Effects of microstructure on transport properties of undoped hydrogenated amorphous silicon films

• Published in: Applied physics letters 1993-08, Vol.63 (7), p.955-957
• Main Authors: DAWSON, R. M. A, FORTMANN, C. M, GUNES, M, LI, Y. M, NAG, S. S, COLLINS, R. W, WRONSKI, C. R
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity of specific materials; Electronic transport in condensed matter; Exact sciences and technology; Physics
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.109856

Electronic transport properties have been investigated in undoped hydrogenated amorphous silicon (a-Si:H) materials whose microstructure and void fraction are changed by deposition temperature (Ts). The hydrogen content in these materials decreases from 15 to 5 at. % and the void fraction by 14% as Ts is raised from 200 to 350 °C. The photo and dark conductivities are measured from 40 to 190 °C and extended state electron mobilities are derived from a self-consistent analysis. The room temperature mobilities are found to increase from 0.8 to 30 cm2/V s and become less temperature dependent as Ts increases. These temperature activated mobilities explain the Meyer–Neldel rule [Z. Tech. Phys. 18, 588 (1937)] in a-Si:H materials whose dark conductivity activation energies are greater than 0.4 eV where it cannot be explained by the statistical shift of the Fermi level.