Electron density and Hall mobility data were simultaneously analyzed in the frame of the relaxation time approximation in order to identify the main scattering mechanisms that limit the carrier mobility in β -Ga ₂ O ₃ single crystals. The Hall factor correction was self-consistently included in the fitting procedure. The analysis indicates that low-energy optical phonons provide the main scattering mechanism, via lattice deformation. In this regard, a deformation potential of about 4 × 10 ⁹ eV cm ⁻¹ was estimated. Furthermore, it is shown that the Hall coefficient and mobility can be measured by the usual experimental geometry, and the standard transport theory can be applied when off-diagonal elements of the resistivity tensor at zero magnetic field are negligible with respect to the diagonal ones. This directly follows from the analysis of the magneto-resistive tensor of a semiconductor with monoclinic structure. Such a requirement is satisfied under the hypothesis of nearly spherical energy surfaces, as has been reported to occur at the Γ minimum of the conduction band of β -Ga ₂ O ₃ .

Low resistivity n-type ε-Ga₂O₃ epilayers were obtained for the first time either by adding silane to the gas phase during the metal organic vapour phase epitaxy deposition or by diffusing Sn in nominally undoped layers after the growth. The highest doping concentrations were few 10¹⁸ cm⁻³ and about 10¹⁷ cm⁻³ for Si and Sn doping, with corresponding resistivity below 1 and 10 Ω cm, respectively. Temperature dependent transport investigation in the range of 10-600 K shows a resistivity behavior consistent with the Mott law, suggesting that conduction through localized states dominates the electrical properties of Si- and Sn-doped samples. For both types of dopants, two different mechanisms of conduction through impurity band states seem to be present, each of them determining the transport behavior at the lower and higher temperatures of the measurement range.

The temperature dependence of the Hall hole density and the Hall mobility data of heavy doped p-type 4H-SiC(Al) materials obtained by Al⁺ ion implantation have been analysed in the frame of the charge neutrality condition and the relaxation time approximation. Samples with implanted Al concentrations in the range 10¹⁹–10²⁰ cm⁻³ and 1950 °C/5 min conventional annealing have been taken into account. The reliability of the calculation has been critically discussed by focusing the attention on both the validity limits of the models for the impurity scattering mechanisms and the adopted Hall factor. By introducing empirical mass anisotropy factors, reasons were given in favour of a generalized use of the unique experimental evaluation of the Hall factor reported by the literature for p-type 4H-SiC, assessed for an Al acceptor density in the range of 1.8 × 10¹⁵ cm⁻³–2 × 10¹⁸ cm⁻³. The simultaneous fits of the Hall hole density and mobility data indicate an electrical activation of the Al impurities of the order or higher than 70% and a compensation of about 10% of the Al acceptors.

The fundamental absorption of GaSb, experimentally investigated by optical transmission measurements performed in the temperature range 9–300 K on nominally undoped molecular-beam-epitaxy-grown GaSb layers, is compared to theory. Calculations related to a band-to-band optical transition theory based on the models of Kane and Elliott, considering the band nonparabolicity and the electron-hole (exciton) interaction effects, respectively, show excellent agreement with experimental results. The role of different contributions to absorption coefficient is discussed. DOI: http://dx.doi.org/10.1103/PhysRevB.52.1463 © 1995 The American Physical Society

Unintentionally doped (001)‐oriented orthorhombic κ‐Ga₂O₃ epitaxial films on c‐plane sapphire substrates are characterized by the presence of ≈ 10 nm wide columnar rotational domains that can severely inhibit in‐plane electronic conduction. Comparing the in‐ and out‐of‐plane resistance on well‐defined sample geometries, it is experimentally proved that the in‐plane resistivity is at least ten times higher than the out‐of‐plane one. The introduction of silane during metal‐organic vapor phase epitaxial growth not only allows for n‐type Si extrinsic doping, but also results in the increase of more than one order of magnitude in the domain size (up to ≈ 300 nm) and mobility (highest µ ≈ 10 cm²V⁻¹s⁻¹, with corresponding lowest ρ ≈ 0.2 Ωcm). To qualitatively compare the mean domain dimension in κ‐Ga₂O₃ epitaxial films, non‐destructive experimental procedures are provided based on X‐ray diffraction and Raman spectroscopy. The results of this study pave the way to significantly improved in‐plane conduction in κ‐Ga₂O₃ and its possible breakthrough in new generation electronics. The set of cross‐linked experimental techniques and corresponding interpretation here proposed can apply to a wide range of material systems that suffer/benefit from domain‐related functional properties.