Highly Homogeneous Current Transport in Ultra-Thin Aluminum Nitride (AlN) Epitaxial Films on Gallium Nitride (GaN) Deposited by Plasma Enhanced Atomic Layer Deposition

Nanomaterials

Giuseppe Greco¹  Patrick Fiorenza¹  Raffaella Lo Nigro¹  Filippo Giannazzo¹  Salvatore Di Franco¹  Emanuela Schilirò¹  Fabrizio Roccaforte¹  Zsolt Fogarassy²  Béla Pécz²  Ildiko Cora²  Mike Leszczynski³  Paweł Prystawko³  Piotr Kruszewski³ 

[1] CNR-IMM, Strada VIII, 5, 95121 Catania, Italy;Centre for Energy Research, Institute for Technical Physics and Materials Science Research, Konkoly-Thege, 29-33, 1121 Budapest, Hungary;Top-GaN Ltd., Sokolowska 29/37, 01-142 Warsaw, Poland;

关键词: AlN;    GaN;    atomic layer deposition;   

DOI  :  10.3390/nano11123316

来源: DOAJ

【 摘 要 】

This paper reports an investigation of the structural, chemical and electrical properties of ultra-thin (5 nm) aluminum nitride (AlN) films grown by plasma enhanced atomic layer deposition (PE-ALD) on gallium nitride (GaN). A uniform and conformal coverage of the GaN substrate was demonstrated by morphological analyses of as-deposited AlN films. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) analyses showed a sharp epitaxial interface with GaN for the first AlN atomic layers, while a deviation from the perfect wurtzite stacking and oxygen contamination were detected in the upper part of the film. This epitaxial interface resulted in the formation of a two-dimensional electron gas (2DEG) with a sheet charge density n_s ≈ 1.45 × 10¹² cm⁻², revealed by Hg-probe capacitance–voltage (C–V) analyses. Nanoscale resolution current mapping and current–voltage (I–V) measurements by conductive atomic force microscopy (C-AFM) showed a highly homogeneous current transport through the 5 nm AlN barrier, while a uniform flat-band voltage (V_FB ≈ 0.3 V) for the AlN/GaN heterostructure was demonstrated by scanning capacitance microscopy (SCM). Electron transport through the AlN film was shown to follow the Fowler–Nordheim (FN) tunneling mechanism with an average barrier height of <Φ_B> = 2.08 eV, in good agreement with the expected AlN/GaN conduction band offset.

【 授权许可】

Unknown