Unipolar Vertical Transport in GaN/AlGaN/GaN Heterostructures

TL;DR

This paper investigates unipolar vertical transport in GaN/AlGaN/GaN heterostructures, revealing percolation-based mechanisms and methods to control leakage, which are crucial for improving III-nitride device performance.

Contribution

It identifies percolation due to alloy fluctuations as the main transport mechanism and demonstrates how to suppress it for better device control.

Findings

Vertical current is independent of dislocation density and barrier height.

Percolation transport is dominant in random alloy barriers.

Digital alloys and polarization-engineered barriers reduce leakage.

Abstract

In this letter, we report on unipolar vertical transport characteristics in c-plane GaN/AlGaN/GaN heterostructures. Vertical current in heterostructures with random alloy barriers was found to be independent of dislocation density and heterostructure barrier height, and significantly higher than theoretical estimates. Percolation-based transport due to random alloy fluctuations in the ternary AlGaN is suggested as the dominant transport mechanism, and confirmed through experiments showing that non-random or digital AlGaN alloys and polarization-engineered binary GaN barriers can eliminate percolation transport and reduce leakage significantly. The understanding of vertical transport and methods for effective control proposed here will greatly impact III-nitride unipolar vertical devices.