Thickness dependence of electrical properties of polycrystalline GaSbAs thin films grown on glass substrates: Analysis on the basis of a two-band conduction model using a differential Hall-effect method

• Published in: Thin solid films 2013-10, Vol.545, p.161-170
• Main Authors: Kajikawa, Y., Okamura, K., Okuzako, T., Matsui, Y.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Exact sciences and technology; Fittings; Glass; Grain-boundary barrier; Hall-effect measurement; Impurity-band conduction; Materials science; Mathematical models; Mean free path; Methods of deposition of films and coatings; film growth and epitaxy; Molecular, atomic, ion, and chemical beam epitaxy; Physics; Polycrystalline GaSbAs; Potential barriers; Structure and morphology; thickness; Surface and interface electron states; Surface states, band structure, electron density of states; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Temperature dependence; Thin film structure and morphology; Thin films
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.07.065

Polycrystalline films of undoped p-type GaSb0.8As0.2 with different thicknesses ranging from 0.1 to 1μm were grown on glass substrates at a substrate temperature of 300°C by molecular-beam deposition. Hall-effect measurements in the temperature range of 10–400K revealed the coexisting valence-band and impurity-band conduction. A differential Hall-effect method was applied for the purpose of obtaining concentration and mobility of holes in the surface-side region of the film eliminating the effects of the underlying substrate-side region. Furthermore, a two-band conduction model was applied for the purpose of obtaining concentration and mobility of holes in the valence band eliminating the effects of the impurity-band conduction. The concentrations of a shallow acceptor level, a deep acceptor level, and a compensating donor level are deduced through fitting the experimental temperature dependence of valence-band hole concentration by the solution of the charge-balance equation. The mean value and the standard deviation of the grain-boundary barrier height as well as the mean free path are deduced through fitting the experimental temperature dependence of mobility by assuming the thermionic emission of holes over grain-boundary potential barriers with fluctuated heights. The estimated results of the above parameters are presented as a function of the distance from the substrate interface. Especially, it is shown that the mean free path of valence-band holes is almost unchanged while the height of grain-boundary potential barriers decreases with the distance from the substrate. The obtained results suggest the necessity of improving the electrical properties of GaSbAs layers near at the beginning of their deposition by some method, e.g., by inserting buffer layers, in the practical application for thin film transistors. •Polycrystalline GaSbAs films of various thicknesses were deposited at 300°C.•A differential method was applied for Hall-effect measurements at 10–400K.•Impurity-band conduction and grain-boundary scattering were assumed for analysis.•Mean free path was estimated as a function of the distance from the substrate.•Barrier height at grain boundaries was shown to decrease as growth proceeds.