Chemical bonding, optical constants, and electrical resistivity of sputter-deposited gallium oxide thin films

Abstract

Comparative study between erbium and erbium oxide-doped diamondlike carbon films deposited by pulsed laser deposition technique Influence of sputtering parameter on the optical and electrical properties of zinc-doped indium oxide thin films Gallium oxide (Ga 2 O 3 ) thin films were made by sputter deposition employing a Ga 2 O 3 ceramic target for sputtering. The depositions were made over a wide range of substrate temperatures (T s ), from 25 to 600 C. The effect of T s on the chemical bonding, surface morphological characteristics, optical constants, and electrical properties of the grown films was evaluated using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and four-point probe measurements. XPS analyses indicate the binding energies (BE) of the Ga 2p doublet, i.e., the Ga 2p 3/2 and Ga 2p 1/2 peaks, are located at 1118.0 and 1145.0 eV, respectively, characterizing gallium in its highest chemical oxidation state (Ga 3þ ) in the grown films. The core level XPS spectra of O 1s indicate that the peak is centered at a BE $ 531 eV, which is also characteristic of Ga-O bonds in the Ga 2 O 3 phase. The granular morphology of the nanocrystalline Ga 2 O 3 films was evident from AFM measurements, which also indicate that the surface roughness of the films increases from 0.5 nm to 3.0 nm with increasing T s . The SE analyses indicate that the index of refraction (n) of Ga 2 O 3 films increases with increasing T s due to improved structural quality and packing density of the films. The n(k) of all the Ga 2 O 3 films follows the Cauchy's dispersion relation. The room temperature electrical resistivity was high ($200 X-cm) for amorphous Ga 2 O 3 films grown at T s ¼ RT-300 C and decreased to $1 X-cm for nanocrystalline Ga 2 O 3 films grown at T s ! 500-600 C. A correlation between growth conditions, microstructure, optical constants, and electrical properties of Ga 2 O 3 films is derived. V C 2014 AIP Publishing LLC.

Mg-doped β-Ga2O3 films with tunable optical band gap prepared on MgO (110) substrates by metal-organic chemical vapor deposition

“…The Ga 2p 1/2 and Ga 2p 3/2 core levels shown in Fig. 3b before annealing are observed at binding energies (BE) of 1145.15 and 1118.25 eV, respectively, which are similar to the results of C.V. Ramana et al [10]. A shift of 0.45 eV to the higher BE direction after annealing is observed for these two peaks, which is due to the redistribution of electronic charge around the constituent atoms.…”

“…The actual Mg concentrations calculated from the XPS spectra for the 1%, 3%, 5% and 10% Mg-doped samples before annealing are 1.2%, 2.8%, 5.4% and 9.3%, respectively, which are all very close to their nominal values. Due to the absorbed carbonyl (oxygen bonded to carbon) or hydroxyl (oxygen bonded to hydrogen) groups on the film surface [10], we could not calculate the concentration of lattice oxygen accurately based on the O 1s core level. However, the peak area of O 1s (normalized to Ga 2p) after annealing is somewhat larger than that of the film before annealing, indicating a probable increase in the concentration of lattice oxygen due to the oxidation of the film in the atmosphere ambient.…”

“…There are many different methods used to synthesize β-Ga 2 O 3 films such as sputtering [9,10], thermal evaporation [11,12], pulsed laser deposition (PLD) [13,14], molecular beam epitaxy (MBE) [3,15] and metal-organic chemical vapor deposition (MOCVD) [16]. The doping of β-Ga 2 O 3 films with different dopants such as Si [17] and Cu [18] has also been reported.…”

High-sensitivity β-Ga_2O_3 solar-blind photodetector on high-temperature pretreated c-plane sapphire substrate

“…Generally, μ increases with grain size due to reduced grain boundaries and thus suppressed grain-boundary scattering, especially for nanocrystalline materials. Moreover, μ is also sensitive to lattice imperfections, for example, vacancies, dislocations, and distortions [22,23]. Therefore, μ values are larger due to better crystallinity and larger grains in the β-Ga 2 O 3 epitaxial films grown on annealed substrates; these results are well-supported by the AFM and XRD results.…”

“…This observation is in good agreement with the XRD results and further confirms the improved crystallinity of β-Ga 2 O 3 epitaxy film by adopting the annealed substrate. This effect is also reflected by the change in surface roughness [22], and the RMS value monotonically increases from 1.35 to 3.17 nm with increasing substrate-annealing temperatures, as shown in Fig. 3(f).…”