Spectra of charged defects in glassy Ge 0.285 Pb 0.15 S 0.565 thin layers
- PDF / 156,267 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 12 Downloads / 155 Views
PHOUS, VITREOUS, POROUS, ORGANIC, AND MICROCRYSTALLINE SEMICONDUCTORS; SEMICONDUCTOR COMPOSITES
Spectra of Charged Defects in Glassy Ge0.285Pb0.15S0.565 Thin Layers R. A. Castro^, V. A. Bordovsky, N. I. Anisimov, and G. I. Grabko Herzen Russian State Pedagogical University, St. Petersburg, 191186 Russia ^e-mail: [email protected] Submitted May 29, 2008; accepted for publication June 20, 2008
Abstract—The relaxation-time distribution function, its main parameters, and energy distribution of the density of states of charged defects have been calculated for the first time on the basis of the experimental isothermal relaxation curves for dark current in thin films of glassy Ge0.285Pb0.15S0.565 semiconductors. The results obtained confirm the existence of non-Debye dispersion in this system at infralow frequencies and can be used for further study of the electronic properties of disordered semiconductors. PACS numbers: 71.23.Cq, 71.55.Jv, 73.61.Jc DOI: 10.1134/S1063782609030191
Study of many classes of materials (polymers, liquid insulators, chalcogenide glassy semiconductors (CGSs), etc.) indicates the existence of relaxation spectra with significant deviations from classical Debye dispersion. These deviations are interpreted in terms of the concepts about diffuse dielectric spectrum, which can be due both to the presence of relaxators with somewhat different (but similar) relaxation times τi and to the interaction between different relaxators. Such relaxators are generally atoms, molecules, groups of atoms, structural defects, etc.; they can form a continuous set (spectrum) of relaxation times. Concerning glassy systems, it is well known that D+ and D– centers with negative correlation energy can play the role of such defects, which exchange electrons during charge transport and accumulation [1]. Analysis of the Ge0.285Pb0.15S0.565 system by thermoactivation spectroscopy at temperatures T from 260 to 280 K revealed the existence of defect states with activation energy of 0.43 eV and concentration of ~1016 cm–3 [2]. Further study of the spectrum of defect states in glassy and amorphous structures of germanium chalcogenide is promising for research and in view of increasing (especially recently) interest in them as materials for modern optoelectronics [3]. In this paper, we report the results of studying the spectrum of relaxators for the Ge0.285Pb0.15S0.565 ternary system and calculations of the energy distribution of the density of charged defects, which are responsible for long-term isothermal relaxation in this semiconductor. The isothermal relaxation of dark current was measured on Ge0.285Pb0.15S0.565 films with a thickness of ~1.0 µm, prepared by thermal evaporation in vacuum. The samples were sandwiched with aluminum elec-
trodes (contact area 14.0 mm2). Isothermal relaxation curves were recorded with a V7-30 electrometer (range of measured currents from 10–15 to 10–7 A for both polarities) and a stabilized voltage source (measurements in fields E from 10–2 to 10–4 V/cm). During measurements, the temperature
Data Loading...
