Damage Evolution and Recovery in Al-Implanted 4H-SiC

Abstract

Damage evolution in 4H-SiC epitaxial layers irradiated with 1.1 MeV Al molecular ions at 150 K to a range of ion fluences and subsequent isochronal recovery were studied by Rutherford backscattering spectroscopy (RBS) and nuclear reaction analysis (NRA). The relative disorder on both the Si and C sublattices follows a sigmoidal dependence on ion fluence, and a buried amorphous layer is formed when the local dose reaches a critical amorphization value (0.12 dpa). The buried amorphous thickness increases rapidly at {approx} 2.0 x 1014 Al/cm2 and eventually saturates at the highest fluence. Isochronal annealing studies up to 870 K reveals the existence of three distinct recovery stages at {approx} 335, 520 and 650 K for low to intermediate ion fluences, where the relative disorder has not yet reached the fully amorphous level. In high-dose samples, where a buried amorphous layer is produced, the onset of a fourth recovery stage appears above 800 K. Recrystallization occurs at the rear interface and in the surface region, and the relative amount of recovery decreases with increasing fluence for the same annealing temperatures. Defect-stimulated epitaxial growth rather than thermal-stimulated epitaxial growth dominates the recrystallization.