Current path in light emitting diodes based on nanowire ensembles

TL;DR

This paper investigates the electrical and optical behavior of nanowire ensemble LEDs, revealing that their electroluminescence is influenced by current inhomogeneity and quantum effects within the nanowires.

Contribution

It provides a detailed analysis of the current distribution and quantum effects in (In,Ga)N/GaN nanowire ensemble LEDs, highlighting the role of inhomogeneity in their electroluminescence.

Findings

Electroluminescence governed by current density differences among nanowires.

Nanowires exhibit N-polarity and quantum confined Stark effect.

Inhomogeneity affects the overall LED performance.

Abstract

Light emitting diodes (LEDs) were fabricated using ensembles of free-standing (In,Ga)N/GaN nanowires (NWs) grown on Si substrates in the self-induced growth mode by molecular beam epitaxy. Electron beam induced current analysis, cathodoluminescence as well as biased $\mu$-photoluminescence spectroscopy, transmission electron microscopy, and electrical measurements indicate that the electroluminescence of such LEDs is governed by the differences in the individual current densities of the single-NW LEDs operated in parallel, i.e. by the inhomogeneity of the current path in the ensemble LED. In addition, the optoelectronic characterization leads to the conclusion that these NWs exhibit N-polarity and that the (In,Ga)N quantum well states in the NWs are subject to a non-vanishing quantum confined Stark effect.