Effect of fully strained AlN nucleation layer on the AlN/SiC interface and subsequent GaN growth on 4H–SiC by MOVPE

AlN nucleation layers (NL) with different thickness were grown on 4H-SiC substrates using MOVPE. The growth evolution of the AlN layer on SiC was investigated. The effect of fully strained AlN nucleation layer (NL) on the AlN/SiC interface and on the subsequent GaN growth was also investigated. The thickness of the NL was varied between 10 nm and 100 nm in order to study the surface morphology and strain of AlN NL layer. The interface quality between AlN and SiC was characterized using HRXRD. It was observed that 100 nm NL was partially relaxed whereas 40 nm AlN NL was fully strained with improved SiC/AlN interface. GaN layer grown with fully strained NL showed improved surface morphology and lower screw dislocation density. 2DEG properties of AlGaN/GaN HEMT structures grown on fully strained and partially relaxed NL were found to be almost similar.