Study on the effects of AlN interlayer in thick GaN grown on 3C-SiC/Si substrates

For epitaxy of GaN on 3C-SiC/Si substrates, optimization of growth temperature of AlN interlayers (ILs) was performed. With a proper growth condition of AlN IL, crack-free 3.5 μm thick GaN layer was realized by multiple AlN ILs on 3C-SiC/Si (1 1 1) substrate. The distribution of D0X peak position in low temperature cathodoluminescence spectra was mapped to investigate the stress in as-grown wafer. An increase of tensile stress was found in the top GaN layers above AlN ILs. Cross-sectional transmission electron microscopy images confirmed that AlN ILs could induce compressive stress and reduce threading dislocations in the GaN epilayer grown on 3C-SiC/Si. The reduction of dislocations should account for the part of incremental tensile stress revealed by the inhomogeneous distribution of luminescence.

► AlN interlayer growth temperature in GaN on 3C-SiC/Si was optimized as 1050 °C.
► Crack free GaN layer was realized by multiple AlN interlayers on 3C-SiC/Si.
► Stress distribution was mapped by low temperature cathodoluminescence in GaN.
► TEM revealed threading dislocations transformed to misfit dislocations.
► The misfit dislocations relaxed the compressive stress induced by AlN.