First-principles study on improvement of two-dimensional hole gas concentration and confinement in AlN/GaN superlattices

Abstract

Using first-principles calculations based on density functional theory, we have systematically studied the influence of in-plane lattice constant and thickness of slabs on the concentration and distribution of two-dimensional hole gas (2DHG) in AlN/GaN superlattices. We show that the increase of in-plane lattice constant would increase the concentration of 2DHG at interfaces and decrease the valence band offset, which may lead to a leak of current. Increasing the thickness of AlN and/or decreasing the thickness of GaN would remarkably strengthen the internal field in GaN layer, resulting in better confinement of 2DHG at AlN/GaN interfaces. Therefore, a moderate larger in-plane lattice constant and thicker AlN layer could improve the concentration and confinement of 2DHG at AlN/GaN interfaces. Our study could serve as a guide to control the properties of 2DHG at III-nitride interfaces and help to optimize the performance of p-type nitride-based devices.

Depth profiled polarization effects in AlGaN quantum wells probed with interconnected cathodoluminescence spectroscopy and ion sputtering

“…roup-III nitrides such as GaN and AlN have very prominent spontaneous polarization (SP) phenomena arising from their underlying wurtzite structure. [1][2][3] Biaxial strains in group-III nitrides, especially being substantial in epitaxially grown heterostructures, result in piezoelectric polarization (PE). Both SP and PE polarizations can induce polarization charges at the surfaces and interfaces of heterostructured group-III nitrides, 4,5) which generate strong electric fields inside layered semiconductors and lead to the quantum confined Stark effect (QCSE).…”