertical resolution of 0.1–0.2 nm. Energy-dispersive X-ray (EDX) spectroscopy performed with an X-MaxN 20 energy-dispersive elemental analysis detector (Oxford Instruments, Oxfordshire, UK) was used to determine the elemental composition of thin films. The error in determining the concentration of elements via this method is 0.1 at.%. In addition, Raman spectra of the thin films were measured using an Alpha 300 AR confocal Raman spectroscopy system (WiTec, Ulm, Germany). A solid-state laser with an operating wavelength of 488 nm and an ×100 objective lens (NA = 0.75) was focused on the surface of the samples. An identical lens collected scattered light in the backscattering geometry. A spectral resolution of 1.2 cm−1 was achieved by using a diffraction grating with 1800 lines/mm.
Hall measurements at room temperature were performed to determine the conductivity type, concentration, and mobility of charge carrier of the samples. The four-probe method was used to perform the Hall measurements using the Nanometrics HL5500PC equipment (Nanometrics Inc., Ottawa, ON, Canada), which makes it possible to measure the parameters of high-resistive samples with a resistivity of up to 107 Ohm × cm. The permissible relative error limits when measuring direct current or voltage are ±2%, and ±2% when reproducing current or voltage. The permissible relative error limit for reproducing magnetic induction in the working area is ±2%. Before performing the Hall measurements, Ti/Au contacts were deposited on the thin film surfaces using an MSS-3G-2 magnetron sputtering system. Ti was deposited first.

