Electrical Properties of Atomic Layer Deposited Aluminum Oxide on Gallium Nitride

TL;DR

This study investigates the electrical properties of Al2O3 films on GaN, revealing key interface characteristics such as conduction band offset and fixed charge density, important for electronic device applications.

Contribution

It provides experimental measurements of the conduction band offset and interface charge density at the Al2O3/GaN interface, supporting theoretical predictions and advancing understanding of this material system.

Findings

Conduction band offset at Al2O3/GaN interface is 2.13 eV.

Fixed positive charge density at the interface is 4.60x10^{12} cm^{-2}.

A non-zero oxide field of 0.93 MV/cm was observed.

Abstract

We report on our investigation of the electrical properties of metal/Al2O3/GaN metal-insulator-semiconductor (MIS) capacitors. We determined the conduction band offset and interface charge density of the alumina/GaN interface by analyzing capacitance-voltage characteristics of atomic layer deposited Al2O3 films on GaN substrates. The conduction band offset at the Al2O3/GaN interface was calculated to be 2.13 eV, in agreement with theoretical predications. A non-zero field of 0.93 MV/cm in the oxide under flat-band conditions in the GaN was inferred, which we attribute to a fixed net positive charge density of magnitude 4.60x1012 cm-2 at the Al2O3/GaN interface. We provide hypotheses to explain the origin of this charge by analyzing the energy band line-up.