Two dimensional confinement of electrons in nanowall network of GaN leading to high mobility and phase coherence

TL;DR

This paper demonstrates a novel method to create a two-dimensional electron gas in GaN nanowalls through charge accumulation on side facets, resulting in high electron mobility and phase coherence, with potential applications in spintronics.

Contribution

It introduces an alternative approach to achieve 2DEG in GaN nanowalls via surface charge effects, supported by self-consistent quantum-mechanical modeling and experimental validation.

Findings

Enhanced electron mobility compared to bulk GaN

Observation of weak localization indicating 2D confinement

Phase coherence length up to 20 μm

Abstract

Here, we report an alternative route to achieve two dimensional electron gas (2DEG) in a semiconductor structure. It has been shown that charge accumulation on the side facets can lead to the formation of 2DEG in a network of c-axis oriented wedge-shaped GaN nanowalls grown on c-plane sapphire substrate. Our study reveals that negative charges on the side-facets pushes the electron cloud inward resulting in the formation of 2DEG in the central plane parallel to the wall height. This confinement is evidenced from several orders of magnitude enhancement of electron mobility as compared to bulk, observation of weak localization effect in low temperature magneto-transport studies as well as the reduction of both the elastic and inelastic scattering rates with the average width of the walls. Importantly, the phase coherence length has been found to be as high as 20 {\mu}m, which makes the system potentially interesting for spin-tronics. Schrodinger and the Poisson equations are solved self-consistently taking into account the surface charge accumulation effect. The result indeed shows the 2D quantum confinement of electrons even for 40 nm of wall-width.