3. Results and Discussion

On the XRD spectrum of the PECVD-deposited pure gallium oxide thin films (TZn = 23 °C), there are peaks at 2θ = 18.9°, 38.4°, and 59.2° (Figure 1), which can be associated with reflexes (–201), (–402), and (–603) of the β-Ga2O3 phase (PDF 00-043-10-12), respectively. The single-crystalline β-Ga2O3 film has the following lattice parameters: a = 12.20 Å, b = 3.04 Å, c = 5.79 Å, and β = 103.8°.
With an increase in TZn in addition to the peaks indicated above, multiple peaks appear that are related to reflexes of the β-Ga2O3 phase on the XRD spectra. In this case, the most intense peak corresponds to the (111) reflex of the β-Ga2O3 phase. The obtained lattice parameters a = 12.23 Å, b = 3.05 Å, c = 5.80 Å, and β = 103.8° are slightly higher in value compared to those of the sample deposited at TZn = 23 °C. Moreover, increasing the TZn results in an increase in the intensity of peaks on the XRD spectrum. Notably, the observed diffraction peaks shift slightly towards smaller 2θ as TZn increases. In addition, an increase in TZn leads to a significant increase in the crystallite sizes (Dc), which were estimated using the Scherrer equation (Table 1). Notably, a high-intensity peak corresponding to the (111) reflex and characteristic changes in lattice parameters were previously observed in β-Ga2O3 doped with Zn [33,34,42,45,46]. As shown below, an increase in TZn leads to an increase in the Zn concentration [Zn] in β-Ga2O3 films. Since the ionic radius of Zn2+ (0.74 Å) is slightly larger than that of Ga3+ (0.62 Å), introducing zinc into β-Ga2O3, where it substitutes for gallium, increases the lattice parameters of β-Ga2O3 and shifts the position of the diffraction peaks slightly. An increase in Dc indicates an increase in the crystallinity of the films with TZn.
EDX analysis of the PECVD-deposited pure and Zn-doped Ga2O3 thin films did not detect the presence of other chemical elements in the films, except Ga, O, and Zn. The concentrations of chemical elements for the studied series of thin films are shown in Table 2. The PECVD-deposited pure Ga2O3 thin films are characterized via high stoichiometry. An increase in TZn leads to an increase in [Zn]: for films deposited at TZn = 220 °C, [Zn] = 4 at.% is achieved by reducing [Ga] up to 36 at.%. With a further increase in TZn up to 230 °C and 235 °C, an increase in [Zn] is achieved by reducing both [Ga] and [O]. This may be explained by the segregation of the ZnO phase in thin films, characterized by a lower oxygen content. Despite the high concentrations of Zn detected via EDX, no other phases were detected in the films using XRD, which is typical of Zn-doped Ga2O3 films and crystals, and has been observed previously in Refs. [33,45,46,47]. Optical methods indirectly suggest the formation of ZnO precipitates [48], while the formation of the ZnGa2O4 spinel phase is possible at Zn concentrations of at least 10 at.% [42,43]. High-temperature annealing also facilitates the formation of the ZnO phase at low Zn concentrations [49].
The surface of the PECVD-deposited pure Ga2O3 thin films (Figure 2a) is heteromorphic and is represented by spherical grains with a size of Dg = 50 nm. An increase in TZn leads to a significant change in the microrelief of the PECVD-deposited Ga2O3 thin film surfaces. At TZn = 220 °C, large agglomerates up to 500 nm in size are formed, consisting of small grains with Dg = 50–100 nm. When the TZn increases to 230 °C, the size of agglomerates practically does not change; however, it is not possible to detect small grains. At TZn = 235 °C, the size of the agglomerates reaches 1.5 µm with Dg up to 300 nm. Notably, for all the studied films, Ts was fixed at 350 °C, and post-layer annealing was not performed. Even with an increase in TZn by 5 °C, the observed changes in the microrelief of the sample surface are due to an increase in the concentration of Zn in the PECVD-deposited Ga2O3 thin films (see Table 2 and Figure 2).
AFM images of the PECVD-deposited pure and Zn-doped Ga2O3 thin film surfaces are shown in Figure 3. The AFM and SEM images of the Ga2O3 thin films deposited at TZn = 220–235 °C are consistent. However, according to the AFM images, not only small spherical grains but also regular quadrangular crystallites with a size of up to 200 nm appear on the surface of the pure Ga2O3 thin films, which indicates the monocrystalline structure of the film. The surface roughness parameters of thin films determined using AFM are shown in Table 3, which introduces the following designations: Ra is the arithmetic average of profile height deviations, Rq is the root mean square average of profile height deviations, and Rz is the maximum peak-to-valley height of the profile. The PECVD-deposited pure Ga2O3 thin films (TZn = 23 °C) are relatively smooth with low roughness parameters. When Zn is introduced into Ga2O3 thin films (TZn = 220 °C), the roughness parameters increase significantly, which correlates with the SEM results (Figure 2). A further increase in TZn leads to a further increase in Ra, Rq, and Rz. A particularly significant increase in these parameters occurs with an increase in TZn from 230 °C to 235 °C. Similar changes in microrelief and roughness parameters were observed during the doping of β-Ga2O3 films with Zn [46,49]. Notably, these changes did not always exhibit the same characteristics as the Zn concentration increased.
Raman spectra of the PECVD-deposited pure and Zn-doped Ga2O3 thin films are shown in Figure 4. Active phonon modes are closely related to the symmetry of the crystal structure. In the monoclinic structure of the β-Ga2O3 crystal, there are two [GaO6] octahedra connected to two [GaO4] tetrahedra forming double chains along the b-axis. Each primitive β-Ga2O3 cell consists of 10 atoms generating 30 phonon modes, 27 of which are optical phonons. These optical modes at the center of the Brillouin zone can be expressed as follows [50]: Γopt = 10Ag + 5Bg + 4Au + 8Bu. Phonon modes with Ag and Bg symmetry are Raman-active, while those with Au and Bu symmetry are IR-active.
