THE TRANSPORT MECHANISM IN NANOCRYSTALLINE SILICON FILMS AT LOW TEMPERATURE

Abstract

In a wide temperature range (500—20 K), we studied the electrical transport mechanism in intrinsic and P-doped nanocrystalline silicon films. We find that the HQD model successfully explains the conductivity at high temperatures (500—200K ), but fails at temperature below 200K. Single activation energy W was found in the low temperature range (100—20K), which is approximately equal to the value of kBT(W～1—3kBT).It is in good agreement with the charac teristics of hopping conduction in amorphous semiconductor, In this paper we mod ified the HQD model. We consider two distinct transport mechanisms, thermal-assi sted tunneling and electrons hopping through the local states near the Fermi lev el exist simultaneously. At high temperature tunneling transport is the main pro cess. At low temperature transport is governed by electron hopping. On this basi s, a complete analytic function of the conductivity is proposed. The function su ccessfully explains the conductivity of intrinsic and P-doped nanocrystalline si licon films in the whole temperature range.