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Improvement of crystal quality of AlN grown on sapphire substrate by MOCVD
Author(s) -
Lai MuJen,
Chang LiannBe,
Yuan TzuTao,
Lin RayMing
Publication year - 2010
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.201000063
Subject(s) - sapphire , materials science , metalorganic vapour phase epitaxy , nitride , substrate (aquarium) , surface roughness , diffraction , absorption edge , crystal (programming language) , aluminium , surface finish , volumetric flow rate , optoelectronics , analytical chemistry (journal) , layer (electronics) , optics , chemistry , laser , epitaxy , nanotechnology , composite material , band gap , chromatography , geology , computer science , programming language , oceanography , physics , quantum mechanics
The crystalline quality of aluminum nitride (AlN) epilayers grown on sapphire substrates by MOCVD was improved by increasing hydrogen flow rate during the high temperature growth process. The AlN epilayer exhibited a root mean square (rms) of roughness was 1.944 nm from the 2×2 µm 2 size atomic force microscopy (AFM) images. Full widths at half maximum (FWHMs) of (002) and (102) rocking curves of triple‐axis high resolution X‐ray diffraction (HRXRD) measurements were as narrow as 28.8 arc sec and 868 arc sec, respectively. The optical transmittance spectra showed a sharp absorption edge at a wavelength of 200 nm and strong Fabry‐Perot (FP) oscillations. It is proposed that the improvement in crystalline quality is due to the surface in the low‐temperature aluminum nitride (LT‐AlN) buffer layer is promoted to be stable Al‐polarity by the conditions of increasing hydrogen flow rate and ramping up the growth temperature. Addtionally, the parasitic reactions are effectively suppressed by increasing the hydrogen flow rate during the growth process of high temperature. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)