The presented Raman spectra of β-Ga2O3 thin films deposited at different TZn are largely similar. The Raman spectra of the samples can be divided into three regions according to the frequency range of the observed vibrational bands [51]. The high-frequency maxima (above 600 cm−1) at 631 cm−1, 654 cm−1, and 767 cm−1 correspond to the modes of valence and bending vibrations of GaO4 tetrahedra. The peaks at 322 cm−1, 348 cm−1, 417 cm−1, and 477 cm−1 in the middle frequency range (300–600 cm−1) correspond to the modes of bending vibrations of GaO6 octahedra. The main reason for the appearance of bands at 146 cm−1and 171 cm−1, as well as at 202 cm−1 in the low-frequency range (below 300 cm−1), is the vibrations and translations of GaO4–GaO6 chains. The intense peak in the 202 cm−1 region (Ag(3) mode) is due to the mode of vibrations of a typical Ga–O chain. Comparing the Raman spectra of β-Ga2O3 thin films deposited at different TZn, it was found that there were no noticeable peak shifts in the spectra. However, the Ag(3) mode in the spectrum of the films is slightly shifted towards lower Raman shift values as TZn increases. In particular, for TZn = 23 °C and 220 °C, the position of this peak is near 202 cm−1, and with further increase in TZn up to 230 °C and 235 °C, the peak shifts to 201 cm−1 and 200 cm−1, respectively. Notably, a similar change in the Raman spectra of β-Ga2O3 thin films was observed earlier [47,52] when Zn was introduced, which manifested as a shift in the position of Ag(3) to the region of low cm−1. This hardly noticeable shift is due to the ionic radius of Zn being close to that of Ga. During the formation of the crystal structure of Ga2O3 doped with Zn, a small part of gallium in the lattice nodes can be replaced by zinc. Zn ions introduced into the Ga2O3 lattice break the original Ga–O bond and transform the vibrational or translational modes of GaO4–GaO6 chains, so it is only when the Zn content increases to a certain extent that the shift becomes more noticeable.
According to the Hall measurements, the pure β-Ga2O3 thin films (TZn = 23 °C) have n-type conductivity, electron concentration n = 1.15 × 1015 cm−3, mobility µ = 0.11 cm2 × V−1 × s−1, and resistivity ρ = 4.8 × 104 Ohm × cm (Table 4). The relatively high n is due to the presence of donor-type defects [53] or background Sn impurity [17,23]. The relatively low µ is due to the low thickness of the films and the presence of grain boundaries, which enhances the scattering of charge carriers on the surface and leads to a decrease in µ in the thin films [54].
All thin films deposited at TZn = 220–235 °C have n-type conductivity. Thin films deposited at TZn = 220 °C are characterized by significantly lower n and, consequently, high ρ (Table 4). µ increases slightly for films at TZn = 220 °C, and notably, ρ increases mainly due to a decrease in n. A decrease in n and an increase in the ρ of β-Ga2O3 upon doping with Zn were observed earlier [35,39,55] and result from the Zn impurity being a deep acceptor compensating for the shallow donors. A slight increase in µ at TZn = 220 °C and 230 °C (with doping of Zn) is due to an increase in Dg and other changes in the microrelief of thin films (Figure 2 and Figure 3 and Table 3) [56]. The obtained result is consistent with the Seto model, which was developed for polycrystalline semiconductor films [57]. According to the Seto model, the scattering of charge carriers at grain boundaries is the main mechanism that determines µ. An increase in Dg is observed at TZn = 220 °C and 230 °C, which leads to an increase in µ. However, with a further increase in TZn to 235 °C, the microrelief of the films transforms, resulting in the formation of larger agglomerates measuring up to 1.5 µm. These agglomerates consist of smaller grains than those observed at TZn = 220 °C and 230 °C. In this case, it is likely that the smaller grains significantly affect the scattering of charge carriers, leading to a decrease in µ.
The results of Raman spectroscopy confirm that the Zn atom replaces the position of the Ga atom. In Refs. [38,58,59,60,61], density functional theory calculations showed that when β-Ga2O3 is doped with Zn, the substitution of Ga atoms with Zn atoms is an energetically favorable process. Moreover, our results confirm that the changes in the crystal lattice parameters are insignificant. The formation energies of Zn-substituted β-Ga2O3 vary widely, from 0.9 eV to 5.6 eV, depending on the model and conditions assumed in the calculations. As noted above, the substitution of a Ga atom for a Zn atom creates a deep enough acceptor level (Ev + (0.7–1.3) eV) that makes it difficult to obtain p-type gallium oxide conductivity. The increase in n with Zn content (at TZn = 220 °C and 230 °C) can be explained by the possible precipitation of a foreign ZnO phase in the bulk of β-Ga2O3 films. The content of the ZnO phase is too small to be detected via XRD; however, this semiconductor has a significantly smaller band gap of 3.3 eV [62], which can lead to an increase in the effective concentration of charge carriers. In addition, it is possible to assume the formation of a foreign phase of ZnO doped with Ga during the synthesis and deposition of films. Mutual doping of oxide mixtures was previously established for ITO [63]. On the other hand, Refs. [33,43,64] showed that an increase in Zn leads to an increase in oxygen vacancy concentration, which can exhibit donor-like properties.
The electrically conductive parameters of Zn-doped β-Ga2O3 thin films have previously been reported by Wang et al. in Ref. [64], where studies of PLD-deposited films at a thickness of 300 nm were carried out. At [Zn] = 3 at.%, 5 at.%, and 7 at.%, ρ = 6.97 × 106 Ohm × cm, 2.53 × 106 Ohm × cm, and 2.27 × 106 Ohm × cm, respectively. In addition, the n and µ values achieved for PECVD- and PLD-deposited Zn-doped β-Ga2O3 thin films are of a similar order of magnitude. Similar trends are observed in the changes in n and µ; µ values for PLD-deposited films are higher, probably due to the less developed microrelief of the film surface. Notably, the resistivity of β-Ga2O3 bulk crystals with a Zn concentration of 0.25 at.% was 1011–1014 Ohm × cm [35].
To develop PECVD technology for β-Ga2O3 and other ultra-wide bandgap semiconductors, with the possibility of pre-purifying precursors, we plan to conduct detailed studies of their properties to create functional areas for power and sensor electronics devices in the future. The studies will involve analyzing the chemical and elemental composition of films using X-ray photoelectron and secondary ion mass spectroscopy techniques, similarly to the approaches utilized in [65,66].

