Artículos de revistas
Light-induced Metastability In A-ge : H
Registro en:
Journal Of Non-crystalline Solids. , v. 128, n. 3, p. 243 - 254, 1991.
223093
10.1016/0022-3093(91)90462-F
2-s2.0-0026155380
Autor
Santos P.V.
de O. Graeff C.F.
Chambouleyron I.
Institución
Resumen
Light-induced metastable changes in the conductivity of hydrogenated amorphous germanium (a-Ge : H) thin films deposited by rf-sputtering are reported. The films are photoconductive with room temperature photo-to-dark conductivity ratio σph/σd = 1.0-1.5 under AM1 illumination (1.0 mW/cm2). The dark conductivity and the photoconductivity of the films decrease after exposure to AM1 irradiation, which is attributed to light-induced defect formation. The changes are metastable and the conductivity returns to its original value after some hours in the dark. In order to establish the kinetics of defect formation and annealing, a differential set-up was used to measure conductivity transients under different temperatures and illumination conditions. The time evolution of the defect generation and annealing processes follows a stretched exponential behavior similar to the one observed for a-Si : H. Both processes are temperature activated, with activation energies of 0.40 and 0.45 eV, respectively. This behavior indicates that the kinetics of defect formation involve excitation over a wide distribution of barrier heights separating the annealed and the metastable states. The connection between defects kinetics and dispersive hydrogen diffusion is analyzed. © 1991. 128 3 243 254 Marques, Chambouleyron, (1989) Proc. 9th E.C. Photovoltaic Solar Energy Conf., p. 1042. , W. Paltz, G.T. Wrixon, P. Helm, Kluwer Academic, Dordrecht Karg, Bohm, Pierz, Influence of plasma deposition on structural and electronic properties of a-Ge:H (1989) Journal of Non-Crystalline Solids, 114, p. 477 Martin, Schroeder, Leidner, Oechsner, (1989) J. Non-Cryst. Solids, 114, p. 537 Turner, Jones, Pang, Bateman, Chen, Li, Marques, Paul, (1990) J. Appl. Phys., 67, p. 7430 Jackson, Kakalios, (1988) Amorphous Silicon and Related Materials, p. 247. , H. Fritzsche, World Scientific, Singapore, and references therein Stabler, Wronski, Reversible conductivity changes in discharge-produced amorphous Si (1977) Applied Physics Letters, 31, p. 292 Dersch, Stuke, Beichler, Light-induced dangling bonds in hydrogenated amorphous silicon (1981) Applied Physics Letters, 36, p. 456 Stabler, Wronski, Optically induced conductivity changes in discharge-produced hydrogenated amorphous silicon (1980) Journal of Applied Physics, 51, p. 3262 Hong, Hwang, (1986) Appl. Phys. Lett., 49, p. 645 Kocka, Vanecekk, Triska, (1988) Amorphous Silicon and Related Materials, p. 297. , H. Fritzsche, World Scientific, Singapore Kakalios, Street, Jackson, (1987) Phys. Rev. Lett., 59, p. 1037 Jackson, Kakalios, Evidence for hydrogen motion in annealing of light-induced metastable defects in hydrogenated amorphous silicon (1988) Physical Review B, 32 B, p. 1020 Stutzmann, Jackson, Tsai, (1985) Phys. Rev., 32 B, p. 23 Bube, Redfield, (1989) J. Appl. Phys., 66, p. 820 Redfield, (1988) Appl. Phys. Lett., 52, p. 492 Jackson, (1990) Phys. Rev., 41 B, p. 1059 Jackson, Marshall, Moyer, (1989) Phys. Rev., 39 B, p. 1164 Redfield, Bube, (1989) Appl. Phys. Lett., 54, p. 1037 Jackson, (1989) Philos. Mag. Lett., 59, p. 103 Stutzmann, (1987) Philos. Mag., 56 B, p. 63 As an example, the exact integration of eq. (7) for ϵ = 0.5 and ϵ = 1 leads to the following expressions for the factor K=[nBT(t)−nBT(∞)/nBT(0)−nBT(∞)[2,for ϵ=0.5 and K= nBT(t)/nBT(0), ϵ = 1. If during light soaking and annealing the changes in nBT(t) are small (ΔnBT/nBT < ∼ surface layer of the sample) K does not deviate appreciably from unity for measurement times t < τ. It can, therefore, be neglected in our analysis, and a simple stretched exponential behavior is recovered. The errors involved in the estimation of the time constants τ using this approximation are of ∼13% for ϵ = 0.5 and of ∼30% for ϵ = 1. See also ref. [16]Beyer, Herion, Wagner, Zastrow, (1990) Proc. Material Research Society Spring Meeting, , to appear in, San Francisco, CA Kakalios, Jackson, (1989) Amorphous Silicon and Related Materials, p. 165. , H. Fritzsche, World Scientific, Singapore