Influence of the AlN nucleation layer on the properties of AlGaN/GaN heterostructure on Si (1 1 1) substrates

Highlights: • AlGaN/GaN HEMT structures have been grown on Si (1 1 1) substrates with different AlN nucleation layers (NL) by MOCVD. • Effects of the growth temperature of AlN NL on properties of the AlGaN/GaN heterostructures are investigated. • Optimized growth temperature of AlN NL resulted in superior two-dimensional electron gas performance of the AlGaN/GaN heterostructure. AlGaN/GaN heterostructures were grown on Si (1 1 1) substrates with different AlN nucleation layers (NL) by metal–organic chemical vapor deposition (MOCVD). The results indicate that the growth temperature of AlN NL has a noticeable influence on the structural, electronic and optical properties of the AlGaN/GaN heterostructures. Optimizing the growth temperature to 1040 °C led to quasi-2D smooth surface of the AlN NL with providing sufficient compressive stress to suppress cracking of the subsequent GaN layer during the cooling process, resulting in improved crystalline quality of GaN layer and superior two-dimensional electron gas (2DEG) performance of the AlGaN/GaN heterostructure.