Investigation of AlN nucleation layers for AlGaN/GaN heterostructures on 4H-SiC

Growth of GaN on AlN nucleation layers (NL) by LP-MOVPE on 4H-SiC substrates is investigated in order to obtain high quality GaN layers for AlGaN/GaN HEMTs. The relationship between structural quality, surface morphology and electrical properties has been investigated using HR-XRD, AFM, TEM, Van der Pauw-Hall and TLM measurements. It is shown that there is a correlation between AlN NL strain and HEMT 2DEG properties. Optimum layers show a Hall sheet resistance of 250 Ω/sq. Finally, HEMT transistors have been processed and measured, showing a saturated drain current of 1.2 A/mm for a gate length of 1.5 μm. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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