Polarization and Space Charge Limited Current in III-Nitride Heterostructure Nanowires

TL;DR

This paper investigates polarization effects and space charge limited conduction in III-Nitride nanowires, revealing how polarization fields influence p-type conductivity and charge distribution in complex heterostructure geometries.

Contribution

It provides a detailed numerical analysis of polarization-induced charge behavior and conduction regimes in III-Nitride nanowires, highlighting the impact of structural asymmetry and interface interactions.

Findings

P-type conductivity arises from hole carriers due to polarization fields.

Transition from Ohmic to space charge limited conduction occurs at low voltages.

Charge distribution is highly dependent on nanowire structure and polarization interactions.

Abstract

An undoped AlGaN/GaN nanowire demonstrated p-type conductivity based solely on the formation of hole carriers in response to the negative polarization field at the (000-1) AlGaN/GaN facet. A transistor based on this nanowire displayed a low-voltage transition from Ohmic to space charge limited conduction. A numerical simulation showed that a highly asymmetric strain exists across the triangular cross-section, which creates a doublet peak in the piezoelectric induced polarization sheet charge at the (000-1) facet. Additionally, there is a strong interplay between the charge at the (000-1) AlGaN/GaN interface with depletion from the three surfaces as well as an interaction with the opposing polarization fields at two semi-polar {-110-1} facets. The charge distribution and resultant conduction regime is highly interdependent on configuration of the multi-layer structure, and is not amenable to an analytical model.