CONICET | Buscador de Institutos y Recursos Humanos

Modulated photoconductivity has proved to be an excellent tool to probe the density of states of semiconductors. However, though a great deal of attention has been devoted to the high frequency regime for its simplicity of application, the modulated photoconductivity in the low frequency (LF-MPC) regime has been the object of researches only recently. In the case of a dominant species of states present in the orbidden gap, it was shown that LF-MPC is a good complementary technique to the high frequency method to extract different transport parameters. In this paper, we present a complete theoretical analysis of the LF-MPC experiment for the case when different species of traps are present.We solve the complete system of equations that describe the experiment, and we apply simplifying assumptions to deduce a simple formula relating the photocurrent phase shift to the density of states DOS at the majority carriers quasi-Fermi level. By means of numerical calculations, we discuss the accuracy of our development, and of previous approximate formulas, to reconstruct a given DOS. Finally, we present experimental and theoretical evidence that, under sensitization conditions, the sign of the phase shift of the modulated photocurrent reverses and the steady-state photoconductivity depends superlinearly on the generation rate.LF-MPC) regime has been the object of researches only recently. In the case of a dominant species of states present in the orbidden gap, it was shown that LF-MPC is a good complementary technique to the high frequency method to extract different transport parameters. In this paper, we present a complete theoretical analysis of the LF-MPC experiment for the case when different species of traps are present.We solve the complete system of equations that describe the experiment, and we apply simplifying assumptions to deduce a simple formula relating the photocurrent phase shift to the density of states DOS at the majority carriers quasi-Fermi level. By means of numerical calculations, we discuss the accuracy of our development, and of previous approximate formulas, to reconstruct a given DOS. Finally, we present experimental and theoretical evidence that, under sensitization conditions, the sign of the phase shift of the modulated photocurrent reverses and the steady-state photoconductivity depends superlinearly on the generation rate.

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