Defect reduction in GaN epilayers and HFET structures grown on (0 0 0 1)sapphire by ammonia MBE

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Proceedings titleJournal of Crystal Growth
ConferenceProceedings of the Fourth European Workshop on Gallium Nitride, July 2000, Nottingham, UK
Pages584589; # of pages: 6
SubjectCharacterization; Crystal morphology; Molecular beam epitaxy; Nitrides; Semiconducting III–V materials; High electron mobility transistor
AbstractThe quality of GaN epilayers grown by molecular beam epitaxy on substrates such as sapphire and silicon carbide has improved considerably over the past few years and in fact now produces AlGaN/GaN HEMT devices with characteristics among the best reported for any growth technique. However, only recently has the bulk defect density of MBE grown GaN achieved levels comparable to that obtained by MOVPE and with a comparable level of electrical performance. In this paper, we report the ammonia-MBE growth of GaN epilayers and HFET structures on (0 0 0 1)sapphire. The effect of growth temperature on the defect density of single GaN layers and the effect of an insulating carbon doped layer on the defect density of an overgrown channel layer in the HFET structures is reported. The quality of the epilayers has been studied using Hall effect and the defect density using TEM, SEM and wet etching. The growth of an insulating carbon-doped buffer layer followed by an undoped GaN channel layer results in a defect density in the channel layer of ∼2×108 cm−2. Mobilities close to 490 cm2/Vs at a carrier density of 8×1016 cm−3 for a 0.4 μm thick channel layer has been observed. Growth temperature is one of the most critical parameters for achieving this low defect density both in the bulk layers and the FET structures. Photo-chemical wet etching has been used to reveal the defect structure in these layers.
Publication date
AffiliationNational Research Council Canada; NRC Institute for Microstructural Sciences
Peer reviewedNo
NPARC number12328306
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Record identifier2707f7f9-46a2-44a8-9e58-6abbd8c24109
Record created2009-09-10
Record modified2016-05-09
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