Electrical transport mechanisms and structure of hydrogenated and non-hydrogenated nanocrystalline Ga1-xMnxAs films

Abstract

The mechanisms of electrical conductivity in hydrogenated and non-hydrogenated nanocrystalline Ga1-xMnxAs (0.000 <= x <= 0.081) films were analyzed, first from a macroscopic perspective, followed by microscopic analysis to investigate the energy levels for trapping electric charges. The analysis of the current-voltage and resistivity-temperature characteristics allowed the development of a model based on the morphology and structure of the films. This model takes into account the main aspects of the transport above 300 K. Space charge limited current (SCLC) mechanism was observed in Mn-free films and is associated with deep trap states located at 0.10 and 0.22 eV below the conduction band. In samples containing Mn, the dark conductivity is highly dependent on the presence of hydrogen. This effect was related to the grain boundaries and interstitial regions of the films, in which the density of gap states is expected to be reduced by the presence of hydrogen. (C) 2015 Elsevier B.V. All rights reserved.