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PHOTOCURRENT RELAXATION IN AsxSe1-x THIN FILMS: COMPOSITIONAL DEPENDENCE

M. S. Iovu1, I. A. Vasiliev1,* , D. V. Harea1, E. P. Colomeico1

Affiliation

  1. Centre of Optoelectronics, 1 Academiei str., MD-2028, Chisinau, Moldova Republic

Abstract

Photocurrent relaxation technique has been used to study the deep states in amorphous arsenic selenium films AsxSe1-x with x=0.02, 0.05, 0.1, 0.28, 0.4, 0.45, 0.5 and 0.6 using monochromatic light pulse (l=0.63 mm, F=(1-3)1014 (photon) cm-2s-1, t~25 s) at room temperature. The iph x t vs. kTln(nt) diagrams are used to evaluate the density-of-state (DOS) distribution in analogy with time-of-flight (TOF) post-transit photocurrent analysis. For the composition of x=0.02 this distribution consist of a broad maximum located near 0.69 eV. As the concentration of arsenic increase the position of the maximum increase up to 0.84 eV at x=0.4 and it width also increase in this range of composition. On contrary, for x>0.4 the DOS function consist of the narrow peak extended in the mid-gap and it intensity abrupt falls for x=0.45 and 0.5. By comparison with the steady-state photocurrent spectra the relaxation of photocurrent for x<0.4 have been interpreted as due to deep acceptor-like centers associated with D+ and D- defects with negative U-. For x>0.4 such interpretations suggest the reductions in defect densities because stressed rigid phase..

Keywords

Photocurrent relaxation, amorphous arsenic-selenium films, defect centers.

Submitted at: May 20, 2005
Accepted at: Sept. 22, 2005

Citation

M. S. Iovu, I. A. Vasiliev, D. V. Harea, E. P. Colomeico, PHOTOCURRENT RELAXATION IN AsxSe1-x THIN FILMS: COMPOSITIONAL DEPENDENCE, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 5, pp. 2317-2322 (2005)