Computational study of ridge states in GaAs nanopillars

Abstract

Semiconductor nanopillars have unique geometries that make them very promising materials for a variety of devices. In order to improve their performance, we need to understand how they are affected by ridge states that lie on the six corners of the nanopillar hexagon. Although the GaAs nanopillars are primarily zinc blende (ABC), stacking faults of wurtzite (AB) stacking occur. We use density-functional theory to study stacking faults using one-dimensional periodic geometries that have a combination of zinc blende and wurtzite stacking. In contrast to perfect zinc blende nanopillars, energetically favorable midgap ridge states created by stacking faults are found in these geometries using density-functional theory. The calculated band diagrams and densities of state help us to understand how these midgap states lead to a reduced mobility and carrier localization. We also study how sulfur passivation affects and potentially improves the performance by modifying the ridges.