Structural Characterization of MOVPE Grown AlGaN/GaN for HEMT Formation

Vladimir Popok, Thore Stig Aunsborg, Rasmus Hjelmgart Godiksen, Peter Kjær Kristensen, Raghavendra Rao Juluri, Piotr Caban, Kjeld Pedersen

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Abstract

Results on structural, compositional, optical and electrical characterization of MOVPE grown AlGaN/GaN heterostructures with focus on understanding how the AlN buffer synthesis affects the top films are reported. The study demonstrates very good correlation between different methods providing a platform for reliable estimation of crystalline quality of the AlGaN/GaN structures and related to that electrical performance which is found to be significantly affected by threading dislocations (TD): higher TD density reduces the electron mobility while the charge carrier concentration is found to be largely unchanged. The attempt to vary the ammonia flow during the AlN synthesis is found not to affect the film composition and dislocation densities in the following heterostructures. An unusual phenomenon of considerable diffusion of Ga from the GaN film into the AlN buffer is found in all samples under the study. The obtained results are an important step in optimization of AlGaN/GaN growth towards the formation of good quality HEMT structures on sapphire and transfer of technology to Si substrates by providing clear understanding of the role of synthesis parameter on structure and composition of the films.
Original languageEnglish
JournalReviews on Advanced Materials Science
Volume57
Issue number1
Pages (from-to)72-81
Number of pages10
ISSN1605-8127
Publication statusPublished - Dec 2018

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