arXiv subjects

Stefano Leone

Publications and source records attributed to Stefano Leone.

3 recordsLinked to original sources

arXiv2026

Shubnikov-de Haas oscillations of two-dimensional electron gases in AlYN/GaN and AlScN/GaN heterostructures

AlYN and AlScN have recently emerged as promising nitride materials that can be integrated with GaN to form two-dimensional electron gases (2DEGs) at heterojunctions. Electron transport properties in these heterostructures have been enhanced through careful design and optimization of epitaxial growth conditions. In this work, we report for the first time Shubnikov-de Haas (SdH) oscillations of 2DEGs in AlYN/GaN and AlScN/GaN heterostructures, grown by metal-organic chemical vapor deposition. SdH oscillations provide direct access to key 2DEG parameters at the Fermi level: (1) carrier density, (2) electron effective mass (m* ~ 0.24 me for AlYN/GaN and m* ~ 0.25 me for AlScN/GaN), and (3) quantum scattering time (~ 68 fs for AlYN/GaN and ~ 70 fs for AlScN/GaN). These measurements of fundamental transport properties provide critical insights for advancing emerging nitride semiconductors for future high-frequency and power electronics.

cond-mat.mes-hall↗

arXiv2025

Chemical Vapor Deposition of Nitrides by Carbon-free Brominated Precursors

The epitaxial growth of group 13-nitride semiconductors (GaN, AlN, and AlGaN alloys) for the mass production and fabrication of high-frequency and high-power devices relies on metal-organic chemical vapor deposition (MOCVD) using metal-organic molecules, also called precursors. While this growth method ensures high productivity and low operation costs compared to other methods, its most significant disadvantage lies in the presence of carbon atoms in the precursors, which are unavoidably incorporated into the epitaxial layers and hamper the performance of most types of fabricated devices. Carbon-free precursors for the CVD process could enhance the performance of high-frequency and high-power nitride-based devices while maintaining growth capability in industrial equipment. In this work, we implement gallium- and aluminum-brominated precursors, which contain no carbon atoms, to grow GaN and AlN layers in an industrial CVD system. We compare the results of this alternative CVD process with the conventional method using trimethyl precursors through several characterization techniques, indicating a clear reduction in optically active carbon-related defects.

cond-mat.mtrl-sci↗

arXiv2023

Demonstration and STEM Analysis of Ferroelectric Switching in MOCVD-Grown Single Crystalline Al$_{0.85}$Sc$_{0.15}$N

Wurtzite-type Al$_{1-x}$Sc$_x$N solid solutions grown by metal organic chemical vapour deposition are for the first time confirmed to be ferroelectric. The film with 230 nm thickness and x = 0.15 exhibits a coercive field of 5.5 MV/cm at a measurement frequency of 1.5 kHz. Single crystal quality and homogeneous chemical composition of the film was confirmed by X-ray diffraction spectroscopic methods such as time of flight secondary ion mass spectrometry. Annular bright field scanning transmission electron microscopy served to proof the ferroelectric polarization inversion on unit cell level. The single crystal quality further allowed to image the large-scale domain pattern of a wurtzite-type ferroelectric for the first time, revealing a predominantly cone-like domain shape along the c-axis of the material. As in previous work, this again implies the presence of strong polarization discontinuities along this crystallographic axis, which could be suitable for current transport. The domains are separated by narrow domain walls, for which an upper thickness limit of 3 nm was deduced, but which could potentially be atomically sharp. We are confident that these results will advance the commencing integration of wurtzite-type ferroelectrics to GaN as well as generally III-N based heterostructures and devices.

physics.app-ph↗