Dependence of conduction mechanisms in heavily Al-doped 4H-SiC epilayers on Al concentration

Abstract

To reduce the resistivity of heavily Al-doped 4H-SiC epilayers, the conduction mechanisms were investigated for Al concentrations (CAl) between 2.4 × 1019 and 4.7 × 1020 cm−3 and measurement temperatures (T) between 20 and 600 K. The results elucidated the relationship between the conduction mechanisms and the values of T and CAl. For the epilayers with CAl ∼ 3 × 1019 cm−3, an unexpected additional conduction mechanism was observed between the band and nearest-neighbor-hopping conduction regions, for which two plausible conduction models are proposed. To reduce the resistivity of epilayers with CAl > 2 × 1020 cm−3, it is essential to fabricate samples with low lattice distortion.