Quantum coherence of electrons in random networks of c-axis oriented wedge-shaped GaN nanowalls grown by molecular beam epitaxy

TL;DR

This study investigates quantum coherence and transport properties of electrons in c-axis oriented GaN nanowall networks, revealing high electron mobility and phase coherence lengths that surpass those in traditional 2DEG systems.

Contribution

It provides new insights into electron coherence and mobility in GaN nanowalls, demonstrating substantial mobility enhancement and exceptionally large phase coherence lengths compared to existing systems.

Findings

Weak localization observed in all samples

Electron mobility comparable to previous estimates

Phase coherence length up to 60 microns in narrow walls

Abstract

The depth distribution of the transport properties as well as the temperature dependence of the low field magneto-conductance for several c-axis oriented GaN nanowall network samples grown with different average wall-widths are investigated. Magneto-conductance recorded at low temperatures shows clear signature of weak localization effect in all nanowall samples studied here. The scattering mean free path and the phase coherence time, are extracted from the magneto-conductance profile. Electron mobility estimated from scattering mean free path is found to be comparable with those estimated previously from room temperature conductivity data for these samples [Appl. Phys. Lett. 101, 132109 (2012); AIP Conf. Proc. 1583, 252 (2014)], confirming independently the substantial mobility enhancement in these nanowalls as compared to bulk. Our study furthermore reveals that the high electron mobility region extends down to several hundreds of nanometer below the tip of the walls. Like mobility, phase coherence length is found to increase with the reduction of the average wall width. Interestingly, for samples with lower values of the average wall width, phase coherence length is estimated to be as high as 60 micron, which is much larger than those reported for GaN/AlGaN heterostructure based two dimensional electron gas (2DEG) systems.