4. Conclusions

A method was developed for plasma-enhanced chemical vapor deposition of β-Ga2O3:Zn thin films with the possibility of pre-purifying metal precursors. Increasing the temperature of the Zn source (TZn) to 220 °C led to the formation of Ga2O3 thin films with an impurity concentration of 4 at.%, at TZn = 230 °C [Zn] = 6 at.% and at 235 °C [Zn] = 8 at.%. The phase composition of the films, regardless of TZn, corresponded to the monoclinic β-Ga2O3 phase. At TZn = 23 °C, the β-Ga2O3 films were single-crystalline with a surface orientation of (–201). As TZn increased, a polycrystalline structure of β-Ga2O3 films with a predominant orientation of (111) was formed. Doping films with Zn led to a slight increase in the lattice parameters of the crystal and a significant increase in the size of the crystallites. The introduction of Zn also led to the formation of a more developed microrelief of the film surface, an increase in roughness parameters by about two orders of magnitude and in grain size by up to 300 nm, and the formation of grain agglomerates with a size of up to 1.5 µm. Raman spectroscopy showed that a small concentration of impurity atoms tended to replace gallium atoms in the oxide lattice, which was also confirmed by the results of the Hall measurements. The concentration of charge carriers upon the introduction of Zn, which is a deep acceptor, decreased by 2–3 orders of magnitude, which mainly determined the decrease in film resistivity. The mobility of charge carriers was determined to a greater extent by the microstructure of the films and weakly depended on [Zn].

Author Contributions

Conceptualization, L.A.M., S.V.T., and E.A.S.; methodology, L.A.M., S.V.T., and P.A.Y.; software, E.A.S.; validation, S.V.T. and A.V.A.; formal analysis, L.A.M., E.A.S., and P.A.Y.; investigation, L.A.M., E.A.S., and P.A.Y.; resources, L.A.M. and A.V.A.; data curation, L.A.M., E.A.S., and P.A.Y.; writing—original draft preparation, L.A.M., A.V.A., and P.A.Y.; writing—review and editing, L.A.M., A.V.A., and P.A.Y.; visualization, E.A.S. and P.A.Y.; supervision, L.A.M.; project administration, L.A.M. and E.A.S.; funding acquisition, L.A.M. and A.V.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by The Russian Science Foundation, grant number 22-13-00053. The structural properties of the samples were studied using the infrastructure of Studying design-center for electronics of the Lobachevsky University, established as part of the federal project “Studying of specialists and creating scientific foundation for the electronic industry.”

