Investigation of density of states and charge carrier mobility in amorphous semiconductors via time-of-flight photocurrent analysis

TL;DR

This study combines experimental TOF measurements and numerical simulations to analyze the density of states and charge carrier mobility in amorphous selenium, revealing trap states and transport mechanisms across temperature and field variations.

Contribution

It introduces a comprehensive method using Laplace transform analysis and the multiple trapping model to accurately reconstruct the DOS and evaluate mobility in amorphous semiconductors.

Findings

Identification of shallow and deep trap levels in a-Se.

Thermally activated hole mobility with specific activation energies.

Validation of Laplace-based techniques for disordered semiconductors.

Abstract

The present study examines the electronic transport characteristics of amorphous semiconductors through TOF measurements and numerical simulations. The primary objective is to determine the DOS in amorphous selenium (a-Se) and to assess the temperature and electric field dependence of the hole mobility. A comprehensive investigation of localized states within the mobility gap is performed using Laplace transform analysis of ToF photocurrent transients, combined with the multiple trapping model. This approach enables accurate reconstruction of the DOS across a wide temperature range, allowing clear identification of shallow and deep trap levels and revealing thermally activated transport mechanisms. Simulated ToF currents are also used to evaluate the hole drift mobility under various thermal and field conditions. Activation energies are extracted from Arrhenius plots of the mobility data. The results support a physically consistent description of the electronic structure in a-Se and validate the applicability of Laplace-based techniques for probing charge transport in disordered semiconductors.