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

Author Aleksei V. Almaev was employed by the company Fokon LLC. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.

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Figure 1. XRD patterns of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
Figure 1. XRD patterns of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
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Figure 2. SEM images of the PECVD-deposited pure (a) and Zn-doped Ga2O3 thin film surfaces at TZn = 220 °C (b), 230 °C (c), and 235 °C (d).
Figure 2. SEM images of the PECVD-deposited pure (a) and Zn-doped Ga2O3 thin film surfaces at TZn = 220 °C (b), 230 °C (c), and 235 °C (d).
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Figure 3. AFM images of the PECVD-deposited pure (a) and Zn-doped Ga2O3 thin film surfaces at TZn = 220 °C (b), 230 °C (c), and 235 °C (d).
Figure 3. AFM images of the PECVD-deposited pure (a) and Zn-doped Ga2O3 thin film surfaces at TZn = 220 °C (b), 230 °C (c), and 235 °C (d).
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Figure 4. Raman spectra of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
Figure 4. Raman spectra of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
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Table 1. The crystallite sizes of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
Table 1. The crystallite sizes of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
TZn (°C)Dc (nm)
2330.6
22032.9
23034.2
23536.6
Table 2. Elemental composition of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
Table 2. Elemental composition of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
TZn (°C)Elemental Concentrations (at.%)
GaOZn
2340600
22036604
23035596
23534588
Table 3. Roughness parameters of the PECVD-deposited pure and Zn-doped Ga2O3 thin film surfaces.
Table 3. Roughness parameters of the PECVD-deposited pure and Zn-doped Ga2O3 thin film surfaces.
TZn (°C)Ra (nm)Rq (nm)Rz (nm)
230.881.126.47
22015.1718.9355.04
23023.8230.51101.67
23588.84106.23249.55
Table 4. Electrically conductive parameters of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
Table 4. Electrically conductive parameters of the PECVD-deposited pure and Zn-doped Ga2O3 thin films.
TZn (°C)ρ (Ohm × cm)n (cm−3)µ (cm2 × V−1 × s−1)
234.8 × 1041 × 10150.11
2208.3 × 1065 × 10120.13
2303.4 × 1068 × 10120.22
2352.9 × 1061 × 10130.16
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Mochalov, L.A.; Telegin, S.V.; Almaev, A.V.; Slapovskaya, E.A.; Yunin, P.A. Structural and Electrically Conductive Properties of Plasma-Enhanced Chemical-Vapor-Deposited High-Resistivity Zn-Doped β-Ga2O3 Thin Films. Micromachines 2025, 16, 954. https://doi.org/10.3390/mi16080954

AMA Style

Mochalov LA, Telegin SV, Almaev AV, Slapovskaya EA, Yunin PA. Structural and Electrically Conductive Properties of Plasma-Enhanced Chemical-Vapor-Deposited High-Resistivity Zn-Doped β-Ga2O3 Thin Films. Micromachines. 2025; 16(8):954. https://doi.org/10.3390/mi16080954

Chicago/Turabian Style

Mochalov, Leonid A., Sergey V. Telegin, Aleksei V. Almaev, Ekaterina A. Slapovskaya, and Pavel A. Yunin. 2025. "Structural and Electrically Conductive Properties of Plasma-Enhanced Chemical-Vapor-Deposited High-Resistivity Zn-Doped β-Ga2O3 Thin Films" Micromachines 16, no. 8: 954. https://doi.org/10.3390/mi16080954

APA Style

Mochalov, L. A., Telegin, S. V., Almaev, A. V., Slapovskaya, E. A., & Yunin, P. A. (2025). Structural and Electrically Conductive Properties of Plasma-Enhanced Chemical-Vapor-Deposited High-Resistivity Zn-Doped β-Ga2O3 Thin Films. Micromachines, 16(8), 954. https://doi.org/10.3390/mi16080954

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